2 @c This is part of the GNU Emacs Lisp Reference Manual.
3 @c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2001,
4 @c 2002, 2003, 2004, 2005, 2006, 2007, 2008 Free Software Foundation, Inc.
5 @c See the file elisp.texi for copying conditions.
6 @setfilename ../../info/windows
7 @node Windows, Frames, Buffers, Top
10 This chapter describes most of the functions and variables related to
11 Emacs windows. @xref{Frames and Windows}, for how windows relate to
12 frames. @xref{Display}, for information on how text is displayed in
16 * Basic Windows:: Basic information on using windows.
17 * Splitting Windows:: Splitting one window into two windows.
18 * Deleting Windows:: Deleting a window gives its space to other windows.
19 * Selecting Windows:: The selected window is the one that you edit in.
20 * Cyclic Window Ordering:: Moving around the existing windows.
21 * Buffers and Windows:: Each window displays the contents of a buffer.
22 * Displaying Buffers:: Higher-level functions for displaying a buffer
23 and choosing a window for it.
24 * Choosing Window:: How to choose a window for displaying a buffer.
25 * Dedicated Windows:: How to avoid displaying another buffer in
27 * Window Point:: Each window has its own location of point.
28 * Window Start and End:: Buffer positions indicating which text is
29 on-screen in a window.
30 * Textual Scrolling:: Moving text up and down through the window.
31 * Vertical Scrolling:: Moving the contents up and down on the window.
32 * Horizontal Scrolling:: Moving the contents sideways on the window.
33 * Size of Window:: Accessing the size of a window.
34 * Resizing Windows:: Changing the size of a window.
35 * Coordinates and Windows:: Converting coordinates to windows.
36 * Window Tree:: The layout and sizes of all windows in a frame.
37 * Window Configurations:: Saving and restoring the state of the screen.
38 * Window Parameters:: Associating additional information with windows.
39 * Window Hooks:: Hooks for scrolling, window size changes,
40 redisplay going past a certain point,
41 or window configuration changes.
45 @section Basic Concepts of Emacs Windows
47 @cindex selected window
49 A @dfn{window} in Emacs is the physical area of the screen in which a
50 buffer is displayed. The term is also used to refer to a Lisp object that
51 represents that screen area in Emacs Lisp. It should be
52 clear from the context which is meant.
54 Emacs groups windows into frames; see @ref{Frames}. A frame
55 represents an area of screen available for Emacs to use. Each frame
56 always contains at least one window, but you can subdivide it
57 vertically or horizontally into multiple, nonoverlapping Emacs
60 In each frame, at any time, one and only one window is designated as
61 @dfn{selected within the frame}. The frame's cursor appears in that
62 window, but the other windows have ``non-selected'' cursors, normally
63 less visible. (@xref{Cursor Parameters}, for customizing this.) At
64 any time, one frame is the selected frame; and the window selected
65 within that frame is @dfn{the selected window}. The selected window's
66 buffer is usually the current buffer (except when @code{set-buffer} has
67 been used); see @ref{Current Buffer}.
69 For practical purposes, a window exists only while it is displayed in
70 a frame. Once removed from the frame, the window is effectively deleted
71 and should not be used, @emph{even though there may still be references
72 to it} from other Lisp objects; see @ref{Deleting Windows}. Restoring a
73 saved window configuration is the only way for a window no longer on the
74 screen to come back to life; see @ref{Window Configurations}.
76 @cindex multiple windows
77 Users create multiple windows so they can look at several buffers at
78 once. Lisp libraries use multiple windows for a variety of reasons, but
79 most often to display related information. In Rmail, for example, you
80 can move through a summary buffer in one window while the other window
81 shows messages one at a time as they are reached.
83 The meaning of ``window'' in Emacs is similar to what it means in the
84 context of general-purpose window systems such as X, but not identical.
85 The X Window System places X windows on the screen; Emacs uses one or
86 more X windows as frames, and subdivides them into
87 Emacs windows. When you use Emacs on a character-only terminal, Emacs
88 treats the whole terminal screen as one frame.
90 @cindex terminal screen
91 @cindex screen of terminal
93 Most window systems support arbitrarily located overlapping windows.
94 In contrast, Emacs windows are @dfn{tiled}; they never overlap, and
95 together they fill the whole screen or frame. Because of the way in
96 which Emacs creates new windows (@pxref{Splitting Windows}) and resizes
97 them (@pxref{Resizing Windows}), not all conceivable tilings of windows
98 on an Emacs frame are actually possible.
100 @defun windowp object
101 This function returns @code{t} if @var{object} is a window.
104 @node Splitting Windows
105 @section Splitting Windows
106 @cindex splitting windows
107 @cindex window splitting
109 The functions described below are the primitives used to split a window
110 into two windows. They do not accept a buffer as an argument. Rather,
111 the two ``halves'' of the split window initially display the same buffer
112 previously visible in the window that was split.
114 @deffn Command split-window &optional window size horizontal
115 This function splits a new window out of @var{window}'s screen area. It
116 returns the new window. The default for @var{window} is the selected
117 window. When you split the selected window, it remains selected.
119 If @var{horizontal} is non-@code{nil}, then @var{window} splits into two
120 side by side windows. The original window keeps the leftmost @var{size}
121 columns, and gives the rest of the columns to the new window.
122 Otherwise, @var{window} splits into windows one above the other, the
123 original window keeps the upper @var{size} lines and gives the rest of
124 the lines to the new window. The original window @var{window} is
125 therefore the left-hand or upper of the two, and the new window is the
128 If @var{size} is omitted or @code{nil}, then @var{window} is divided
129 evenly into two parts. (If there is an odd line, it is allocated to
130 the new window.) When @code{split-window} is called interactively,
131 all its arguments are @code{nil}.
133 If splitting would result in making a window that is smaller than
134 @code{window-min-height} or @code{window-min-width} (@pxref{Resizing
135 Windows}), @code{split-window} signals an error and does not split the
138 The following example starts with one window on a screen that is 50
139 lines high by 80 columns wide; then it splits the window.
143 (setq w (selected-window))
144 @result{} #<window 8 on windows.texi>
145 (window-edges) ; @r{Edges in order:}
146 @result{} (0 0 80 50) ; @r{left--top--right--bottom}
150 ;; @r{Returns window created}
151 (setq w2 (split-window w 15))
152 @result{} #<window 28 on windows.texi>
156 @result{} (0 15 80 50) ; @r{Bottom window;}
161 @result{} (0 0 80 15) ; @r{Top window}
165 The screen looks like this:
181 Next, split the top window horizontally:
185 (setq w3 (split-window w 35 t))
186 @result{} #<window 32 on windows.texi>
190 @result{} (35 0 80 15) ; @r{Left edge at column 35}
194 @result{} (0 0 35 15) ; @r{Right edge at column 35}
198 @result{} (0 15 80 50) ; @r{Bottom window unchanged}
203 Now the screen looks like this:
220 Normally, Emacs indicates the border between two side-by-side windows
221 with a scroll bar (@pxref{Scroll Bars}), or with @samp{|} characters. The
222 display table can specify alternative border characters; see @ref{Display
226 @deffn Command split-window-vertically &optional size
227 This function splits the selected window into two windows, one above the
228 other, leaving the upper of the two windows selected, with @var{size}
229 lines. (If @var{size} is negative, then the lower of the two windows
230 gets @minus{}@var{size} lines and the upper window gets the rest, but
231 the upper window is still the one selected.) However, if
232 @code{split-window-keep-point} (see below) is @code{nil}, then either
233 window can be selected.
235 In other respects, this function is similar to @code{split-window}.
236 In particular, the upper window is the original one and the return
237 value is the new, lower window.
240 @defopt split-window-keep-point
241 If this variable is non-@code{nil} (the default), then
242 @code{split-window-vertically} behaves as described above.
244 If it is @code{nil}, then @code{split-window-vertically} adjusts point
245 in each of the two windows to avoid scrolling. (This is useful on
246 slow terminals.) It selects whichever window contains the screen line
247 that point was previously on.
249 This variable affects the behavior of @code{split-window-vertically}
250 only. It has no effect on the other functions described here.
253 @deffn Command split-window-horizontally &optional size
254 This function splits the selected window into two windows
255 side-by-side, leaving the selected window on the left with @var{size}
256 columns. If @var{size} is negative, the rightmost window gets
257 @minus{}@var{size} columns, but the leftmost window still remains
260 This function is basically an interface to @code{split-window}.
261 You could define a simplified version of the function like this:
265 (defun split-window-horizontally (&optional arg)
266 "Split selected window into two windows, side by side..."
270 (let ((size (and arg (prefix-numeric-value arg))))
272 (setq size (+ (window-width) size)))
273 (split-window nil size t)))
278 @defun one-window-p &optional no-mini all-frames
279 This function returns non-@code{nil} if there is only one window. The
280 argument @var{no-mini}, if non-@code{nil}, means don't count the
281 minibuffer even if it is active; otherwise, the minibuffer window is
282 counted when it is active.
284 The argument @var{all-frames} specifies which frames to consider. Here
285 are the possible values and their meanings:
289 Count the windows in the selected frame, plus the minibuffer used
290 by that frame even if it lies in some other frame.
293 Count all windows in all existing frames.
296 Count all windows in all visible frames.
299 Count all windows in all visible or iconified frames.
302 Count precisely the windows in the selected frame, and no others.
306 @node Deleting Windows
307 @section Deleting Windows
308 @cindex deleting windows
310 A window remains visible on its frame unless you @dfn{delete} it by
311 calling certain functions that delete windows. A deleted window cannot
312 appear on the screen, but continues to exist as a Lisp object until
313 there are no references to it. There is no way to cancel the deletion
314 of a window aside from restoring a saved window configuration
315 (@pxref{Window Configurations}). Restoring a window configuration also
316 deletes any windows that aren't part of that configuration.
318 When you delete a window, the space it took up is given to one of
319 its sibling windows adjacent to it.
322 @defun window-live-p window
323 This function returns @code{nil} if @var{window} is deleted, and
326 @strong{Warning:} Erroneous information or fatal errors may result from
327 using a deleted window as if it were live.
330 @deffn Command delete-window &optional window
331 This function removes @var{window} from display and returns @code{nil}.
332 The default for @var{window} is the selected window. An error is
333 signaled if @var{window} is the only window on its frame.
336 @deffn Command delete-other-windows &optional window
337 This function makes @var{window} the only window on its frame, by
338 deleting the other windows in that frame. The default for @var{window}
339 is the selected window. The return value is @code{nil}.
342 @deffn Command delete-windows-on &optional buffer-or-name frame
343 This function deletes all windows showing @var{buffer-or-name}. If
344 there are no windows showing @var{buffer-or-name}, it does nothing. The
345 optional argument @var{buffer-or-name} may be a buffer or the name of an
346 existing buffer and defaults to the current buffer.
348 @code{delete-windows-on} operates frame by frame. If a frame has
349 several windows showing different buffers, then those showing
350 @var{buffer-or-name} are removed, and the others expand to fill the
351 space. If all windows in some frame are showing @var{buffer-or-name}
352 (including the case where there is only one window), then the frame
353 winds up with a single window showing another buffer chosen with
354 @code{other-buffer} (@pxref{The Buffer List}). If, however, the window
355 showing @var{buffer-or-name} is dedicated to its buffer
356 (@pxref{Dedicated Windows}), and there are other frames left, that
357 window's frame is deleted.
