2 @c This is part of the GNU Emacs Lisp Reference Manual.
3 @c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2002, 2003,
4 @c 2004, 2005, 2006 Free Software Foundation, Inc.
5 @c See the file elisp.texi for copying conditions.
6 @setfilename ../info/frames
7 @node Frames, Positions, Windows, Top
11 A @dfn{frame} is a rectangle on the screen that contains one or more
12 Emacs windows. A frame initially contains a single main window (plus
13 perhaps a minibuffer window), which you can subdivide vertically or
14 horizontally into smaller windows.
16 @cindex terminal frame
17 When Emacs runs on a text-only terminal, it starts with one
18 @dfn{terminal frame}. If you create additional ones, Emacs displays
19 one and only one at any given time---on the terminal screen, of course.
22 When Emacs communicates directly with a supported window system, such
23 as X, it does not have a terminal frame; instead, it starts with
24 a single @dfn{window frame}, but you can create more, and Emacs can
25 display several such frames at once as is usual for window systems.
28 This predicate returns a non-@code{nil} value if @var{object} is a
29 frame, and @code{nil} otherwise. For a frame, the value indicates which
30 kind of display the frame uses:
34 The frame is displayed in an X window.
36 A terminal frame on a character display.
38 The frame is displayed on a Macintosh.
40 The frame is displayed on MS-Windows 9X/NT.
42 The frame is displayed on an MS-DOS terminal.
47 * Creating Frames:: Creating additional frames.
48 * Multiple Displays:: Creating frames on other displays.
49 * Frame Parameters:: Controlling frame size, position, font, etc.
50 * Frame Titles:: Automatic updating of frame titles.
51 * Deleting Frames:: Frames last until explicitly deleted.
52 * Finding All Frames:: How to examine all existing frames.
53 * Frames and Windows:: A frame contains windows;
54 display of text always works through windows.
55 * Minibuffers and Frames:: How a frame finds the minibuffer to use.
56 * Input Focus:: Specifying the selected frame.
57 * Visibility of Frames:: Frames may be visible or invisible, or icons.
58 * Raising and Lowering:: Raising a frame makes it hide other windows;
59 lowering it makes the others hide it.
60 * Frame Configurations:: Saving the state of all frames.
61 * Mouse Tracking:: Getting events that say when the mouse moves.
62 * Mouse Position:: Asking where the mouse is, or moving it.
63 * Pop-Up Menus:: Displaying a menu for the user to select from.
64 * Dialog Boxes:: Displaying a box to ask yes or no.
65 * Pointer Shape:: Specifying the shape of the mouse pointer.
66 * Window System Selections:: Transferring text to and from other X clients.
67 * Drag and Drop:: Internals of Drag-and-Drop implementation.
68 * Color Names:: Getting the definitions of color names.
69 * Text Terminal Colors:: Defining colors for text-only terminals.
70 * Resources:: Getting resource values from the server.
71 * Display Feature Testing:: Determining the features of a terminal.
74 @xref{Display}, for information about the related topic of
75 controlling Emacs redisplay.
78 @section Creating Frames
80 To create a new frame, call the function @code{make-frame}.
82 @defun make-frame &optional alist
83 This function creates and returns a new frame, displaying the current
84 buffer. If you are using a supported window system, it makes a window
85 frame; otherwise, it makes a terminal frame.
87 The argument is an alist specifying frame parameters. Any parameters
88 not mentioned in @var{alist} default according to the value of the
89 variable @code{default-frame-alist}; parameters not specified even there
90 default from the standard X resources or whatever is used instead on
93 The set of possible parameters depends in principle on what kind of
94 window system Emacs uses to display its frames. @xref{Window Frame
95 Parameters}, for documentation of individual parameters you can specify.
97 This function itself does not make the new frame the selected frame.
98 @xref{Input Focus}. The previously selected frame remains selected.
99 However, the window system may select the new frame for its own reasons,
100 for instance if the frame appears under the mouse pointer and your
101 setup is for focus to follow the pointer.
104 @defvar before-make-frame-hook
105 A normal hook run by @code{make-frame} before it actually creates the
109 @defvar after-make-frame-functions
110 An abnormal hook run by @code{make-frame} after it creates the frame.
111 Each function in @code{after-make-frame-functions} receives one argument, the
115 @node Multiple Displays
116 @section Multiple Displays
117 @cindex multiple X displays
118 @cindex displays, multiple
120 A single Emacs can talk to more than one X display.
121 Initially, Emacs uses just one display---the one chosen with the
122 @code{DISPLAY} environment variable or with the @samp{--display} option
123 (@pxref{Initial Options,,, emacs, The GNU Emacs Manual}). To connect to
124 another display, use the command @code{make-frame-on-display} or specify
125 the @code{display} frame parameter when you create the frame.
127 Emacs treats each X server as a separate terminal, giving each one its
128 own selected frame and its own minibuffer windows. However, only one of
129 those frames is ``@emph{the} selected frame'' at any given moment, see
132 A few Lisp variables are @dfn{terminal-local}; that is, they have a
133 separate binding for each terminal. The binding in effect at any time
134 is the one for the terminal that the currently selected frame belongs
135 to. These variables include @code{default-minibuffer-frame},
136 @code{defining-kbd-macro}, @code{last-kbd-macro}, and
137 @code{system-key-alist}. They are always terminal-local, and can never
138 be buffer-local (@pxref{Buffer-Local Variables}) or frame-local.
140 A single X server can handle more than one screen. A display name
141 @samp{@var{host}:@var{server}.@var{screen}} has three parts; the last
142 part specifies the screen number for a given server. When you use two
143 screens belonging to one server, Emacs knows by the similarity in their
144 names that they share a single keyboard, and it treats them as a single
147 @deffn Command make-frame-on-display display &optional parameters
148 This creates and returns a new frame on display @var{display}, taking
149 the other frame parameters from @var{parameters}. Aside from the
150 @var{display} argument, it is like @code{make-frame} (@pxref{Creating
154 @defun x-display-list
155 This returns a list that indicates which X displays Emacs has a
156 connection to. The elements of the list are strings, and each one is
160 @defun x-open-connection display &optional xrm-string must-succeed
161 This function opens a connection to the X display @var{display}. It
162 does not create a frame on that display, but it permits you to check
163 that communication can be established with that display.
165 The optional argument @var{xrm-string}, if not @code{nil}, is a
166 string of resource names and values, in the same format used in the
167 @file{.Xresources} file. The values you specify override the resource
168 values recorded in the X server itself; they apply to all Emacs frames
169 created on this display. Here's an example of what this string might
173 "*BorderWidth: 3\n*InternalBorder: 2\n"
176 @xref{X Resources,, X Resources, emacs, The GNU Emacs Manual}.
178 If @var{must-succeed} is non-@code{nil}, failure to open the connection
179 terminates Emacs. Otherwise, it is an ordinary Lisp error.
182 @defun x-close-connection display
183 This function closes the connection to display @var{display}. Before
184 you can do this, you must first delete all the frames that were open on
185 that display (@pxref{Deleting Frames}).
188 @node Frame Parameters
189 @section Frame Parameters
191 A frame has many parameters that control its appearance and behavior.
192 Just what parameters a frame has depends on what display mechanism it
195 Frame parameters exist mostly for the sake of window systems. A
196 terminal frame has a few parameters, mostly for compatibility's sake;
197 only the @code{height}, @code{width}, @code{name}, @code{title},
198 @code{menu-bar-lines}, @code{buffer-list} and @code{buffer-predicate}
199 parameters do something special. If the terminal supports colors, the
200 parameters @code{foreground-color}, @code{background-color},
201 @code{background-mode} and @code{display-type} are also meaningful.
204 * Parameter Access:: How to change a frame's parameters.
205 * Initial Parameters:: Specifying frame parameters when you make a frame.
206 * Window Frame Parameters:: List of frame parameters for window systems.
207 * Size and Position:: Changing the size and position of a frame.
208 * Geometry:: Parsing geometry specifications.
211 @node Parameter Access
212 @subsection Access to Frame Parameters
214 These functions let you read and change the parameter values of a
217 @defun frame-parameter frame parameter
218 This function returns the value of the parameter @var{parameter} (a
219 symbol) of @var{frame}. If @var{frame} is @code{nil}, it returns the
220 selected frame's parameter. If @var{frame} has no setting for
221 @var{parameter}, this function returns @code{nil}.
224 @defun frame-parameters &optional frame
225 The function @code{frame-parameters} returns an alist listing all the
226 parameters of @var{frame} and their values. If @var{frame} is
227 @code{nil} or omitted, this returns the selected frame's parameters
230 @defun modify-frame-parameters frame alist
231 This function alters the parameters of frame @var{frame} based on the
232 elements of @var{alist}. Each element of @var{alist} has the form
233 @code{(@var{parm} . @var{value})}, where @var{parm} is a symbol naming a
234 parameter. If you don't mention a parameter in @var{alist}, its value
235 doesn't change. If @var{frame} is @code{nil}, it defaults to the selected
239 @defun modify-all-frames-parameters alist
240 This function alters the frame parameters of all existing frames
241 according to @var{alist}, then modifies @code{default-frame-alist}
242 (and, if necessary, @code{initial-frame-alist}) to apply the same
243 parameter values to frames that will be created henceforth.
246 @node Initial Parameters
247 @subsection Initial Frame Parameters
249 You can specify the parameters for the initial startup frame
250 by setting @code{initial-frame-alist} in your init file (@pxref{Init File}).
252 @defvar initial-frame-alist
253 This variable's value is an alist of parameter values used when creating
254 the initial window frame. You can set this variable to specify the
255 appearance of the initial frame without altering subsequent frames.
256 Each element has the form:
259 (@var{parameter} . @var{value})
262 Emacs creates the initial frame before it reads your init
263 file. After reading that file, Emacs checks @code{initial-frame-alist},
264 and applies the parameter settings in the altered value to the already
265 created initial frame.
