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1 | @c -*-texinfo-*- |
2 | @c This is part of the GNU Emacs Lisp Reference Manual. | |
fd897522 GM |
3 | @c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999 |
4 | @c Free Software Foundation, Inc. | |
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5 | @c See the file elisp.texi for copying conditions. |
6 | @setfilename ../info/windows | |
7 | @node Windows, Frames, Buffers, Top | |
8 | @chapter Windows | |
9 | ||
10 | This chapter describes most of the functions and variables related to | |
11 | Emacs windows. See @ref{Display}, for information on how text is | |
12 | displayed in windows. | |
13 | ||
14 | @menu | |
3c29caa8 DH |
15 | * Basic Windows:: Basic information on using windows. |
16 | * Splitting Windows:: Splitting one window into two windows. | |
17 | * Deleting Windows:: Deleting a window gives its space to other windows. | |
18 | * Selecting Windows:: The selected window is the one that you edit in. | |
19 | * Cyclic Window Ordering:: Moving around the existing windows. | |
20 | * Buffers and Windows:: Each window displays the contents of a buffer. | |
21 | * Displaying Buffers:: Higher-lever functions for displaying a buffer | |
22 | and choosing a window for it. | |
23 | * Choosing Window:: How to choose a window for displaying a buffer. | |
24 | * Window Point:: Each window has its own location of point. | |
25 | * Window Start:: The display-start position controls which text | |
26 | is on-screen in the window. | |
8241495d RS |
27 | * Textual Scrolling:: Moving text up and down through the window. |
28 | * Vertical Scrolling:: Moving the contents up and down on the window. | |
29 | * Horizontal Scrolling:: Moving the contents sideways on the window. | |
3c29caa8 DH |
30 | * Size of Window:: Accessing the size of a window. |
31 | * Resizing Windows:: Changing the size of a window. | |
32 | * Coordinates and Windows:: Converting coordinates to windows. | |
33 | * Window Configurations:: Saving and restoring the state of the screen. | |
f9f59935 RS |
34 | * Window Hooks:: Hooks for scrolling, window size changes, |
35 | redisplay going past a certain point, | |
36 | or window configuration changes. | |
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37 | @end menu |
38 | ||
39 | @node Basic Windows | |
40 | @section Basic Concepts of Emacs Windows | |
41 | @cindex window | |
42 | @cindex selected window | |
43 | ||
bfe721d1 KH |
44 | A @dfn{window} in Emacs is the physical area of the screen in which a |
45 | buffer is displayed. The term is also used to refer to a Lisp object that | |
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46 | represents that screen area in Emacs Lisp. It should be |
47 | clear from the context which is meant. | |
48 | ||
bfe721d1 KH |
49 | Emacs groups windows into frames. A frame represents an area of |
50 | screen available for Emacs to use. Each frame always contains at least | |
51 | one window, but you can subdivide it vertically or horizontally into | |
52 | multiple nonoverlapping Emacs windows. | |
53 | ||
54 | In each frame, at any time, one and only one window is designated as | |
55 | @dfn{selected within the frame}. The frame's cursor appears in that | |
f9f59935 | 56 | window. At any time, one frame is the selected frame; and the window |
bfe721d1 KH |
57 | selected within that frame is @dfn{the selected window}. The selected |
58 | window's buffer is usually the current buffer (except when | |
59 | @code{set-buffer} has been used). @xref{Current Buffer}. | |
60 | ||
61 | For practical purposes, a window exists only while it is displayed in | |
62 | a frame. Once removed from the frame, the window is effectively deleted | |
63 | and should not be used, @emph{even though there may still be references | |
64 | to it} from other Lisp objects. Restoring a saved window configuration | |
65 | is the only way for a window no longer on the screen to come back to | |
66 | life. (@xref{Deleting Windows}.) | |
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67 | |
68 | Each window has the following attributes: | |
69 | ||
70 | @itemize @bullet | |
71 | @item | |
72 | containing frame | |
73 | ||
3c29caa8 | 74 | @item |
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75 | window height |
76 | ||
3c29caa8 | 77 | @item |
b1b12a8e RS |
78 | window width |
79 | ||
3c29caa8 | 80 | @item |
b1b12a8e RS |
81 | window edges with respect to the screen or frame |
82 | ||
3c29caa8 | 83 | @item |
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84 | the buffer it displays |
85 | ||
3c29caa8 | 86 | @item |
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87 | position within the buffer at the upper left of the window |
88 | ||
3c29caa8 | 89 | @item |
c638661f | 90 | amount of horizontal scrolling, in columns |
b1b12a8e | 91 | |
3c29caa8 | 92 | @item |
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93 | point |
94 | ||
3c29caa8 | 95 | @item |
b1b12a8e RS |
96 | the mark |
97 | ||
3c29caa8 | 98 | @item |
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99 | how recently the window was selected |
100 | @end itemize | |
101 | ||
102 | @cindex multiple windows | |
103 | Users create multiple windows so they can look at several buffers at | |
104 | once. Lisp libraries use multiple windows for a variety of reasons, but | |
bfe721d1 KH |
105 | most often to display related information. In Rmail, for example, you |
106 | can move through a summary buffer in one window while the other window | |
107 | shows messages one at a time as they are reached. | |
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108 | |
109 | The meaning of ``window'' in Emacs is similar to what it means in the | |
c638661f | 110 | context of general-purpose window systems such as X, but not identical. |
bfe721d1 KH |
111 | The X Window System places X windows on the screen; Emacs uses one or |
112 | more X windows as frames, and subdivides them into | |
113 | Emacs windows. When you use Emacs on a character-only terminal, Emacs | |
114 | treats the whole terminal screen as one frame. | |
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115 | |
116 | @cindex terminal screen | |
117 | @cindex screen of terminal | |
118 | @cindex tiled windows | |
119 | Most window systems support arbitrarily located overlapping windows. | |
120 | In contrast, Emacs windows are @dfn{tiled}; they never overlap, and | |
f9f59935 RS |
121 | together they fill the whole screen or frame. Because of the way in |
122 | which Emacs creates new windows and resizes them, not all conceivable | |
123 | tilings of windows on an Emacs frame are actually possible. | |
124 | @xref{Splitting Windows}, and @ref{Size of Window}. | |
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125 | |
126 | @xref{Display}, for information on how the contents of the | |
127 | window's buffer are displayed in the window. | |
128 | ||
129 | @defun windowp object | |
f9f59935 | 130 | This function returns @code{t} if @var{object} is a window. |
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131 | @end defun |
132 | ||
133 | @node Splitting Windows | |
134 | @section Splitting Windows | |
135 | @cindex splitting windows | |
136 | @cindex window splitting | |
137 | ||
138 | The functions described here are the primitives used to split a window | |
139 | into two windows. Two higher level functions sometimes split a window, | |
140 | but not always: @code{pop-to-buffer} and @code{display-buffer} | |
141 | (@pxref{Displaying Buffers}). | |
142 | ||
143 | The functions described here do not accept a buffer as an argument. | |
144 | The two ``halves'' of the split window initially display the same buffer | |
145 | previously visible in the window that was split. | |
146 | ||
147 | @deffn Command split-window &optional window size horizontal | |
148 | This function splits @var{window} into two windows. The original | |
149 | window @var{window} remains the selected window, but occupies only | |
150 | part of its former screen area. The rest is occupied by a newly created | |
151 | window which is returned as the value of this function. | |
152 | ||
2726b68b | 153 | If @var{horizontal} is non-@code{nil}, then @var{window} splits into |
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154 | two side by side windows. The original window @var{window} keeps the |
155 | leftmost @var{size} columns, and gives the rest of the columns to the | |
156 | new window. Otherwise, it splits into windows one above the other, and | |
157 | @var{window} keeps the upper @var{size} lines and gives the rest of the | |
158 | lines to the new window. The original window is therefore the | |
c638661f | 159 | left-hand or upper of the two, and the new window is the right-hand or |
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160 | lower. |
161 | ||
2726b68b | 162 | If @var{window} is omitted or @code{nil}, then the selected window is |
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163 | split. If @var{size} is omitted or @code{nil}, then @var{window} is |
164 | divided evenly into two parts. (If there is an odd line, it is | |
165 | allocated to the new window.) When @code{split-window} is called | |
166 | interactively, all its arguments are @code{nil}. | |
167 | ||
2726b68b RS |
168 | If splitting would result in making a window that is smaller than |
169 | @code{window-min-height} or @code{window-min-width}, the function | |
170 | signals an error and does not split the window at all. | |
171 | ||
172 | The following example starts with one window on a screen that is 50 | |
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173 | lines high by 80 columns wide; then the window is split. |
174 | ||
175 | @smallexample | |
176 | @group | |
177 | (setq w (selected-window)) | |
178 | @result{} #<window 8 on windows.texi> | |
179 | (window-edges) ; @r{Edges in order:} | |
180 | @result{} (0 0 80 50) ; @r{left--top--right--bottom} | |
181 | @end group | |
182 | ||
183 | @group | |
184 | ;; @r{Returns window created} | |
3c29caa8 | 185 | (setq w2 (split-window w 15)) |
b1b12a8e RS |
186 | @result{} #<window 28 on windows.texi> |
187 | @end group | |
188 | @group | |
189 | (window-edges w2) | |
190 | @result{} (0 15 80 50) ; @r{Bottom window;} | |
191 | ; @r{top is line 15} | |
192 | @end group | |
193 | @group | |
194 | (window-edges w) | |
195 | @result{} (0 0 80 15) ; @r{Top window} | |
196 | @end group | |
197 | @end smallexample | |
198 | ||
199 | The screen looks like this: | |
200 | ||
201 | @smallexample | |
202 | @group | |
3c29caa8 DH |
203 | __________ |
204 | | | line 0 | |
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205 | | w | |
206 | |__________| | |
207 | | | line 15 | |
208 | | w2 | | |
209 | |__________| | |
210 | line 50 | |
211 | column 0 column 80 | |
212 | @end group | |
213 | @end smallexample | |
214 | ||
215 | Next, the top window is split horizontally: | |
216 | ||
217 | @smallexample | |
218 | @group | |
219 | (setq w3 (split-window w 35 t)) | |
220 | @result{} #<window 32 on windows.texi> | |
221 | @end group | |
222 | @group | |
223 | (window-edges w3) | |
224 | @result{} (35 0 80 15) ; @r{Left edge at column 35} | |
225 | @end group | |
226 | @group | |
227 | (window-edges w) | |
228 | @result{} (0 0 35 15) ; @r{Right edge at column 35} | |
229 | @end group | |
230 | @group | |
231 | (window-edges w2) | |
232 | @result{} (0 15 80 50) ; @r{Bottom window unchanged} | |
233 | @end group | |
234 | @end smallexample | |
235 | ||
bda144f4 | 236 | @need 3000 |
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237 | Now, the screen looks like this: |
238 | ||
239 | @smallexample | |
240 | @group | |
241 | column 35 | |
3c29caa8 DH |
242 | __________ |
243 | | | | line 0 | |
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244 | | w | w3 | |
245 | |___|______| | |
246 | | | line 15 | |
247 | | w2 | | |
248 | |__________| | |
249 | line 50 | |
250 | column 0 column 80 | |
251 | @end group | |
252 | @end smallexample | |
aeb2c306 JB |
253 | |
254 | Normally, Emacs indicates the border between two side-by-side windows | |
969fe9b5 | 255 | with a scroll bar (@pxref{Window Frame Parameters,Scroll Bars}) or @samp{|} |
aeb2c306 JB |
256 | characters. The display table can specify alternative border |
257 | characters; see @ref{Display Tables}. | |
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258 | @end deffn |
259 | ||
8241495d | 260 | @deffn Command split-window-vertically &optional size |
1911e6e5 | 261 | This function splits the selected window into two windows, one above the |
ebc6903b | 262 | other, leaving the upper of the two windows selected, with @var{size} |
1911e6e5 RS |
263 | lines. (If @var{size} is negative, then the lower of the two windows |
264 | gets @minus{} @var{size} lines and the upper window gets the rest, but | |
265 | the upper window is still the one selected.) | |
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266 | @end deffn |
267 | ||
2468d0c0 | 268 | @deffn Command split-window-horizontally &optional size |
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269 | This function splits the selected window into two windows |
270 | side-by-side, leaving the selected window with @var{size} columns. | |
271 | ||
8241495d RS |
272 | This function is basically an interface to @code{split-window}. |
273 | You could define a simplified version of the function like this: | |
b1b12a8e RS |
274 | |
