bug#5721: Feature request: Function that returns absolute coordinates

[martin rudalics <rudalics@gmx.at>]

 > I'd like the request to be reopened, because the current function
 > `window-inside-absolute-pixel-edges' does not provide the requested
 > behaviour.

I think your analysis is correct but will leave it to Jan to decide how
to proceed.

 > Suppose no fringes, and header-line.  All considerations for a GTK build.
 >
 > 0--------------------------------------*
 > |           display                    |
 > | A----------------------------+       |
 > | |      emacs@foo.bar         +       |
 > | |-B------------------------+ +       |
 > | | |       toolbar          | |       |
 > | | +------------------------+ |       |
 > | | |       menubar          | |       |
 > | | C------------------------+ |       |
 > | | |                        | |       |
 > | | |       window           | |       |
 > | | |   D---------+          | |       |
 > | | |   | tooltip |          | |       |
 > | | |   +---------+          | |       |
 > | | +------------------------+ |       |
 > | *----------------------------*       |
 > |                                      |
 > *--------------------------------------*

Where did/do we put the internal borders of the frame?

 > We have a buffer position D =
 > (D.x, D.y) in some window and want to display a tool-tip there. At the
 > moment,
 >
 >        (posn-x-y (posn-at-point))
 >
 > gives us a position relative to C, so we would need it's absolute
 > position.
 >
 > But `window-absolute-pixel-edges' gives the absolute position of
 >
 >     (C.x - (B.x - A.x), C.y - (B.y - A.y))
 >   = (A.x , C.y - (B.y - A.y)) ,
 >
 > that is, it does not account for the width and height (B - A) of the
 > window managers decorations.  Furthermore these sizes are unknown to the
 > lisp side, making it impossible to complete the desired task.

I'm not sure whether we can correctly retrieve the decorations always
and everywhere.  But note that for maximized and full-screen frames
there usually are no outer borders and with full-screen frames there's
no titlebar either.  How does your patch handle these?

 > So it seems to me that `window-absolute-pixel-edges' should return the
 > absolute position of C, such that the tool-tip (or other frame) may be
 > positioned at C + D.
 >
 > I noticed, that the frame struct already has members x_pixels_diff and
 > y_pixels_diff, such that
 >
 >     (x_pixels_diff, y_pixels_diff) = (B.x - A.x, B.y - A.y) ,
 >
 > such that we may compute C with this values.  So I propose extending
 > `calc_absolute_offset' by adding these pixel_diff values.  For GTK this
 > appears to be especially easy, since these diff values already account
 > for the tool-bar and menu-bar sizes.

martin