267 If these settings affect the frame geometry and appearance, you'll see
268 the frame appear with the wrong ones and then change to the specified
269 ones. If that bothers you, you can specify the same geometry and
270 appearance with X resources; those do take effect before the frame is
271 created. @xref{X Resources,, X Resources, emacs, The GNU Emacs Manual}.
273 X resource settings typically apply to all frames. If you want to
274 specify some X resources solely for the sake of the initial frame, and
275 you don't want them to apply to subsequent frames, here's how to achieve
276 this. Specify parameters in @code{default-frame-alist} to override the
277 X resources for subsequent frames; then, to prevent these from affecting
278 the initial frame, specify the same parameters in
279 @code{initial-frame-alist} with values that match the X resources.
282 If these parameters specify a separate minibuffer-only frame with
283 @code{(minibuffer . nil)}, and you have not created one, Emacs creates
286 @defvar minibuffer-frame-alist
287 This variable's value is an alist of parameter values used when creating
288 an initial minibuffer-only frame---if such a frame is needed, according
289 to the parameters for the main initial frame.
292 @defvar default-frame-alist
293 This is an alist specifying default values of frame parameters for all
294 Emacs frames---the first frame, and subsequent frames. When using the X
295 Window System, you can get the same results by means of X resources
298 Setting this variable does not affect existing frames.
301 See also @code{special-display-frame-alist}. @xref{Definition of
302 special-display-frame-alist}.
304 If you use options that specify window appearance when you invoke Emacs,
305 they take effect by adding elements to @code{default-frame-alist}. One
306 exception is @samp{-geometry}, which adds the specified position to
307 @code{initial-frame-alist} instead. @xref{Emacs Invocation,, Command
308 Line Arguments for Emacs Invocation, emacs, The GNU Emacs Manual}.
310 @node Window Frame Parameters
311 @subsection Window Frame Parameters
313 Just what parameters a frame has depends on what display mechanism
314 it uses. This section describes the parameters that have special
315 meanings on some or all kinds of terminals. Of these, @code{name},
316 @code{title}, @code{height}, @code{width}, @code{buffer-list} and
317 @code{buffer-predicate} provide meaningful information in terminal
318 frames, and @code{tty-color-mode} is meaningful @emph{only} in
322 * Basic Parameters:: Parameters that are fundamental.
323 * Position Parameters:: The position of the frame on the screen.
324 * Size Parameters:: Frame's size.
325 * Layout Parameters:: Size of parts of the frame, and
326 enabling or disabling some parts.
327 * Buffer Parameters:: Which buffers have been or should be shown.
328 * Management Parameters:: Communicating with the window manager.
329 * Cursor Parameters:: Controlling the cursor appearance.
330 * Color Parameters:: Colors of various parts of the frame.
333 @node Basic Parameters
334 @subsubsection Basic Parameters
336 These frame parameters give the most basic information about the
337 frame. @code{title} and @code{name} are meaningful on all terminals.
341 The display on which to open this frame. It should be a string of the
342 form @code{"@var{host}:@var{dpy}.@var{screen}"}, just like the
343 @code{DISPLAY} environment variable.
346 This parameter describes the range of possible colors that can be used
347 in this frame. Its value is @code{color}, @code{grayscale} or
351 If a frame has a non-@code{nil} title, it appears in the window system's
352 border for the frame, and also in the mode line of windows in that frame
353 if @code{mode-line-frame-identification} uses @samp{%F}
354 (@pxref{%-Constructs}). This is normally the case when Emacs is not
355 using a window system, and can only display one frame at a time.
359 The name of the frame. The frame name serves as a default for the frame
360 title, if the @code{title} parameter is unspecified or @code{nil}. If
361 you don't specify a name, Emacs sets the frame name automatically
362 (@pxref{Frame Titles}).
364 If you specify the frame name explicitly when you create the frame, the
365 name is also used (instead of the name of the Emacs executable) when
366 looking up X resources for the frame.
369 @node Position Parameters
370 @subsubsection Position Parameters
372 Position parameters' values are normally measured in pixels, but on
373 text-only terminals they count characters or lines instead.
377 The screen position of the left edge, in pixels, with respect to the
378 left edge of the screen. The value may be a positive number @var{pos},
379 or a list of the form @code{(+ @var{pos})} which permits specifying a
380 negative @var{pos} value.
382 A negative number @minus{}@var{pos}, or a list of the form @code{(-
383 @var{pos})}, actually specifies the position of the right edge of the
384 window with respect to the right edge of the screen. A positive value
385 of @var{pos} counts toward the left. @strong{Reminder:} if the
386 parameter is a negative integer @minus{}@var{pos}, then @var{pos} is
389 Some window managers ignore program-specified positions. If you want to
390 be sure the position you specify is not ignored, specify a
391 non-@code{nil} value for the @code{user-position} parameter as well.
394 The screen position of the top edge, in pixels, with respect to the
395 top edge of the screen. It works just like @code{left}, except vertically
396 instead of horizontally.
399 The screen position of the left edge @emph{of the frame's icon}, in
400 pixels, counting from the left edge of the screen. This takes effect if
401 and when the frame is iconified.
403 If you specify a value for this parameter, then you must also specify
404 a value for @code{icon-top} and vice versa. The window manager may
405 ignore these two parameters.
408 The screen position of the top edge @emph{of the frame's icon}, in
409 pixels, counting from the top edge of the screen. This takes effect if
410 and when the frame is iconified.
413 When you create a frame and specify its screen position with the
414 @code{left} and @code{top} parameters, use this parameter to say whether
415 the specified position was user-specified (explicitly requested in some
416 way by a human user) or merely program-specified (chosen by a program).
417 A non-@code{nil} value says the position was user-specified.
419 Window managers generally heed user-specified positions, and some heed
420 program-specified positions too. But many ignore program-specified
421 positions, placing the window in a default fashion or letting the user
422 place it with the mouse. Some window managers, including @code{twm},
423 let the user specify whether to obey program-specified positions or
426 When you call @code{make-frame}, you should specify a non-@code{nil}
427 value for this parameter if the values of the @code{left} and @code{top}
428 parameters represent the user's stated preference; otherwise, use
432 @node Size Parameters
433 @subsubsection Size Parameters
435 Size parameters' values are normally measured in pixels, but on
436 text-only terminals they count characters or lines instead.
440 The height of the frame contents, in characters. (To get the height in
441 pixels, call @code{frame-pixel-height}; see @ref{Size and Position}.)
444 The width of the frame contents, in characters. (To get the height in
445 pixels, call @code{frame-pixel-width}; see @ref{Size and Position}.)
448 This does for the size parameters @code{height} and @code{width} what
449 the @code{user-position} parameter (see above) does for the position
450 parameters @code{top} and @code{left}.
453 Specify that width, height or both shall be set to the size of the screen.
454 The value @code{fullwidth} specifies that width shall be the size of the
455 screen. The value @code{fullheight} specifies that height shall be the
456 size of the screen. The value @code{fullboth} specifies that both the
457 width and the height shall be set to the size of the screen.
460 @node Layout Parameters
461 @subsubsection Layout Parameters
463 These frame parameters enable or disable various parts of the
464 frame, or control their sizes.
468 The width in pixels of the frame's border.
470 @item internal-border-width
471 The distance in pixels between text (or fringe) and the frame's border.
473 @item vertical-scroll-bars
474 Whether the frame has scroll bars for vertical scrolling, and which side
475 of the frame they should be on. The possible values are @code{left},
476 @code{right}, and @code{nil} for no scroll bars.
479 @item horizontal-scroll-bars
480 Whether the frame has scroll bars for horizontal scrolling
481 (non-@code{nil} means yes). Horizontal scroll bars are not currently
485 @item scroll-bar-width
486 The width of vertical scroll bars, in pixels, or @code{nil} meaning to
487 use the default width.
491 The default width of the left and right fringes of windows in this
492 frame (@pxref{Fringes}). If either of these is zero, that effectively
493 removes the corresponding fringe. A value of @code{nil} stands for
494 the standard fringe width, which is the width needed to display the
497 The combined fringe widths must add up to an integral number of
498 columns, so the actual default fringe widths for the frame may be
499 larger than the specified values. The extra width needed to reach an
500 acceptable total is distributed evenly between the left and right
501 fringe. However, you can force one fringe or the other to a precise
502 width by specifying that width as a negative integer. If both widths are
503 negative, only the left fringe gets the specified width.
506 The number of lines to allocate at the top of the frame for a menu
507 bar. The default is 1. A value of @code{nil} means don't display a
508 menu bar. @xref{Menu Bar}. (The X toolkit and GTK allow at most one
509 menu bar line; they treat larger values as 1.)
512 The number of lines to use for the tool bar. A value of @code{nil}
513 means don't display a tool bar. (GTK allows at most one tool bar line;
514 it treats larger values as 1.)
517 Additional space to leave below each text line, in pixels (a positive
518 integer). @xref{Line Height}, for more information.
521 @node Buffer Parameters
522 @subsubsection Buffer Parameters
524 These frame parameters, meaningful on all kinds of terminals, deal
525 with which buffers have been, or should, be displayed in the frame.
529 Whether this frame has its own minibuffer. The value @code{t} means
530 yes, @code{nil} means no, @code{only} means this frame is just a
531 minibuffer. If the value is a minibuffer window (in some other frame),
532 the new frame uses that minibuffer.
534 @item buffer-predicate
535 The buffer-predicate function for this frame. The function
536 @code{other-buffer} uses this predicate (from the selected frame) to
537 decide which buffers it should consider, if the predicate is not
538 @code{nil}. It calls the predicate with one argument, a buffer, once for
539 each buffer; if the predicate returns a non-@code{nil} value, it
540 considers that buffer.
543 A list of buffers that have been selected in this frame,
544 ordered most-recently-selected first.
