@c -*-texinfo-*- @c This is part of the GNU Emacs Lisp Reference Manual. @c Copyright (C) 1990--1995, 1998--1999, 2001--2022 Free Software @c Foundation, Inc. @c See the file elisp.texi for copying conditions. @node Frames @chapter Frames @cindex frame A @dfn{frame} is a screen object that contains one or more Emacs windows (@pxref{Windows}). It is the kind of object called a ``window'' in the terminology of graphical environments; but we can't call it a ``window'' here, because Emacs uses that word in a different way. In Emacs Lisp, a @dfn{frame object} is a Lisp object that represents a frame on the screen. @xref{Frame Type}. A frame initially contains a single main window and/or a minibuffer window; you can subdivide the main window vertically or horizontally into smaller windows. @xref{Splitting Windows}. @cindex terminal A @dfn{terminal} is a display device capable of displaying one or more Emacs frames. In Emacs Lisp, a @dfn{terminal object} is a Lisp object that represents a terminal. @xref{Terminal Type}. @cindex text terminal @cindex graphical terminal @cindex graphical display There are two classes of terminals: @dfn{text terminals} and @dfn{graphical terminals}. Text terminals are non-graphics-capable displays, including @command{xterm} and other terminal emulators. On a text terminal, each Emacs frame occupies the terminal's entire screen; although you can create additional frames and switch between them, the terminal only shows one frame at a time. Graphical terminals, on the other hand, are managed by graphical display systems such as the X Window System, which allow Emacs to show multiple frames simultaneously on the same display. On GNU and Unix systems, you can create additional frames on any available terminal, within a single Emacs session, regardless of whether Emacs was started on a text or graphical terminal. Emacs can display on both graphical and text terminals simultaneously. This comes in handy, for instance, when you connect to the same session from several remote locations. @xref{Multiple Terminals}. @defun framep object This predicate returns a non-@code{nil} value if @var{object} is a frame, and @code{nil} otherwise. For a frame, the value indicates which kind of display the frame uses: @table @code @item t The frame is displayed on a text terminal. @item x The frame is displayed on an X graphical terminal. @item w32 The frame is displayed on a MS-Windows graphical terminal. @item ns The frame is displayed on a GNUstep or Macintosh Cocoa graphical terminal. @item pc The frame is displayed on an MS-DOS terminal. @item pgtk The frame is displayed using pure GTK facilities. @end table @end defun @defun frame-terminal &optional frame This function returns the terminal object that displays @var{frame}. If @var{frame} is @code{nil} or unspecified, it defaults to the selected frame. @end defun @defun terminal-live-p object This predicate returns a non-@code{nil} value if @var{object} is a terminal that is live (i.e., not deleted), and @code{nil} otherwise. For live terminals, the return value indicates what kind of frames are displayed on that terminal; the list of possible values is the same as for @code{framep} above. @end defun @cindex top-level frame On a graphical terminal we distinguish two types of frames: A normal @dfn{top-level frame} is a frame whose window-system window is a child of the window-system's root window for that terminal. A child frame is a frame whose window-system window is the child of the window-system window of another Emacs frame. @xref{Child Frames}. @menu * Creating Frames:: Creating additional frames. * Multiple Terminals:: Displaying on several different devices. * Frame Geometry:: Geometric properties of frames. * Frame Parameters:: Controlling frame size, position, font, etc. * Terminal Parameters:: Parameters common for all frames on terminal. * Frame Titles:: Automatic updating of frame titles. * Deleting Frames:: Frames last until explicitly deleted. * Finding All Frames:: How to examine all existing frames. * Minibuffers and Frames:: How a frame finds the minibuffer to use. * Input Focus:: Specifying the selected frame. * Visibility of Frames:: Frames may be visible or invisible, or icons. * Raising and Lowering:: Raising, Lowering and Restacking Frames. * Frame Configurations:: Saving the state of all frames. * Child Frames:: Making a frame the child of another. * Mouse Tracking:: Getting events that say when the mouse moves. * Mouse Position:: Asking where the mouse is, or moving it. * Pop-Up Menus:: Displaying a menu for the user to select from. * Dialog Boxes:: Displaying a box to ask yes or no. * Pointer Shape:: Specifying the shape of the mouse pointer. * Window System Selections:: Transferring text to and from other X clients. * Yanking Media:: Yanking things that aren't plain text. * Drag and Drop:: Internals of Drag-and-Drop implementation. * Color Names:: Getting the definitions of color names. * Text Terminal Colors:: Defining colors for text terminals. * Resources:: Getting resource values from the server. * Display Feature Testing:: Determining the features of a terminal. @end menu @node Creating Frames @section Creating Frames @cindex frame creation To create a new frame, call the function @code{make-frame}. @deffn Command make-frame &optional parameters This function creates and returns a new frame, displaying the current buffer. The @var{parameters} argument is an alist that specifies frame parameters for the new frame. @xref{Frame Parameters}. If you specify the @code{terminal} parameter in @var{parameters}, the new frame is created on that terminal. Otherwise, if you specify the @code{window-system} frame parameter in @var{parameters}, that determines whether the frame should be displayed on a text terminal or a graphical terminal. @xref{Window Systems}. If neither is specified, the new frame is created in the same terminal as the selected frame. Any parameters not mentioned in @var{parameters} default to the values in the alist @code{default-frame-alist} (@pxref{Initial Parameters}); parameters not specified there default from the X resources or its equivalent on your operating system (@pxref{X Resources,, X Resources, emacs, The GNU Emacs Manual}). After the frame is created, this function applies any parameters specified in @code{frame-inherited-parameters} (see below) it has no assigned yet, taking the values from the frame that was selected when @code{make-frame} was called. Note that on multi-monitor displays (@pxref{Multiple Terminals}), the window manager might position the frame differently than specified by the positional parameters in @var{parameters} (@pxref{Position Parameters}). For example, some window managers have a policy of displaying the frame on the monitor that contains the largest part of the window (a.k.a.@: the @dfn{dominating} monitor). This function itself does not make the new frame the selected frame. @xref{Input Focus}. The previously selected frame remains selected. On graphical terminals, however, the window system may select the new frame for its own reasons. @end deffn @defvar before-make-frame-hook A normal hook run by @code{make-frame} before it creates the frame. @end defvar @defvar after-make-frame-functions An abnormal hook run by @code{make-frame} after it created the frame. Each function in @code{after-make-frame-functions} receives one argument, the frame just created. @end defvar Note that any functions added to these hooks by your initial file are usually not run for the initial frame, since Emacs reads the initial file only after creating that frame. However, if the initial frame is specified to use a separate minibuffer frame (@pxref{Minibuffers and Frames}), the functions will be run for both, the minibuffer-less and the minibuffer frame. Alternatively, you can add functions to these hooks in your ``early init file'' (@pxref{Init File}), in which case they will be in effect for the initial frame as well. @defvar frame-inherited-parameters This variable specifies the list of frame parameters that a newly created frame inherits from the currently selected frame. For each parameter (a symbol) that is an element in this list and has not been assigned earlier when processing @code{make-frame}, the function sets the value of that parameter in the created frame to its value in the selected frame. @end defvar @defopt server-after-make-frame-hook A normal hook run when the Emacs server creates a client frame. When this hook is called, the created frame is the selected one. @xref{Emacs Server,,, emacs, The GNU Emacs Manual}. @end defopt @node Multiple Terminals @section Multiple Terminals @cindex multiple terminals @cindex multi-tty @cindex multiple X displays @cindex displays, multiple Emacs represents each terminal as a @dfn{terminal object} data type (@pxref{Terminal Type}). On GNU and Unix systems, Emacs can use multiple terminals simultaneously in each session. On other systems, it can only use a single terminal. Each terminal object has the following attributes: @itemize @bullet @item The name of the device used by the terminal (e.g., @samp{:0.0} or @file{/dev/tty}). @item The terminal and keyboard coding systems used on the terminal. @xref{Terminal I/O Encoding}. @item The kind of display associated with the terminal. This is the symbol returned by the function @code{terminal-live-p} (i.e., @code{x}, @code{t}, @code{w32}, @code{ns}, @code{pc}, @code{haiku}, or @code{pgtk}). @xref{Frames}. @item A list of terminal parameters. @xref{Terminal Parameters}. @end itemize There is no primitive for creating terminal objects. Emacs creates them as needed, such as when you call @code{make-frame-on-display} (described below). @defun terminal-name &optional terminal This function returns the file name of the device used by @var{terminal}. If @var{terminal} is omitted or @code{nil}, it defaults to the selected frame's terminal. @var{terminal} can also be a frame, meaning that frame's terminal. @end defun @defun terminal-list This function returns a list of all live terminal objects. @end defun @defun get-device-terminal device This function returns a terminal whose device name is given by @var{device}. If @var{device} is a string, it can be either the file name of a terminal device, or the name of an X display of the form @samp{@var{host}:@var{server}.@var{screen}}. If @var{device} is a frame, this function returns that frame's terminal; @code{nil} means the selected frame. Finally, if @var{device} is a terminal object that represents a live terminal, that terminal is returned. The function signals an error if its argument is none of the above. @end defun @defun delete-terminal &optional terminal force This function deletes all frames on @var{terminal} and frees the resources used by it. It runs the abnormal hook @code{delete-terminal-functions}, passing @var{terminal} as the argument to each function. If @var{terminal} is omitted or @code{nil}, it defaults to the selected frame's terminal. @var{terminal} can also be a frame, meaning that frame's terminal. Normally, this function signals an error if you attempt to delete the sole active terminal, but if @var{force} is non-@code{nil}, you are allowed to do so. Emacs automatically calls this function when the last frame on a terminal is deleted (@pxref{Deleting Frames}). @end defun @defvar delete-terminal-functions An abnormal hook run by @code{delete-terminal}. Each function receives one argument, the @var{terminal} argument passed to @code{delete-terminal}. Due to technical details, the functions may be called either just before the terminal is deleted, or just afterwards. @end defvar @cindex terminal-local variables A few Lisp variables are @dfn{terminal-local}; that is, they have a separate binding for each terminal. The binding in effect at any time is the one for the terminal that the currently selected frame belongs to. These variables include @code{default-minibuffer-frame}, @code{defining-kbd-macro}, @code{last-kbd-macro}, and @code{system-key-alist}. They are always terminal-local, and can never be buffer-local (@pxref{Buffer-Local Variables}). On GNU and Unix systems, each X display is a separate graphical terminal. When Emacs is started from within the X window system, it uses the X display specified by the @env{DISPLAY} environment variable, or by the @samp{--display} option (@pxref{Initial Options,,, emacs, The GNU Emacs Manual}). Emacs can connect to other X displays via the command @code{make-frame-on-display}. Each X display has its own selected frame and its own minibuffer windows; however, only one of those frames is @emph{the} selected frame at any given moment (@pxref{Input Focus}). Emacs can even connect to other text terminals, by interacting with the @command{emacsclient} program. @xref{Emacs Server,,, emacs, The GNU Emacs Manual}. @cindex X display names @cindex display name on X A single X server can handle more than one display. Each X display has a three-part name, @samp{@var{hostname}:@var{displaynumber}.@var{screennumber}}. The first part, @var{hostname}, specifies the name of the machine to which the display is physically connected. The second part, @var{displaynumber}, is a zero-based number that identifies one or more monitors connected to that machine that share a common keyboard and pointing device (mouse, tablet, etc.). The third part, @var{screennumber}, identifies a zero-based screen number (a separate monitor) that is part of a single monitor collection on that X server. When you use two or more screens belonging to one server, Emacs knows by the similarity in their names that they share a single keyboard. Systems that don't use the X window system, such as MS-Windows, don't support the notion of X displays, and have only one display on each host. The display name on these systems doesn't follow the above 3-part format; for example, the display name on MS-Windows systems is a constant string @samp{w32}, and exists for compatibility, so that you could pass it to functions that expect a display name. @deffn Command make-frame-on-display display &optional parameters This function creates and returns a new frame on @var{display}, taking the other frame parameters from the alist @var{parameters}. @var{display} should be the name of an X display (a string). Before creating the frame, this function ensures that Emacs is set up to display graphics. For instance, if Emacs has not processed X resources (e.g., if it was started on a text terminal), it does so at this time. In all other respects, this function behaves like @code{make-frame} (@pxref{Creating Frames}). @end deffn @defun x-display-list This function returns a list that indicates which X displays Emacs has a connection to. The elements of the list are strings, and each one is a display name. @end defun @defun x-open-connection display &optional xrm-string must-succeed This function opens a connection to the X display @var{display}, without creating a frame on that display. Normally, Emacs Lisp programs need not call this function, as @code{make-frame-on-display} calls it automatically. The only reason for calling it is to check whether communication can be established with a given X display. The optional argument @var{xrm-string}, if not @code{nil}, is a string of resource names and values, in the same format used in the @file{.Xresources} file. @xref{X Resources,, X Resources, emacs, The GNU Emacs Manual}. These values apply to all Emacs frames created on this display, overriding the resource values recorded in the X server. Here's an example of what this string might look like: @example "*BorderWidth: 3\n*InternalBorder: 2\n" @end example If @var{must-succeed} is non-@code{nil}, failure to open the connection terminates Emacs. Otherwise, it is an ordinary Lisp error. @end defun @defun x-close-connection display This function closes the connection to display @var{display}. Before you can do this, you must first delete all the frames that were open on that display (@pxref{Deleting Frames}). @end defun @cindex multi-monitor On some multi-monitor setups, a single X display outputs to more than one physical monitor. You can use the functions @code{display-monitor-attributes-list} and @code{frame-monitor-attributes} to obtain information about such setups. @defun display-monitor-attributes-list &optional display This function returns a list of physical monitor attributes on @var{display}, which can be a display name (a string), a terminal, or a frame; if omitted or @code{nil}, it defaults to the selected frame's display. Each element of the list is an association list, representing the attributes of a physical monitor. The first element corresponds to the primary monitor. The attribute keys and values are: @table @samp @item geometry Position of the top-left corner of the monitor's screen and its size, in pixels, as @samp{(@var{x} @var{y} @var{width} @var{height})}. Note that, if the monitor is not the primary monitor, some of the coordinates might be negative. @item workarea Position of the top-left corner and size of the work area (usable space) in pixels as @samp{(@var{x} @var{y} @var{width} @var{height})}. This may be different from @samp{geometry} in that space occupied by various window manager features (docks, taskbars, etc.)@: may be excluded from the work area. Whether or not such features actually subtract from the work area depends on the platform and environment. Again, if the monitor is not the primary monitor, some of the coordinates might be negative. @item mm-size Width and height in millimeters as @samp{(@var{width} @var{height})} @item frames List of frames that this physical monitor dominates (see below). @item name Name of the physical monitor as @var{string}. @item source Source of the multi-monitor information as @var{string}; e.g., @samp{XRandr} or @samp{Xinerama}. @end table @var{x}, @var{y}, @var{width}, and @var{height} are integers. @samp{name} and @samp{source} may be absent. A frame is @dfn{dominated} by a physical monitor when either the largest area of the frame resides in that monitor, or (if the frame does not intersect any physical monitors) that monitor is the closest to the frame. Every (non-tooltip) frame (whether visible or not) in a graphical display is dominated by exactly one physical monitor at a time, though the frame can span multiple (or no) physical monitors. Here's an example of the data produced by this function on a 2-monitor display: @lisp (display-monitor-attributes-list) @result{} (((geometry 0 0 1920 1080) ;; @r{Left-hand, primary monitor} (workarea 0 0 1920 1050) ;; @r{A taskbar occupies some of the height} (mm-size 677 381) (name . "DISPLAY1") (frames # #)) ((geometry 1920 0 1680 1050) ;; @r{Right-hand monitor} (workarea 1920 0 1680 1050) ;; @r{Whole screen can be used} (mm-size 593 370) (name . "DISPLAY2") (frames))) @end lisp @end defun @defun frame-monitor-attributes &optional frame This function returns the attributes of the physical monitor dominating (see above) @var{frame}, which defaults to the selected frame. @end defun On multi-monitor displays it is possible to use the command @code{make-frame-on-monitor} to make frames on the specified monitor. @deffn Command make-frame-on-monitor monitor &optional display parameters This function creates and returns a new frame on @var{monitor} located on @var{display}, taking the other frame parameters from the alist @var{parameters}. @var{monitor} should be the name of the physical monitor, the same string as returned by the function @code{display-monitor-attributes-list} in the attribute @code{name}. @var{display} should be the name of an X display (a string). @end deffn @node Frame Geometry @section Frame Geometry @cindex frame geometry @cindex frame position @cindex position of frame @cindex frame size @cindex size of frame The geometry of a frame depends on the toolkit that was used to build this instance of Emacs and the terminal that displays the frame. This chapter describes these dependencies and some of the functions to deal with them. Note that the @var{frame} argument of all of these functions has to specify a live frame (@pxref{Deleting Frames}). If omitted or @code{nil}, it specifies the selected frame (@pxref{Input Focus}). @menu * Frame Layout:: Basic layout of frames. * Frame Font:: The default font of a frame and how to set it. * Frame Position:: The position of a frame on its display. * Frame Size:: Specifying and retrieving a frame's size. * Implied Frame Resizing:: Implied resizing of frames and how to prevent it. @end menu @node Frame Layout @subsection Frame Layout @cindex frame layout @cindex layout of frame A visible frame occupies a rectangular area on its terminal's display. This area may contain a number of nested rectangles, each serving a different purpose. The drawing below sketches the layout of a frame on a graphical terminal: @smallexample @group <------------ Outer Frame Width -----------> ____________________________________________ ^(0) ________ External/Outer Border _______ | | | |_____________ Title Bar ______________| | | | (1)_____________ Menu Bar ______________| | ^ | | (2)_____________ Tool Bar ______________| | ^ | | (3)_____________ Tab Bar _______________| | ^ | | | _________ Internal Border ________ | | ^ | | | | ^ | | | | | | | | | | | | | Outer | | | Inner | | | Native Frame | | | Frame | | | Frame Height | | | Height | | | Height | | | | | | | | | | | | |<--+--- Inner Frame Width ------->| | | | | | | | | | | | | | | | |___v______________________________| | | | | | |___________ Internal Border __________| | v v |___________ External/Outer Border __________| <-------- Native Frame Width --------> @end group @end smallexample In practice not all of the areas shown in the drawing will or may be present. The meaning of these areas is described below. @table @asis @item Outer Frame @cindex outer frame @cindex outer edges @cindex outer width @cindex outer height @cindex outer size The @dfn{outer frame} is a rectangle comprising all areas shown in the drawing. The edges of that rectangle are called the @dfn{outer edges} of the frame. Together, the @dfn{outer width} and @dfn{outer height} of the frame specify the @dfn{outer size} of that rectangle. Knowing the outer size of a frame is useful for fitting a frame into the working area of its display (@pxref{Multiple Terminals}) or for placing two frames adjacent to each other on the screen. Usually, the outer size of a frame is available only after the frame has been mapped (made visible, @pxref{Visibility of Frames}) at least once. For the initial frame or a frame that has not been created yet, the outer size can be only estimated or must be calculated from the window-system's or window manager's defaults. One workaround is to obtain the differences of the outer and native (see below) sizes of a mapped frame and use them for calculating the outer size of the new frame. @cindex outer position The position of the upper left corner of the outer frame (indicated by @samp{(0)} in the drawing above) is the @dfn{outer position} of the frame. The outer position of a graphical frame is also referred to as ``the position'' of the frame because it usually remains unchanged on its display whenever the frame is resized or its layout is changed. The outer position is specified by and can be set via the @code{left} and @code{top} frame parameters (@pxref{Position Parameters}). For a normal, top-level frame these parameters usually represent its absolute position (see below) with respect to its display's origin. For a child frame (@pxref{Child Frames}) these parameters represent its position relative to the native position (see below) of its parent frame. For frames on text terminals the values of these parameters are meaningless and always zero. @item External Border @cindex external border The @dfn{external border} is part of the decorations supplied by the window manager. It is typically used for resizing the frame with the mouse and is therefore not shown on ``fullboth'' and maximized frames (@pxref{Size Parameters}). Its width is determined by the window manager and cannot be changed by Emacs' functions. External borders don't exist on text terminal frames. For graphical frames, their display can be suppressed by setting the @code{override-redirect} or @code{undecorated} frame parameter (@pxref{Management Parameters}). @item Outer Border @cindex outer border The @dfn{outer border} is a separate border whose width can be specified with the @code{border-width} frame parameter (@pxref{Layout Parameters}). In practice, either the external or the outer border of a frame are displayed but never both at the same time. Usually, the outer border is shown only for special frames that are not (fully) controlled by the window manager like tooltip frames (@pxref{Tooltips}), child frames (@pxref{Child Frames}) and @code{undecorated} or @code{override-redirect} frames (@pxref{Management Parameters}). Outer borders are never shown on text terminal frames and on frames generated by GTK+ routines. On MS-Windows, the outer border is emulated with the help of a one pixel wide external border. Non-toolkit builds on X allow to change the color of the outer border by setting the @code{border-color} frame parameter (@pxref{Layout Parameters}). @item Title Bar @cindex title bar @cindex caption bar The @dfn{title bar}, a.k.a.