;;; button.el --- clickable buttons -*- lexical-binding: t -*- ;; ;; Copyright (C) 2001-2020 Free Software Foundation, Inc. ;; ;; Author: Miles Bader ;; Keywords: extensions, hypermedia ;; Package: emacs ;; ;; This file is part of GNU Emacs. ;; ;; GNU Emacs is free software: you can redistribute it and/or modify ;; it under the terms of the GNU General Public License as published by ;; the Free Software Foundation, either version 3 of the License, or ;; (at your option) any later version. ;; GNU Emacs is distributed in the hope that it will be useful, ;; but WITHOUT ANY WARRANTY; without even the implied warranty of ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the ;; GNU General Public License for more details. ;; You should have received a copy of the GNU General Public License ;; along with GNU Emacs. If not, see . ;;; Commentary: ;; ;; This package defines functions for inserting and manipulating ;; clickable buttons in Emacs buffers, such as might be used for help ;; hyperlinks, etc. ;; ;; In some ways it duplicates functionality also offered by the ;; `widget' package, but the button package has the advantage that it ;; is (1) much faster, (2) much smaller, and (3) much, much, simpler ;; (the code, that is, not the interface). ;; ;; Buttons can either use overlays, in which case the button is ;; represented by the overlay itself, or text-properties, in which case ;; the button is represented by a marker or buffer-position pointing ;; somewhere in the button. In the latter case, no markers into the ;; buffer are retained, which is important for speed if there are ;; extremely large numbers of buttons. Note however that if there is ;; an existing face text-property at the site of the button, the ;; button face may not be visible. Using overlays avoids this. ;; ;; Using `define-button-type' to define default properties for buttons ;; is not necessary, but it is encouraged, since doing so makes the ;; resulting code clearer and more efficient. ;; ;;; Code: ;;; Globals (defface button '((t :inherit link)) "Default face used for buttons." :group 'basic-faces) (defvar button-map (let ((map (make-sparse-keymap))) ;; The following definition needs to avoid using escape sequences that ;; might get converted to ^M when building loaddefs.el (define-key map [(control ?m)] 'push-button) (define-key map [mouse-2] 'push-button) ;; FIXME: You'd think that for keymaps coming from text-properties on the ;; mode-line or header-line, the `mode-line' or `header-line' prefix ;; shouldn't be necessary! (define-key map [mode-line mouse-2] 'push-button) (define-key map [header-line mouse-2] 'push-button) map) "Keymap used by buttons.") (defvar button-buffer-map (let ((map (make-sparse-keymap))) (define-key map [?\t] 'forward-button) (define-key map "\e\t" 'backward-button) (define-key map [backtab] 'backward-button) map) "Keymap useful for buffers containing buttons. Mode-specific keymaps may want to use this as their parent keymap.") ;; Default properties for buttons. (put 'default-button 'face 'button) (put 'default-button 'mouse-face 'highlight) (put 'default-button 'keymap button-map) (put 'default-button 'type 'button) ;; `action' may be either a function to call, or a marker to go to. (put 'default-button 'action #'ignore) (put 'default-button 'help-echo (purecopy "mouse-2, RET: Push this button")) ;; Make overlay buttons go away if their underlying text is deleted. (put 'default-button 'evaporate t) ;; Prevent insertions adjacent to text-property buttons from ;; inheriting their properties. (put 'default-button 'rear-nonsticky t) ;; A `category-symbol' property for the default button type. (put 'button 'button-category-symbol 'default-button) ;;; Button types (which can be used to hold default properties for buttons) ;; Because button-type properties are inherited by buttons using the ;; special `category' property (implemented by both overlays and ;; text-properties), we need to store them on a symbol to which the ;; `category' properties can point. Instead of using the symbol that's ;; the name of each button-type, however, we use a separate symbol (with ;; `-button' appended, and uninterned) to store the properties. This is ;; to avoid name clashes. ;; [this is an internal function] (defsubst button-category-symbol (type) "Return the symbol used by button-type TYPE to store properties. Buttons inherit them by setting their `category' property to that symbol." (or (get type 'button-category-symbol) (error "Unknown button type `%s'" type))) (defun define-button-type (name &rest properties) "Define a `button type' called NAME (a symbol). The remaining arguments form a plist of PROPERTY VALUE pairs, specifying properties to use as defaults for buttons with this type \(a button's type may be set by giving it a `type' property when creating the button, using the :type keyword argument). In addition, the keyword argument :supertype may be used to specify a button-type from which NAME inherits its default property values \(however, the inheritance happens only when NAME is defined; subsequent changes to a