359 The optional argument @var{frame} specifies which frames to operate on.
360 This function does not use it in quite the same way as the other
361 functions which scan all windows; specifically, the values @code{t} and
362 @code{nil} have the opposite of their meanings in other functions. Here
363 are the full details:
367 If it is @code{nil}, operate on all frames.
369 If it is @code{t}, operate on the selected frame.
371 If it is @code{visible}, operate on all visible frames.
373 If it is 0, operate on all visible or iconified frames.
375 If it is a frame, operate on that frame.
378 This function always returns @code{nil}.
381 @node Selecting Windows
382 @section Selecting Windows
383 @cindex selecting a window
385 When a window is selected, the buffer in the window becomes the current
386 buffer, and the cursor will appear in it.
388 @defun selected-window
389 This function returns the selected window. This is the window in
390 which the cursor appears and to which many commands apply.
393 @defun select-window window &optional norecord
394 This function makes @var{window} the selected window. The cursor then
395 appears in @var{window} (after redisplay). Unless @var{window} was
396 already selected, @code{select-window} makes @var{window}'s buffer the
397 current buffer. The return value is @var{window}.
399 Normally, @var{window}'s selected buffer is moved to the front of the
400 buffer list (@pxref{The Buffer List}) and @var{window} becomes the most
401 recently selected window. But if @var{norecord} is non-@code{nil}, the
402 buffer list remains unchanged and @var{window} does not become the most
403 recently selected one.
408 (setq w (next-window))
410 @result{} #<window 65 on windows.texi>
415 @defmac save-selected-window forms@dots{}
416 This macro records the selected frame, as well as the selected window
417 of each frame, executes @var{forms} in sequence, then restores the
418 earlier selected frame and windows. It also saves and restores the
419 current buffer. It returns the value of the last form in @var{forms}.
421 This macro does not save or restore anything about the sizes,
422 arrangement or contents of windows; therefore, if @var{forms} change
423 them, the change persists. If the previously selected window of some
424 frame is no longer live at the time of exit from @var{forms}, that
425 frame's selected window is left alone. If the previously selected
426 window is no longer live, then whatever window is selected at the end of
427 @var{forms} remains selected. The current buffer is restored if and
428 only if it is still live when exiting @var{forms}.
430 This macro changes neither the ordering of recently selected windows nor
434 @defmac with-selected-window window forms@dots{}
435 This macro selects @var{window}, executes @var{forms} in sequence, then
436 restores the previously selected window and current buffer. The ordering
437 of recently selected windows and the buffer list remain unchanged unless
438 you deliberately change them within @var{forms}, for example, by calling
439 @code{select-window} with argument @var{norecord} @code{nil} or omitted
443 @cindex finding windows
444 The following functions choose one of the windows on the screen,
445 offering various criteria for the choice.
447 @defun get-lru-window &optional frame dedicated
448 This function returns the window least recently ``used'' (that is,
449 selected). If any full-width windows are present, it only considers
452 The selected window can be the least recently used window if it is the
453 only window. A newly created window becomes the least recently used
454 window until it is selected. A minibuffer window is never a candidate.
455 A dedicated window (@pxref{Dedicated Windows}) is never a candidate
456 unless the optional argument @var{dedicated} is non-@code{nil}.
458 The optional argument @var{frame} specifies which windows are
463 If it is @code{nil}, consider windows on the selected frame.
465 If it is @code{t}, consider windows on all frames.
467 If it is @code{visible}, consider windows on all visible frames.
469 If it is 0, consider windows on all visible or iconified frames.
471 If it is a frame, consider windows on that frame.
475 @defun get-largest-window &optional frame dedicated
476 This function returns the window with the largest area (height times
477 width). If there are no side-by-side windows, then this is the window
478 with the most lines. A minibuffer window is never a candidate. A
479 dedicated window (@pxref{Dedicated Windows}) is never a candidate unless
480 the optional argument @var{dedicated} is non-@code{nil}.
482 If there are two candidate windows of the same size, this function
483 prefers the one that comes first in the cyclic ordering of windows,
484 starting from the selected window (@pxref{Cyclic Window Ordering}).
486 The optional argument @var{frame} specifies which set of windows to
487 consider, see @code{get-lru-window} above.
490 @cindex window that satisfies a predicate
491 @cindex conditional selection of windows
492 @defun get-window-with-predicate predicate &optional minibuf all-frames default
493 This function returns a window satisfying @var{predicate}. It cycles
494 through all visible windows using @code{walk-windows} (@pxref{Cyclic
495 Window Ordering}), calling @var{predicate} on each one of them with that
496 window as its argument. The function returns the first window for which
497 @var{predicate} returns a non-@code{nil} value; if that never happens,
498 it returns @var{default} (which defaults to @code{nil}).
500 The optional arguments @var{minibuf} and @var{all-frames} specify the
501 set of windows to include in the scan. See the description of
502 @code{next-window} in @ref{Cyclic Window Ordering}, for details.
505 @node Cyclic Window Ordering
506 @comment node-name, next, previous, up
507 @section Cyclic Ordering of Windows
508 @cindex cyclic ordering of windows
509 @cindex ordering of windows, cyclic
510 @cindex window ordering, cyclic
512 When you use the command @kbd{C-x o} (@code{other-window}) to select
513 some other window, it moves through the windows on the screen in a
514 specific order. For any given configuration of windows, this order
515 never varies. It is called the @dfn{cyclic ordering of windows}.
517 This ordering generally goes from top to bottom, and from left to
518 right. But it may go down first or go right first, depending on the
519 order in which windows were split.
521 If the first split was vertical (into windows one above each other),
522 and then the subwindows were split horizontally, then the ordering is
523 left to right in the top of the frame, and then left to right in the
524 next lower part of the frame, and so on. If the first split was
525 horizontal, the ordering is top to bottom in the left part, and so on.
526 In general, within each set of siblings at any level in the window tree
527 (@pxref{Window Tree}), the order is left to right, or top to bottom.
529 @deffn Command next-window &optional window minibuf all-frames
530 @cindex minibuffer window, and @code{next-window}
531 This function returns the window following @var{window} in the cyclic
532 ordering of windows. This is the window @kbd{C-x o} selects if typed
533 when @var{window} is selected. The default for @var{window} is the
536 The value of the optional argument @var{minibuf} specifies whether the
537 minibuffer is included in the window order. Normally, when
538 @var{minibuf} is @code{nil}, the minibuffer is included only if it is
539 currently ``active''; this matches the behavior of @kbd{C-x o}. (The
540 minibuffer window is active while the minibuffer is in use; see
543 If @var{minibuf} is @code{t}, the cyclic ordering includes the
544 minibuffer window even if it is not active. If @var{minibuf} is neither
545 @code{t} nor @code{nil}, the minibuffer window is not included even if
548 The optional argument @var{all-frames} specifies which frames to
549 consider. Here are the possible values and their meanings:
553 Consider all the windows in @var{window}'s frame, plus the minibuffer
554 used by that frame even if it lies in some other frame. If the
555 minibuffer counts (as determined by @var{minibuf}), then all windows on
556 all frames that share that minibuffer count too.
559 Consider all windows in all existing frames.
562 Consider all windows in all visible frames. (To get useful results, you
563 must ensure @var{window} is in a visible frame.)
566 Consider all windows in all visible or iconified frames.
569 Consider all windows on that frame.
572 Consider precisely the windows in @var{window}'s frame, and no others.
575 This example assumes there are two windows, both displaying the
576 buffer @samp{windows.texi}:
581 @result{} #<window 56 on windows.texi>
584 (next-window (selected-window))
585 @result{} #<window 52 on windows.texi>
588 (next-window (next-window (selected-window)))
589 @result{} #<window 56 on windows.texi>
594 @deffn Command previous-window &optional window minibuf all-frames
595 This function returns the window preceding @var{window} in the cyclic
596 ordering of windows. The other arguments specify which windows to
597 include in the cycle, as in @code{next-window}.
600 @deffn Command other-window count &optional all-frames
601 This function selects another window in the cyclic ordering of windows.
602 @var{count} specifies the number of windows to skip in the ordering,
603 starting with the selected window, before making the selection. If
604 @var{count} is a positive number, it skips @var{count} windows forwards.
605 @var{count} negative means skip @minus{}@var{count} windows backwards.
606 If @var{count} is zero, it does not skip any window, thus re-selecting
607 the selected window. In an interactive call, @var{count} is the numeric
610 The optional argument @var{all-frames} has the same meaning as in
611 @code{next-window}, but the @var{minibuf} argument of @code{next-window}
612 is always effectively @code{nil}. This function returns @code{nil}.
616 @defun walk-windows proc &optional minibuf all-frames
617 This function cycles through all windows. It calls the function
618 @code{proc} once for each window, with the window as its sole
621 The optional arguments @var{minibuf} and @var{all-frames} specify the
622 set of windows to include in the walk. See @code{next-window}, above,
626 @defun window-list &optional frame minibuf window
627 This function returns a list of all windows on @var{frame}, starting
628 with @var{window}. The default for @var{frame} is the selected frame;
629 the default for @var{window} is the selected window.
631 The value of @var{minibuf} specifies if the minibuffer window shall be
632 included in the result list. If @var{minibuf} is @code{t}, the result
633 always includes the minibuffer window. If @var{minibuf} is @code{nil}
634 or omitted, that includes the minibuffer window if it is active. If
635 @var{minibuf} is neither @code{nil} nor @code{t}, the result never
636 includes the minibuffer window.
639 @node Buffers and Windows
640 @section Buffers and Windows
641 @cindex examining windows
642 @cindex windows, controlling precisely
643 @cindex buffers, controlled in windows
645 This section describes low-level functions to examine windows or to
646 display buffers in windows in a precisely controlled fashion.
648 See the following section for
651 @xref{Displaying Buffers}, for
653 related functions that find a window to use and specify a buffer for it.
654 The functions described there are easier to use, but they employ
655 heuristics in choosing or creating a window; use the functions described
656 here when you need complete control.
658 @defun set-window-buffer window buffer-or-name &optional keep-margins
659 This function makes @var{window} display @var{buffer-or-name} as its
660 contents. It returns @code{nil}. The default for @var{window} is the
661 selected window. The argument @var{buffer-or-name} must specify a
662 buffer or the name of an existing buffer.
664 @code{set-window-buffer} is the fundamental primitive for changing which
665 buffer is displayed in a window, and all ways of doing that call this
670 (set-window-buffer (selected-window) "foo")
675 Normally, displaying @var{buffer-or-name} in @var{window} resets the
676 window's position, display margins, fringe widths, and scroll bar
677 settings based on the local variables of that buffer.
678 However, if @var{keep-margins} is non-@code{nil}, display margins and
679 fringe widths of @var{window} remain unchanged. @xref{Fringes}.
681 @code{set-window-buffer} signals an error when @var{window} is
682 @dfn{strongly} dedicated to its buffer (@pxref{Dedicated Windows}) and
683 does not already display @var{buffer-or-name}.
685 Note that this function runs @code{window-scroll-functions} before
686 running @code{window-configuration-change-hook}.
689 @defvar buffer-display-count
690 This buffer-local variable records the number of times a buffer has been
691 displayed in a window. It is incremented each time
692 @code{set-window-buffer} is called for the buffer.
695 @defun window-buffer &optional window
696 This function returns the buffer that @var{window} is displaying. The
697 default for @var{window} is the selected window.