275 | @smallexample | |
276 | @group | |
277 | (defun split-window-horizontally (&optional arg) | |
278 | "Split selected window into two windows, side by side..." | |
279 | (interactive "P") | |
513331d3 | 280 | @end group |
8241495d RS |
281 | @group |
282 | (let ((size (and arg (prefix-numeric-value arg)))) | |
283 | (and size (< size 0) | |
284 | (setq size (+ (window-width) size))) | |
285 | (split-window nil size t))) | |
b1b12a8e RS |
286 | @end group |
287 | @end smallexample | |
288 | @end deffn | |
289 | ||
290 | @defun one-window-p &optional no-mini all-frames | |
291 | This function returns non-@code{nil} if there is only one window. The | |
292 | argument @var{no-mini}, if non-@code{nil}, means don't count the | |
293 | minibuffer even if it is active; otherwise, the minibuffer window is | |
eaac2be1 | 294 | included, if active, in the total number of windows, which is compared |
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295 | against one. |
296 | ||
297 | The argument @var{all-frames} specifies which frames to consider. Here | |
298 | are the possible values and their meanings: | |
299 | ||
300 | @table @asis | |
301 | @item @code{nil} | |
302 | Count the windows in the selected frame, plus the minibuffer used | |
303 | by that frame even if it lies in some other frame. | |
304 | ||
305 | @item @code{t} | |
306 | Count all windows in all existing frames. | |
307 | ||
308 | @item @code{visible} | |
309 | Count all windows in all visible frames. | |
310 | ||
bfe721d1 KH |
311 | @item 0 |
312 | Count all windows in all visible or iconified frames. | |
313 | ||
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314 | @item anything else |
315 | Count precisely the windows in the selected frame, and no others. | |
316 | @end table | |
317 | @end defun | |
318 | ||
319 | @node Deleting Windows | |
320 | @section Deleting Windows | |
321 | @cindex deleting windows | |
322 | ||
323 | A window remains visible on its frame unless you @dfn{delete} it by | |
324 | calling certain functions that delete windows. A deleted window cannot | |
325 | appear on the screen, but continues to exist as a Lisp object until | |
326 | there are no references to it. There is no way to cancel the deletion | |
327 | of a window aside from restoring a saved window configuration | |
328 | (@pxref{Window Configurations}). Restoring a window configuration also | |
329 | deletes any windows that aren't part of that configuration. | |
330 | ||
331 | When you delete a window, the space it took up is given to one | |
969fe9b5 | 332 | adjacent sibling. |
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333 | |
334 | @c Emacs 19 feature | |
335 | @defun window-live-p window | |
336 | This function returns @code{nil} if @var{window} is deleted, and | |
337 | @code{t} otherwise. | |
338 | ||
b22f3a19 | 339 | @strong{Warning:} Erroneous information or fatal errors may result from |
b1b12a8e RS |
340 | using a deleted window as if it were live. |
341 | @end defun | |
342 | ||
343 | @deffn Command delete-window &optional window | |
969fe9b5 RS |
344 | This function removes @var{window} from display, and returns @code{nil}. |
345 | If @var{window} is omitted, then the selected window is deleted. An | |
346 | error is signaled if there is only one window when @code{delete-window} | |
347 | is called. | |
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348 | @end deffn |
349 | ||
350 | @deffn Command delete-other-windows &optional window | |
351 | This function makes @var{window} the only window on its frame, by | |
352 | deleting the other windows in that frame. If @var{window} is omitted or | |
353 | @code{nil}, then the selected window is used by default. | |
354 | ||
969fe9b5 | 355 | The return value is @code{nil}. |
b1b12a8e RS |
356 | @end deffn |
357 | ||
358 | @deffn Command delete-windows-on buffer &optional frame | |
359 | This function deletes all windows showing @var{buffer}. If there are | |
360 | no windows showing @var{buffer}, it does nothing. | |
361 | ||
362 | @code{delete-windows-on} operates frame by frame. If a frame has | |
363 | several windows showing different buffers, then those showing | |
364 | @var{buffer} are removed, and the others expand to fill the space. If | |
365 | all windows in some frame are showing @var{buffer} (including the case | |
366 | where there is only one window), then the frame reverts to having a | |
367 | single window showing another buffer chosen with @code{other-buffer}. | |
368 | @xref{The Buffer List}. | |
369 | ||
1911e6e5 RS |
370 | The argument @var{frame} controls which frames to operate on. This |
371 | function does not use it in quite the same way as the other functions | |
372 | which scan all windows; specifically, the values @code{t} and @code{nil} | |
373 | have the opposite of their meanings in other functions. Here are the | |
374 | full details: | |
b1b12a8e RS |
375 | |
376 | @itemize @bullet | |
377 | @item | |
1911e6e5 | 378 | If it is @code{nil}, operate on all frames. |
b1b12a8e | 379 | @item |
1911e6e5 | 380 | If it is @code{t}, operate on the selected frame. |
b1b12a8e RS |
381 | @item |
382 | If it is @code{visible}, operate on all visible frames. | |
1911e6e5 | 383 | @item |
bfe721d1 | 384 | If it is 0, operate on all visible or iconified frames. |
b1b12a8e RS |
385 | @item |
386 | If it is a frame, operate on that frame. | |
387 | @end itemize | |
388 | ||
389 | This function always returns @code{nil}. | |
390 | @end deffn | |
391 | ||
392 | @node Selecting Windows | |
393 | @section Selecting Windows | |
394 | @cindex selecting windows | |
395 | ||
396 | When a window is selected, the buffer in the window becomes the current | |
397 | buffer, and the cursor will appear in it. | |
398 | ||
399 | @defun selected-window | |
400 | This function returns the selected window. This is the window in | |
401 | which the cursor appears and to which many commands apply. | |
402 | @end defun | |
403 | ||
404 | @defun select-window window | |
405 | This function makes @var{window} the selected window. The cursor then | |
406 | appears in @var{window} (on redisplay). The buffer being displayed in | |
407 | @var{window} is immediately designated the current buffer. | |
408 | ||
409 | The return value is @var{window}. | |
410 | ||
411 | @example | |
412 | @group | |
413 | (setq w (next-window)) | |
414 | (select-window w) | |
415 | @result{} #<window 65 on windows.texi> | |
416 | @end group | |
417 | @end example | |
418 | @end defun | |
419 | ||
bfe721d1 KH |
420 | @defmac save-selected-window forms@dots{} |
421 | This macro records the selected window, executes @var{forms} | |
422 | in sequence, then restores the earlier selected window. | |
3c29caa8 DH |
423 | |
424 | This macro does not save or restore anything about the sizes, arrangement | |
bfe721d1 | 425 | or contents of windows; therefore, if the @var{forms} change them, |
3c29caa8 DH |
426 | the change persists. |
427 | ||
428 | Each frame, at any time, has a window selected within the frame. This | |
969fe9b5 | 429 | macro saves only @emph{the} selected window; it does not save anything |
3c29caa8 DH |
430 | about other frames. If the @var{forms} select some other frame and |
431 | alter the window selected within it, the change persists. | |
bfe721d1 KH |
432 | @end defmac |
433 | ||
b1b12a8e RS |
434 | @cindex finding windows |
435 | The following functions choose one of the windows on the screen, | |
436 | offering various criteria for the choice. | |
437 | ||
438 | @defun get-lru-window &optional frame | |
439 | This function returns the window least recently ``used'' (that is, | |
440 | selected). The selected window is always the most recently used window. | |
441 | ||
442 | The selected window can be the least recently used window if it is the | |
443 | only window. A newly created window becomes the least recently used | |
444 | window until it is selected. A minibuffer window is never a candidate. | |
445 | ||
c638661f | 446 | The argument @var{frame} controls which windows are considered. |
b1b12a8e RS |
447 | |
448 | @itemize @bullet | |
449 | @item | |
450 | If it is @code{nil}, consider windows on the selected frame. | |
451 | @item | |
452 | If it is @code{t}, consider windows on all frames. | |
453 | @item | |
454 | If it is @code{visible}, consider windows on all visible frames. | |
455 | @item | |
bfe721d1 KH |
456 | If it is 0, consider windows on all visible or iconified frames. |
457 | @item | |
b1b12a8e RS |
458 | If it is a frame, consider windows on that frame. |
459 | @end itemize | |
460 | @end defun | |
461 | ||
462 | @defun get-largest-window &optional frame | |
463 | This function returns the window with the largest area (height times | |
464 | width). If there are no side-by-side windows, then this is the window | |
465 | with the most lines. A minibuffer window is never a candidate. | |
466 | ||
467 | If there are two windows of the same size, then the function returns | |
c638661f | 468 | the window that is first in the cyclic ordering of windows (see |
b1b12a8e RS |
469 | following section), starting from the selected window. |
470 | ||
1911e6e5 RS |
471 | The argument @var{frame} controls which set of windows to |
472 | consider. See @code{get-lru-window}, above. | |
b1b12a8e RS |
473 | @end defun |
474 | ||
1e8ca3a9 EZ |
475 | @cindex window that satisfies a predicate |
476 | @cindex conditional selection of windows | |
477 | @defun get-window-with-predicate predicate &optional minibuf all-frames default | |
478 | This function returns a window satisfying @var{predicate}. It cycles | |
479 | through all visible windows using @code{walk-windows} (@pxref{Cyclic | |
480 | Window Ordering}), calling @var{predicate} on each one one of them | |
481 | with that window as its argument. The function returns the first | |
482 | window for which @var{predicate} returns a non-@code{nil} value; if | |
483 | that never happens, it returns @var{default}. | |
484 | ||
485 | The optional arguments @var{minibuf} and @var{all-frames} specify the | |
486 | set of windows to include in the scan. See the description of | |
487 | @code{next-window} in @ref{Cyclic Window Ordering}, for details. | |
488 | @end defun | |
489 | ||
b1b12a8e RS |
490 | @node Cyclic Window Ordering |
491 | @comment node-name, next, previous, up | |
492 | @section Cyclic Ordering of Windows | |
493 | @cindex cyclic ordering of windows | |
494 | @cindex ordering of windows, cyclic | |
3c29caa8 | 495 | @cindex window ordering, cyclic |
b1b12a8e RS |
496 | |
497 | When you use the command @kbd{C-x o} (@code{other-window}) to select | |
498 | the next window, it moves through all the windows on the screen in a | |
499 | specific cyclic order. For any given configuration of windows, this | |
500 | order never varies. It is called the @dfn{cyclic ordering of windows}. | |
501 | ||
502 | This ordering generally goes from top to bottom, and from left to | |
503 | right. But it may go down first or go right first, depending on the | |
504 | order in which the windows were split. | |
505 | ||
506 | If the first split was vertical (into windows one above each other), | |
507 | and then the subwindows were split horizontally, then the ordering is | |
508 | left to right in the top of the frame, and then left to right in the | |
509 | next lower part of the frame, and so on. If the first split was | |
510 | horizontal, the ordering is top to bottom in the left part, and so on. | |
511 | In general, within each set of siblings at any level in the window tree, | |
512 | the order is left to right, or top to bottom. | |
513 | ||
514 | @defun next-window &optional window minibuf all-frames | |
515 | @cindex minibuffer window | |
516 | This function returns the window following @var{window} in the cyclic | |
c638661f RS |
517 | ordering of windows. This is the window that @kbd{C-x o} would select |
518 | if typed when @var{window} is selected. If @var{window} is the only | |
b1b12a8e RS |
519 | window visible, then this function returns @var{window}. If omitted, |
520 | @var{window} defaults to the selected window. | |
521 | ||
522 | The value of the argument @var{minibuf} determines whether the | |
523 | minibuffer is included in the window order. Normally, when | |
524 | @var{minibuf} is @code{nil}, the minibuffer is included if it is | |
525 | currently active; this is the behavior of @kbd{C-x o}. (The minibuffer | |
526 | window is active while the minibuffer is in use. @xref{Minibuffers}.) | |
527 | ||
528 | If @var{minibuf} is @code{t}, then the cyclic ordering includes the | |
529 | minibuffer window even if it is not active. | |
530 | ||
531 | If @var{minibuf} is neither @code{t} nor @code{nil}, then the minibuffer | |
532 | window is not included even if it is active. | |
533 | ||
534 | The argument @var{all-frames} specifies which frames to consider. Here | |
535 | are the possible values and their meanings: | |
536 | ||
537 | @table @asis | |
538 | @item @code{nil} | |
539 | Consider all the windows in @var{window}'s frame, plus the minibuffer | |
540 | used by that frame even if it lies in some other frame. | |
541 | ||
542 | @item @code{t} | |
543 | Consider all windows in all existing frames. | |
544 | ||
545 | @item @code{visible} | |
546 | Consider all windows in all visible frames. (To get useful results, you | |
547 | must ensure @var{window} is in a visible frame.) | |
548 | ||
83abd543 | 549 | @item 0 |