@ @dfn{caption bar}, is also part of the window manager's decorations and typically displays the title of the frame (@pxref{Frame Titles}) as well as buttons for minimizing, maximizing and deleting the frame. It can be also used for dragging the frame with the mouse. The title bar is usually not displayed for fullboth (@pxref{Size Parameters}), tooltip (@pxref{Tooltips}) and child frames (@pxref{Child Frames}) and doesn't exist for terminal frames. Display of the title bar can be suppressed by setting the @code{override-redirect} or the @code{undecorated} frame parameters (@pxref{Management Parameters}). @item Menu Bar @cindex internal menu bar @cindex external menu bar The menu bar (@pxref{Menu Bar}) can be either internal (drawn by Emacs itself) or external (drawn by the toolkit). Most builds (GTK+, Lucid, Motif and MS-Windows) rely on an external menu bar. NS also uses an external menu bar which, however, is not part of the outer frame. Non-toolkit builds can provide an internal menu bar. On text terminal frames, the menu bar is part of the frame's root window (@pxref{Windows and Frames}). As a rule, menu bars are never shown on child frames (@pxref{Child Frames}). Display of the menu bar can be suppressed by setting the @code{menu-bar-lines} parameter (@pxref{Layout Parameters}) to zero. Whether the menu bar is wrapped or truncated whenever its width becomes too large to fit on its frame depends on the toolkit . Usually, only Motif and MS-Windows builds can wrap the menu bar. When they (un-)wrap the menu bar, they try to keep the outer height of the frame unchanged, so the native height of the frame (see below) will change instead. @item Tool Bar @cindex internal tool bar @cindex external tool bar Like the menu bar, the tool bar (@pxref{Tool Bar}) can be either internal (drawn by Emacs itself) or external (drawn by a toolkit). The GTK+ and NS builds have the tool bar drawn by the toolkit. The remaining builds use internal tool bars. With GTK+ the tool bar can be located on either side of the frame, immediately outside the internal border, see below. Tool bars are usually not shown for child frames (@pxref{Child Frames}). Display of the tool bar can be suppressed by setting the @code{tool-bar-lines} parameter (@pxref{Layout Parameters}) to zero. If the variable @code{auto-resize-tool-bars} is non-@code{nil}, Emacs wraps the internal tool bar when its width becomes too large for its frame. If and when Emacs (un-)wraps the internal tool bar, it by default keeps the outer height of the frame unchanged, so the native height of the frame (see below) will change instead. Emacs built with GTK+, on the other hand, never wraps the tool bar but may automatically increase the outer width of a frame in order to accommodate an overlong tool bar. @item Tab Bar @cindex tab bar The tab bar (@pxref{Tab Bars,,,emacs, The GNU Emacs Manual}) is always drawn by Emacs itself. The tab bar appears above the tool bar in Emacs built with an internal tool bar, and below the tool bar in builds with an external tool bar. Display of the tab bar can be suppressed by setting the @code{tab-bar-lines} parameter (@pxref{Layout Parameters}) to zero. @item Native Frame @cindex native frame @cindex native edges @cindex native width @cindex native height @cindex native size The @dfn{native frame} is a rectangle located entirely within the outer frame. It excludes the areas occupied by an external or outer border, the title bar and any external menu or tool bar. The edges of the native frame are called the @dfn{native edges} of the frame. Together, the @dfn{native width} and @dfn{native height} of a frame specify the @dfn{native size} of the frame. The native size of a frame is the size Emacs passes to the window-system or window manager when creating or resizing the frame from within Emacs. It is also the size Emacs receives from the window-system or window manager whenever these resize the frame's window-system window, for example, after maximizing the frame by clicking on the corresponding button in the title bar or when dragging its external border with the mouse. @cindex native position The position of the top left corner of the native frame specifies the @dfn{native position} of the frame. (1)--(3) in the drawing above indicate that position for the various builds: @itemize @w{} @item (1) non-toolkit and terminal frames @item (2) Lucid, Motif, MS-Windows, and Haiku frames @item (3) GTK+ and NS frames @end itemize Accordingly, the native height of a frame may include the height of the tool bar but not that of the menu bar (Lucid, Motif, MS-Windows) or those of the menu bar and the tool bar (non-toolkit and text terminal frames). The native position of a frame is the reference position for functions that set or return the current position of the mouse (@pxref{Mouse Position}) and for functions dealing with the position of windows like @code{window-edges}, @code{window-at} or @code{coordinates-in-window-p} (@pxref{Coordinates and Windows}). It also specifies the (0, 0) origin for locating and positioning child frames within this frame (@pxref{Child Frames}). Note also that the native position of a frame usually remains unaltered on its display when removing or adding the window manager decorations by changing the frame's @code{override-redirect} or @code{undecorated} parameter (@pxref{Management Parameters}). @item Internal Border The internal border is a border drawn by Emacs around the inner frame (see below). The specification of its appearance depends on whether or not the given frame is a child frame (@pxref{Child Frames}). For normal frames its width is specified by the @code{internal-border-width} frame parameter (@pxref{Layout Parameters}), and its color is specified by the background of the @code{internal-border} face. For child frames its width is specified by the @code{child-frame-border-width} frame parameter (but will use the @code{internal-border-width} parameter as fallback), and its color is specified by the background of the @code{child-frame-border} face. @item Inner Frame @cindex inner frame @cindex inner edges @cindex inner width @cindex inner height @cindex inner size @cindex display area The @dfn{inner frame} is the rectangle reserved for the frame's windows. It's enclosed by the internal border which, however, is not part of the inner frame. Its edges are called the @dfn{inner edges} of the frame. The @dfn{inner width} and @dfn{inner height} specify the @dfn{inner size} of the rectangle. The inner frame is sometimes also referred to as the @dfn{display area} of the frame. @cindex minibuffer-less frame @cindex minibuffer-only frame As a rule, the inner frame is subdivided into the frame's root window (@pxref{Windows and Frames}) and the frame's minibuffer window (@pxref{Minibuffer Windows}). There are two notable exceptions to this rule: A @dfn{minibuffer-less frame} contains a root window only and does not contain a minibuffer window. A @dfn{minibuffer-only frame} contains only a minibuffer window which also serves as that frame's root window. See @ref{Initial Parameters} for how to create such frame configurations. @item Text Area @cindex text area The @dfn{text area} of a frame is a somewhat fictitious area that can be embedded in the native frame. Its position is unspecified. Its width can be obtained by removing from that of the native width the widths of the internal border, one vertical scroll bar, and one left and one right fringe if they are specified for this frame, see @ref{Layout Parameters}. Its height can be obtained by removing from that of the native height the widths of the internal border and the heights of the frame's internal menu and tool bars, the tab bar and one horizontal scroll bar if specified for this frame. @end table @cindex absolute position @cindex absolute frame position @cindex absolute edges @cindex absolute frame edges @cindex display origin @cindex origin of display The @dfn{absolute position} of a frame is given as a pair (X, Y) of horizontal and vertical pixel offsets relative to an origin (0, 0) of the frame's display. Correspondingly, the @dfn{absolute edges} of a frame are given as pixel offsets from that origin. Note that with multiple monitors, the origin of the display does not necessarily coincide with the top-left corner of the entire usable display area of the terminal. Hence the absolute position of a frame can be negative in such an environment even when that frame is completely visible. By convention, vertical offsets increase ``downwards''. This means that the height of a frame is obtained by subtracting the offset of its top edge from that of its bottom edge. Horizontal offsets increase ``rightwards'', as expected, so a frame's width is calculated by subtracting the offset of its left edge from that of its right edge. For a frame on a graphical terminal the following function returns the sizes of the areas described above: @defun frame-geometry &optional frame This function returns geometric attributes of @var{frame}. The return value is an association list of the attributes listed below. All coordinate, height and width values are integers counting pixels. Note that if @var{frame} has not been mapped yet, (@pxref{Visibility of Frames}) some of the return values may only represent approximations of the actual values---those that can be seen after the frame has been mapped. @table @code @item outer-position A cons representing the absolute position of the outer @var{frame}, relative to the origin at position (0, 0) of @var{frame}'s display. @item outer-size A cons of the outer width and height of @var{frame}. @item external-border-size A cons of the horizontal and vertical width of @var{frame}'s external borders as supplied by the window manager. If the window manager doesn't supply these values, Emacs will try to guess them from the coordinates of the outer and inner frame. @item outer-border-width The width of the outer border of @var{frame}. The value is meaningful for non-GTK+ X builds only. @item title-bar-size A cons of the width and height of the title bar of @var{frame} as supplied by the window manager or operating system. If both of them are zero, the frame has no title bar. If only the width is zero, Emacs was not able to retrieve the width information. @item menu-bar-external If non-@code{nil}, this means the menu bar is external (not part of the native frame of @var{frame}). @item menu-bar-size A cons of the width and height of the menu bar of @var{frame}. @item tool-bar-external If non-@code{nil}, this means the tool bar is external (not part of the native frame of @var{frame}). @item tool-bar-position This tells on which side the tool bar on @var{frame} is and can be one of @code{left}, @code{top}, @code{right} or @code{bottom}. The only toolkit that currently supports a value other than @code{top} is GTK+. @item tool-bar-size A cons of the width and height of the tool bar of @var{frame}. @item internal-border-width The width of the internal border of @var{frame}. @end table @end defun The following function can be used to retrieve the edges of the outer, native and inner frame. @defun frame-edges &optional frame type This function returns the absolute edges of the outer, native or inner frame of @var{frame}. @var{frame} must be a live frame and defaults to the selected one. The returned list has the form @w{@code{(@var{left} @var{top} @var{right} @var{bottom})}} where all values are in pixels relative to the origin of @var{frame}'s display. For terminal frames the values returned for @var{left} and @var{top} are always zero. Optional argument @var{type} specifies the type of the edges to return: @code{outer-edges} means to return the outer edges of @var{frame}, @code{native-edges} (or @code{nil}) means to return its native edges and @code{inner-edges} means to return its inner edges. By convention, the pixels of the display at the values returned for @var{left} and @var{top} are considered to be inside (part of) @var{frame}. Hence, if @var{left} and @var{top} are both zero, the pixel at the display's origin is part of @var{frame}. The pixels at @var{bottom} and @var{right}, on the other hand, are considered to lie immediately outside @var{frame}. This means that if you have, for example, two side-by-side frames positioned such that the right outer edge of the frame on the left equals the left outer edge of the frame on the right, the pixels at that edge show a part of the frame on the right. @end defun @node Frame Font @subsection Frame Font @cindex default font @cindex default character size @cindex default character width @cindex default width of character @cindex default character height @cindex default height of character Each frame has a @dfn{default font} which specifies the default character size for that frame. This size is meant when retrieving or changing the size of a frame in terms of columns or lines (@pxref{Size Parameters}). It is also used when resizing (@pxref{Window Sizes}) or splitting (@pxref{Splitting Windows}) windows. @cindex line height @cindex column width @cindex canonical character height @cindex canonical character width The terms @dfn{line height} and @dfn{canonical character height} are sometimes used instead of ``default character height''. Similarly, the terms @dfn{column width} and @dfn{canonical character width} are used instead of ``default character width''. @defun frame-char-height &optional frame @defunx frame-char-width &optional frame These functions return the default height and width of a character in @var{frame}, measured in pixels. Together, these values establish the size of the default font on @var{frame}. The values depend on the choice of font for @var{frame}, see @ref{Font and Color Parameters}. @end defun The default font can be also set directly with the following function: @deffn Command set-frame-font font &optional keep-size frames This sets the default font to @var{font}. When called interactively, it prompts for the name of a font, and uses that font on the selected frame. When called from Lisp, @var{font} should be a font name (a string), a font object, font entity, or a font spec. If the optional argument @var{keep-size} is @code{nil}, this keeps the number of frame lines and columns fixed. (If non-@code{nil}, the option @code{frame-inhibit-implied-resize} described in the next section will override this.) If @var{keep-size} is non-@code{nil} (or with a prefix argument), it tries to keep the size of the display area of the current frame fixed by adjusting the number of lines and columns. If the optional argument @var{frames} is @code{nil}, this applies the font to the selected frame only. If @var{frames} is non-@code{nil}, it should be a list of frames to act upon, or @code{t} meaning all existing and all future graphical frames. @end deffn @node Frame Position @subsection Frame Position @cindex frame position @cindex position of frame On graphical systems, the position of a normal top-level frame is specified as the absolute position of its outer frame (@pxref{Frame Geometry}). The position of a child frame (@pxref{Child Frames}) is specified via pixel offsets of its outer edges relative to the native position of its parent frame. You can access or change the position of a frame using the frame parameters @code{left} and @code{top} (@pxref{Position Parameters}). Here are two additional functions for working with the positions of an existing, visible frame. For both functions, the argument @var{frame} must denote a live frame and defaults to the selected frame. @defun frame-position &optional frame For a normal, non-child frame this function returns a cons of the pixel coordinates of its outer position (@pxref{Frame Layout}) with respect to the origin @code{(0, 0)} of its display. For a child frame (@pxref{Child Frames}) this function returns the pixel coordinates of its outer position with respect to an origin @code{(0, 0)} at the native position of @var{frame}'s parent. Negative values never indicate an offset from the right or bottom edge of @var{frame}'s display or parent frame. Rather, they mean that @var{frame}'s outer position is on the left and/or above the origin of its display or the native position of its parent frame. This usually means that @var{frame} is only partially visible (or completely invisible). However, on systems where the display's origin does not coincide with its top-left corner, the frame may be visible on a secondary monitor. On a text terminal frame both values are zero. @end defun @defun set-frame-position frame x y This function sets the outer frame position of @var{frame} to (@var{x}, @var{y}). The latter arguments specify pixels and normally count from the origin at the position (0, 0) of @var{frame}'s display. For child frames, they count from the native position of @var{frame}'s parent frame. Negative parameter values position the right edge of the outer frame by @var{-x} pixels left from the right edge of the screen (or the parent frame's native rectangle) and the bottom edge by @var{-y} pixels up from the bottom edge of the screen (or the parent frame's native rectangle). Note that negative values do not permit to align the right or bottom edge of @var{frame} exactly at the right or bottom edge of its display or parent frame. Neither do they allow to specify a position that does not lie within the edges of the display or parent frame. The frame parameters @code{left} and @code{top} (@pxref{Position Parameters}) allow to do that, but may still fail to provide good results for the initial or a new frame. This function has no effect on text terminal frames. @end defun @defvar move-frame-functions @cindex frame position changes, a hook This hook specifies the functions that are run when an Emacs frame is moved (assigned a new position) by the window-system or window manager. The functions are run with one argument, the frame that moved. For a child frame (@pxref{Child Frames}), the functions are run only when the position of the frame changes in relation to that of its parent frame. @end defvar @node Frame Size @subsection Frame Size @cindex frame size @cindex text width of a frame @cindex text height of a frame @cindex text size of a frame The canonical way to specify the @dfn{size of a frame} from within Emacs is by specifying its @dfn{text size}---a tuple of the width and height of the frame's text area (@pxref{Frame Layout}). It can be measured either in pixels or in terms of the frame's canonical character size (@pxref{Frame Font}). For frames with an internal menu or tool bar, the frame's native height cannot be told exactly before the frame has been actually drawn. This means that in general you cannot use the native size to specify the initial size of a frame. As soon as you know the native size of a visible frame, you can calculate its outer size (@pxref{Frame Layout}) by adding in the remaining components from the return value of @code{frame-geometry}. For invisible frames or for frames that have yet to be created, however, the outer size can only be estimated. This also means that calculating an exact initial position of a frame specified via offsets from the right or bottom edge of the screen (@pxref{Frame Position}) is impossible. The text size of any frame can be set and retrieved with the help of the @code{height} and @code{width} frame parameters (@pxref{Size Parameters}). The text size of the initial frame can be also set with the help of an X-style geometry specification. @xref{Emacs Invocation,, Command Line Arguments for Emacs Invocation, emacs, The GNU Emacs Manual}. Below we list some functions to access and set the size of an existing, visible frame, by default the selected one. @defun frame-height &optional frame @defunx frame-width &optional frame These functions return the height and width of the text area of @var{frame}, measured in units of the default font height and width of @var{frame} (@pxref{Frame Font}). These functions are plain shorthands for writing @code{(frame-parameter frame 'height)} and @code{(frame-parameter frame 'width)}. If the text area of @var{frame} measured in pixels is not a multiple of its default font size, the values returned by these functions are rounded down to the number of characters of the default font that fully fit into the text area. @end defun The functions following next return the pixel widths and heights of the native, outer and inner frame and the text area (@pxref{Frame Layout}) of a given frame. For a text terminal, the results are in characters rather than pixels. @defun frame-outer-width &optional frame @defunx frame-outer-height &optional frame These functions return the outer width and height of @var{frame} in pixels. @end defun @defun frame-native-height &optional frame @defunx frame-native-width &optional frame These functions return the native width and height of @var{frame} in pixels. @end defun @defun frame-inner-width &optional frame @defunx frame-inner-height &optional frame These functions return the inner width and height of @var{frame} in pixels. @end defun @defun frame-text-width &optional frame @defunx frame-text-height &optional frame These functions return the width and height of the text area of @var{frame} in pixels. @end defun On window systems that support it, Emacs tries by default to make the text size of a frame measured in pixels a multiple of the frame's character size. This, however, usually means that a frame can be resized only in character size increments when dragging its external borders. It also may break attempts to truly maximize the frame or making it ``fullheight'' or ``fullwidth'' (@pxref{Size Parameters}) leaving some empty space below and/or on the right of the frame. The following option may help in that case. @defopt frame-resize-pixelwise If this option is @code{nil} (the default), a frame's text pixel size is usually rounded to a multiple of the current values of that frame's @code{frame-char-height} and @code{frame-char-width} whenever the frame is resized. If this is non-@code{nil}, no rounding occurs, hence frame sizes can increase/decrease by one pixel. Setting this variable usually causes the next resize operation to pass the corresponding size hints to the window manager. This means that this variable should be set only in a user's initial file; applications should never bind it temporarily. The precise meaning of a value of @code{nil} for this option depends on the toolkit used. Dragging the external border with the mouse is done character-wise provided the window manager is willing to process the corresponding size hints. Calling @code{set-frame-size} (see below) with arguments that do not specify the frame size as an integer multiple of its character size, however, may: be