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authorRichard M. Stallman1994-03-27 21:24:22 +0000
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1@c -*-texinfo-*-
2@c This is part of the GNU Emacs Lisp Reference Manual.
3@c Copyright (C) 1990, 1991, 1992, 1993, 1994 Free Software Foundation, Inc.
4@c See the file elisp.texi for copying conditions.
5@setfilename ../info/frames
6@node Frames, Positions, Windows, Top
7@chapter Frames
8@cindex frame
9
10 A @var{frame} is a rectangle on the screen that contains one or more
11Emacs windows. A frame initially contains a single main window (plus
12perhaps a minibuffer window) which you can subdivide vertically or
13horizontally into smaller windows.
14
15@cindex terminal frame
16@cindex X window frame
17 When Emacs runs on a text-only terminal, it has just one frame, a
18@dfn{terminal frame}. There is no way to create another terminal frame
19after startup. If Emacs has an X display, it does not have a terminal
20frame; instead, it starts with a single @dfn{X window frame}. You can
21create more; see @ref{Creating Frames}.
22
23@defun framep object
24This predicate returns @code{t} if @var{object} is a frame, and
25@code{nil} otherwise.
26@end defun
27
28@menu
29* Creating Frames:: Creating additional X Window frames.
30* Frame Parameters:: Controlling frame size, position, font, etc.
31* Deleting Frames:: Frames last until explicitly deleted.
32* Finding All Frames:: How to examine all existing frames.
33* Frames and Windows:: A frame contains windows;
34 display of text always works through windows.
35* Minibuffers and Frames:: How a frame finds the minibuffer to use.
36* Input Focus:: Specifying the selected frame.
37* Visibility of Frames:: Frames may be visible or invisible, or icons.
38* Raising and Lowering:: Raising a frame makes it hide other X windows;
39 lowering it makes the others hide them.
40* Frame Configurations:: Saving the state of all frames.
41* Mouse Tracking:: Getting events that say when the mouse moves.
42* Mouse Position:: Asking where the mouse is, or moving it.
43* Pop-Up Menus:: Displaying a menu for the user to select from.
44* Dialog Boxes:: Displaying a box to ask yes or no.
45* X Selections:: Transferring text to and from other X clients.
46* X Connections:: Opening and closing the X server connection.
47* Resources:: Getting resource values from the server.
48* Server Data:: Getting info about the X server.
49@end menu
50
51 @xref{Display}, for related information.
52
53@node Creating Frames
54@section Creating Frames
55
56To create a new frame, call the function @code{make-frame}.
57
58@defun make-frame alist
59This function creates a new frame, if the display mechanism permits
60creation of frames. (An X server does; an ordinary terminal does not.)
61
62The argument is an alist specifying frame parameters. Any parameters
63not mentioned in @var{alist} default according to the value of the
64variable @code{default-frame-alist}; parameters not specified there
65either default from the standard X defaults file and X resources.
66
67The set of possible parameters depends in principle on what kind of
68window system Emacs uses to display its the frames. @xref{X Frame
69Parameters}, for documentation of individual parameters you can specify
70when creating an X window frame.
71@end defun
72
73@defvar default-frame-alist
74This is an alist specifying default values of frame parameters.
75Each element has the form:
76
77@example
78(@var{parameter} . @var{value})
79@end example
80
81If you use options that specify window appearance when you invoke Emacs,
82they take effect by adding elements to @code{default-frame-alist}.
83@xref{Command Arguments,,, emacs, The GNU Emacs Manual}.
84@end defvar
85
86@defvar before-make-frame-hook
87A normal hook run by @code{make-frame} before it actually creates the
88frame.
89@end defvar
90
91@defvar after-make-frame-hook
92A normal hook run by @code{make-frame} after it creates the frame.
93@end defvar
94
95@node Frame Parameters
96@section Frame Parameters
97
98A frame has many parameters that control its appearance and behavior.
99Just what parameters a frame has depends on what display mechanism it
100uses.
101
102Frame parameters exist for the sake of window systems. A terminal frame
103has a few parameters, for compatibility's sake only. You can't change
104these parameters directly; the only ones that ever change are the height
105and width.
106
107@menu
108* Parameter Access:: How to change a frame's parameters.
109* Initial Parameters:: Specifying frame parameters when you make a frame.
110* X Frame Parameters:: Individual parameters documented.
111* Size And Position:: Changing the size and position of a frame.
112@end menu
113
114@node Parameter Access
115@subsection Access to Frame Parameters
116
117These functions let you read and change the parameter values of a
118frame.
