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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 | |
926a5166 | 173 | lines high by 80 columns wide; then it splits the window. |
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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 | ||
926a5166 | 215 | Next, split the top window horizontally: |
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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 |
926a5166 | 237 | Now the screen looks like this: |
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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} |
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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.) | |
b1b12a8e RS |
266 | @end deffn |
267 | ||
2468d0c0 | 268 | @deffn Command split-window-horizontally &optional size |
b1b12a8e RS |
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 |
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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. | |
b1b12a8e RS |
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} | |
121af256 EZ |
422 | in sequence, then restores the earlier selected window (unless that |
423 | window is no longer alive). | |
3c29caa8 DH |
424 | |
425 | This macro does not save or restore anything about the sizes, arrangement | |
bfe721d1 | 426 | or contents of windows; therefore, if the @var{forms} change them, |
3c29caa8 DH |
427 | the change persists. |
428 | ||
429 | Each frame, at any time, has a window selected within the frame. This | |
969fe9b5 | 430 | macro saves only @emph{the} selected window; it does not save anything |
3c29caa8 DH |
431 | about other frames. If the @var{forms} select some other frame and |
432 | alter the window selected within it, the change persists. | |
bfe721d1 KH |
433 | @end defmac |
434 | ||
b1b12a8e RS |
435 | @cindex finding windows |
436 | The following functions choose one of the windows on the screen, | |
437 | offering various criteria for the choice. | |
438 | ||
439 | @defun get-lru-window &optional frame | |
440 | This function returns the window least recently ``used'' (that is, | |
441 | selected). The selected window is always the most recently used window. | |
442 | ||
443 | The selected window can be the least recently used window if it is the | |
444 | only window. A newly created window becomes the least recently used | |
445 | window until it is selected. A minibuffer window is never a candidate. | |
446 | ||
c638661f | 447 | The argument @var{frame} controls which windows are considered. |
b1b12a8e RS |
448 | |
449 | @itemize @bullet | |
450 | @item | |
451 | If it is @code{nil}, consider windows on the selected frame. | |
452 | @item | |
453 | If it is @code{t}, consider windows on all frames. | |
454 | @item | |
455 | If it is @code{visible}, consider windows on all visible frames. | |
456 | @item | |
bfe721d1 KH |
457 | If it is 0, consider windows on all visible or iconified frames. |
458 | @item | |
b1b12a8e RS |
459 | If it is a frame, consider windows on that frame. |
460 | @end itemize | |
461 | @end defun | |
462 | ||
463 | @defun get-largest-window &optional frame | |
464 | This function returns the window with the largest area (height times | |
465 | width). If there are no side-by-side windows, then this is the window | |
466 | with the most lines. A minibuffer window is never a candidate. | |
467 | ||
468 | If there are two windows of the same size, then the function returns | |
c638661f | 469 | the window that is first in the cyclic ordering of windows (see |
b1b12a8e RS |
470 | following section), starting from the selected window. |
471 | ||
1911e6e5 RS |
472 | The argument @var{frame} controls which set of windows to |
473 | consider. See @code{get-lru-window}, above. | |
b1b12a8e RS |
474 | @end defun |
475 | ||
1e8ca3a9 EZ |
476 | @cindex window that satisfies a predicate |
477 | @cindex conditional selection of windows | |
478 | @defun get-window-with-predicate predicate &optional minibuf all-frames default | |
479 | This function returns a window satisfying @var{predicate}. It cycles | |
480 | through all visible windows using @code{walk-windows} (@pxref{Cyclic | |
481 | Window Ordering}), calling @var{predicate} on each one one of them | |
482 | with that window as its argument. The function returns the first | |
483 | window for which @var{predicate} returns a non-@code{nil} value; if | |
484 | that never happens, it returns @var{default}. | |
485 | ||
486 | The optional arguments @var{minibuf} and @var{all-frames} specify the | |
487 | set of windows to include in the scan. See the description of | |
488 | @code{next-window} in @ref{Cyclic Window Ordering}, for details. | |
489 | @end defun | |
490 | ||
b1b12a8e RS |
491 | @node Cyclic Window Ordering |
492 | @comment node-name, next, previous, up | |
493 | @section Cyclic Ordering of Windows | |
494 | @cindex cyclic ordering of windows | |
495 | @cindex ordering of windows, cyclic | |
3c29caa8 | 496 | @cindex window ordering, cyclic |
b1b12a8e RS |
497 | |
498 | When you use the command @kbd{C-x o} (@code{other-window}) to select | |
499 | the next window, it moves through all the windows on the screen in a | |
500 | specific cyclic order. For any given configuration of windows, this | |
501 | order never varies. It is called the @dfn{cyclic ordering of windows}. | |
502 | ||
503 | This ordering generally goes from top to bottom, and from left to | |
504 | right. But it may go down first or go right first, depending on the | |
505 | order in which the windows were split. | |
506 | ||
507 | If the first split was vertical (into windows one above each other), | |
508 | and then the subwindows were split horizontally, then the ordering is | |
509 | left to right in the top of the frame, and then left to right in the | |
510 | next lower part of the frame, and so on. If the first split was | |
511 | horizontal, the ordering is top to bottom in the left part, and so on. | |
512 | In general, within each set of siblings at any level in the window tree, | |
513 | the order is left to right, or top to bottom. | |
514 | ||
515 | @defun next-window &optional window minibuf all-frames | |
516 | @cindex minibuffer window | |
517 | This function returns the window following @var{window} in the cyclic | |
c638661f RS |
518 | ordering of windows. This is the window that @kbd{C-x o} would select |
519 | if typed when @var{window} is selected. If @var{window} is the only | |
b1b12a8e RS |
520 | window visible, then this function returns @var{window}. If omitted, |
521 | @var{window} defaults to the selected window. | |
522 | ||
523 | The value of the argument @var{minibuf} determines whether the | |
524 | minibuffer is included in the window order. Normally, when | |
525 | @var{minibuf} is @code{nil}, the minibuffer is included if it is | |
526 | currently active; this is the behavior of @kbd{C-x o}. (The minibuffer | |
527 | window is active while the minibuffer is in use. @xref{Minibuffers}.) | |
528 | ||
529 | If @var{minibuf} is @code{t}, then the cyclic ordering includes the | |
530 | minibuffer window even if it is not active. | |
531 | ||
532 | If @var{minibuf} is neither @code{t} nor @code{nil}, then the minibuffer | |
533 | window is not included even if it is active. | |
534 | ||
535 | The argument @var{all-frames} specifies which frames to consider. Here | |
536 | are the possible values and their meanings: | |
537 | ||
538 | @table @asis | |
539 | @item @code{nil} | |
540 | Consider all the windows in @var{window}'s frame, plus the minibuffer | |
541 | used by that frame even if it lies in some other frame. | |
542 | ||
543 | @item @code{t} | |
544 | Consider all windows in all existing frames. | |
545 | ||
546 | @item @code{visible} | |
547 | Consider all windows in all visible frames. (To get useful results, you | |
548 | must ensure @var{window} is in a visible frame.) | |
549 | ||
83abd543 | 550 | @item 0 |
bfe721d1 KH |
551 | Consider all windows in all visible or iconified frames. |
552 | ||
b1b12a8e RS |
553 | @item anything else |
554 | Consider precisely the windows in @var{window}'s frame, and no others. | |
555 | @end table | |
556 | ||
3c29caa8 | 557 | This example assumes there are two windows, both displaying the |
b1b12a8e RS |
558 | buffer @samp{windows.texi}: |
559 | ||
560 | @example | |
561 | @group | |
562 | (selected-window) | |
563 | @result{} #<window 56 on windows.texi> | |
564 | @end group | |
565 | @group | |
566 | (next-window (selected-window)) | |
567 | @result{} #<window 52 on windows.texi> | |
568 | @end group | |
569 | @group | |
570 | (next-window (next-window (selected-window))) | |
571 | @result{} #<window 56 on windows.texi> | |
572 | @end group | |
573 | @end example | |
574 | @end defun | |
575 | ||
576 | @defun previous-window &optional window minibuf all-frames | |
577 | This function returns the window preceding @var{window} in the cyclic | |
578 | ordering of windows. The other arguments specify which windows to | |
579 | include in the cycle, as in @code{next-window}. | |
580 | @end defun | |
581 | ||
8241495d | 582 | @deffn Command other-window count &optional all-frames |
b1b12a8e | 583 | This function selects the @var{count}th following window in the cyclic |
969fe9b5 RS |
584 | order. If count is negative, then it moves back @minus{}@var{count} |
585 | windows in the cycle, rather than forward. It returns @code{nil}. | |
b1b12a8e | 586 | |
75708135 | 587 | The argument @var{all-frames} has the same meaning as in |
8241495d RS |
588 | @code{next-window}, but the @var{minibuf} argument of @code{next-window} |
589 | is always effectively @code{nil}. | |
590 | ||
b1b12a8e RS |
591 | In an interactive call, @var{count} is the numeric prefix argument. |
592 | @end deffn | |
593 | ||
594 | @c Emacs 19 feature | |
595 | @defun walk-windows proc &optional minibuf all-frames | |
596 | This function cycles through all windows, calling @code{proc} | |
597 | once for each window with the window as its sole argument. | |
598 | ||
599 | The optional arguments @var{minibuf} and @var{all-frames} specify the | |
600 | set of windows to include in the scan. See @code{next-window}, above, | |
601 | for details. | |
602 | @end defun | |
603 | ||
e258eedc GM |
604 | @defun window-list &optional frame minibuf window |
605 | This function returns a list of the windows on @var{frame}, starting | |
606 | with @var{window}. If @var{frame} is @code{nil} or omitted, the | |
607 | selected frame is used instead; if @var{window} is @code{nil} or | |
608 | omitted, the selected window is used instead. | |
609 | ||
610 | The value of @var{minibuf} determines if the minibuffer window will be | |
611 | included in the result list. If @var{minibuf} is @code{t}, the | |
612 | minibuffer window will be included, even if it isn't active. If | |
429994d8 | 613 | @var{minibuf} is @code{nil} or omitted, the minibuffer window will |
e258eedc GM |
614 | only be included in the list if it is active. If @var{minibuf} is |
615 | neither @code{nil} nor @code{t}, the minibuffer window is not | |
616 | included, whether or not it is active. | |
