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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, 1995, 1998, 1999, 2001, | |
4 | @c 2002, 2003, 2004, 2005, 2006, 2007 Free Software Foundation, Inc. | |
5 | @c See the file elisp.texi for copying conditions. | |
6336d8c3 | 6 | @setfilename ../../info/windows |
b8d4c8d0 GM |
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 | |
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-level 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. | |
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. | |
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 Tree:: The layout and sizes of all windows in a frame. | |
34 | * Window Configurations:: Saving and restoring the state of the screen. | |
35 | * Window Hooks:: Hooks for scrolling, window size changes, | |
36 | redisplay going past a certain point, | |
37 | or window configuration changes. | |
38 | @end menu | |
39 | ||
40 | @node Basic Windows | |
41 | @section Basic Concepts of Emacs Windows | |
42 | @cindex window | |
43 | @cindex selected window | |
44 | ||
45 | A @dfn{window} in Emacs is the physical area of the screen in which a | |
46 | buffer is displayed. The term is also used to refer to a Lisp object that | |
47 | represents that screen area in Emacs Lisp. It should be | |
48 | clear from the context which is meant. | |
49 | ||
50 | Emacs groups windows into frames. A frame represents an area of | |
51 | screen available for Emacs to use. Each frame always contains at least | |
52 | one window, but you can subdivide it vertically or horizontally into | |
53 | multiple nonoverlapping Emacs windows. | |
54 | ||
55 | In each frame, at any time, one and only one window is designated as | |
56 | @dfn{selected within the frame}. The frame's cursor appears in that | |
57 | window, but the other windows have ``non-selected'' cursors, normally | |
7ed54cc5 RS |
58 | less visible. (@pxref{Cursor Parameters}, for customization of this.) |
59 | At any time, one frame is the selected frame; and the window selected | |
60 | within that frame is @dfn{the selected window}. The selected window's | |
61 | buffer is usually the current buffer (except when @code{set-buffer} | |
62 | has been used). @xref{Current Buffer}. | |
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63 | |
64 | For practical purposes, a window exists only while it is displayed in | |
65 | a frame. Once removed from the frame, the window is effectively deleted | |
66 | and should not be used, @emph{even though there may still be references | |
67 | to it} from other Lisp objects. Restoring a saved window configuration | |
68 | is the only way for a window no longer on the screen to come back to | |
69 | life. (@xref{Deleting Windows}.) | |
70 | ||
71 | Each window has the following attributes: | |
72 | ||
73 | @itemize @bullet | |
74 | @item | |
75 | containing frame | |
76 | ||
77 | @item | |
78 | window height | |
79 | ||
80 | @item | |
81 | window width | |
82 | ||
83 | @item | |
84 | window edges with respect to the screen or frame | |
85 | ||
86 | @item | |
87 | the buffer it displays | |
88 | ||
89 | @item | |
90 | position within the buffer at the upper left of the window | |
91 | ||
92 | @item | |
93 | amount of horizontal scrolling, in columns | |
94 | ||
95 | @item | |
96 | point | |
97 | ||
98 | @item | |
99 | the mark | |
100 | ||
101 | @item | |
102 | how recently the window was selected | |
103 | ||
104 | @item | |
105 | fringe settings | |
106 | ||
107 | @item | |
108 | display margins | |
109 | ||
110 | @item | |
111 | scroll-bar settings | |
112 | @end itemize | |
113 | ||
114 | @cindex multiple windows | |
115 | Users create multiple windows so they can look at several buffers at | |
116 | once. Lisp libraries use multiple windows for a variety of reasons, but | |
117 | most often to display related information. In Rmail, for example, you | |
118 | can move through a summary buffer in one window while the other window | |
119 | shows messages one at a time as they are reached. | |
120 | ||
121 | The meaning of ``window'' in Emacs is similar to what it means in the | |
122 | context of general-purpose window systems such as X, but not identical. | |
123 | The X Window System places X windows on the screen; Emacs uses one or | |
124 | more X windows as frames, and subdivides them into | |
125 | Emacs windows. When you use Emacs on a character-only terminal, Emacs | |
126 | treats the whole terminal screen as one frame. | |
127 | ||
128 | @cindex terminal screen | |
129 | @cindex screen of terminal | |
130 | @cindex tiled windows | |
131 | Most window systems support arbitrarily located overlapping windows. | |
132 | In contrast, Emacs windows are @dfn{tiled}; they never overlap, and | |
133 | together they fill the whole screen or frame. Because of the way in | |
134 | which Emacs creates new windows and resizes them, not all conceivable | |
135 | tilings of windows on an Emacs frame are actually possible. | |
136 | @xref{Splitting Windows}, and @ref{Size of Window}. | |
137 | ||
138 | @xref{Display}, for information on how the contents of the | |
139 | window's buffer are displayed in the window. | |
140 | ||
141 | @defun windowp object | |
142 | This function returns @code{t} if @var{object} is a window. | |
143 | @end defun | |
144 | ||
145 | @node Splitting Windows | |
146 | @section Splitting Windows | |
147 | @cindex splitting windows | |
148 | @cindex window splitting | |
149 | ||
150 | The functions described here are the primitives used to split a window | |
151 | into two windows. Two higher level functions sometimes split a window, | |
152 | but not always: @code{pop-to-buffer} and @code{display-buffer} | |
153 | (@pxref{Displaying Buffers}). | |
154 | ||
155 | The functions described here do not accept a buffer as an argument. | |
156 | The two ``halves'' of the split window initially display the same buffer | |
157 | previously visible in the window that was split. | |
158 | ||
159 | @deffn Command split-window &optional window size horizontal | |
160 | This function splits a new window out of @var{window}'s screen area. | |
161 | It returns the new window. | |
162 | ||