ignored, cause a rounding (GTK+), or be accepted (Lucid, Motif, MS-Windows). With some window managers you may have to set this to non-@code{nil} in order to make a frame appear truly maximized or full-screen. @end defopt @defun set-frame-size frame width height &optional pixelwise This function sets the size of the text area of @var{frame}, measured in terms of the canonical height and width of a character on @var{frame} (@pxref{Frame Font}). The optional argument @var{pixelwise} non-@code{nil} means to measure the new width and height in units of pixels instead. Note that if @code{frame-resize-pixelwise} is @code{nil}, some toolkits may refuse to truly honor the request if it does not increase/decrease the frame size to a multiple of its character size. @end defun @defun set-frame-height frame height &optional pretend pixelwise This function resizes the text area of @var{frame} to a height of @var{height} lines. The sizes of existing windows in @var{frame} are altered proportionally to fit. If @var{pretend} is non-@code{nil}, then Emacs displays @var{height} lines of output in @var{frame}, but does not change its value for the actual height of the frame. This is only useful on text terminals. Using a smaller height than the terminal actually implements may be useful to reproduce behavior observed on a smaller screen, or if the terminal malfunctions when using its whole screen. Setting the frame height directly does not always work, because knowing the correct actual size may be necessary for correct cursor positioning on text terminals. The optional fourth argument @var{pixelwise} non-@code{nil} means that @var{frame} should be @var{height} pixels high. Note that if @code{frame-resize-pixelwise} is @code{nil}, some window managers may refuse to truly honor the request if it does not increase/decrease the frame height to a multiple of its character height. When used interactively, this command will ask the user for the number of lines to set the height of the currently selected frame. You can also provide this value with a numeric prefix. @end defun @defun set-frame-width frame width &optional pretend pixelwise This function sets the width of the text area of @var{frame}, measured in characters. The argument @var{pretend} has the same meaning as in @code{set-frame-height}. The optional fourth argument @var{pixelwise} non-@code{nil} means that @var{frame} should be @var{width} pixels wide. Note that if @code{frame-resize-pixelwise} is @code{nil}, some window managers may refuse to fully honor the request if it does not increase/decrease the frame width to a multiple of its character width. When used interactively, this command will ask the user for the number of columns to set the width of the currently selected frame. You can also provide this value with a numeric prefix. @end defun None of these three functions will make a frame smaller than needed to display all of its windows together with their scroll bars, fringes, margins, dividers, mode and header lines. This contrasts with requests by the window manager triggered, for example, by dragging the external border of a frame with the mouse. Such requests are always honored by clipping, if necessary, portions that cannot be displayed at the right, bottom corner of the frame. The parameters @code{min-width} and @code{min-height} (@pxref{Size Parameters}) can be used to obtain a similar behavior when changing the frame size from within Emacs. @cindex tracking frame size changes The abnormal hook @code{window-size-change-functions} (@pxref{Window Hooks}) tracks all changes of the inner size of a frame including those induced by request of the window-system or window manager. To rule out false positives that might occur when changing only the sizes of a frame's windows without actually changing the size of the inner frame, use the following function. @defun frame-size-changed-p &optional frame This function returns non-@code{nil} when the inner width or height of @var{frame} has changed since @code{window-size-change-functions} was run the last time for @var{frame}. It always returns @code{nil} immediately after running @code{window-size-change-functions} for @var{frame}. @end defun @node Implied Frame Resizing @subsection Implied Frame Resizing @cindex implied frame resizing @cindex implied resizing of frame By default, Emacs tries to keep the number of lines and columns of a frame's text area unaltered when, for example, toggling its menu or tool bar, changing its default font or setting the width of any of its scroll bars. This means that in such case Emacs must ask the window manager to resize the frame's window in order to accommodate the size change. Occasionally, such @dfn{implied frame resizing} may be unwanted, for example, when a frame has been maximized or made full-screen (where it's turned off by default). In general, users can disable implied resizing with the following option: @defopt frame-inhibit-implied-resize If this option is @code{nil}, changing a frame's font, menu bar, tool bar, internal borders, fringes or scroll bars may resize its outer frame in order to keep the number of columns or lines of its text area unaltered. If this option is @code{t}, no such resizing is done. The value of this option can be also a list of frame parameters. In that case, implied resizing is inhibited for the change of a parameter that appears in this list. Parameters currently handled by this option are @code{font}, @code{font-backend}, @code{internal-border-width}, @code{menu-bar-lines} and @code{tool-bar-lines}. Changing any of the @code{scroll-bar-width}, @code{scroll-bar-height}, @code{vertical-scroll-bars}, @code{horizontal-scroll-bars}, @code{left-fringe} and @code{right-fringe} frame parameters is handled as if the frame contained just one live window. This means, for example, that removing vertical scroll bars on a frame containing several side by side windows will shrink the outer frame width by the width of one scroll bar provided this option is @code{nil} and keep it unchanged if this option is @code{t} or a list containing @code{vertical-scroll-bars}. The default value is @code{(tab-bar-lines tool-bar-lines)} for Lucid, Motif and MS-Windows (which means that adding/removing a tool or tab bar there does not change the outer frame height), @code{(tab-bar-lines)} on all other window systems including GTK+ (which means that changing any of the parameters listed above with the exception of @code{tab-bar-lines} may change the size of the outer frame), and @code{t} otherwise (which means the outer frame size never changes implicitly when there's no window system support). Note that when a frame is not large enough to accommodate a change of any of the parameters listed above, Emacs may try to enlarge the frame even if this option is non-@code{nil}. Note also that window managers usually do not ask for resizing a frame when they change the number of lines occupied by an external menu or tool bar. Typically, such ``wrappings'' occur when a user shrinks a frame horizontally, making it impossible to display all elements of its menu or tool bar. They may also result from a change of the major mode altering the number of items of a menu or tool bar. Any such wrappings may implicitly alter the number of lines of a frame's text area and are unaffected by the setting of this option. @end defopt @node Frame Parameters @section Frame Parameters @cindex frame parameters A frame has many parameters that control its appearance and behavior. Just what parameters a frame has depends on what display mechanism it uses. Frame parameters exist mostly for the sake of graphical displays. Most frame parameters have no effect when applied to a frame on a text terminal; only the @code{height}, @code{width}, @code{name}, @code{title}, @code{menu-bar-lines}, @code{buffer-list} and @code{buffer-predicate} parameters do something special. If the terminal supports colors, the parameters @code{foreground-color}, @code{background-color}, @code{background-mode} and @code{display-type} are also meaningful. If the terminal supports frame transparency, the parameter @code{alpha} is also meaningful. By default, frame parameters are saved and restored by the desktop library functions (@pxref{Desktop Save Mode}) when the variable @code{desktop-restore-frames} is non-@code{nil}. It's the responsibility of applications that their parameters are included in @code{frameset-persistent-filter-alist} to avoid that they get meaningless or even harmful values in restored sessions. @menu * Parameter Access:: How to change a frame's parameters. * Initial Parameters:: Specifying frame parameters when you make a frame. * Window Frame Parameters:: List of frame parameters for window systems. * Geometry:: Parsing geometry specifications. @end menu @node Parameter Access @subsection Access to Frame Parameters These functions let you read and change the parameter values of a frame. @defun frame-parameter frame parameter This function returns the value of the parameter @var{parameter} (a symbol) of @var{frame}. If @var{frame} is @code{nil}, it returns the selected frame's parameter. If @var{frame} has no setting for @var{parameter}, this function returns @code{nil}. @end defun @defun frame-parameters &optional frame The function @code{frame-parameters} returns an alist listing all the parameters of @var{frame} and their values. If @var{frame} is @code{nil} or omitted, this returns the selected frame's parameters @end defun @defun modify-frame-parameters frame alist This function alters the frame @var{frame} based on the elements of @var{alist}. Each element of @var{alist} has the form @code{(@var{parm} . @var{value})}, where @var{parm} is a symbol naming a parameter. If you don't mention a parameter in @var{alist}, its value doesn't change. If @var{frame} is @code{nil}, it defaults to the selected frame. Some parameters are only meaningful for frames on certain kinds of display (@pxref{Frames}). If @var{alist} includes parameters that are not meaningful for the @var{frame}'s display, this function will change its value in the frame's parameter list, but will otherwise ignore it. When @var{alist} specifies more than one parameter whose value can affect the new size of @var{frame}, the final size of the frame may differ according to the toolkit used. For example, specifying that a frame should from now on have a menu and/or tool bar instead of none and simultaneously specifying the new height of the frame will inevitably lead to a recalculation of the frame's height. Conceptually, in such case, this function will try to have the explicit height specification prevail. It cannot be excluded, however, that the addition (or removal) of the menu or tool bar, when eventually performed by the toolkit, will defeat this intention. Sometimes, binding @code{frame-inhibit-implied-resize} (@pxref{Implied Frame Resizing}) to a non-@code{nil} value around calls to this function may fix the problem sketched here. Sometimes, however, exactly such binding may be hit by the problem. @end defun @defun set-frame-parameter frame parm value This function sets the frame parameter @var{parm} to the specified @var{value}. If @var{frame} is @code{nil}, it defaults to the selected frame. @end defun @defun modify-all-frames-parameters alist This function alters the frame parameters of all existing frames according to @var{alist}, then modifies @code{default-frame-alist} (and, if necessary, @code{initial-frame-alist}) to apply the same parameter values to frames that will be created henceforth. @end defun @node Initial Parameters @subsection Initial Frame Parameters @cindex parameters of initial frame You can specify the parameters for the initial startup frame by setting @code{initial-frame-alist} in your init file (@pxref{Init File}). @defopt initial-frame-alist This variable's value is an alist of parameter values used when creating the initial frame. You can set this variable to specify the appearance of the initial frame without altering subsequent frames. Each element has the form: @example (@var{parameter} . @var{value}) @end example Emacs creates the initial frame before it reads your init file. After reading that file, Emacs checks @code{initial-frame-alist}, and applies the parameter settings in the altered value to the already created initial frame. If these settings affect the frame geometry and appearance, you'll see the frame appear with the wrong ones and then change to the specified ones. If that bothers you, you can specify the same geometry and appearance with X resources; those do take effect before the frame is created. @xref{X Resources,, X Resources, emacs, The GNU Emacs Manual}. X resource settings typically apply to all frames. If you want to specify some X resources solely for the sake of the initial frame, and you don't want them to apply to subsequent frames, here's how to achieve this. Specify parameters in @code{default-frame-alist} to override the X resources for subsequent frames; then, to prevent these from affecting the initial frame, specify the same parameters in @code{initial-frame-alist} with values that match the X resources. @end defopt @cindex minibuffer-only frame If these parameters include @code{(minibuffer . nil)}, that indicates that the initial frame should have no minibuffer. In this case, Emacs creates a separate @dfn{minibuffer-only frame} as well. @defopt minibuffer-frame-alist This variable's value is an alist of parameter values used when creating an initial minibuffer-only frame (i.e., the minibuffer-only frame that Emacs creates if @code{initial-frame-alist} specifies a frame with no minibuffer). @end defopt @defopt default-frame-alist This is an alist specifying default values of frame parameters for all Emacs frames---the first frame, and subsequent frames. When using the X Window System, you can get the same results by means of X resources in many cases. Setting this variable does not affect existing frames. Furthermore, functions that display a buffer in a separate frame may override the default parameters by supplying their own parameters. @end defopt If you invoke Emacs with command-line options that specify frame appearance, those options take effect by adding elements to either @code{initial-frame-alist} or @code{default-frame-alist}. Options which affect just the initial frame, such as @samp{--geometry} and @samp{--maximized}, add to @code{initial-frame-alist}; the others add to @code{default-frame-alist}. @pxref{Emacs Invocation,, Command Line Arguments for Emacs Invocation, emacs, The GNU Emacs Manual}. @node Window Frame Parameters @subsection Window Frame Parameters @cindex frame parameters for windowed displays Just what parameters a frame has depends on what display mechanism it uses. This section describes the parameters that have special meanings on some or all kinds of terminals. Of these, @code{name}, @code{title}, @code{height}, @code{width}, @code{buffer-list} and @code{buffer-predicate} provide meaningful information in terminal frames, and @code{tty-color-mode} is meaningful only for frames on text terminals. @menu * Basic Parameters:: Parameters that are fundamental. * Position Parameters:: The position of the frame on the screen. * Size Parameters:: Frame's size. * Layout Parameters:: Size of parts of the frame, and enabling or disabling some parts. * Buffer Parameters:: Which buffers have been or should be shown. * Frame Interaction Parameters:: Parameters for interacting with other frames. * Mouse Dragging Parameters:: Parameters for resizing and moving frames with the mouse. * Management Parameters:: Communicating with the window manager. * Cursor Parameters:: Controlling the cursor appearance. * Font and Color Parameters:: Fonts and colors for the frame text. @end menu @node Basic Parameters @subsubsection Basic Parameters These frame parameters give the most basic information about the frame. @code{title} and @code{name} are meaningful on all terminals. @table @code @vindex display@r{, a frame parameter} @item display The display on which to open this frame. It should be a string of the form @samp{@var{host}:@var{dpy}.@var{screen}}, just like the @env{DISPLAY} environment variable. @xref{Multiple Terminals}, for more details about display names. @vindex display-type@r{, a frame parameter} @item display-type This parameter describes the range of possible colors that can be used in this frame. Its value is @code{color}, @code{grayscale} or @code{mono}. @vindex title@r{, a frame parameter} @item title If a frame has a non-@code{nil} title, it appears in the window system's title bar at the top of the frame, and also in the mode line of windows in that frame if @code{mode-line-frame-identification} uses @samp{%F} (@pxref{%-Constructs}). This is normally the case when Emacs is not using a window system, and can only display one frame at a time. @xref{Frame Titles}. @vindex name@r{, a frame parameter} @item name The name of the frame. The frame name serves as a default for the frame title, if the @code{title} parameter is unspecified or @code{nil}. If you don't specify a name, Emacs sets the frame name automatically (@pxref{Frame Titles}). If you specify the frame name explicitly when you create the frame, the name is also used (instead of the name of the Emacs executable) when looking up X resources for the frame. @vindex explicit-name@r{, a frame parameter} @item explicit-name If the frame name was specified explicitly when the frame was created, this parameter will be that name. If the frame wasn't explicitly named, this parameter will be @code{nil}. @end table @node Position Parameters @subsubsection Position Parameters @cindex window position on display @cindex frame position Parameters describing the X- and Y-offsets of a frame are always measured in pixels. For a normal, non-child frame they specify the frame's outer position (@pxref{Frame Geometry}) relative to its display's origin. For a child frame (@pxref{Child Frames}) they specify the frame's outer position relative to the native position of the frame's parent frame. (Note that none of these parameters is meaningful on TTY frames.) @table @code @vindex left@r{, a frame parameter} @item left The position, in pixels, of the left outer edge of the frame with respect to the left edge of the frame's display or parent frame. It can be specified in one of the following ways. @table @asis @item an integer A positive integer always relates the left edge of the frame to the left edge of its display or parent frame. A negative integer relates the right frame edge to the right edge of the display or parent frame. @item @code{(+ @var{pos})} This specifies the position of the left frame edge relative to the left edge of its display or parent frame. The integer @var{pos} may be positive or negative; a negative value specifies a position outside the screen or parent frame or on a monitor other than the primary one (for multi-monitor displays). @item @code{(- @var{pos})} This specifies the position of the right frame edge relative to the right edge of the display or parent frame. The integer @var{pos} may be positive or negative; a negative value specifies a position outside the screen or parent frame or on a monitor other than the primary one (for multi-monitor displays). @cindex left position ratio @cindex top position ratio @item a floating-point value A floating-point value in the range 0.0 to 1.0 specifies the left edge's offset via the @dfn{left position ratio} of the frame---the ratio of the left edge of its outer frame to the width of the frame's workarea (@pxref{Multiple Terminals}) or its parent's native frame (@pxref{Child Frames}) minus the width of the outer frame. Thus, a left position ratio of 0.0 flushes a frame to the left, a ratio of 0.5 centers it and a ratio of 1.0 flushes it to the right of its display or parent frame. Similarly, the @dfn{top position ratio} of a frame is the ratio of the frame's top position to the height of its workarea or parent frame minus the height of the frame. Emacs will try to keep the position ratios of a child frame unaltered if that frame has a non-@code{nil} @code{keep-ratio} parameter (@pxref{Frame Interaction Parameters}) and its parent frame is resized. Since the outer size of a frame (@pxref{Frame Geometry}) is usually unavailable before a frame has been made visible, it is generally not advisable to use floating-point values when creating decorated frames. Floating-point values are more suited for ensuring that an (undecorated) child frame is positioned nicely within the area of its parent frame. @end table Some window managers ignore program-specified positions. If you want to be sure the position you specify is not ignored, specify a non-@code{nil} value for the @code{user-position} parameter as in the following example: @example (modify-frame-parameters nil '((user-position . t) (left . (+ -4)))) @end example In general, it is not a good idea to position a frame relative to the right or bottom edge of its display. Positioning the initial or a new frame is either not accurate (because the size of the outer frame is not yet fully known before the frame has been made visible) or will cause additional flicker (if the frame has to be repositioned after becoming visible). Note also, that positions specified relative to the right/bottom edge of a display, workarea or parent frame as well as floating-point offsets are stored internally as integer offsets relative to the left/top edge of the display, workarea or parent frame edge. They are also returned as such by functions like @code{frame-parameters} and restored as such by the desktop saving routines. @vindex top@r{, a frame parameter} @item top The screen position of the top (or bottom) edge, in pixels, with respect to the top (or bottom) edge of the display or parent frame. It works just like @code{left}, except vertically instead of horizontally. @vindex icon-left@r{, a frame parameter} @item icon-left The screen position of the left edge of the frame's icon, in pixels, counting from the left edge of the screen. This takes effect when the frame is iconified, if the window manager supports this feature. If you specify a value for this parameter, then you must also specify a value for @code{icon-top} and vice versa. @vindex icon-top@r{, a frame parameter} @item icon-top The screen position of the top edge of the frame's icon, in pixels, counting from the top edge of the screen. This takes effect when the frame is iconified, if the window manager supports this feature. @vindex user-position@r{, a frame parameter} @item user-position When you create a frame and specify its screen position with the @code{left} and @code{top} parameters, use this parameter to say whether the specified position was user-specified (explicitly requested in some way by a human user) or merely program-specified (chosen by a program). A non-@code{nil} value says the position was user-specified. @cindex window positions and window managers Window managers generally heed user-specified positions, and some heed program-specified positions too. But many ignore program-specified positions, placing the window in a default fashion or letting the user place it with the mouse. Some window managers, including @code{twm}, let the user specify whether to obey program-specified positions or ignore them. When you call @code{make-frame}, you should specify a non-@code{nil} value for this parameter if the values of the @code{left} and @code{top} parameters represent the user's stated preference; otherwise, use @code{nil}. @vindex z-group@r{, a frame parameter} @item z-group This parameter specifies a relative position of the frame's window-system window in the stacking (Z-) order of the frame's display. If this is @code{above}, the window-system will display the window that corresponds to the frame above all other window-system windows that do not have the @code{above} property set. If this is @code{nil}, the frame's window is displayed below all windows that have the @code{above} property