429994d8 | 617 | @end defun |
e258eedc | 618 | |
b1b12a8e RS |
619 | @node Buffers and Windows |
620 | @section Buffers and Windows | |
621 | @cindex examining windows | |
622 | @cindex windows, controlling precisely | |
623 | @cindex buffers, controlled in windows | |
624 | ||
625 | This section describes low-level functions to examine windows or to | |
626 | display buffers in windows in a precisely controlled fashion. | |
627 | @iftex | |
628 | See the following section for | |
629 | @end iftex | |
37680279 | 630 | @ifnottex |
b1b12a8e | 631 | @xref{Displaying Buffers}, for |
37680279 | 632 | @end ifnottex |
b1b12a8e RS |
633 | related functions that find a window to use and specify a buffer for it. |
634 | The functions described there are easier to use than these, but they | |
635 | employ heuristics in choosing or creating a window; use these functions | |
636 | when you need complete control. | |
637 | ||
638 | @defun set-window-buffer window buffer-or-name | |
639 | This function makes @var{window} display @var{buffer-or-name} as its | |
a9f0a989 RS |
640 | contents. It returns @code{nil}. This is the fundamental primitive |
641 | for changing which buffer is displayed in a window, and all ways | |
642 | of doing that call this function. | |
b1b12a8e RS |
643 | |
644 | @example | |
645 | @group | |
646 | (set-window-buffer (selected-window) "foo") | |
647 | @result{} nil | |
648 | @end group | |
649 | @end example | |
650 | @end defun | |
651 | ||
652 | @defun window-buffer &optional window | |
653 | This function returns the buffer that @var{window} is displaying. If | |
654 | @var{window} is omitted, this function returns the buffer for the | |
655 | selected window. | |
656 | ||
657 | @example | |
658 | @group | |
659 | (window-buffer) | |
660 | @result{} #<buffer windows.texi> | |
661 | @end group | |
662 | @end example | |
663 | @end defun | |
664 | ||
665 | @defun get-buffer-window buffer-or-name &optional all-frames | |
666 | This function returns a window currently displaying | |
667 | @var{buffer-or-name}, or @code{nil} if there is none. If there are | |
668 | several such windows, then the function returns the first one in the | |
669 | cyclic ordering of windows, starting from the selected window. | |
670 | @xref{Cyclic Window Ordering}. | |
671 | ||
672 | The argument @var{all-frames} controls which windows to consider. | |
673 | ||
674 | @itemize @bullet | |
675 | @item | |
676 | If it is @code{nil}, consider windows on the selected frame. | |
677 | @item | |
678 | If it is @code{t}, consider windows on all frames. | |
679 | @item | |
680 | If it is @code{visible}, consider windows on all visible frames. | |
681 | @item | |
bfe721d1 KH |
682 | If it is 0, consider windows on all visible or iconified frames. |
683 | @item | |
b1b12a8e RS |
684 | If it is a frame, consider windows on that frame. |
685 | @end itemize | |
686 | @end defun | |
687 | ||
3c29caa8 DH |
688 | @defun get-buffer-window-list buffer-or-name &optional minibuf all-frames |
689 | This function returns a list of all the windows currently displaying | |
690 | @var{buffer-or-name}. | |
691 | ||
692 | The two optional arguments work like the optional arguments of | |
693 | @code{next-window} (@pxref{Cyclic Window Ordering}); they are @emph{not} | |
694 | like the single optional argument of @code{get-buffer-window}. Perhaps | |
695 | we should change @code{get-buffer-window} in the future to make it | |
696 | compatible with the other functions. | |
697 | ||
698 | The argument @var{all-frames} controls which windows to consider. | |
699 | ||
700 | @itemize @bullet | |
701 | @item | |
702 | If it is @code{nil}, consider windows on the selected frame. | |
703 | @item | |
704 | If it is @code{t}, consider windows on all frames. | |
705 | @item | |
706 | If it is @code{visible}, consider windows on all visible frames. | |
707 | @item | |
708 | If it is 0, consider windows on all visible or iconified frames. | |
709 | @item | |
710 | If it is a frame, consider windows on that frame. | |
711 | @end itemize | |
712 | @end defun | |
713 | ||
a9f0a989 | 714 | @defvar buffer-display-time |
a9f0a989 RS |
715 | This variable records the time at which a buffer was last made visible |
716 | in a window. It is always local in each buffer; each time | |
717 | @code{set-window-buffer} is called, it sets this variable to | |
718 | @code{(current-time)} in the specified buffer (@pxref{Time of Day}). | |
1911e6e5 | 719 | When a buffer is first created, @code{buffer-display-time} starts out |
a9f0a989 RS |
720 | with the value @code{nil}. |
721 | @end defvar | |
722 | ||
b1b12a8e RS |
723 | @node Displaying Buffers |
724 | @section Displaying Buffers in Windows | |
725 | @cindex switching to a buffer | |
726 | @cindex displaying a buffer | |
727 | ||
728 | In this section we describe convenient functions that choose a window | |
729 | automatically and use it to display a specified buffer. These functions | |
730 | can also split an existing window in certain circumstances. We also | |
731 | describe variables that parameterize the heuristics used for choosing a | |
732 | window. | |
733 | @iftex | |
734 | See the preceding section for | |
735 | @end iftex | |
37680279 | 736 | @ifnottex |
b1b12a8e | 737 | @xref{Buffers and Windows}, for |
37680279 | 738 | @end ifnottex |
a9f0a989 RS |
739 | low-level functions that give you more precise control. All of these |
740 | functions work by calling @code{set-window-buffer}. | |
b1b12a8e RS |
741 | |
742 | Do not use the functions in this section in order to make a buffer | |
743 | current so that a Lisp program can access or modify it; they are too | |
744 | drastic for that purpose, since they change the display of buffers in | |
969fe9b5 | 745 | windows, which would be gratuitous and surprise the user. Instead, use |
1911e6e5 RS |
746 | @code{set-buffer} and @code{save-current-buffer} (@pxref{Current |
747 | Buffer}), which designate buffers as current for programmed access | |
748 | without affecting the display of buffers in windows. | |
b1b12a8e RS |
749 | |
750 | @deffn Command switch-to-buffer buffer-or-name &optional norecord | |
751 | This function makes @var{buffer-or-name} the current buffer, and also | |
752 | displays the buffer in the selected window. This means that a human can | |
753 | see the buffer and subsequent keyboard commands will apply to it. | |
754 | Contrast this with @code{set-buffer}, which makes @var{buffer-or-name} | |
755 | the current buffer but does not display it in the selected window. | |
756 | @xref{Current Buffer}. | |
757 | ||
22697dac KH |
758 | If @var{buffer-or-name} does not identify an existing buffer, then a new |
759 | buffer by that name is created. The major mode for the new buffer is | |
760 | set according to the variable @code{default-major-mode}. @xref{Auto | |
761 | Major Mode}. | |
b1b12a8e | 762 | |
969fe9b5 RS |
763 | Normally the specified buffer is put at the front of the buffer list |
764 | (both the selected frame's buffer list and the frame-independent buffer | |
765 | list). This affects the operation of @code{other-buffer}. However, if | |
b1b12a8e RS |
766 | @var{norecord} is non-@code{nil}, this is not done. @xref{The Buffer |
767 | List}. | |
768 | ||
769 | The @code{switch-to-buffer} function is often used interactively, as | |
770 | the binding of @kbd{C-x b}. It is also used frequently in programs. It | |
996d82f8 | 771 | returns the buffer that it switched to. |
b1b12a8e RS |
772 | @end deffn |
773 | ||
f9f59935 | 774 | @deffn Command switch-to-buffer-other-window buffer-or-name &optional norecord |
b1b12a8e RS |
775 | This function makes @var{buffer-or-name} the current buffer and |
776 | displays it in a window not currently selected. It then selects that | |
777 | window. The handling of the buffer is the same as in | |
778 | @code{switch-to-buffer}. | |
779 | ||
c638661f RS |
780 | The currently selected window is absolutely never used to do the job. |
781 | If it is the only window, then it is split to make a distinct window for | |
782 | this purpose. If the selected window is already displaying the buffer, | |
783 | then it continues to do so, but another window is nonetheless found to | |
784 | display it in as well. | |
f9f59935 RS |
785 | |
786 | This function updates the buffer list just like @code{switch-to-buffer} | |
787 | unless @var{norecord} is non-@code{nil}. | |
b1b12a8e RS |
788 | @end deffn |
789 | ||
f9f59935 | 790 | @defun pop-to-buffer buffer-or-name &optional other-window norecord |
b1b12a8e RS |
791 | This function makes @var{buffer-or-name} the current buffer and |
792 | switches to it in some window, preferably not the window previously | |
793 | selected. The ``popped-to'' window becomes the selected window within | |
996d82f8 | 794 | its frame. The return value is the buffer that was switched to. |
b1b12a8e RS |
795 | |
796 | If the variable @code{pop-up-frames} is non-@code{nil}, | |
797 | @code{pop-to-buffer} looks for a window in any visible frame already | |
798 | displaying the buffer; if there is one, it returns that window and makes | |
799 | it be selected within its frame. If there is none, it creates a new | |
800 | frame and displays the buffer in it. | |
801 | ||
802 | If @code{pop-up-frames} is @code{nil}, then @code{pop-to-buffer} | |
803 | operates entirely within the selected frame. (If the selected frame has | |
804 | just a minibuffer, @code{pop-to-buffer} operates within the most | |
805 | recently selected frame that was not just a minibuffer.) | |
806 | ||
807 | If the variable @code{pop-up-windows} is non-@code{nil}, windows may | |
808 | be split to create a new window that is different from the original | |
809 | window. For details, see @ref{Choosing Window}. | |
810 | ||
811 | If @var{other-window} is non-@code{nil}, @code{pop-to-buffer} finds or | |
812 | creates another window even if @var{buffer-or-name} is already visible | |
813 | in the selected window. Thus @var{buffer-or-name} could end up | |
814 | displayed in two windows. On the other hand, if @var{buffer-or-name} is | |
815 | already displayed in the selected window and @var{other-window} is | |
816 | @code{nil}, then the selected window is considered sufficient display | |
817 | for @var{buffer-or-name}, so that nothing needs to be done. | |
818 | ||
bfe721d1 KH |
819 | All the variables that affect @code{display-buffer} affect |
820 | @code{pop-to-buffer} as well. @xref{Choosing Window}. | |
821 | ||
b1b12a8e | 822 | If @var{buffer-or-name} is a string that does not name an existing |
22697dac KH |
823 | buffer, a buffer by that name is created. The major mode for the new |
824 | buffer is set according to the variable @code{default-major-mode}. | |
825 | @xref{Auto Major Mode}. | |
f9f59935 RS |
826 | |
827 | This function updates the buffer list just like @code{switch-to-buffer} | |
828 | unless @var{norecord} is non-@code{nil}. | |
b1b12a8e RS |
829 | @end defun |
830 | ||
bfe721d1 KH |
831 | @deffn Command replace-buffer-in-windows buffer |
832 | This function replaces @var{buffer} with some other buffer in all | |
833 | windows displaying it. The other buffer used is chosen with | |