702 @result{} #<buffer windows.texi>
707 @defun get-buffer-window &optional buffer-or-name all-frames
708 This function returns a window currently displaying
709 @var{buffer-or-name}, or @code{nil} if there is none. If there are
710 several such windows, then the function returns the first one in the
711 cyclic ordering of windows, starting from the selected window.
712 @xref{Cyclic Window Ordering}.
714 The argument @var{BUFFER-OR-NAME} may be a buffer or a buffer name and
715 defaults to the current buffer. The optional argument @var{all-frames}
716 specifies which windows to consider:
720 @code{nil} means consider windows on the selected frame.
722 @code{t} means consider windows on all existing frames.
724 @code{visible} means consider windows on all visible frames.
726 0 means consider windows on all visible or iconified frames.
728 A frame means consider windows on that frame only.
731 Observe that the behavior of @code{get-buffer-window} may differ from
732 that of @code{next-window} (@pxref{Cyclic Window Ordering}) when
733 @var{all-frames} equals @code{nil} or any value not listed here.
734 Perhaps we will change @code{get-buffer-window} in the future to make it
735 compatible with the other functions.
738 @defun get-buffer-window-list &optional buffer-or-name minibuf all-frames
739 This function returns a list of all windows currently displaying
740 @var{buffer-or-name}. The argument @var{buffer-or-name} may be a buffer
741 or the name of an existing buffer and defaults to the current buffer.
743 The two remaining arguments work like the same-named arguments of
744 @code{next-window}; they are @emph{not} like the optional arguments of
745 @code{get-buffer-window}.
748 @defvar buffer-display-time
749 This variable records the time at which a buffer was last made visible
750 in a window. It is always local in each buffer; each time
751 @code{set-window-buffer} is called, it sets this variable to
752 @code{(current-time)} in the specified buffer (@pxref{Time of Day}).
753 When a buffer is first created, @code{buffer-display-time} starts out
754 with the value @code{nil}.
757 @node Displaying Buffers
758 @section Displaying Buffers in Windows
759 @cindex switching to a buffer
760 @cindex displaying a buffer
762 In this section we describe convenient functions that choose a window
763 automatically and use it to display a specified buffer. These functions
764 can also split an existing window in certain circumstances. We also
765 describe variables that parameterize the heuristics used for choosing a
768 See the preceding section for
771 @xref{Buffers and Windows}, for
773 low-level primitives that give you more precise control. All of these
774 functions work by calling @code{set-window-buffer}.
776 Do not use the functions in this section in order to make a buffer
777 current so that a Lisp program can access or modify it; they are too
778 drastic for that purpose, since they change the display of buffers in
779 windows, which would be gratuitous and surprise the user. Instead, use
780 @code{set-buffer} and @code{save-current-buffer} (@pxref{Current
781 Buffer}), which designate buffers as current for programmed access
782 without affecting the display of buffers in windows.
784 @deffn Command switch-to-buffer buffer-or-name &optional norecord
785 This function makes @var{buffer-or-name} the current buffer, and also
786 displays the buffer in the selected window. This means that a human can
787 see the buffer and subsequent keyboard commands will apply to it.
788 Contrast this with @code{set-buffer}, which makes @var{buffer-or-name}
789 the current buffer but does not display it in the selected window;
790 see @ref{Current Buffer}.
792 If @var{buffer-or-name} is @code{nil}, @code{switch-to-buffer} chooses a
793 buffer using @code{other-buffer}. If @var{buffer-or-name} is a string
794 that does not identify an existing buffer, then a new buffer by that
795 name is created. The major mode for the new buffer is set according to
796 the variable @code{default-major-mode}; see @ref{Auto Major Mode}.
798 When @code{enable-recursive-minibuffers} is non-@code{nil} and the
799 selected window is either the minibuffer window or is dedicated to its
800 buffer (@pxref{Dedicated Windows}), @code{switch-to-buffer} calls
801 @code{pop-to-buffer} (see below) to display the buffer in some other
804 Normally the specified buffer is put at the front of the buffer list
805 (both the selected frame's buffer list and the frame-independent buffer
806 list). This affects the operation of @code{other-buffer}. However, if
807 @var{norecord} is non-@code{nil}, this is not done. @xref{The Buffer
810 The @code{switch-to-buffer} function is often used interactively, as
811 the binding of @kbd{C-x b}. It is also used frequently in programs. It
812 returns the buffer that it switched to.
815 The next two functions are similar to @code{switch-to-buffer}, except
816 for the described features.
818 @deffn Command switch-to-buffer-other-window buffer-or-name &optional norecord
819 This function makes @var{buffer-or-name} the current buffer, displays it
820 in a window not currently selected, and selects that window. The
821 handling of the buffer is the same as in @code{switch-to-buffer}.
823 The currently selected window is absolutely never used to do the job.
824 If it is the only window, then it is split to make a distinct window for
825 this purpose. If the selected window is already displaying the buffer,
826 then it continues to do so, but another window is nonetheless found to
827 display it in as well.
829 This function updates the buffer list just like @code{switch-to-buffer}
830 unless @var{norecord} is non-@code{nil}.
833 @deffn Command pop-to-buffer buffer-or-name &optional other-window norecord
834 This command makes @var{buffer-or-name} the current buffer and switches
835 to it in some window, preferably not the window previously selected.
836 The ``popped-to'' window becomes the selected window. Its frame is
837 given the X server's focus, if possible; see @ref{Input Focus}. The return
838 value is the buffer that was switched to.
840 If @var{buffer-or-name} is @code{nil}, that means to choose some other
841 buffer, but you don't specify which. If @var{buffer-or-name} is a
842 string that does not name an existing buffer, a buffer by that name is
843 created. The major mode for the new buffer is set according to the
844 variable @code{default-major-mode}. @xref{Auto Major Mode}.
846 If the variable @code{pop-up-frames} is non-@code{nil},
847 @code{pop-to-buffer} looks for a window in any visible frame already
848 displaying the buffer; if there is one, it selects and returns that
849 window. If no such window exists, it creates a new frame and displays
852 If @code{pop-up-frames} is @code{nil}, then @code{pop-to-buffer}
853 operates entirely within the selected frame. (If the selected frame has
854 just a minibuffer, @code{pop-to-buffer} operates within the most
855 recently selected frame that was not just a minibuffer.)
857 If the variable @code{pop-up-windows} is non-@code{nil}, windows may be
858 split to create a new window that is different from the original window.
859 For details, see @ref{Choosing Window}.
861 If @var{other-window} is non-@code{nil}, @code{pop-to-buffer} finds or
862 creates another window even if @var{buffer-or-name} is already visible
863 in the selected window. Thus @var{buffer-or-name} could end up
864 displayed in two windows. On the other hand, if @var{buffer-or-name} is
865 already displayed in the selected window and @var{other-window} is
866 @code{nil}, then the selected window is considered sufficient for
867 displaying @var{buffer-or-name}, so that nothing needs to be done.
869 All the variables that affect @code{display-buffer} affect
870 @code{pop-to-buffer} as well. @xref{Choosing Window}.
872 This function updates the buffer list just like @code{switch-to-buffer}
873 unless @var{norecord} is non-@code{nil}.
876 @deffn Command replace-buffer-in-windows &optional buffer-or-name
877 This function replaces @var{buffer-or-name} in all windows displaying
878 it with some other buffer. It uses @code{other-buffer} to choose the
879 other buffer. In the usual applications of this function, you
880 don't care which other buffer is used; you just want to make sure that
881 @var{buffer-or-name} is no longer displayed.
883 The argument @var{buffer-or-name} may be a buffer or the name of an
884 existing buffer and defaults to the current buffer.
886 If a window displaying @var{buffer-or-name} is dedicated
887 (@pxref{Dedicated Windows}), and is not the only window on its frame,
888 that window is deleted. If that window is the only window on its frame
889 and there are other frames left, the window's frame is deleted too. If
890 there are no other frames left, some other buffer is displayed in that
893 This function returns @code{nil}.
896 @node Choosing Window
897 @section Choosing a Window for Display
899 This section describes the basic facility that chooses a window to
900 display a buffer in---@code{display-buffer}. Higher-level functions and
901 commands, like @code{switch-to-buffer} and @code{pop-to-buffer}, use this
902 subroutine. Here we describe how to use @code{display-buffer} and how
905 @deffn Command display-buffer buffer-or-name &optional not-this-window frame
906 This command makes @var{buffer-or-name} appear in some window, but it
907 does not select that window and does not make the buffer specified by
908 @var{buffer-or-name} current. The identity of the selected window is
909 unaltered by this function. The argument @var{buffer-or-name} must be a
910 buffer or the name of an existing buffer.
912 @var{not-this-window} non-@code{nil} means to display the specified
913 buffer in a window other than the selected one, even if it is already
914 displayed in the selected window. This can cause the buffer to appear
915 in two windows at once. Otherwise, if @var{buffer-or-name} is already
916 being displayed in any window, that is good enough, so this function
919 @code{display-buffer} returns the window chosen to display
920 @var{buffer-or-name}.
922 If the optional argument @var{frame} is non-@code{nil}, it specifies
923 which frames to check when deciding whether the buffer is already
924 displayed. If the buffer is already displayed in some window on one of
925 these frames, @code{display-buffer} simply returns that window. Here
926 are the possible values of @var{frame}:
930 @code{nil} means consider windows on the selected frame.
931 (Actually, the last non-minibuffer frame.)
933 @code{t} means consider windows on all frames.
935 @code{visible} means consider windows on all visible frames.
937 0 means consider windows on all visible or iconified frames.
939 A frame means consider windows on that frame only.
942 Precisely how @code{display-buffer} finds or creates a window depends on
943 the variables described below.
946 @defopt display-buffer-reuse-frames
947 If this variable is non-@code{nil}, @code{display-buffer} searches
948 existing frames for a window displaying @var{buffer-or-name}. If the
949 buffer is already displayed in a window in some frame,
950 @code{display-buffer} makes the frame visible and raises it, to use that
951 window. If the buffer is not already displayed, or
952 @code{display-buffer-reuse-frames} is @code{nil}, the behavior of
953 @code{display-buffer} is determined by the variables described next.
956 @defopt pop-up-windows
957 This variable specifies whether @code{display-buffer} is allowed to
958 split (@pxref{Splitting Windows}) an existing window . If it is
959 non-@code{nil}, @code{display-buffer} tries to the split the largest or
960 least recently used window on the selected frame. (If the selected
961 frame is a minibuffer-only frame, it tries to split a window on another
962 frame instead.) If @code{pop-up-windows} is nil or the variable
963 @code{pop-up-frames} (see below) is non-@code{nil},
964 @code{display-buffer} does not split any window.
967 @defvar split-window-preferred-function
968 This variable specifies how to split a window. Its value, if
969 non-@code{nil}, should be a function of one argument, which is a
970 window. If this variable specifies a function, @code{display-buffer}
971 will call it with one or more candidate windows when it looks for a
972 window to split. If the argument window fits, the function is
973 expected to split it and return a new window. If the function returns
974 @code{nil}, the argument window will not be split.
976 If the value of this variable is @code{nil}, @code{display-buffer}
977 uses the two variables described next to decide whether and which
981 @defopt split-height-threshold
982 This variable specifies whether @code{display-buffer} may split a window
983 vertically, provided there are multiple windows. If the value is a
984 number, @code{display-buffer} splits a window only if it has at least
985 this many lines. If no window is tall enough, or if the value of this
986 variable is @code{nil}, @code{display-buffer} tries to split some window
987 horizontally, subject to restrictions of @code{split-width-threshold}
988 (see below). If splitting horizontally is impossible too,
989 @code{display-buffer} splits a window vertically only if it's the only
990 window on its frame and not the minibuffer window, and only if
991 @code{pop-up-windows} is non-@code{nil}.