set and above all windows that have the @code{below} property set. If this is @code{below}, the frame's window is displayed below all windows that do not have the @code{below} property set. To position the frame above or below a specific other frame use the function @code{frame-restack} (@pxref{Raising and Lowering}). @end table @node Size Parameters @subsubsection Size Parameters @cindex window size on display Frame parameters usually specify frame sizes in character units. On graphical displays, the @code{default} face determines the actual pixel sizes of these character units (@pxref{Face Attributes}). @table @code @vindex width@r{, a frame parameter} @item width This parameter specifies the width of the frame. It can be specified as in the following ways: @table @asis @item an integer A positive integer specifies the width of the frame's text area (@pxref{Frame Geometry}) in characters. @item a cons cell If this is a cons cell with the symbol @code{text-pixels} in its @sc{car}, the @sc{cdr} of that cell specifies the width of the frame's text area in pixels. @cindex frame width ratio @cindex frame height ratio @item a floating-point value A floating-point number between 0.0 and 1.0 can be used to specify the width of a frame via its @dfn{width ratio}---the ratio of its outer width (@pxref{Frame Geometry}) to the width of the frame's workarea (@pxref{Multiple Terminals}) or its parent frame's (@pxref{Child Frames}) native frame. Thus, a value of 0.5 makes the frame occupy half of the width of its workarea or parent frame, a value of 1.0 the full width. Similarly, the @dfn{height ratio} of a frame is the ratio of its outer height to the height of its workarea or its parent's native frame. Emacs will try to keep the width and height ratio of a child frame unaltered if that frame has a non-@code{nil} @code{keep-ratio} parameter (@pxref{Frame Interaction Parameters}) and its parent frame is resized. Since the outer size of a frame is usually unavailable before a frame has been made visible, it is generally not advisable to use floating-point values when creating decorated frames. Floating-point values are more suited to ensure that a child frame always fits within the area of its parent frame as, for example, when customizing @code{display-buffer-alist} (@pxref{Choosing Window}) via @code{display-buffer-in-child-frame}. @end table Regardless of how this parameter was specified, functions reporting the value of this parameter like @code{frame-parameters} always report the width of the frame's text area in characters as an integer rounded, if necessary, to a multiple of the frame's default character width. That value is also used by the desktop saving routines. @vindex height@r{, a frame parameter} @item height This parameter specifies the height of the frame. It works just like @code{width}, except vertically instead of horizontally. @vindex user-size@r{, a frame parameter} @item user-size This does for the size parameters @code{height} and @code{width} what the @code{user-position} parameter (@pxref{Position Parameters, user-position}) does for the position parameters @code{top} and @code{left}. @vindex min-width@r{, a frame parameter} @item min-width This parameter specifies the minimum native width (@pxref{Frame Geometry}) of the frame, in characters. Normally, the functions that establish a frame's initial width or resize a frame horizontally make sure that all the frame's windows, vertical scroll bars, fringes, margins and vertical dividers can be displayed. This parameter, if non-@code{nil} allows to make a frame narrower than that with the consequence that any components that do not fit will be clipped by the window manager. @vindex min-height@r{, a frame parameter} @item min-height This parameter specifies the minimum native height (@pxref{Frame Geometry}) of the frame, in characters. Normally, the functions that establish a frame's initial size or resize a frame make sure that all the frame's windows, horizontal scroll bars and dividers, mode and header lines, the echo area and the internal menu and tool bar can be displayed. This parameter, if non-@code{nil} allows to make a frame smaller than that with the consequence that any components that do not fit will be clipped by the window manager. @cindex fullboth frames @cindex fullheight frames @cindex fullwidth frames @cindex maximized frames @vindex fullscreen@r{, a frame parameter} @item fullscreen This parameter specifies whether to maximize the frame's width, height or both. Its value can be @code{fullwidth}, @code{fullheight}, @code{fullboth}, or @code{maximized}.@footnote{On Haiku, setting @code{fullscreen} to @code{fullwidth} or @code{fullheight} has no effect.} A @dfn{fullwidth} frame is as wide as possible, a @dfn{fullheight} frame is as tall as possible, and a @dfn{fullboth} frame is both as wide and as tall as possible. A @dfn{maximized} frame is like a ``fullboth'' frame, except that it usually keeps its title bar and the buttons for resizing and closing the frame. Also, maximized frames typically avoid hiding any task bar or panels displayed on the desktop. A ``fullboth'' frame, on the other hand, usually omits the title bar and occupies the entire available screen space. Full-height and full-width frames are more similar to maximized frames in this regard. However, these typically display an external border which might be absent with maximized frames. Hence the heights of maximized and full-height frames and the widths of maximized and full-width frames often differ by a few pixels. With some window managers you may have to customize the variable @code{frame-resize-pixelwise} (@pxref{Frame Size}) in order to make a frame truly appear maximized or full-screen. Moreover, some window managers might not support smooth transition between the various full-screen or maximization states. Customizing the variable @code{x-frame-normalize-before-maximize} can help to overcome that. Full-screen on macOS hides both the tool-bar and the menu-bar, however both will be displayed if the mouse pointer is moved to the top of the screen. @vindex fullscreen-restore@r{, a frame parameter} @item fullscreen-restore This parameter specifies the desired fullscreen state of the frame after invoking the @code{toggle-frame-fullscreen} command (@pxref{Frame Commands,,, emacs, The GNU Emacs Manual}) in the ``fullboth'' state. Normally this parameter is installed automatically by that command when toggling the state to fullboth. If, however, you start Emacs in the ``fullboth'' state, you have to specify the desired behavior in your initial file as, for example @example (setq default-frame-alist '((fullscreen . fullboth) (fullscreen-restore . fullheight))) @end example This will give a new frame full height after typing in it @key{F11} for the first time. @vindex fit-frame-to-buffer-margins@r{, a frame parameter} @item fit-frame-to-buffer-margins This parameter allows to override the value of the option @code{fit-frame-to-buffer-margins} when fitting this frame to the buffer of its root window with @code{fit-frame-to-buffer} (@pxref{Resizing Windows}). @vindex fit-frame-to-buffer-sizes@r{, a frame parameter} @item fit-frame-to-buffer-sizes This parameter allows to override the value of the option @code{fit-frame-to-buffer-sizes} when fitting this frame to the buffer of its root window with @code{fit-frame-to-buffer} (@pxref{Resizing Windows}). @end table @node Layout Parameters @subsubsection Layout Parameters @cindex layout parameters of frames @cindex frame layout parameters These frame parameters enable or disable various parts of the frame, or control their sizes. @table @code @vindex border-width@r{, a frame parameter} @item border-width The width in pixels of the frame's outer border (@pxref{Frame Geometry}). @vindex internal-border-width@r{, a frame parameter} @item internal-border-width The width in pixels of the frame's internal border (@pxref{Frame Geometry}). @vindex child-frame-border-width@r{, a frame parameter} @item child-frame-border-width The width in pixels of the frame's internal border (@pxref{Frame Geometry}) if the given frame is a child frame (@pxref{Child Frames}). If this is @code{nil}, the value specified by the @code{internal-border-width} parameter is used instead. @vindex vertical-scroll-bars@r{, a frame parameter} @item vertical-scroll-bars Whether the frame has scroll bars (@pxref{Scroll Bars}) for vertical scrolling, and which side of the frame they should be on. The possible values are @code{left}, @code{right}, and @code{nil} for no scroll bars. @vindex horizontal-scroll-bars@r{, a frame parameter} @item horizontal-scroll-bars Whether the frame has scroll bars for horizontal scrolling (@code{t} and @code{bottom} mean yes, @code{nil} means no). @vindex scroll-bar-width@r{, a frame parameter} @item scroll-bar-width The width of vertical scroll bars, in pixels, or @code{nil} meaning to use the default width. @vindex scroll-bar-height@r{, a frame parameter} @item scroll-bar-height The height of horizontal scroll bars, in pixels, or @code{nil} meaning to use the default height. @vindex left-fringe@r{, a frame parameter} @vindex right-fringe@r{, a frame parameter} @item left-fringe @itemx right-fringe The default width of the left and right fringes of windows in this frame (@pxref{Fringes}). If either of these is zero, that effectively removes the corresponding fringe. When you use @code{frame-parameter} to query the value of either of these two frame parameters, the return value is always an integer. When using @code{set-frame-parameter}, passing a @code{nil} value imposes an actual default value of 8 pixels. @vindex right-divider-width@r{, a frame parameter} @item right-divider-width The width (thickness) reserved for the right divider (@pxref{Window Dividers}) of any window on the frame, in pixels. A value of zero means to not draw right dividers. @vindex bottom-divider-width@r{, a frame parameter} @item bottom-divider-width The width (thickness) reserved for the bottom divider (@pxref{Window Dividers}) of any window on the frame, in pixels. A value of zero means to not draw bottom dividers. @vindex menu-bar-lines@r{, a frame parameter} @item menu-bar-lines The number of lines to allocate at the top of the frame for a menu bar (@pxref{Menu Bar}). The default is one if Menu Bar mode is enabled and zero otherwise. @xref{Menu Bars,,,emacs, The GNU Emacs Manual}. For an external menu bar (@pxref{Frame Layout}), this value remains unchanged even when the menu bar wraps to two or more lines. In that case, the @code{menu-bar-size} value returned by @code{frame-geometry} (@pxref{Frame Geometry}) allows to derive whether the menu bar actually occupies one or more lines. @vindex tool-bar-lines@r{, a frame parameter} @item tool-bar-lines The number of lines to use for the tool bar (@pxref{Tool Bar}). The default is one if Tool Bar mode is enabled and zero otherwise. @xref{Tool Bars,,,emacs, The GNU Emacs Manual}. This value may change whenever the tool bar wraps (@pxref{Frame Layout}). @vindex tool-bar-position@r{, a frame parameter} @item tool-bar-position The position of the tool bar when Emacs was built with GTK+. Its value can be one of @code{top}, @code{bottom} @code{left}, @code{right}. The default is @code{top}. @vindex tab-bar-lines@r{, a frame parameter} @item tab-bar-lines The number of lines to use for the tab bar (@pxref{Tab Bars,,,emacs, The GNU Emacs Manual}). The default is one if Tab Bar mode is enabled and zero otherwise. This value may change whenever the tab bar wraps (@pxref{Frame Layout}). @vindex line-spacing@r{, a frame parameter} @item line-spacing Additional space to leave below each text line, in pixels (a positive integer). @xref{Line Height}, for more information. @vindex no-special-glyphs@r{, a frame parameter} @item no-special-glyphs If this is non-@code{nil}, it suppresses the display of any truncation and continuation glyphs (@pxref{Truncation}) for all buffers displayed by this frame. This is useful to eliminate such glyphs when fitting a frame to its buffer via @code{fit-frame-to-buffer} (@pxref{Resizing Windows}). @end table @node Buffer Parameters @subsubsection Buffer Parameters @cindex frame, which buffers to display @cindex buffers to display on frame These frame parameters, meaningful on all kinds of terminals, deal with which buffers have been, or should, be displayed in the frame. @table @code @vindex minibuffer@r{, a frame parameter} @item minibuffer Whether this frame has its own minibuffer. The value @code{t} means yes, @code{nil} means no, @code{only} means this frame is just a minibuffer. If the value is a minibuffer window (in some other frame), the frame uses that minibuffer. This parameter takes effect when the frame is created. If specified as @code{nil}, Emacs will try to set it to the minibuffer window of @code{default-minibuffer-frame} (@pxref{Minibuffers and Frames}). For an existing frame, this parameter can be used exclusively to specify another minibuffer window. It is not allowed to change it from a minibuffer window to @code{t} and vice-versa, or from @code{t} to @code{nil}. If the parameter specifies a minibuffer window already, setting it to @code{nil} has no effect. The special value @code{child-frame} means to make a minibuffer-only child frame (@pxref{Child Frames}) whose parent becomes the frame created. As if specified as @code{nil}, Emacs will set this parameter to the minibuffer window of the child frame but will not select the child frame after its creation. @vindex buffer-predicate@r{, a frame parameter} @item buffer-predicate The buffer-predicate function for this frame. The function @code{other-buffer} uses this predicate (from the selected frame) to decide which buffers it should consider, if the predicate is not @code{nil}. It calls the predicate with one argument, a buffer, once for each buffer; if the predicate returns a non-@code{nil} value, it considers that buffer. @vindex buffer-list@r{, a frame parameter} @item buffer-list A list of buffers that have been selected in this frame, ordered most-recently-selected first. @vindex unsplittable@r{, a frame parameter} @item unsplittable If non-@code{nil}, this frame's window is never split automatically. @end table @node Frame Interaction Parameters @subsubsection Frame Interaction Parameters @cindex frame interaction parameters @cindex interaction parameters between frames These parameters supply forms of interactions between different frames. @table @code @vindex parent-frame@r{, a frame parameter} @item parent-frame If non-@code{nil}, this means that this frame is a child frame (@pxref{Child Frames}), and this parameter specifies its parent frame. If @code{nil}, this means that this frame is a normal, top-level frame. @vindex delete-before@r{, a frame parameter} @item delete-before If non-@code{nil}, this parameter specifies another frame whose deletion will automatically trigger the deletion of this frame. @xref{Deleting Frames}. @vindex mouse-wheel-frame@r{, a frame parameter} @item mouse-wheel-frame If non-@code{nil}, this parameter specifies the frame whose windows will be scrolled whenever the mouse wheel is scrolled with the mouse pointer hovering over this frame, see @ref{Mouse Commands,,, emacs, The GNU Emacs Manual}. @vindex no-other-frame@r{, a frame parameter} @item no-other-frame If this is non-@code{nil}, then this frame is not eligible as candidate for the functions @code{next-frame}, @code{previous-frame} (@pxref{Finding All Frames}) and @code{other-frame}, see @ref{Frame Commands,,, emacs, The GNU Emacs Manual}. @vindex auto-hide-function@r{, a frame parameter} @item auto-hide-function When this parameter specifies a function, that function will be called instead of the function specified by the variable @code{frame-auto-hide-function} when quitting the frame's only window (@pxref{Quitting Windows}) and there are other frames left. @vindex minibuffer-exit@r{, a frame parameter} @item minibuffer-exit When this parameter is non-@code{nil}, Emacs will by default make this frame invisible whenever the minibuffer (@pxref{Minibuffers}) is exited. Alternatively, it can specify the functions @code{iconify-frame} and @code{delete-frame}. This parameter is useful to make a child frame disappear automatically (similar to how Emacs deals with a window) when exiting the minibuffer. @vindex keep-ratio@r{, a frame parameter} @item keep-ratio This parameter is currently meaningful for child frames (@pxref{Child Frames}) only. If it is non-@code{nil}, then Emacs will try to keep the frame's size (width and height) ratios (@pxref{Size Parameters}) as well as its left and right position ratios (@pxref{Position Parameters}) unaltered whenever its parent frame is resized. If the value of this parameter is @code{nil}, the frame's position and size remain unaltered when the parent frame is resized, so the position and size ratios may change. If the value of this parameter is @code{t}, Emacs will try to preserve the frame's size and position ratios, hence the frame's size and position relative to its parent frame may change. More individual control is possible by using a cons cell: In that case the frame's width ratio is preserved if the @sc{car} of the cell is either @code{t} or @code{width-only}. The height ratio is preserved if the @sc{car} of the cell is either @code{t} or @code{height-only}. The left position ratio is preserved if the @sc{cdr} of the cell is either @code{t} or @code{left-only}. The top position ratio is preserved if the @sc{cdr} of the cell is either @code{t} or @code{top-only}. @end table @node Mouse Dragging Parameters @subsubsection Mouse Dragging Parameters @cindex mouse dragging parameters @cindex parameters for resizing frames with the mouse @cindex parameters for moving frames with the mouse The parameters described below provide support for resizing a frame by dragging its internal borders with the mouse. They also allow moving a frame with the mouse by dragging the header or tab line of its topmost or the mode line of its bottommost window. These parameters are mostly useful for child frames (@pxref{Child Frames}) that come without window manager decorations. If necessary, they can be used for undecorated top-level frames as well. @table @code @vindex drag-internal-border@r{, a frame parameter} @item drag-internal-border If non-@code{nil}, the frame can be resized by dragging its internal borders, if present, with the mouse. @vindex drag-with-header-line@r{, a frame parameter} @item drag-with-header-line If non-@code{nil}, the frame can be moved with the mouse by dragging the header line of its topmost window. @vindex drag-with-tab-line@r{, a frame parameter} @item drag-with-tab-line If non-@code{nil}, the frame can be moved with the mouse by dragging the tab line of its topmost window. @vindex drag-with-mode-line@r{, a frame parameter} @item drag-with-mode-line If non-@code{nil}, the frame can be moved with the mouse by dragging the mode line of its bottommost window. Note that such a frame is not allowed to have its own minibuffer window. @vindex snap-width@r{, a frame parameter} @item snap-width A frame that is moved with the mouse will ``snap'' at the border(s) of the display or its parent frame whenever it is dragged as near to such an edge as the number of pixels specified by this parameter. @vindex top-visible@r{, a frame parameter} @item top-visible If this parameter is a number, the top edge of the frame never appears above the top edge of its display or parent frame. Moreover, as many pixels of the frame as specified by that number will remain visible when the frame is moved against any of the remaining edges of its display or parent frame. Setting this parameter is useful to guard against dragging a child frame with a non-@code{nil} @code{drag-with-header-line} parameter completely out of the area of its parent frame. @vindex bottom-visible@r{, a frame parameter} @item bottom-visible If this parameter is a number, the bottom edge of the frame never appears below the bottom edge of its display or parent frame. Moreover, as many pixels of the frame as specified by that number will remain visible when the frame is moved against any of the remaining edges of its display or parent frame. Setting this parameter is useful to guard against dragging a child frame with a non-@code{nil} @code{drag-with-mode-line} parameter completely out of the area of its parent frame. @end table @node Management Parameters @subsubsection Window Management Parameters @cindex window manager interaction, and frame parameters The following frame parameters control various aspects of the frame's interaction with the window manager or window system. They have no effect on text terminals. @table @code @vindex visibility@r{, a frame parameter} @item visibility The state of visibility of the frame. There are three possibilities: @code{nil} for invisible, @code{t} for visible, and @code{icon} for iconified. @xref{Visibility of Frames}. @vindex auto-raise@r{, a frame parameter} @item auto-raise If non-@code{nil}, Emacs automatically raises the frame when it is selected. Some window managers do not allow this. @vindex auto-lower@r{, a frame parameter} @item auto-lower If non-@code{nil}, Emacs automatically lowers the frame when it is deselected. Some window managers do not allow this. @vindex icon-type@r{, a frame parameter} @item icon-type The type of icon to use for this frame. If the value is a string, that specifies a file containing a bitmap to use; @code{nil} specifies no icon (in which case the window manager decides what to show); any other non-@code{nil} value specifies the default Emacs icon. @vindex icon-name@r{, a frame parameter} @item icon-name The name to use in the icon for this frame, when and if the icon appears. If this is @code{nil}, the frame's title is used. @vindex window-id@r{, a frame parameter} @item window-id The ID number which the graphical display uses for this frame. Emacs assigns this parameter when the frame is created; changing the parameter has no effect on the actual ID number. @vindex outer-window-id@r{, a frame parameter} @item outer-window-id The ID number of the outermost window-system window in which the frame exists. As with @code{window-id}, changing this parameter has no actual effect. @vindex wait-for-wm@r{, a frame parameter} @item wait-for-wm If non-@code{nil}, tell Xt to wait for the window manager to confirm geometry changes. Some window managers, including versions of Fvwm2 and KDE, fail to confirm, so Xt hangs. Set this to @code{nil} to prevent hanging with those window managers. @vindex sticky@r{, a frame parameter} @item sticky If non-@code{nil}, the frame is visible on all virtual desktops on systems with virtual desktops. @vindex inhibit-double-buffering@r{, a frame parameter} @item inhibit-double-buffering If non-@code{nil}, the frame is drawn to the screen without double buffering. Emacs normally attempts to use double buffering, where available, to reduce flicker. Set this property if you experience display bugs or pine for that retro, flicker-y feeling. @vindex skip-taskbar@r{, a frame parameter} @item skip-taskbar If non-@code{nil}, this tells the window manager to remove the frame's icon from the taskbar associated with the frame's display and inhibit switching to the frame's window via the combination @kbd{Alt-@key{TAB}}. On MS-Windows, iconifying such a frame will "roll in" its window-system window at the bottom of the desktop. Some window managers may not honor this parameter. @vindex no-focus-on-map@r{, a frame parameter} @item no-focus-on-map If non-@code{nil}, this means that the frame does not want to receive input focus when it is mapped (@pxref{Visibility of Frames}). Some window managers may not honor this parameter. @vindex no-accept-focus@r{, a frame parameter} @item no-accept-focus If non-@code{nil}, this means that the frame does not want to receive input focus via explicit mouse clicks or when moving the mouse into it either via @code{focus-follows-mouse} (@pxref{Input Focus}) or @code{mouse-autoselect-window} (@pxref{Mouse Window Auto-selection}). This may have the unwanted side-effect that a user cannot scroll a non-selected frame with the mouse. Some window managers may not honor this parameter. On Haiku, it also has the side-effect that the window will not be able to receive any keyboard input from the user, not even if the user switches to the frame using the key combination @kbd{Alt-@key{TAB}}. @vindex undecorated@r{, a frame parameter} @item undecorated If non-@code{nil}, this frame's window-system window is drawn without decorations, like the title, minimize/maximize boxes and external borders. This usually means that the window cannot be dragged, resized, iconified, maximized or deleted with the mouse. If @code{nil}, the frame's window is usually drawn with all the elements listed above unless their display has been suspended via window manager settings. Under X, Emacs uses the Motif window manager hints to turn off decorations. Some window managers may not honor these hints. NS builds consider the tool bar to be a decoration, and therefore hide it on an undecorated frame. @vindex override-redirect@r{, a frame parameter} @item override-redirect @cindex override redirect frames If non-@code{nil}, this means that this is an @dfn{override redirect} frame---a frame not handled by window managers under X@. Override redirect frames have no window manager decorations, can be positioned and resized only via Emacs' positioning and resizing functions and are usually drawn on top of all other frames. Setting this parameter has no effect on MS-Windows. @ignore @vindex parent-id@r{, a frame parameter} @item parent-id @c ??? Not yet working. The X window number of the window that should be the parent of this one. Specifying this lets you create an Emacs window inside some other application's window. (It is not certain this will be implemented; try it and see if it works.) @end ignore @vindex ns-appearance@r{, a frame parameter} @item ns-appearance Only available on macOS, if set to @code{dark} draw this frame's window-system window using the ``vibrant dark'' theme, and if set to @code{light} use the ``aqua'' theme, otherwise use the system default. The ``vibrant dark'' theme can be used to set the toolbar and scrollbars to a dark appearance when using an Emacs theme with a dark background. @vindex ns-transparent-titlebar@r{, a frame parameter} @item ns-transparent-titlebar Only available on macOS, if non-@code{nil}, set the titlebar and toolbar to be transparent. This effectively sets the background color of both to match the Emacs background color. @end table @node Cursor Parameters @subsubsection Cursor Parameters @cindex cursor, and frame parameters This frame parameter controls the way the cursor looks. @table @code @vindex cursor-type@r{, a frame parameter} @item cursor-type How to display the cursor. Legitimate values are: @table @code @item box Display a filled box. (This is the default.) @item (box . @var{size}) Display a filled box. However, display it as a hollow box if point is under masked image larger than @var{size} pixels in either dimension. @item hollow Display a hollow box. @item nil Don't display a cursor. @item bar Display a vertical bar between characters. @item (bar . @var{width}) Display a vertical bar @var{width} pixels wide between characters. @item hbar Display a horizontal bar. @item (hbar . @var{height}) Display a horizontal bar @var{height} pixels high. @end table @end table @vindex cursor-type The @code{cursor-type} frame parameter may be overridden by the variables @code{cursor-type} and @code{cursor-in-non-selected-windows}: @defopt cursor-type This buffer-local variable controls how the cursor looks in a selected window showing the buffer. If its value is @code{t}, that means to use the cursor specified by the @code{cursor-type} frame parameter. Otherwise, the value should be one of the cursor types listed above, and it overrides the @code{cursor-type} frame parameter. @end defopt @defopt cursor-in-non-selected-windows This buffer-local variable controls how the cursor looks in a window that is not selected. It supports the same values as the @code{cursor-type} frame parameter; also, @code{nil} means don't display a cursor in nonselected windows, and @code{t} (the default) means use a standard modification of the usual cursor type (solid box becomes hollow box, and bar becomes a narrower bar). @end defopt @defopt x-stretch-cursor This variable controls the width of the block cursor displayed on extra-wide glyphs such as a tab or a stretch of white space. By default, the block cursor is only as wide as the font's default character, and will not cover all of the width of the glyph under it if that glyph is extra-wide. A non-@code{nil} value of this variable means draw the block cursor as wide as the glyph under it. The default value is @code{nil}. This variable has no effect on text-mode frames, since the text-mode cursor is drawn by the terminal out of Emacs's control. @end defopt @defopt blink-cursor-alist This variable specifies how to blink the cursor. Each element has the form @code{(@var{on-state} . @var{off-state})}. Whenever the cursor type equals @var{on-state} (comparing using @code{equal}), the corresponding @var{off-state} specifies what the cursor looks like when it blinks off. Both @var{on-state} and @var{off-state} should be suitable values for the @code{cursor-type} frame parameter. There are various defaults for how to blink each type of cursor, if the type is not mentioned as an @var{on-state} here. Changes in this variable do not take effect immediately, only when you specify the @code{cursor-type} frame parameter. @end defopt @node Font and Color Parameters @subsubsection Font and Color Parameters @cindex font and color, frame parameters These frame parameters control the use of fonts and colors. @table @code @vindex font-backend@r{, a frame parameter} @item font-backend A list of symbols, specifying the @dfn{font backends} to use for drawing characters on the frame, in order of priority. In Emacs built without Cairo drawing on X, there are currently three potentially available font backends: @code{x} (the X core font driver), @code{xft} (the Xft font driver), and @code{xfthb} (the Xft font driver with HarfBuzz text shaping). If built with Cairo drawing, there are also three potentially available font backends on X: @code{x}, @code{ftcr} (the FreeType font driver on Cairo), and @code{ftcrhb} (the FreeType font driver on Cairo with HarfBuzz text shaping). When Emacs is built with HarfBuzz, the default font driver is @code{ftcrhb}, although use of the @code{ftcr} driver is still possible, but not recommended. On MS-Windows, there are currently three available font backends: @code{gdi} (the core MS-Windows font driver), @code{uniscribe} (font driver for OTF and TTF fonts with text shaping by the Uniscribe engine), and @code{harfbuzz} (font driver for OTF and TTF fonts with HarfBuzz text shaping) (@pxref{Windows Fonts,,, emacs, The GNU Emacs Manual}). The @code{harfbuzz} driver is similarly recommended. On Haiku, there can be several font drivers (@pxref{Haiku Fonts,,, emacs, The GNU Emacs Manual}). On other systems, there is only one available font backend, so it does not make sense to modify this frame parameter. @vindex background-mode@r{, a frame parameter} @item background-mode This parameter is either @code{dark} or @code{light}, according to whether the background color is a light one or a dark one. @vindex tty-color-mode@r{, a frame parameter} @item tty-color-mode @cindex standard colors for character terminals This parameter overrides the terminal's color support as given by the system's terminal capabilities database in that this parameter's value specifies the color mode to use on a text terminal. The value can be either a symbol or a number. A number specifies the number of colors to use (and, indirectly, what commands to issue to produce each color). For example, @code{(tty-color-mode . 8)} specifies use of the ANSI escape sequences for 8 standard text colors. A value of @minus{}1 turns off color support. If the parameter's value is a symbol, it specifies a number through the value of @code{tty-color-mode-alist}, and the associated number is used instead. @vindex screen-gamma@r{, a frame parameter} @item screen-gamma @cindex gamma correction If this is a number, Emacs performs gamma correction which adjusts the brightness of all colors. The value should be the screen gamma of your display. Usual PC monitors have a screen gamma of 2.2, so color values in Emacs, and in X windows generally, are calibrated to display properly on a monitor with that gamma value. If you specify 2.2 for @code{screen-gamma}, that means no correction is needed. Other values request correction, designed to make the corrected colors appear on your screen the way they would have appeared without correction on an ordinary monitor with a gamma value of 2.2. If your monitor displays colors too light, you should specify a @code{screen-gamma} value smaller than 2.2. This requests correction that makes colors darker. A screen gamma value of 1.5 may give good results for LCD color displays. @vindex alpha@r{, a frame parameter} @item alpha @cindex opacity, frame @cindex transparency, frame @vindex frame-alpha-lower-limit This parameter specifies the opacity of the frame, on graphical displays that support variable opacity. It should be an integer between 0 and 100, where 0 means completely transparent and 100 means completely opaque. It can also have a @code{nil} value, which tells Emacs not to set the frame opacity (leaving it to the window manager). To prevent the frame from disappearing completely from view, the variable @code{frame-alpha-lower-limit} defines a lower opacity limit. If the value of the frame parameter is less than the value of this variable, Emacs uses the latter. By default, @code{frame-alpha-lower-limit} is 20. The @code{alpha} frame parameter can also be a cons cell @code{(@var{active} . @var{inactive})}, where @var{active} is the opacity of the frame when it is selected, and @var{inactive} is the opacity when it is not selected. Some window systems do not support the @code{alpha} parameter for child frames (@pxref{Child Frames}). @end table The following frame parameters are semi-obsolete in that they are automatically equivalent to particular face attributes of particular faces (@pxref{Standard Faces,,, emacs, The Emacs Manual}): @table @code @vindex font@r{, a frame parameter} @item font The name of the font for displaying text in the frame. This is a string, either a valid font name for your system or the name of an Emacs fontset (@pxref{Fontsets}). It is equivalent to the @code{font} attribute of the @code{default} face. @vindex foreground-color@r{, a frame parameter} @item foreground-color The color to use for characters. It is equivalent to the @code{:foreground} attribute of the @code{default} face. @vindex background-color@r{, a frame parameter} @item background-color The color to use for the background of characters. It is equivalent to the @code{:background} attribute of the @code{default} face. @vindex mouse-color@r{, a frame parameter} @vindex mouse@r{, a face} @item mouse-color The color for the mouse pointer. It is equivalent to the @code{:background} attribute of the @code{mouse} face. @vindex cursor-color@r{, a frame parameter} @item cursor-color The color for the cursor that shows point. It is equivalent to the @code{:background} attribute of the @code{cursor} face. @vindex border-color@r{, a frame parameter} @item border-color The color for the border of the frame. It is equivalent to the @code{:background} attribute of the @code{border} face. @vindex scroll-bar-foreground@r{, a frame parameter} @item scroll-bar-foreground If non-@code{nil}, the color for the foreground of scroll bars. It is equivalent to the @code{:foreground} attribute of the @code{scroll-bar} face. @vindex scroll-bar-background@r{, a frame parameter} @item scroll-bar-background If non-@code{nil}, the color for the background of scroll bars. It is equivalent to the @code{:background} attribute of the @code{scroll-bar} face. @end table @node Geometry @subsection Geometry Here's how to examine the data in an X-style window geometry specification: @defun x-parse-geometry geom @cindex geometry specification The function @code{x-parse-geometry} converts a standard X window geometry string to an alist that you can use as part of the argument to @code{make-frame}. The alist describes which parameters were specified in @var{geom}, and gives the values specified for them. Each element looks like @code{(@var{parameter} . @var{value})}. The possible @var{parameter} values are @code{left}, @code{top}, @code{width}, and @code{height}. For the size parameters, the value must be an integer. The position parameter names @code{left} and @code{top} are not totally accurate, because some values indicate the position of the right or bottom edges instead. The @var{value} possibilities for the position parameters are: an integer, a list @code{(+ @var{pos})}, or a list @code{(- @var{pos})}; as previously described (@pxref{Position Parameters}). Here is an example: @example (x-parse-geometry "35x70+0-0") @result{} ((height . 70) (width . 35) (top - 0) (left . 0)) @end example @end defun @node Terminal Parameters @section Terminal Parameters @cindex terminal parameters Each terminal has a list of associated parameters. These @dfn{terminal parameters} are mostly a convenient way of storage for terminal-local variables, but some terminal parameters have a special meaning. This section describes functions to read and change the parameter values of a terminal. They all accept as their argument either a terminal or a frame; the latter means use that frame's terminal. An argument of @code{nil} means the selected frame's terminal. @defun terminal-parameters &optional terminal This function returns an alist listing all the parameters of @var{terminal} and their values. @end defun @defun terminal-parameter terminal parameter This function returns the value of the parameter @var{parameter} (a symbol) of @var{terminal}. If @var{terminal} has no setting for @var{parameter}, this function returns @code{nil}. @end defun @defun set-terminal-parameter terminal parameter value This function sets the parameter @var{parameter} of @var{terminal} to the specified @var{value}, and returns the previous value of that parameter. @end defun Here's a list of a few terminal parameters that have a special meaning: @table @code @item background-mode The classification of the terminal's background color, either @code{light} or @code{dark}. @item normal-erase-is-backspace Value is either 1 or 0, depending on whether @code{normal-erase-is-backspace-mode} is turned on or off on this terminal. @xref{DEL Does Not Delete,,, emacs, The Emacs Manual}. @item terminal-initted After the terminal is initialized, this is set to the terminal-specific initialization function. @item tty-mode-set-strings When present, a list of strings containing escape sequences that Emacs will output while configuring a tty for rendering. Emacs emits these strings only when configuring a terminal: if you want to enable a mode on a terminal that is already active (for example, while in @code{tty-setup-hook}), explicitly output the necessary escape sequence using @code{send-string-to-terminal} in addition to adding the sequence to @code{tty-mode-set-strings}. @item tty-mode-reset-strings When present, a list of strings that undo the effects of the strings in @code{tty-mode-set-strings}. Emacs emits these strings when exiting, deleting a terminal, or suspending itself. @end table @node Frame Titles @section Frame Titles @cindex frame title Every frame has a @code{name} parameter; this serves as the default for the frame title which window systems typically display at the top of the frame. You can specify a name explicitly by setting the @code{name} frame property. Normally you don't specify the name explicitly, and Emacs computes the frame name automatically based on a template stored in the variable @code{frame-title-format}. Emacs recomputes the name each time the frame is redisplayed. @defvar frame-title-format This variable specifies how to compute a name for a frame when you have not explicitly specified one. The variable's value is actually a mode line construct, just like @code{mode-line-format}, except that the @samp{%c}, @samp{%C}, and @samp{%l} constructs are ignored. @xref{Mode Line Data}. @end defvar @defvar icon-title-format This variable specifies how to compute the name for an iconified frame, when you have not explicitly specified the frame title. This title appears in the icon itself. @end defvar @defvar multiple-frames This variable is set automatically by Emacs. Its value is @code{t} when there are two or more frames (not counting minibuffer-only frames or invisible frames). The default value of @code{frame-title-format} uses @code{multiple-frames} so as to put the buffer name in the frame title only when there is more than one frame. The value of this variable is not guaranteed to be accurate except while processing @code{frame-title-format} or @code{icon-title-format}. @end defvar @node Deleting Frames @section Deleting Frames @cindex deleting frames A @dfn{live frame} is one that has not been deleted. When a frame is deleted, it is removed from its terminal display, although it may continue to exist as a Lisp object until there are no more references to it. @deffn Command delete-frame &optional frame force @vindex delete-frame-functions @vindex after-delete-frame-functions This function deletes the frame @var{frame}. The argument @var{frame} must specify a live frame (see below) and defaults to the selected frame. It first deletes any child frame of @var{frame} (@pxref{Child Frames}) and any frame whose @code{delete-before} frame parameter (@pxref{Frame Interaction Parameters}) specifies @var{frame}. All such deletions are performed recursively; so this step makes sure that no other frames with @var{frame} as their ancestor will exist. Then, unless @var{frame} specifies a tooltip, this function runs the hook @code{delete-frame-functions} (each function getting one argument, @var{frame}) before actually killing the frame. After actually killing the frame and removing the frame from the frame list, @code{delete-frame} runs @code{after-delete-frame-functions}. Note that a frame cannot be deleted as long as its minibuffer serves as surrogate minibuffer for another frame (@pxref{Minibuffers and Frames}). Normally, you cannot delete a frame if all other frames are invisible, but if @var{force} is non-@code{nil}, then you are allowed to do so. @end deffn @defun frame-live-p frame This function returns non-@code{nil} if the frame @var{frame} has not been deleted. The possible non-@code{nil} return values are like those of @code{framep}. @xref{Frames}. @end defun Some window managers provide a command to delete a window. These work by sending a special message to the program that operates the window. When Emacs gets one of these commands, it generates a @code{delete-frame} event, whose normal definition is a command that calls the function @code{delete-frame}. @xref{Misc Events}. @deffn Command delete-other-frames &optional frame iconify This command deletes all frames on @var{frame}'s terminal, except @var{frame}. If @var{frame} uses another frame's minibuffer, that minibuffer frame is left untouched. The argument @var{frame} must specify a live frame and defaults to the selected frame. Internally, this command works by calling @code{delete-frame} with @var{force} @code{nil} for all frames that shall be deleted. This function does not delete any of @var{frame}'s child frames (@pxref{Child Frames}). If @var{frame} is a child frame, it deletes @var{frame}'s siblings only. With the prefix argument @var{iconify}, the frames are iconified rather than deleted. @end deffn @node Finding All Frames @section Finding All Frames @cindex frames, scanning all @defun frame-list This function returns a list of all the live frames, i.e., those that have not been deleted. It is analogous to @code{buffer-list} for buffers, and includes frames on all terminals. The list that you get is newly created, so modifying the list doesn't have any effect on the internals of Emacs. @end defun @defun visible-frame-list This function returns a list of just the currently visible frames. @xref{Visibility of Frames}. Frames on text terminals always count as visible, even though only the selected one is actually displayed. @end defun @defun frame-list-z-order &optional display This function returns a list of Emacs' frames, in Z (stacking) order (@pxref{Raising and Lowering}). The optional argument @var{display} specifies which display to poll. @var{display} should be either a frame or a display name (a string). If omitted or @code{nil}, that stands for the selected frame's display. It returns @code{nil} if @var{display} contains no Emacs frame. Frames are listed from topmost (first) to bottommost (last). As a special case, if @var{display} is non-@code{nil} and specifies a live frame, it returns the child frames of that frame in Z (stacking) order. This function is not meaningful on text terminals. @end defun @defun next-frame &optional frame minibuf This function lets you cycle conveniently through all the frames on a specific terminal from an arbitrary starting point. It returns the frame following @var{frame}, in the list of all live frames, on @var{frame}'s terminal. The argument @var{frame} must specify a live frame and defaults to the selected frame. It never returns a frame whose @code{no-other-frame} parameter (@pxref{Frame Interaction Parameters}) is non-@code{nil}. The second argument, @var{minibuf}, says which frames to consider when deciding what the next frame should be: @table @asis @item @code{nil} Consider all frames except minibuffer-only frames. @item @code{visible} Consider only visible frames. @item 0 Consider only visible or iconified frames. @item a window Consider only the frames using that particular window as their minibuffer window. @item anything else Consider all frames. @end table @end defun @defun previous-frame &optional frame minibuf Like @code{next-frame}, but cycles through all frames in the opposite direction. @end defun See also @code{next-window} and @code{previous-window}, in @ref{Cyclic Window Ordering}. @node Minibuffers and Frames @section Minibuffers and Frames Normally, each frame has its own minibuffer window at the bottom, which is used whenever that frame is selected. You can get that window with the function @code{minibuffer-window} (@pxref{Minibuffer Windows}). @cindex frame without a minibuffer @cindex surrogate minibuffer frame However, you can also create a frame without a minibuffer. Such a frame must use the minibuffer window of some other frame. That other frame will serve as @dfn{surrogate minibuffer frame} for this frame and cannot be deleted via @code{delete-frame} (@pxref{Deleting Frames}) as long as this frame is live. When you create the frame, you can explicitly specify its minibuffer window (in some other frame) with the @code{minibuffer} frame parameter (@pxref{Buffer Parameters}). If you don't, then the minibuffer is found in the frame which is the value of the variable @code{default-minibuffer-frame}. Its value should be a frame that does have a minibuffer. If you use a minibuffer-only frame, you might want that frame to raise when you enter the minibuffer. If so, set the variable @code{minibuffer-auto-raise} to @code{t}. @xref{Raising and Lowering}. @defvar default-minibuffer-frame This variable specifies the frame to use for the minibuffer window, by default. It does not affect existing frames. It is always local to the current terminal and cannot be buffer-local. @xref{Multiple Terminals}. @end defvar @node Input Focus @section Input Focus @cindex input focus @cindex selected frame At any time, one frame in Emacs is the @dfn{selected