119
120@defun frame-parameters frame
121The function @code{frame-parameters} returns an alist listing all the
122parameters of @var{frame} and their values.
123@end defun
124
125@defun modify-frame-parameters frame alist
126This function alters the parameters of frame @var{frame} based on the
127elements of @var{alist}. Each element of @var{alist} has the form
128@code{(@var{parm} . @var{value})}, where @var{parm} is a symbol naming a
129parameter. If you don't mention a parameter in @var{alist}, its value
130doesn't change.
131@end defun
132
133@node Initial Parameters
134@subsection Initial Frame Parameters
135
136You can specify the parameters for the initial startup frame
137by setting @code{initial-frame-alist} in your @file{.emacs} file.
138
139@defvar initial-frame-alist
140This variable's value is an alist of parameter values used when creating
141the initial X window frame.
142@end defvar
143
144If these parameters specify a separate minibuffer-only frame,
145and you have not created one, Emacs creates one for you.
146
147@defvar minibuffer-frame-alist
148This variable's value is an alist of parameter values used when creating
149an initial minibuffer-only frame---if such a frame is needed, according
150to the parameters for the main initial frame.
151@end defvar
152
153@node X Frame Parameters
154@subsection X Window Frame Parameters
155
156Just what parameters a frame has depends on what display mechanism it
157uses. Here is a table of the parameters of an X window frame:
158
159@table @code
160@item name
161The name of the frame. Most window managers display the frame's name in
162the frame's border, at the top of the frame. If you don't specify a
163name, and you have more than one frame, Emacs sets the frame name based
164on the buffer displayed in the frame's selected window.
165
166If you specify the frame name explicitly when you create the frame, the
167name is also used (instead of the name of the Emacs executable) when
168looking up X resources for the frame.
169
170@item left
171The screen position of the left edge, in pixels.
172
173@item top
174The screen position of the top edge, in pixels.
175
176@item height
177The height of the frame contents, in pixels.
178
179@item width
180The width of the frame contents, in pixels.
181
182@item window-id
183The number of the X window for the frame.
184
185@item minibuffer
186Whether this frame has its own minibuffer. The value @code{t} means
187yes, @code{nil} means no, @code{only} means this frame is just a
188minibuffer, a minibuffer window (in some other frame) means the new
189frame uses that minibuffer.
190
191@item font
192The name of the font for displaying text in the frame. This is a
193string.
194
195@item auto-raise
196Whether selecting the frame raises it (non-@code{nil} means yes).
197
198@item auto-lower
199Whether deselecting the frame lowers it (non-@code{nil} means yes).
200
201@item vertical-scroll-bars
202Whether the frame has scroll bars for vertical scrolling
203(non-@code{nil} means yes).
204
205@item horizontal-scroll-bars
206Whether the frame has scroll bars for horizontal scrolling
207(non-@code{nil} means yes). (Horizontal scroll bars are not currently
208implemented.)
209
210@item icon-type
211The type of icon to use for this frame when it is iconified.
212Non-@code{nil} specifies a bitmap icon, @code{nil} a text icon.
213
214@item foreground-color
215The color to use for the inside of a character. This is a string; the X
216server defines the meaningful color names.
217
218@item background-color
219The color to use for the background of text.
220
221@item mouse-color
222The color for the mouse cursor.
223
224@item cursor-color
225The color for the cursor that shows point.
226
227@item border-color
228The color for the border of the frame.
229
230@item cursor-type
231The way to display the cursor. There are two legitimate values:
232@code{bar} and @code{box}. The symbol @code{bar} specifies a vertical
233bar between characters as the cursor. The symbol @code{box} specifies
234an ordinary black box overlaying the character after point; that is the
235default.
236
237@item border-width
238The width in pixels of the window border.
239
240@item internal-border-width
241The distance in pixels between text and border.
242
243@item unsplittable
244If non-@code{nil}, this frame's window is never split automatically.
245
246@item visibility
247The state of visibility of the frame. There are three possibilities:
248@code{nil} for invisible, @code{t} for visible, and @code{icon} for
249iconified. @xref{Visibility of Frames}.
250
251@item menu-bar-lines
252The number of lines to allocate at the top of the frame for a menu bar.
253The default is 1. @xref{Menu Bar}.
254
255@item parent-id
256@c ??? Not yet working.
257The X window number of the window that should be the parent of this one.
258Specifying this lets you create an Emacs window inside some other
259application's window. (It is not certain this will be implemented; try
260it and see if it works.)