bfe721d1 KH |
550 | Consider all windows in all visible or iconified frames. |
551 | ||
b1b12a8e RS |
552 | @item anything else |
553 | Consider precisely the windows in @var{window}'s frame, and no others. | |
554 | @end table | |
555 | ||
3c29caa8 | 556 | This example assumes there are two windows, both displaying the |
b1b12a8e RS |
557 | buffer @samp{windows.texi}: |
558 | ||
559 | @example | |
560 | @group | |
561 | (selected-window) | |
562 | @result{} #<window 56 on windows.texi> | |
563 | @end group | |
564 | @group | |
565 | (next-window (selected-window)) | |
566 | @result{} #<window 52 on windows.texi> | |
567 | @end group | |
568 | @group | |
569 | (next-window (next-window (selected-window))) | |
570 | @result{} #<window 56 on windows.texi> | |
571 | @end group | |
572 | @end example | |
573 | @end defun | |
574 | ||
575 | @defun previous-window &optional window minibuf all-frames | |
576 | This function returns the window preceding @var{window} in the cyclic | |
577 | ordering of windows. The other arguments specify which windows to | |
578 | include in the cycle, as in @code{next-window}. | |
579 | @end defun | |
580 | ||
8241495d | 581 | @deffn Command other-window count &optional all-frames |
b1b12a8e | 582 | This function selects the @var{count}th following window in the cyclic |
969fe9b5 RS |
583 | order. If count is negative, then it moves back @minus{}@var{count} |
584 | windows in the cycle, rather than forward. It returns @code{nil}. | |
b1b12a8e | 585 | |
75708135 | 586 | The argument @var{all-frames} has the same meaning as in |
8241495d RS |
587 | @code{next-window}, but the @var{minibuf} argument of @code{next-window} |
588 | is always effectively @code{nil}. | |
589 | ||
b1b12a8e RS |
590 | In an interactive call, @var{count} is the numeric prefix argument. |
591 | @end deffn | |
592 | ||
593 | @c Emacs 19 feature | |
594 | @defun walk-windows proc &optional minibuf all-frames | |
595 | This function cycles through all windows, calling @code{proc} | |
596 | once for each window with the window as its sole argument. | |
597 | ||
598 | The optional arguments @var{minibuf} and @var{all-frames} specify the | |
599 | set of windows to include in the scan. See @code{next-window}, above, | |
600 | for details. | |
601 | @end defun | |
602 | ||
e258eedc GM |
603 | @defun window-list &optional frame minibuf window |
604 | This function returns a list of the windows on @var{frame}, starting | |
605 | with @var{window}. If @var{frame} is @code{nil} or omitted, the | |
606 | selected frame is used instead; if @var{window} is @code{nil} or | |
607 | omitted, the selected window is used instead. | |
608 | ||
609 | The value of @var{minibuf} determines if the minibuffer window will be | |
610 | included in the result list. If @var{minibuf} is @code{t}, the | |
611 | minibuffer window will be included, even if it isn't active. If | |
429994d8 | 612 | @var{minibuf} is @code{nil} or omitted, the minibuffer window will |
e258eedc GM |
613 | only be included in the list if it is active. If @var{minibuf} is |
614 | neither @code{nil} nor @code{t}, the minibuffer window is not | |
615 | included, whether or not it is active. | |
429994d8 | 616 | @end defun |
e258eedc | 617 | |
b1b12a8e RS |
618 | @node Buffers and Windows |
619 | @section Buffers and Windows | |
620 | @cindex examining windows | |
621 | @cindex windows, controlling precisely | |
622 | @cindex buffers, controlled in windows | |
623 | ||
624 | This section describes low-level functions to examine windows or to | |
625 | display buffers in windows in a precisely controlled fashion. | |
626 | @iftex | |
627 | See the following section for | |
628 | @end iftex | |
37680279 | 629 | @ifnottex |
b1b12a8e | 630 | @xref{Displaying Buffers}, for |
37680279 | 631 | @end ifnottex |
b1b12a8e RS |
632 | related functions that find a window to use and specify a buffer for it. |
633 | The functions described there are easier to use than these, but they | |
634 | employ heuristics in choosing or creating a window; use these functions | |
635 | when you need complete control. | |
636 | ||
637 | @defun set-window-buffer window buffer-or-name | |
638 | This function makes @var{window} display @var{buffer-or-name} as its | |
a9f0a989 RS |
639 | contents. It returns @code{nil}. This is the fundamental primitive |
640 | for changing which buffer is displayed in a window, and all ways | |
641 | of doing that call this function. | |
b1b12a8e RS |
642 | |
643 | @example | |
644 | @group | |
645 | (set-window-buffer (selected-window) "foo") | |
646 | @result{} nil | |
647 | @end group | |
648 | @end example | |
649 | @end defun | |
650 | ||
651 | @defun window-buffer &optional window | |
652 | This function returns the buffer that @var{window} is displaying. If | |
653 | @var{window} is omitted, this function returns the buffer for the | |
654 | selected window. | |
655 | ||
656 | @example | |
657 | @group | |
658 | (window-buffer) | |
659 | @result{} #<buffer windows.texi> | |
660 | @end group | |
661 | @end example | |
662 | @end defun | |
663 | ||
664 | @defun get-buffer-window buffer-or-name &optional all-frames | |
665 | This function returns a window currently displaying | |
666 | @var{buffer-or-name}, or @code{nil} if there is none. If there are | |
667 | several such windows, then the function returns the first one in the | |
668 | cyclic ordering of windows, starting from the selected window. | |
669 | @xref{Cyclic Window Ordering}. | |
670 | ||
671 | The argument @var{all-frames} controls which windows to consider. | |
672 | ||
673 | @itemize @bullet | |
674 | @item | |
675 | If it is @code{nil}, consider windows on the selected frame. | |
676 | @item | |
677 | If it is @code{t}, consider windows on all frames. | |
678 | @item | |
679 | If it is @code{visible}, consider windows on all visible frames. | |
680 | @item | |
bfe721d1 KH |
681 | If it is 0, consider windows on all visible or iconified frames. |
682 | @item | |
b1b12a8e RS |
683 | If it is a frame, consider windows on that frame. |
684 | @end itemize | |
685 | @end defun | |
686 | ||
3c29caa8 DH |
687 | @defun get-buffer-window-list buffer-or-name &optional minibuf all-frames |
688 | This function returns a list of all the windows currently displaying | |
689 | @var{buffer-or-name}. | |
690 | ||
691 | The two optional arguments work like the optional arguments of | |
692 | @code{next-window} (@pxref{Cyclic Window Ordering}); they are @emph{not} | |
693 | like the single optional argument of @code{get-buffer-window}. Perhaps | |
694 | we should change @code{get-buffer-window} in the future to make it | |
695 | compatible with the other functions. | |
696 | ||
697 | The argument @var{all-frames} controls which windows to consider. | |
698 | ||
699 | @itemize @bullet | |
700 | @item | |
701 | If it is @code{nil}, consider windows on the selected frame. | |
702 | @item | |
703 | If it is @code{t}, consider windows on all frames. | |
704 | @item | |
705 | If it is @code{visible}, consider windows on all visible frames. | |
706 | @item | |
707 | If it is 0, consider windows on all visible or iconified frames. | |
708 | @item | |
709 | If it is a frame, consider windows on that frame. | |
710 | @end itemize | |
711 | @end defun | |
712 | ||
a9f0a989 | 713 | @defvar buffer-display-time |
a9f0a989 RS |
714 | This variable records the time at which a buffer was last made visible |
715 | in a window. It is always local in each buffer; each time | |
716 | @code{set-window-buffer} is called, it sets this variable to | |
717 | @code{(current-time)} in the specified buffer (@pxref{Time of Day}). | |
1911e6e5 | 718 | When a buffer is first created, @code{buffer-display-time} starts out |
a9f0a989 RS |
719 | with the value @code{nil}. |
720 | @end defvar | |
721 | ||
b1b12a8e RS |
722 | @node Displaying Buffers |
723 | @section Displaying Buffers in Windows | |
724 | @cindex switching to a buffer | |
725 | @cindex displaying a buffer | |
726 | ||
727 | In this section we describe convenient functions that choose a window | |
728 | automatically and use it to display a specified buffer. These functions | |
729 | can also split an existing window in certain circumstances. We also | |
730 | describe variables that parameterize the heuristics used for choosing a | |
731 | window. | |
732 | @iftex | |
733 | See the preceding section for | |
734 | @end iftex | |
37680279 | 735 | @ifnottex |
b1b12a8e | 736 | @xref{Buffers and Windows}, for |
37680279 | 737 | @end ifnottex |
a9f0a989 RS |
738 | low-level functions that give you more precise control. All of these |
739 | functions work by calling @code{set-window-buffer}. | |
b1b12a8e RS |
740 | |
741 | Do not use the functions in this section in order to make a buffer | |
742 | current so that a Lisp program can access or modify it; they are too | |
743 | drastic for that purpose, since they change the display of buffers in | |
969fe9b5 | 744 | windows, which would be gratuitous and surprise the user. Instead, use |
1911e6e5 RS |
745 | @code{set-buffer} and @code{save-current-buffer} (@pxref{Current |
746 | Buffer}), which designate buffers as current for programmed access | |
747 | without affecting the display of buffers in windows. | |
b1b12a8e RS |
748 | |
749 | @deffn Command switch-to-buffer buffer-or-name &optional norecord | |
750 | This function makes @var{buffer-or-name} the current buffer, and also | |
751 | displays the buffer in the selected window. This means that a human can | |
752 | see the buffer and subsequent keyboard commands will apply to it. | |
753 | Contrast this with @code{set-buffer}, which makes @var{buffer-or-name} | |
754 | the current buffer but does not display it in the selected window. | |
755 | @xref{Current Buffer}. | |
756 | ||
22697dac KH |
757 | If @var{buffer-or-name} does not identify an existing buffer, then a new |
758 | buffer by that name is created. The major mode for the new buffer is | |
759 | set according to the variable @code{default-major-mode}. @xref{Auto | |
760 | Major Mode}. | |
b1b12a8e | 761 | |
969fe9b5 RS |
762 | Normally the specified buffer is put at the front of the buffer list |
763 | (both the selected frame's buffer list and the frame-independent buffer | |
764 | list). This affects the operation of @code{other-buffer}. However, if | |
b1b12a8e RS |
765 | @var{norecord} is non-@code{nil}, this is not done. @xref{The Buffer |
766 | List}. | |
767 | ||
768 | The @code{switch-to-buffer} function is often used interactively, as | |
769 | the binding of @kbd{C-x b}. It is also used frequently in programs. It | |
770 | always returns @code{nil}. | |
771 | @end deffn | |
772 | ||
f9f59935 | 773 | @deffn Command switch-to-buffer-other-window buffer-or-name &optional norecord |
b1b12a8e RS |
774 | This function makes @var{buffer-or-name} the current buffer and |
775 | displays it in a window not currently selected. It then selects that | |
776 | window. The handling of the buffer is the same as in | |
777 | @code{switch-to-buffer}. | |
778 | ||
c638661f RS |
779 | The currently selected window is absolutely never used to do the job. |
780 | If it is the only window, then it is split to make a distinct window for | |
781 | this purpose. If the selected window is already displaying the buffer, | |
782 | then it continues to do so, but another window is nonetheless found to | |
783 | display it in as well. | |
f9f59935 RS |
784 | |
785 | This function updates the buffer list just like @code{switch-to-buffer} | |
786 | unless @var{norecord} is non-@code{nil}. | |
b1b12a8e RS |
787 | @end deffn |
788 | ||
f9f59935 | 789 | @defun pop-to-buffer buffer-or-name &optional other-window norecord |
b1b12a8e RS |
790 | This function makes @var{buffer-or-name} the current buffer and |
791 | switches to it in some window, preferably not the window previously | |
792 | selected. The ``popped-to'' window becomes the selected window within | |
793 | its frame. | |
794 | ||
795 | If the variable @code{pop-up-frames} is non-@code{nil}, | |
796 | @code{pop-to-buffer} looks for a window in any visible frame already | |
797 | displaying the buffer; if there is one, it returns that window and makes | |
798 | it be selected within its frame. If there is none, it creates a new | |
799 | frame and displays the buffer in it. | |
800 | ||
801 | If @code{pop-up-frames} is @code{nil}, then @code{pop-to-buffer} | |
802 | operates entirely within the selected frame. (If the selected frame has | |
803 | just a minibuffer, @code{pop-to-buffer} operates within the most | |
804 | recently selected frame that was not just a minibuffer.) | |
805 | ||
806 | If the variable @code{pop-up-windows} is non-@code{nil}, windows may | |
807 | be split to create a new window that is different from the original | |
808 | window. For details, see @ref{Choosing Window}. | |
809 | ||
810 | If @var{other-window} is non-@code{nil}, @code{pop-to-buffer} finds or | |
811 | creates another window even if @var{buffer-or-name} is already visible | |
812 | in the selected window. Thus @var{buffer-or-name} could end up | |
813 | displayed in two windows. On the other hand, if @var{buffer-or-name} is | |
814 | already displayed in the selected window and @var{other-window} is | |
815 | @code{nil}, then the selected window is considered sufficient display | |
816 | for @var{buffer-or-name}, so that nothing needs to be done. | |
817 | ||
bfe721d1 KH |