163 | If @var{horizontal} is non-@code{nil}, then @var{window} splits into | |
164 | two side by side windows. The original window @var{window} keeps the | |
165 | leftmost @var{size} columns, and gives the rest of the columns to the | |
166 | new window. Otherwise, it splits into windows one above the other, and | |
167 | @var{window} keeps the upper @var{size} lines and gives the rest of the | |
168 | lines to the new window. The original window is therefore the | |
169 | left-hand or upper of the two, and the new window is the right-hand or | |
170 | lower. | |
171 | ||
172 | If @var{window} is omitted or @code{nil}, that stands for the selected | |
173 | window. When you split the selected window, it remains selected. | |
174 | ||
175 | If @var{size} is omitted or @code{nil}, then @var{window} is divided | |
176 | evenly into two parts. (If there is an odd line, it is allocated to | |
177 | the new window.) When @code{split-window} is called interactively, | |
178 | all its arguments are @code{nil}. | |
179 | ||
180 | If splitting would result in making a window that is smaller than | |
181 | @code{window-min-height} or @code{window-min-width}, the function | |
182 | signals an error and does not split the window at all. | |
183 | ||
184 | The following example starts with one window on a screen that is 50 | |
185 | lines high by 80 columns wide; then it splits the window. | |
186 | ||
187 | @smallexample | |
188 | @group | |
189 | (setq w (selected-window)) | |
190 | @result{} #<window 8 on windows.texi> | |
191 | (window-edges) ; @r{Edges in order:} | |
192 | @result{} (0 0 80 50) ; @r{left--top--right--bottom} | |
193 | @end group | |
194 | ||
195 | @group | |
196 | ;; @r{Returns window created} | |
197 | (setq w2 (split-window w 15)) | |
198 | @result{} #<window 28 on windows.texi> | |
199 | @end group | |
200 | @group | |
201 | (window-edges w2) | |
202 | @result{} (0 15 80 50) ; @r{Bottom window;} | |
203 | ; @r{top is line 15} | |
204 | @end group | |
205 | @group | |
206 | (window-edges w) | |
207 | @result{} (0 0 80 15) ; @r{Top window} | |
208 | @end group | |
209 | @end smallexample | |
210 | ||
211 | The screen looks like this: | |
212 | ||
213 | @smallexample | |
214 | @group | |
215 | __________ | |
216 | | | line 0 | |
217 | | w | | |
218 | |__________| | |
219 | | | line 15 | |
220 | | w2 | | |
221 | |__________| | |
222 | line 50 | |
223 | column 0 column 80 | |
224 | @end group | |
225 | @end smallexample | |
226 | ||
227 | Next, split the top window horizontally: | |
228 | ||
229 | @smallexample | |
230 | @group | |
231 | (setq w3 (split-window w 35 t)) | |
232 | @result{} #<window 32 on windows.texi> | |
233 | @end group | |
234 | @group | |
235 | (window-edges w3) | |
236 | @result{} (35 0 80 15) ; @r{Left edge at column 35} | |
237 | @end group | |
238 | @group | |
239 | (window-edges w) | |
240 | @result{} (0 0 35 15) ; @r{Right edge at column 35} | |
241 | @end group | |
242 | @group | |
243 | (window-edges w2) | |
244 | @result{} (0 15 80 50) ; @r{Bottom window unchanged} | |
245 | @end group | |
246 | @end smallexample | |
247 | ||
248 | @need 3000 | |
249 | Now the screen looks like this: | |
250 | ||
251 | @smallexample | |
252 | @group | |
253 | column 35 | |
254 | __________ | |
255 | | | | line 0 | |
256 | | w | w3 | | |
257 | |___|______| | |
258 | | | line 15 | |
259 | | w2 | | |
260 | |__________| | |
261 | line 50 | |
262 | column 0 column 80 | |
263 | @end group | |
264 | @end smallexample | |
265 | ||
266 | Normally, Emacs indicates the border between two side-by-side windows | |
267 | with a scroll bar (@pxref{Layout Parameters,Scroll Bars}) or @samp{|} | |
268 | characters. The display table can specify alternative border | |
269 | characters; see @ref{Display Tables}. | |
270 | @end deffn | |
271 | ||
272 | @deffn Command split-window-vertically &optional size | |
273 | This function splits the selected window into two windows, one above the | |
274 | other, leaving the upper of the two windows selected, with @var{size} | |
275 | lines. (If @var{size} is negative, then the lower of the two windows | |
276 | gets @minus{} @var{size} lines and the upper window gets the rest, but | |
277 | the upper window is still the one selected.) However, if | |
278 | @code{split-window-keep-point} (see below) is @code{nil}, then either | |
279 | window can be selected. | |
280 | ||
281 | In other respects, this function is similar to @code{split-window}. | |
282 | In particular, the upper window is the original one and the return | |
283 | value is the new, lower window. | |
284 | @end deffn | |
285 | ||
286 | @defopt split-window-keep-point | |
287 | If this variable is non-@code{nil} (the default), then | |
288 | @code{split-window-vertically} behaves as described above. | |
289 | ||
290 | If it is @code{nil}, then @code{split-window-vertically} adjusts point | |
291 | in each of the two windows to avoid scrolling. (This is useful on | |
292 | slow terminals.) It selects whichever window contains the screen line | |
293 | that point was previously on. | |
294 | ||
295 | This variable only affects the behavior of @code{split-window-vertically}. | |
296 | It has no effect on the other functions described here. | |
297 | @end defopt | |
298 | ||
299 | @deffn Command split-window-horizontally &optional size | |
300 | This function splits the selected window into two windows | |
301 | side-by-side, leaving the selected window on the left with @var{size} | |
302 | columns. If @var{size} is negative, the rightmost window gets | |
303 | @minus{} @var{size} columns, but the leftmost window still remains | |
304 | selected. | |
305 | ||
306 | This function is basically an interface to @code{split-window}. | |
307 | You could define a simplified version of the function like this: | |
308 | ||
309 | @smallexample | |
310 | @group | |
311 | (defun split-window-horizontally (&optional arg) | |
312 | "Split selected window into two windows, side by side..." | |
313 | (interactive "P") | |
314 | @end group | |
315 | @group | |
316 | (let ((size (and arg (prefix-numeric-value arg)))) | |
317 | (and size (< size 0) | |
318 | (setq size (+ (window-width) size))) | |
319 | (split-window nil size t))) | |