547 If non-@code{nil}, this frame's window is never split automatically.
550 @node Management Parameters
551 @subsubsection Window Management Parameters
553 These frame parameters, meaningful only on window system displays,
554 interact with the window manager.
558 The state of visibility of the frame. There are three possibilities:
559 @code{nil} for invisible, @code{t} for visible, and @code{icon} for
560 iconified. @xref{Visibility of Frames}.
563 Whether selecting the frame raises it (non-@code{nil} means yes).
566 Whether deselecting the frame lowers it (non-@code{nil} means yes).
569 The type of icon to use for this frame when it is iconified. If the
570 value is a string, that specifies a file containing a bitmap to use.
571 Any other non-@code{nil} value specifies the default bitmap icon (a
572 picture of a gnu); @code{nil} specifies a text icon.
575 The name to use in the icon for this frame, when and if the icon
576 appears. If this is @code{nil}, the frame's title is used.
579 The number of the window-system window used by the frame
580 to contain the actual Emacs windows.
582 @item outer-window-id
583 The number of the outermost window-system window used for the whole frame.
586 If non-@code{nil}, tell Xt to wait for the window manager to confirm
587 geometry changes. Some window managers, including versions of Fvwm2
588 and KDE, fail to confirm, so Xt hangs. Set this to @code{nil} to
589 prevent hanging with those window managers.
593 @c ??? Not yet working.
594 The X window number of the window that should be the parent of this one.
595 Specifying this lets you create an Emacs window inside some other
596 application's window. (It is not certain this will be implemented; try
597 it and see if it works.)
601 @node Cursor Parameters
602 @subsubsection Cursor Parameters
604 This frame parameter controls the way the cursor looks.
608 How to display the cursor. Legitimate values are:
612 Display a filled box. (This is the default.)
614 Display a hollow box.
616 Don't display a cursor.
618 Display a vertical bar between characters.
619 @item (bar . @var{width})
620 Display a vertical bar @var{width} pixels wide between characters.
622 Display a horizontal bar.
623 @item (hbar . @var{height})
624 Display a horizontal bar @var{height} pixels high.
629 The buffer-local variable @code{cursor-type} overrides the value of
630 the @code{cursor-type} frame parameter, but if it is @code{t}, that
631 means to use the cursor specified for the frame.
633 @defvar blink-cursor-alist
634 This variable specifies how to blink the cursor. Each element has the
635 form @code{(@var{on-state} . @var{off-state})}. Whenever the cursor
636 type equals @var{on-state} (comparing using @code{equal}), the
637 corresponding @var{off-state} specifies what the cursor looks like
638 when it blinks ``off''. Both @var{on-state} and @var{off-state}
639 should be suitable values for the @code{cursor-type} frame parameter.
641 There are various defaults for how to blink each type of cursor, if
642 the type is not mentioned as an @var{on-state} here. Changes in this
643 variable do not take effect immediately, because the variable is
644 examined only when you specify the @code{cursor-type} parameter.
647 @node Color Parameters
648 @subsubsection Color Parameters
650 These frame parameters control the use of colors.
653 @item background-mode
654 This parameter is either @code{dark} or @code{light}, according
655 to whether the background color is a light one or a dark one.
658 @cindex standard colors for character terminals
659 This parameter overrides the terminal's color support as given by the
660 system's terminal capabilities database in that this parameter's value
661 specifies the color mode to use in terminal frames. The value can be
662 either a symbol or a number. A number specifies the number of colors
663 to use (and, indirectly, what commands to issue to produce each
664 color). For example, @code{(tty-color-mode . 8)} specifies use of the
665 ANSI escape sequences for 8 standard text colors. A value of -1 turns
668 If the parameter's value is a symbol, it specifies a number through
669 the value of @code{tty-color-mode-alist}, and the associated number is
673 @cindex gamma correction
674 If this is a number, Emacs performs ``gamma correction'' which adjusts
675 the brightness of all colors. The value should be the screen gamma of
676 your display, a floating point number.
678 Usual PC monitors have a screen gamma of 2.2, so color values in
679 Emacs, and in X windows generally, are calibrated to display properly
680 on a monitor with that gamma value. If you specify 2.2 for
681 @code{screen-gamma}, that means no correction is needed. Other values
682 request correction, designed to make the corrected colors appear on
683 your screen the way they would have appeared without correction on an
684 ordinary monitor with a gamma value of 2.2.
686 If your monitor displays colors too light, you should specify a
687 @code{screen-gamma} value smaller than 2.2. This requests correction
688 that makes colors darker. A screen gamma value of 1.5 may give good
689 results for LCD color displays.
692 These frame parameters are semi-obsolete in that they are automatically
693 equivalent to particular face attributes of particular faces.
697 The name of the font for displaying text in the frame. This is a
698 string, either a valid font name for your system or the name of an Emacs
699 fontset (@pxref{Fontsets}). It is equivalent to the @code{font}
700 attribute of the @code{default} face.
702 @item foreground-color
703 The color to use for the image of a character. It is equivalent to
704 the @code{:foreground} attribute of the @code{default} face.
706 @item background-color
707 The color to use for the background of characters. It is equivalent to
708 the @code{:background} attribute of the @code{default} face.
711 The color for the mouse pointer. It is equivalent to the @code{:background}
712 attribute of the @code{mouse} face.
715 The color for the cursor that shows point. It is equivalent to the
716 @code{:background} attribute of the @code{cursor} face.
719 The color for the border of the frame. It is equivalent to the
720 @code{:background} attribute of the @code{border} face.
722 @item scroll-bar-foreground
723 If non-@code{nil}, the color for the foreground of scroll bars. It is
724 equivalent to the @code{:foreground} attribute of the
725 @code{scroll-bar} face.
727 @item scroll-bar-background
728 If non-@code{nil}, the color for the background of scroll bars. It is
729 equivalent to the @code{:background} attribute of the
730 @code{scroll-bar} face.
733 @node Size and Position
734 @subsection Frame Size And Position
735 @cindex size of frame
740 You can read or change the size and position of a frame using the
741 frame parameters @code{left}, @code{top}, @code{height}, and
742 @code{width}. Whatever geometry parameters you don't specify are chosen
743 by the window manager in its usual fashion.
745 Here are some special features for working with sizes and positions.
746 (For the precise meaning of ``selected frame'' used by these functions,
747 see @ref{Input Focus}.)
749 @defun set-frame-position frame left top
750 This function sets the position of the top left corner of @var{frame} to
751 @var{left} and @var{top}. These arguments are measured in pixels, and
752 normally count from the top left corner of the screen.
754 Negative parameter values position the bottom edge of the window up from
755 the bottom edge of the screen, or the right window edge to the left of
756 the right edge of the screen. It would probably be better if the values
757 were always counted from the left and top, so that negative arguments
758 would position the frame partly off the top or left edge of the screen,
759 but it seems inadvisable to change that now.
762 @defun frame-height &optional frame
763 @defunx frame-width &optional frame
764 These functions return the height and width of @var{frame}, measured in
765 lines and columns. If you don't supply @var{frame}, they use the
771 These functions are old aliases for @code{frame-height} and
772 @code{frame-width}. When you are using a non-window terminal, the size
773 of the frame is normally the same as the size of the terminal screen.
776 @defun frame-pixel-height &optional frame
777 @defunx frame-pixel-width &optional frame
778 These functions return the height and width of @var{frame}, measured in
779 pixels. If you don't supply @var{frame}, they use the selected frame.
782 @defun frame-char-height &optional frame
783 @defunx frame-char-width &optional frame
784 These functions return the height and width of a character in
785 @var{frame}, measured in pixels. The values depend on the choice of
786 font. If you don't supply @var{frame}, these functions use the selected
790 @defun set-frame-size frame cols rows
791 This function sets the size of @var{frame}, measured in characters;
792 @var{cols} and @var{rows} specify the new width and height.
794 To set the size based on values measured in pixels, use
795 @code{frame-char-height} and @code{frame-char-width} to convert
796 them to units of characters.
799 @defun set-frame-height frame lines &optional pretend
800 This function resizes @var{frame} to a height of @var{lines} lines. The
801 sizes of existing windows in @var{frame} are altered proportionally to
804 If @var{pretend} is non-@code{nil}, then Emacs displays @var{lines}
805 lines of output in @var{frame}, but does not change its value for the
806 actual height of the frame. This is only useful for a terminal frame.
807 Using a smaller height than the terminal actually implements may be
808 useful to reproduce behavior observed on a smaller screen, or if the
809 terminal malfunctions when using its whole screen. Setting the frame
810 height ``for real'' does not always work, because knowing the correct
811 actual size may be necessary for correct cursor positioning on a
815 @defun set-frame-width frame width &optional pretend
816 This function sets the width of @var{frame}, measured in characters.
817 The argument @var{pretend} has the same meaning as in
818 @code{set-frame-height}.
821 @findex set-screen-height
822 @findex set-screen-width
823 The older functions @code{set-screen-height} and
824 @code{set-screen-width} were used to specify the height and width of the
825 screen, in Emacs versions that did not support multiple frames. They
826 are semi-obsolete, but still work; they apply to the selected frame.
831 Here's how to examine the data in an X-style window geometry
834 @defun x-parse-geometry geom
835 @cindex geometry specification
836 The function @code{x-parse-geometry} converts a standard X window
837 geometry string to an alist that you can use as part of the argument to
840 The alist describes which parameters were specified in @var{geom}, and
841 gives the values specified for them. Each element looks like
842 @code{(@var{parameter} . @var{value})}. The possible @var{parameter}
843 values are @code{left}, @code{top}, @code{width}, and @code{height}.