993 A window whose height is fixed (@pxref{Resizing Windows}) cannot be
994 split vertically by @code{display-buffer}. Also, @code{display-buffer}
995 splits a window vertically only if it can accommodate two windows that
996 are both at least `window-min-height' lines tall. Moreover, if the
997 window that shall be split has a mode line, the window must be at least
998 four lines tall in order to make sure that the new window can have a
999 mode line as well. If the original window doesn't have a mode line, a
1000 height of two lines suffices.
1003 @defopt split-width-threshold
1004 This variable specifies whether @code{display-buffer} may split a window
1005 horizontally. If the value is a number, @code{display-buffer} may split
1006 a window if it has at least this many columns. If the value of this
1007 variable is @code{nil}, @code{display-buffer} will not split any windows
1008 horizontally. (It still might split some window vertically, though, see
1011 A window whose width is fixed (@pxref{Resizing Windows}) cannot be split
1012 horizontally by @code{display-buffer}. Also, @code{display-buffer}
1013 splits a window horizontally only if it can accommodate two windows that
1014 are both at least `window-min-width' columns wide.
1017 @defopt even-window-heights
1018 This variable specifies whether @code{display-buffer} should even out
1019 window heights if the buffer gets displayed in an existing window, above
1020 or beneath another window. If @code{even-window-heights} is
1021 non-@code{nil}, the default, window heights will be evened out. If
1022 either of the involved window has fixed height (@pxref{Resizing
1023 Windows}) or @code{even-window-heights} is @code{nil}, the original
1024 window heights will be left alone.
1028 @defopt pop-up-frames
1029 This variable specifies whether @code{display-buffer} makes new frames.
1030 If it is non-@code{nil}, @code{display-buffer} looks for an existing
1031 window already displaying the desired buffer, on any visible frame. If
1032 it finds one, it returns that window. Otherwise it makes a new frame,
1033 unless the variable's value is @code{graphic-only} and the selected
1034 frame is not on a graphic display. @xref{Frames}, for more information.
1036 Note that the value of @code{pop-up-windows} does not matter if
1037 @code{pop-up-frames} is non-@code{nil}. If @code{pop-up-frames} is
1038 @code{nil}, then @code{display-buffer} either splits a window or reuses
1043 @defopt pop-up-frame-function
1044 This variable specifies how to make a new frame if @code{pop-up-frames}
1047 Its value should be a function of no arguments. When
1048 @code{display-buffer} makes a new frame, it does so by calling that
1049 function, which should return a frame. The default value of the
1050 variable is a function that creates a frame using parameters from
1051 @code{pop-up-frame-alist}.
1054 @defopt pop-up-frame-alist
1055 This variable holds an alist specifying frame parameters used when
1056 @code{display-buffer} makes a new frame. @xref{Frame Parameters}, for
1057 more information about frame parameters.
1060 @defopt special-display-buffer-names
1061 A list of buffer names identifying buffers that should be displayed
1062 specially. If the name of @var{buffer-or-name} is in this list,
1063 @code{display-buffer} handles the buffer specially. By default, special
1064 display means to give the buffer a dedicated frame.
1066 If an element is a list, instead of a string, then the @sc{car} of that
1067 list is the buffer name, and the rest of that list says how to create
1068 the frame. There are two possibilities for the rest of that list (its
1069 @sc{cdr}): It can be an alist, specifying frame parameters, or it can
1070 contain a function and arguments to give to it. (The function's first
1071 argument is always the buffer to be displayed; the arguments from the
1072 list come after that.)
1077 (("myfile" (minibuffer) (menu-bar-lines . 0)))
1081 specifies to display a buffer named @samp{myfile} in a dedicated frame
1082 with specified @code{minibuffer} and @code{menu-bar-lines} parameters.
1084 The list of frame parameters can also use the phony frame parameters
1085 @code{same-frame} and @code{same-window}. If the specified frame
1086 parameters include @code{(same-window . @var{value})} and @var{value}
1087 is non-@code{nil}, that means to display the buffer in the current
1088 selected window. Otherwise, if they include @code{(same-frame .
1089 @var{value})} and @var{value} is non-@code{nil}, that means to display
1090 the buffer in a new window in the currently selected frame.
1093 @defopt special-display-regexps
1094 A list of regular expressions specifying buffers that should be
1095 displayed specially. If the buffer's name matches any of the regular
1096 expressions in this list, @code{display-buffer} handles the buffer
1097 specially. By default, special display means to give the buffer a
1100 If an element is a list, instead of a string, then the @sc{car} of the
1101 list is the regular expression, and the rest of the list says how to
1102 create the frame. See @code{special-display-buffer-names} above.
1105 @defun special-display-p buffer-name
1106 This function returns non-@code{nil} if displaying a buffer
1107 named @var{buffer-name} with @code{display-buffer} would
1108 create a special frame. The value is @code{t} if it would
1109 use the default frame parameters, or else the specified list
1110 of frame parameters.
1113 @defvar special-display-function
1114 This variable holds the function to call to display a buffer specially.
1115 It receives the buffer as an argument, and should return the window in
1116 which it is displayed. The default value of this variable is
1117 @code{special-display-popup-frame}, see below.
1120 @defun special-display-popup-frame buffer &optional args
1121 This function tries to make @var{buffer} visible in a frame of its own.
1122 If @var{buffer} is already displayed in some window, it makes that
1123 window's frame visible and raises it. Otherwise, it creates a frame
1124 that is dedicated to @var{buffer}. The return value is the window used
1125 to display @var{buffer}.
1127 If @var{args} is an alist, it specifies frame parameters for the new
1128 frame. If @var{args} is a list whose @sc{car} is a symbol, then
1129 @code{(car @var{args})} is called as a function to actually create and
1130 set up the frame; it is called with @var{buffer} as first argument, and
1131 @code{(cdr @var{args})} as additional arguments.
1133 This function always uses an existing window displaying @var{buffer},
1134 whether or not it is in a frame of its own; but if you set up the above
1135 variables in your init file, before @var{buffer} was created, then
1136 presumably the window was previously made by this function.
1139 @defopt special-display-frame-alist
1140 @anchor{Definition of special-display-frame-alist}
1141 This variable holds frame parameters for
1142 @code{special-display-popup-frame} to use when it creates a frame.
1145 @defopt same-window-buffer-names
1146 A list of buffer names for buffers that should be displayed in the
1147 selected window. If the buffer's name is in this list,
1148 @code{display-buffer} handles the buffer by switching to it in the
1152 @defopt same-window-regexps
1153 A list of regular expressions that specify buffers that should be
1154 displayed in the selected window. If the buffer's name matches any of
1155 the regular expressions in this list, @code{display-buffer} handles the
1156 buffer by switching to it in the selected window.
1159 @defun same-window-p buffer-name
1160 This function returns @code{t} if displaying a buffer
1161 named @var{buffer-name} with @code{display-buffer} would
1162 put it in the selected window.
1166 @defvar display-buffer-function
1167 This variable is the most flexible way to customize the behavior of
1168 @code{display-buffer}. If it is non-@code{nil}, it should be a function
1169 that @code{display-buffer} calls to do the work. The function should
1170 accept two arguments, the first two arguments that @code{display-buffer}
1171 received. It should choose or create a window, display the specified
1172 buffer in it, and then return the window.
1174 This variable takes precedence over all the other options described
1178 If all options described above fail to produce a suitable window,
1179 @code{display-buffer} tries to reuse an existing window. As a last
1180 resort, it will try to display @var{buffer-or-name} on a separate frame.
1181 In that case, the value of @code{pop-up-frames} is disregarded.
1183 @node Dedicated Windows
1184 @section Dedicated Windows
1185 @cindex dedicated window
1187 Functions for displaying a buffer can be told to not use specific
1188 windows by marking these window as @dfn{dedicated} to their buffers.
1189 @code{display-buffer} (@pxref{Choosing Window}) never uses a dedicated
1190 window for displaying another buffer in it. @code{get-lru-window} and
1191 @code{get-largest-window} (@pxref{Selecting Windows}) do not consider
1192 dedicated windows as candidates when their @var{dedicated} argument is
1193 non-@code{nil}. The behavior of @code{set-window-buffer}
1194 (@pxref{Buffers and Windows}) with respect to dedicated windows is
1195 slightly different, see below.
1197 When @code{delete-windows-on} (@pxref{Deleting Windows}) wants to delete
1198 a dedicated window and that window is the only window on its frame, it
1199 deletes the window's frame too, provided there are other frames left.
1200 @code{replace-buffer-in-windows} (@pxref{Displaying Buffers}) tries to
1201 delete all dedicated windows showing its buffer argument. When such a
1202 window is the only window on its frame, that frame is deleted, provided
1203 there are other frames left. If there are no more frames left, some
1204 other buffer is displayed in the window, and the window is marked as
1207 When you kill a buffer (@pxref{Killing Buffers}) displayed in a
1208 dedicated window, any such window usually gets deleted too, since
1209 @code{kill-buffer} calls @code{replace-buffer-in-windows} for cleaning
1210 up windows. Burying a buffer (@pxref{The Buffer List}) deletes the
1211 selected window if it is dedicated and shows that buffer. However, if
1212 that window is the only window on its frame, another buffer is displayed
1213 in it and the frame is iconified.
1215 @defun window-dedicated-p &optional window
1216 This function returns non-@code{nil} if @var{window} is dedicated to its
1217 buffer and @code{nil} otherwise. More precisely, the return value is
1218 the value assigned by the last call of @code{set-window-dedicated-p} for
1219 @var{window} or @code{nil} if that function was never called with
1220 @var{window} as its argument. The default for @var{window} is the
1224 @defun set-window-dedicated-p window flag
1225 This function marks @var{window} as dedicated to its buffer if
1226 @var{flag} is non-@code{nil}, and non-dedicated otherwise.
1228 As a special case, if @var{flag} is @code{t}, @var{window} becomes
1229 @dfn{strongly} dedicated to its buffer. @code{set-window-buffer}
1230 signals an error when the window it acts upon is strongly dedicated to
1231 its buffer and does not already display the buffer it is asked to
1232 display. In any other case, @code{set-window-buffer} will display
1233 another buffer in that window. Other functions do not treat @code{t}
1234 differently from any non-@code{nil} value.
1238 @section Windows and Point
1239 @cindex window position
1240 @cindex window point
1241 @cindex position in window
1242 @cindex point in window
1244 Each window has its own value of point (@pxref{Point}), independent of
1245 the value of point in other windows displaying the same buffer. This
1246 makes it useful to have multiple windows showing one buffer.
1250 The window point is established when a window is first created; it is
1251 initialized from the buffer's point, or from the window point of another
1252 window opened on the buffer if such a window exists.
1255 Selecting a window sets the value of point in its buffer from the
1256 window's value of point. Conversely, deselecting a window sets the
1257 window's value of point from that of the buffer. Thus, when you switch
1258 between windows that display a given buffer, the point value for the
1259 selected window is in effect in the buffer, while the point values for
1260 the other windows are stored in those windows.
1263 As long as the selected window displays the current buffer, the window's
1264 point and the buffer's point always move together; they remain equal.
1268 As far as the user is concerned, point is where the cursor is, and
1269 when the user switches to another buffer, the cursor jumps to the
1270 position of point in that buffer.