818 | All the variables that affect @code{display-buffer} affect |
819 | @code{pop-to-buffer} as well. @xref{Choosing Window}. | |
820 | ||
b1b12a8e | 821 | If @var{buffer-or-name} is a string that does not name an existing |
22697dac KH |
822 | buffer, a buffer by that name is created. The major mode for the new |
823 | buffer is set according to the variable @code{default-major-mode}. | |
824 | @xref{Auto Major Mode}. | |
f9f59935 RS |
825 | |
826 | This function updates the buffer list just like @code{switch-to-buffer} | |
827 | unless @var{norecord} is non-@code{nil}. | |
b1b12a8e RS |
828 | @end defun |
829 | ||
bfe721d1 KH |
830 | @deffn Command replace-buffer-in-windows buffer |
831 | This function replaces @var{buffer} with some other buffer in all | |
832 | windows displaying it. The other buffer used is chosen with | |
833 | @code{other-buffer}. In the usual applications of this function, you | |
834 | don't care which other buffer is used; you just want to make sure that | |
835 | @var{buffer} is no longer displayed. | |
836 | ||
837 | This function returns @code{nil}. | |
838 | @end deffn | |
839 | ||
b1b12a8e RS |
840 | @node Choosing Window |
841 | @section Choosing a Window for Display | |
842 | ||
c638661f | 843 | This section describes the basic facility that chooses a window to |
b1b12a8e RS |
844 | display a buffer in---@code{display-buffer}. All the higher-level |
845 | functions and commands use this subroutine. Here we describe how to use | |
846 | @code{display-buffer} and how to customize it. | |
847 | ||
f9f59935 | 848 | @deffn Command display-buffer buffer-or-name &optional not-this-window frame |
b1b12a8e RS |
849 | This command makes @var{buffer-or-name} appear in some window, like |
850 | @code{pop-to-buffer}, but it does not select that window and does not | |
851 | make the buffer current. The identity of the selected window is | |
852 | unaltered by this function. | |
853 | ||
854 | If @var{not-this-window} is non-@code{nil}, it means to display the | |
855 | specified buffer in a window other than the selected one, even if it is | |
856 | already on display in the selected window. This can cause the buffer to | |
857 | appear in two windows at once. Otherwise, if @var{buffer-or-name} is | |
858 | already being displayed in any window, that is good enough, so this | |
859 | function does nothing. | |
860 | ||
861 | @code{display-buffer} returns the window chosen to display | |
862 | @var{buffer-or-name}. | |
863 | ||
f9f59935 | 864 | If the argument @var{frame} is non-@code{nil}, it specifies which frames |
1911e6e5 RS |
865 | to check when deciding whether the buffer is already displayed. If the |
866 | buffer is already displayed in some window on one of these frames, | |
867 | @code{display-buffer} simply returns that window. Here are the possible | |
868 | values of @var{frame}: | |
869 | ||
870 | @itemize @bullet | |
871 | @item | |
872 | If it is @code{nil}, consider windows on the selected frame. | |
873 | @item | |
874 | If it is @code{t}, consider windows on all frames. | |
875 | @item | |
876 | If it is @code{visible}, consider windows on all visible frames. | |
877 | @item | |
878 | If it is 0, consider windows on all visible or iconified frames. | |
879 | @item | |
880 | If it is a frame, consider windows on that frame. | |
881 | @end itemize | |
f9f59935 | 882 | |
b1b12a8e RS |
883 | Precisely how @code{display-buffer} finds or creates a window depends on |
884 | the variables described below. | |
885 | @end deffn | |
886 | ||
704bdba1 GM |
887 | @defopt display-buffer-reuse-frames |
888 | If this variable is non-@code{nil}, @code{display-buffer} searches | |
889 | existing frames for a window displaying the buffer. If the buffer is | |
890 | already displayed in a window in some frame, @code{display-buffer} makes | |
891 | the frame visible and raises it, to use that window. If the buffer is | |
892 | not already displayed, or if @code{display-buffer-reuse-frames} is | |
893 | @code{nil}, @code{display-buffer}'s behavior is determined by other | |
894 | variables, described below. | |
895 | @end defopt | |
896 | ||
b1b12a8e RS |
897 | @defopt pop-up-windows |
898 | This variable controls whether @code{display-buffer} makes new windows. | |
899 | If it is non-@code{nil} and there is only one window, then that window | |
900 | is split. If it is @code{nil}, then @code{display-buffer} does not | |
901 | split the single window, but uses it whole. | |
902 | @end defopt | |
903 | ||
904 | @defopt split-height-threshold | |
905 | This variable determines when @code{display-buffer} may split a window, | |
906 | if there are multiple windows. @code{display-buffer} always splits the | |
907 | largest window if it has at least this many lines. If the largest | |
908 | window is not this tall, it is split only if it is the sole window and | |
909 | @code{pop-up-windows} is non-@code{nil}. | |
910 | @end defopt | |
911 | ||
4f0308e1 GM |
912 | @defopt even-window-heights |
913 | This variable determines if @code{display-buffer} should even out window | |
914 | heights if the buffer gets displayed in an existing window, above or | |
915 | beneath another existing window. If @code{even-window-heights} is | |
916 | @code{t}, the default, window heights will be evened out. If | |
917 | @code{even-window-heights} is @code{nil}, the orginal window heights | |
918 | will be left alone. | |
fbd9f276 | 919 | @end defopt |
4f0308e1 | 920 | |
b1b12a8e RS |
921 | @c Emacs 19 feature |
922 | @defopt pop-up-frames | |
923 | This variable controls whether @code{display-buffer} makes new frames. | |
924 | If it is non-@code{nil}, @code{display-buffer} looks for an existing | |
925 | window already displaying the desired buffer, on any visible frame. If | |
926 | it finds one, it returns that window. Otherwise it makes a new frame. | |
927 | The variables @code{pop-up-windows} and @code{split-height-threshold} do | |
928 | not matter if @code{pop-up-frames} is non-@code{nil}. | |
929 | ||
930 | If @code{pop-up-frames} is @code{nil}, then @code{display-buffer} either | |
931 | splits a window or reuses one. | |
932 | ||
933 | @xref{Frames}, for more information. | |
934 | @end defopt | |
935 | ||
936 | @c Emacs 19 feature | |
937 | @defvar pop-up-frame-function | |
938 | This variable specifies how to make a new frame if @code{pop-up-frames} | |
939 | is non-@code{nil}. | |
940 | ||
941 | Its value should be a function of no arguments. When | |
942 | @code{display-buffer} makes a new frame, it does so by calling that | |
943 | function, which should return a frame. The default value of the | |
c638661f | 944 | variable is a function that creates a frame using parameters from |
b1b12a8e RS |
945 | @code{pop-up-frame-alist}. |
946 | @end defvar | |
947 | ||
8241495d | 948 | @defopt pop-up-frame-alist |
b1b12a8e RS |
949 | This variable holds an alist specifying frame parameters used when |
950 | @code{display-buffer} makes a new frame. @xref{Frame Parameters}, for | |
951 | more information about frame parameters. | |
8241495d | 952 | @end defopt |
b1b12a8e | 953 | |
1911e6e5 | 954 | @defopt special-display-buffer-names |
c2264295 RS |
955 | A list of buffer names for buffers that should be displayed specially. |
956 | If the buffer's name is in this list, @code{display-buffer} handles the | |
957 | buffer specially. | |
958 | ||
959 | By default, special display means to give the buffer a dedicated frame. | |
bfe721d1 KH |
960 | |
961 | If an element is a list, instead of a string, then the @sc{car} of the | |
962 | list is the buffer name, and the rest of the list says how to create the | |
963 | frame. There are two possibilities for the rest of the list. It can be | |
964 | an alist, specifying frame parameters, or it can contain a function and | |
965 | arguments to give to it. (The function's first argument is always the | |
966 | buffer to be displayed; the arguments from the list come after that.) | |
1911e6e5 | 967 | @end defopt |
c2264295 | 968 | |
1911e6e5 | 969 | @defopt special-display-regexps |
c2264295 RS |
970 | A list of regular expressions that specify buffers that should be |
971 | displayed specially. If the buffer's name matches any of the regular | |
972 | expressions in this list, @code{display-buffer} handles the buffer | |
973 | specially. | |
974 | ||
975 | By default, special display means to give the buffer a dedicated frame. | |
bfe721d1 KH |
976 | |
977 | If an element is a list, instead of a string, then the @sc{car} of the | |
978 | list is the regular expression, and the rest of the list says how to | |
979 | create the frame. See above, under @code{special-display-buffer-names}. | |
1911e6e5 | 980 | @end defopt |
c2264295 RS |
981 | |
982 | @defvar special-display-function | |
983 | This variable holds the function to call to display a buffer specially. | |
984 | It receives the buffer as an argument, and should return the window in | |
985 | which it is displayed. | |
986 | ||
987 | The default value of this variable is | |
988 | @code{special-display-popup-frame}. | |
989 | @end defvar | |
990 | ||
8241495d | 991 | @defun special-display-popup-frame buffer &rest args |
c2264295 RS |
992 | This function makes @var{buffer} visible in a frame of its own. If |
993 | @var{buffer} is already displayed in a window in some frame, it makes | |
994 | the frame visible and raises it, to use that window. Otherwise, it | |
995 | creates a frame that will be dedicated to @var{buffer}. | |
c638661f | 996 | |
8241495d RS |
997 | If @var{args} is an alist, it specifies frame parameters for the new |
998 | frame. | |
999 | ||
1000 | If @var{args} is a list whose @sc{car} is a symbol, then @code{(car | |
1001 | @var{args})} is called as a function to actually create and set up the | |
1002 | frame; it is called with @var{buffer} as first argument, and @code{(cdr | |
1003 | @var{args})} as additional arguments. | |
1004 | ||
1005 | This function always uses an existing window displaying @var{buffer}, | |
1006 | whether or not it is in a frame of its own; but if you set up the above | |
1007 | variables in your init file, before @var{buffer} was created, then | |
1008 | presumably the window was previously made by this function. | |
c2264295 RS |
1009 | @end defun |
1010 | ||
1011 | @defopt special-display-frame-alist | |
1012 | This variable holds frame parameters for | |
1013 | @code{special-display-popup-frame} to use when it creates a frame. | |
1014 | @end defopt | |
1015 | ||
864bd34b | 1016 | @defopt same-window-buffer-names |
bfe721d1 KH |
1017 | A list of buffer names for buffers that should be displayed in the |
1018 | selected window. If the buffer's name is in this list, | |
1019 | @code{display-buffer} handles the buffer by switching to it in the | |
1020 | selected window. | |
864bd34b | 1021 | @end defopt |
bfe721d1 | 1022 | |
864bd34b | 1023 | @defopt same-window-regexps |
bfe721d1 KH |
1024 | A list of regular expressions that specify buffers that should be |
1025 | displayed in the selected window. If the buffer's name matches any of | |
1026 | the regular expressions in this list, @code{display-buffer} handles the | |
1027 | buffer by switching to it in the selected window. | |
864bd34b | 1028 | @end defopt |
bfe721d1 | 1029 | |
b1b12a8e RS |
1030 | @c Emacs 19 feature |
1031 | @defvar display-buffer-function | |
1032 | This variable is the most flexible way to customize the behavior of | |
1033 | @code{display-buffer}. If it is non-@code{nil}, it should be a function | |
1034 | that @code{display-buffer} calls to do the work. The function should | |
1035 | accept two arguments, the same two arguments that @code{display-buffer} | |
1036 | received. It should choose or create a window, display the specified | |
1037 | buffer, and then return the window. | |
1038 | ||
1039 | This hook takes precedence over all the other options and hooks | |
1040 | described above. | |
1041 | @end defvar | |
1042 | ||
1043 | @c Emacs 19 feature | |
1044 | @cindex dedicated window | |
1045 | A window can be marked as ``dedicated'' to its buffer. Then | |
969fe9b5 RS |
1046 | @code{display-buffer} will not try to use that window to display any |
1047 | other buffer. | |
b1b12a8e RS |
1048 | |
1049 | @defun window-dedicated-p window | |
1050 | This function returns @code{t} if @var{window} is marked as dedicated; | |
1051 | otherwise @code{nil}. | |
1052 | @end defun | |
1053 | ||
1054 | @defun set-window-dedicated-p window flag | |
1055 | This function marks @var{window} as dedicated if @var{flag} is | |
1056 | non-@code{nil}, and nondedicated otherwise. | |
1057 | @end defun | |
1058 | ||
1059 | @node Window Point | |
1060 | @section Windows and Point | |
1061 | @cindex window position | |
1062 | @cindex window point | |
1063 | @cindex position in window | |
1064 | @cindex point in window | |
1065 | ||
1066 | Each window has its own value of point, independent of the value of | |
1067 | point in other windows displaying the same buffer. This makes it useful | |
1068 | to have multiple windows showing one buffer. | |
1069 | ||
1070 | @itemize @bullet | |
1071 | @item | |
1072 | The window point is established when a window is first created; it is | |
1073 | initialized from the buffer's point, or from the window point of another | |
1074 | window opened on the buffer if such a window exists. | |
1075 | ||
1076 | @item | |
f9f59935 RS |
1077 | Selecting a window sets the value of point in its buffer from the |