261@end table
262
263@node Size And Position
264@subsection Frame Size And Position
265
266 You can read or change the size and position of a frame using the
267frame parameters @code{left}, @code{top}, @code{height} and
268@code{width}. When you create a frame, you must specify either both
269size parameters or neither. Likewise, you must specify either both
270position parameters or neither. Whatever geometry parameters you don't
271specify are chosen by the window manager in its usual fashion.
272
273 Here are some special features for working with sizes and positions:
274
275@defun set-frame-position frame left top
276This function sets the position of the top left corner of
277@var{frame}---to @var{left} and @var{top}. These arguments are measured
278in pixels, counting from the top left corner of the screen.
279@end defun
280
281@defun frame-height &optional frame
282@defunx frame-width &optional frame
283These functions return the height and width of @var{frame}, measured in
284characters. If you don't supply @var{frame}, they use the selected
285frame.
286@end defun
287
288@defun frame-pixel-height &optional frame
289@defunx frame-pixel-width &optional frame
290These functions return the height and width of @var{frame}, measured in
291pixels. If you don't supply @var{frame}, they use the selected frame.
292@end defun
293
294@defun frame-char-height &optional frame
295@defunx frame-char-width &optional frame
296These functions return the height and width, respectively, of a
297character in @var{frame}, measured in pixels. The values depend on the
298choice of font. If you don't supply @var{frame}, these functions use
299the selected frame.
300@end defun
301
302@defun set-frame-size frame cols rows
303This function sets the size of @var{frame}, measured in
304characters; @var{cols} and @var{rows} specify the new width and height.
305
306To set the size with values measured in pixels, use
307@code{modify-frame-parameters} to set the @code{width} and @code{height}
308parameters. @xref{X Frame Parameters}.
309@end defun
310
311 The old-fashioned functions @code{set-screen-height} and
312@code{set-screen-width}, which were used to specify the height and width
313of the screen in Emacs versions that did not support multiple frames,
314are still usable. They apply to the selected frame. @xref{Screen
315Size}.
316
317@defun x-parse-geometry geom
318@cindex geometry specification
319The function @code{x-parse-geometry} converts a standard X windows
320geometry string to an alist which you can use as part of the argument to
321@code{make-frame}.
322
323The alist describes which parameters were specified in @var{geom}, and
324gives the values specified for them. Each element looks like
325@code{(@var{parameter} . @var{value})}. The possible @var{parameter}
326values are @code{left}, @code{top}, @code{width}, and @code{height}.
327
328@smallexample
329(x-parse-geometry "35x70+0-0")
330 @result{} ((width . 35) (height . 70) (left . 0) (top . -1))
331@end smallexample
332@end defun
333
334@ignore
335New functions @code{set-frame-height} and @code{set-frame-width} set the
336size of a specified frame. The frame is the first argument; the size is
337the second.
338@end ignore
339
340@node Deleting Frames
341@section Deleting Frames
342@cindex deletion of frames
343
344Frames remain potentially visible until you explicitly @dfn{delete}
345them. A deleted frame cannot appear on the screen, but continues to
346exist as a Lisp object until there are no references to it. There is no
347way to cancel the deletion of a frame aside from restoring a saved frame
348configuration (@pxref{Frame Configurations}); this is similar to the
349way windows behave.
350
351@deffn Command delete-frame &optional frame
352This function deletes the frame @var{frame}. By default, @var{frame} is
353the selected frame.
354@end deffn
355
356@defun frame-live-p frame
357The function @code{frame-live-p} returns non-@code{nil} if the frame
358@var{frame} has not been deleted.
359@end defun
360
361@node Finding All Frames
362@section Finding All Frames
363
364@defun frame-list
365The function @code{frame-list} returns a list of all the frames that
366have not been deleted. It is analogous to @code{buffer-list} for
367buffers. The list that you get is newly created, so modifying the list
368doesn't have any effect on the internals of Emacs.
369@end defun
370
371@defun visible-frame-list
372This function returns a list of just the currently visible frames.
373@xref{Visibility of Frames}.
374@end defun
375
376@defun next-frame &optional frame minibuf
377The function @code{next-frame} lets you cycle conveniently through all
378the frames from an arbitrary starting point. It returns the ``next''
379frame after @var{frame} in the cycle. If @var{frame} is omitted or
380@code{nil}, it defaults to the selected frame.