1272 @defun window-point &optional window
1273 This function returns the current position of point in @var{window}.
1274 For a nonselected window, this is the value point would have (in that
1275 window's buffer) if that window were selected. The default for
1276 @var{window} is the selected window.
1278 When @var{window} is the selected window and its buffer is also the
1279 current buffer, the value returned is the same as point in that buffer.
1280 Strictly speaking, it would be more correct to return the ``top-level''
1281 value of point, outside of any @code{save-excursion} forms. But that
1282 value is hard to find.
1285 @defun set-window-point window position
1286 This function positions point in @var{window} at position
1287 @var{position} in @var{window}'s buffer. It returns @var{position}.
1289 If @var{window} is selected, and its buffer is current,
1290 this simply does @code{goto-char}.
1293 @defvar window-point-insertion-type
1294 This variable specifies the marker insertion type (@pxref{Marker
1295 Insertion Types}) of @code{window-point}. The default is @code{nil},
1296 so @code{window-point} will stay behind text inserted there.
1299 @node Window Start and End
1300 @section The Window Start and End Positions
1301 @cindex window start position
1303 Each window maintains a marker used to keep track of a buffer position
1304 that specifies where in the buffer display should start. This position
1305 is called the @dfn{display-start} position of the window (or just the
1306 @dfn{start}). The character after this position is the one that appears
1307 at the upper left corner of the window. It is usually, but not
1308 inevitably, at the beginning of a text line.
1310 After switching windows or buffers, and in some other cases, if the
1311 window start is in the middle of a line, Emacs adjusts the window
1312 start to the start of a line. This prevents certain operations from
1313 leaving the window start at a meaningless point within a line. This
1314 feature may interfere with testing some Lisp code by executing it
1315 using the commands of Lisp mode, because they trigger this
1316 readjustment. To test such code, put it into a command and bind the
1319 @defun window-start &optional window
1320 @cindex window top line
1321 This function returns the display-start position of window
1322 @var{window}. If @var{window} is @code{nil}, the selected window is
1332 When you create a window, or display a different buffer in it, the
1333 display-start position is set to a display-start position recently used
1334 for the same buffer, or to @code{point-min} if the buffer doesn't have
1337 Redisplay updates the window-start position (if you have not specified
1338 it explicitly since the previous redisplay)---to make sure point appears
1339 on the screen. Nothing except redisplay automatically changes the
1340 window-start position; if you move point, do not expect the window-start
1341 position to change in response until after the next redisplay.
1343 For a realistic example of using @code{window-start}, see the
1344 description of @code{count-lines}. @xref{Definition of count-lines}.
1347 @cindex window end position
1348 @defun window-end &optional window update
1349 This function returns the position where display of its buffer ends in
1350 @var{window}. The default for @var{window} is the selected window.
1352 Simply changing the buffer text or moving point does not update the
1353 value that @code{window-end} returns. The value is updated only when
1354 Emacs redisplays and redisplay completes without being preempted.
1356 If the last redisplay of @var{window} was preempted, and did not finish,
1357 Emacs does not know the position of the end of display in that window.
1358 In that case, this function returns @code{nil}.
1360 If @var{update} is non-@code{nil}, @code{window-end} always returns an
1361 up-to-date value for where display ends, based on the current
1362 @code{window-start} value. If a previously saved value of that position
1363 is still valid, @code{window-end} returns that value; otherwise it
1364 computes the correct value by scanning the buffer text.
1366 Even if @var{update} is non-@code{nil}, @code{window-end} does not
1367 attempt to scroll the display if point has moved off the screen, the
1368 way real redisplay would do. It does not alter the
1369 @code{window-start} value. In effect, it reports where the displayed
1370 text will end if scrolling is not required.
1373 @defun set-window-start window position &optional noforce
1374 This function sets the display-start position of @var{window} to
1375 @var{position} in @var{window}'s buffer. It returns @var{position}.
1377 The display routines insist that the position of point be visible when a
1378 buffer is displayed. Normally, they change the display-start position
1379 (that is, scroll the window) whenever necessary to make point visible.
1380 However, if you specify the start position with this function using
1381 @code{nil} for @var{noforce}, it means you want display to start at
1382 @var{position} even if that would put the location of point off the
1383 screen. If this does place point off screen, the display routines move
1384 point to the left margin on the middle line in the window.
1386 For example, if point @w{is 1} and you set the start of the window
1387 @w{to 37}, the start of the next line, point will be ``above'' the top
1388 of the window. The display routines will automatically move point if
1389 it is still 1 when redisplay occurs. Here is an example:
1393 ;; @r{Here is what @samp{foo} looks like before executing}
1394 ;; @r{the @code{set-window-start} expression.}
1398 ---------- Buffer: foo ----------
1399 @point{}This is the contents of buffer foo.
1405 ---------- Buffer: foo ----------
1419 ;; @r{Here is what @samp{foo} looks like after executing}
1420 ;; @r{the @code{set-window-start} expression.}
1421 ---------- Buffer: foo ----------
1427 ---------- Buffer: foo ----------
1431 If @var{noforce} is non-@code{nil}, and @var{position} would place point
1432 off screen at the next redisplay, then redisplay computes a new window-start
1433 position that works well with point, and thus @var{position} is not used.
1436 @defun pos-visible-in-window-p &optional position window partially
1437 This function returns non-@code{nil} if @var{position} is within the
1438 range of text currently visible on the screen in @var{window}. It
1439 returns @code{nil} if @var{position} is scrolled vertically out of view.
1440 Locations that are partially obscured are not considered visible unless
1441 @var{partially} is non-@code{nil}. The argument @var{position} defaults
1442 to the current position of point in @var{window}; @var{window}, to the
1443 selected window. If @var{position} is @code{t}, that means to check the
1444 last visible position in @var{window}.
1446 The @code{pos-visible-in-window-p} function considers only vertical
1447 scrolling. If @var{position} is out of view only because @var{window}
1448 has been scrolled horizontally, @code{pos-visible-in-window-p} returns
1449 non-@code{nil} anyway. @xref{Horizontal Scrolling}.
1451 If @var{position} is visible, @code{pos-visible-in-window-p} returns
1452 @code{t} if @var{partially} is @code{nil}; if @var{partially} is
1453 non-@code{nil}, and the character following @var{position} is fully
1454 visible, it returns a list of the form @code{(@var{x} @var{y})}, where
1455 @var{x} and @var{y} are the pixel coordinates relative to the top left
1456 corner of the window; otherwise it returns an extended list of the form
1457 @code{(@var{x} @var{y} @var{rtop} @var{rbot} @var{rowh} @var{vpos})},
1458 where @var{rtop} and @var{rbot} specify the number of off-window pixels
1459 at the top and bottom of the row at @var{position}, @var{rowh} specifies
1460 the visible height of that row, and @var{vpos} specifies the vertical
1461 position (zero-based row number) of that row.
1467 ;; @r{If point is off the screen now, recenter it now.}
1468 (or (pos-visible-in-window-p
1469 (point) (selected-window))
1475 @defun window-line-height &optional line window
1476 This function returns the height of text line @var{line} in
1477 @var{window}. If @var{line} is one of @code{header-line} or
1478 @code{mode-line}, @code{window-line-height} returns information about
1479 the corresponding line of the window. Otherwise, @var{line} is a text
1480 line number starting from 0. A negative number counts from the end of
1481 the window. The default for @var{line} is the current line in
1482 @var{window}; the default for @var{window} is the selected window.
1484 If the display is not up to date, @code{window-line-height} returns
1485 @code{nil}. In that case, @code{pos-visible-in-window-p} may be used
1486 to obtain related information.
1488 If there is no line corresponding to the specified @var{line},
1489 @code{window-line-height} returns @code{nil}. Otherwise, it returns
1490 a list @code{(@var{height} @var{vpos} @var{ypos} @var{offbot})},
1491 where @var{height} is the height in pixels of the visible part of the
1492 line, @var{vpos} and @var{ypos} are the vertical position in lines and
1493 pixels of the line relative to the top of the first text line, and
1494 @var{offbot} is the number of off-window pixels at the bottom of the
1495 text line. If there are off-window pixels at the top of the (first)
1496 text line, @var{ypos} is negative.
1499 @node Textual Scrolling
1500 @section Textual Scrolling
1501 @cindex textual scrolling
1502 @cindex scrolling textually
1504 @dfn{Textual scrolling} means moving the text up or down through a
1505 window. It works by changing the value of the window's display-start
1506 location. It may also change the value of @code{window-point} to keep
1507 point on the screen.
1509 Textual scrolling was formerly called ``vertical scrolling,'' but we
1510 changed its name to distinguish it from the new vertical fractional
1511 scrolling feature (@pxref{Vertical Scrolling}).
1513 In the commands @code{scroll-up} and @code{scroll-down}, the directions
1514 ``up'' and ``down'' refer to the motion of the text in the buffer at which
1515 you are looking through the window. Imagine that the text is
1516 written on a long roll of paper and that the scrolling commands move the
1517 paper up and down. Thus, if you are looking at text in the middle of a
1518 buffer and repeatedly call @code{scroll-down}, you will eventually see
1519 the beginning of the buffer.
1521 Some people have urged that the opposite convention be used: they
1522 imagine that the window moves over text that remains in place. Then
1523 ``down'' commands would take you to the end of the buffer. This view is
1524 more consistent with the actual relationship between windows and the
1525 text in the buffer, but it is less like what the user sees. The
1526 position of a window on the terminal does not move, and short scrolling
1527 commands clearly move the text up or down on the screen. We have chosen
1528 names that fit the user's point of view.
1530 The textual scrolling functions (aside from
1531 @code{scroll-other-window}) have unpredictable results if the current
1532 buffer is different from the buffer that is displayed in the selected
1533 window. @xref{Current Buffer}.
1535 If the window contains a row which is taller than the height of the
1536 window (for example in the presence of a large image), the scroll
1537 functions will adjust the window vscroll to scroll the partially
1538 visible row. To disable this feature, Lisp code may bind the variable
1539 `auto-window-vscroll' to @code{nil} (@pxref{Vertical Scrolling}).
1541 @deffn Command scroll-up &optional count
1542 This function scrolls the text in the selected window upward
1543 @var{count} lines. If @var{count} is negative, scrolling is actually
1546 If @var{count} is @code{nil} (or omitted), then the length of scroll
1547 is @code{next-screen-context-lines} lines less than the usable height of
1548 the window (not counting its mode line).
1550 @code{scroll-up} returns @code{nil}, unless it gets an error
1551 because it can't scroll any further.
1554 @deffn Command scroll-down &optional count
1555 This function scrolls the text in the selected window downward
1556 @var{count} lines. If @var{count} is negative, scrolling is actually
1559 If @var{count} is omitted or @code{nil}, then the length of the scroll
1560 is @code{next-screen-context-lines} lines less than the usable height of
1561 the window (not counting its mode line).
1563 @code{scroll-down} returns @code{nil}, unless it gets an error because
1564 it can't scroll any further.
1567 @deffn Command scroll-other-window &optional count
1568 This function scrolls the text in another window upward @var{count}
1569 lines. Negative values of @var{count}, or @code{nil}, are handled
1570 as in @code{scroll-up}.