1078 | window's value of point. Conversely, deselecting a window sets the | |
1079 | window's value of point from that of the buffer. Thus, when you switch | |
1080 | between windows that display a given buffer, the point value for the | |
1081 | selected window is in effect in the buffer, while the point values for | |
1082 | the other windows are stored in those windows. | |
b1b12a8e RS |
1083 | |
1084 | @item | |
1085 | As long as the selected window displays the current buffer, the window's | |
1086 | point and the buffer's point always move together; they remain equal. | |
1087 | ||
1088 | @item | |
1089 | @xref{Positions}, for more details on buffer positions. | |
1090 | @end itemize | |
1091 | ||
1092 | As far as the user is concerned, point is where the cursor is, and | |
1093 | when the user switches to another buffer, the cursor jumps to the | |
1094 | position of point in that buffer. | |
1095 | ||
8241495d | 1096 | @defun window-point &optional window |
b1b12a8e RS |
1097 | This function returns the current position of point in @var{window}. |
1098 | For a nonselected window, this is the value point would have (in that | |
8241495d RS |
1099 | window's buffer) if that window were selected. If @var{window} is |
1100 | @code{nil}, the selected window is used. | |
b1b12a8e RS |
1101 | |
1102 | When @var{window} is the selected window and its buffer is also the | |
1103 | current buffer, the value returned is the same as point in that buffer. | |
1104 | ||
1105 | Strictly speaking, it would be more correct to return the | |
1106 | ``top-level'' value of point, outside of any @code{save-excursion} | |
1107 | forms. But that value is hard to find. | |
1108 | @end defun | |
1109 | ||
1110 | @defun set-window-point window position | |
1111 | This function positions point in @var{window} at position | |
1112 | @var{position} in @var{window}'s buffer. | |
1113 | @end defun | |
1114 | ||
1115 | @node Window Start | |
1116 | @section The Window Start Position | |
1117 | ||
1118 | Each window contains a marker used to keep track of a buffer position | |
c638661f | 1119 | that specifies where in the buffer display should start. This position |
b1b12a8e RS |
1120 | is called the @dfn{display-start} position of the window (or just the |
1121 | @dfn{start}). The character after this position is the one that appears | |
1122 | at the upper left corner of the window. It is usually, but not | |
1123 | inevitably, at the beginning of a text line. | |
1124 | ||
1125 | @defun window-start &optional window | |
1126 | @cindex window top line | |
1127 | This function returns the display-start position of window | |
1128 | @var{window}. If @var{window} is @code{nil}, the selected window is | |
3c29caa8 | 1129 | used. For example, |
b1b12a8e RS |
1130 | |
1131 | @example | |
1132 | @group | |
1133 | (window-start) | |
1134 | @result{} 7058 | |
1135 | @end group | |
1136 | @end example | |
1137 | ||
c638661f | 1138 | When you create a window, or display a different buffer in it, the |
b1b12a8e RS |
1139 | display-start position is set to a display-start position recently used |
1140 | for the same buffer, or 1 if the buffer doesn't have any. | |
1141 | ||
ea951766 | 1142 | Redisplay updates the window-start position (if you have not specified |
8241495d RS |
1143 | it explicitly since the previous redisplay)---for example, to make sure |
1144 | point appears on the screen. Nothing except redisplay automatically | |
1145 | changes the window-start position; if you move point, do not expect the | |
1146 | window-start position to change in response until after the next | |
1147 | redisplay. | |
ea951766 RS |
1148 | |
1149 | For a realistic example of using @code{window-start}, see the | |
1150 | description of @code{count-lines} in @ref{Text Lines}. | |
b1b12a8e RS |
1151 | @end defun |
1152 | ||
969fe9b5 | 1153 | @defun window-end &optional window update |
b1b12a8e RS |
1154 | This function returns the position of the end of the display in window |
1155 | @var{window}. If @var{window} is @code{nil}, the selected window is | |
1156 | used. | |
c638661f | 1157 | |
6c7418db RS |
1158 | Simply changing the buffer text or moving point does not update the |
1159 | value that @code{window-end} returns. The value is updated only when | |
969fe9b5 | 1160 | Emacs redisplays and redisplay completes without being preempted. |
6c7418db | 1161 | |
c638661f | 1162 | If the last redisplay of @var{window} was preempted, and did not finish, |
a283f4a3 | 1163 | Emacs does not know the position of the end of display in that window. |
969fe9b5 | 1164 | In that case, this function returns @code{nil}. |
c638661f | 1165 | |
41448f63 RS |
1166 | If @var{update} is non-@code{nil}, @code{window-end} always returns an |
1167 | up-to-date value for where the window ends, based on the current | |
1168 | @code{window-start} value. If the saved value is valid, | |
1169 | @code{window-end} returns that; otherwise it computes the correct | |
969fe9b5 | 1170 | value by scanning the buffer text. |
41448f63 RS |
1171 | |
1172 | Even if @var{update} is non-@code{nil}, @code{window-end} does not | |
1173 | attempt to scroll the display if point has moved off the screen, the | |
1174 | way real redisplay would do. It does not alter the | |
1175 | @code{window-start} value. In effect, it reports where the displayed | |
1176 | text will end if scrolling is not required. | |
b1b12a8e RS |
1177 | @end defun |
1178 | ||
1179 | @defun set-window-start window position &optional noforce | |
1180 | This function sets the display-start position of @var{window} to | |
c638661f | 1181 | @var{position} in @var{window}'s buffer. It returns @var{position}. |
b1b12a8e RS |
1182 | |
1183 | The display routines insist that the position of point be visible when a | |
1184 | buffer is displayed. Normally, they change the display-start position | |
1185 | (that is, scroll the window) whenever necessary to make point visible. | |
1186 | However, if you specify the start position with this function using | |
1187 | @code{nil} for @var{noforce}, it means you want display to start at | |
1188 | @var{position} even if that would put the location of point off the | |
1189 | screen. If this does place point off screen, the display routines move | |
1190 | point to the left margin on the middle line in the window. | |
1191 | ||
1192 | For example, if point @w{is 1} and you set the start of the window @w{to | |
1193 | 2}, then point would be ``above'' the top of the window. The display | |
1194 | routines will automatically move point if it is still 1 when redisplay | |
1195 | occurs. Here is an example: | |
1196 | ||
1197 | @example | |
1198 | @group | |
1199 | ;; @r{Here is what @samp{foo} looks like before executing} | |
1200 | ;; @r{the @code{set-window-start} expression.} | |
1201 | @end group | |
1202 | ||
1203 | @group | |
1204 | ---------- Buffer: foo ---------- | |
1205 | @point{}This is the contents of buffer foo. | |
1206 | 2 | |
1207 | 3 | |
1208 | 4 | |
1209 | 5 | |
1210 | 6 | |
1211 | ---------- Buffer: foo ---------- | |
1212 | @end group | |
1213 | ||
1214 | @group | |
1215 | (set-window-start | |
1216 | (selected-window) | |
1217 | (1+ (window-start))) | |
1218 | @result{} 2 | |
1219 | @end group | |
1220 | ||
1221 | @group | |
1222 | ;; @r{Here is what @samp{foo} looks like after executing} | |
1223 | ;; @r{the @code{set-window-start} expression.} | |
1224 | ---------- Buffer: foo ---------- | |
1225 | his is the contents of buffer foo. | |
1226 | 2 | |
1227 | 3 | |
1228 | @point{}4 | |
1229 | 5 | |
1230 | 6 | |
1231 | ---------- Buffer: foo ---------- | |
1232 | @end group | |
1233 | @end example | |
1234 | ||
1235 | If @var{noforce} is non-@code{nil}, and @var{position} would place point | |
1236 | off screen at the next redisplay, then redisplay computes a new window-start | |
1237 | position that works well with point, and thus @var{position} is not used. | |
b1b12a8e RS |
1238 | @end defun |
1239 | ||
00480554 | 1240 | @defun pos-visible-in-window-p &optional position window partially |
601bda2e | 1241 | This function returns @code{t} if @var{position} is within the range of |
00480554 MB |
1242 | text currently visible on the screen in @var{window}. It returns |
1243 | @code{nil} if @var{position} is scrolled vertically or horizontally out | |
1244 | of view. Locations that are partially obscured are not considered | |
1245 | visible unless @var{partially} is non-@code{nil}. The argument | |
1246 | @var{position} defaults to the current position of point in | |
1247 | @var{window}; @var{window}, to the selected window. | |
1248 | ||
1249 | Here is an example: | |
b1b12a8e RS |
1250 | |
1251 | @example | |
1252 | @group | |
1253 | (or (pos-visible-in-window-p | |
1254 | (point) (selected-window)) | |
1255 | (recenter 0)) | |
1256 | @end group | |
1257 | @end example | |
b1b12a8e RS |
1258 | @end defun |
1259 | ||
8241495d RS |
1260 | @node Textual Scrolling |
1261 | @section Textual Scrolling | |
1262 | @cindex textual scrolling | |
1263 | @cindex scrolling textually | |
1264 | ||
1265 | @dfn{Textual scrolling} means moving the text up or down though a | |
1266 | window. It works by changing the value of the window's display-start | |
1267 | location. It may also change the value of @code{window-point} to keep | |
1268 | point on the screen. | |
b1b12a8e | 1269 | |
8241495d RS |
1270 | Textual scrolling was formerly called ``vertical scrolling,'' but we |
1271 | changed its name to distinguish it from the new vertical fractional | |
1272 | scrolling feature (@pxref{Vertical Scrolling}). | |
b1b12a8e RS |
1273 | |
1274 | In the commands @code{scroll-up} and @code{scroll-down}, the directions | |
1275 | ``up'' and ``down'' refer to the motion of the text in the buffer at which | |
1276 | you are looking through the window. Imagine that the text is | |
1277 | written on a long roll of paper and that the scrolling commands move the | |
1278 | paper up and down. Thus, if you are looking at text in the middle of a | |
1279 | buffer and repeatedly call @code{scroll-down}, you will eventually see | |
1280 | the beginning of the buffer. | |
1281 | ||
1282 | Some people have urged that the opposite convention be used: they | |
1283 | imagine that the window moves over text that remains in place. Then | |
1284 | ``down'' commands would take you to the end of the buffer. This view is | |
1285 | more consistent with the actual relationship between windows and the | |
1286 | text in the buffer, but it is less like what the user sees. The | |
1287 | position of a window on the terminal does not move, and short scrolling | |
1288 | commands clearly move the text up or down on the screen. We have chosen | |
1289 | names that fit the user's point of view. | |
1290 | ||
8241495d RS |
1291 | The textual scrolling functions (aside from |
1292 | @code{scroll-other-window}) have unpredictable results if the current | |
1293 | buffer is different from the buffer that is displayed in the selected | |
1294 | window. @xref{Current Buffer}. | |
b1b12a8e RS |
1295 | |
1296 | @deffn Command scroll-up &optional count | |
1297 | This function scrolls the text in the selected window upward | |
1298 | @var{count} lines. If @var{count} is negative, scrolling is actually | |
1299 | downward. | |
1300 | ||
1301 | If @var{count} is @code{nil} (or omitted), then the length of scroll | |
1302 | is @code{next-screen-context-lines} lines less than the usable height of | |
1303 | the window (not counting its mode line). | |
1304 | ||
1305 | @code{scroll-up} returns @code{nil}. | |
1306 | @end deffn | |
1307 | ||
1308 | @deffn Command scroll-down &optional count | |
1309 | This function scrolls the text in the selected window downward | |
1310 | @var{count} lines. If @var{count} is negative, scrolling is actually | |
1311 | upward. | |
1312 | ||
1313 | If @var{count} is omitted or @code{nil}, then the length of the scroll | |
1314 | is @code{next-screen-context-lines} lines less than the usable height of | |
c638661f | 1315 | the window (not counting its mode line). |
b1b12a8e RS |
1316 | |
1317 | @code{scroll-down} returns @code{nil}. | |
1318 | @end deffn | |
1319 | ||
1320 | @deffn Command scroll-other-window &optional count | |
1321 | This function scrolls the text in another window upward @var{count} | |
1322 | lines. Negative values of @var{count}, or @code{nil}, are handled | |
1323 | as in @code{scroll-up}. | |
1324 | ||
8241495d RS |
1325 | You can specify which buffer to scroll by setting the variable |
1326 | @code{other-window-scroll-buffer} to a buffer. If that buffer isn't | |
1327 | already displayed, @code{scroll-other-window} displays it in some | |
1328 | window. | |
1329 | ||
1330 | When the selected window is the minibuffer, the next window is normally | |
1331 | the one at the top left corner. You can specify a different window to | |
1332 | scroll, when the minibuffer is selected, by setting the variable | |
b1b12a8e RS |
1333 | @code{minibuffer-scroll-window}. This variable has no effect when any |
1334 | other window is selected. @xref{Minibuffer Misc}. | |
1335 | ||
1336 | When the minibuffer is active, it is the next window if the selected | |
1337 | window is the one at the bottom right corner. In this case, | |
1338 | @code{scroll-other-window} attempts to scroll the minibuffer. If the | |
1339 | minibuffer contains just one line, it has nowhere to scroll to, so the | |