frame}. The selected window (@pxref{Selecting Windows}) always resides on the selected frame. When Emacs displays its frames on several terminals (@pxref{Multiple Terminals}), each terminal has its own selected frame. But only one of these is @emph{the} selected frame: it's the frame that belongs to the terminal from which the most recent input came. That is, when Emacs runs a command that came from a certain terminal, the selected frame is the one of that terminal. Since Emacs runs only a single command at any given time, it needs to consider only one selected frame at a time; this frame is what we call @dfn{the selected frame} in this manual. The display on which the selected frame is shown is the @dfn{selected frame's display}. @defun selected-frame This function returns the selected frame. @end defun Some window systems and window managers direct keyboard input to the window object that the mouse is in; others require explicit clicks or commands to @dfn{shift the focus} to various window objects. Either way, Emacs automatically keeps track of which frames have focus. To explicitly switch to a different frame from a Lisp function, call @code{select-frame-set-input-focus}. The plural ``frames'' in the previous paragraph is deliberate: while Emacs itself has only one selected frame, Emacs can have frames on many different terminals (recall that a connection to a window system counts as a terminal), and each terminal has its own idea of which frame has input focus. When you set the input focus to a frame, you set the focus for that frame's terminal, but frames on other terminals may still remain focused. Lisp programs can switch frames temporarily by calling the function @code{select-frame}. This does not alter the window system's concept of focus; rather, it escapes from the window manager's control until that control is somehow reasserted. When using a text terminal, only one frame can be displayed at a time on the terminal, so after a call to @code{select-frame}, the next redisplay actually displays the newly selected frame. This frame remains selected until a subsequent call to @code{select-frame}. Each frame on a text terminal has a number which appears in the mode line before the buffer name (@pxref{Mode Line Variables}). @defun select-frame-set-input-focus frame &optional norecord This function selects @var{frame}, raises it (should it happen to be obscured by other frames) and tries to give it the window system's focus. On a text terminal, the next redisplay displays the new frame on the entire terminal screen. The optional argument @var{norecord} has the same meaning as for @code{select-frame} (see below). The return value of this function is not significant. @end defun Ideally, the function described next should focus a frame without also raising it above other frames. Unfortunately, many window-systems or window managers may refuse to comply. @defun x-focus-frame frame &optional noactivate This function gives @var{frame} the focus of the X server without necessarily raising it. @var{frame} @code{nil} means use the selected frame. Under X, the optional argument @var{noactivate}, if non-@code{nil}, means to avoid making @var{frame}'s window-system window the ``active'' window which should insist a bit more on avoiding to raise @var{frame} above other frames. On MS-Windows the @var{noactivate} argument has no effect. However, if @var{frame} is a child frame (@pxref{Child Frames}), this function usually focuses @var{frame} without raising it above other child frames. If there is no window system support, this function does nothing. @end defun @deffn Command select-frame frame &optional norecord This function selects frame @var{frame}, temporarily disregarding the focus of the X server if any. The selection of @var{frame} lasts until the next time the user does something to select a different frame, or until the next time this function is called. (If you are using a window system, the previously selected frame may be restored as the selected frame after return to the command loop, because it still may have the window system's input focus.) The specified @var{frame} becomes the selected frame, and its terminal becomes the selected terminal. This function then calls @code{select-window} as a subroutine, passing the window selected within @var{frame} as its first argument and @var{norecord} as its second argument (hence, if @var{norecord} is non-@code{nil}, this avoids changing the order of recently selected windows and the buffer list). @xref{Selecting Windows}. This function returns @var{frame}, or @code{nil} if @var{frame} has been deleted. In general, you should never use @code{select-frame} in a way that could switch to a different terminal without switching back when you're done. @end deffn @cindex text-terminal focus notification Emacs cooperates with the window system by arranging to select frames as the server and window manager request. When a window system informs Emacs that one of its frames has been selected, Emacs internally generates a @dfn{focus-in} event. When an Emacs frame is displayed on a text-terminal emulator, such as @command{xterm}, which supports reporting of focus-change notification, the focus-in and focus-out events are available even for text-mode frames. Focus events are normally handled by @code{handle-focus-in}. @deffn Command handle-focus-in event This function handles focus-in events from window systems and terminals that support explicit focus notifications. It updates the per-frame focus flags that @code{frame-focus-state} queries and calls @code{after-focus-change-function}. In addition, it generates a @code{switch-frame} event in order to switch the Emacs notion of the selected frame to the frame most recently focused in some terminal. It's important to note that this switching of the Emacs selected frame to the most recently focused frame does not mean that other frames do not continue to have the focus in their respective terminals. Do not invoke this function yourself: instead, attach logic to @code{after-focus-change-function}. @end deffn @deffn Command handle-switch-frame frame This function handles a switch-frame event, which Emacs generates for itself upon focus notification or under various other circumstances involving an input event arriving at a different frame from the last event. Do not invoke this function yourself. @end deffn @defun redirect-frame-focus frame &optional focus-frame This function redirects focus from @var{frame} to @var{focus-frame}. This means that @var{focus-frame} will receive subsequent keystrokes and events intended for @var{frame}. After such an event, the value of @code{last-event-frame} will be @var{focus-frame}. Also, switch-frame events specifying @var{frame} will instead select @var{focus-frame}. If @var{focus-frame} is omitted or @code{nil}, that cancels any existing redirection for @var{frame}, which therefore once again receives its own events. One use of focus redirection is for frames that don't have minibuffers. These frames use minibuffers on other frames. Activating a minibuffer on another frame redirects focus to that frame. This puts the focus on the minibuffer's frame, where it belongs, even though the mouse remains in the frame that activated the minibuffer. Selecting a frame can also change focus redirections. Selecting frame @code{bar}, when @code{foo} had been selected, changes any redirections pointing to @code{foo} so that they point to @code{bar} instead. This allows focus redirection to work properly when the user switches from one frame to another using @code{select-window}. This means that a frame whose focus is redirected to itself is treated differently from a frame whose focus is not redirected. @code{select-frame} affects the former but not the latter. The redirection lasts until @code{redirect-frame-focus} is called to change it. @end defun @defun frame-focus-state frame This function retrieves the last known focus state of @var{frame}. It returns @code{nil} if the frame is known not to be focused, @code{t} if the frame is known to be focused, or @code{unknown} if Emacs does not know the focus state of the frame. (You may see this last state in TTY frames running on terminals that do not support explicit focus notifications.) @end defun @defvar after-focus-change-function This function is an extension point that code can use to receive a notification that focus has changed. This function is called with no arguments when Emacs notices that the set of focused frames may have changed. Code wanting to do something when frame focus changes should use @code{add-function} to add a function to this one, and in this added function, re-scan the set of focused frames, calling @code{frame-focus-state} to retrieve the last known focus state of each frame. Focus events are delivered asynchronously, and frame input focus according to an external system may not correspond to the notion of the Emacs selected frame. Multiple frames may appear to have input focus simultaneously due to focus event delivery differences, the presence of multiple Emacs terminals, and other factors, and code should be robust in the face of this situation. Depending on window system, focus events may also be delivered repeatedly and with different focus states before settling to the expected values. Code relying on focus notifications should ``debounce'' any user-visible updates arising from focus changes, perhaps by deferring work until redisplay. This function may be called in arbitrary contexts, including from inside @code{read-event}, so take the same care as you might when writing a process filter. @end defvar @defopt focus-follows-mouse This option informs Emacs whether and how the window manager transfers focus when you move the mouse pointer into a frame. It can have three meaningful values: @table @asis @item @code{nil} The default value @code{nil} should be used when your window manager follows a ``click-to-focus'' policy where you have to click the mouse inside of a frame in order for that frame to gain focus. @item @code{t} The value @code{t} should be used when your window manager has the focus automatically follow the position of the mouse pointer but a frame that gains focus is not raised automatically and may even remain occluded by other window-system windows. @item @code{auto-raise} The value @code{auto-raise} should be used when your window manager has the focus automatically follow the position of the mouse pointer and a frame that gains focus is raised automatically. @end table If this option is non-@code{nil}, Emacs moves the mouse pointer to the frame selected by @code{select-frame-set-input-focus}. That function is used by a number of commands like, for example, @code{other-frame} and @code{pop-to-buffer}. The distinction between the values @code{t} and @code{auto-raise} is not needed for ``normal'' frames because the window manager usually takes care of raising them. It is useful to automatically raise child frames via @code{mouse-autoselect-window} (@pxref{Mouse Window Auto-selection}). Note that this option does not distinguish ``sloppy'' focus (where the frame that previously had focus retains focus as long as the mouse pointer does not move into another window-system window) from ``strict'' focus (where a frame immediately loses focus when it's left by the mouse pointer). Neither does it recognize whether your window manager supports delayed focusing or auto-raising where you can explicitly specify the time until a new frame gets focus or is auto-raised. You can supply a ``focus follows mouse'' policy for individual Emacs windows by customizing the variable @code{mouse-autoselect-window} (@pxref{Mouse Window Auto-selection}). @end defopt @node Visibility of Frames @section Visibility of Frames @cindex visible frame @cindex invisible frame @cindex iconified frame @cindex minimized frame @cindex frame visibility A frame on a graphical display may be @dfn{visible}, @dfn{invisible}, or @dfn{iconified}. If it is visible, its contents are displayed in the usual manner. If it is iconified, its contents are not displayed, but there is a little icon somewhere to bring the frame back into view (some window managers refer to this state as @dfn{minimized} rather than @dfn{iconified}, but from Emacs' point of view they are the same thing). If a frame is invisible, it is not displayed at all. @cindex mapped frame @cindex unmapped frame The concept of visibility is strongly related to that of (un-)mapped frames. A frame (or, more precisely, its window-system window) is and becomes @dfn{mapped} when it is displayed for the first time and whenever it changes its state of visibility from @code{iconified} or @code{invisible} to @code{visible}. Conversely, a frame is and becomes @dfn{unmapped} whenever it changes its status from @code{visible} to @code{iconified} or @code{invisible}. Visibility is meaningless on text terminals, since only the selected frame is actually displayed in any case. @defun frame-visible-p frame This function returns the visibility status of frame @var{frame}. The value is @code{t} if @var{frame} is visible, @code{nil} if it is invisible, and @code{icon} if it is iconified. On a text terminal, all frames are considered visible for the purposes of this function, even though only one frame is displayed. @xref{Raising and Lowering}. @end defun @deffn Command iconify-frame &optional frame This function iconifies frame @var{frame}. If you omit @var{frame}, it iconifies the selected frame. This usually makes all child frames of @var{frame} (and their descendants) invisible (@pxref{Child Frames}). @end deffn @deffn Command make-frame-visible &optional frame This function makes frame @var{frame} visible. If you omit @var{frame}, it makes the selected frame visible. This does not raise the frame, but you can do that with @code{raise-frame} if you wish (@pxref{Raising and Lowering}). Making a frame visible usually makes all its child frames (and their descendants) visible as well (@pxref{Child Frames}). @end deffn @deffn Command make-frame-invisible &optional frame force This function makes frame @var{frame} invisible. If you omit @var{frame}, it makes the selected frame invisible. Usually, this makes all child frames of @var{frame} (and their descendants) invisible too (@pxref{Child Frames}). Unless @var{force} is non-@code{nil}, this function refuses to make @var{frame} invisible if all other frames are invisible. @end deffn The visibility status of a frame is also available as a frame parameter. You can read or change it as such. @xref{Management Parameters}. The user can also iconify and deiconify frames with the window manager. This happens below the level at which Emacs can exert any control, but Emacs does provide events that you can use to keep track of such changes. @xref{Misc Events}. @defun x-double-buffered-p &optional frame This function returns non-@code{nil} if @var{frame} is currently being rendered with double buffering. @var{frame} defaults to the selected frame. @end defun @node Raising and Lowering @section Raising, Lowering and Restacking Frames @cindex raising a frame @cindex lowering a frame @cindex restacking a frame @cindex frame stacking order @cindex frame Z-order @cindex Z-order Most window systems use a desktop metaphor. Part of this metaphor is the idea that system-level windows (representing, e.g., Emacs frames) are stacked in a notional third dimension perpendicular to the screen surface. The order induced by stacking is total and usually referred to as stacking (or Z-) order. Where the areas of two windows overlap, the one higher up in that order will (partially) cover the one underneath. You can @dfn{raise} a frame to the top of that order or @dfn{lower} a frame to its bottom by using the functions @code{raise-frame} and @code{lower-frame}. You can @dfn{restack} a frame directly above or below another frame using the function @code{frame-restack}. Note that all functions described below will respect the adherence of frames (and all other window-system windows) to their respective z-group (@pxref{Position Parameters}). For example, you usually cannot lower a frame below that of the desktop window and you cannot raise a frame whose @code{z-group} parameter is @code{nil} above the window-system's taskbar or tooltip window. @deffn Command raise-frame &optional frame This function raises frame @var{frame} (default, the selected frame) above all other frames belonging to the same or a lower z-group as @var{frame}. If @var{frame} is invisible or iconified, this makes it visible. If @var{frame} is a child frame (@pxref{Child Frames}), this raises @var{frame} above all other child frames of its parent. @end deffn @deffn Command lower-frame &optional frame This function lowers frame @var{frame} (default, the selected frame) below all other frames belonging to the same or a higher z-group as @var{frame}. If @var{frame} is a child frame (@pxref{Child Frames}), this lowers @var{frame} below all other child frames of its parent. @end deffn @defun frame-restack frame1 frame2 &optional above This function restacks @var{frame1} below @var{frame2}. This implies that if both frames are visible and their display areas overlap, @var{frame2} will (partially) obscure @var{frame1}. If the optional third argument @var{above} is non-@code{nil}, this function restacks @var{frame1} above @var{frame2}. This means that if both frames are visible and their display areas overlap, @var{frame1} will (partially) obscure @var{frame2}. Technically, this function may be thought of as an atomic action performed in two steps: The first step removes @var{frame1}'s window-system window from the display. The second step reinserts @var{frame1}'s window into the display below (above if @var{above} is true) that of @var{frame2}. Hence the position of @var{frame2} in its display's Z (stacking) order relative to all other frames excluding @var{frame1} remains unaltered. Some window managers may refuse to restack windows. @end defun Note that the effect of restacking will only hold as long as neither of the involved frames is iconified or made invisible. You can use the @code{z-group} (@pxref{Position Parameters}) frame parameter to add a frame to a group of frames permanently shown above or below other frames. As long as a frame belongs to one of these groups, restacking it will only affect its relative stacking position within that group. The effect of restacking frames belonging to different z-groups is undefined. You can list frames in their current stacking order with the function @code{frame-list-z-order} (@pxref{Finding All Frames}). @defopt minibuffer-auto-raise If this is non-@code{nil}, activation of the minibuffer raises the frame that the minibuffer window is in. @end defopt On window systems, you can also enable auto-raising (on frame selection) or auto-lowering (on frame deselection) using frame parameters. @xref{Management Parameters}. @cindex top frame The concept of raising and lowering frames also applies to text terminal frames. On each text terminal, only the top frame is displayed at any one time. @defun tty-top-frame &optional terminal This function returns the top frame on @var{terminal}. @var{terminal} should be a terminal object, a frame (meaning that frame's terminal), or @code{nil} (meaning the selected frame's terminal). If it does not refer to a text terminal, the return value is @code{nil}. @end defun @node Frame Configurations @section Frame Configurations @cindex frame configuration A @dfn{frame configuration} records the current arrangement of frames, all their properties, and the window configuration of each one. (@xref{Window Configurations}.) @defun current-frame-configuration This function returns a frame configuration list that describes the current arrangement of frames and their contents. @end defun @defun set-frame-configuration configuration &optional nodelete This function restores the state of frames described in @var{configuration}. However, this function does not restore deleted frames. Ordinarily, this function deletes all existing frames not listed in @var{configuration}. But if @var{nodelete} is non-@code{nil}, the unwanted frames are iconified instead. @end defun @node Child Frames @section Child Frames @cindex child frames @cindex parent frames Child frames are objects halfway between windows (@pxref{Windows}) and ``normal'' frames. Like windows, they are attached to an owning frame. Unlike windows, they may overlap each other---changing the size or position of one child frame does not change the size or position of any of its sibling child frames. By design, operations to make or modify child frames are implemented with the help of frame parameters (@pxref{Frame Parameters}) without any specialized functions or customizable variables. Note that child frames are meaningful on graphical terminals only. To create a new child frame or to convert a normal frame into a child frame, set that frame's @code{parent-frame} parameter (@pxref{Frame Interaction Parameters}) to that of an already existing frame. The frame specified by that parameter will then be the frame's parent frame as long as the parameter is not changed or reset. Technically, this makes the child frame's window-system window a child window of the parent frame's window-system window. @cindex reparent frame @cindex nest frame The @code{parent-frame} parameter can be changed at any time. Setting it to another frame @dfn{reparents} the child frame. Setting it to another child frame makes the frame a @dfn{nested} child frame. Setting it to @code{nil} restores the frame's status as a top-level frame---a frame whose window-system window is a child of its display's root window.@footnote{On Haiku, child frames are only visible when a parent frame is active, owing to a limitation of the Haiku windowing system. Owing to the same limitation, child frames are only guaranteed to appear above their top-level parent; that is to say, the top-most frame in the hierarchy, which does not have a parent frame.