320 | @end group | |
321 | @end smallexample | |
322 | @end deffn | |
323 | ||
324 | @defun one-window-p &optional no-mini all-frames | |
325 | This function returns non-@code{nil} if there is only one window. The | |
326 | argument @var{no-mini}, if non-@code{nil}, means don't count the | |
327 | minibuffer even if it is active; otherwise, the minibuffer window is | |
328 | counted when it is active. | |
329 | ||
330 | The argument @var{all-frames} specifies which frames to consider. Here | |
331 | are the possible values and their meanings: | |
332 | ||
333 | @table @asis | |
334 | @item @code{nil} | |
335 | Count the windows in the selected frame, plus the minibuffer used | |
336 | by that frame even if it lies in some other frame. | |
337 | ||
338 | @item @code{t} | |
339 | Count all windows in all existing frames. | |
340 | ||
341 | @item @code{visible} | |
342 | Count all windows in all visible frames. | |
343 | ||
344 | @item 0 | |
345 | Count all windows in all visible or iconified frames. | |
346 | ||
347 | @item anything else | |
348 | Count precisely the windows in the selected frame, and no others. | |
349 | @end table | |
350 | @end defun | |
351 | ||
352 | @node Deleting Windows | |
353 | @section Deleting Windows | |
354 | @cindex deleting windows | |
355 | ||
356 | A window remains visible on its frame unless you @dfn{delete} it by | |
357 | calling certain functions that delete windows. A deleted window cannot | |
358 | appear on the screen, but continues to exist as a Lisp object until | |
359 | there are no references to it. There is no way to cancel the deletion | |
360 | of a window aside from restoring a saved window configuration | |
361 | (@pxref{Window Configurations}). Restoring a window configuration also | |
362 | deletes any windows that aren't part of that configuration. | |
363 | ||
364 | When you delete a window, the space it took up is given to one | |
365 | adjacent sibling. | |
366 | ||
367 | @c Emacs 19 feature | |
368 | @defun window-live-p window | |
369 | This function returns @code{nil} if @var{window} is deleted, and | |
370 | @code{t} otherwise. | |
371 | ||
372 | @strong{Warning:} Erroneous information or fatal errors may result from | |
373 | using a deleted window as if it were live. | |
374 | @end defun | |
375 | ||
376 | @deffn Command delete-window &optional window | |
377 | This function removes @var{window} from display, and returns @code{nil}. | |
378 | If @var{window} is omitted, then the selected window is deleted. An | |
379 | error is signaled if there is only one window when @code{delete-window} | |
380 | is called. | |
381 | @end deffn | |
382 | ||
383 | @deffn Command delete-other-windows &optional window | |
384 | This function makes @var{window} the only window on its frame, by | |
385 | deleting the other windows in that frame. If @var{window} is omitted or | |
386 | @code{nil}, then the selected window is used by default. | |
387 | ||
388 | The return value is @code{nil}. | |
389 | @end deffn | |
390 | ||
391 | @deffn Command delete-windows-on buffer-or-name &optional frame | |
392 | This function deletes all windows showing @var{buffer-or-name}. If | |
393 | there are no windows showing @var{buffer-or-name}, it does nothing. | |
394 | @var{buffer-or-name} must be a buffer or the name of an existing | |
395 | buffer. | |
396 | ||
397 | @code{delete-windows-on} operates frame by frame. If a frame has | |
398 | several windows showing different buffers, then those showing | |
399 | @var{buffer-or-name} are removed, and the others expand to fill the | |
400 | space. If all windows in some frame are showing @var{buffer-or-name} | |
401 | (including the case where there is only one window), then the frame | |
402 | winds up with a single window showing another buffer chosen with | |
403 | @code{other-buffer}. @xref{The Buffer List}. | |
404 | ||
405 | The argument @var{frame} controls which frames to operate on. This | |
406 | function does not use it in quite the same way as the other functions | |
407 | which scan all windows; specifically, the values @code{t} and @code{nil} | |
408 | have the opposite of their meanings in other functions. Here are the | |
409 | full details: | |
410 | ||
411 | @itemize @bullet | |
412 | @item | |
413 | If it is @code{nil}, operate on all frames. | |
414 | @item | |
415 | If it is @code{t}, operate on the selected frame. | |
416 | @item | |
417 | If it is @code{visible}, operate on all visible frames. | |
418 | @item | |
419 | If it is 0, operate on all visible or iconified frames. | |
420 | @item | |
421 | If it is a frame, operate on that frame. | |
422 | @end itemize | |
423 | ||
424 | This function always returns @code{nil}. | |
425 | @end deffn | |
426 | ||
427 | @node Selecting Windows | |
428 | @section Selecting Windows | |
429 | @cindex selecting a window | |
430 | ||
431 | When a window is selected, the buffer in the window becomes the current | |
432 | buffer, and the cursor will appear in it. | |
433 | ||
434 | @defun selected-window | |
435 | This function returns the selected window. This is the window in | |
436 | which the cursor appears and to which many commands apply. | |
437 | @end defun | |
438 | ||
439 | @defun select-window window &optional norecord | |
440 | This function makes @var{window} the selected window. The cursor then | |
441 | appears in @var{window} (on redisplay). Unless @var{window} was | |
442 | already selected, @code{select-window} makes @var{window}'s buffer the | |
443 | current buffer. | |
444 | ||
445 | Normally @var{window}'s selected buffer is moved to the front of the | |
446 | buffer list, but if @var{norecord} is non-@code{nil}, the buffer list | |
447 | order is unchanged. | |
448 | ||
449 | The return value is @var{window}. | |
450 | ||
451 | @example | |
452 | @group | |
453 | (setq w (next-window)) | |
454 | (select-window w) | |
455 | @result{} #<window 65 on windows.texi> | |
456 | @end group | |
457 | @end example | |
458 | @end defun | |
459 | ||
460 | @defmac save-selected-window forms@dots{} | |
461 | This macro records the selected frame, as well as the selected window | |
462 | of each frame, executes @var{forms} in sequence, then restores the | |