381
382The second argument, @var{minibuf}, says which frames to consider:
383
384@table @asis
385@item @code{nil}
386Exclude minibuffer-only frames.
387@item @code{visible}
388Consider all visible frames.
389@item a window
390Consider only the frames using that particular window as their
391minibuffer.
392@item anything else
393Consider all frames.
394@end table
395@end defun
396
397@defun previous-frame &optional frame minibuf
398Like @code{next-frame}, but cycles through all frames in the opposite
399direction.
400@end defun
401
402@node Frames and Windows
403@section Frames and Windows
404
405All the non-minibuffer windows in a frame are arranged in a tree of
406subdivisions; the root of this tree is available via the function
407@code{frame-root-window}. Each window is part of one and
408only one frame; you can get the frame with @code{window-frame}.
409
410@defun frame-root-window frame
411This returns the root window of frame @var{frame}.
412@end defun
413
414@defun window-frame window
415This function returns the frame that @var{window} is on.
416@end defun
417
418At any time, exactly one window on any frame is @dfn{selected within the
419frame}. The significance of this designation is that selecting the
420frame also selects this window. You can get the frame's current
421selected window with @code{frame-selected-window}.
422
423@defun frame-selected-window frame
424This function returns the window on @var{frame} which is selected within
425@var{frame}.
426@end defun
427
428Conversely, selecting a window for Emacs with @code{select-window} also
429makes that window selected within its frame. @xref{Selecting Windows}.
430
431@node Minibuffers and Frames
432@section Minibuffers and Frames
433
434Normally, each frame has its own minibuffer window at the bottom, which
435is used whenever that frame is selected. If the frame has a minibuffer,
436you can get it with @code{minibuffer-window} (@pxref{Minibuffer Misc}).
437
438However, you can also create a frame with no minibuffer. Such a frame
439must use the minibuffer window of some other frame. When you create the
440frame, you can specify explicitly the frame on which to find the
441minibuffer to use. If you don't, then the minibuffer is found in the
442frame which is the value of the variable
443@code{default-minibuffer-frame}. Its value should be a frame which does
444have a minibuffer.
445
446If you use a minibuffer-only frame, you might want that frame to raise
447when you enter the minibuffer. If so, set the variable
448@code{minibuffer-auto-raise} to @code{t}. @xref{Raising and Lowering}.
449
450@node Input Focus
451@section Input Focus
452@cindex input focus
453@cindex selected frame
454
455At any time, one frame in Emacs is the @dfn{selected frame}. The selected
456window always resides on the selected frame.
457
458@defun selected-frame
459This function returns the selected frame.
460@end defun
461
462The X server normally directs keyboard input to the X window that the
463mouse is in. Some window managers use mouse clicks or keyboard events
464to @dfn{shift the focus} to various X windows, overriding the normal
465behavior of the server.
466
467Lisp programs can switch frames ``temporarily'' by calling
468the function @code{select-frame}. This does not override the window
469manager; rather, it escapes from the window manager's control until
470that control is somehow reasserted.
471
472@c ??? This is not yet implemented properly.
473@defun select-frame frame
474This function selects frame @var{frame}, temporarily disregarding the
475focus of the X server. The selection of @var{frame} lasts until the
476next time the user does something to select a different frame, or until
477the next time this function is called.
478@end defun
479
480Emacs cooperates with the X server and the window managers by arranging
481to select frames according to what the server and window manager ask
482for. It does so by generating a special kind of input event, called a
483@dfn{focus} event. The command loop handles a focus event by calling
484@code{handle-select-frame}. @xref{Focus Events}.
485
486@deffn Command handle-switch-frame frame
487This function handles a focus event by selecting frame @var{frame}.
488
489Focus events normally do their job by invoking this command.
490Don't call it for any other reason.
491@end deffn
492
493@defun redirect-frame-focus frame focus-frame
494This function redirects focus from @var{frame} to @var{focus-frame}.
495This means that @var{focus-frame} will receive subsequent keystrokes and
496intended for @var{frame}. After such an event, the value of
497@code{last-event-frame} will be @var{focus-frame}. Also, switch-frame
498events specifying @var{frame} will instead select @var{focus-frame}.
499
500If @var{focus-frame} is @code{nil}, that cancels any existing
501redirection for @var{frame}, which therefore once again receives its own
502events.
503
504One use of focus redirection is for frames that don't have minibuffers.
505These frames use minibuffers on other frames. Activating a minibuffer
506on another frame redirects focus to that frame. This puts the focus on
507the minibuffer's frame, where it belongs, even though the mouse remains
508in the frame which activated the minibuffer.