845 For the size parameters, the value must be an integer. The position
846 parameter names @code{left} and @code{top} are not totally accurate,
847 because some values indicate the position of the right or bottom edges
848 instead. These are the @var{value} possibilities for the position
853 A positive integer relates the left edge or top edge of the window to
854 the left or top edge of the screen. A negative integer relates the
855 right or bottom edge of the window to the right or bottom edge of the
858 @item @code{(+ @var{position})}
859 This specifies the position of the left or top edge of the window
860 relative to the left or top edge of the screen. The integer
861 @var{position} may be positive or negative; a negative value specifies a
862 position outside the screen.
864 @item @code{(- @var{position})}
865 This specifies the position of the right or bottom edge of the window
866 relative to the right or bottom edge of the screen. The integer
867 @var{position} may be positive or negative; a negative value specifies a
868 position outside the screen.
874 (x-parse-geometry "35x70+0-0")
875 @result{} ((height . 70) (width . 35)
876 (top - 0) (left . 0))
881 @section Frame Titles
883 Every frame has a @code{name} parameter; this serves as the default
884 for the frame title which window systems typically display at the top of
885 the frame. You can specify a name explicitly by setting the @code{name}
888 Normally you don't specify the name explicitly, and Emacs computes the
889 frame name automatically based on a template stored in the variable
890 @code{frame-title-format}. Emacs recomputes the name each time the
891 frame is redisplayed.
893 @defvar frame-title-format
894 This variable specifies how to compute a name for a frame when you have
895 not explicitly specified one. The variable's value is actually a mode
896 line construct, just like @code{mode-line-format}. @xref{Mode Line
900 @defvar icon-title-format
901 This variable specifies how to compute the name for an iconified frame,
902 when you have not explicitly specified the frame title. This title
903 appears in the icon itself.
906 @defvar multiple-frames
907 This variable is set automatically by Emacs. Its value is @code{t} when
908 there are two or more frames (not counting minibuffer-only frames or
909 invisible frames). The default value of @code{frame-title-format} uses
910 @code{multiple-frames} so as to put the buffer name in the frame title
911 only when there is more than one frame.
913 The value of this variable is not guaranteed to be accurate except
914 while processing @code{frame-title-format} or
915 @code{icon-title-format}.
918 @node Deleting Frames
919 @section Deleting Frames
920 @cindex deletion of frames
922 Frames remain potentially visible until you explicitly @dfn{delete}
923 them. A deleted frame cannot appear on the screen, but continues to
924 exist as a Lisp object until there are no references to it.
926 @deffn Command delete-frame &optional frame force
927 @vindex delete-frame-functions
928 This function deletes the frame @var{frame}. Unless @var{frame} is a
929 tooltip, it first runs the hook @code{delete-frame-functions} (each
930 function gets one argument, @var{frame}). By default, @var{frame} is
933 A frame cannot be deleted if its minibuffer is used by other frames.
934 Normally, you cannot delete a frame if all other frames are invisible,
935 but if the @var{force} is non-@code{nil}, then you are allowed to do so.
938 @defun frame-live-p frame
939 The function @code{frame-live-p} returns non-@code{nil} if the frame
940 @var{frame} has not been deleted. The possible non-@code{nil} return
941 values are like those of @code{framep}. @xref{Frames}.
944 Some window managers provide a command to delete a window. These work
945 by sending a special message to the program that operates the window.
946 When Emacs gets one of these commands, it generates a
947 @code{delete-frame} event, whose normal definition is a command that
948 calls the function @code{delete-frame}. @xref{Misc Events}.
950 @node Finding All Frames
951 @section Finding All Frames
954 The function @code{frame-list} returns a list of all the frames that
955 have not been deleted. It is analogous to @code{buffer-list} for
956 buffers, and includes frames on all terminals. The list that you get is
957 newly created, so modifying the list doesn't have any effect on the
961 @defun visible-frame-list
962 This function returns a list of just the currently visible frames.
963 @xref{Visibility of Frames}. (Terminal frames always count as
964 ``visible'', even though only the selected one is actually displayed.)
967 @defun next-frame &optional frame minibuf
968 The function @code{next-frame} lets you cycle conveniently through all
969 the frames on the current display from an arbitrary starting point. It
970 returns the ``next'' frame after @var{frame} in the cycle. If
971 @var{frame} is omitted or @code{nil}, it defaults to the selected frame
972 (@pxref{Input Focus}).
974 The second argument, @var{minibuf}, says which frames to consider:
978 Exclude minibuffer-only frames.
980 Consider all visible frames.
982 Consider all visible or iconified frames.
984 Consider only the frames using that particular window as their
991 @defun previous-frame &optional frame minibuf
992 Like @code{next-frame}, but cycles through all frames in the opposite
996 See also @code{next-window} and @code{previous-window}, in @ref{Cyclic
999 @node Frames and Windows
1000 @section Frames and Windows
1002 Each window is part of one and only one frame; you can get the frame
1003 with @code{window-frame}.
1005 @defun window-frame window
1006 This function returns the frame that @var{window} is on.
1009 All the non-minibuffer windows in a frame are arranged in a cyclic
1010 order. The order runs from the frame's top window, which is at the
1011 upper left corner, down and to the right, until it reaches the window at
1012 the lower right corner (always the minibuffer window, if the frame has
1013 one), and then it moves back to the top. @xref{Cyclic Window Ordering}.
1015 @defun frame-first-window &optional frame
1016 This returns the topmost, leftmost window of frame @var{frame}.
1017 If omitted or @code{nil}, @var{frame} defaults to the selected frame.
1020 At any time, exactly one window on any frame is @dfn{selected within the
1021 frame}. The significance of this designation is that selecting the
1022 frame also selects this window. You can get the frame's current
1023 selected window with @code{frame-selected-window}.
1025 @defun frame-selected-window &optional frame
1026 This function returns the window on @var{frame} that is selected
1027 within @var{frame}. If omitted or @code{nil}, @var{frame} defaults to
1031 @defun set-frame-selected-window frame window
1032 This sets the selected window of frame @var{frame} to @var{window}.
1033 If @var{frame} is @code{nil}, it operates on the selected frame. If
1034 @var{frame} is the selected frame, this makes @var{window} the
1035 selected window. This function returns @var{window}.
1038 Conversely, selecting a window for Emacs with @code{select-window} also
1039 makes that window selected within its frame. @xref{Selecting Windows}.
1041 Another function that (usually) returns one of the windows in a given
1042 frame is @code{minibuffer-window}. @xref{Definition of minibuffer-window}.
1044 @node Minibuffers and Frames
1045 @section Minibuffers and Frames
1047 Normally, each frame has its own minibuffer window at the bottom, which
1048 is used whenever that frame is selected. If the frame has a minibuffer,
1049 you can get it with @code{minibuffer-window} (@pxref{Definition of
1050 minibuffer-window}).
1052 However, you can also create a frame with no minibuffer. Such a frame
1053 must use the minibuffer window of some other frame. When you create the
1054 frame, you can specify explicitly the minibuffer window to use (in some
1055 other frame). If you don't, then the minibuffer is found in the frame
1056 which is the value of the variable @code{default-minibuffer-frame}. Its
1057 value should be a frame that does have a minibuffer.
1059 If you use a minibuffer-only frame, you might want that frame to raise
1060 when you enter the minibuffer. If so, set the variable
1061 @code{minibuffer-auto-raise} to @code{t}. @xref{Raising and Lowering}.
1063 @defvar default-minibuffer-frame
1064 This variable specifies the frame to use for the minibuffer window, by
1065 default. It does not affect existing frames. It is always local to
1066 the current terminal and cannot be buffer-local. @xref{Multiple
1071 @section Input Focus
1073 @cindex selected frame
1075 At any time, one frame in Emacs is the @dfn{selected frame}. The selected
1076 window always resides on the selected frame.
1078 When Emacs displays its frames on several terminals (@pxref{Multiple
1079 Displays}), each terminal has its own selected frame. But only one of
1080 these is ``@emph{the} selected frame'': it's the frame that belongs to
1081 the terminal from which the most recent input came. That is, when Emacs
1082 runs a command that came from a certain terminal, the selected frame is
1083 the one of that terminal. Since Emacs runs only a single command at any
1084 given time, it needs to consider only one selected frame at a time; this
1085 frame is what we call @dfn{the selected frame} in this manual. The
1086 display on which the selected frame is displayed is the @dfn{selected
1089 @defun selected-frame
1090 This function returns the selected frame.
1093 Some window systems and window managers direct keyboard input to the
1094 window object that the mouse is in; others require explicit clicks or
1095 commands to @dfn{shift the focus} to various window objects. Either
1096 way, Emacs automatically keeps track of which frame has the focus. To
1097 switch to a different frame from a Lisp function, call
1098 @code{select-frame-set-input-focus}.
1100 Lisp programs can also switch frames ``temporarily'' by calling the
1101 function @code{select-frame}. This does not alter the window system's
1102 concept of focus; rather, it escapes from the window manager's control
1103 until that control is somehow reasserted.
1105 When using a text-only terminal, only one frame can be displayed at a
1106 time on the terminal, so after a call to @code{select-frame}, the next
1107 redisplay actually displays the newly selected frame. This frame
1108 remains selected until a subsequent call to @code{select-frame} or
1109 @code{select-frame-set-input-focus}. Each terminal frame has a number
1110 which appears in the mode line before the buffer name (@pxref{Mode
1113 @defun select-frame-set-input-focus frame
1114 This function makes @var{frame} the selected frame, raises it (should
1115 it happen to be obscured by other frames) and tries to give it the X
1116 server's focus. On a text-only terminal, the next redisplay displays
1117 the new frame on the entire terminal screen. The return value of this
1118 function is not significant.
1121 @c ??? This is not yet implemented properly.