834 | @code{other-buffer}. In the usual applications of this function, you | |
835 | don't care which other buffer is used; you just want to make sure that | |
836 | @var{buffer} is no longer displayed. | |
837 | ||
838 | This function returns @code{nil}. | |
839 | @end deffn | |
840 | ||
b1b12a8e RS |
841 | @node Choosing Window |
842 | @section Choosing a Window for Display | |
843 | ||
c638661f | 844 | This section describes the basic facility that chooses a window to |
b1b12a8e RS |
845 | display a buffer in---@code{display-buffer}. All the higher-level |
846 | functions and commands use this subroutine. Here we describe how to use | |
847 | @code{display-buffer} and how to customize it. | |
848 | ||
f9f59935 | 849 | @deffn Command display-buffer buffer-or-name &optional not-this-window frame |
b1b12a8e RS |
850 | This command makes @var{buffer-or-name} appear in some window, like |
851 | @code{pop-to-buffer}, but it does not select that window and does not | |
852 | make the buffer current. The identity of the selected window is | |
853 | unaltered by this function. | |
854 | ||
855 | If @var{not-this-window} is non-@code{nil}, it means to display the | |
856 | specified buffer in a window other than the selected one, even if it is | |
857 | already on display in the selected window. This can cause the buffer to | |
858 | appear in two windows at once. Otherwise, if @var{buffer-or-name} is | |
859 | already being displayed in any window, that is good enough, so this | |
860 | function does nothing. | |
861 | ||
862 | @code{display-buffer} returns the window chosen to display | |
863 | @var{buffer-or-name}. | |
864 | ||
f9f59935 | 865 | If the argument @var{frame} is non-@code{nil}, it specifies which frames |
1911e6e5 RS |
866 | to check when deciding whether the buffer is already displayed. If the |
867 | buffer is already displayed in some window on one of these frames, | |
868 | @code{display-buffer} simply returns that window. Here are the possible | |
869 | values of @var{frame}: | |
870 | ||
871 | @itemize @bullet | |
872 | @item | |
873 | If it is @code{nil}, consider windows on the selected frame. | |
874 | @item | |
875 | If it is @code{t}, consider windows on all frames. | |
876 | @item | |
877 | If it is @code{visible}, consider windows on all visible frames. | |
878 | @item | |
879 | If it is 0, consider windows on all visible or iconified frames. | |
880 | @item | |
881 | If it is a frame, consider windows on that frame. | |
882 | @end itemize | |
f9f59935 | 883 | |
b1b12a8e RS |
884 | Precisely how @code{display-buffer} finds or creates a window depends on |
885 | the variables described below. | |
886 | @end deffn | |
887 | ||
704bdba1 GM |
888 | @defopt display-buffer-reuse-frames |
889 | If this variable is non-@code{nil}, @code{display-buffer} searches | |
890 | existing frames for a window displaying the buffer. If the buffer is | |
891 | already displayed in a window in some frame, @code{display-buffer} makes | |
892 | the frame visible and raises it, to use that window. If the buffer is | |
893 | not already displayed, or if @code{display-buffer-reuse-frames} is | |
894 | @code{nil}, @code{display-buffer}'s behavior is determined by other | |
895 | variables, described below. | |
896 | @end defopt | |
897 | ||
b1b12a8e RS |
898 | @defopt pop-up-windows |
899 | This variable controls whether @code{display-buffer} makes new windows. | |
900 | If it is non-@code{nil} and there is only one window, then that window | |
901 | is split. If it is @code{nil}, then @code{display-buffer} does not | |
902 | split the single window, but uses it whole. | |
903 | @end defopt | |
904 | ||
905 | @defopt split-height-threshold | |
906 | This variable determines when @code{display-buffer} may split a window, | |
907 | if there are multiple windows. @code{display-buffer} always splits the | |
908 | largest window if it has at least this many lines. If the largest | |
909 | window is not this tall, it is split only if it is the sole window and | |
910 | @code{pop-up-windows} is non-@code{nil}. | |
911 | @end defopt | |
912 | ||
4f0308e1 GM |
913 | @defopt even-window-heights |
914 | This variable determines if @code{display-buffer} should even out window | |
915 | heights if the buffer gets displayed in an existing window, above or | |
916 | beneath another existing window. If @code{even-window-heights} is | |
917 | @code{t}, the default, window heights will be evened out. If | |
918 | @code{even-window-heights} is @code{nil}, the orginal window heights | |
919 | will be left alone. | |
fbd9f276 | 920 | @end defopt |
4f0308e1 | 921 | |
b1b12a8e RS |
922 | @c Emacs 19 feature |
923 | @defopt pop-up-frames | |
924 | This variable controls whether @code{display-buffer} makes new frames. | |
925 | If it is non-@code{nil}, @code{display-buffer} looks for an existing | |
926 | window already displaying the desired buffer, on any visible frame. If | |
927 | it finds one, it returns that window. Otherwise it makes a new frame. | |
928 | The variables @code{pop-up-windows} and @code{split-height-threshold} do | |
929 | not matter if @code{pop-up-frames} is non-@code{nil}. | |
930 | ||
931 | If @code{pop-up-frames} is @code{nil}, then @code{display-buffer} either | |
932 | splits a window or reuses one. | |
933 | ||
934 | @xref{Frames}, for more information. | |
935 | @end defopt | |
936 | ||
937 | @c Emacs 19 feature | |
938 | @defvar pop-up-frame-function | |
939 | This variable specifies how to make a new frame if @code{pop-up-frames} | |
940 | is non-@code{nil}. | |
941 | ||
942 | Its value should be a function of no arguments. When | |
943 | @code{display-buffer} makes a new frame, it does so by calling that | |
944 | function, which should return a frame. The default value of the | |
c638661f | 945 | variable is a function that creates a frame using parameters from |
b1b12a8e RS |
946 | @code{pop-up-frame-alist}. |
947 | @end defvar | |
948 | ||
8241495d | 949 | @defopt pop-up-frame-alist |
b1b12a8e RS |
950 | This variable holds an alist specifying frame parameters used when |
951 | @code{display-buffer} makes a new frame. @xref{Frame Parameters}, for | |
952 | more information about frame parameters. | |
8241495d | 953 | @end defopt |
b1b12a8e | 954 | |
1911e6e5 | 955 | @defopt special-display-buffer-names |
c2264295 RS |
956 | A list of buffer names for buffers that should be displayed specially. |
957 | If the buffer's name is in this list, @code{display-buffer} handles the | |
958 | buffer specially. | |
959 | ||
960 | By default, special display means to give the buffer a dedicated frame. | |
bfe721d1 KH |
961 | |
962 | If an element is a list, instead of a string, then the @sc{car} of the | |
963 | list is the buffer name, and the rest of the list says how to create the | |
964 | frame. There are two possibilities for the rest of the list. It can be | |
965 | an alist, specifying frame parameters, or it can contain a function and | |
966 | arguments to give to it. (The function's first argument is always the | |
967 | buffer to be displayed; the arguments from the list come after that.) | |
1911e6e5 | 968 | @end defopt |
c2264295 | 969 | |
1911e6e5 | 970 | @defopt special-display-regexps |
c2264295 RS |
971 | A list of regular expressions that specify buffers that should be |
972 | displayed specially. If the buffer's name matches any of the regular | |
973 | expressions in this list, @code{display-buffer} handles the buffer | |
974 | specially. | |
975 | ||
976 | By default, special display means to give the buffer a dedicated frame. | |
bfe721d1 KH |
977 | |
978 | If an element is a list, instead of a string, then the @sc{car} of the | |
979 | list is the regular expression, and the rest of the list says how to | |
980 | create the frame. See above, under @code{special-display-buffer-names}. | |
1911e6e5 | 981 | @end defopt |
c2264295 RS |
982 | |
983 | @defvar special-display-function | |
984 | This variable holds the function to call to display a buffer specially. | |
985 | It receives the buffer as an argument, and should return the window in | |
986 | which it is displayed. | |
987 | ||
988 | The default value of this variable is | |
989 | @code{special-display-popup-frame}. | |
990 | @end defvar | |
991 | ||
8241495d | 992 | @defun special-display-popup-frame buffer &rest args |
c2264295 RS |
993 | This function makes @var{buffer} visible in a frame of its own. If |
994 | @var{buffer} is already displayed in a window in some frame, it makes | |
995 | the frame visible and raises it, to use that window. Otherwise, it | |
996 | creates a frame that will be dedicated to @var{buffer}. | |
c638661f | 997 | |
8241495d RS |
998 | If @var{args} is an alist, it specifies frame parameters for the new |
999 | frame. | |
1000 | ||
1001 | If @var{args} is a list whose @sc{car} is a symbol, then @code{(car | |
1002 | @var{args})} is called as a function to actually create and set up the | |
1003 | frame; it is called with @var{buffer} as first argument, and @code{(cdr | |
1004 | @var{args})} as additional arguments. | |
1005 | ||
1006 | This function always uses an existing window displaying @var{buffer}, | |
1007 | whether or not it is in a frame of its own; but if you set up the above | |
1008 | variables in your init file, before @var{buffer} was created, then | |
1009 | presumably the window was previously made by this function. | |
c2264295 RS |
1010 | @end defun |
1011 | ||
1012 | @defopt special-display-frame-alist | |
1013 | This variable holds frame parameters for | |
1014 | @code{special-display-popup-frame} to use when it creates a frame. | |
1015 | @end defopt | |
1016 | ||
864bd34b | 1017 | @defopt same-window-buffer-names |
bfe721d1 KH |
1018 | A list of buffer names for buffers that should be displayed in the |
1019 | selected window. If the buffer's name is in this list, | |
1020 | @code{display-buffer} handles the buffer by switching to it in the | |
1021 | selected window. | |
864bd34b | 1022 | @end defopt |
bfe721d1 | 1023 | |
864bd34b | 1024 | @defopt same-window-regexps |
bfe721d1 KH |
1025 | A list of regular expressions that specify buffers that should be |
1026 | displayed in the selected window. If the buffer's name matches any of | |
1027 | the regular expressions in this list, @code{display-buffer} handles the | |
1028 | buffer by switching to it in the selected window. | |
864bd34b | 1029 | @end defopt |
bfe721d1 | 1030 | |
b1b12a8e RS |
1031 | @c Emacs 19 feature |
1032 | @defvar display-buffer-function | |
1033 | This variable is the most flexible way to customize the behavior of | |
1034 | @code{display-buffer}. If it is non-@code{nil}, it should be a function | |
1035 | that @code{display-buffer} calls to do the work. The function should | |
1036 | accept two arguments, the same two arguments that @code{display-buffer} | |
1037 | received. It should choose or create a window, display the specified | |
1038 | buffer, and then return the window. | |
1039 | ||
1040 | This hook takes precedence over all the other options and hooks | |
1041 | described above. | |
1042 | @end defvar | |
1043 | ||
1044 | @c Emacs 19 feature | |
1045 | @cindex dedicated window | |