509
510Selecting a frame can also change focus redirections. Selecting frame
511@code{bar}, when @code{foo} had been selected, changes any redirections
512pointing to @code{foo} so that they point to @code{bar} instead. This
513allows focus redirection to work properly when the user switches from
514one frame to another using @code{select-window}.
515
516This means that a frame whose focus is redirected to itself is treated
517differently from a frame whose focus is not redirected.
518@code{select-frame} affects the former but not the latter.
519
520The redirection lasts until @code{redirect-frame-focus} is called to
521change it.
522@end defun
523
524@node Visibility of Frames
525@section Visibility of Frames
526@cindex visible frame
527@cindex invisible frame
528@cindex iconified frame
529@cindex frame visibility
530
531A frame may be @dfn{visible}, @dfn{invisible}, or @dfn{iconified}. If
532it is visible, you can see its contents. If it is iconified, the
533frame's contents do not appear on the screen, but an icon does. If the
534frame is invisible, it doesn't show in the screen, not even as an icon.
535
536@deffn Command make-frame-visible &optional frame
537This function makes frame @var{frame} visible. If you omit @var{frame},
538it makes the selected frame visible.
539@end deffn
540
541@deffn Command make-frame-invisible &optional frame
542This function makes frame @var{frame} invisible. If you omit
543@var{frame}, it makes the selected frame invisible.
544@end deffn
545
546@deffn Command iconify-frame &optional frame
547This function iconifies frame @var{frame}. If you omit @var{frame}, it
548iconifies the selected frame.
549@end deffn
550
551@defun frame-visible-p frame
552This returns the visibility status of frame @var{frame}. The value is
553@code{t} if @var{frame} is visible, @code{nil} if it is invisible, and
554@code{icon} if it is iconified.
555@end defun
556
557 The visibility status of a frame is also available as a frame
558parameter. You can read or change it as such. @xref{X Frame
559Parameters}.
560
561@node Raising and Lowering
562@section Raising and Lowering Frames
563
564The X Window System uses a desktop metaphor. Part of this metaphor is
565the idea that windows are stacked in a notional third dimension
566perpendicular to the screen surface, and thus ordered from ``highest''
567to ``lowest''. Where two windows overlap, the one higher up covers the
568one underneath. Even a window at the bottom of the stack can be seen if
569no other window overlaps it.
570
571@cindex raising a frame
572@cindex lowering a frame
573A window's place in this ordering is not fixed; in fact, users tend to
574change the order frequently. @dfn{Raising} a window means moving it
575``up'', to the top of the stack. @dfn{Lowering} a window means moving
576it to the bottom of the stack. This motion is in the notional third
577dimension only, and does not change the position of the window on the
578screen.
579
580You can raise and lower Emacs's X windows with these functions:
581
582@defun raise-frame frame
583This function raises frame @var{frame}.
584@end defun
585
586@defun lower-frame frame
587This function lowers frame @var{frame}.
588@end defun
589
590@defopt minibuffer-auto-raise
591If this is non-@code{nil}, activation of the minibuffer raises the frame
592that the minibuffer window is in.
593@end defopt
594
595You can also enable auto-raise (raising automatically when a frame is
596selected) or auto-lower (lowering automatically when it is deselected)
597for any frame using frame parameters. @xref{X Frame Parameters}.
598
599@node Frame Configurations
600@section Frame Configurations
601@cindex frame configuration
602
603 A @dfn{frame configuration} records the current arrangement of frames,
604all their properties, and the window configuration of each one.
605
606@defun current-frame-configuration
607This function returns a frame configuration list which describes
608the current arrangement of frames and their contents.
609@end defun
610
611@defun set-frame-configuration configuration
612This function restores the state of frames described in
613@var{configuration}.
614@end defun
615
616@node Mouse Tracking
617@section Mouse Tracking
618@cindex mouse tracking
619@cindex tracking the mouse
620
621Sometimes it is useful to @dfn{track} the mouse, which means, to display
622something to indicate where the mouse is and move the indicator as the
623mouse moves. For efficient mouse tracking, you need a way to wait until
624the mouse actually moves.
625
626The convenient way to track the mouse is to ask for events to represent
627mouse motion. Then you can wait for motion by waiting for an event. In
628addition, you can easily handle any other sorts of events that may
629occur. That is useful, because normally you don't want to track the
630mouse forever---only until some other event, such as the release of a
631button.