1122 @defun select-frame frame
1123 This function selects frame @var{frame}, temporarily disregarding the
1124 focus of the X server if any. The selection of @var{frame} lasts until
1125 the next time the user does something to select a different frame, or
1126 until the next time this function is called. (If you are using a
1127 window system, the previously selected frame may be restored as the
1128 selected frame after return to the command loop, because it still may
1129 have the window system's input focus.) The specified @var{frame}
1130 becomes the selected frame, as explained above, and the terminal that
1131 @var{frame} is on becomes the selected terminal. This function
1132 returns @var{frame}, or @code{nil} if @var{frame} has been deleted.
1134 In general, you should never use @code{select-frame} in a way that could
1135 switch to a different terminal without switching back when you're done.
1138 Emacs cooperates with the window system by arranging to select frames as
1139 the server and window manager request. It does so by generating a
1140 special kind of input event, called a @dfn{focus} event, when
1141 appropriate. The command loop handles a focus event by calling
1142 @code{handle-switch-frame}. @xref{Focus Events}.
1144 @deffn Command handle-switch-frame frame
1145 This function handles a focus event by selecting frame @var{frame}.
1147 Focus events normally do their job by invoking this command.
1148 Don't call it for any other reason.
1151 @defun redirect-frame-focus frame &optional focus-frame
1152 This function redirects focus from @var{frame} to @var{focus-frame}.
1153 This means that @var{focus-frame} will receive subsequent keystrokes and
1154 events intended for @var{frame}. After such an event, the value of
1155 @code{last-event-frame} will be @var{focus-frame}. Also, switch-frame
1156 events specifying @var{frame} will instead select @var{focus-frame}.
1158 If @var{focus-frame} is omitted or @code{nil}, that cancels any existing
1159 redirection for @var{frame}, which therefore once again receives its own
1162 One use of focus redirection is for frames that don't have minibuffers.
1163 These frames use minibuffers on other frames. Activating a minibuffer
1164 on another frame redirects focus to that frame. This puts the focus on
1165 the minibuffer's frame, where it belongs, even though the mouse remains
1166 in the frame that activated the minibuffer.
1168 Selecting a frame can also change focus redirections. Selecting frame
1169 @code{bar}, when @code{foo} had been selected, changes any redirections
1170 pointing to @code{foo} so that they point to @code{bar} instead. This
1171 allows focus redirection to work properly when the user switches from
1172 one frame to another using @code{select-window}.
1174 This means that a frame whose focus is redirected to itself is treated
1175 differently from a frame whose focus is not redirected.
1176 @code{select-frame} affects the former but not the latter.
1178 The redirection lasts until @code{redirect-frame-focus} is called to
1182 @defopt focus-follows-mouse
1183 This option is how you inform Emacs whether the window manager transfers
1184 focus when the user moves the mouse. Non-@code{nil} says that it does.
1185 When this is so, the command @code{other-frame} moves the mouse to a
1186 position consistent with the new selected frame.
1189 @node Visibility of Frames
1190 @section Visibility of Frames
1191 @cindex visible frame
1192 @cindex invisible frame
1193 @cindex iconified frame
1194 @cindex frame visibility
1196 A window frame may be @dfn{visible}, @dfn{invisible}, or
1197 @dfn{iconified}. If it is visible, you can see its contents. If it is
1198 iconified, the frame's contents do not appear on the screen, but an icon
1199 does. If the frame is invisible, it doesn't show on the screen, not
1202 Visibility is meaningless for terminal frames, since only the selected
1203 one is actually displayed in any case.
1205 @deffn Command make-frame-visible &optional frame
1206 This function makes frame @var{frame} visible. If you omit @var{frame},
1207 it makes the selected frame visible.
1210 @deffn Command make-frame-invisible &optional frame force
1211 This function makes frame @var{frame} invisible. If you omit
1212 @var{frame}, it makes the selected frame invisible.
1214 Unless @var{force} is non-@code{nil}, this function refuses to make
1215 @var{frame} invisible if all other frames are invisible..
1218 @deffn Command iconify-frame &optional frame
1219 This function iconifies frame @var{frame}. If you omit @var{frame}, it
1220 iconifies the selected frame.
1223 @defun frame-visible-p frame
1224 This returns the visibility status of frame @var{frame}. The value is
1225 @code{t} if @var{frame} is visible, @code{nil} if it is invisible, and
1226 @code{icon} if it is iconified.
1228 On a text-only terminal, all frames are considered visible, whether
1229 they are currently being displayed or not, and this function returns
1230 @code{t} for all frames.
1233 The visibility status of a frame is also available as a frame
1234 parameter. You can read or change it as such. @xref{Management
1237 The user can iconify and deiconify frames with the window manager.
1238 This happens below the level at which Emacs can exert any control, but
1239 Emacs does provide events that you can use to keep track of such
1240 changes. @xref{Misc Events}.
1242 @node Raising and Lowering
1243 @section Raising and Lowering Frames
1245 Most window systems use a desktop metaphor. Part of this metaphor is
1246 the idea that windows are stacked in a notional third dimension
1247 perpendicular to the screen surface, and thus ordered from ``highest''
1248 to ``lowest''. Where two windows overlap, the one higher up covers
1249 the one underneath. Even a window at the bottom of the stack can be
1250 seen if no other window overlaps it.
1252 @cindex raising a frame
1253 @cindex lowering a frame
1254 A window's place in this ordering is not fixed; in fact, users tend
1255 to change the order frequently. @dfn{Raising} a window means moving
1256 it ``up'', to the top of the stack. @dfn{Lowering} a window means
1257 moving it to the bottom of the stack. This motion is in the notional
1258 third dimension only, and does not change the position of the window
1261 You can raise and lower Emacs frame Windows with these functions:
1263 @deffn Command raise-frame &optional frame
1264 This function raises frame @var{frame} (default, the selected frame).
1265 If @var{frame} is invisible or iconified, this makes it visible.
1268 @deffn Command lower-frame &optional frame
1269 This function lowers frame @var{frame} (default, the selected frame).
1272 @defopt minibuffer-auto-raise
1273 If this is non-@code{nil}, activation of the minibuffer raises the frame
1274 that the minibuffer window is in.
1277 You can also enable auto-raise (raising automatically when a frame is
1278 selected) or auto-lower (lowering automatically when it is deselected)
1279 for any frame using frame parameters. @xref{Management Parameters}.
1281 @node Frame Configurations
1282 @section Frame Configurations
1283 @cindex frame configuration
1285 A @dfn{frame configuration} records the current arrangement of frames,
1286 all their properties, and the window configuration of each one.
1287 (@xref{Window Configurations}.)
1289 @defun current-frame-configuration
1290 This function returns a frame configuration list that describes
1291 the current arrangement of frames and their contents.
1294 @defun set-frame-configuration configuration &optional nodelete
1295 This function restores the state of frames described in
1296 @var{configuration}. However, this function does not restore deleted
1299 Ordinarily, this function deletes all existing frames not listed in
1300 @var{configuration}. But if @var{nodelete} is non-@code{nil}, the
1301 unwanted frames are iconified instead.
1304 @node Mouse Tracking
1305 @section Mouse Tracking
1306 @cindex mouse tracking
1307 @cindex tracking the mouse
1309 Sometimes it is useful to @dfn{track} the mouse, which means to display
1310 something to indicate where the mouse is and move the indicator as the
1311 mouse moves. For efficient mouse tracking, you need a way to wait until
1312 the mouse actually moves.
1314 The convenient way to track the mouse is to ask for events to represent
1315 mouse motion. Then you can wait for motion by waiting for an event. In
1316 addition, you can easily handle any other sorts of events that may
1317 occur. That is useful, because normally you don't want to track the
1318 mouse forever---only until some other event, such as the release of a
1321 @defspec track-mouse body@dots{}
1322 This special form executes @var{body}, with generation of mouse motion
1323 events enabled. Typically @var{body} would use @code{read-event} to
1324 read the motion events and modify the display accordingly. @xref{Motion
1325 Events}, for the format of mouse motion events.
1327 The value of @code{track-mouse} is that of the last form in @var{body}.
1328 You should design @var{body} to return when it sees the up-event that
1329 indicates the release of the button, or whatever kind of event means
1330 it is time to stop tracking.
1333 The usual purpose of tracking mouse motion is to indicate on the screen
1334 the consequences of pushing or releasing a button at the current
1337 In many cases, you can avoid the need to track the mouse by using
1338 the @code{mouse-face} text property (@pxref{Special Properties}).
1339 That works at a much lower level and runs more smoothly than
1340 Lisp-level mouse tracking.
1343 @c These are not implemented yet.
1345 These functions change the screen appearance instantaneously. The
1346 effect is transient, only until the next ordinary Emacs redisplay. That
1347 is OK for mouse tracking, since it doesn't make sense for mouse tracking
1348 to change the text, and the body of @code{track-mouse} normally reads
1349 the events itself and does not do redisplay.
1351 @defun x-contour-region window beg end
1352 This function draws lines to make a box around the text from @var{beg}
1353 to @var{end}, in window @var{window}.
1356 @defun x-uncontour-region window beg end
1357 This function erases the lines that would make a box around the text
1358 from @var{beg} to @var{end}, in window @var{window}. Use it to remove
1359 a contour that you previously made by calling @code{x-contour-region}.
1362 @defun x-draw-rectangle frame left top right bottom
1363 This function draws a hollow rectangle on frame @var{frame} with the
1364 specified edge coordinates, all measured in pixels from the inside top
1365 left corner. It uses the cursor color, the one used for indicating the
1369 @defun x-erase-rectangle frame left top right bottom
1370 This function erases a hollow rectangle on frame @var{frame} with the
1371 specified edge coordinates, all measured in pixels from the inside top
1372 left corner. Erasure means redrawing the text and background that
1373 normally belong in the specified rectangle.
1377 @node Mouse Position
1378 @section Mouse Position
1379 @cindex mouse position
1380 @cindex position of mouse
1382 The functions @code{mouse-position} and @code{set-mouse-position}
1383 give access to the current position of the mouse.