supertype are not reflected in its subtypes)." (let ((catsym (make-symbol (concat (symbol-name name) "-button"))) (super-catsym (button-category-symbol (or (plist-get properties 'supertype) (plist-get properties :supertype) 'button)))) ;; Provide a link so that it's easy to find the real symbol. (put name 'button-category-symbol catsym) ;; Initialize NAME's properties using the global defaults. (let ((default-props (symbol-plist super-catsym))) (while default-props (put catsym (pop default-props) (pop default-props)))) ;; Add NAME as the `type' property, which will then be returned as ;; the type property of individual buttons. (put catsym 'type name) ;; Add the properties in PROPERTIES to the real symbol. (while properties (let ((prop (pop properties))) (when (eq prop :supertype) (setq prop 'supertype)) (put catsym prop (pop properties)))) ;; Make sure there's a `supertype' property. (unless (get catsym 'supertype) (put catsym 'supertype 'button)) name)) (defun button-type-put (type prop val) "Set the button-type TYPE's PROP property to VAL." (put (button-category-symbol type) prop val)) (defun button-type-get (type prop) "Get the property of button-type TYPE named PROP." (get (button-category-symbol type) prop)) (defun button-type-subtype-p (type supertype) "Return non-nil if button-type TYPE is a subtype of SUPERTYPE." (or (eq type supertype) (and type (button-type-subtype-p (button-type-get type 'supertype) supertype)))) ;;; Button properties and other attributes (defun button-start (button) "Return the position at which BUTTON starts. This function only works when BUTTON is in the current buffer." (if (overlayp button) (overlay-start button) ;; Must be a text-property button. (or (previous-single-property-change (1+ button) 'button) (point-min)))) (defun button-end (button) "Return the position at which BUTTON ends. This function only works when BUTTON is in the current buffer." (if (overlayp button) (overlay-end button) ;; Must be a text-property button. (or (next-single-property-change button 'button) (point-max)))) (defun button-get (button prop) "Get the property of button BUTTON named PROP. This function only works when BUTTON is in the current buffer." (cond ((overlayp button) (overlay-get button prop)) ((button--area-button-p button) (get-text-property (cdr button) prop (button--area-button-string button))) ((markerp button) (get-text-property button prop (marker-buffer button))) (t ; Must be a text-property button. (get-text-property button prop)))) (defun button-put (button prop val) "Set BUTTON's PROP property to VAL. This function only works when BUTTON is in the current buffer." ;; Treat some properties specially. (cond ((memq prop '(type :type)) ;; We translate a `type' property to a `category' property, ;; since that's what's actually used by overlay and ;; text-property buttons for inheriting properties. (setq prop 'category) (setq val (button-category-symbol val))) ((eq prop 'category) ;; Disallow updating the `category' property directly. (error "Button `category' property may not be set directly"))) ;; Add the property. (cond ((overlayp button) (overlay-put button prop val)) ((button--area-button-p button) (setq button (button--area-button-string button)) (put-text-property 0 (length button) prop val button)) (t ; Must be a text-property button. (put-text-property (or (previous-single-property-change (1+ button) 'button) (point-min)) (or (next-single-property-change button 'button) (point-max)) prop val)))) (defun button-activate (button &optional use-mouse-action) "Call BUTTON's `action' property. If USE-MOUSE-ACTION is non-nil, invoke the button's `mouse-action' property instead of `action'; if the button has no `mouse-action', the value of `action' is used instead. The action can either be a marker or a function. If it's a marker then goto it. Otherwise if it is a function then it is called with BUTTON as only argument. BUTTON is either an overlay, a buffer position, or (for buttons in the mode-line or header-line) a string. If BUTTON has a `button-data' value, call the function with this value instead of BUTTON. This function only works when BUTTON is in the current buffer." (let ((action (or (and use-mouse-action (button-get button 'mouse-action)) (button-get button 'action))) (data (button-get button 'button-data))) (if (markerp action) (save-selected-window (select-window (display-buffer (marker-buffer action))) (goto-char action) (recenter 0)) (funcall action (or data button))))) (defun button-label (button) "Return BUTTON's text label. This function only works when BUTTON is in the current buffer." (if (button--area-button-p button) (substring-no-properties (button--area-button-string button)) (buffer-substring-no-properties (button-start button) (button-end button)))) (defsubst button-type (button) "Return BUTTON's button-type." (button-get button 'type)) (defun button-has-type-p (button type) "Return non-nil if BUTTON has button-type TYPE, or one of its subtypes." (button-type-subtype-p (button-get button 'type) type)) (defun button--area-button-p (b) "Return non-nil if