632
633@defspec track-mouse body@dots{}
634Execute @var{body}, meanwhile generating input events for mouse motion.
635The code in @var{body} can read these events with @code{read-event} or
636@code{read-key-sequence}. @xref{Motion Events}, for the format of mouse
637motion events.
638
639The value of @code{track-mouse} is that of the last form in @var{body}.
640@end defspec
641
642The usual purpose of tracking mouse motion is to indicate on the screen
643the consequences of pushing or releasing a button at the current
644position.
645
646@ignore
647@c These are not implemented yet.
648
649These functions change the screen appearance instantaneously. The
650effect is transient, only until the next ordinary Emacs redisplay. That
651is ok for mouse tracking, since it doesn't make sense for mouse tracking
652to change the text, and the body of @code{track-mouse} normally reads
653the events itself and does not do redisplay.
654
655@defun x-contour-region window beg end
656This function draws lines to make a box around the text from @var{beg}
657to @var{end}, in window @var{window}.
658@end defun
659
660@defun x-uncontour-region window beg end
661This function erases the lines that would make a box around the text
662from @var{beg} to @var{end}, in window @var{window}. Use it to remove
663a contour that you previously made by calling @code{x-contour-region}.
664@end defun
665
666@defun x-draw-rectangle frame left top right bottom
667This function draws a hollow rectangle on frame @var{frame} with the
668specified edge coordinates, all measured in pixels from the inside top
669left corner. It uses the cursor color, the one used for indicating the
670location of point.
671@end defun
672
673@defun x-erase-rectangle frame left top right bottom
674This function erases a hollow rectangle on frame @var{frame} with the
675specified edge coordinates, all measured in pixels from the inside top
676left corner. Erasure means redrawing the text and background that
677normally belong in the specified rectangle.
678@end defun
679@end ignore
680
681@node Mouse Position
682@section Mouse Position
683@cindex mouse position
684@cindex position of mouse
685
686 The functions @code{mouse-position} and @code{set-mouse-position}
687give access to the current position of the mouse.
688
689@defun mouse-position
690This function returns a description of the position of the mouse. The
691value looks like @code{(@var{frame} @var{x} . @var{y})}, where @var{x}
692and @var{y} are integers giving the position in pixels relative to the
693top left corner of the inside of @var{frame}.
694@end defun
695
696@defun set-mouse-position frame x y
697This function @dfn{warps the mouse} to position @var{x}, @var{y} in
698frame @var{frame}. The arguments @var{x} and @var{y} are integers,
699giving the position in pixels relative to the top left corner of the
700inside of @var{frame}.
701
702@cindex warping the mouse
703@cindex mouse warping
704Warping the mouse means changing the screen position of the mouse as if
705the user had moved the physical mouse---thus simulating the effect of
706actual mouse motion.
707@end defun
708
709@need 3000
710
711@node Pop-Up Menus
712@section Pop-Up Menus
713
714@defun x-popup-menu position menu
715This function displays a pop-up menu and returns an indication of
716what selection the user makes.
717
718The argument @var{position} specifies where on the screen to put the
719menu. It can be either a mouse button event (which says to put the menu
720where the user actuated the button) or a list of this form:
721
722@example
723((@var{xoffset} @var{yoffset}) @var{window})
724@end example
725
726@noindent
727where @var{xoffset} and @var{yoffset} are positions measured in
728characters, counting from the top left corner of @var{window}'s frame.
729
730If @var{position} is @code{t}, it means to use the current mouse
731position. If @var{position} is @code{nil}, it means to precompute the
732key binding equivalents for the keymaps specified in @var{menu},
733without actually displaying or popping up the menu.
734
735The argument @var{menu} says what to display in the menu. It can be a
736keymap or a list of keymaps (@pxref{Menu Keymaps}). Alternatively, it
737can have the following form:
738
739@example
740(@var{title} @var{pane1} @var{pane2}...)
741@end example
742
743@noindent
744where each pane is a list of form
745
746@example
747(@var{title} (@var{line} @var{item})...)
748@end example
749
750Each @var{line} should be a string, and each @var{item} should be the
751value to return if that @var{line} is chosen.
752@end defun
753
754@strong{Usage note:} Don't use @code{x-popup-menu} to display a menu if
755a prefix key with a menu keymap would do the job. If you use a menu
756keymap to implement a menu, @kbd{C-h c} and @kbd{C-h a} can see the
757individual items in that menu and provide help for them. If instead you
758implement the menu by defining a command that calls @code{x-popup-menu},
759the help facilities cannot know what happens inside that command, so
760they cannot give any help for the menu's items. This is the reason why
761all the menu bar items except @samp{Buffers} are implemented with menu
762keymaps (@pxref{Menu Keymaps}).