1572 You can specify which buffer to scroll by setting the variable
1573 @code{other-window-scroll-buffer} to a buffer. If that buffer isn't
1574 already displayed, @code{scroll-other-window} displays it in some
1577 When the selected window is the minibuffer, the next window is normally
1578 the one at the top left corner. You can specify a different window to
1579 scroll, when the minibuffer is selected, by setting the variable
1580 @code{minibuffer-scroll-window}. This variable has no effect when any
1581 other window is selected. When it is non-@code{nil} and the
1582 minibuffer is selected, it takes precedence over
1583 @code{other-window-scroll-buffer}. @xref{Definition of
1584 minibuffer-scroll-window}.
1586 When the minibuffer is active, it is the next window if the selected
1587 window is the one at the bottom right corner. In this case,
1588 @code{scroll-other-window} attempts to scroll the minibuffer. If the
1589 minibuffer contains just one line, it has nowhere to scroll to, so the
1590 line reappears after the echo area momentarily displays the message
1591 @samp{Beginning of buffer}.
1595 @defvar other-window-scroll-buffer
1596 If this variable is non-@code{nil}, it tells @code{scroll-other-window}
1597 which buffer's window to scroll.
1600 @defopt scroll-margin
1601 This option specifies the size of the scroll margin---a minimum number
1602 of lines between point and the top or bottom of a window. Whenever
1603 point gets within this many lines of the top or bottom of the window,
1604 redisplay scrolls the text automatically (if possible) to move point
1605 out of the margin, closer to the center of the window.
1608 @defopt scroll-conservatively
1609 This variable controls how scrolling is done automatically when point
1610 moves off the screen (or into the scroll margin). If the value is a
1611 positive integer @var{n}, then redisplay scrolls the text up to
1612 @var{n} lines in either direction, if that will bring point back into
1613 proper view. This behavior is called @dfn{conservative scrolling}.
1614 Otherwise, scrolling happens in the usual way, under the control of
1615 other variables such as @code{scroll-up-aggressively} and
1616 @code{scroll-down-aggressively}.
1618 The default value is zero, which means that conservative scrolling
1622 @defopt scroll-down-aggressively
1623 The value of this variable should be either @code{nil} or a fraction
1624 @var{f} between 0 and 1. If it is a fraction, that specifies where on
1625 the screen to put point when scrolling down. More precisely, when a
1626 window scrolls down because point is above the window start, the new
1627 start position is chosen to put point @var{f} part of the window
1628 height from the top. The larger @var{f}, the more aggressive the
1631 A value of @code{nil} is equivalent to .5, since its effect is to center
1632 point. This variable automatically becomes buffer-local when set in any
1636 @defopt scroll-up-aggressively
1637 Likewise, for scrolling up. The value, @var{f}, specifies how far
1638 point should be placed from the bottom of the window; thus, as with
1639 @code{scroll-up-aggressively}, a larger value scrolls more aggressively.
1643 This variable is an older variant of @code{scroll-conservatively}. The
1644 difference is that it if its value is @var{n}, that permits scrolling
1645 only by precisely @var{n} lines, not a smaller number. This feature
1646 does not work with @code{scroll-margin}. The default value is zero.
1649 @defopt scroll-preserve-screen-position
1650 If this option is @code{t}, scrolling which would move the current
1651 point position out of the window chooses the new position of point
1652 so that the vertical position of the cursor is unchanged, if possible.
1654 If it is non-@code{nil} and not @code{t}, then the scrolling functions
1655 always preserve the vertical position of point, if possible.
1658 @defopt next-screen-context-lines
1659 The value of this variable is the number of lines of continuity to
1660 retain when scrolling by full screens. For example, @code{scroll-up}
1661 with an argument of @code{nil} scrolls so that this many lines at the
1662 bottom of the window appear instead at the top. The default value is
1666 @deffn Command recenter &optional count
1667 @cindex centering point
1668 This function scrolls the text in the selected window so that point is
1669 displayed at a specified vertical position within the window. It does
1670 not ``move point'' with respect to the text.
1672 If @var{count} is a nonnegative number, that puts the line containing
1673 point @var{count} lines down from the top of the window. If
1674 @var{count} is a negative number, then it counts upward from the
1675 bottom of the window, so that @minus{}1 stands for the last usable
1676 line in the window. If @var{count} is a non-@code{nil} list, then it
1677 stands for the line in the middle of the window.
1679 If @var{count} is @code{nil}, @code{recenter} puts the line containing
1680 point in the middle of the window, then clears and redisplays the entire
1683 When @code{recenter} is called interactively, @var{count} is the raw
1684 prefix argument. Thus, typing @kbd{C-u} as the prefix sets the
1685 @var{count} to a non-@code{nil} list, while typing @kbd{C-u 4} sets
1686 @var{count} to 4, which positions the current line four lines from the
1689 With an argument of zero, @code{recenter} positions the current line at
1690 the top of the window. This action is so handy that some people make a
1691 separate key binding to do this. For example,
1695 (defun line-to-top-of-window ()
1696 "Scroll current line to top of window.
1697 Replaces three keystroke sequence C-u 0 C-l."
1701 (global-set-key [kp-multiply] 'line-to-top-of-window)
1706 @node Vertical Scrolling
1707 @section Vertical Fractional Scrolling
1708 @cindex vertical fractional scrolling
1709 @cindex vertical scroll position
1711 @dfn{Vertical fractional scrolling} means shifting text in a window up
1712 or down by a specified multiple or fraction of a line. Each window has
1713 a @dfn{vertical scroll position}, which is a number, never less than
1714 zero. It specifies how far to raise the contents of the window.
1715 Raising the window contents generally makes all or part of some lines
1716 disappear off the top, and all or part of some other lines appear at the
1717 bottom. The usual value is zero.
1719 The vertical scroll position is measured in units of the normal line
1720 height, which is the height of the default font. Thus, if the value is
1721 .5, that means the window contents are scrolled up half the normal line
1722 height. If it is 3.3, that means the window contents are scrolled up
1723 somewhat over three times the normal line height.
1725 What fraction of a line the vertical scrolling covers, or how many
1726 lines, depends on what the lines contain. A value of .5 could scroll a
1727 line whose height is very short off the screen, while a value of 3.3
1728 could scroll just part of the way through a tall line or an image.
1730 @defun window-vscroll &optional window pixels-p
1731 This function returns the current vertical scroll position of
1732 @var{window}. The default for @var{window} is the selected window.
1733 If @var{pixels-p} is non-@code{nil}, the return value is measured in
1734 pixels, rather than in units of the normal line height.
1744 @defun set-window-vscroll window lines &optional pixels-p
1745 This function sets @var{window}'s vertical scroll position to
1746 @var{lines}. If @var{window} is @code{nil}, the selected window is
1747 used. The argument @var{lines} should be zero or positive; if not, it
1751 The actual vertical scroll position must always correspond
1752 to an integral number of pixels, so the value you specify
1753 is rounded accordingly.
1755 The return value is the result of this rounding.
1759 (set-window-vscroll (selected-window) 1.2)
1764 If @var{pixels-p} is non-@code{nil}, @var{lines} specifies a number of
1765 pixels. In this case, the return value is @var{lines}.
1768 @defvar auto-window-vscroll
1769 If this variable is non-@code{nil}, the line-move, scroll-up, and
1770 scroll-down functions will automatically modify the vertical scroll
1771 position to scroll through display rows that are taller that the height
1772 of the window, for example in the presence of large images.
1775 @node Horizontal Scrolling
1776 @section Horizontal Scrolling
1777 @cindex horizontal scrolling
1779 @dfn{Horizontal scrolling} means shifting the image in the window left
1780 or right by a specified multiple of the normal character width. Each
1781 window has a @dfn{horizontal scroll position}, which is a number, never
1782 less than zero. It specifies how far to shift the contents left.
1783 Shifting the window contents left generally makes all or part of some
1784 characters disappear off the left, and all or part of some other
1785 characters appear at the right. The usual value is zero.
1787 The horizontal scroll position is measured in units of the normal
1788 character width, which is the width of space in the default font. Thus,
1789 if the value is 5, that means the window contents are scrolled left by 5
1790 times the normal character width. How many characters actually
1791 disappear off to the left depends on their width, and could vary from
1794 Because we read from side to side in the ``inner loop,'' and from top
1795 to bottom in the ``outer loop,'' the effect of horizontal scrolling is
1796 not like that of textual or vertical scrolling. Textual scrolling
1797 involves selection of a portion of text to display, and vertical
1798 scrolling moves the window contents contiguously; but horizontal
1799 scrolling causes part of @emph{each line} to go off screen.
1801 Usually, no horizontal scrolling is in effect; then the leftmost
1802 column is at the left edge of the window. In this state, scrolling to
1803 the right is meaningless, since there is no data to the left of the edge
1804 to be revealed by it; so this is not allowed. Scrolling to the left is
1805 allowed; it scrolls the first columns of text off the edge of the window
1806 and can reveal additional columns on the right that were truncated
1807 before. Once a window has a nonzero amount of leftward horizontal
1808 scrolling, you can scroll it back to the right, but only so far as to
1809 reduce the net horizontal scroll to zero. There is no limit to how far
1810 left you can scroll, but eventually all the text will disappear off the
1813 @vindex auto-hscroll-mode
1814 If @code{auto-hscroll-mode} is set, redisplay automatically alters
1815 the horizontal scrolling of a window as necessary to ensure that point
1816 is always visible. However, you can still set the horizontal
1817 scrolling value explicitly. The value you specify serves as a lower
1818 bound for automatic scrolling, i.e. automatic scrolling will not
1819 scroll a window to a column less than the specified one.
1821 @deffn Command scroll-left &optional count set-minimum
1822 This function scrolls the selected window @var{count} columns to the
1823 left (or to the right if @var{count} is negative). The default
1824 for @var{count} is the window width, minus 2.
1826 The return value is the total amount of leftward horizontal scrolling in
1827 effect after the change---just like the value returned by
1828 @code{window-hscroll} (below).
1830 Once you scroll a window as far right as it can go, back to its normal
1831 position where the total leftward scrolling is zero, attempts to scroll
1832 any farther right have no effect.
1834 If @var{set-minimum} is non-@code{nil}, the new scroll amount becomes
1835 the lower bound for automatic scrolling; that is, automatic scrolling
1836 will not scroll a window to a column less than the value returned by
1837 this function. Interactive calls pass non-@code{nil} for
1841 @deffn Command scroll-right &optional count set-minimum
1842 This function scrolls the selected window @var{count} columns to the
1843 right (or to the left if @var{count} is negative). The default
1844 for @var{count} is the window width, minus 2. Aside from the direction
1845 of scrolling, this works just like @code{scroll-left}.
1848 @defun window-hscroll &optional window
1849 This function returns the total leftward horizontal scrolling of
1850 @var{window}---the number of columns by which the text in @var{window}
1851 is scrolled left past the left margin. The default for
1852 @var{window} is the selected window.
1854 The return value is never negative. It is zero when no horizontal
1855 scrolling has been done in @var{window} (which is usually the case).
1874 @defun set-window-hscroll window columns
1875 This function sets horizontal scrolling of @var{window}. The value of
1876 @var{columns} specifies the amount of scrolling, in terms of columns
1877 from the left margin. The argument @var{columns} should be zero or
1878 positive; if not, it is taken as zero. Fractional values of
1879 @var{columns} are not supported at present.
1881 Note that @code{set-window-hscroll} may appear not to work if you test
1882 it by evaluating a call with @kbd{M-:} in a simple way. What happens
1883 is that the function sets the horizontal scroll value and returns, but
1884 then redisplay adjusts the horizontal scrolling to make point visible,
1885 and this overrides what the function did. You can observe the
1886 function's effect if you call it while point is sufficiently far from
1887 the left margin that it will remain visible.