1046 | A window can be marked as ``dedicated'' to its buffer. Then | |
969fe9b5 RS |
1047 | @code{display-buffer} will not try to use that window to display any |
1048 | other buffer. | |
b1b12a8e RS |
1049 | |
1050 | @defun window-dedicated-p window | |
1051 | This function returns @code{t} if @var{window} is marked as dedicated; | |
1052 | otherwise @code{nil}. | |
1053 | @end defun | |
1054 | ||
1055 | @defun set-window-dedicated-p window flag | |
1056 | This function marks @var{window} as dedicated if @var{flag} is | |
1057 | non-@code{nil}, and nondedicated otherwise. | |
1058 | @end defun | |
1059 | ||
1060 | @node Window Point | |
1061 | @section Windows and Point | |
1062 | @cindex window position | |
1063 | @cindex window point | |
1064 | @cindex position in window | |
1065 | @cindex point in window | |
1066 | ||
1067 | Each window has its own value of point, independent of the value of | |
1068 | point in other windows displaying the same buffer. This makes it useful | |
1069 | to have multiple windows showing one buffer. | |
1070 | ||
1071 | @itemize @bullet | |
1072 | @item | |
1073 | The window point is established when a window is first created; it is | |
1074 | initialized from the buffer's point, or from the window point of another | |
1075 | window opened on the buffer if such a window exists. | |
1076 | ||
1077 | @item | |
f9f59935 RS |
1078 | Selecting a window sets the value of point in its buffer from the |
1079 | window's value of point. Conversely, deselecting a window sets the | |
1080 | window's value of point from that of the buffer. Thus, when you switch | |
1081 | between windows that display a given buffer, the point value for the | |
1082 | selected window is in effect in the buffer, while the point values for | |
1083 | the other windows are stored in those windows. | |
b1b12a8e RS |
1084 | |
1085 | @item | |
1086 | As long as the selected window displays the current buffer, the window's | |
1087 | point and the buffer's point always move together; they remain equal. | |
1088 | ||
1089 | @item | |
1090 | @xref{Positions}, for more details on buffer positions. | |
1091 | @end itemize | |
1092 | ||
1093 | As far as the user is concerned, point is where the cursor is, and | |
1094 | when the user switches to another buffer, the cursor jumps to the | |
1095 | position of point in that buffer. | |
1096 | ||
8241495d | 1097 | @defun window-point &optional window |
b1b12a8e RS |
1098 | This function returns the current position of point in @var{window}. |
1099 | For a nonselected window, this is the value point would have (in that | |
8241495d RS |
1100 | window's buffer) if that window were selected. If @var{window} is |
1101 | @code{nil}, the selected window is used. | |
b1b12a8e RS |
1102 | |
1103 | When @var{window} is the selected window and its buffer is also the | |
1104 | current buffer, the value returned is the same as point in that buffer. | |
1105 | ||
1106 | Strictly speaking, it would be more correct to return the | |
1107 | ``top-level'' value of point, outside of any @code{save-excursion} | |
1108 | forms. But that value is hard to find. | |
1109 | @end defun | |
1110 | ||
1111 | @defun set-window-point window position | |
1112 | This function positions point in @var{window} at position | |
1113 | @var{position} in @var{window}'s buffer. | |
1114 | @end defun | |
1115 | ||
1116 | @node Window Start | |
1117 | @section The Window Start Position | |
1118 | ||
1119 | Each window contains a marker used to keep track of a buffer position | |
c638661f | 1120 | that specifies where in the buffer display should start. This position |
b1b12a8e RS |
1121 | is called the @dfn{display-start} position of the window (or just the |
1122 | @dfn{start}). The character after this position is the one that appears | |
1123 | at the upper left corner of the window. It is usually, but not | |
1124 | inevitably, at the beginning of a text line. | |
1125 | ||
1126 | @defun window-start &optional window | |
1127 | @cindex window top line | |
1128 | This function returns the display-start position of window | |
1129 | @var{window}. If @var{window} is @code{nil}, the selected window is | |
3c29caa8 | 1130 | used. For example, |
b1b12a8e RS |
1131 | |
1132 | @example | |
1133 | @group | |
1134 | (window-start) | |
1135 | @result{} 7058 | |
1136 | @end group | |
1137 | @end example | |
1138 | ||
c638661f | 1139 | When you create a window, or display a different buffer in it, the |
b1b12a8e RS |
1140 | display-start position is set to a display-start position recently used |
1141 | for the same buffer, or 1 if the buffer doesn't have any. | |
1142 | ||
ea951766 | 1143 | Redisplay updates the window-start position (if you have not specified |
8241495d RS |
1144 | it explicitly since the previous redisplay)---for example, to make sure |
1145 | point appears on the screen. Nothing except redisplay automatically | |
1146 | changes the window-start position; if you move point, do not expect the | |
1147 | window-start position to change in response until after the next | |
1148 | redisplay. | |
ea951766 RS |
1149 | |
1150 | For a realistic example of using @code{window-start}, see the | |
1151 | description of @code{count-lines} in @ref{Text Lines}. | |
b1b12a8e RS |
1152 | @end defun |
1153 | ||
969fe9b5 | 1154 | @defun window-end &optional window update |
b1b12a8e RS |
1155 | This function returns the position of the end of the display in window |
1156 | @var{window}. If @var{window} is @code{nil}, the selected window is | |
1157 | used. | |
c638661f | 1158 | |
6c7418db RS |
1159 | Simply changing the buffer text or moving point does not update the |
1160 | value that @code{window-end} returns. The value is updated only when | |
969fe9b5 | 1161 | Emacs redisplays and redisplay completes without being preempted. |
6c7418db | 1162 | |
c638661f | 1163 | If the last redisplay of @var{window} was preempted, and did not finish, |
a283f4a3 | 1164 | Emacs does not know the position of the end of display in that window. |
969fe9b5 | 1165 | In that case, this function returns @code{nil}. |
c638661f | 1166 | |
41448f63 RS |
1167 | If @var{update} is non-@code{nil}, @code{window-end} always returns an |
1168 | up-to-date value for where the window ends, based on the current | |
1169 | @code{window-start} value. If the saved value is valid, | |
1170 | @code{window-end} returns that; otherwise it computes the correct | |
969fe9b5 | 1171 | value by scanning the buffer text. |
41448f63 RS |
1172 | |
1173 | Even if @var{update} is non-@code{nil}, @code{window-end} does not | |
1174 | attempt to scroll the display if point has moved off the screen, the | |
1175 | way real redisplay would do. It does not alter the | |
1176 | @code{window-start} value. In effect, it reports where the displayed | |
1177 | text will end if scrolling is not required. | |
b1b12a8e RS |
1178 | @end defun |
1179 | ||
1180 | @defun set-window-start window position &optional noforce | |
1181 | This function sets the display-start position of @var{window} to | |
c638661f | 1182 | @var{position} in @var{window}'s buffer. It returns @var{position}. |
b1b12a8e RS |
1183 | |
1184 | The display routines insist that the position of point be visible when a | |
1185 | buffer is displayed. Normally, they change the display-start position | |
1186 | (that is, scroll the window) whenever necessary to make point visible. | |
1187 | However, if you specify the start position with this function using | |
1188 | @code{nil} for @var{noforce}, it means you want display to start at | |
1189 | @var{position} even if that would put the location of point off the | |
1190 | screen. If this does place point off screen, the display routines move | |
1191 | point to the left margin on the middle line in the window. | |
1192 | ||
1193 | For example, if point @w{is 1} and you set the start of the window @w{to | |
1194 | 2}, then point would be ``above'' the top of the window. The display | |
1195 | routines will automatically move point if it is still 1 when redisplay | |
1196 | occurs. Here is an example: | |
1197 | ||
1198 | @example | |
1199 | @group | |
1200 | ;; @r{Here is what @samp{foo} looks like before executing} | |
1201 | ;; @r{the @code{set-window-start} expression.} | |
1202 | @end group | |
1203 | ||
1204 | @group | |
1205 | ---------- Buffer: foo ---------- | |
1206 | @point{}This is the contents of buffer foo. | |
1207 | 2 | |
1208 | 3 | |
1209 | 4 | |
1210 | 5 | |
1211 | 6 | |
1212 | ---------- Buffer: foo ---------- | |
1213 | @end group | |
1214 | ||
1215 | @group | |
1216 | (set-window-start | |
1217 | (selected-window) | |
1218 | (1+ (window-start))) | |
1219 | @result{} 2 | |
1220 | @end group | |
1221 | ||
1222 | @group | |
1223 | ;; @r{Here is what @samp{foo} looks like after executing} | |
1224 | ;; @r{the @code{set-window-start} expression.} | |
1225 | ---------- Buffer: foo ---------- | |
1226 | his is the contents of buffer foo. | |
1227 | 2 | |
1228 | 3 | |
1229 | @point{}4 | |
1230 | 5 | |
1231 | 6 | |
1232 | ---------- Buffer: foo ---------- | |
1233 | @end group | |
1234 | @end example | |
1235 | ||
1236 | If @var{noforce} is non-@code{nil}, and @var{position} would place point | |
1237 | off screen at the next redisplay, then redisplay computes a new window-start | |
1238 | position that works well with point, and thus @var{position} is not used. | |
b1b12a8e RS |
1239 | @end defun |
1240 | ||
00480554 | 1241 | @defun pos-visible-in-window-p &optional position window partially |
601bda2e | 1242 | This function returns @code{t} if @var{position} is within the range of |
00480554 MB |
1243 | text currently visible on the screen in @var{window}. It returns |
1244 | @code{nil} if @var{position} is scrolled vertically or horizontally out | |
1245 | of view. Locations that are partially obscured are not considered | |
1246 | visible unless @var{partially} is non-@code{nil}. The argument | |
1247 | @var{position} defaults to the current position of point in | |
1248 | @var{window}; @var{window}, to the selected window. | |
1249 | ||
1250 | Here is an example: | |
b1b12a8e RS |
1251 | |
1252 | @example | |
1253 | @group | |
1254 | (or (pos-visible-in-window-p | |
1255 | (point) (selected-window)) | |
1256 | (recenter 0)) | |
1257 | @end group | |
1258 | @end example | |
b1b12a8e RS |
1259 | @end defun |
1260 | ||
8241495d RS |
1261 | @node Textual Scrolling |
1262 | @section Textual Scrolling | |
1263 | @cindex textual scrolling | |
1264 | @cindex scrolling textually | |
1265 | ||
1266 | @dfn{Textual scrolling} means moving the text up or down though a | |
1267 | window. It works by changing the value of the window's display-start | |
1268 | location. It may also change the value of @code{window-point} to keep | |
1269 | point on the screen. | |
b1b12a8e | 1270 | |
8241495d RS |
1271 | Textual scrolling was formerly called ``vertical scrolling,'' but we |
1272 | changed its name to distinguish it from the new vertical fractional | |
1273 | scrolling feature (@pxref{Vertical Scrolling}). | |
b1b12a8e RS |
1274 | |
1275 | In the commands @code{scroll-up} and @code{scroll-down}, the directions | |