463 | earlier selected frame and windows. It also saves and restores the | |
464 | current buffer. It returns the value of the last form in @var{forms}. | |
465 | ||
466 | This macro does not save or restore anything about the sizes, | |
467 | arrangement or contents of windows; therefore, if the @var{forms} | |
468 | change them, the change persists. If the previously selected window | |
469 | of some frame is no longer live at the time of exit from @var{forms}, | |
470 | that frame's selected window is left alone. If the previously | |
471 | selected window is no longer live, then whatever window is selected at | |
472 | the end of @var{forms} remains selected. | |
473 | @end defmac | |
474 | ||
475 | @defmac with-selected-window window forms@dots{} | |
476 | This macro selects @var{window} (without changing the buffer list), | |
477 | executes @var{forms} in sequence, then restores the previously | |
478 | selected window and current buffer. It is just like | |
479 | @code{save-selected-window}, except that it explicitly selects | |
480 | @var{window}, also without altering the buffer list sequence. | |
481 | @end defmac | |
482 | ||
483 | @cindex finding windows | |
484 | The following functions choose one of the windows on the screen, | |
485 | offering various criteria for the choice. | |
486 | ||
487 | @defun get-lru-window &optional frame dedicated | |
488 | This function returns the window least recently ``used'' (that is, | |
489 | selected). If any full-width windows are present, it only considers | |
490 | these. The selected window is always the most recently used window. | |
491 | ||
492 | The selected window can be the least recently used window if it is the | |
493 | only window. A newly created window becomes the least recently used | |
494 | window until it is selected. A minibuffer window is never a | |
495 | candidate. Dedicated windows are never candidates unless the | |
496 | @var{dedicated} argument is non-@code{nil}, so if all | |
497 | existing windows are dedicated, the value is @code{nil}. | |
498 | ||
499 | The argument @var{frame} controls which windows are considered. | |
500 | ||
501 | @itemize @bullet | |
502 | @item | |
503 | If it is @code{nil}, consider windows on the selected frame. | |
504 | @item | |
505 | If it is @code{t}, consider windows on all frames. | |
506 | @item | |
507 | If it is @code{visible}, consider windows on all visible frames. | |
508 | @item | |
509 | If it is 0, consider windows on all visible or iconified frames. | |
510 | @item | |
511 | If it is a frame, consider windows on that frame. | |
512 | @end itemize | |
513 | @end defun | |
514 | ||
515 | @defun get-largest-window &optional frame dedicated | |
516 | This function returns the window with the largest area (height times | |
517 | width). If there are no side-by-side windows, then this is the window | |
518 | with the most lines. A minibuffer window is never a candidate. | |
519 | Dedicated windows are never candidates unless the | |
520 | @var{dedicated} argument is non-@code{nil}, so if all existing windows | |
521 | are dedicated, the value is @code{nil}. | |
522 | ||
523 | If there are two candidate windows of the same size, this function | |
524 | prefers the one that comes first in the cyclic ordering of windows | |
525 | (see following section), starting from the selected window. | |
526 | ||
527 | The argument @var{frame} controls which set of windows to | |
528 | consider. See @code{get-lru-window}, above. | |
529 | @end defun | |
530 | ||
531 | @cindex window that satisfies a predicate | |
532 | @cindex conditional selection of windows | |
533 | @defun get-window-with-predicate predicate &optional minibuf all-frames default | |
534 | This function returns a window satisfying @var{predicate}. It cycles | |
535 | through all visible windows using @code{walk-windows} (@pxref{Cyclic | |
536 | Window Ordering}), calling @var{predicate} on each one of them | |
537 | with that window as its argument. The function returns the first | |
538 | window for which @var{predicate} returns a non-@code{nil} value; if | |
539 | that never happens, it returns @var{default}. | |
540 | ||
541 | The optional arguments @var{minibuf} and @var{all-frames} specify the | |
542 | set of windows to include in the scan. See the description of | |
543 | @code{next-window} in @ref{Cyclic Window Ordering}, for details. | |
544 | @end defun | |
545 | ||
546 | @node Cyclic Window Ordering | |
547 | @comment node-name, next, previous, up | |
548 | @section Cyclic Ordering of Windows | |
549 | @cindex cyclic ordering of windows | |
550 | @cindex ordering of windows, cyclic | |
551 | @cindex window ordering, cyclic | |
552 | ||
553 | When you use the command @kbd{C-x o} (@code{other-window}) to select | |
554 | the next window, it moves through all the windows on the screen in a | |
555 | specific cyclic order. For any given configuration of windows, this | |
556 | order never varies. It is called the @dfn{cyclic ordering of windows}. | |
557 | ||
558 | This ordering generally goes from top to bottom, and from left to | |
559 | right. But it may go down first or go right first, depending on the | |
560 | order in which the windows were split. | |
561 | ||
562 | If the first split was vertical (into windows one above each other), | |
563 | and then the subwindows were split horizontally, then the ordering is | |
564 | left to right in the top of the frame, and then left to right in the | |
565 | next lower part of the frame, and so on. If the first split was | |
566 | horizontal, the ordering is top to bottom in the left part, and so on. | |
567 | In general, within each set of siblings at any level in the window tree, | |
568 | the order is left to right, or top to bottom. | |
569 | ||
570 | @defun next-window &optional window minibuf all-frames | |
571 | @cindex minibuffer window, and @code{next-window} | |
572 | This function returns the window following @var{window} in the cyclic | |
573 | ordering of windows. This is the window that @kbd{C-x o} would select | |
574 | if typed when @var{window} is selected. If @var{window} is the only | |
575 | window visible, then this function returns @var{window}. If omitted, | |