1340 | line reappears after the echo area momentarily displays the message | |
1341 | ``Beginning of buffer''. | |
1342 | @end deffn | |
1343 | ||
1344 | @c Emacs 19 feature | |
1345 | @defvar other-window-scroll-buffer | |
1346 | If this variable is non-@code{nil}, it tells @code{scroll-other-window} | |
1347 | which buffer to scroll. | |
1348 | @end defvar | |
1349 | ||
1911e6e5 RS |
1350 | @defopt scroll-margin |
1351 | This option specifies the size of the scroll margin---a minimum number | |
1352 | of lines between point and the top or bottom of a window. Whenever | |
1353 | point gets within this many lines of the top or bottom of the window, | |
1354 | the window scrolls automatically (if possible) to move point out of the | |
1355 | margin, closer to the center of the window. | |
1356 | @end defopt | |
1357 | ||
1911e6e5 | 1358 | @defopt scroll-conservatively |
b1b12a8e | 1359 | This variable controls how scrolling is done automatically when point |
1911e6e5 RS |
1360 | moves off the screen (or into the scroll margin). If the value is zero, |
1361 | then redisplay scrolls the text to center point vertically in the | |
1362 | window. If the value is a positive integer @var{n}, then redisplay | |
1363 | scrolls the window up to @var{n} lines in either direction, if that will | |
1364 | bring point back into view. Otherwise, it centers point. The default | |
1365 | value is zero. | |
765712a7 GM |
1366 | |
1367 | A value of @code{nil} is equivalent to .5, since it centers point. This | |
1368 | variable automatically becomes buffer-local when set in any fashion. | |
1911e6e5 RS |
1369 | @end defopt |
1370 | ||
04c1025b GM |
1371 | @defopt scroll-up-aggressively |
1372 | @tindex scroll-up-aggressively | |
1373 | The value of this variable should be either @code{nil} or a fraction | |
1374 | @var{f} between 0 and 1. If it is a fraction, that specifies where on | |
1375 | the screen to put point when scrolling upward. More precisely, when a | |
1376 | window scrolls up because point is above the window start, the new start | |
1377 | position is chosen to put point @var{f} part of the window height from | |
1378 | the top. The larger @var{f}, the more aggressive the scrolling. | |
1379 | ||
2468d0c0 DL |
1380 | A value of @code{nil} is equivalent to .5, since its effect is to center |
1381 | point. This variable automatically becomes buffer-local when set in any | |
1382 | fashion. | |
04c1025b GM |
1383 | @end defopt |
1384 | ||
1385 | @defopt scroll-down-aggressively | |
1386 | @tindex scroll-down-aggressively | |
1387 | Likewise, for scrolling down. The value, @var{f}, specifies how far | |
1388 | point should be placed from the bottom of the window; thus, as with | |
1389 | @code{scroll-up-aggressively}, a larger value scrolls more aggressively. | |
1390 | @end defopt | |
1391 | ||
1911e6e5 RS |
1392 | @defopt scroll-step |
1393 | This variable is an older variant of @code{scroll-conservatively}. The | |
1394 | difference is that it if its value is @var{n}, that permits scrolling | |
1395 | only by precisely @var{n} lines, not a smaller number. This feature | |
1396 | does not work with @code{scroll-margin}. The default value is zero. | |
1397 | @end defopt | |
1398 | ||
1911e6e5 RS |
1399 | @defopt scroll-preserve-screen-position |
1400 | If this option is non-@code{nil}, the scroll functions move point so | |
1401 | that the vertical position of the cursor is unchanged, when that is | |
1402 | possible. | |
b1b12a8e RS |
1403 | @end defopt |
1404 | ||
1405 | @defopt next-screen-context-lines | |
1406 | The value of this variable is the number of lines of continuity to | |
1407 | retain when scrolling by full screens. For example, @code{scroll-up} | |
1408 | with an argument of @code{nil} scrolls so that this many lines at the | |
1409 | bottom of the window appear instead at the top. The default value is | |
1410 | @code{2}. | |
1411 | @end defopt | |
1412 | ||
1413 | @deffn Command recenter &optional count | |
1414 | @cindex centering point | |
1415 | This function scrolls the selected window to put the text where point | |
1416 | is located at a specified vertical position within the window. | |
1417 | ||
1418 | If @var{count} is a nonnegative number, it puts the line containing | |
1419 | point @var{count} lines down from the top of the window. If @var{count} | |
1420 | is a negative number, then it counts upward from the bottom of the | |
1421 | window, so that @minus{}1 stands for the last usable line in the window. | |
1422 | If @var{count} is a non-@code{nil} list, then it stands for the line in | |
1423 | the middle of the window. | |
1424 | ||
1425 | If @var{count} is @code{nil}, @code{recenter} puts the line containing | |
1426 | point in the middle of the window, then clears and redisplays the entire | |
1427 | selected frame. | |
1428 | ||
1429 | When @code{recenter} is called interactively, @var{count} is the raw | |
1430 | prefix argument. Thus, typing @kbd{C-u} as the prefix sets the | |
1431 | @var{count} to a non-@code{nil} list, while typing @kbd{C-u 4} sets | |
1432 | @var{count} to 4, which positions the current line four lines from the | |
1433 | top. | |
1434 | ||
c638661f RS |
1435 | With an argument of zero, @code{recenter} positions the current line at |
1436 | the top of the window. This action is so handy that some people make a | |
1437 | separate key binding to do this. For example, | |
b1b12a8e RS |
1438 | |
1439 | @example | |
1440 | @group | |
1441 | (defun line-to-top-of-window () | |
1442 | "Scroll current line to top of window. | |
1443 | Replaces three keystroke sequence C-u 0 C-l." | |
3c29caa8 | 1444 | (interactive) |
b1b12a8e RS |
1445 | (recenter 0)) |
1446 | ||
3c29caa8 | 1447 | (global-set-key [kp-multiply] 'line-to-top-of-window) |
b1b12a8e RS |
1448 | @end group |
1449 | @end example | |
1450 | @end deffn | |
1451 | ||
8241495d RS |
1452 | @node Vertical Scrolling |
1453 | @section Vertical Fractional Scrolling | |
1454 | @cindex Vertical Fractional Scrolling | |
1455 | ||
1456 | @dfn{Vertical fractional scrolling} means shifting the image in the | |
1457 | window up or down by a specified multiple or fraction of a line. | |
1458 | Starting in Emacs 21, each window has a @dfn{vertical scroll position}, | |
1459 | which is a number, never less than zero. It specifies how far to raise | |
1460 | the contents of the window. Raising the window contents generally makes | |
1461 | all or part of some lines disappear off the top, and all or part of some | |
1462 | other lines appear at the bottom. The usual value is zero. | |
1463 | ||
1464 | The vertical scroll position is measured in units of the normal line | |
1465 | height, which is the height of the default font. Thus, if the value is | |
1466 | .5, that means the window contents are scrolled up half the normal line | |
1467 | height. If it is 3.3, that means the window contents are scrolled up | |
1468 | somewhat over three times the normal line height. | |
1469 | ||
1470 | What fraction of a line the vertical scrolling covers, or how many | |
1471 | lines, depends on what the lines contain. A value of .5 could scroll a | |
1472 | line whose height is very short off the screen, while a value of 3.3 | |
1473 | could scroll just part of the way through a tall line or an image. | |
1474 | ||
1475 | @defun window-vscroll &optional window | |
1476 | This function returns the current vertical scroll position of | |
1477 | @var{window}, If @var{window} is @code{nil}, the selected window is | |
1478 | used. | |
1479 | ||
1480 | @example | |
1481 | @group | |
1482 | (window-vscroll) | |
1483 | @result{} 0 | |
1484 | @end group | |
1485 | @end example | |
1486 | @end defun | |
1487 | ||
1488 | @defun set-window-vscroll window lines | |
1489 | This function sets @var{window}'s vertical scroll position to | |
1490 | @var{lines}. The argument @var{lines} should be zero or positive; if | |
1491 | not, it is taken as zero. | |
1492 | ||
eb687116 EZ |
1493 | If @var{window} is @code{nil}, the selected window is used. |
1494 | ||
8241495d RS |
1495 | The actual vertical scroll position must always correspond |
1496 | to an integral number of pixels, so the value you specify | |
1497 | is rounded accordingly. | |
1498 | ||
1499 | The return value is the result of this rounding. | |
1500 | ||
1501 | @example | |
1502 | @group | |
1503 | (set-window-vscroll (selected-window) 1.2) | |
1504 | @result{} 1.13 | |
1505 | @end group | |
1506 | @end example | |
1507 | @end defun | |
1508 | ||
b1b12a8e RS |
1509 | @node Horizontal Scrolling |
1510 | @section Horizontal Scrolling | |
1511 | @cindex horizontal scrolling | |
1512 | ||
8241495d RS |
1513 | @dfn{Horizontal scrolling} means shifting the image in the window left |
1514 | or right by a specified multiple of the normal character width. Each | |
1515 | window has a @dfn{vertical scroll position}, which is a number, never | |
1516 | less than zero. It specifies how far to shift the contents left. | |
1517 | Shifting the window contents left generally makes all or part of some | |
1518 | characters disappear off the left, and all or part of some other | |
1519 | characters appear at the right. The usual value is zero. | |
1520 | ||
1521 | The horizontal scroll position is measured in units of the normal | |
1522 | character width, which is the width of space in the default font. Thus, | |
1523 | if the value is 5, that means the window contents are scrolled left by 5 | |
c400241b | 1524 | times the normal character width. How many characters actually |
8241495d RS |
1525 | disappear off to the left depends on their width, and could vary from |
1526 | line to line. | |
1527 | ||
1528 | Because we read from side to side in the ``inner loop'', and from top | |
1529 | to bottom in the ``outer loop'', the effect of horizontal scrolling is | |
1530 | not like that of textual or vertical scrolling. Textual scrolling | |
1531 | involves selection of a portion of text to display, and vertical | |
1532 | scrolling moves the window contents contiguously; but horizontal | |
1533 | scrolling causes part of @emph{each line} to go off screen. | |
b1b12a8e RS |
1534 | |
1535 | Usually, no horizontal scrolling is in effect; then the leftmost | |
1536 | column is at the left edge of the window. In this state, scrolling to | |
8241495d RS |
1537 | the right is meaningless, since there is no data to the left of the edge |
1538 | to be revealed by it; so this is not allowed. Scrolling to the left is | |
1539 | allowed; it scrolls the first columns of text off the edge of the window | |
1540 | and can reveal additional columns on the right that were truncated | |
1541 | before. Once a window has a nonzero amount of leftward horizontal | |
1542 | scrolling, you can scroll it back to the right, but only so far as to | |
1543 | reduce the net horizontal scroll to zero. There is no limit to how far | |
1544 | left you can scroll, but eventually all the text will disappear off the | |
1545 | left edge. | |
1546 | ||
71cd13fa | 1547 | @vindex automatic-hscrolling |
8241495d | 1548 | In Emacs 21, redisplay automatically alters the horizontal scrolling |
03ff8aab GM |
1549 | of a window as necessary to ensure that point is always visible, if |
1550 | @code{automatic-hscrolling} is set. However, you can still set the | |
1551 | horizontal scrolling value explicitly. The value you specify serves as | |
1552 | a lower bound for automatic scrolling, i.e. automatic scrolling | |
1553 | will not scroll a window to a column less than the specified one. | |
8241495d RS |
1554 | |
1555 | @deffn Command scroll-left &optional count | |
b1b12a8e | 1556 | This function scrolls the selected window @var{count} columns to the |
8241495d RS |
1557 | left (or to the right if @var{count} is negative). The default |
1558 | for @var{count} is the window width, minus 2. | |
1559 | ||
1560 | The return value is the total amount of leftward horizontal scrolling in | |
1561 | effect after the change---just like the value returned by | |
1562 | @code{window-hscroll} (below). | |
b1b12a8e RS |
1563 | @end deffn |
1564 | ||
8241495d | 1565 | @deffn Command scroll-right &optional count |
b1b12a8e | 1566 | This function scrolls the selected window @var{count} columns to the |
8241495d RS |
1567 | right (or to the left if @var{count} is negative). The default |
1568 | for @var{count} is the window width, minus 2. | |
1569 | ||
1570 | The return value is the total amount of leftward horizontal scrolling in | |
1571 | effect after the change---just like the value returned by | |
1572 | @code{window-hscroll} (below). | |
b1b12a8e RS |
1573 | |
1574 | Once you scroll a window as far right as it can go, back to its normal | |
1575 | position where the total leftward scrolling is zero, attempts to scroll | |
1576 | any farther right have no effect. | |
1577 | @end deffn | |
1578 | ||
1579 | @defun window-hscroll &optional window | |
1580 | This function returns the total leftward horizontal scrolling of | |
1581 | @var{window}---the number of columns by which the text in @var{window} | |
1582 | is scrolled left past the left margin. | |
1583 | ||
1584 | The value is never negative. It is zero when no horizontal scrolling | |
1585 | has been done in @var{window} (which is usually the case). | |
1586 | ||
1587 | If @var{window} is @code{nil}, the selected window is used. | |
1588 | ||
1589 | @example | |
1590 | @group | |
1591 | (window-hscroll) | |
1592 | @result{} 0 | |