1276 | ``up'' and ``down'' refer to the motion of the text in the buffer at which | |
1277 | you are looking through the window. Imagine that the text is | |
1278 | written on a long roll of paper and that the scrolling commands move the | |
1279 | paper up and down. Thus, if you are looking at text in the middle of a | |
1280 | buffer and repeatedly call @code{scroll-down}, you will eventually see | |
1281 | the beginning of the buffer. | |
1282 | ||
1283 | Some people have urged that the opposite convention be used: they | |
1284 | imagine that the window moves over text that remains in place. Then | |
1285 | ``down'' commands would take you to the end of the buffer. This view is | |
1286 | more consistent with the actual relationship between windows and the | |
1287 | text in the buffer, but it is less like what the user sees. The | |
1288 | position of a window on the terminal does not move, and short scrolling | |
1289 | commands clearly move the text up or down on the screen. We have chosen | |
1290 | names that fit the user's point of view. | |
1291 | ||
8241495d RS |
1292 | The textual scrolling functions (aside from |
1293 | @code{scroll-other-window}) have unpredictable results if the current | |
1294 | buffer is different from the buffer that is displayed in the selected | |
1295 | window. @xref{Current Buffer}. | |
b1b12a8e RS |
1296 | |
1297 | @deffn Command scroll-up &optional count | |
1298 | This function scrolls the text in the selected window upward | |
1299 | @var{count} lines. If @var{count} is negative, scrolling is actually | |
1300 | downward. | |
1301 | ||
1302 | If @var{count} is @code{nil} (or omitted), then the length of scroll | |
1303 | is @code{next-screen-context-lines} lines less than the usable height of | |
1304 | the window (not counting its mode line). | |
1305 | ||
1306 | @code{scroll-up} returns @code{nil}. | |
1307 | @end deffn | |
1308 | ||
1309 | @deffn Command scroll-down &optional count | |
1310 | This function scrolls the text in the selected window downward | |
1311 | @var{count} lines. If @var{count} is negative, scrolling is actually | |
1312 | upward. | |
1313 | ||
1314 | If @var{count} is omitted or @code{nil}, then the length of the scroll | |
1315 | is @code{next-screen-context-lines} lines less than the usable height of | |
c638661f | 1316 | the window (not counting its mode line). |
b1b12a8e RS |
1317 | |
1318 | @code{scroll-down} returns @code{nil}. | |
1319 | @end deffn | |
1320 | ||
1321 | @deffn Command scroll-other-window &optional count | |
1322 | This function scrolls the text in another window upward @var{count} | |
1323 | lines. Negative values of @var{count}, or @code{nil}, are handled | |
1324 | as in @code{scroll-up}. | |
1325 | ||
8241495d RS |
1326 | You can specify which buffer to scroll by setting the variable |
1327 | @code{other-window-scroll-buffer} to a buffer. If that buffer isn't | |
1328 | already displayed, @code{scroll-other-window} displays it in some | |
1329 | window. | |
1330 | ||
1331 | When the selected window is the minibuffer, the next window is normally | |
1332 | the one at the top left corner. You can specify a different window to | |
1333 | scroll, when the minibuffer is selected, by setting the variable | |
b1b12a8e RS |
1334 | @code{minibuffer-scroll-window}. This variable has no effect when any |
1335 | other window is selected. @xref{Minibuffer Misc}. | |
1336 | ||
1337 | When the minibuffer is active, it is the next window if the selected | |
1338 | window is the one at the bottom right corner. In this case, | |
1339 | @code{scroll-other-window} attempts to scroll the minibuffer. If the | |
1340 | minibuffer contains just one line, it has nowhere to scroll to, so the | |
1341 | line reappears after the echo area momentarily displays the message | |
1342 | ``Beginning of buffer''. | |
1343 | @end deffn | |
1344 | ||
1345 | @c Emacs 19 feature | |
1346 | @defvar other-window-scroll-buffer | |
1347 | If this variable is non-@code{nil}, it tells @code{scroll-other-window} | |
1348 | which buffer to scroll. | |
1349 | @end defvar | |
1350 | ||
1911e6e5 RS |
1351 | @defopt scroll-margin |
1352 | This option specifies the size of the scroll margin---a minimum number | |
1353 | of lines between point and the top or bottom of a window. Whenever | |
1354 | point gets within this many lines of the top or bottom of the window, | |
ac7845fd RS |
1355 | redisplay scrolls the text automatically (if possible) to move point |
1356 | out of the margin, closer to the center of the window. | |
1911e6e5 RS |
1357 | @end defopt |
1358 | ||
1911e6e5 | 1359 | @defopt scroll-conservatively |
b1b12a8e | 1360 | This variable controls how scrolling is done automatically when point |
ac7845fd RS |
1361 | moves off the screen (or into the scroll margin). If the value is a |
1362 | positive integer @var{n}, then redisplay scrolls the text up to | |
1363 | @var{n} lines in either direction, if that will bring point back into | |
1364 | proper view. This action is called @dfn{conservative scrolling}. | |
1365 | Otherwise, scrolling happens in the usual way, under the control of | |
1366 | other variables such as @code{scroll-up-aggressively} and | |
1367 | @code{scroll-down-aggressively}. | |
1368 | ||
1369 | The default value is zero, which means that conservative scrolling | |
1370 | never happens. | |
1911e6e5 RS |
1371 | @end defopt |
1372 | ||
9db0af9e RS |
1373 | @defopt scroll-down-aggressively |
1374 | @tindex scroll-down-aggressively | |
04c1025b GM |
1375 | The value of this variable should be either @code{nil} or a fraction |
1376 | @var{f} between 0 and 1. If it is a fraction, that specifies where on | |
9db0af9e RS |
1377 | the screen to put point when scrolling down. More precisely, when a |
1378 | window scrolls down because point is above the window start, the new | |
1379 | start position is chosen to put point @var{f} part of the window | |
1380 | height from the top. The larger @var{f}, the more aggressive the | |
1381 | scrolling. | |
04c1025b | 1382 | |
2468d0c0 DL |
1383 | A value of @code{nil} is equivalent to .5, since its effect is to center |
1384 | point. This variable automatically becomes buffer-local when set in any | |
1385 | fashion. | |
04c1025b GM |
1386 | @end defopt |
1387 | ||
9db0af9e RS |
1388 | @defopt scroll-up-aggressively |
1389 | @tindex scroll-up-aggressively | |
1390 | Likewise, for scrolling up. The value, @var{f}, specifies how far | |
04c1025b GM |
1391 | point should be placed from the bottom of the window; thus, as with |
1392 | @code{scroll-up-aggressively}, a larger value scrolls more aggressively. | |
1393 | @end defopt | |
1394 | ||
1911e6e5 RS |
1395 | @defopt scroll-step |
1396 | This variable is an older variant of @code{scroll-conservatively}. The | |
1397 | difference is that it if its value is @var{n}, that permits scrolling | |
1398 | only by precisely @var{n} lines, not a smaller number. This feature | |
1399 | does not work with @code{scroll-margin}. The default value is zero. | |
1400 | @end defopt | |
1401 | ||
1911e6e5 RS |
1402 | @defopt scroll-preserve-screen-position |
1403 | If this option is non-@code{nil}, the scroll functions move point so | |
1404 | that the vertical position of the cursor is unchanged, when that is | |
1405 | possible. | |
b1b12a8e RS |
1406 | @end defopt |
1407 | ||
1408 | @defopt next-screen-context-lines | |
1409 | The value of this variable is the number of lines of continuity to | |
1410 | retain when scrolling by full screens. For example, @code{scroll-up} | |
1411 | with an argument of @code{nil} scrolls so that this many lines at the | |
1412 | bottom of the window appear instead at the top. The default value is | |
1413 | @code{2}. | |
1414 | @end defopt | |
1415 | ||
1416 | @deffn Command recenter &optional count | |
1417 | @cindex centering point | |
ac7845fd RS |
1418 | This function scrolls the text in the selected window so that point is |
1419 | displayed at a specified vertical position within the window. It does | |
1420 | not ``move point'' with respect to the text. | |
1421 | ||
1422 | If @var{count} is a nonnegative number, that puts the line containing | |
1423 | point @var{count} lines down from the top of the window. If | |
1424 | @var{count} is a negative number, then it counts upward from the | |
1425 | bottom of the window, so that @minus{}1 stands for the last usable | |
1426 | line in the window. If @var{count} is a non-@code{nil} list, then it | |
1427 | stands for the line in the middle of the window. | |
b1b12a8e RS |
1428 | |
1429 | If @var{count} is @code{nil}, @code{recenter} puts the line containing | |
1430 | point in the middle of the window, then clears and redisplays the entire | |
1431 | selected frame. | |
1432 | ||
1433 | When @code{recenter} is called interactively, @var{count} is the raw | |
1434 | prefix argument. Thus, typing @kbd{C-u} as the prefix sets the | |
1435 | @var{count} to a non-@code{nil} list, while typing @kbd{C-u 4} sets | |
1436 | @var{count} to 4, which positions the current line four lines from the | |
1437 | top. | |
1438 | ||
c638661f RS |
1439 | With an argument of zero, @code{recenter} positions the current line at |
1440 | the top of the window. This action is so handy that some people make a | |
1441 | separate key binding to do this. For example, | |
b1b12a8e RS |
1442 | |
1443 | @example | |
1444 | @group | |
1445 | (defun line-to-top-of-window () | |
1446 | "Scroll current line to top of window. | |
1447 | Replaces three keystroke sequence C-u 0 C-l." | |
3c29caa8 | 1448 | (interactive) |
b1b12a8e RS |
1449 | (recenter 0)) |
1450 | ||
3c29caa8 | 1451 | (global-set-key [kp-multiply] 'line-to-top-of-window) |
b1b12a8e RS |
1452 | @end group |
1453 | @end example | |
1454 | @end deffn | |
1455 | ||
8241495d RS |
1456 | @node Vertical Scrolling |
1457 | @section Vertical Fractional Scrolling | |
1458 | @cindex Vertical Fractional Scrolling | |
1459 | ||
1460 | @dfn{Vertical fractional scrolling} means shifting the image in the | |
1461 | window up or down by a specified multiple or fraction of a line. | |
1462 | Starting in Emacs 21, each window has a @dfn{vertical scroll position}, | |
1463 | which is a number, never less than zero. It specifies how far to raise | |
1464 | the contents of the window. Raising the window contents generally makes | |
1465 | all or part of some lines disappear off the top, and all or part of some | |
1466 | other lines appear at the bottom. The usual value is zero. | |
1467 | ||
1468 | The vertical scroll position is measured in units of the normal line | |
1469 | height, which is the height of the default font. Thus, if the value is | |
1470 | .5, that means the window contents are scrolled up half the normal line | |
1471 | height. If it is 3.3, that means the window contents are scrolled up | |
1472 | somewhat over three times the normal line height. | |
1473 | ||
1474 | What fraction of a line the vertical scrolling covers, or how many | |
1475 | lines, depends on what the lines contain. A value of .5 could scroll a | |
1476 | line whose height is very short off the screen, while a value of 3.3 | |