1889 The value returned is @var{columns}.
1893 (set-window-hscroll (selected-window) 10)
1899 Here is how you can determine whether a given position @var{position} is
1900 off the screen due to horizontal scrolling:
1904 (defun hscroll-on-screen (window position)
1906 (goto-char position)
1908 (>= (- (current-column) (window-hscroll window)) 0)
1909 (< (- (current-column) (window-hscroll window))
1910 (window-width window)))))
1914 @node Size of Window
1915 @section The Size of a Window
1917 @cindex size of window
1919 An Emacs window is rectangular, and its size information consists of
1920 the height (the number of lines) and the width (the number of character
1921 positions in each line). The mode line is included in the height. But
1922 the width does not count the scroll bar or the column of @samp{|}
1923 characters that separates side-by-side windows.
1925 The following three functions return size information about a window:
1927 @defun window-height &optional window
1928 This function returns the number of lines in @var{window}, including its
1929 mode line and header line, if any. If @var{window} fills its entire
1930 frame except for the echo area, this is typically one less than the
1931 value of @code{frame-height} on that frame. The default for
1932 @var{window} is the selected window.
1940 (split-window-vertically)
1941 @result{} #<window 4 on windows.texi>
1950 @defun window-body-height &optional window
1951 Like @code{window-height} but the value does not include the
1952 mode line (if any) or the header line (if any).
1955 @defun window-width &optional window
1956 This function returns the number of columns in @var{window}. The
1957 default for @var{window} is the selected window.
1959 The return value does not include the window's scroll bar or the column
1960 of @samp{|} characters that separates side-by-side windows. Moreover,
1961 the return value does not include the space used for displaying fringes
1962 and margins. Hence you cannot, in general, compare the return values of
1963 @code{window-width} and @code{frame-width} for equality to determine
1964 whether a window is a wide as the containing frame. Use the function
1965 @code{window-full-width-p}, see below, instead.
1975 @defun window-full-width-p &optional window
1976 This function returns non-@code{nil} if @var{window} is as wide as the
1977 frame that contains it; otherwise @code{nil}. The default for
1978 @var{window} is the selected window.
1981 @defun window-edges &optional window
1982 This function returns a list of the edge coordinates of @var{window}.
1983 The default for @var{window} is the selected window.
1985 The order of the list is @code{(@var{left} @var{top} @var{right}
1986 @var{bottom})}, all elements relative to 0, 0 at the top left corner of
1987 the frame. The element @var{right} of the value is one more than the
1988 rightmost column used by @var{window}, and @var{bottom} is one more than
1989 the bottommost row used by @var{window} and its mode-line.
1991 The edges include the space used by the window's scroll bar, display
1992 margins, fringes, header line, and mode line, if it has them. Also,
1993 if the window has a neighbor on the right, its right edge value
1994 includes the width of the separator line between the window and that
1995 neighbor. Since the width of the window does not include this
1996 separator, the width does not usually equal the difference between the
1997 right and left edges.
2000 @defun window-inside-edges &optional window
2001 This is similar to @code{window-edges}, but the edge values
2002 it returns include only the text area of the window. They
2003 do not include the header line, mode line, scroll bar or
2004 vertical separator, fringes, or display margins.
2007 Here are the results obtained on a typical 24-line terminal with just
2008 one window, with menu bar enabled:
2012 (window-edges (selected-window))
2013 @result{} (0 1 80 23)
2016 (window-inside-edges (selected-window))
2017 @result{} (0 1 80 22)
2022 The bottom edge is at line 23 because the last line is the echo area.
2023 The bottom inside edge is at line 22, which is the window's mode line.
2025 If @var{window} is at the upper left corner of its frame, and there is
2026 no menu bar, then @var{bottom} returned by @code{window-edges} is the
2027 same as the value of @code{(window-height)}, @var{right} is almost the
2028 same as the value of @code{(window-width)}, and @var{top} and
2029 @var{left} are zero. For example, the edges of the following window
2030 are @w{@samp{0 0 8 5}}. Assuming that the frame has more than 8
2031 columns, the last column of the window (column 7) holds a border
2032 rather than text. The last row (row 4) holds the mode line, shown
2033 here with @samp{xxxxxxxxx}.
2049 In the following example, let's suppose that the frame is 7
2050 columns wide. Then the edges of the left window are @w{@samp{0 0 4 3}}
2051 and the edges of the right window are @w{@samp{4 0 7 3}}.
2052 The inside edges of the left window are @w{@samp{0 0 3 2}},
2053 and the inside edges of the right window are @w{@samp{4 0 7 2}},
2066 @defun window-pixel-edges &optional window
2067 This function is like @code{window-edges} except that, on a graphical
2068 display, the edge values are measured in pixels instead of in
2069 character lines and columns.
2072 @defun window-inside-pixel-edges &optional window
2073 This function is like @code{window-inside-edges} except that, on a
2074 graphical display, the edge values are measured in pixels instead of
2075 in character lines and columns.
2078 @node Resizing Windows
2079 @section Changing the Size of a Window
2080 @cindex window resizing
2081 @cindex resize window
2082 @cindex changing window size
2083 @cindex window size, changing
2085 The window size functions fall into two classes: high-level commands
2086 that change the size of windows and low-level functions that access
2087 window size. Emacs does not permit overlapping windows or gaps between
2088 windows, so resizing a window always affects at least one other window.
2090 @deffn Command enlarge-window size &optional horizontal
2091 This function makes the selected window @var{size} lines taller by
2092 stealing lines from windows above or below. In a first round, it takes
2093 lines from one window at a time until that window is
2094 @code{window-min-height} lines tall, then takes from another. If, at
2095 the end of the first round, the selected window is still not tall
2096 enough, @code{enlarge-window} starts a second round, where it deletes
2097 windows above or below the selected one.
2099 If @var{horizontal} is non-@code{nil}, this function makes the window
2100 @var{size} columns wider, stealing columns instead of lines. If a
2101 window from which columns are stolen shrinks below
2102 @code{window-min-width} columns, that window disappears.
2104 If the requested size would exceed that of the window's frame, then the
2105 function makes the window occupy the entire height (or width) of the
2108 If there are various other windows from which lines or columns can be
2109 stolen, and some of them specify fixed size (using
2110 @code{window-size-fixed}, see below), they are left untouched while
2111 other windows are ``robbed.'' If it would be necessary to alter the
2112 size of a fixed-size window, @code{enlarge-window} gets an error
2115 If @var{size} is negative, this function shrinks the selected window by
2116 @minus{}@var{size} lines or columns. If that makes the window smaller
2117 than the minimum size (@code{window-min-height} and
2118 @code{window-min-width}), then @code{enlarge-window} deletes the window.
2120 @code{enlarge-window} returns @code{nil}.
2123 @deffn Command enlarge-window-horizontally columns
2124 This function makes the selected window @var{columns} wider.
2125 It could be defined as follows:
2129 (defun enlarge-window-horizontally (columns)
2131 (enlarge-window columns t))
2136 @deffn Command shrink-window size &optional horizontal
2137 This function is like @code{enlarge-window} but negates the argument
2138 @var{size}, making the selected window smaller by giving lines (or
2139 columns) to the other windows. If the window shrinks below
2140 @code{window-min-height} or @code{window-min-width}, then it disappears.
2142 If @var{size} is negative, the window is enlarged by @minus{}@var{size}
2146 @deffn Command shrink-window-horizontally columns
2147 This function makes the selected window @var{columns} narrower.
2148 It could be defined as follows:
2152 (defun shrink-window-horizontally (columns)
2154 (shrink-window columns t))
2159 @defun adjust-window-trailing-edge window delta horizontal
2160 This function makes the selected window @var{delta} lines taller or
2161 @var{delta} columns wider, by moving the bottom or right edge. This
2162 function does not delete other windows; if it cannot make the
2163 requested size adjustment, it signals an error. On success, this
2164 function returns @code{nil}.
2167 @defun fit-window-to-buffer &optional window max-height min-height
2168 This function makes @var{window} the right height to display its
2169 contents exactly. The default for @var{window} is the selected
2172 The argument @var{max-height} specifies the maximum height the window
2173 is allowed to be; @code{nil} means use the frame height. The argument
2174 @var{min-height} specifies the minimum height for the window;
2175 @code{nil} means use @code{window-min-height}. All these height
2176 values include the mode line and/or header line.
2179 @deffn Command shrink-window-if-larger-than-buffer &optional window
2180 This command shrinks @var{window} vertically to be as small as possible
2181 while still showing the full contents of its buffer---but not less than
2182 @code{window-min-height} lines. The default for @var{window} is
2183 the selected window.
2185 However, this command does nothing if the window is already too small to
2186 display the whole text of the buffer, or if part of the contents are
2187 currently scrolled off screen, or if the window is not the full width of
2188 its frame, or if the window is the only window in its frame.
2190 This command returns non-@code{nil} if it actually shrank the window
2191 and @code{nil} otherwise.
2194 @cindex fixed-size window
2195 @defvar window-size-fixed
2196 If this variable is non-@code{nil}, in a given buffer, then the size of
2197 any window displaying that buffer remains fixed unless you either
2198 explicitly change it or Emacs has no other choice.
2200 If the value is @code{height}, then only the window's height is fixed;
2201 if the value is @code{width}, then only the window's width is fixed.
2202 Any other non-@code{nil} value fixes both the width and the height.
2204 This variable automatically becomes buffer-local when set.
2206 Explicit size-change functions such as @code{enlarge-window}
2207 get an error if they would have to change a window size which is fixed.
2208 Therefore, when you want to change the size of such a window,
2209 you should bind @code{window-size-fixed} to @code{nil}, like this:
2212 (let ((window-size-fixed nil))
2213 (enlarge-window 10))
2216 Deleting an adjacent window or changing the frame size may change the
2217 size of a fixed-size window, if there is no other alternative.
2220 @cindex minimum window size
2221 The following two variables constrain the window-structure-changing
2222 functions to a minimum height and width.
2224 @defopt window-min-height
2225 The value of this variable specifies how short a window may become
2226 before it is automatically deleted. Making a window smaller than
2227 @code{window-min-height} automatically deletes it, and no window may be
2228 created shorter than this. The value is measured in line units. When
2229 the window wants a mode line and/or a header line, they are counted as
2230 one line each. The default value is @code{4}. A value less than
2231 @code{1} is ignored.
2234 @defopt window-min-width
2235 The value of this variable specifies how narrow a window may become
2236 before it is automatically deleted. Making a window smaller than
2237 @code{window-min-width} automatically deletes it, and no window may be
2238 created narrower than this. The value is measured in characters and
2239 includes any fringes or the scroll bar. The default value is @code{10}.
2240 A value less than @code{2} is ignored.
2243 @cindex balancing window sizes
2244 Emacs provides two functions to balance windows, that is, to even out
2245 the sizes of windows on the same frame. The minibuffer window and
2246 fixed-size windows are not resized by these functions.
2248 @deffn Command balance-windows &optional window-or-frame
2249 This function balances windows in a way that gives more space to
2250 full-width and/or full-height windows. If @var{window-or-frame}
2251 specifies a frame, it balances all windows on that frame. If
2252 @var{window-or-frame} specifies a window, it balances this window and
2253 its ``siblings'' only. Think of a sibling as the other (original or
2254 new) window with respect to the present one, involved in the process of
2255 splitting; see @ref{Splitting Windows}. Since a sibling may have been
2256 split again, a window can have more than one sibling.