1593 | @end group | |
1594 | @group | |
1595 | (scroll-left 5) | |
1596 | @result{} 5 | |
1597 | @end group | |
1598 | @group | |
1599 | (window-hscroll) | |
1600 | @result{} 5 | |
1601 | @end group | |
1602 | @end example | |
1603 | @end defun | |
1604 | ||
1605 | @defun set-window-hscroll window columns | |
1606 | This function sets the number of columns from the left margin that | |
f9f59935 | 1607 | @var{window} is scrolled from the value of @var{columns}. The argument |
b1b12a8e | 1608 | @var{columns} should be zero or positive; if not, it is taken as zero. |
8241495d | 1609 | Fractional values of @var{columns} are not supported at present. |
b1b12a8e RS |
1610 | |
1611 | The value returned is @var{columns}. | |
1612 | ||
1613 | @example | |
1614 | @group | |
1615 | (set-window-hscroll (selected-window) 10) | |
1616 | @result{} 10 | |
1617 | @end group | |
1618 | @end example | |
1619 | @end defun | |
1620 | ||
1621 | Here is how you can determine whether a given position @var{position} | |
1622 | is off the screen due to horizontal scrolling: | |
1623 | ||
1624 | @example | |
1625 | @group | |
c638661f | 1626 | (defun hscroll-on-screen (window position) |
3c29caa8 | 1627 | (save-excursion |
c638661f | 1628 | (goto-char position) |
3c29caa8 | 1629 | (and |
c638661f RS |
1630 | (>= (- (current-column) (window-hscroll window)) 0) |
1631 | (< (- (current-column) (window-hscroll window)) | |
1632 | (window-width window))))) | |
b1b12a8e RS |
1633 | @end group |
1634 | @end example | |
1635 | ||
1636 | @node Size of Window | |
1637 | @section The Size of a Window | |
1638 | @cindex window size | |
1639 | @cindex size of window | |
1640 | ||
1641 | An Emacs window is rectangular, and its size information consists of | |
1642 | the height (the number of lines) and the width (the number of character | |
1643 | positions in each line). The mode line is included in the height. But | |
1644 | the width does not count the scroll bar or the column of @samp{|} | |
c638661f | 1645 | characters that separates side-by-side windows. |
b1b12a8e RS |
1646 | |
1647 | The following three functions return size information about a window: | |
1648 | ||
1649 | @defun window-height &optional window | |
88f7b76a RS |
1650 | This function returns the number of lines in @var{window}, including |
1651 | its mode line and header line, if any. If @var{window} fills its | |
1652 | entire frame except for the echo area, and there is no tool bar, this | |
1653 | is typically one less than the value of @code{frame-height} on that | |
1654 | frame. | |
b1b12a8e RS |
1655 | |
1656 | If @var{window} is @code{nil}, the function uses the selected window. | |
1657 | ||
1658 | @example | |
1659 | @group | |
1660 | (window-height) | |
1661 | @result{} 23 | |
1662 | @end group | |
1663 | @group | |
1664 | (split-window-vertically) | |
1665 | @result{} #<window 4 on windows.texi> | |
1666 | @end group | |
1667 | @group | |
1668 | (window-height) | |
1669 | @result{} 11 | |
1670 | @end group | |
1671 | @end example | |
1672 | @end defun | |
1673 | ||
88f7b76a RS |
1674 | @tindex window-body-height |
1675 | @defun window-body-height &optional window | |
1676 | Like @code{window-height} but the value does not include the | |
1677 | mode line (if any) or the header line (if any). | |
1678 | @end defun | |
1679 | ||
b1b12a8e RS |
1680 | @defun window-width &optional window |
1681 | This function returns the number of columns in @var{window}. If | |
1682 | @var{window} fills its entire frame, this is the same as the value of | |
1683 | @code{frame-width} on that frame. The width does not include the | |
1684 | window's scroll bar or the column of @samp{|} characters that separates | |
1685 | side-by-side windows. | |
1686 | ||
1687 | If @var{window} is @code{nil}, the function uses the selected window. | |
1688 | ||
1689 | @example | |
1690 | @group | |
1691 | (window-width) | |
1692 | @result{} 80 | |
1693 | @end group | |
1694 | @end example | |
1695 | @end defun | |
1696 | ||
1697 | @defun window-edges &optional window | |
1698 | This function returns a list of the edge coordinates of @var{window}. | |
1699 | If @var{window} is @code{nil}, the selected window is used. | |
1700 | ||
1701 | The order of the list is @code{(@var{left} @var{top} @var{right} | |
1702 | @var{bottom})}, all elements relative to 0, 0 at the top left corner of | |
1703 | the frame. The element @var{right} of the value is one more than the | |
1704 | rightmost column used by @var{window}, and @var{bottom} is one more than | |
1705 | the bottommost row used by @var{window} and its mode-line. | |
1706 | ||
8241495d RS |
1707 | If a window has a scroll bar, the right edge value includes the width of |
1708 | the scroll bar. Otherwise, if the window has a neighbor on the right, | |
1709 | its right edge value includes the width of the separator line between | |
1710 | the window and that neighbor. Since the width of the window does not | |
1711 | include this separator, the width does not usually equal the difference | |
1712 | between the right and left edges. | |
b1b12a8e RS |
1713 | |
1714 | Here is the result obtained on a typical 24-line terminal with just one | |
1715 | window: | |
1716 | ||
1717 | @example | |
1718 | @group | |
1719 | (window-edges (selected-window)) | |
1720 | @result{} (0 0 80 23) | |
1721 | @end group | |
1722 | @end example | |
1723 | ||
c638661f RS |
1724 | @noindent |
1725 | The bottom edge is at line 23 because the last line is the echo area. | |
1726 | ||
fb1d9004 RS |
1727 | If @var{window} is at the upper left corner of its frame, then |
1728 | @var{bottom} is the same as the value of @code{(window-height)}, | |
8241495d RS |
1729 | @var{right} is almost the same as the value of @code{(window-width)}, |
1730 | and @var{top} and @var{left} are zero. For example, the edges of the | |
1731 | following window are @w{@samp{0 0 8 5}}. Assuming that the frame has | |
1732 | more than 8 columns, the last column of the window (column 7) holds a | |
1733 | border rather than text. The last row (row 4) holds the mode line, | |
1734 | shown here with @samp{xxxxxxxxx}. | |
b1b12a8e RS |
1735 | |
1736 | @example | |
1737 | @group | |
3c29caa8 | 1738 | 0 |
b1b12a8e | 1739 | _______ |
3c29caa8 DH |
1740 | 0 | | |
1741 | | | | |
1742 | | | | |
1743 | | | | |
b1b12a8e RS |
1744 | xxxxxxxxx 4 |
1745 | ||
3c29caa8 | 1746 | 7 |
b1b12a8e RS |
1747 | @end group |
1748 | @end example | |
1749 | ||
b1b12a8e RS |
1750 | In the following example, let's suppose that the frame is 7 |
1751 | columns wide. Then the edges of the left window are @w{@samp{0 0 4 3}} | |
8241495d | 1752 | and the edges of the right window are @w{@samp{4 0 8 3}}. |
b1b12a8e RS |
1753 | |
1754 | @example | |
1755 | @group | |
1756 | ___ ___ | |
3c29caa8 DH |
1757 | | | | |
1758 | | | | | |
1759 | xxxxxxxxx | |
b1b12a8e RS |
1760 | |
1761 | 0 34 7 | |
1762 | @end group | |
1763 | @end example | |
1764 | @end defun | |
1765 | ||
1766 | @node Resizing Windows | |
1767 | @section Changing the Size of a Window | |
1768 | @cindex window resizing | |
1769 | @cindex changing window size | |
1770 | @cindex window size, changing | |
1771 | ||
1772 | The window size functions fall into two classes: high-level commands | |
1773 | that change the size of windows and low-level functions that access | |
1774 | window size. Emacs does not permit overlapping windows or gaps between | |
1775 | windows, so resizing one window affects other windows. | |
1776 | ||
1777 | @deffn Command enlarge-window size &optional horizontal | |
c638661f | 1778 | This function makes the selected window @var{size} lines taller, |
b1b12a8e RS |
1779 | stealing lines from neighboring windows. It takes the lines from one |
1780 | window at a time until that window is used up, then takes from another. | |
1781 | If a window from which lines are stolen shrinks below | |
1782 | @code{window-min-height} lines, that window disappears. | |
1783 | ||
1784 | If @var{horizontal} is non-@code{nil}, this function makes | |
1785 | @var{window} wider by @var{size} columns, stealing columns instead of | |
1786 | lines. If a window from which columns are stolen shrinks below | |
1787 | @code{window-min-width} columns, that window disappears. | |
1788 | ||
c638661f RS |
1789 | If the requested size would exceed that of the window's frame, then the |
1790 | function makes the window occupy the entire height (or width) of the | |
1791 | frame. | |
b1b12a8e | 1792 | |
8241495d RS |
1793 | If there are various other windows from which lines or columns can be |
1794 | stolen, and some of them specify fixed size (using | |
1795 | @code{window-size-fixed}, see below), they are left untouched while | |
1796 | other windows are ``robbed.'' If it would be necessary to alter the | |
1797 | size of a fixed-size window, @code{enlarge-window} gets an error | |
1798 | instead. | |
1799 | ||
b1b12a8e RS |
1800 | If @var{size} is negative, this function shrinks the window by |
1801 | @minus{}@var{size} lines or columns. If that makes the window smaller | |
1802 | than the minimum size (@code{window-min-height} and | |
1803 | @code{window-min-width}), @code{enlarge-window} deletes the window. | |
1804 | ||
3c29caa8 | 1805 | @code{enlarge-window} returns @code{nil}. |
b1b12a8e RS |
1806 | @end deffn |
1807 | ||
1808 | @deffn Command enlarge-window-horizontally columns | |
1809 | This function makes the selected window @var{columns} wider. | |
1810 | It could be defined as follows: | |
1811 | ||
1812 | @example | |
1813 | @group | |
1814 | (defun enlarge-window-horizontally (columns) | |
1815 | (enlarge-window columns t)) | |
1816 | @end group | |
1817 | @end example | |
1818 | @end deffn | |
1819 | ||
1820 | @deffn Command shrink-window size &optional horizontal | |
1821 | This function is like @code{enlarge-window} but negates the argument | |
1822 | @var{size}, making the selected window smaller by giving lines (or | |
1823 | columns) to the other windows. If the window shrinks below | |
1824 | @code{window-min-height} or @code{window-min-width}, then it disappears. | |
1825 | ||
1826 | If @var{size} is negative, the window is enlarged by @minus{}@var{size} | |
1827 | lines or columns. | |
1828 | @end deffn | |
1829 | ||
1830 | @deffn Command shrink-window-horizontally columns | |
1831 | This function makes the selected window @var{columns} narrower. | |
1832 | It could be defined as follows: | |
1833 | ||
1834 | @example | |
1835 | @group | |
1836 | (defun shrink-window-horizontally (columns) | |
1837 | (shrink-window columns t)) | |
1838 | @end group | |
1839 | @end example | |
1840 | @end deffn | |
1841 | ||
8241495d | 1842 | @deffn Command shrink-window-if-larger-than-buffer &optional window |
1911e6e5 RS |
1843 | This command shrinks @var{window} to be as small as possible while still |
1844 | showing the full contents of its buffer---but not less than | |
8241495d RS |
1845 | @code{window-min-height} lines. If @var{window} is not given, |
1846 | it defaults to the selected window. | |
1911e6e5 RS |
1847 | |
1848 | However, the command does nothing if the window is already too small to | |
1849 | display the whole text of the buffer, or if part of the contents are | |
1850 | currently scrolled off screen, or if the window is not the full width of | |
1851 | its frame, or if the window is the only window in its frame. | |
1852 | @end deffn | |
1853 | ||
8241495d RS |
1854 | @tindex window-size-fixed |
1855 | @defvar window-size-fixed | |
1856 | If this variable is non-@code{nil}, in any given buffer, | |
1857 | then the size of any window displaying the buffer remains fixed | |
1858 | unless you explicitly change it or Emacs has no other choice. | |
1859 | (This feature is new in Emacs 21.) | |
1860 | ||
1861 | If the value is @code{height}, then only the window's height is fixed; | |
1862 | if the value is @code{width}, then only the window's width is fixed. | |
1863 | Any other non-@code{nil} value fixes both the width and the height. | |
1864 | ||
1865 | The usual way to use this variable is to give it a buffer-local value in | |
1866 | a particular buffer. That way, the windows (but usually there is only | |
1867 | one) displaying that buffer have fixed size. | |
1868 | ||
1869 | Explicit size-change functions such as @code{enlarge-window} | |
1870 | get an error if they would have to change a window size which is fixed. | |
1871 | Therefore, when you want to change the size of such a window, | |
1872 | you should bind @code{window-size-fixed} to @code{nil}, like this: | |
1873 | ||
1874 | @example | |
1875 | (let ((window-size-fixed nil)) | |
1876 | (enlarge-window 10)) | |
1877 | @end example | |
1878 | ||
1879 | Note that changing the frame size will change the size of a | |
1880 | fixed-size window, if there is no other alternative. | |
1881 | @end defvar | |
1882 | ||
b1b12a8e | 1883 | @cindex minimum window size |
c638661f | 1884 | The following two variables constrain the window-size-changing |
b1b12a8e RS |
1885 | functions to a minimum height and width. |
1886 | ||
1887 | @defopt window-min-height | |
1888 | The value of this variable determines how short a window may become | |
1889 | before it is automatically deleted. Making a window smaller than | |
1890 | @code{window-min-height} automatically deletes it, and no window may be | |
1891 | created shorter than this. The absolute minimum height is two (allowing | |
1892 | one line for the mode line, and one line for the buffer display). | |