1385 @defun mouse-position
1386 This function returns a description of the position of the mouse. The
1387 value looks like @code{(@var{frame} @var{x} . @var{y})}, where @var{x}
1388 and @var{y} are integers giving the position in characters relative to
1389 the top left corner of the inside of @var{frame}.
1392 @defvar mouse-position-function
1393 If non-@code{nil}, the value of this variable is a function for
1394 @code{mouse-position} to call. @code{mouse-position} calls this
1395 function just before returning, with its normal return value as the
1396 sole argument, and it returns whatever this function returns to it.
1398 This abnormal hook exists for the benefit of packages like
1399 @file{xt-mouse.el} that need to do mouse handling at the Lisp level.
1402 @defun set-mouse-position frame x y
1403 This function @dfn{warps the mouse} to position @var{x}, @var{y} in
1404 frame @var{frame}. The arguments @var{x} and @var{y} are integers,
1405 giving the position in characters relative to the top left corner of the
1406 inside of @var{frame}. If @var{frame} is not visible, this function
1407 does nothing. The return value is not significant.
1410 @defun mouse-pixel-position
1411 This function is like @code{mouse-position} except that it returns
1412 coordinates in units of pixels rather than units of characters.
1415 @defun set-mouse-pixel-position frame x y
1416 This function warps the mouse like @code{set-mouse-position} except that
1417 @var{x} and @var{y} are in units of pixels rather than units of
1418 characters. These coordinates are not required to be within the frame.
1420 If @var{frame} is not visible, this function does nothing. The return
1421 value is not significant.
1427 @section Pop-Up Menus
1429 When using a window system, a Lisp program can pop up a menu so that
1430 the user can choose an alternative with the mouse.
1432 @defun x-popup-menu position menu
1433 This function displays a pop-up menu and returns an indication of
1434 what selection the user makes.
1436 The argument @var{position} specifies where on the screen to put the
1437 top left corner of the menu. It can be either a mouse button event
1438 (which says to put the menu where the user actuated the button) or a
1442 ((@var{xoffset} @var{yoffset}) @var{window})
1446 where @var{xoffset} and @var{yoffset} are coordinates, measured in
1447 pixels, counting from the top left corner of @var{window}. @var{window}
1448 may be a window or a frame.
1450 If @var{position} is @code{t}, it means to use the current mouse
1451 position. If @var{position} is @code{nil}, it means to precompute the
1452 key binding equivalents for the keymaps specified in @var{menu},
1453 without actually displaying or popping up the menu.
1455 The argument @var{menu} says what to display in the menu. It can be a
1456 keymap or a list of keymaps (@pxref{Menu Keymaps}). In this case, the
1457 return value is the list of events corresponding to the user's choice.
1458 (This list has more than one element if the choice occurred in a
1459 submenu.) Note that @code{x-popup-menu} does not actually execute the
1460 command bound to that sequence of events.
1462 Alternatively, @var{menu} can have the following form:
1465 (@var{title} @var{pane1} @var{pane2}...)
1469 where each pane is a list of form
1472 (@var{title} @var{item1} @var{item2}...)
1475 Each item should normally be a cons cell @code{(@var{line} . @var{value})},
1476 where @var{line} is a string, and @var{value} is the value to return if
1477 that @var{line} is chosen. An item can also be a string; this makes a
1478 non-selectable line in the menu.
1480 If the user gets rid of the menu without making a valid choice, for
1481 instance by clicking the mouse away from a valid choice or by typing
1482 keyboard input, then this normally results in a quit and
1483 @code{x-popup-menu} does not return. But if @var{position} is a mouse
1484 button event (indicating that the user invoked the menu with the
1485 mouse) then no quit occurs and @code{x-popup-menu} returns @code{nil}.
1488 @strong{Usage note:} Don't use @code{x-popup-menu} to display a menu
1489 if you could do the job with a prefix key defined with a menu keymap.
1490 If you use a menu keymap to implement a menu, @kbd{C-h c} and @kbd{C-h
1491 a} can see the individual items in that menu and provide help for them.
1492 If instead you implement the menu by defining a command that calls
1493 @code{x-popup-menu}, the help facilities cannot know what happens inside
1494 that command, so they cannot give any help for the menu's items.
1496 The menu bar mechanism, which lets you switch between submenus by
1497 moving the mouse, cannot look within the definition of a command to see
1498 that it calls @code{x-popup-menu}. Therefore, if you try to implement a
1499 submenu using @code{x-popup-menu}, it cannot work with the menu bar in
1500 an integrated fashion. This is why all menu bar submenus are
1501 implemented with menu keymaps within the parent menu, and never with
1502 @code{x-popup-menu}. @xref{Menu Bar}.
1504 If you want a menu bar submenu to have contents that vary, you should
1505 still use a menu keymap to implement it. To make the contents vary, add
1506 a hook function to @code{menu-bar-update-hook} to update the contents of
1507 the menu keymap as necessary.
1510 @section Dialog Boxes
1511 @cindex dialog boxes
1513 A dialog box is a variant of a pop-up menu---it looks a little
1514 different, it always appears in the center of a frame, and it has just
1515 one level and one or more buttons. The main use of dialog boxes is
1516 for asking questions that the user can answer with ``yes'', ``no'',
1517 and a few other alternatives. With a single button, they can also
1518 force the user to acknowledge important information. The functions
1519 @code{y-or-n-p} and @code{yes-or-no-p} use dialog boxes instead of the
1520 keyboard, when called from commands invoked by mouse clicks.
1522 @defun x-popup-dialog position contents &optional header
1523 This function displays a pop-up dialog box and returns an indication of
1524 what selection the user makes. The argument @var{contents} specifies
1525 the alternatives to offer; it has this format:
1528 (@var{title} (@var{string} . @var{value})@dots{})
1532 which looks like the list that specifies a single pane for
1533 @code{x-popup-menu}.
1535 The return value is @var{value} from the chosen alternative.
1537 As for @code{x-popup-menu}, an element of the list may be just a
1538 string instead of a cons cell @code{(@var{string} . @var{value})}.
1539 That makes a box that cannot be selected.
1541 If @code{nil} appears in the list, it separates the left-hand items from
1542 the right-hand items; items that precede the @code{nil} appear on the
1543 left, and items that follow the @code{nil} appear on the right. If you
1544 don't include a @code{nil} in the list, then approximately half the
1545 items appear on each side.
1547 Dialog boxes always appear in the center of a frame; the argument
1548 @var{position} specifies which frame. The possible values are as in
1549 @code{x-popup-menu}, but the precise coordinates or the individual
1550 window don't matter; only the frame matters.
1552 If @var{header} is non-@code{nil}, the frame title for the box is
1553 @samp{Information}, otherwise it is @samp{Question}. The former is used
1554 for @code{message-box} (@pxref{The Echo Area}).
1556 In some configurations, Emacs cannot display a real dialog box; so
1557 instead it displays the same items in a pop-up menu in the center of the
1560 If the user gets rid of the dialog box without making a valid choice,
1561 for instance using the window manager, then this produces a quit and
1562 @code{x-popup-dialog} does not return.
1566 @section Pointer Shape
1567 @cindex pointer shape
1568 @cindex mouse pointer shape
1570 You can specify the mouse pointer style for particular text or
1571 images using the @code{pointer} text property, and for images with the
1572 @code{:pointer} and @code{:map} image properties. The values you can
1573 use in these properties are @code{text} (or @code{nil}), @code{arrow},
1574 @code{hand}, @code{vdrag}, @code{hdrag}, @code{modeline}, and
1575 @code{hourglass}. @code{text} stands for the usual mouse pointer
1576 style used over text.
1578 Over void parts of the window (parts that do not correspond to any
1579 of the buffer contents), the mouse pointer usually uses the
1580 @code{arrow} style, but you can specify a different style (one of
1581 those above) by setting @code{void-text-area-pointer}.
1583 @defvar void-text-area-pointer
1584 This variable specifies the mouse pointer style for void text areas.
1585 These include the areas after the end of a line or below the last line
1586 in the buffer. The default is to use the @code{arrow} (non-text)
1590 You can specify what the @code{text} pointer style really looks like
1591 by setting the variable @code{x-pointer-shape}.
1593 @defvar x-pointer-shape
1594 This variable specifies the pointer shape to use ordinarily in the
1595 Emacs frame, for the @code{text} pointer style.
1598 @defvar x-sensitive-text-pointer-shape
1599 This variable specifies the pointer shape to use when the mouse
1600 is over mouse-sensitive text.
1603 These variables affect newly created frames. They do not normally
1604 affect existing frames; however, if you set the mouse color of a
1605 frame, that also installs the current value of those two variables.
1606 @xref{Color Parameters}.
1608 The values you can use, to specify either of these pointer shapes, are
1609 defined in the file @file{lisp/term/x-win.el}. Use @kbd{M-x apropos
1610 @key{RET} x-pointer @key{RET}} to see a list of them.
1612 @node Window System Selections
1613 @section Window System Selections
1614 @cindex selection (for window systems)
1616 The X server records a set of @dfn{selections} which permit transfer of
1617 data between application programs. The various selections are
1618 distinguished by @dfn{selection types}, represented in Emacs by
1619 symbols. X clients including Emacs can read or set the selection for
1622 @deffn Command x-set-selection type data
1623 This function sets a ``selection'' in the X server. It takes two
1624 arguments: a selection type @var{type}, and the value to assign to it,
1625 @var{data}. If @var{data} is @code{nil}, it means to clear out the
1626 selection. Otherwise, @var{data} may be a string, a symbol, an integer
1627 (or a cons of two integers or list of two integers), an overlay, or a
1628 cons of two markers pointing to the same buffer. An overlay or a pair
1629 of markers stands for text in the overlay or between the markers.