763
764@node Dialog Boxes
765@section Dialog Boxes
766@cindex dialog boxes
767
768 A dialog box is a variant of a pop-up menu. It looks a little
769different (if Emacs uses an X toolkit), it always appears in the center
770of a frame, and it has just one level and one pane. The main use of
771dialog boxes is for asking questions that the user can answer with
772``yes'', ``no'', and a few other alternatives. The functions
773@code{y-or-n-p} and @code{yes-or-no-p} use dialog boxes instead of the
774keyboard, when called from commands invoked by mouse clicks.
775
776@defun x-popup-dialog position contents
777This function displays a pop-up dialog box and returns an indication of
778what selection the user makes. The argument @var{contents} specifies
779the alternatives to offer; it has this format:
780
781@example
782(@var{title} (@var{string} @var{value})@dots{})
783@end example
784
785@noindent
786which looks like the list that specifies a single pane for
787@code{x-popup-menu}.
788
789Dialog boxes always appear in the center of a frame; the argument
790@var{position} specifies which frame. The possible values are as in
791@code{x-popup-menu}, but the precise coordinates don't matter; only the
792frame matters.
793@end defun
794
795@node X Selections
796@section X Selections
797@cindex selection (for X windows)
798
799The X server records a set of @dfn{selections} which permit transfer of
800data between application programs. The various selections are
801distinguished by @dfn{selection types}, represented in Emacs by
802symbols. X clients including Emacs can read or set the selection for
803any given type.
804
805@defun x-set-selection type data
806This function sets a ``selection'' in the X server. It takes two
807arguments: a selection type @var{type}, and the value to assign to it,
808@var{data}. If @var{data} is @code{nil}, it means to clear out the
809selection. Otherwise, @var{data} may be a string, a symbol, an integer
810(or a cons of two integers or list of two integers), an overlay, or a
811cons of two markers pointing to the same buffer. An overlay or a pair
812of markers stands for text in the overlay or between the markers.
813
814The data may also be a vector of valid non-vector selection values.
815
816Each possible @var{type} has its own selection value, which changes
817independently. The usual values of @var{type} are @code{PRIMARY} and
818@code{SECONDARY}; these are symbols with upper-case names, in accord
819with X Window System conventions. The default is @code{PRIMARY}.
820@end defun
821
822@defun x-get-selection type data-type
823This function accesses selections set up by Emacs or by other X
824clients. It takes two optional arguments, @var{type} and
825@var{data-type}. The default for @var{type}, the selection type, is
826@code{PRIMARY}.
827
828The @var{data-type} argument specifies the form of data conversion to
829use, to convert the raw data obtained from another X client into Lisp
830data. Meaningful values include @code{TEXT}, @code{STRING},
831@code{TARGETS}, @code{LENGTH}, @code{DELETE}, @code{FILE_NAME},
832@code{CHARACTER_POSITION}, @code{LINE_NUMBER}, @code{COLUMN_NUMBER},
833@code{OWNER_OS}, @code{HOST_NAME}, @code{USER}, @code{CLASS},
834@code{NAME}, @code{ATOM}, and @code{INTEGER}. (These are symbols with
835upper-case names in accord with X conventions.) The default for
836@var{data-type} is @code{STRING}.
837@end defun
838
839@cindex cut buffer
840The X server also has a set of numbered @dfn{cut buffers} which can
841store text or other data being moved between applications. Cut buffers
842are considered obsolete, but Emacs supports them for the sake of X
843clients that still use them.
844
845@defun x-get-cut-buffer n
846This function returns the contents of cut buffer number @var{n}.
847@end defun
848
849@defun x-set-cut-buffer string
850This function stores @var{string} into the first cut buffer (cut buffer
8510), moving the other values down through the series of cut buffers, much
852like the way successive kills in Emacs move down the kill ring.
853@end defun
854
855@node X Connections
856@section X Connections
857
858You can close the connection with the X server with the function
859@code{x-close-current-connection}, and open a new one with
860@code{x-open-connection} (perhaps with a different server and display).
861
862@defun x-close-current-connection
863This function closes the connection to the X server. It deletes all
864frames, making Emacs effectively inaccessible to the user; therefore, a
865Lisp program that closes the connection should open another one.