} Since child frames can be arbitrarily nested, a frame can be both a child and a parent frame. Also, the relative roles of child and parent frame may be reversed at any time (though it's usually a good idea to keep the size of a child frame sufficiently smaller than that of its parent). An error will be signaled for the attempt to make a frame an ancestor of itself. Most window-systems clip a child frame at the native edges (@pxref{Frame Geometry}) of its parent frame---everything outside these edges is usually invisible. A child frame's @code{left} and @code{top} parameters specify a position relative to the top-left corner of its parent's native frame. When the parent frame is resized, this position remains conceptually unaltered. NS builds do not clip child frames at the parent frame's edges, allowing them to be positioned so they do not obscure the parent frame while still being visible themselves. Usually, moving a parent frame moves along all its child frames and their descendants as well, keeping their relative positions unaltered. Note that the hook @code{move-frame-functions} (@pxref{Frame Position}) is run for a child frame only when the position of the child frame relative to its parent frame changes. When a parent frame is resized, its child frames conceptually retain their previous sizes and their positions relative to the left upper corner of the parent. This means that a child frame may become (partially) invisible when its parent frame shrinks. The parameter @code{keep-ratio} (@pxref{Frame Interaction Parameters}) can be used to resize and reposition a child frame proportionally whenever its parent frame is resized. This may avoid obscuring parts of a frame when its parent frame is shrunk. A visible child frame always appears on top of its parent frame thus obscuring parts of it, except on NS builds where it may be positioned beneath the parent. This is comparable to the window-system window of a top-level frame which also always appears on top of its parent window---the desktop's root window. When a parent frame is iconified or made invisible (@pxref{Visibility of Frames}), its child frames are made invisible. When a parent frame is deiconified or made visible, its child frames are made visible. When a parent frame is about to be deleted (@pxref{Deleting Frames}), its child frames are recursively deleted before it. There is one exception to this rule: When the child frame serves as a surrogate minibuffer frame (@pxref{Minibuffers and Frames}) for another frame, it is retained until the parent frame has been deleted. If, at this time, no remaining frame uses the child frame as its minibuffer frame, Emacs will try to delete the child frame too. If that deletion fails for whatever reason, the child frame is made a top-level frame. Whether a child frame can have a menu or tool bar is window-system or window manager dependent. Most window-systems explicitly disallow menu bars for child frames. It seems advisable to disable both, menu and tool bars, via the frame's initial parameters settings. Usually, child frames do not exhibit window manager decorations like a title bar or external borders (@pxref{Frame Geometry}). When the child frame does not show a menu or tool bar, any other of the frame's borders (@pxref{Layout Parameters}) can be used instead of the external borders. In particular, under X (but not when building with GTK+), the frame's outer border can be used. On MS-Windows, specifying a non-zero outer border width will show a one-pixel wide external border. Under all window-systems, the internal border can be used. In either case, it's advisable to disable a child frame's window manager decorations with the @code{undecorated} frame parameter (@pxref{Management Parameters}). To resize or move an undecorated child frame with the mouse, special frame parameters (@pxref{Mouse Dragging Parameters}) have to be used. The internal border of a child frame, if present, can be used to resize the frame with the mouse, provided that frame has a non-@code{nil} @code{drag-internal-border} parameter. If set, the @code{snap-width} parameter indicates the number of pixels where the frame @dfn{snaps} at the respective edge or corner of its parent frame. There are two ways to drag an entire child frame with the mouse: The @code{drag-with-mode-line} parameter, if non-@code{nil}, allows to drag a frame without minibuffer window (@pxref{Minibuffer Windows}) via the mode line area of its bottommost window. The @code{drag-with-header-line} parameter, if non-@code{nil}, allows to drag the frame via the header line area of its topmost window. In order to give a child frame a draggable header or mode line, the window parameters @code{mode-line-format} and @code{header-line-format} are handy (@pxref{Window Parameters}). These allow to remove an unwanted mode line (when @code{drag-with-header-line} is chosen) and to remove mouse-sensitive areas which might interfere with frame dragging. When the user drags a frame with a mouse and overshoots, it's easy to drag a frame out of the screen area of its parent. Retrieving such a frame can be hairy once the mouse button has been released. To prevent such a situation, it is advisable to set the frame's @code{top-visible} or @code{bottom-visible} parameter (@pxref{Mouse Dragging Parameters}). Set the @code{top-visible} parameter of a child frame to a number when you intend to allow the user dragging that frame by its header line. Setting @code{top-visible} to a number inhibits dragging the top edge of the child frame above the top edge of its parent. Set the @code{bottom-visible} parameter to a number when you intend to drag that frame via its mode line; this inhibits dragging the bottom edge of the child frame beneath the bottom edge of its parent. In either case, that number also specifies width and height (in pixels) of the area of the child frame that remains visible during dragging. When a child frame is used for displaying a buffer via @code{display-buffer-in-child-frame} (@pxref{Buffer Display Action Functions}), the frame's @code{auto-hide-function} parameter (@pxref{Frame Interaction Parameters}) can be set to a function, in order to appropriately deal with the frame when the window displaying the buffer shall be quit. When a child frame is used during minibuffer interaction, for example, to display completions in a separate window, the @code{minibuffer-exit} parameter (@pxref{Frame Interaction Parameters}) is useful in order to deal with the frame when the minibuffer is exited. The behavior of child frames deviates from that of top-level frames in a number of other ways as well. Here we sketch a few of them: @itemize @bullet @item The semantics of maximizing and iconifying child frames is highly window-system dependent. As a rule, applications should never invoke these operations on child frames. By default, invoking @code{iconify-frame} on a child frame will try to iconify the top-level frame corresponding to that child frame instead. To obtain a different behavior, users may customize the option @code{iconify-child-frame} described below. @item Raising, lowering and restacking child frames (@pxref{Raising and Lowering}) or changing the @code{z-group} (@pxref{Position Parameters}) of a child frame changes only the stacking order of child frames with the same parent. @item Many window-systems are not able to change the opacity (@pxref{Font and Color Parameters}) of child frames. @item Transferring focus from a child frame to an ancestor that is not its parent by clicking with the mouse in a visible part of that ancestor's window may fail with some window-systems. You may have to click into the direct parent's window-system window first. @item Window managers might not bother to extend their focus follows mouse policy to child frames. Customizing @code{mouse-autoselect-window} can help in this regard (@pxref{Mouse Window Auto-selection}). @item Dropping (@pxref{Drag and Drop}) on child frames is not guaranteed to work on all window-systems. Some will drop the object on the parent frame or on some ancestor instead. @end itemize The following two functions can be useful when working with child and parent frames: @defun frame-parent &optional frame This function returns the parent frame of @var{frame}. The parent frame of @var{frame} is the Emacs frame whose window-system window is the parent window of @var{frame}'s window-system window. If such a frame exists, @var{frame} is considered a child frame of that frame. This function returns @code{nil} if @var{frame} has no parent frame. @end defun @defun frame-ancestor-p ancestor descendant This functions returns non-@code{nil} if @var{ancestor} is an ancestor of @var{descendant}. @var{ancestor} is an ancestor of @var{descendant} when it is either @var{descendant}'s parent frame or it is an ancestor of @var{descendant}'s parent frame. Both, @var{ancestor} and @var{descendant} must specify live frames. @end defun Note also the function @code{window-largest-empty-rectangle} (@pxref{Coordinates and Windows}) which can be used to inscribe a child frame in the largest empty area of an existing window. This can be useful to avoid that a child frame obscures any text shown in that window. Customizing the following option can be useful to tweak the behavior of @code{iconify-frame} for child frames. @defopt iconify-child-frame This option tells Emacs how to proceed when it is asked to iconify a child frame. If it is @code{nil}, @code{iconify-frame} will do nothing when invoked on a child frame. If it is @code{iconify-top-level}, Emacs will try to iconify the top-level frame that is the ancestor of this child frame instead. If it is @code{make-invisible}, Emacs will try to make this child frame invisible instead of iconifying it. Any other value means to try iconifying the child frame. Since such an attempt may not be honored by all window managers and can even lead to making the child frame unresponsive to user actions, the default is to iconify the top level frame instead. @end defopt @node Mouse Tracking @section Mouse Tracking @cindex mouse tracking @c @cindex tracking the mouse Duplicates track-mouse Sometimes it is useful to @dfn{track} the mouse, which means to display something to indicate where the mouse is and move the indicator as the mouse moves. For efficient mouse tracking, you need a way to wait until the mouse actually moves. The convenient way to track the mouse is to ask for events to represent mouse motion. Then you can wait for motion by waiting for an event. In addition, you can easily handle any other sorts of events that may occur. That is useful, because normally you don't want to track the mouse forever---only until some other event, such as the release of a button. @defmac track-mouse body@dots{} This macro executes @var{body}, with generation of mouse motion events enabled. Typically, @var{body} would use @code{read-event} to read the motion events and modify the display accordingly. @xref{Motion Events}, for the format of mouse motion events. The value of @code{track-mouse} is that of the last form in @var{body}. You should design @var{body} to return when it sees the up-event that indicates the release of the button, or whatever kind of event means it is time to stop tracking. The @code{track-mouse} form causes Emacs to generate mouse motion events by binding the variable @code{track-mouse} to a non-@code{nil} value. If that variable has the special value @code{dragging}, it additionally instructs the display engine to refrain from changing the shape of the mouse pointer. This is desirable in Lisp programs that require mouse dragging across large portions of Emacs display, which might otherwise cause the mouse pointer to change its shape according to the display portion it hovers on (@pxref{Pointer Shape}). Therefore, Lisp programs that need the mouse pointer to retain its original shape during dragging should bind @code{track-mouse} to the value @code{dragging} at the beginning of their @var{body}. @end defmac The usual purpose of tracking mouse motion is to indicate on the screen the consequences of pushing or releasing a button at the current position. In many cases, you can avoid the need to track the mouse by using the @code{mouse-face} text property (@pxref{Special Properties}). That works at a much lower level and runs more smoothly than Lisp-level mouse tracking. @ignore @c These are not implemented yet. These functions change the screen appearance instantaneously. The effect is transient, only until the next ordinary Emacs redisplay. That is OK for mouse tracking, since it doesn't make sense for mouse tracking to change the text, and the body of @code{track-mouse} normally reads the events itself and does not do redisplay. @defun x-contour-region window beg end This function draws lines to make a box around the text from @var{beg} to @var{end}, in window @var{window}. @end defun @defun x-uncontour-region window beg end This function erases the lines that would make a box around the text from @var{beg} to @var{end}, in window @var{window}. Use it to remove a contour that you previously made by calling @code{x-contour-region}. @end defun @defun x-draw-rectangle frame left top right bottom This function draws a hollow rectangle on frame @var{frame} with the specified edge coordinates, all measured in pixels from the inside top left corner. It uses the cursor color, the one used for indicating the location of point. @end defun @defun x-erase-rectangle frame left top right bottom This function erases a hollow rectangle on frame @var{frame} with the specified edge coordinates, all measured in pixels from the inside top left corner. Erasure means redrawing the text and background that normally belong in the specified rectangle. @end defun @end ignore @node Mouse Position @section Mouse Position @cindex mouse position @cindex position of mouse The functions @code{mouse-position} and @code{set-mouse-position} give access to the current position of the mouse. @defun mouse-position This function returns a description of the position of the mouse. The value looks like @code{(@var{frame} @var{x} . @var{y})}, where @var{x} and @var{y} are integers giving the (possibly rounded) position in multiples of the default character size of @var{frame} (@pxref{Frame Font}) relative to the native position of @var{frame} (@pxref{Frame Geometry}). @end defun @defvar mouse-position-function If non-@code{nil}, the value of this variable is a function for @code{mouse-position} to call. @code{mouse-position} calls this function just before returning, with its normal return value as the sole argument, and it returns whatever this function returns to it. This abnormal hook exists for the benefit of packages like @file{xt-mouse.el} that need to do mouse handling at the Lisp level. @end defvar @defvar tty-menu-calls-mouse-position-function If non-@code{nil}, TTY menus will call @code{mouse-position-function} as described above. This exists for cases where @code{mouse-position-function} is not safe to be called by the TTY menus, such as if it could trigger redisplay. @end defvar @defun set-mouse-position frame x y This function @dfn{warps the mouse} to position @var{x}, @var{y} in frame @var{frame}. The arguments @var{x} and @var{y} are integers, giving the position in multiples of the default character size of @var{frame} (@pxref{Frame Font}) relative to the native position of @var{frame} (@pxref{Frame Geometry}). The resulting mouse position is constrained to the native frame of @var{frame}. If @var{frame} is not visible, this function does nothing. The return value is not significant. @end defun @defun mouse-pixel-position This function is like @code{mouse-position} except that it returns coordinates in units of pixels rather than units of characters. @end defun @defun set-mouse-pixel-position frame x y This function warps the mouse like @code{set-mouse-position} except that @var{x} and @var{y} are in units of pixels rather than units of characters. The resulting mouse position is not constrained to the native frame of @var{frame}. If @var{frame} is not visible, this function does nothing. The return value is not significant. @end defun On a graphical terminal the following two functions allow the absolute position of the mouse cursor to be retrieved and set. @defun mouse-absolute-pixel-position This function returns a cons cell (@var{x} . @var{y}) of the coordinates of the mouse cursor position in pixels, relative to a position (0, 0) of the selected frame's display. @end defun @defun set-mouse-absolute-pixel-position x y This function moves the mouse cursor to the position (@var{x}, @var{y}). The coordinates @var{x} and @var{y} are interpreted in pixels relative to a position (0, 0) of the selected frame's display. @end defun The following function can tell whether the mouse cursor is currently visible on a frame: @defun frame-pointer-visible-p &optional frame This predicate function returns non-@code{nil} if the mouse pointer displayed on @var{frame} is visible; otherwise it returns @code{nil}. @var{frame} omitted or @code{nil} means the selected frame. This is useful when @code{make-pointer-invisible} is set to @code{t}: it allows you to know if the pointer has been hidden. @xref{Mouse Avoidance,,,emacs, The Emacs Manual}. @end defun @need 3000 @node Pop-Up Menus @section Pop-Up Menus @cindex menus, popup A Lisp program can pop up a menu so that the user can choose an alternative with the mouse. On a text terminal, if the mouse is not available, the user can choose an alternative using the keyboard motion keys---@kbd{C-n}, @kbd{C-p}, or up- and down-arrow keys. @defun x-popup-menu position menu This function displays a pop-up menu and returns an indication of what selection the user makes. The argument @var{position} specifies where on the screen to put the top left corner of the menu. It can be either a mouse button event (which says to put the menu where the user actuated the button) or a list of this form: @example ((@var{xoffset} @var{yoffset}) @var{window}) @end example @noindent where @var{xoffset} and @var{yoffset} are coordinates, measured in pixels, counting from the top left corner of @var{window}. @var{window} may be a window or a frame. If @var{position} is @code{t}, it means to use the current mouse position (or the top-left corner of the frame if the mouse is not available on a text terminal). If @var{position} is @code{nil}, it means to precompute the key binding equivalents for the keymaps specified in @var{menu}, without actually displaying or popping up the menu. The argument @var{menu} says what to display in the menu. It can be a keymap or a list of keymaps (@pxref{Menu Keymaps}). In this case, the return value is the list of events corresponding to the user's choice. This list has more than one element if the choice occurred in a submenu. (Note that @code{x-popup-menu} does not actually execute the command bound to that sequence of events.) On text terminals and toolkits that support menu titles, the title is taken from the prompt string of @var{menu} if @var{menu} is a keymap, or from the prompt string of the first keymap in @var{menu} if it is a list of keymaps (@pxref{Defining Menus}). Alternatively, @var{menu} can have the following form: @example (@var{title} @var{pane1} @var{pane2}...) @end example @noindent where each pane is a list of form @example (@var{title} @var{item1} @var{item2}...) @end example Each @var{item} should be a cons cell, @code{(@var{line} . @var{value})}, where @var{line} is a string and @var{value} is the value to return if that @var{line} is chosen. Unlike in a menu keymap, a @code{nil} @var{value} does not make the menu item non-selectable. Alternatively, each @var{item} can be a string rather than a cons cell; this makes a non-selectable menu item. If the user gets rid of the menu without making a valid choice, for instance by clicking the mouse away from a valid choice or by typing @kbd{C-g}, then this normally results in a quit and @code{x-popup-menu} does not return. But if @var{position} is a mouse button event (indicating that the user invoked the menu with the mouse) then no quit occurs and @code{x-popup-menu} returns @code{nil}. @end defun @strong{Usage note:} Don't use @code{x-popup-menu} to display a menu if you could do the job with a prefix key defined with a menu keymap. If you use a menu keymap to implement a menu, @kbd{C-h c} and @kbd{C-h a} can see the individual items in that menu and provide help for them. If instead you implement the menu by defining a command that calls @code{x-popup-menu}, the help facilities cannot know what happens inside that command, so they cannot give any help for the menu's items. The menu bar mechanism, which lets you switch between submenus by moving the mouse, cannot look within the definition of a command to see that it calls @code{x-popup-menu}. Therefore, if you try to implement a submenu using @code{x-popup-menu}, it cannot work with the menu bar in an integrated fashion. This is why all menu bar submenus are implemented with menu keymaps within the parent menu, and never with @code{x-popup-menu}. @xref{Menu Bar}. If you want a menu bar submenu to have contents that vary, you should still use a menu keymap to implement it. To make the contents vary, add a hook function to @code{menu-bar-update-hook} to update the contents of the menu keymap as necessary. @defvar x-pre-popup-menu-hook A normal hook run immediately before a pop-up menu is displayed, either directly by calling @code{x-popup-menu}, or through a menu keymap. It won't be called if @code{x-popup-menu} returns for some other reason without displaying a pop-up menu. @end defvar @node Dialog Boxes @section Dialog Boxes @cindex dialog boxes A dialog box is a variant of a pop-up menu---it looks a little different, it always appears in the center of a frame, and it has just one level and one or more buttons. The main use of dialog boxes is for asking questions that the user can answer with ``yes'', ``no'', and a few other alternatives. With a single button, they can also force the user to acknowledge important information. The functions @code{y-or-n-p} and @code{yes-or-no-p} use dialog boxes instead of the keyboard, when called from commands invoked by mouse clicks. @defun x-popup-dialog position contents &optional header This function displays a pop-up dialog box and returns an indication of what selection the user makes. The argument @var{contents} specifies the alternatives to offer; it has this format: @example (@var{title} (@var{string} . @var{value})@dots{}) @end example @noindent which looks like the list that specifies a single pane for @code{x-popup-menu}. The return value is @var{value} from the chosen alternative. As for @code{x-popup-menu}, an element of the list may be just a string instead of a cons cell @code{(@var{string} . @var{value})}. That makes a box that cannot be selected. If @code{nil} appears in the list, it separates the left-hand items from the right-hand items; items that precede the @code{nil} appear on the left, and items that follow the @code{nil} appear on the right. If you don't include a @code{nil} in the list, then approximately half the items appear on each side. Dialog boxes always appear in the center of a frame; the argument @var{position} specifies which frame. The possible values are as in @code{x-popup-menu}, but the precise coordinates or the individual window don't matter; only the frame matters. If @var{header} is non-@code{nil}, the frame title for the box is @samp{Information}, otherwise it is @samp{Question}. The former is used for @code{message-box} (@pxref{message-box}). (On text terminals, the box title is not displayed.) In some configurations, Emacs cannot display a real dialog box; so instead it displays the same items in a pop-up menu in the center of the frame. If the user gets rid of the dialog box without making a valid choice, for instance using the window manager, then this produces a quit and @code{x-popup-dialog} does not return. @end defun @node Pointer Shape @section Pointer Shape @cindex pointer shape @cindex mouse pointer shape You can specify the mouse pointer style for particular text or images using the @code{pointer} text property, and for images with the @code{:pointer} and @code{:map} image properties. The values you can use in these properties are in the table below. The actual shapes may vary between systems; the descriptions are examples. @table @code @item text @itemx nil The usual mouse pointer style used over text (an ``I''-like shape). @item arrow @itemx vdrag @itemx modeline An arrow that points north-west. @item hand A hand that points upwards. @item hdrag A right-left arrow. @item nhdrag An up-down arrow. @item hourglass A rotating ring. @end table Over void parts of the window (parts that do not correspond to any of the buffer contents), the mouse pointer usually uses the @code{arrow} style, but you can specify a different style (one of those above) by setting @code{void-text-area-pointer}. @defopt void-text-area-pointer This variable specifies the mouse pointer style for void text areas. These include the areas after the end of a line or below the last line in the buffer. The default is to use the @code{arrow} (non-text) pointer style. @end defopt When using X, you can specify what the @code{text} pointer style really looks like by setting the variable @code{x-pointer-shape}. @defvar x-pointer-shape This variable specifies the pointer shape to use ordinarily in the Emacs frame, for the @code{text} pointer style. @end defvar @defvar x-sensitive-text-pointer-shape This variable specifies the pointer shape to use when the mouse is over mouse-sensitive text. @end defvar These variables affect newly created frames. They do not normally affect existing frames; however, if you set the mouse color of a frame, that also installs the current value of those two variables. @xref{Font and Color Parameters}. The values you can use, to specify either of these pointer shapes, are