1631 The argument @var{data} may also be a vector of valid non-vector
1634 Each possible @var{type} has its own selection value, which changes
1635 independently. The usual values of @var{type} are @code{PRIMARY},
1636 @code{SECONDARY} and @code{CLIPBOARD}; these are symbols with upper-case
1637 names, in accord with X Window System conventions. If @var{type} is
1638 @code{nil}, that stands for @code{PRIMARY}.
1640 This function returns @var{data}.
1643 @defun x-get-selection &optional type data-type
1644 This function accesses selections set up by Emacs or by other X
1645 clients. It takes two optional arguments, @var{type} and
1646 @var{data-type}. The default for @var{type}, the selection type, is
1649 The @var{data-type} argument specifies the form of data conversion to
1650 use, to convert the raw data obtained from another X client into Lisp
1651 data. Meaningful values include @code{TEXT}, @code{STRING},
1652 @code{UTF8_STRING}, @code{TARGETS}, @code{LENGTH}, @code{DELETE},
1653 @code{FILE_NAME}, @code{CHARACTER_POSITION}, @code{NAME},
1654 @code{LINE_NUMBER}, @code{COLUMN_NUMBER}, @code{OWNER_OS},
1655 @code{HOST_NAME}, @code{USER}, @code{CLASS}, @code{ATOM}, and
1656 @code{INTEGER}. (These are symbols with upper-case names in accord
1657 with X conventions.) The default for @var{data-type} is
1662 The X server also has a set of eight numbered @dfn{cut buffers} which can
1663 store text or other data being moved between applications. Cut buffers
1664 are considered obsolete, but Emacs supports them for the sake of X
1665 clients that still use them. Cut buffers are numbered from 0 to 7.
1667 @defun x-get-cut-buffer &optional n
1668 This function returns the contents of cut buffer number @var{n}.
1669 If omitted @var{n} defaults to 0.
1672 @defun x-set-cut-buffer string &optional push
1673 @anchor{Definition of x-set-cut-buffer}
1674 This function stores @var{string} into the first cut buffer (cut buffer
1675 0). If @var{push} is @code{nil}, only the first cut buffer is changed.
1676 If @var{push} is non-@code{nil}, that says to move the values down
1677 through the series of cut buffers, much like the way successive kills in
1678 Emacs move down the kill ring. In other words, the previous value of
1679 the first cut buffer moves into the second cut buffer, and the second to
1680 the third, and so on through all eight cut buffers.
1683 @defvar selection-coding-system
1684 This variable specifies the coding system to use when reading and
1685 writing selections, the clipboard, or a cut buffer. @xref{Coding
1686 Systems}. The default is @code{compound-text-with-extensions}, which
1687 converts to the text representation that X11 normally uses.
1690 @cindex clipboard support (for MS-Windows)
1691 When Emacs runs on MS-Windows, it does not implement X selections in
1692 general, but it does support the clipboard. @code{x-get-selection}
1693 and @code{x-set-selection} on MS-Windows support the text data type
1694 only; if the clipboard holds other types of data, Emacs treats the
1697 @cindex scrap support (for Mac OS)
1698 On Mac OS, selection-like data transfer between applications is
1699 performed through a mechanism called @dfn{scraps}. The clipboard is a
1700 particular scrap named @code{com.apple.scrap.clipboard}. Types of scrap
1701 data are called @dfn{scrap flavor types}, which are identified by
1702 four-char codes such as @code{TEXT}. Emacs associates a selection with
1703 a scrap, and a selection type with a scrap flavor type via
1704 @code{mac-scrap-name} and @code{mac-ostype} properties, respectively.
1707 (get 'CLIPBOARD 'mac-scrap-name)
1708 @result{} "com.apple.scrap.clipboard"
1709 (get 'com.apple.traditional-mac-plain-text 'mac-ostype)
1713 Conventionally, selection types for scrap flavor types on Mac OS have
1714 the form of @acronym{UTI, Uniform Type Identifier} such as
1715 @code{com.apple.traditional-mac-plain-text},
1716 @code{public.utf16-plain-text}, and @code{public.file-url}.
1718 @defopt x-select-enable-clipboard
1719 If this is non-@code{nil}, the Emacs yank functions consult the
1720 clipboard before the primary selection, and the kill functions store in
1721 the clipboard as well as the primary selection. Otherwise they do not
1722 access the clipboard at all. The default is @code{nil} on most systems,
1723 but @code{t} on MS-Windows and Mac.
1727 @section Drag and Drop
1729 @vindex x-dnd-test-function
1730 @vindex x-dnd-known-types
1731 When a user drags something from another application over Emacs, that other
1732 application expects Emacs to tell it if Emacs can handle the data that is
1733 dragged. The variable @code{x-dnd-test-function} is used by Emacs to determine
1734 what to reply. The default value is @code{x-dnd-default-test-function}
1735 which accepts drops if the type of the data to be dropped is present in
1736 @code{x-dnd-known-types}. You can customize @code{x-dnd-test-function} and/or
1737 @code{x-dnd-known-types} if you want Emacs to accept or reject drops based
1738 on some other criteria.
1740 @vindex x-dnd-types-alist
1741 If you want to change the way Emacs handles drop of different types
1742 or add a new type, customize @code{x-dnd-types-alist}. This requires
1743 detailed knowledge of what types other applications use for drag and
1746 @vindex dnd-protocol-alist
1747 When an URL is dropped on Emacs it may be a file, but it may also be
1748 another URL type (ftp, http, etc.). Emacs first checks
1749 @code{dnd-protocol-alist} to determine what to do with the URL. If
1750 there is no match there and if @code{browse-url-browser-function} is
1751 an alist, Emacs looks for a match there. If no match is found the
1752 text for the URL is inserted. If you want to alter Emacs behavior,
1753 you can customize these variables.
1756 @section Color Names
1759 @cindex specify color
1760 @cindex numerical RGB color specification
1761 A color name is text (usually in a string) that specifies a color.
1762 Symbolic names such as @samp{black}, @samp{white}, @samp{red}, etc.,
1763 are allowed; use @kbd{M-x list-colors-display} to see a list of
1764 defined names. You can also specify colors numerically in forms such
1765 as @samp{#@var{rgb}} and @samp{RGB:@var{r}/@var{g}/@var{b}}, where
1766 @var{r} specifies the red level, @var{g} specifies the green level,
1767 and @var{b} specifies the blue level. You can use either one, two,
1768 three, or four hex digits for @var{r}; then you must use the same
1769 number of hex digits for all @var{g} and @var{b} as well, making
1770 either 3, 6, 9 or 12 hex digits in all. (See the documentation of the
1771 X Window System for more details about numerical RGB specification of
1774 These functions provide a way to determine which color names are
1775 valid, and what they look like. In some cases, the value depends on the
1776 @dfn{selected frame}, as described below; see @ref{Input Focus}, for the
1777 meaning of the term ``selected frame''.
1779 @defun color-defined-p color &optional frame
1780 This function reports whether a color name is meaningful. It returns
1781 @code{t} if so; otherwise, @code{nil}. The argument @var{frame} says
1782 which frame's display to ask about; if @var{frame} is omitted or
1783 @code{nil}, the selected frame is used.
1785 Note that this does not tell you whether the display you are using
1786 really supports that color. When using X, you can ask for any defined
1787 color on any kind of display, and you will get some result---typically,
1788 the closest it can do. To determine whether a frame can really display
1789 a certain color, use @code{color-supported-p} (see below).
1791 @findex x-color-defined-p
1792 This function used to be called @code{x-color-defined-p},
1793 and that name is still supported as an alias.
1796 @defun defined-colors &optional frame
1797 This function returns a list of the color names that are defined
1798 and supported on frame @var{frame} (default, the selected frame).
1799 If @var{frame} does not support colors, the value is @code{nil}.
1801 @findex x-defined-colors
1802 This function used to be called @code{x-defined-colors},
1803 and that name is still supported as an alias.
1806 @defun color-supported-p color &optional frame background-p
1807 This returns @code{t} if @var{frame} can really display the color
1808 @var{color} (or at least something close to it). If @var{frame} is
1809 omitted or @code{nil}, the question applies to the selected frame.
1811 Some terminals support a different set of colors for foreground and
1812 background. If @var{background-p} is non-@code{nil}, that means you are
1813 asking whether @var{color} can be used as a background; otherwise you
1814 are asking whether it can be used as a foreground.
1816 The argument @var{color} must be a valid color name.
1819 @defun color-gray-p color &optional frame
1820 This returns @code{t} if @var{color} is a shade of gray, as defined on
1821 @var{frame}'s display. If @var{frame} is omitted or @code{nil}, the
1822 question applies to the selected frame. If @var{color} is not a valid
1823 color name, this function returns @code{nil}.
1826 @defun color-values color &optional frame
1828 This function returns a value that describes what @var{color} should
1829 ideally look like on @var{frame}. If @var{color} is defined, the
1830 value is a list of three integers, which give the amount of red, the
1831 amount of green, and the amount of blue. Each integer ranges in
1832 principle from 0 to 65535, but some displays may not use the full
1833 range. This three-element list is called the @dfn{rgb values} of the
1836 If @var{color} is not defined, the value is @code{nil}.
1839 (color-values "black")
1841 (color-values "white")
1842 @result{} (65280 65280 65280)
1843 (color-values "red")
1844 @result{} (65280 0 0)
1845 (color-values "pink")
1846 @result{} (65280 49152 51968)
1847 (color-values "hungry")
1851 The color values are returned for @var{frame}'s display. If
1852 @var{frame} is omitted or @code{nil}, the information is returned for
1853 the selected frame's display. If the frame cannot display colors, the
1854 value is @code{nil}.
1856 @findex x-color-values
1857 This function used to be called @code{x-color-values},
1858 and that name is still supported as an alias.
1861 @node Text Terminal Colors
1862 @section Text Terminal Colors
1863 @cindex colors on text-only terminals
1865 Text-only terminals usually support only a small number of colors,
1866 and the computer uses small integers to select colors on the terminal.