866@end defun
867
868@defun x-open-connection display &optional resource-string
869This function opens a connection to an X server, for use of display
870@var{display}.
871
872The optional argument @var{resource-string} is a string of resource
873names and values, in the same format used in the @file{.Xresources}
874file. The values you specify override the resource values recorded in
875the X server itself. Here's an example of what this string might look
876like:
877
878@example
879"*BorderWidth: 3\n*InternalBorder: 2\n"
880@end example
881
882@xref{Resources}.
883@end defun
884
885@defun x-display-color-p
886This returns @code{t} if the connected X display has color, and
887@code{nil} otherwise.
888@end defun
889
890@defun x-color-defined-p color
891This function reports whether a color name is meaningful and supported
892on the X display Emacs is using. It returns @code{t} if the display
893supports that color; otherwise, @code{nil}.
894
895Black-and-white displays support just two colors, @code{"black"} or
896@code{"white"}. Color displays support many other colors.
897@end defun
898
899@defun x-synchronize flag
900The function @code{x-synchronize} enables or disables synchronous
901communication with the X server. It enables synchronous communication
902if @var{flag} is non-@code{nil}, and disables it if @var{flag} is
903@code{nil}.
904
905In synchronous mode, Emacs waits for a response to each X protocol
906command before doing anything else. This is useful for debugging Emacs,
907because protocol errors are reported right away, which helps you find
908the erroneous command. Synchronous mode is not the default because it
909is much slower.
910@end defun
911
912@node Resources
913@section X Resources
914
915@defun x-get-resource attribute &optional name class
916The function @code{x-get-resource} retrieves a resource value from the X
917Windows defaults database.
918
919Resources are indexed by a combination of a @dfn{key} and a @dfn{class}.
920This function searches using a key of the form
921@samp{@var{instance}.@var{attribute}}, using the name under which Emacs
922was invoked as @var{instance}, and using @samp{Emacs} as the class.
923
924The optional arguments @var{component} and @var{subclass} add to the key
925and the class, respectively. You must specify both of them or neither.
926If you specify them, the key is
927@samp{@var{instance}.@var{component}.@var{attribute}}, and the class is
928@samp{Emacs.@var{subclass}}.
929@end defun
930
931 @xref{Resources X, X Resources,, emacs, The GNU Emacs Manual}.
932
933@node Server Data
934@section Data about the X Server
935
936 This section describes functions and a variable that you can use to
937get information about the capabilities and origin of the X server that
938Emacs is displaying its frames on.
939
940@defun x-display-screens
941This function returns the number of screens associated with the current
942display.
943@end defun
944
945@defun x-server-version
946This function returns the list of version numbers of the X server in
947use.
948@end defun
949
950@defun x-server-vendor
951This function returns the vendor supporting the X server in use.
952@end defun
953
954@defun x-display-pixel-height
955This function returns the height of this X screen in pixels.
956@end defun
957
958@defun x-display-mm-height
959This function returns the height of this X screen in millimeters.
960@end defun
961
962@defun x-display-pixel-width
963This function returns the width of this X screen in pixels.
964@end defun
965
966@defun x-display-mm-width
967This function returns the width of this X screen in millimeters.
968@end defun
969
970@defun x-display-backing-store
971This function returns the backing store capability of this screen.
972Values can be the symbols @code{always}, @code{when-mapped}, or
973@code{not-useful}.
974@end defun
975
976@defun x-display-save-under
977This function returns non-@code{nil} if this X screen supports the
978SaveUnder feature.
979@end defun
980
981@defun x-display-planes
982This function returns the number of planes this display supports.
983@end defun
984
985@defun x-display-visual-class
986This function returns the visual class for this X screen. The value is
987one of the symbols @code{static-gray}, @code{gray-scale},
988@code{static-color}, @code{pseudo-color}, @code{true-color}, and
989@code{direct-color}.
990@end defun
991
992@defun x-display-color-p
993This function returns @code{t} if the X screen in use is a color
994screen.
995@end defun
996
997@defun x-display-color-cells
998This function returns the number of color cells this X screen supports.
999@end defun
1000
1001@ignore
1002@defvar x-no-window-manager
1003This variable's value is is @code{t} if no X window manager is in use.
1004@end defvar
1005@end ignore
1006
1007@ignore
1008@item
1009The functions @code{x-pixel-width} and @code{x-pixel-height} return the
1010width and height of an X Window frame, measured in pixels.
1011
1012@item
1013x-pointer-shape, x-nontext-pointer-shape, x-mode-pointer-shape.
1014@end ignore