1477 | could scroll just part of the way through a tall line or an image. | |
1478 | ||
1479 | @defun window-vscroll &optional window | |
1480 | This function returns the current vertical scroll position of | |
1481 | @var{window}, If @var{window} is @code{nil}, the selected window is | |
1482 | used. | |
1483 | ||
1484 | @example | |
1485 | @group | |
1486 | (window-vscroll) | |
1487 | @result{} 0 | |
1488 | @end group | |
1489 | @end example | |
1490 | @end defun | |
1491 | ||
1492 | @defun set-window-vscroll window lines | |
1493 | This function sets @var{window}'s vertical scroll position to | |
1494 | @var{lines}. The argument @var{lines} should be zero or positive; if | |
1495 | not, it is taken as zero. | |
1496 | ||
eb687116 EZ |
1497 | If @var{window} is @code{nil}, the selected window is used. |
1498 | ||
8241495d RS |
1499 | The actual vertical scroll position must always correspond |
1500 | to an integral number of pixels, so the value you specify | |
1501 | is rounded accordingly. | |
1502 | ||
1503 | The return value is the result of this rounding. | |
1504 | ||
1505 | @example | |
1506 | @group | |
1507 | (set-window-vscroll (selected-window) 1.2) | |
1508 | @result{} 1.13 | |
1509 | @end group | |
1510 | @end example | |
1511 | @end defun | |
1512 | ||
b1b12a8e RS |
1513 | @node Horizontal Scrolling |
1514 | @section Horizontal Scrolling | |
1515 | @cindex horizontal scrolling | |
1516 | ||
8241495d RS |
1517 | @dfn{Horizontal scrolling} means shifting the image in the window left |
1518 | or right by a specified multiple of the normal character width. Each | |
061967de | 1519 | window has a @dfn{horizontal scroll position}, which is a number, never |
8241495d RS |
1520 | less than zero. It specifies how far to shift the contents left. |
1521 | Shifting the window contents left generally makes all or part of some | |
1522 | characters disappear off the left, and all or part of some other | |
1523 | characters appear at the right. The usual value is zero. | |
1524 | ||
1525 | The horizontal scroll position is measured in units of the normal | |
1526 | character width, which is the width of space in the default font. Thus, | |
1527 | if the value is 5, that means the window contents are scrolled left by 5 | |
c400241b | 1528 | times the normal character width. How many characters actually |
8241495d RS |
1529 | disappear off to the left depends on their width, and could vary from |
1530 | line to line. | |
1531 | ||
1532 | Because we read from side to side in the ``inner loop'', and from top | |
1533 | to bottom in the ``outer loop'', the effect of horizontal scrolling is | |
1534 | not like that of textual or vertical scrolling. Textual scrolling | |
1535 | involves selection of a portion of text to display, and vertical | |
1536 | scrolling moves the window contents contiguously; but horizontal | |
1537 | scrolling causes part of @emph{each line} to go off screen. | |
b1b12a8e RS |
1538 | |
1539 | Usually, no horizontal scrolling is in effect; then the leftmost | |
1540 | column is at the left edge of the window. In this state, scrolling to | |
8241495d RS |
1541 | the right is meaningless, since there is no data to the left of the edge |
1542 | to be revealed by it; so this is not allowed. Scrolling to the left is | |
1543 | allowed; it scrolls the first columns of text off the edge of the window | |
1544 | and can reveal additional columns on the right that were truncated | |
1545 | before. Once a window has a nonzero amount of leftward horizontal | |
1546 | scrolling, you can scroll it back to the right, but only so far as to | |
1547 | reduce the net horizontal scroll to zero. There is no limit to how far | |
1548 | left you can scroll, but eventually all the text will disappear off the | |
1549 | left edge. | |
1550 | ||
0594fc7f | 1551 | @vindex auto-hscroll-mode |
8241495d | 1552 | In Emacs 21, redisplay automatically alters the horizontal scrolling |
03ff8aab | 1553 | of a window as necessary to ensure that point is always visible, if |
0594fc7f | 1554 | @code{auto-hscroll-mode} is set. However, you can still set the |
03ff8aab GM |
1555 | horizontal scrolling value explicitly. The value you specify serves as |
1556 | a lower bound for automatic scrolling, i.e. automatic scrolling | |
1557 | will not scroll a window to a column less than the specified one. | |
8241495d RS |
1558 | |
1559 | @deffn Command scroll-left &optional count | |
b1b12a8e | 1560 | This function scrolls the selected window @var{count} columns to the |
8241495d RS |
1561 | left (or to the right if @var{count} is negative). The default |
1562 | for @var{count} is the window width, minus 2. | |
1563 | ||
1564 | The return value is the total amount of leftward horizontal scrolling in | |
1565 | effect after the change---just like the value returned by | |
1566 | @code{window-hscroll} (below). | |
b1b12a8e RS |
1567 | @end deffn |
1568 | ||
8241495d | 1569 | @deffn Command scroll-right &optional count |
b1b12a8e | 1570 | This function scrolls the selected window @var{count} columns to the |
8241495d RS |
1571 | right (or to the left if @var{count} is negative). The default |
1572 | for @var{count} is the window width, minus 2. | |
1573 | ||
1574 | The return value is the total amount of leftward horizontal scrolling in | |
1575 | effect after the change---just like the value returned by | |
1576 | @code{window-hscroll} (below). | |
b1b12a8e RS |
1577 | |
1578 | Once you scroll a window as far right as it can go, back to its normal | |
1579 | position where the total leftward scrolling is zero, attempts to scroll | |
1580 | any farther right have no effect. | |
1581 | @end deffn | |
1582 | ||
1583 | @defun window-hscroll &optional window | |
1584 | This function returns the total leftward horizontal scrolling of | |
1585 | @var{window}---the number of columns by which the text in @var{window} | |
1586 | is scrolled left past the left margin. | |
1587 | ||
1588 | The value is never negative. It is zero when no horizontal scrolling | |
1589 | has been done in @var{window} (which is usually the case). | |
1590 | ||
1591 | If @var{window} is @code{nil}, the selected window is used. | |
1592 | ||
1593 | @example | |
1594 | @group | |
1595 | (window-hscroll) | |
1596 | @result{} 0 | |
1597 | @end group | |
1598 | @group | |
1599 | (scroll-left 5) | |
1600 | @result{} 5 | |
1601 | @end group | |
1602 | @group | |
1603 | (window-hscroll) | |
1604 | @result{} 5 | |
1605 | @end group | |
1606 | @end example | |
1607 | @end defun | |
1608 | ||
1609 | @defun set-window-hscroll window columns | |
1610 | This function sets the number of columns from the left margin that | |
f9f59935 | 1611 | @var{window} is scrolled from the value of @var{columns}. The argument |
b1b12a8e | 1612 | @var{columns} should be zero or positive; if not, it is taken as zero. |
8241495d | 1613 | Fractional values of @var{columns} are not supported at present. |
b1b12a8e | 1614 | |
515a9a0f RS |
1615 | Note that @code{set-window-hscroll} may appear not to work if you test |
1616 | it by evaluating a call with @kbd{M-:} in a simple way. What happens | |
1617 | is that the function sets the horizontal scroll value and returns, but | |
1618 | then redisplay adjusts the horizontal scrolling to make point visible, | |
1619 | and this overrides what the function did. You can observe the | |
1620 | function's effect if you call it while point is sufficiently far from | |
1621 | the left margin that it will remain visible. | |
1622 | ||
b1b12a8e RS |
1623 | The value returned is @var{columns}. |
1624 | ||
1625 | @example | |
1626 | @group | |
1627 | (set-window-hscroll (selected-window) 10) | |
1628 | @result{} 10 | |
1629 | @end group | |
1630 | @end example | |
1631 | @end defun | |
1632 | ||
1633 | Here is how you can determine whether a given position @var{position} | |
1634 | is off the screen due to horizontal scrolling: | |
1635 | ||
1636 | @example | |
1637 | @group | |
c638661f | 1638 | (defun hscroll-on-screen (window position) |
3c29caa8 | 1639 | (save-excursion |
c638661f | 1640 | (goto-char position) |
3c29caa8 | 1641 | (and |
c638661f RS |
1642 | (>= (- (current-column) (window-hscroll window)) 0) |
1643 | (< (- (current-column) (window-hscroll window)) | |
1644 | (window-width window))))) | |
b1b12a8e RS |
1645 | @end group |
1646 | @end example | |
1647 | ||
1648 | @node Size of Window | |
1649 | @section The Size of a Window | |
1650 | @cindex window size | |
1651 | @cindex size of window | |
1652 | ||
1653 | An Emacs window is rectangular, and its size information consists of | |
1654 | the height (the number of lines) and the width (the number of character | |
1655 | positions in each line). The mode line is included in the height. But | |
1656 | the width does not count the scroll bar or the column of @samp{|} | |
c638661f | 1657 | characters that separates side-by-side windows. |
b1b12a8e RS |
1658 | |
1659 | The following three functions return size information about a window: | |
1660 | ||
1661 | @defun window-height &optional window | |
88f7b76a RS |
1662 | This function returns the number of lines in @var{window}, including |
1663 | its mode line and header line, if any. If @var{window} fills its | |
1664 | entire frame except for the echo area, and there is no tool bar, this | |
1665 | is typically one less than the value of @code{frame-height} on that | |
1666 | frame. | |
b1b12a8e RS |
1667 | |
1668 | If @var{window} is @code{nil}, the function uses the selected window. | |
1669 | ||
1670 | @example | |
1671 | @group | |
1672 | (window-height) | |
1673 | @result{} 23 | |
1674 | @end group | |
1675 | @group | |
1676 | (split-window-vertically) | |
1677 | @result{} #<window 4 on windows.texi> | |
1678 | @end group | |
1679 | @group | |
1680 | (window-height) | |
1681 | @result{} 11 | |
1682 | @end group | |
1683 | @end example | |
1684 | @end defun | |
1685 | ||
88f7b76a RS |
1686 | @tindex window-body-height |
1687 | @defun window-body-height &optional window | |
1688 | Like @code{window-height} but the value does not include the | |
1689 | mode line (if any) or the header line (if any). | |
1690 | @end defun | |
1691 | ||
b1b12a8e RS |
1692 | @defun window-width &optional window |
1693 | This function returns the number of columns in @var{window}. If | |
1694 | @var{window} fills its entire frame, this is the same as the value of | |
1695 | @code{frame-width} on that frame. The width does not include the | |
1696 | window's scroll bar or the column of @samp{|} characters that separates | |
1697 | side-by-side windows. | |
1698 | ||
1699 | If @var{window} is @code{nil}, the function uses the selected window. | |
1700 | ||
1701 | @example | |
1702 | @group | |
1703 | (window-width) | |
1704 | @result{} 80 | |
1705 | @end group | |
1706 | @end example | |
1707 | @end defun | |
1708 | ||
1709 | @defun window-edges &optional window | |
1710 | This function returns a list of the edge coordinates of @var{window}. | |
1711 | If @var{window} is @code{nil}, the selected window is used. | |
1712 | ||
1713 | The order of the list is @code{(@var{left} @var{top} @var{right} | |
1714 | @var{bottom})}, all elements relative to 0, 0 at the top left corner of | |
