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