1867 This means that the computer cannot reliably tell what the selected
1868 color looks like; instead, you have to inform your application which
1869 small integers correspond to which colors. However, Emacs does know
1870 the standard set of colors and will try to use them automatically.
1872 The functions described in this section control how terminal colors
1875 Several of these functions use or return @dfn{rgb values}, described
1876 in @ref{Color Names}.
1878 These functions accept a display (either a frame or the name of a
1879 terminal) as an optional argument. We hope in the future to make Emacs
1880 support more than one text-only terminal at one time; then this argument
1881 will specify which terminal to operate on (the default being the
1882 selected frame's terminal; @pxref{Input Focus}). At present, though,
1883 the @var{frame} argument has no effect.
1885 @defun tty-color-define name number &optional rgb frame
1886 This function associates the color name @var{name} with
1887 color number @var{number} on the terminal.
1889 The optional argument @var{rgb}, if specified, is an rgb value, a list
1890 of three numbers that specify what the color actually looks like.
1891 If you do not specify @var{rgb}, then this color cannot be used by
1892 @code{tty-color-approximate} to approximate other colors, because
1893 Emacs will not know what it looks like.
1896 @defun tty-color-clear &optional frame
1897 This function clears the table of defined colors for a text-only terminal.
1900 @defun tty-color-alist &optional frame
1901 This function returns an alist recording the known colors supported by a
1904 Each element has the form @code{(@var{name} @var{number} . @var{rgb})}
1905 or @code{(@var{name} @var{number})}. Here, @var{name} is the color
1906 name, @var{number} is the number used to specify it to the terminal.
1907 If present, @var{rgb} is a list of three color values (for red, green,
1908 and blue) that says what the color actually looks like.
1911 @defun tty-color-approximate rgb &optional frame
1912 This function finds the closest color, among the known colors
1913 supported for @var{display}, to that described by the rgb value
1914 @var{rgb} (a list of color values). The return value is an element of
1915 @code{tty-color-alist}.
1918 @defun tty-color-translate color &optional frame
1919 This function finds the closest color to @var{color} among the known
1920 colors supported for @var{display} and returns its index (an integer).
1921 If the name @var{color} is not defined, the value is @code{nil}.
1925 @section X Resources
1927 @defun x-get-resource attribute class &optional component subclass
1928 The function @code{x-get-resource} retrieves a resource value from the X
1929 Window defaults database.
1931 Resources are indexed by a combination of a @dfn{key} and a @dfn{class}.
1932 This function searches using a key of the form
1933 @samp{@var{instance}.@var{attribute}} (where @var{instance} is the name
1934 under which Emacs was invoked), and using @samp{Emacs.@var{class}} as
1937 The optional arguments @var{component} and @var{subclass} add to the key
1938 and the class, respectively. You must specify both of them or neither.
1939 If you specify them, the key is
1940 @samp{@var{instance}.@var{component}.@var{attribute}}, and the class is
1941 @samp{Emacs.@var{class}.@var{subclass}}.
1944 @defvar x-resource-class
1945 This variable specifies the application name that @code{x-get-resource}
1946 should look up. The default value is @code{"Emacs"}. You can examine X
1947 resources for application names other than ``Emacs'' by binding this
1948 variable to some other string, around a call to @code{x-get-resource}.
1951 @defvar x-resource-name
1952 This variable specifies the instance name that @code{x-get-resource}
1953 should look up. The default value is the name Emacs was invoked with,
1954 or the value specified with the @samp{-name} or @samp{-rn} switches.
1957 To illustrate some of the above, suppose that you have the line:
1960 xterm.vt100.background: yellow
1964 in your X resources file (whose name is usually @file{~/.Xdefaults}
1965 or @file{~/.Xresources}). Then:
1969 (let ((x-resource-class "XTerm") (x-resource-name "xterm"))
1970 (x-get-resource "vt100.background" "VT100.Background"))
1974 (let ((x-resource-class "XTerm") (x-resource-name "xterm"))
1975 (x-get-resource "background" "VT100" "vt100" "Background"))
1980 @xref{X Resources,, X Resources, emacs, The GNU Emacs Manual}.
1982 @node Display Feature Testing
1983 @section Display Feature Testing
1984 @cindex display feature testing
1986 The functions in this section describe the basic capabilities of a
1987 particular display. Lisp programs can use them to adapt their behavior
1988 to what the display can do. For example, a program that ordinarily uses
1989 a popup menu could use the minibuffer if popup menus are not supported.
1991 The optional argument @var{display} in these functions specifies which
1992 display to ask the question about. It can be a display name, a frame
1993 (which designates the display that frame is on), or @code{nil} (which
1994 refers to the selected frame's display, @pxref{Input Focus}).
1996 @xref{Color Names}, @ref{Text Terminal Colors}, for other functions to
1997 obtain information about displays.
1999 @defun display-popup-menus-p &optional display
2000 This function returns @code{t} if popup menus are supported on
2001 @var{display}, @code{nil} if not. Support for popup menus requires that
2002 the mouse be available, since the user cannot choose menu items without
2006 @defun display-graphic-p &optional display
2007 @cindex frames, more than one on display
2008 @cindex fonts, more than one on display
2009 This function returns @code{t} if @var{display} is a graphic display
2010 capable of displaying several frames and several different fonts at
2011 once. This is true for displays that use a window system such as X, and
2012 false for text-only terminals.
2015 @defun display-mouse-p &optional display
2016 @cindex mouse, availability
2017 This function returns @code{t} if @var{display} has a mouse available,
2021 @defun display-color-p &optional display
2022 @findex x-display-color-p
2023 This function returns @code{t} if the screen is a color screen.
2024 It used to be called @code{x-display-color-p}, and that name
2025 is still supported as an alias.
2028 @defun display-grayscale-p &optional display
2029 This function returns @code{t} if the screen can display shades of gray.
2030 (All color displays can do this.)
2033 @defun display-supports-face-attributes-p attributes &optional display
2034 @anchor{Display Face Attribute Testing}
2035 This function returns non-@code{nil} if all the face attributes in
2036 @var{attributes} are supported (@pxref{Face Attributes}).
2038 The definition of `supported' is somewhat heuristic, but basically
2039 means that a face containing all the attributes in @var{attributes},
2040 when merged with the default face for display, can be represented in a
2045 different in appearance than the default face, and
2048 `close in spirit' to what the attributes specify, if not exact.
2051 Point (2) implies that a @code{:weight black} attribute will be
2052 satisfied by any display that can display bold, as will
2053 @code{:foreground "yellow"} as long as some yellowish color can be
2054 displayed, but @code{:slant italic} will @emph{not} be satisfied by
2055 the tty display code's automatic substitution of a `dim' face for
2059 @defun display-selections-p &optional display
2060 This function returns @code{t} if @var{display} supports selections.
2061 Windowed displays normally support selections, but they may also be
2062 supported in some other cases.
2065 @defun display-images-p &optional display
2066 This function returns @code{t} if @var{display} can display images.
2067 Windowed displays ought in principle to handle images, but some
2068 systems lack the support for that. On a display that does not support
2069 images, Emacs cannot display a tool bar.
2072 @defun display-screens &optional display
2073 This function returns the number of screens associated with the display.
2076 @defun display-pixel-height &optional display
2077 This function returns the height of the screen in pixels.
2078 On a character terminal, it gives the height in characters.
2081 @defun display-mm-height &optional display
2082 This function returns the height of the screen in millimeters,
2083 or @code{nil} if Emacs cannot get that information.
2086 @defun display-pixel-width &optional display
2087 This function returns the width of the screen in pixels.
2088 On a character terminal, it gives the width in characters.
2091 @defun display-mm-width &optional display
2092 This function returns the width of the screen in millimeters,
2093 or @code{nil} if Emacs cannot get that information.
2096 @defun display-backing-store &optional display
2097 This function returns the backing store capability of the display.
2098 Backing store means recording the pixels of windows (and parts of
2099 windows) that are not exposed, so that when exposed they can be
2100 displayed very quickly.
2102 Values can be the symbols @code{always}, @code{when-mapped}, or
2103 @code{not-useful}. The function can also return @code{nil}
2104 when the question is inapplicable to a certain kind of display.
2107 @defun display-save-under &optional display
2108 This function returns non-@code{nil} if the display supports the
2109 SaveUnder feature. That feature is used by pop-up windows
2110 to save the pixels they obscure, so that they can pop down
2114 @defun display-planes &optional display
2115 This function returns the number of planes the display supports.
2116 This is typically the number of bits per pixel.
2117 For a tty display, it is log to base two of the number of colors supported.
2120 @defun display-visual-class &optional display
2121 This function returns the visual class for the screen. The value is one
2122 of the symbols @code{static-gray}, @code{gray-scale},
2123 @code{static-color}, @code{pseudo-color}, @code{true-color}, and
2124 @code{direct-color}.
2127 @defun display-color-cells &optional display
2128 This function returns the number of color cells the screen supports.
2131 These functions obtain additional information specifically
2134 @defun x-server-version &optional display
2135 This function returns the list of version numbers of the X server
2136 running the display. The value is a list of three integers: the major
2137 and minor version numbers of the X protocol, and the
2138 distributor-specific release number of the X server software itself.
2141 @defun x-server-vendor &optional display
2142 This function returns the ``vendor'' that provided the X server
2143 software (as a string). Really this means whoever distributes the X
2146 When the developers of X labelled software distributors as
2147 ``vendors'', they showed their false assumption that no system could
2148 ever be developed and distributed noncommercially.
2152 @defvar x-no-window-manager
2153 This variable's value is @code{t} if no X window manager is in use.
2159 The functions @code{x-pixel-width} and @code{x-pixel-height} return the
2160 width and height of an X Window frame, measured in pixels.
2164 arch-tag: 94977df6-3dca-4730-b57b-c6329e9282ba