576 | @var{window} defaults to the selected window. | |
577 | ||
578 | The value of the argument @var{minibuf} determines whether the | |
579 | minibuffer is included in the window order. Normally, when | |
580 | @var{minibuf} is @code{nil}, the minibuffer is included if it is | |
581 | currently active; this is the behavior of @kbd{C-x o}. (The minibuffer | |
582 | window is active while the minibuffer is in use. @xref{Minibuffers}.) | |
583 | ||
584 | If @var{minibuf} is @code{t}, then the cyclic ordering includes the | |
585 | minibuffer window even if it is not active. | |
586 | ||
587 | If @var{minibuf} is neither @code{t} nor @code{nil}, then the minibuffer | |
588 | window is not included even if it is active. | |
589 | ||
590 | The argument @var{all-frames} specifies which frames to consider. Here | |
591 | are the possible values and their meanings: | |
592 | ||
593 | @table @asis | |
594 | @item @code{nil} | |
595 | Consider all the windows in @var{window}'s frame, plus the minibuffer | |
596 | used by that frame even if it lies in some other frame. If the | |
597 | minibuffer counts (as determined by @var{minibuf}), then all windows on | |
598 | all frames that share that minibuffer count too. | |
599 | ||
600 | @item @code{t} | |
601 | Consider all windows in all existing frames. | |
602 | ||
603 | @item @code{visible} | |
604 | Consider all windows in all visible frames. (To get useful results, you | |
605 | must ensure @var{window} is in a visible frame.) | |
606 | ||
607 | @item 0 | |
608 | Consider all windows in all visible or iconified frames. | |
609 | ||
610 | @item a frame | |
611 | Consider all windows on that frame. | |
612 | ||
613 | @item anything else | |
614 | Consider precisely the windows in @var{window}'s frame, and no others. | |
615 | @end table | |
616 | ||
617 | This example assumes there are two windows, both displaying the | |
618 | buffer @samp{windows.texi}: | |
619 | ||
620 | @example | |
621 | @group | |
622 | (selected-window) | |
623 | @result{} #<window 56 on windows.texi> | |
624 | @end group | |
625 | @group | |
626 | (next-window (selected-window)) | |
627 | @result{} #<window 52 on windows.texi> | |
628 | @end group | |
629 | @group | |
630 | (next-window (next-window (selected-window))) | |
631 | @result{} #<window 56 on windows.texi> | |
632 | @end group | |
633 | @end example | |
634 | @end defun | |
635 | ||
636 | @defun previous-window &optional window minibuf all-frames | |
637 | This function returns the window preceding @var{window} in the cyclic | |
638 | ordering of windows. The other arguments specify which windows to | |
639 | include in the cycle, as in @code{next-window}. | |
640 | @end defun | |
641 | ||
642 | @deffn Command other-window count &optional all-frames | |
643 | This function selects the @var{count}th following window in the cyclic | |
644 | order. If count is negative, then it moves back @minus{}@var{count} | |
645 | windows in the cycle, rather than forward. It returns @code{nil}. | |
646 | ||
647 | The argument @var{all-frames} has the same meaning as in | |
648 | @code{next-window}, but the @var{minibuf} argument of @code{next-window} | |
649 | is always effectively @code{nil}. | |
650 | ||
651 | In an interactive call, @var{count} is the numeric prefix argument. | |
652 | @end deffn | |
653 | ||
654 | @c Emacs 19 feature | |
655 | @defun walk-windows proc &optional minibuf all-frames | |
656 | This function cycles through all windows. It calls the function | |
657 | @code{proc} once for each window, with the window as its sole | |
658 | argument. | |
659 | ||
660 | The optional arguments @var{minibuf} and @var{all-frames} specify the | |
661 | set of windows to include in the scan. See @code{next-window}, above, | |
662 | for details. | |
663 | @end defun | |
664 | ||
665 | @defun window-list &optional frame minibuf window | |
666 | This function returns a list of the windows on @var{frame}, starting | |
667 | with @var{window}. If @var{frame} is @code{nil} or omitted, | |
668 | @code{window-list} uses the selected frame instead; if @var{window} is | |
669 | @code{nil} or omitted, it uses the selected window. | |
670 | ||
671 | The value of @var{minibuf} determines if the minibuffer window is | |
672 | included in the result list. If @var{minibuf} is @code{t}, the result | |
673 | always includes the minibuffer window. If @var{minibuf} is @code{nil} | |
674 | or omitted, that includes the minibuffer window if it is active. If | |
675 | @var{minibuf} is neither @code{nil} nor @code{t}, the result never | |
676 | includes the minibuffer window. | |
677 | @end defun | |
678 | ||
679 | @node Buffers and Windows | |
680 | @section Buffers and Windows | |
681 | @cindex examining windows | |
682 | @cindex windows, controlling precisely | |
683 | @cindex buffers, controlled in windows | |
684 | ||
685 | This section describes low-level functions to examine windows or to | |
686 | display buffers in windows in a precisely controlled fashion. | |
687 | @iftex | |
688 | See the following section for | |
689 | @end iftex | |
690 | @ifnottex | |
691 | @xref{Displaying Buffers}, for | |
692 | @end ifnottex | |
693 | related functions that find a window to use and specify a buffer for it. | |
694 | The functions described there are easier to use than these, but they | |
695 | employ heuristics in choosing or creating a window; use these functions | |
696 | when you need complete control. | |
697 | ||
698 | @defun set-window-buffer window buffer-or-name &optional keep-margins | |
699 | This function makes @var{window} display @var{buffer-or-name} as its | |
700 | contents. It returns @code{nil}. @var{buffer-or-name} must be a | |
701 | buffer, or the name of an existing buffer. This is the fundamental | |
702 | primitive for changing which buffer is displayed in a window, and all | |
703 | ways of doing that call this function. | |
704 | ||
705 | @example | |
706 | @group | |
707 | (set-window-buffer (selected-window) "foo") | |
708 | @result{} nil | |
709 | @end group | |
710 | @end example | |
711 | ||
712 | Normally, displaying @var{buffer} in @var{window} resets the window's | |