2259 @deffn Command balance-windows-area
2260 This function attempts to give all windows on the selected frame
2261 approximately the same share of the screen area. This means that
2262 full-width or full-height windows are not given more space than other
2266 @node Coordinates and Windows
2267 @section Coordinates and Windows
2269 This section describes how to relate screen coordinates to windows.
2271 @defun window-at x y &optional frame
2272 This function returns the window containing the specified cursor
2273 position in the frame @var{frame}. The coordinates @var{x} and @var{y}
2274 are measured in characters and count from the top left corner of the
2275 frame. If they are out of range, @code{window-at} returns @code{nil}.
2277 If you omit @var{frame}, the selected frame is used.
2280 @defun coordinates-in-window-p coordinates window
2281 This function checks whether a particular frame position falls within
2282 the window @var{window}.
2284 The argument @var{coordinates} is a cons cell of the form @code{(@var{x}
2285 . @var{y})}. The coordinates @var{x} and @var{y} are measured in
2286 characters, and count from the top left corner of the screen or frame.
2288 The value returned by @code{coordinates-in-window-p} is non-@code{nil}
2289 if the coordinates are inside @var{window}. The value also indicates
2290 what part of the window the position is in, as follows:
2293 @item (@var{relx} . @var{rely})
2294 The coordinates are inside @var{window}. The numbers @var{relx} and
2295 @var{rely} are the equivalent window-relative coordinates for the
2296 specified position, counting from 0 at the top left corner of the
2300 The coordinates are in the mode line of @var{window}.
2303 The coordinates are in the header line of @var{window}.
2306 The coordinates are in the vertical line between @var{window} and its
2307 neighbor to the right. This value occurs only if the window doesn't
2308 have a scroll bar; positions in a scroll bar are considered outside the
2309 window for these purposes.
2313 The coordinates are in the left or right fringe of the window.
2317 The coordinates are in the left or right margin of the window.
2320 The coordinates are not in any part of @var{window}.
2323 The function @code{coordinates-in-window-p} does not require a frame as
2324 argument because it always uses the frame that @var{window} is on.
2328 @section The Window Tree
2331 A @dfn{window tree} specifies the layout, size, and relationship
2332 between all windows in one frame.
2334 @defun window-tree &optional frame
2335 This function returns the window tree for frame @var{frame}.
2336 If @var{frame} is omitted, the selected frame is used.
2338 The return value is a list of the form @code{(@var{root} @var{mini})},
2339 where @var{root} represents the window tree of the frame's
2340 root window, and @var{mini} is the frame's minibuffer window.
2342 If the root window is not split, @var{root} is the root window itself.
2343 Otherwise, @var{root} is a list @code{(@var{dir} @var{edges} @var{w1}
2344 @var{w2} ...)} where @var{dir} is @code{nil} for a horizontal split,
2345 and @code{t} for a vertical split, @var{edges} gives the combined size and
2346 position of the subwindows in the split, and the rest of the elements
2347 are the subwindows in the split. Each of the subwindows may again be
2348 a window or a list representing a window split, and so on. The
2349 @var{edges} element is a list @code{(@var{left}@var{ top}@var{ right}@var{ bottom})}
2350 similar to the value returned by @code{window-edges}.
2353 @node Window Configurations
2354 @section Window Configurations
2355 @cindex window configurations
2356 @cindex saving window information
2358 A @dfn{window configuration} records the entire layout of one
2359 frame---all windows, their sizes, which buffers they contain, how those
2360 buffers are scrolled, and their values of point and the mark; also their
2361 fringes, margins, and scroll bar settings. It also includes the value
2362 of @code{minibuffer-scroll-window}. As a special exception, the window
2363 configuration does not record the value of point in the selected window
2364 for the current buffer. Also, the window configuration does not record
2365 the values of window parameters; see @ref{Window Parameters}.
2367 You can bring back an entire frame layout by restoring a previously
2368 saved window configuration. If you want to record the layout of all
2369 frames instead of just one, use a frame configuration instead of a
2370 window configuration; see @ref{Frame Configurations}.
2372 @defun current-window-configuration &optional frame
2373 This function returns a new object representing @var{frame}'s current
2374 window configuration. The default for @var{frame} is the selected
2378 @defun set-window-configuration configuration
2379 This function restores the configuration of windows and buffers as
2380 specified by @var{configuration}, for the frame that @var{configuration}
2383 The argument @var{configuration} must be a value that was previously
2384 returned by @code{current-window-configuration}. The configuration is
2385 restored in the frame from which @var{configuration} was made, whether
2386 that frame is selected or not. This always counts as a window size
2387 change and triggers execution of the @code{window-size-change-functions}
2388 (@pxref{Window Hooks}), because @code{set-window-configuration} doesn't
2389 know how to tell whether the new configuration actually differs from the
2392 If the frame which @var{configuration} was saved from is dead, all this
2393 function does is restore the three variables @code{window-min-height},
2394 @code{window-min-width} and @code{minibuffer-scroll-window}. In this
2395 case, the function returns @code{nil}. Otherwise, it returns @code{t}.
2397 Here is a way of using this function to get the same effect
2398 as @code{save-window-excursion}:
2402 (let ((config (current-window-configuration)))
2404 (progn (split-window-vertically nil)
2406 (set-window-configuration config)))
2411 @defspec save-window-excursion forms@dots{}
2412 This special form records the window configuration, executes @var{forms}
2413 in sequence, then restores the earlier window configuration. The window
2414 configuration includes, for each window, the value of point and the
2415 portion of the buffer that is visible. It also includes the choice of
2416 selected window. However, it does not include the value of point in
2417 the current buffer; use @code{save-excursion} also, if you wish to
2420 Don't use this construct when @code{save-selected-window} is sufficient.
2422 Exit from @code{save-window-excursion} always triggers execution of
2423 @code{window-size-change-functions}. (It doesn't know how to tell
2424 whether the restored configuration actually differs from the one in
2425 effect at the end of the @var{forms}.)
2427 The return value is the value of the final form in @var{forms}.
2433 @result{} #<window 25 on control.texi>
2436 (setq w (selected-window))
2437 @result{} #<window 19 on control.texi>
2440 (save-window-excursion
2441 (delete-other-windows w)
2442 (switch-to-buffer "foo")
2444 @result{} do-something
2445 ;; @r{The screen is now split again.}
2450 @defun window-configuration-p object
2451 This function returns @code{t} if @var{object} is a window configuration.
2454 @defun compare-window-configurations config1 config2
2455 This function compares two window configurations as regards the
2456 structure of windows, but ignores the values of point and mark and the
2457 saved scrolling positions---it can return @code{t} even if those
2460 The function @code{equal} can also compare two window configurations; it
2461 regards configurations as unequal if they differ in any respect, even a
2462 saved point or mark.
2465 @defun window-configuration-frame config
2466 This function returns the frame for which the window configuration
2467 @var{config} was made.
2470 Other primitives to look inside of window configurations would make
2471 sense, but are not implemented because we did not need them. See the
2472 file @file{winner.el} for some more operations on windows
2475 @node Window Parameters
2476 @section Window Parameters
2477 @cindex window parameters
2479 This sections describes how window parameters can be used to associate
2480 additional information with windows.
2482 @defun window-parameter window parameter
2483 This function returns @var{window}'s value for @var{parameter}. The
2484 default for @var{window} is the selected window. If @var{window}
2485 has no setting for @var{parameter}, this function returns @code{nil}.
2488 @defun window-parameters &optional window
2489 This function returns all parameters of @var{window} and their values.
2490 The default for @var{window} is the selected window. The return value
2491 is an association list of elements of the form @code{(@var{parameter}
2495 @defun set-window-parameter window parameter value
2496 This function sets @var{window}'s value of @var{parameter} to
2497 @var{value} and returns @var{value}. The default for @var{window}
2498 is the selected window.
2501 Currently, window parameters are not saved in window configurations and
2502 consequently not restored by @code{set-window-configuration}. Hence,
2503 any change of a parameter introduced via @code{set-window-parameter} can
2504 be undone only by invoking @code{set-window-parameter} for the same
2505 parameter again. Since @code{save-window-excursion} relies on window
2506 configurations (@pxref{Window Configurations}), window parameters are
2507 not saved and restored by that special form, either.
2510 @section Hooks for Window Scrolling and Changes
2511 @cindex hooks for window operations
2513 This section describes how a Lisp program can take action whenever a
2514 window displays a different part of its buffer or a different buffer.
2515 There are three actions that can change this: scrolling the window,
2516 switching buffers in the window, and changing the size of the window.
2517 The first two actions run @code{window-scroll-functions}; the last runs
2518 @code{window-size-change-functions}.
2520 @defvar window-scroll-functions
2521 This variable holds a list of functions that Emacs should call before
2522 redisplaying a window with scrolling. Displaying a different buffer in
2523 the window also runs these functions.
2525 This variable is not a normal hook, because each function is called with
2526 two arguments: the window, and its new display-start position.
2528 These functions must be careful in using @code{window-end}
2529 (@pxref{Window Start and End}); if you need an up-to-date value, you
2530 must use the @var{update} argument to ensure you get it.
2532 @strong{Warning:} don't use this feature to alter the way the window
2533 is scrolled. It's not designed for that, and such use probably won't
2537 @defvar window-size-change-functions
2538 This variable holds a list of functions to be called if the size of any
2539 window changes for any reason. The functions are called just once per
2540 redisplay, and just once for each frame on which size changes have
2543 Each function receives the frame as its sole argument. There is no
2544 direct way to find out which windows on that frame have changed size, or
2545 precisely how. However, if a size-change function records, at each
2546 call, the existing windows and their sizes, it can also compare the
2547 present sizes and the previous sizes.
2549 Creating or deleting windows counts as a size change, and therefore
2550 causes these functions to be called. Changing the frame size also
2551 counts, because it changes the sizes of the existing windows.
2553 It is not a good idea to use @code{save-window-excursion} (@pxref{Window
2554 Configurations}) in these functions, because that always counts as a
2555 size change, and it would cause these functions to be called over and
2556 over. In most cases, @code{save-selected-window} (@pxref{Selecting
2557 Windows}) is what you need here.
2560 @defvar redisplay-end-trigger-functions
2561 This abnormal hook is run whenever redisplay in a window uses text that
2562 extends past a specified end trigger position. You set the end trigger
2563 position with @code{set-window-redisplay-end-trigger}. The functions
2564 are called with two arguments: the window, and the end trigger position.
2565 Storing @code{nil} for the end trigger position turns off the feature,
2566 and the trigger value is automatically reset to @code{nil} just after
2570 @defun set-window-redisplay-end-trigger window position
2571 This function sets @var{window}'s end trigger position at
2575 @defun window-redisplay-end-trigger &optional window
2576 This function returns @var{window}'s current end trigger position.
2577 If @var{window} is @code{nil} or omitted, it uses the selected window.
2580 @defvar window-configuration-change-hook
2581 A normal hook that is run every time you change the window configuration
2582 of an existing frame. This includes splitting or deleting windows,
2583 changing the sizes of windows, or displaying a different buffer in a
2586 The buffer-local part of this hook is run once per each window on the
2587 affected frame, with the relevant window selected and its buffer
2588 current. The global part is run once for the modified frame, with that
2593 arch-tag: 3f6c36e8-df49-4986-b757-417feed88be3