c638661f | 1893 | Actions that change window sizes reset this variable to two if it is |
b1b12a8e RS |
1894 | less than two. The default value is 4. |
1895 | @end defopt | |
1896 | ||
1897 | @defopt window-min-width | |
1898 | The value of this variable determines how narrow a window may become | |
1911e6e5 | 1899 | before it is automatically deleted. Making a window smaller than |
b1b12a8e RS |
1900 | @code{window-min-width} automatically deletes it, and no window may be |
1901 | created narrower than this. The absolute minimum width is one; any | |
1902 | value below that is ignored. The default value is 10. | |
1903 | @end defopt | |
1904 | ||
1905 | @node Coordinates and Windows | |
1906 | @section Coordinates and Windows | |
1907 | ||
c638661f | 1908 | This section describes how to relate screen coordinates to windows. |
b1b12a8e RS |
1909 | |
1910 | @defun window-at x y &optional frame | |
1911 | This function returns the window containing the specified cursor | |
1912 | position in the frame @var{frame}. The coordinates @var{x} and @var{y} | |
1913 | are measured in characters and count from the top left corner of the | |
1914 | frame. If they are out of range, @code{window-at} returns @code{nil}. | |
1915 | ||
1916 | If you omit @var{frame}, the selected frame is used. | |
1917 | @end defun | |
1918 | ||
1919 | @defun coordinates-in-window-p coordinates window | |
1920 | This function checks whether a particular frame position falls within | |
1921 | the window @var{window}. | |
1922 | ||
969fe9b5 RS |
1923 | The argument @var{coordinates} is a cons cell of the form @code{(@var{x} |
1924 | . @var{y})}. The coordinates @var{x} and @var{y} are measured in | |
1925 | characters, and count from the top left corner of the screen or frame. | |
b1b12a8e | 1926 | |
f9f59935 RS |
1927 | The value returned by @code{coordinates-in-window-p} is non-@code{nil} |
1928 | if the coordinates are inside @var{window}. The value also indicates | |
1929 | what part of the window the position is in, as follows: | |
b1b12a8e RS |
1930 | |
1931 | @table @code | |
1932 | @item (@var{relx} . @var{rely}) | |
1933 | The coordinates are inside @var{window}. The numbers @var{relx} and | |
1934 | @var{rely} are the equivalent window-relative coordinates for the | |
1935 | specified position, counting from 0 at the top left corner of the | |
1936 | window. | |
1937 | ||
1938 | @item mode-line | |
1939 | The coordinates are in the mode line of @var{window}. | |
1940 | ||
8241495d RS |
1941 | @item header-line |
1942 | The coordinates are in the header line of @var{window}. | |
1943 | ||
1944 | @item vertical-line | |
b1b12a8e | 1945 | The coordinates are in the vertical line between @var{window} and its |
3c29caa8 | 1946 | neighbor to the right. This value occurs only if the window doesn't |
b1b12a8e | 1947 | have a scroll bar; positions in a scroll bar are considered outside the |
8241495d | 1948 | window for these purposes. |
b1b12a8e RS |
1949 | |
1950 | @item nil | |
1951 | The coordinates are not in any part of @var{window}. | |
1952 | @end table | |
1953 | ||
1954 | The function @code{coordinates-in-window-p} does not require a frame as | |
1955 | argument because it always uses the frame that @var{window} is on. | |
1956 | @end defun | |
1957 | ||
1958 | @node Window Configurations | |
1959 | @section Window Configurations | |
1960 | @cindex window configurations | |
1961 | @cindex saving window information | |
1962 | ||
f9f59935 | 1963 | A @dfn{window configuration} records the entire layout of one |
b1b12a8e RS |
1964 | frame---all windows, their sizes, which buffers they contain, what part |
1965 | of each buffer is displayed, and the values of point and the mark. You | |
1966 | can bring back an entire previous layout by restoring a window | |
1967 | configuration previously saved. | |
1968 | ||
1969 | If you want to record all frames instead of just one, use a frame | |
1970 | configuration instead of a window configuration. @xref{Frame | |
1971 | Configurations}. | |
1972 | ||
8241495d RS |
1973 | @defun current-window-configuration &optional frame |
1974 | This function returns a new object representing @var{frame}'s | |
f9f59935 RS |
1975 | current window configuration, including the number of windows, their |
1976 | sizes and current buffers, which window is the selected window, and for | |
1977 | each window the displayed buffer, the display-start position, and the | |
969fe9b5 RS |
1978 | positions of point and the mark. It also includes the values of |
1979 | @code{window-min-height}, @code{window-min-width} and | |
1980 | @code{minibuffer-scroll-window}. An exception is made for point in the | |
f9f59935 | 1981 | current buffer, whose value is not saved. |
8241495d RS |
1982 | |
1983 | If @var{frame} is omitted, the selected frame is used. | |
b1b12a8e RS |
1984 | @end defun |
1985 | ||
1986 | @defun set-window-configuration configuration | |
f9f59935 | 1987 | This function restores the configuration of windows and buffers as |
8241495d RS |
1988 | specified by @var{configuration}, for the frame that @var{configuration} |
1989 | was created for. | |
1990 | ||
1991 | The argument @var{configuration} must be a value that was previously | |
1992 | returned by @code{current-window-configuration}. This configuration is | |
1993 | restored in the frame from which @var{configuration} was made, whether | |
1994 | that frame is selected or not. This always counts as a window size | |
1995 | change and triggers execution of the @code{window-size-change-functions} | |
969fe9b5 RS |
1996 | (@pxref{Window Hooks}), because @code{set-window-configuration} doesn't |
1997 | know how to tell whether the new configuration actually differs from the | |
1998 | old one. | |
1999 | ||
2000 | If the frame which @var{configuration} was saved from is dead, all this | |
2001 | function does is restore the three variables @code{window-min-height}, | |
2002 | @code{window-min-width} and @code{minibuffer-scroll-window}. | |
bfe721d1 | 2003 | |
b1b12a8e RS |
2004 | Here is a way of using this function to get the same effect |
2005 | as @code{save-window-excursion}: | |
2006 | ||
2007 | @example | |
2008 | @group | |
2009 | (let ((config (current-window-configuration))) | |
2010 | (unwind-protect | |
2011 | (progn (split-window-vertically nil) | |
2012 | @dots{}) | |
2013 | (set-window-configuration config))) | |
2014 | @end group | |
2015 | @end example | |
2016 | @end defun | |
2017 | ||
2018 | @defspec save-window-excursion forms@dots{} | |
2019 | This special form records the window configuration, executes @var{forms} | |
2020 | in sequence, then restores the earlier window configuration. The window | |
2021 | configuration includes the value of point and the portion of the buffer | |
c638661f | 2022 | that is visible. It also includes the choice of selected window. |
b1b12a8e | 2023 | However, it does not include the value of point in the current buffer; |
f9f59935 | 2024 | use @code{save-excursion} also, if you wish to preserve that. |
b1b12a8e | 2025 | |
bfe721d1 KH |
2026 | Don't use this construct when @code{save-selected-window} is all you need. |
2027 | ||
2028 | Exit from @code{save-window-excursion} always triggers execution of the | |
2029 | @code{window-size-change-functions}. (It doesn't know how to tell | |
2030 | whether the restored configuration actually differs from the one in | |
2031 | effect at the end of the @var{forms}.) | |
2032 | ||
b1b12a8e RS |
2033 | The return value is the value of the final form in @var{forms}. |
2034 | For example: | |
2035 | ||
2036 | @example | |
2037 | @group | |
2038 | (split-window) | |
2039 | @result{} #<window 25 on control.texi> | |
2040 | @end group | |
2041 | @group | |
2042 | (setq w (selected-window)) | |
2043 | @result{} #<window 19 on control.texi> | |
2044 | @end group | |
2045 | @group | |
2046 | (save-window-excursion | |
2047 | (delete-other-windows w) | |
2048 | (switch-to-buffer "foo") | |
2049 | 'do-something) | |
2050 | @result{} do-something | |
2051 | ;; @r{The screen is now split again.} | |
2052 | @end group | |
2053 | @end example | |
2054 | @end defspec | |
2055 | ||
2056 | @defun window-configuration-p object | |
2057 | This function returns @code{t} if @var{object} is a window configuration. | |
969fe9b5 RS |
2058 | @end defun |
2059 | ||
2060 | @defun compare-window-configurations config1 config2 | |
2061 | This function compares two window configurations as regards the | |
2062 | structure of windows, but ignores the values of point and mark and the | |
2063 | saved scrolling positions---it can return @code{t} even if those | |
2064 | aspects differ. | |
2065 | ||
2066 | The function @code{equal} can also compare two window configurations; it | |
2067 | regards configurations as unequal if they differ in any respect, even a | |
2068 | saved point or mark. | |
b1b12a8e RS |
2069 | @end defun |
2070 | ||
2071 | Primitives to look inside of window configurations would make sense, | |
2072 | but none are implemented. It is not clear they are useful enough to be | |
2073 | worth implementing. | |
f9f59935 RS |
2074 | |
2075 | @node Window Hooks | |
2076 | @section Hooks for Window Scrolling and Changes | |
2077 | ||
2078 | This section describes how a Lisp program can take action whenever a | |
2079 | window displays a different part of its buffer or a different buffer. | |
2080 | There are three actions that can change this: scrolling the window, | |
2081 | switching buffers in the window, and changing the size of the window. | |
2082 | The first two actions run @code{window-scroll-functions}; the last runs | |
2083 | @code{window-size-change-functions}. The paradigmatic use of these | |
969fe9b5 RS |
2084 | hooks is in the implementation of Lazy Lock mode; see @ref{Support |
2085 | Modes, Lazy Lock, Font Lock Support Modes, emacs, The GNU Emacs Manual}. | |
f9f59935 RS |
2086 | |
2087 | @defvar window-scroll-functions | |
2088 | This variable holds a list of functions that Emacs should call before | |
2089 | redisplaying a window with scrolling. It is not a normal hook, because | |
2090 | each function is called with two arguments: the window, and its new | |
2091 | display-start position. | |
2092 | ||
2093 | Displaying a different buffer in the window also runs these functions. | |
2094 | ||
1911e6e5 RS |
2095 | These functions must be careful in using @code{window-end} |
2096 | (@pxref{Window Start}); if you need an up-to-date value, you must use | |
2097 | the @var{update} argument to ensure you get it. | |
f9f59935 RS |
2098 | @end defvar |
2099 | ||
2100 | @defvar window-size-change-functions | |
2101 | This variable holds a list of functions to be called if the size of any | |
2102 | window changes for any reason. The functions are called just once per | |
2103 | redisplay, and just once for each frame on which size changes have | |
2104 | occurred. | |
2105 | ||
2106 | Each function receives the frame as its sole argument. There is no | |
2107 | direct way to find out which windows on that frame have changed size, or | |
2108 | precisely how. However, if a size-change function records, at each | |
2109 | call, the existing windows and their sizes, it can also compare the | |
2110 | present sizes and the previous sizes. | |
2111 | ||
2112 | Creating or deleting windows counts as a size change, and therefore | |
2113 | causes these functions to be called. Changing the frame size also | |
2114 | counts, because it changes the sizes of the existing windows. | |
2115 | ||
2116 | It is not a good idea to use @code{save-window-excursion} (@pxref{Window | |
2117 | Configurations}) in these functions, because that always counts as a | |
2118 | size change, and it would cause these functions to be called over and | |
2119 | over. In most cases, @code{save-selected-window} (@pxref{Selecting | |
2120 | Windows}) is what you need here. | |
2121 | @end defvar | |
2122 | ||
f9f59935 | 2123 | @defvar redisplay-end-trigger-functions |
1911e6e5 | 2124 | This abnormal hook is run whenever redisplay in a window uses text that |
f9f59935 RS |
2125 | extends past a specified end trigger position. You set the end trigger |
2126 | position with the function @code{set-window-redisplay-end-trigger}. The | |
2127 | functions are called with two arguments: the window, and the end trigger | |
2128 | position. Storing @code{nil} for the end trigger position turns off the | |
2129 | feature, and the trigger value is automatically reset to @code{nil} just | |
2130 | after the hook is run. | |
2131 | @end defvar | |
2132 | ||
f9f59935 RS |
2133 | @defun set-window-redisplay-end-trigger window position |
2134 | This function sets @var{window}'s end trigger position at | |
2135 | @var{position}. | |
2136 | @end defun | |
2137 | ||
8241495d | 2138 | @defun window-redisplay-end-trigger &optional window |
f9f59935 RS |
2139 | This function returns @var{window}'s current end trigger position. |
2140 | @end defun | |
2141 | ||
f9f59935 RS |
2142 | @defvar window-configuration-change-hook |
2143 | A normal hook that is run every time you change the window configuration | |
2144 | of an existing frame. This includes splitting or deleting windows, | |
2145 | changing the sizes of windows, or displaying a different buffer in a | |
2146 | window. The frame whose window configuration has changed is the | |
2147 | selected frame when this hook runs. | |
2148 | @end defvar |