defined in the file @file{lisp/term/x-win.el}. Use @kbd{M-x apropos @key{RET} x-pointer @key{RET}} to see a list of them. @node Window System Selections @section Window System Selections @cindex selection (for window systems) @cindex clipboard @cindex primary selection @cindex secondary selection In window systems, such as X, data can be transferred between different applications by means of @dfn{selections}. X defines an arbitrary number of @dfn{selection types}, each of which can store its own data; however, only three are commonly used: the @dfn{clipboard}, @dfn{primary selection}, and @dfn{secondary selection}. Other window systems support only the clipboard. @xref{Cut and Paste,, Cut and Paste, emacs, The GNU Emacs Manual}, for Emacs commands that make use of these selections. This section documents the low-level functions for reading and setting window-system selections. @deffn Command gui-set-selection type data This function sets a window-system selection. It takes two arguments: a selection type @var{type}, and the value to assign to it, @var{data}. @var{type} should be a symbol; it is usually one of @code{PRIMARY}, @code{SECONDARY} or @code{CLIPBOARD}. These are symbols with upper-case names, in accord with X Window System conventions. If @var{type} is @code{nil}, that stands for @code{PRIMARY}. If @var{data} is @code{nil}, it means to clear out the selection. Otherwise, @var{data} may be a string, a symbol, an integer (or a cons of two integers or list of two integers), an overlay, or a cons of two markers pointing to the same buffer. An overlay or a pair of markers stands for text in the overlay or between the markers. The argument @var{data} may also be a vector of valid non-vector selection values. This function returns @var{data}. @end deffn @defun gui-get-selection &optional type data-type This function accesses selections set up by Emacs or by other programs. It takes two optional arguments, @var{type} and @var{data-type}. The default for @var{type}, the selection type, is @code{PRIMARY}. The @var{data-type} argument specifies the form of data conversion to use, to convert the raw data obtained from another program into Lisp data. Meaningful values include @code{TEXT}, @code{STRING}, @code{UTF8_STRING}, @code{TARGETS}, @code{LENGTH}, @code{DELETE}, @code{FILE_NAME}, @code{CHARACTER_POSITION}, @code{NAME}, @code{LINE_NUMBER}, @code{COLUMN_NUMBER}, @code{OWNER_OS}, @code{HOST_NAME}, @code{USER}, @code{CLASS}, @code{ATOM}, and @code{INTEGER}. (These are symbols with upper-case names in accord with X conventions.) The default for @var{data-type} is @code{STRING}. Window systems other than X usually support only a small subset of these types, in addition to @code{STRING}. @end defun @defopt selection-coding-system This variable specifies the coding system to use when reading and writing selections or the clipboard. @xref{Coding Systems}. The default is @code{compound-text-with-extensions}, which converts to the text representation that X11 normally uses. @end defopt @cindex clipboard support (for MS-Windows) When Emacs runs on MS-Windows, it does not implement X selections in general, but it does support the clipboard. @code{gui-get-selection} and @code{gui-set-selection} on MS-Windows support the text data type only; if the clipboard holds other types of data, Emacs treats the clipboard as empty. The supported data type is @code{STRING}. For backward compatibility, there are obsolete aliases @code{x-get-selection} and @code{x-set-selection}, which were the names of @code{gui-get-selection} and @code{gui-set-selection} before Emacs 25.1. @node Yanking Media @section Yanking Media If you choose, for instance, ``Copy Image'' in a web browser, that image is put onto the clipboard, and Emacs can access it via @code{gui-get-selection}. But in general, inserting image data into an arbitrary buffer isn't very useful---you can't really do much with it by default. So Emacs has a system to let modes register handlers for these ``complicated'' selections. @defun yank-media-handler types handler @var{types} can be a @acronym{MIME} media type symbol, a regexp to match these, or a list of these symbols and regexps. For instance: @example (yank-media-handler 'text/html #'my-html-handler) (yank-media-handler "image/.*" #'my-image-handler) @end example A mode can register as many handlers as required. The @var{handler} function is called with two parameters: The @acronym{MIME} media type symbol and the data (as a string). The handler should then insert the object into the buffer, or save it, or do whatever is appropriate for the mode. @end defun The @code{yank-media} command will consult the registered handlers in the current buffer, compare that with the available media types on the clipboard, and then pass on the matching selection to the handler (if any). If there's more than one matching selection, the user is queried first. The @code{yank-media-types} command can be used to explore the clipboard/primary selection. It lists all the media types that are currently available, and can be handy when creating handlers---to see what data is actually available. Some applications put a surprising amount of different data types on the clipboard. @node Drag and Drop @section Drag and Drop @cindex drag and drop @vindex x-dnd-test-function @vindex x-dnd-known-types When a user drags something from another application over Emacs, that other application expects Emacs to tell it if Emacs can handle the data that is dragged. The variable @code{x-dnd-test-function} is used by Emacs to determine what to reply. The default value is @code{x-dnd-default-test-function} which accepts drops if the type of the data to be dropped is present in @code{x-dnd-known-types}. You can customize @code{x-dnd-test-function} and/or @code{x-dnd-known-types} if you want Emacs to accept or reject drops based on some other criteria. @vindex x-dnd-types-alist If you want to change the way Emacs handles drop of different types or add a new type, customize @code{x-dnd-types-alist}. This requires detailed knowledge of what types other applications use for drag and drop. @vindex dnd-protocol-alist @vindex browse-url-handlers @vindex browse-url-default-handlers When an URL is dropped on Emacs it may be a file, but it may also be another URL type (https, etc.). Emacs first checks @code{dnd-protocol-alist} to determine what to do with the URL@. If there is no match there, Emacs looks for a match in @code{browse-url-handlers} and @code{browse-url-default-handlers}. If still no match has been found, the text for the URL is inserted. If you want to alter Emacs behavior, you can customize these variables. @node Color Names @section Color Names @cindex color names @cindex specify color @cindex numerical RGB color specification A color name is text (usually in a string) that specifies a color. Symbolic names such as @samp{black}, @samp{white}, @samp{red}, etc., are allowed; use @kbd{M-x list-colors-display} to see a list of defined names. You can also specify colors numerically in forms such as @samp{#@var{rgb}} and @samp{RGB:@var{r}/@var{g}/@var{b}}, where @var{r} specifies the red level, @var{g} specifies the green level, and @var{b} specifies the blue level. You can use either one, two, three, or four hex digits for @var{r}; then you must use the same number of hex digits for all @var{g} and @var{b} as well, making either 3, 6, 9 or 12 hex digits in all. (See the documentation of the X Window System for more details about numerical RGB specification of colors.) These functions provide a way to determine which color names are valid, and what they look like. In some cases, the value depends on the @dfn{selected frame}, as described below; see @ref{Input Focus}, for the meaning of the term ``selected frame''. To read user input of color names with completion, use @code{read-color} (@pxref{High-Level Completion, read-color}). @defun color-defined-p color &optional frame This function reports whether a color name is meaningful. It returns @code{t} if so; otherwise, @code{nil}. The argument @var{frame} says which frame's display to ask about; if @var{frame} is omitted or @code{nil}, the selected frame is used. Note that this does not tell you whether the display you are using really supports that color. When using X, you can ask for any defined color on any kind of display, and you will get some result---typically, the closest it can do. To determine whether a frame can really display a certain color, use @code{color-supported-p} (see below). @findex x-color-defined-p This function used to be called @code{x-color-defined-p}, and that name is still supported as an alias. @end defun @defun defined-colors &optional frame This function returns a list of the color names that are defined and supported on frame @var{frame} (default, the selected frame). If @var{frame} does not support colors, the value is @code{nil}. @findex x-defined-colors This function used to be called @code{x-defined-colors}, and that name is still supported as an alias. @end defun @defun color-supported-p color &optional frame background-p This returns @code{t} if @var{frame} can really display the color @var{color} (or at least something close to it). If @var{frame} is omitted or @code{nil}, the question applies to the selected frame. Some terminals support a different set of colors for foreground and background. If @var{background-p} is non-@code{nil}, that means you are asking whether @var{color} can be used as a background; otherwise you are asking whether it can be used as a foreground. The argument @var{color} must be a valid color name. @end defun @defun color-gray-p color &optional frame This returns @code{t} if @var{color} is a shade of gray, as defined on @var{frame}'s display. If @var{frame} is omitted or @code{nil}, the question applies to the selected frame. If @var{color} is not a valid color name, this function returns @code{nil}. @end defun @defun color-values color &optional frame @cindex rgb value This function returns a value that describes what @var{color} should ideally look like on @var{frame}. If @var{color} is defined, the value is a list of three integers, which give the amount of red, the amount of green, and the amount of blue. Each integer ranges in principle from 0 to 65535, but some displays may not use the full range. This three-element list is called the @dfn{rgb values} of the color. If @var{color} is not defined, the value is @code{nil}. @example (color-values "black") @result{} (0 0 0) (color-values "white") @result{} (65535 65535 65535) (color-values "red") @result{} (65535 0 0) (color-values "pink") @result{} (65535 49344 52171) (color-values "hungry") @result{} nil @end example The color values are returned for @var{frame}'s display. If @var{frame} is omitted or @code{nil}, the information is returned for the selected frame's display. If the frame cannot display colors, the value is @code{nil}. @findex x-color-values This function used to be called @code{x-color-values}, and that name is still supported as an alias. @end defun @node Text Terminal Colors @section Text Terminal Colors @cindex colors on text terminals Text terminals usually support only a small number of colors, and the computer uses small integers to select colors on the terminal. This means that the computer cannot reliably tell what the selected color looks like; instead, you have to inform your application which small integers correspond to which colors. However, Emacs does know the standard set of colors and will try to use them automatically. The functions described in this section control how terminal colors are used by Emacs. Several of these functions use or return @dfn{rgb values}, described in @ref{Color Names}. These functions accept a display (either a frame or the name of a terminal) as an optional argument. We hope in the future to make Emacs support different colors on different text terminals; then this argument will specify which terminal to operate on (the default being the selected frame's terminal; @pxref{Input Focus}). At present, though, the @var{frame} argument has no effect. @defun tty-color-define name number &optional rgb frame This function associates the color name @var{name} with color number @var{number} on the terminal. The optional argument @var{rgb}, if specified, is an rgb value, a list of three numbers that specify what the color actually looks like. If you do not specify @var{rgb}, then this color cannot be used by @code{tty-color-approximate} to approximate other colors, because Emacs will not know what it looks like. @end defun @defun tty-color-clear &optional frame This function clears the table of defined colors for a text terminal. @end defun @defun tty-color-alist &optional frame This function returns an alist recording the known colors supported by a text terminal. Each element has the form @code{(@var{name} @var{number} . @var{rgb})} or @code{(@var{name} @var{number})}. Here, @var{name} is the color name, @var{number} is the number used to specify it to the terminal. If present, @var{rgb} is a list of three color values (for red, green, and blue) that says what the color actually looks like. @end defun @defun tty-color-approximate rgb &optional frame This function finds the closest color, among the known colors supported for @var{display}, to that described by the rgb value @var{rgb} (a list of color values). The return value is an element of @code{tty-color-alist}. @end defun @defun tty-color-translate color &optional frame This function finds the closest color to @var{color} among the known colors supported for @var{display} and returns its index (an integer). If the name @var{color} is not defined, the value is @code{nil}. @end defun @node Resources @section X Resources This section describes some of the functions and variables for querying and using X resources, or their equivalent on your operating system. @xref{X Resources,, X Resources, emacs, The GNU Emacs Manual}, for more information about X resources. @defun x-get-resource attribute class &optional component subclass The function @code{x-get-resource} retrieves a resource value from the X Window defaults database. Resources are indexed by a combination of a @dfn{key} and a @dfn{class}. This function searches using a key of the form @samp{@var{instance}.@var{attribute}} (where @var{instance} is the name under which Emacs was invoked), and using @samp{Emacs.@var{class}} as the class. The optional arguments @var{component} and @var{subclass} add to the key and the class, respectively. You must specify both of them or neither. If you specify them, the key is @samp{@var{instance}.@var{component}.@var{attribute}}, and the class is @samp{Emacs.@var{class}.@var{subclass}}. @end defun @defvar x-resource-class This variable specifies the application name that @code{x-get-resource} should look up. The default value is @code{"Emacs"}. You can examine X resources for other application names by binding this variable to some other string, around a call to @code{x-get-resource}. @end defvar @defvar x-resource-name This variable specifies the instance name that @code{x-get-resource} should look up. The default value is the name Emacs was invoked with, or the value specified with the @samp{-name} or @samp{-rn} switches. @end defvar To illustrate some of the above, suppose that you have the line: @example xterm.vt100.background: yellow @end example @noindent in your X resources file (whose name is usually @file{~/.Xdefaults} or @file{~/.Xresources}). Then: @example @group (let ((x-resource-class "XTerm") (x-resource-name "xterm")) (x-get-resource "vt100.background" "VT100.Background")) @result{} "yellow" @end group @group (let ((x-resource-class "XTerm") (x-resource-name "xterm")) (x-get-resource "background" "VT100" "vt100" "Background")) @result{} "yellow" @end group @end example @defvar inhibit-x-resources If this variable is non-@code{nil}, Emacs does not look up X resources, and X resources do not have any effect when creating new frames. @end defvar @node Display Feature Testing @section Display Feature Testing @cindex display feature testing The functions in this section describe the basic capabilities of a particular display. Lisp programs can use them to adapt their behavior to what the display can do. For example, a program that ordinarily uses a popup menu could use the minibuffer if popup menus are not supported. The optional argument @var{display} in these functions specifies which display to ask the question about. It can be a display name, a frame (which designates the display that frame is on), or @code{nil} (which refers to the selected frame's display, @pxref{Input Focus}). @xref{Color Names}, @ref{Text Terminal Colors}, for other functions to obtain information about displays. @defun display-popup-menus-p &optional display This function returns @code{t} if popup menus are supported on @var{display}, @code{nil} if not. Support for popup menus requires that the mouse be available, since the menu is popped up by clicking the mouse on some portion of the Emacs display. @end defun @defun display-graphic-p &optional display This function returns @code{t} if @var{display} is a graphic display capable of displaying several frames and several different fonts at once. This is true for displays that use a window system such as X, and false for text terminals. @end defun @defun display-mouse-p &optional display @cindex mouse, availability This function returns @code{t} if @var{display} has a mouse available, @code{nil} if not. @end defun @defun display-color-p &optional display @findex x-display-color-p This function returns @code{t} if the screen is a color screen. It used to be called @code{x-display-color-p}, and that name is still supported as an alias. @end defun @defun display-grayscale-p &optional display This function returns @code{t} if the screen can display shades of gray. (All color displays can do this.) @end defun @defun display-supports-face-attributes-p attributes &optional display @anchor{Display Face Attribute Testing} This function returns non-@code{nil} if all the face attributes in @var{attributes} are supported (@pxref{Face Attributes}). The definition of ``supported'' is somewhat heuristic, but basically means that a face containing all the attributes in @var{attributes}, when merged with the default face for display, can be represented in a way that's @enumerate @item different in appearance than the default face, and @item close in spirit to what the attributes specify, if not exact. @end enumerate Point (2) implies that a @code{:weight black} attribute will be satisfied by any display that can display bold, as will @code{:foreground "yellow"} as long as some yellowish color can be displayed, but @code{:slant italic} will @emph{not} be satisfied by the tty display code's automatic substitution of a dim face for italic. @end defun @defun display-selections-p &optional display This function returns @code{t} if @var{display} supports selections. Windowed displays normally support selections, but they may also be supported in some other cases. @end defun @defun display-images-p &optional display This function returns @code{t} if @var{display} can display images. Windowed displays ought in principle to handle images, but some systems lack the support for that. On a display that does not support images, Emacs cannot display a tool bar. @end defun @defun display-screens &optional display This function returns the number of screens associated with the display. @end defun @defun display-pixel-height &optional display This function returns the height of the screen in pixels. On a character terminal, it gives the height in characters. For graphical terminals, note that on multi-monitor setups this refers to the pixel height for all physical monitors associated with @var{display}. @xref{Multiple Terminals}. @end defun @defun display-pixel-width &optional display This function returns the width of the screen in pixels. On a character terminal, it gives the width in characters. For graphical terminals, note that on multi-monitor setups this refers to the pixel width for all physical monitors associated with @var{display}. @xref{Multiple Terminals}. @end defun @defun display-mm-height &optional display This function returns the height of the screen in millimeters, or @code{nil} if Emacs cannot get that information. For graphical terminals, note that on multi-monitor setups this refers to the height for all physical monitors associated with @var{display}. @xref{Multiple Terminals}. @end defun @defun display-mm-width &optional display This function returns the width of the screen in millimeters, or @code{nil} if Emacs cannot get that information. For graphical terminals, note that on multi-monitor setups this refers to the width for all physical monitors associated with @var{display}. @xref{Multiple Terminals}. @end defun @defopt display-mm-dimensions-alist This variable allows the user to specify the dimensions of graphical displays returned by @code{display-mm-height} and @code{display-mm-width} in case the system provides incorrect values. @end defopt @cindex backing store @defun display-backing-store &optional display This function returns the backing store capability of the display. Backing store means recording the pixels of windows (and parts of windows) that are not exposed, so that when exposed they can be displayed very quickly. Values can be the symbols @code{always}, @code{when-mapped}, or @code{not-useful}. The function can also return @code{nil} when the question is inapplicable to a certain kind of display. @end defun @cindex SaveUnder feature @defun display-save-under &optional display This function returns non-@code{nil} if the display supports the SaveUnder feature. That feature is used by pop-up windows to save the pixels they obscure, so that they can pop down quickly. @end defun @defun display-planes &optional display This function returns the number of planes the display supports. This is typically the number of bits per pixel. For a tty display, it is log to base two of the number of colors supported. @end defun @defun display-visual-class &optional display This function returns the visual class for the screen. The value is one of the symbols @code{static-gray} (a limited, unchangeable number of grays), @code{gray-scale} (a full range of grays), @code{static-color} (a limited, unchangeable number of colors), @code{pseudo-color} (a limited number of colors), @code{true-color} (a full range of colors), and @code{direct-color} (a full range of colors). @end defun @defun display-color-cells &optional display This function returns the number of color cells the screen supports. @end defun These functions obtain additional information about the window system in use where Emacs shows the specified @var{display}. (Their names begin with @code{x-} for historical reasons.) @defun x-server-version &optional display This function returns the list of version numbers of the GUI window system running on @var{display}, such as the X server on GNU and Unix systems. The value is a list of three integers: the major and minor version numbers of the protocol, and the distributor-specific release number of the window system software itself. On GNU and Unix systems, these are normally the version of the X protocol and the distributor-specific release number of the X server software. On MS-Windows, this is the version of the Windows OS. @end defun @defun x-server-vendor &optional display This function returns the vendor that provided the window system software (as a string). On GNU and Unix systems this really means whoever distributes the X server. On MS-Windows this is the vendor ID string of the Windows OS (Microsoft). When the developers of X labeled software distributors as ``vendors'', they showed their false assumption that no system could ever be developed and distributed noncommercially. @end defun @ignore @defvar x-no-window-manager This variable's value is @code{t} if no X window manager is in use. @end defvar @end ignore