BUTTON is an area button. Such area buttons are used for buttons in the mode-line and header-line." (stringp (car-safe b))) (defalias 'button--area-button-string #'car "Return area button BUTTON's button-string.") ;;; Creating overlay buttons (defun make-button (beg end &rest properties) "Make a button from BEG to END in the current buffer. The remaining arguments form a plist of PROPERTY VALUE pairs, specifying properties to add to the button. In addition, the keyword argument :type may be used to specify a button-type from which to inherit other properties; see `define-button-type'. Also see `make-text-button', `insert-button'." (let ((overlay (make-overlay beg end nil t nil))) (while properties (button-put overlay (pop properties) (pop properties))) ;; Put a pointer to the button in the overlay, so it's easy to get ;; when we don't actually have a reference to the overlay. (overlay-put overlay 'button overlay) ;; If the user didn't specify a type, use the default. (unless (overlay-get overlay 'category) (overlay-put overlay 'category 'default-button)) ;; OVERLAY is the button, so return it. overlay)) (defun insert-button (label &rest properties) "Insert a button with the label LABEL. The remaining arguments form a plist of PROPERTY VALUE pairs, specifying properties to add to the button. In addition, the keyword argument :type may be used to specify a button-type from which to inherit other properties; see `define-button-type'. Also see `insert-text-button', `make-button'." (apply #'make-button (prog1 (point) (insert label)) (point) properties)) ;;; Creating text-property buttons (defun make-text-button (beg end &rest properties) "Make a button from BEG to END in the current buffer. The remaining arguments form a plist of PROPERTY VALUE pairs, specifying properties to add to the button. In addition, the keyword argument :type may be used to specify a button-type from which to inherit other properties; see `define-button-type'. This function is like `make-button', except that the button is actually part of the text instead of being a property of the buffer. That is, this function uses text properties, the other uses overlays. Creating large numbers of buttons can also be somewhat faster using `make-text-button'. Note, however, that if there is an existing face property at the site of the button, the button face may not be visible. You may want to use `make-button' in that case. If the property `button-data' is present, it will later be used as the argument for the `action' callback function instead of the default argument, which is the button itself. BEG can also be a string, in which case a copy of it is made into a button. Also see `insert-text-button'." (let ((object nil) (type-entry (or (plist-member properties 'type) (plist-member properties :type)))) (when (stringp beg) (setq object (copy-sequence beg)) (setq beg 0) (setq end (length object))) ;; Disallow setting the `category' property directly. (when (plist-get properties 'category) (error "Button `category' property may not be set directly")) (if (null type-entry) ;; The user didn't specify a `type' property, use the default. (setq properties (cons 'category (cons 'default-button properties))) ;; The user did specify a `type' property. Translate it into a ;; `category' property, which is what's actually used by ;; text-properties for inheritance. (setcar type-entry 'category) (setcar (cdr type-entry) (button-category-symbol (cadr type-entry)))) ;; Now add all the text properties at once. (add-text-properties beg end ;; Each button should have a non-eq `button' ;; property so that next-single-property-change can ;; detect boundaries reliably. (cons 'button (cons (list t) properties)) object) ;; Return something that can be used to get at the button. (or object beg))) (defun insert-text-button (label &rest properties) "Insert a button with the label LABEL. The remaining arguments form a plist of PROPERTY VALUE pairs, specifying properties to add to the button. In addition, the keyword argument :type may be used to specify a button-type from which to inherit other properties; see `define-button-type'. This function is like `insert-button', except that the button is actually part of the text instead of being a property of the buffer. Creating large numbers of buttons can also be somewhat faster using `insert-text-button'. Also see `make-text-button'." (apply #'make-text-button (prog1 (point) (insert label)) (point) properties)) ;;; Finding buttons in a buffer (defun button-at (pos) "Return the button at position POS in the current buffer, or nil. If the button at POS is a text property button, the return value is a marker pointing to POS." (let ((button (get-char-property pos 'button))) (and button (get-char-property pos 'category) (if (overlayp button) button ;; Must be a text-property button; ;; return a marker pointing to it. (copy-marker pos t))))) (defun next-button (pos &optional count-current) "Return the next button after position POS in the current buffer. If COUNT-CURRENT is non-nil, count any button at POS in the search, instead of