1715 | the frame. The element @var{right} of the value is one more than the | |
1716 | rightmost column used by @var{window}, and @var{bottom} is one more than | |
1717 | the bottommost row used by @var{window} and its mode-line. | |
1718 | ||
8241495d RS |
1719 | If a window has a scroll bar, the right edge value includes the width of |
1720 | the scroll bar. Otherwise, if the window has a neighbor on the right, | |
1721 | its right edge value includes the width of the separator line between | |
1722 | the window and that neighbor. Since the width of the window does not | |
1723 | include this separator, the width does not usually equal the difference | |
1724 | between the right and left edges. | |
b1b12a8e RS |
1725 | |
1726 | Here is the result obtained on a typical 24-line terminal with just one | |
1727 | window: | |
1728 | ||
1729 | @example | |
1730 | @group | |
1731 | (window-edges (selected-window)) | |
1732 | @result{} (0 0 80 23) | |
1733 | @end group | |
1734 | @end example | |
1735 | ||
c638661f RS |
1736 | @noindent |
1737 | The bottom edge is at line 23 because the last line is the echo area. | |
1738 | ||
fb1d9004 RS |
1739 | If @var{window} is at the upper left corner of its frame, then |
1740 | @var{bottom} is the same as the value of @code{(window-height)}, | |
8241495d RS |
1741 | @var{right} is almost the same as the value of @code{(window-width)}, |
1742 | and @var{top} and @var{left} are zero. For example, the edges of the | |
1743 | following window are @w{@samp{0 0 8 5}}. Assuming that the frame has | |
1744 | more than 8 columns, the last column of the window (column 7) holds a | |
1745 | border rather than text. The last row (row 4) holds the mode line, | |
1746 | shown here with @samp{xxxxxxxxx}. | |
b1b12a8e RS |
1747 | |
1748 | @example | |
1749 | @group | |
3c29caa8 | 1750 | 0 |
b1b12a8e | 1751 | _______ |
3c29caa8 DH |
1752 | 0 | | |
1753 | | | | |
1754 | | | | |
1755 | | | | |
b1b12a8e RS |
1756 | xxxxxxxxx 4 |
1757 | ||
3c29caa8 | 1758 | 7 |
b1b12a8e RS |
1759 | @end group |
1760 | @end example | |
1761 | ||
b1b12a8e RS |
1762 | In the following example, let's suppose that the frame is 7 |
1763 | columns wide. Then the edges of the left window are @w{@samp{0 0 4 3}} | |
8241495d | 1764 | and the edges of the right window are @w{@samp{4 0 8 3}}. |
b1b12a8e RS |
1765 | |
1766 | @example | |
1767 | @group | |
1768 | ___ ___ | |
3c29caa8 DH |
1769 | | | | |
1770 | | | | | |
1771 | xxxxxxxxx | |
b1b12a8e RS |
1772 | |
1773 | 0 34 7 | |
1774 | @end group | |
1775 | @end example | |
1776 | @end defun | |
1777 | ||
1778 | @node Resizing Windows | |
1779 | @section Changing the Size of a Window | |
1780 | @cindex window resizing | |
1781 | @cindex changing window size | |
1782 | @cindex window size, changing | |
1783 | ||
1784 | The window size functions fall into two classes: high-level commands | |
1785 | that change the size of windows and low-level functions that access | |
1786 | window size. Emacs does not permit overlapping windows or gaps between | |
1787 | windows, so resizing one window affects other windows. | |
1788 | ||
1789 | @deffn Command enlarge-window size &optional horizontal | |
c638661f | 1790 | This function makes the selected window @var{size} lines taller, |
b1b12a8e RS |
1791 | stealing lines from neighboring windows. It takes the lines from one |
1792 | window at a time until that window is used up, then takes from another. | |
1793 | If a window from which lines are stolen shrinks below | |
1794 | @code{window-min-height} lines, that window disappears. | |
1795 | ||
1796 | If @var{horizontal} is non-@code{nil}, this function makes | |
1797 | @var{window} wider by @var{size} columns, stealing columns instead of | |
1798 | lines. If a window from which columns are stolen shrinks below | |
1799 | @code{window-min-width} columns, that window disappears. | |
1800 | ||
c638661f RS |
1801 | If the requested size would exceed that of the window's frame, then the |
1802 | function makes the window occupy the entire height (or width) of the | |
1803 | frame. | |
b1b12a8e | 1804 | |
8241495d RS |
1805 | If there are various other windows from which lines or columns can be |
1806 | stolen, and some of them specify fixed size (using | |
1807 | @code{window-size-fixed}, see below), they are left untouched while | |
1808 | other windows are ``robbed.'' If it would be necessary to alter the | |
1809 | size of a fixed-size window, @code{enlarge-window} gets an error | |
1810 | instead. | |
1811 | ||
b1b12a8e RS |
1812 | If @var{size} is negative, this function shrinks the window by |
1813 | @minus{}@var{size} lines or columns. If that makes the window smaller | |
1814 | than the minimum size (@code{window-min-height} and | |
1815 | @code{window-min-width}), @code{enlarge-window} deletes the window. | |
1816 | ||
3c29caa8 | 1817 | @code{enlarge-window} returns @code{nil}. |
b1b12a8e RS |
1818 | @end deffn |
1819 | ||
1820 | @deffn Command enlarge-window-horizontally columns | |
1821 | This function makes the selected window @var{columns} wider. | |
1822 | It could be defined as follows: | |
1823 | ||
1824 | @example | |
1825 | @group | |
1826 | (defun enlarge-window-horizontally (columns) | |
1827 | (enlarge-window columns t)) | |
1828 | @end group | |
1829 | @end example | |
1830 | @end deffn | |
1831 | ||
1832 | @deffn Command shrink-window size &optional horizontal | |
1833 | This function is like @code{enlarge-window} but negates the argument | |
1834 | @var{size}, making the selected window smaller by giving lines (or | |
1835 | columns) to the other windows. If the window shrinks below | |
1836 | @code{window-min-height} or @code{window-min-width}, then it disappears. | |
1837 | ||
1838 | If @var{size} is negative, the window is enlarged by @minus{}@var{size} | |
1839 | lines or columns. | |
1840 | @end deffn | |
1841 | ||
1842 | @deffn Command shrink-window-horizontally columns | |
1843 | This function makes the selected window @var{columns} narrower. | |
1844 | It could be defined as follows: | |
1845 | ||
1846 | @example | |
1847 | @group | |
1848 | (defun shrink-window-horizontally (columns) | |
1849 | (shrink-window columns t)) | |
1850 | @end group | |
1851 | @end example | |
1852 | @end deffn | |
1853 | ||
8241495d | 1854 | @deffn Command shrink-window-if-larger-than-buffer &optional window |
1911e6e5 RS |
1855 | This command shrinks @var{window} to be as small as possible while still |
1856 | showing the full contents of its buffer---but not less than | |
8241495d RS |
1857 | @code{window-min-height} lines. If @var{window} is not given, |
1858 | it defaults to the selected window. | |
1911e6e5 RS |
1859 | |
1860 | However, the command does nothing if the window is already too small to | |
1861 | display the whole text of the buffer, or if part of the contents are | |
1862 | currently scrolled off screen, or if the window is not the full width of | |
1863 | its frame, or if the window is the only window in its frame. | |
1864 | @end deffn | |
1865 | ||
8241495d RS |
1866 | @tindex window-size-fixed |
1867 | @defvar window-size-fixed | |
1868 | If this variable is non-@code{nil}, in any given buffer, | |
1869 | then the size of any window displaying the buffer remains fixed | |
1870 | unless you explicitly change it or Emacs has no other choice. | |
1871 | (This feature is new in Emacs 21.) | |
1872 | ||
1873 | If the value is @code{height}, then only the window's height is fixed; | |
1874 | if the value is @code{width}, then only the window's width is fixed. | |
1875 | Any other non-@code{nil} value fixes both the width and the height. | |
1876 | ||
1877 | The usual way to use this variable is to give it a buffer-local value in | |
1878 | a particular buffer. That way, the windows (but usually there is only | |
1879 | one) displaying that buffer have fixed size. | |
1880 | ||
1881 | Explicit size-change functions such as @code{enlarge-window} | |
1882 | get an error if they would have to change a window size which is fixed. | |
1883 | Therefore, when you want to change the size of such a window, | |
1884 | you should bind @code{window-size-fixed} to @code{nil}, like this: | |
1885 | ||
1886 | @example | |
1887 | (let ((window-size-fixed nil)) | |
1888 | (enlarge-window 10)) | |
1889 | @end example | |
1890 | ||
1891 | Note that changing the frame size will change the size of a | |
1892 | fixed-size window, if there is no other alternative. | |
1893 | @end defvar | |
1894 | ||
b1b12a8e | 1895 | @cindex minimum window size |
926a5166 | 1896 | The following two variables constrain the window-structure-changing |
b1b12a8e RS |
1897 | functions to a minimum height and width. |
1898 | ||
1899 | @defopt window-min-height | |
1900 | The value of this variable determines how short a window may become | |
1901 | before it is automatically deleted. Making a window smaller than | |
926a5166 RS |
1902 | @code{window-min-height} automatically deletes it, and no window may |
1903 | be created shorter than this. The default value is 4. | |
1904 | ||
1905 | The absolute minimum window height is one; actions that change window | |
1906 | sizes reset this variable to one if it is less than one. | |
b1b12a8e RS |
1907 | @end defopt |
1908 | ||
1909 | @defopt window-min-width | |
1910 | The value of this variable determines how narrow a window may become | |
1911e6e5 | 1911 | before it is automatically deleted. Making a window smaller than |
b1b12a8e | 1912 | @code{window-min-width} automatically deletes it, and no window may be |
926a5166 RS |
1913 | created narrower than this. The default value is 10. |
1914 | ||
1915 | The absolute minimum window width is two; actions that change window | |
1916 | sizes reset this variable to two if it is less than two. | |
b1b12a8e RS |
1917 | @end defopt |
1918 | ||
1919 | @node Coordinates and Windows | |
1920 | @section Coordinates and Windows | |
1921 | ||
c638661f | 1922 | This section describes how to relate screen coordinates to windows. |
b1b12a8e RS |
1923 | |
1924 | @defun window-at x y &optional frame | |
1925 | This function returns the window containing the specified cursor | |
1926 | position in the frame @var{frame}. The coordinates @var{x} and @var{y} | |
1927 | are measured in characters and count from the top left corner of the | |
1928 | frame. If they are out of range, @code{window-at} returns @code{nil}. | |
1929 | ||
1930 | If you omit @var{frame}, the selected frame is used. | |
1931 | @end defun | |
1932 | ||
1933 | @defun coordinates-in-window-p coordinates window | |
1934 | This function checks whether a particular frame position falls within | |
1935 | the window @var{window}. | |
1936 | ||
969fe9b5 RS |
1937 | The argument @var{coordinates} is a cons cell of the form @code{(@var{x} |
1938 | . @var{y})}. The coordinates @var{x} and @var{y} are measured in | |
1939 | characters, and count from the top left corner of the screen or frame. | |
b1b12a8e | 1940 | |
f9f59935 RS |
1941 | The value returned by @code{coordinates-in-window-p} is non-@code{nil} |
1942 | if the coordinates are inside @var{window}. The value also indicates | |
1943 | what part of the window the position is in, as follows: | |