713 | display margins, fringe widths, scroll bar settings, and position | |
714 | based on the local variables of @var{buffer}. However, if | |
715 | @var{keep-margins} is non-@code{nil}, the display margins and fringe | |
716 | widths of @var{window} remain unchanged. @xref{Fringes}. | |
717 | @end defun | |
718 | ||
719 | @defvar buffer-display-count | |
720 | This buffer-local variable records the number of times a buffer is | |
721 | displayed in a window. It is incremented each time | |
722 | @code{set-window-buffer} is called for the buffer. | |
723 | @end defvar | |
724 | ||
725 | @defun window-buffer &optional window | |
726 | This function returns the buffer that @var{window} is displaying. If | |
727 | @var{window} is omitted, this function returns the buffer for the | |
728 | selected window. | |
729 | ||
730 | @example | |
731 | @group | |
732 | (window-buffer) | |
733 | @result{} #<buffer windows.texi> | |
734 | @end group | |
735 | @end example | |
736 | @end defun | |
737 | ||
738 | @defun get-buffer-window buffer-or-name &optional all-frames | |
739 | This function returns a window currently displaying | |
740 | @var{buffer-or-name}, or @code{nil} if there is none. If there are | |
741 | several such windows, then the function returns the first one in the | |
742 | cyclic ordering of windows, starting from the selected window. | |
743 | @xref{Cyclic Window Ordering}. | |
744 | ||
745 | The argument @var{all-frames} controls which windows to consider. | |
746 | ||
747 | @itemize @bullet | |
748 | @item | |
749 | If it is @code{nil}, consider windows on the selected frame. | |
750 | @item | |
751 | If it is @code{t}, consider windows on all frames. | |
752 | @item | |
753 | If it is @code{visible}, consider windows on all visible frames. | |
754 | @item | |
755 | If it is 0, consider windows on all visible or iconified frames. | |
756 | @item | |
757 | If it is a frame, consider windows on that frame. | |
758 | @end itemize | |
759 | @end defun | |
760 | ||
761 | @defun get-buffer-window-list buffer-or-name &optional minibuf all-frames | |
762 | This function returns a list of all the windows currently displaying | |
763 | @var{buffer-or-name}. | |
764 | ||
765 | The two optional arguments work like the optional arguments of | |
766 | @code{next-window} (@pxref{Cyclic Window Ordering}); they are @emph{not} | |
767 | like the single optional argument of @code{get-buffer-window}. Perhaps | |
768 | we should change @code{get-buffer-window} in the future to make it | |
769 | compatible with the other functions. | |
770 | @end defun | |
771 | ||
772 | @defvar buffer-display-time | |
773 | This variable records the time at which a buffer was last made visible | |
774 | in a window. It is always local in each buffer; each time | |
775 | @code{set-window-buffer} is called, it sets this variable to | |
776 | @code{(current-time)} in the specified buffer (@pxref{Time of Day}). | |
777 | When a buffer is first created, @code{buffer-display-time} starts out | |
778 | with the value @code{nil}. | |
779 | @end defvar | |
780 | ||
781 | @node Displaying Buffers | |
782 | @section Displaying Buffers in Windows | |
783 | @cindex switching to a buffer | |
784 | @cindex displaying a buffer | |
785 | ||
786 | In this section we describe convenient functions that choose a window | |
787 | automatically and use it to display a specified buffer. These functions | |
788 | can also split an existing window in certain circumstances. We also | |
789 | describe variables that parameterize the heuristics used for choosing a | |
790 | window. | |
791 | @iftex | |
792 | See the preceding section for | |
793 | @end iftex | |
794 | @ifnottex | |
795 | @xref{Buffers and Windows}, for | |
796 | @end ifnottex | |
797 | low-level functions that give you more precise control. All of these | |
798 | functions work by calling @code{set-window-buffer}. | |
799 | ||
800 | Do not use the functions in this section in order to make a buffer | |
801 | current so that a Lisp program can access or modify it; they are too | |
802 | drastic for that purpose, since they change the display of buffers in | |
803 | windows, which would be gratuitous and surprise the user. Instead, use | |
804 | @code{set-buffer} and @code{save-current-buffer} (@pxref{Current | |
805 | Buffer}), which designate buffers as current for programmed access | |
806 | without affecting the display of buffers in windows. | |
807 | ||
808 | @deffn Command switch-to-buffer buffer-or-name &optional norecord | |
809 | This function makes @var{buffer-or-name} the current buffer, and also | |
810 | displays the buffer in the selected window. This means that a human can | |
811 | see the buffer and subsequent keyboard commands will apply to it. | |
812 | Contrast this with @code{set-buffer}, which makes @var{buffer-or-name} | |
813 | the current buffer but does not display it in the selected window. | |
814 | @xref{Current Buffer}. | |
815 | ||
816 | If @var{buffer-or-name} does not identify an existing buffer, then a new | |
817 | buffer by that name is created. The major mode for the new buffer is | |
818 | set according to the variable @code{default-major-mode}. @xref{Auto | |
819 | Major Mode}. If @var{buffer-or-name} is @code{nil}, | |
820 | @code{switch-to-buffer} chooses a buffer using @code{other-buffer}. | |
821 | ||
822 | Normally the specified buffer is put at the front of the buffer list | |
823 | (both the selected frame's buffer list and the frame-independent buffer | |
824 | list). This affects the operation of @code{other-buffer}. However, if | |
825 | @var{norecord} is non-@code{nil}, this is not done. @xref{The Buffer | |
826 | List}. | |
827 | ||
828 | The @code{switch-to-buffer} function is often used interactively, as | |
829 | the binding of @kbd{C-x b}. It is also used frequently in programs. It | |
830 | returns the buffer that it switched to. | |
831 | @end deffn | |
832 | ||
833 | The next two functions are similar to @code{switch-to-buffer}, except | |
834 | for the described features. | |
835 | ||
836 | @deffn Command switch-to-buffer-other-window buffer-or-name &optional norecord | |
837 | This function makes @var{buffer-or-name} the current buffer and | |