starting at the next button." (unless count-current ;; Search for the next button boundary. (setq pos (next-single-char-property-change pos 'button))) (and (< pos (point-max)) (or (button-at pos) ;; We must have originally been on a button, and are now in ;; the inter-button space. Recurse to find a button. (next-button pos)))) (defun previous-button (pos &optional count-current) "Return the previous button before position POS in the current buffer. If COUNT-CURRENT is non-nil, count any button at POS in the search, instead of starting at the next button." (let ((button (button-at pos))) (if button (if count-current button ;; We started out on a button, so move to its start and look ;; for the previous button boundary. (setq pos (previous-single-char-property-change (button-start button) 'button)) (let ((new-button (button-at pos))) (if new-button ;; We are in a button again; this can happen if there ;; are adjacent buttons (or at bob). (unless (= pos (button-start button)) new-button) ;; We are now in the space between buttons. (previous-button pos)))) ;; We started out in the space between buttons. (setq pos (previous-single-char-property-change pos 'button)) (or (button-at pos) (and (> pos (point-min)) (button-at (1- pos))))))) ;;; User commands (defun push-button (&optional pos use-mouse-action) "Perform the action specified by a button at location POS. POS may be either a buffer position or a mouse-event. If USE-MOUSE-ACTION is non-nil, invoke the button's `mouse-action' property instead of its `action' property; if the button has no `mouse-action', the value of `action' is used instead. The action in both cases may be either a function to call or a marker to display and is invoked using `button-activate' (which see). POS defaults to point, except when `push-button' is invoked interactively as the result of a mouse-event, in which case, the mouse event is used. If there's no button at POS, do nothing and return nil, otherwise return t." (interactive (list (if (integerp last-command-event) (point) last-command-event))) (if (and (not (integerp pos)) (eventp pos)) ;; POS is a mouse event; switch to the proper window/buffer (let ((posn (event-start pos))) (with-current-buffer (window-buffer (posn-window posn)) (let* ((str (posn-string posn)) (str-button (and str (get-text-property (cdr str) 'button (car str))))) (if str-button ;; mode-line, header-line, or display string event. (button-activate str t) (push-button (posn-point posn) t))))) ;; POS is just normal position (let ((button (button-at (or pos (point))))) (when button (button-activate button use-mouse-action) t)))) (defun button--help-echo (button) "Evaluate BUTTON's `help-echo' property and return its value." (let ((help (button-get button 'help-echo))) (if (functionp help) (let ((obj (if (overlayp button) button (current-buffer)))) (funcall help (selected-window) obj (button-start button))) (eval help lexical-binding)))) (defun forward-button (n &optional wrap display-message no-error) "Move to the Nth next button, or Nth previous button if N is negative. If N is 0, move to the start of any button at point. If WRAP is non-nil, moving past either end of the buffer continues from the other end. If DISPLAY-MESSAGE is non-nil, the button's `help-echo' property is displayed. Any button with a non-nil `skip' property is skipped over. If NO-ERROR, return nil if no further buttons could be found instead of erroring out. Returns the button found." (interactive "p\nd\nd") (let (button) (if (zerop n) ;; Move to start of current button (if (setq button (button-at (point))) (goto-char (button-start button))) ;; Move to Nth next button (let ((iterator (if (> n 0) #'next-button #'previous-button)) (wrap-start (if (> n 0) (point-min) (point-max))) opoint fail) (setq n (abs n)) (setq button t) ; just to start the loop (while (and (null fail) (> n 0) button) (setq button (funcall iterator (point))) (when (and (not button) wrap) (setq button (funcall iterator wrap-start t))) (when button (goto-char (button-start button)) ;; Avoid looping forever (e.g., if all the buttons have ;; the `skip' property). (cond ((null opoint) (setq opoint (point))) ((= opoint (point)) (setq fail t))) (unless (button-get button 'skip) (setq n (1- n))))))) (if (null button) (unless no-error (user-error (if wrap "No buttons!" "No more buttons"))) (let ((msg (and display-message (button--help-echo button)))) (when msg (message "%s" msg))) button))) (defun backward-button (n &optional wrap display-message no-error) "Move to the Nth previous button, or Nth next button if N is negative. If N is 0, move to the start of any button at point. If WRAP is non-nil, moving past either end of the buffer continues from the other end. If DISPLAY-MESSAGE is non-nil, the button's `help-echo' property is displayed. Any button with a non-nil `skip' property is skipped over. If NO-ERROR, return nil if no further buttons could be found instead of erroring out. Returns the button found." (interactive "p\nd\nd") (forward-button (- n) wrap display-message no-error)) (provide 'button) ;;; button.el ends here