b1b12a8e RS |
1944 | |
1945 | @table @code | |
1946 | @item (@var{relx} . @var{rely}) | |
1947 | The coordinates are inside @var{window}. The numbers @var{relx} and | |
1948 | @var{rely} are the equivalent window-relative coordinates for the | |
1949 | specified position, counting from 0 at the top left corner of the | |
1950 | window. | |
1951 | ||
1952 | @item mode-line | |
1953 | The coordinates are in the mode line of @var{window}. | |
1954 | ||
8241495d RS |
1955 | @item header-line |
1956 | The coordinates are in the header line of @var{window}. | |
1957 | ||
1958 | @item vertical-line | |
b1b12a8e | 1959 | The coordinates are in the vertical line between @var{window} and its |
3c29caa8 | 1960 | neighbor to the right. This value occurs only if the window doesn't |
b1b12a8e | 1961 | have a scroll bar; positions in a scroll bar are considered outside the |
8241495d | 1962 | window for these purposes. |
b1b12a8e RS |
1963 | |
1964 | @item nil | |
1965 | The coordinates are not in any part of @var{window}. | |
1966 | @end table | |
1967 | ||
1968 | The function @code{coordinates-in-window-p} does not require a frame as | |
1969 | argument because it always uses the frame that @var{window} is on. | |
1970 | @end defun | |
1971 | ||
1972 | @node Window Configurations | |
1973 | @section Window Configurations | |
1974 | @cindex window configurations | |
1975 | @cindex saving window information | |
1976 | ||
f9f59935 | 1977 | A @dfn{window configuration} records the entire layout of one |
c02dd51a RS |
1978 | frame---all windows, their sizes, which buffers they contain, what |
1979 | part of each buffer is displayed, and the values of point and the | |
1980 | mark. It also includes the values of @code{window-min-height}, | |
1981 | @code{window-min-width} and @code{minibuffer-scroll-window}. An | |
1982 | exception is made for point in the selected window for the current | |
1983 | buffer; its value is not saved in the window configuration. | |
1984 | ||
1985 | You can bring back an entire previous layout by restoring a window | |
1986 | configuration previously saved. If you want to record all frames | |
1987 | instead of just one, use a frame configuration instead of a window | |
1988 | configuration. @xref{Frame Configurations}. | |
b1b12a8e | 1989 | |
8241495d | 1990 | @defun current-window-configuration &optional frame |
c02dd51a RS |
1991 | This function returns a new object representing @var{frame}'s current |
1992 | window configuration. If @var{frame} is omitted, the selected frame | |
1993 | is used. | |
b1b12a8e RS |
1994 | @end defun |
1995 | ||
1996 | @defun set-window-configuration configuration | |
f9f59935 | 1997 | This function restores the configuration of windows and buffers as |
8241495d RS |
1998 | specified by @var{configuration}, for the frame that @var{configuration} |
1999 | was created for. | |
2000 | ||
2001 | The argument @var{configuration} must be a value that was previously | |
2002 | returned by @code{current-window-configuration}. This configuration is | |
2003 | restored in the frame from which @var{configuration} was made, whether | |
2004 | that frame is selected or not. This always counts as a window size | |
2005 | change and triggers execution of the @code{window-size-change-functions} | |
969fe9b5 RS |
2006 | (@pxref{Window Hooks}), because @code{set-window-configuration} doesn't |
2007 | know how to tell whether the new configuration actually differs from the | |
2008 | old one. | |
2009 | ||
2010 | If the frame which @var{configuration} was saved from is dead, all this | |
2011 | function does is restore the three variables @code{window-min-height}, | |
2012 | @code{window-min-width} and @code{minibuffer-scroll-window}. | |
bfe721d1 | 2013 | |
b1b12a8e RS |
2014 | Here is a way of using this function to get the same effect |
2015 | as @code{save-window-excursion}: | |
2016 | ||
2017 | @example | |
2018 | @group | |
2019 | (let ((config (current-window-configuration))) | |
2020 | (unwind-protect | |
2021 | (progn (split-window-vertically nil) | |
2022 | @dots{}) | |
2023 | (set-window-configuration config))) | |
2024 | @end group | |
2025 | @end example | |
2026 | @end defun | |
2027 | ||
2028 | @defspec save-window-excursion forms@dots{} | |
2029 | This special form records the window configuration, executes @var{forms} | |
2030 | in sequence, then restores the earlier window configuration. The window | |
2031 | configuration includes the value of point and the portion of the buffer | |
c638661f | 2032 | that is visible. It also includes the choice of selected window. |
b1b12a8e | 2033 | However, it does not include the value of point in the current buffer; |
f9f59935 | 2034 | use @code{save-excursion} also, if you wish to preserve that. |
b1b12a8e | 2035 | |
bfe721d1 KH |
2036 | Don't use this construct when @code{save-selected-window} is all you need. |
2037 | ||
2038 | Exit from @code{save-window-excursion} always triggers execution of the | |
2039 | @code{window-size-change-functions}. (It doesn't know how to tell | |
2040 | whether the restored configuration actually differs from the one in | |
2041 | effect at the end of the @var{forms}.) | |
2042 | ||
b1b12a8e RS |
2043 | The return value is the value of the final form in @var{forms}. |
2044 | For example: | |
2045 | ||
2046 | @example | |
2047 | @group | |
2048 | (split-window) | |
2049 | @result{} #<window 25 on control.texi> | |
2050 | @end group | |
2051 | @group | |
2052 | (setq w (selected-window)) | |
2053 | @result{} #<window 19 on control.texi> | |
2054 | @end group | |
2055 | @group | |
2056 | (save-window-excursion | |
2057 | (delete-other-windows w) | |
2058 | (switch-to-buffer "foo") | |
2059 | 'do-something) | |
2060 | @result{} do-something | |
2061 | ;; @r{The screen is now split again.} | |
2062 | @end group | |
2063 | @end example | |
2064 | @end defspec | |
2065 | ||
2066 | @defun window-configuration-p object | |
2067 | This function returns @code{t} if @var{object} is a window configuration. | |
969fe9b5 RS |
2068 | @end defun |
2069 | ||
2070 | @defun compare-window-configurations config1 config2 | |
2071 | This function compares two window configurations as regards the | |
2072 | structure of windows, but ignores the values of point and mark and the | |
2073 | saved scrolling positions---it can return @code{t} even if those | |
2074 | aspects differ. | |
2075 | ||
2076 | The function @code{equal} can also compare two window configurations; it | |
2077 | regards configurations as unequal if they differ in any respect, even a | |
2078 | saved point or mark. | |
b1b12a8e RS |
2079 | @end defun |
2080 | ||
2081 | Primitives to look inside of window configurations would make sense, | |
2082 | but none are implemented. It is not clear they are useful enough to be | |
2083 | worth implementing. | |
f9f59935 RS |
2084 | |
2085 | @node Window Hooks | |
2086 | @section Hooks for Window Scrolling and Changes | |
2087 | ||
2088 | This section describes how a Lisp program can take action whenever a | |
2089 | window displays a different part of its buffer or a different buffer. | |
2090 | There are three actions that can change this: scrolling the window, | |
2091 | switching buffers in the window, and changing the size of the window. | |
2092 | The first two actions run @code{window-scroll-functions}; the last runs | |
2093 | @code{window-size-change-functions}. The paradigmatic use of these | |
969fe9b5 RS |
2094 | hooks is in the implementation of Lazy Lock mode; see @ref{Support |
2095 | Modes, Lazy Lock, Font Lock Support Modes, emacs, The GNU Emacs Manual}. | |
f9f59935 RS |
2096 | |
2097 | @defvar window-scroll-functions | |
2098 | This variable holds a list of functions that Emacs should call before | |
2099 | redisplaying a window with scrolling. It is not a normal hook, because | |
2100 | each function is called with two arguments: the window, and its new | |
2101 | display-start position. | |
2102 | ||
2103 | Displaying a different buffer in the window also runs these functions. | |
2104 | ||
1911e6e5 RS |
2105 | These functions must be careful in using @code{window-end} |
2106 | (@pxref{Window Start}); if you need an up-to-date value, you must use | |
2107 | the @var{update} argument to ensure you get it. | |
f9f59935 RS |
2108 | @end defvar |
2109 | ||
2110 | @defvar window-size-change-functions | |
2111 | This variable holds a list of functions to be called if the size of any | |
2112 | window changes for any reason. The functions are called just once per | |
2113 | redisplay, and just once for each frame on which size changes have | |
2114 | occurred. | |
2115 | ||
2116 | Each function receives the frame as its sole argument. There is no | |
2117 | direct way to find out which windows on that frame have changed size, or | |
2118 | precisely how. However, if a size-change function records, at each | |
2119 | call, the existing windows and their sizes, it can also compare the | |
2120 | present sizes and the previous sizes. | |
2121 | ||
2122 | Creating or deleting windows counts as a size change, and therefore | |
2123 | causes these functions to be called. Changing the frame size also | |
2124 | counts, because it changes the sizes of the existing windows. | |
2125 | ||
2126 | It is not a good idea to use @code{save-window-excursion} (@pxref{Window | |
2127 | Configurations}) in these functions, because that always counts as a | |
2128 | size change, and it would cause these functions to be called over and | |
2129 | over. In most cases, @code{save-selected-window} (@pxref{Selecting | |
2130 | Windows}) is what you need here. | |
2131 | @end defvar | |
2132 | ||
f9f59935 | 2133 | @defvar redisplay-end-trigger-functions |
1911e6e5 | 2134 | This abnormal hook is run whenever redisplay in a window uses text that |
f9f59935 RS |
2135 | extends past a specified end trigger position. You set the end trigger |
2136 | position with the function @code{set-window-redisplay-end-trigger}. The | |
2137 | functions are called with two arguments: the window, and the end trigger | |
2138 | position. Storing @code{nil} for the end trigger position turns off the | |
2139 | feature, and the trigger value is automatically reset to @code{nil} just | |
2140 | after the hook is run. | |
2141 | @end defvar | |
2142 | ||
f9f59935 RS |
2143 | @defun set-window-redisplay-end-trigger window position |
2144 | This function sets @var{window}'s end trigger position at | |
2145 | @var{position}. | |
2146 | @end defun | |
2147 | ||
8241495d | 2148 | @defun window-redisplay-end-trigger &optional window |
f9f59935 RS |
2149 | This function returns @var{window}'s current end trigger position. |
2150 | @end defun | |
2151 | ||
f9f59935 RS |
2152 | @defvar window-configuration-change-hook |
2153 | A normal hook that is run every time you change the window configuration | |
2154 | of an existing frame. This includes splitting or deleting windows, | |
2155 | changing the sizes of windows, or displaying a different buffer in a | |
2156 | window. The frame whose window configuration has changed is the | |
2157 | selected frame when this hook runs. | |
2158 | @end defvar |