838 | displays it in a window not currently selected. It then selects that | |
839 | window. The handling of the buffer is the same as in | |
840 | @code{switch-to-buffer}. | |
841 | ||
842 | The currently selected window is absolutely never used to do the job. | |
843 | If it is the only window, then it is split to make a distinct window for | |
844 | this purpose. If the selected window is already displaying the buffer, | |
845 | then it continues to do so, but another window is nonetheless found to | |
846 | display it in as well. | |
847 | ||
848 | This function updates the buffer list just like @code{switch-to-buffer} | |
849 | unless @var{norecord} is non-@code{nil}. | |
850 | @end deffn | |
851 | ||
852 | @defun pop-to-buffer buffer-or-name &optional other-window norecord | |
853 | This function makes @var{buffer-or-name} the current buffer and | |
854 | switches to it in some window, preferably not the window previously | |
855 | selected. The ``popped-to'' window becomes the selected window within | |
856 | its frame. The return value is the buffer that was switched to. | |
857 | If @var{buffer-or-name} is @code{nil}, that means to choose some | |
858 | other buffer, but you don't specify which. | |
859 | ||
860 | If the variable @code{pop-up-frames} is non-@code{nil}, | |
861 | @code{pop-to-buffer} looks for a window in any visible frame already | |
862 | displaying the buffer; if there is one, it returns that window and makes | |
863 | it be selected within its frame. If there is none, it creates a new | |
864 | frame and displays the buffer in it. | |
865 | ||
866 | If @code{pop-up-frames} is @code{nil}, then @code{pop-to-buffer} | |
867 | operates entirely within the selected frame. (If the selected frame has | |
868 | just a minibuffer, @code{pop-to-buffer} operates within the most | |
869 | recently selected frame that was not just a minibuffer.) | |
870 | ||
871 | If the variable @code{pop-up-windows} is non-@code{nil}, windows may | |
872 | be split to create a new window that is different from the original | |
873 | window. For details, see @ref{Choosing Window}. | |
874 | ||
875 | If @var{other-window} is non-@code{nil}, @code{pop-to-buffer} finds or | |
876 | creates another window even if @var{buffer-or-name} is already visible | |
877 | in the selected window. Thus @var{buffer-or-name} could end up | |
878 | displayed in two windows. On the other hand, if @var{buffer-or-name} is | |
879 | already displayed in the selected window and @var{other-window} is | |
880 | @code{nil}, then the selected window is considered sufficient display | |
881 | for @var{buffer-or-name}, so that nothing needs to be done. | |
882 | ||
883 | All the variables that affect @code{display-buffer} affect | |
884 | @code{pop-to-buffer} as well. @xref{Choosing Window}. | |
885 | ||
886 | If @var{buffer-or-name} is a string that does not name an existing | |
887 | buffer, a buffer by that name is created. The major mode for the new | |
888 | buffer is set according to the variable @code{default-major-mode}. | |
889 | @xref{Auto Major Mode}. | |
890 | ||
891 | This function updates the buffer list just like @code{switch-to-buffer} | |
892 | unless @var{norecord} is non-@code{nil}. | |
893 | @end defun | |
894 | ||
895 | @deffn Command replace-buffer-in-windows buffer-or-name | |
896 | This function replaces @var{buffer-or-name} with some other buffer in all | |
897 | windows displaying it. It chooses the other buffer with | |
898 | @code{other-buffer}. In the usual applications of this function, you | |
899 | don't care which other buffer is used; you just want to make sure that | |
900 | @var{buffer-or-name} is no longer displayed. | |
901 | ||
902 | This function returns @code{nil}. | |
903 | @end deffn | |
904 | ||
905 | @node Choosing Window | |
906 | @section Choosing a Window for Display | |
907 | ||
908 | This section describes the basic facility that chooses a window to | |
909 | display a buffer in---@code{display-buffer}. All the higher-level | |
910 | functions and commands use this subroutine. Here we describe how to use | |
911 | @code{display-buffer} and how to customize it. | |
912 | ||
913 | @deffn Command display-buffer buffer-or-name &optional not-this-window frame | |
914 | This command makes @var{buffer-or-name} appear in some window, like | |
915 | @code{pop-to-buffer}, but it does not select that window and does not | |
916 | make the buffer current. The identity of the selected window is | |
917 | unaltered by this function. @var{buffer-or-name} must be a buffer, or | |
918 | the name of an existing buffer. | |
919 | ||
920 | If @var{not-this-window} is non-@code{nil}, it means to display the | |
921 | specified buffer in a window other than the selected one, even if it is | |
922 | already on display in the selected window. This can cause the buffer to | |
923 | appear in two windows at once. Otherwise, if @var{buffer-or-name} is | |
924 | already being displayed in any window, that is good enough, so this | |
925 | function does nothing. | |
926 | ||
927 | @code{display-buffer} returns the window chosen to display | |
928 | @var{buffer-or-name}. | |
929 | ||
930 | If the argument @var{frame} is non-@code{nil}, it specifies which frames | |
931 | to check when deciding whether the buffer is already displayed. If the | |
932 | buffer is already displayed in some window on one of these frames, | |
933 | @code{display-buffer} simply returns that window. Here are the possible | |
934 | values of @var{frame}: | |
935 | ||
936 | @itemize @bullet | |
937 | @item | |
938 | If it is @code{nil}, consider windows on the selected frame. | |
939 | (Actually, the last non-minibuffer frame.) | |
940 | @item | |
941 | If it is @code{t}, consider windows on all frames. | |
942 | @item | |
943 | If it is @code{visible}, consider windows on all visible frames. | |
944 | @item | |
945 | If it is 0, consider windows on all visible or iconified frames. | |
946 | @item | |
947 | If it is a frame, consider windows on that frame. | |
948 | @end itemize | |
949 | ||
950 | Precisely how @code{display-buffer} finds or creates a window depends on | |
951 | the variables described below. | |
952 | @end deffn | |
953 | ||
954 | @defopt display-buffer-reuse-frames | |
955 | If this variable is non-@code{nil}, @code{display-buffer} searches | |
956 | existing frames for a window displaying the buffer. If the buffer is | |
957 | already displayed in a window in some frame, @code{display-buffer} makes | |
958 | the frame visible and raises it, to use that window. If the buffer is | |
959 | not already displayed, or if @code{display-buffer-reuse-frames} is | |
960 | @code{nil}, @code{display-buffer}'s behavior is determined by other | |
961 | variables, described below. | |
962 | @end defopt | |
963 | ||
964 | @defopt pop-up-windows | |
965 | This variable controls whether @code{display-buffer} makes new windows. | |
966 | If it is non-@code{nil} and there is only one window, then that window | |
967 | is split. If it is @code{nil}, then @code{display-buffer} does not | |
968 | split the single window, but uses it whole. | |
969 | @end defopt | |
970 | ||
971 | @defopt split-height-threshold | |
972 | This variable determines when @code{display-buffer} may split a window, | |
973 | if there are multiple windows. @code{display-buffer} always splits the | |
974 | largest window if it has at least this many lines. If the largest | |
975 | window is not this tall, it is split only if it is the sole window and | |
976 | @code{pop-up-windows} is non-@code{nil}. | |
977 | @end defopt | |
978 | ||
979 | @defopt even-window-heights | |
980 | This variable determines if @code{display-buffer} should even out window | |
981 | heights if the buffer gets displayed in an existing window, above or | |
982 | beneath another existing window. If @code{even-window-heights} is | |
983 | @code{t}, the default, window heights will be evened out. If | |
984 | @code{even-window-heights} is @code{nil}, the original window heights | |
985 | will be left alone. | |
986 | @end defopt | |
987 | ||
988 | @c Emacs 19 feature | |
989 | @defopt pop-up-frames | |
990 | This variable controls whether @code{display-buffer} makes new frames. | |
991 | If it is non-@code{nil}, @code{display-buffer} looks for an existing | |
992 | window already displaying the desired buffer, on any visible frame. If | |
993 | it finds one, it returns that window. Otherwise it makes a new frame. | |
994 | The variables @code{pop-up-windows} and @code{split-height-threshold} do | |
995 | not matter if @code{pop-up-frames} is non-@code{nil}. | |
996 | ||
997 | If @code{pop-up-frames} is @code{nil}, then @code{display-buffer} either | |
998 | splits a window or reuses one. | |
999 | ||
1000 | @xref{Frames}, for more information. | |
1001 | @end defopt | |
1002 | ||
1003 | @c Emacs 19 feature | |
1004 | @defopt pop-up-frame-function | |
1005 | This variable specifies how to make a new frame if @code{pop-up-frames} | |
1006 | is non-@code{nil}. | |
1007 | ||
1008 | Its value should be a function of no arguments. When | |
1009 | @code{display-buffer} makes a new frame, it does so by calling that | |
1010 | function, which should return a frame. The default value of the | |
1011 | variable is a function that creates a frame using parameters from | |
1012 | @code{pop-up-frame-alist}. | |
1013 | @end defopt | |
1014 | ||
1015 | @defopt pop-up-frame-alist | |
1016 | This variable holds an alist specifying frame parameters used when | |
1017 | @code{display-buffer} makes a new frame. @xref{Frame Parameters}, for | |
1018 | more information about frame parameters. | |
1019 | @end defopt | |
1020 | ||
1021 | @defopt special-display-buffer-names | |
1022 | A list of buffer names for buffers that should be displayed specially. | |
1023 | If the buffer's name is in this list, @code{display-buffer} handles the | |
1024 | buffer specially. | |
1025 | ||
1026 | By default, special display means to give the buffer a dedicated frame. | |
1027 | ||
1028 | If an element is a list, instead of a string, then the @sc{car} of the | |
1029 | list is the buffer name, and the rest of the list says how to create | |
1030 | the frame. There are two possibilities for the rest of the list (its | |
1031 | @sc{cdr}). It can be an alist, specifying frame parameters, or it can | |
1032 | contain a function and arguments to give to it. (The function's first | |
1033 | argument is always the buffer to be displayed; the arguments from the | |
1034 | list come after that.) | |
1035 | ||
1036 | For example: | |
1037 | ||
1038 | @example | |
1039 | (("myfile" (minibuffer) (menu-bar-lines . 0))) | |
1040 | @end example | |
1041 | ||
1042 | @noindent | |
1043 | specifies to display a buffer named @samp{myfile} in a dedicated frame | |
1044 | with specified @code{minibuffer} and @code{menu-bar-lines} parameters. | |
1045 | ||
1046 | The list of frame parameters can also use the phony frame parameters | |
1047 | @code{same-frame} and @code{same-window}. If the specified frame | |
1048 | parameters include @code{(same-window . @var{value})} and @var{value} | |
1049 | is non-@code{nil}, that means to display the buffer in the current | |
1050 | selected window. Otherwise, if they include @code{(same-frame . | |
1051 | @var{value})} and @var{value} is non-@code{nil}, that means to display | |
1052 | the buffer in a new window in the currently selected frame. | |
1053 | @end defopt | |
1054 | ||
1055 | @defopt special-display-regexps | |
1056 | A list of regular expressions that specify buffers that should be | |
1057 | displayed specially. If the buffer's name matches any of the regular | |
1058 | expressions in this list, @code{display-buffer} handles the buffer | |
1059 | specially. | |
1060 | ||
1061 | By default, special display means to give the buffer a dedicated frame. | |
1062 | ||
1063 | If an element is a list, instead of a string, then the @sc{car} of the | |
1064 | list is the regular expression, and the rest of the list says how to | |
1065 | create the frame. See above, under @code{special-display-buffer-names}. | |
1066 | @end defopt | |
1067 | ||
1068 | @defun special-display-p buffer-name | |
1069 | This function returns non-@code{nil} if displaying a buffer | |
1070 | named @var{buffer-name} with @code{display-buffer} would | |
1071 | create a special frame. The value is @code{t} if it would | |
1072 | use the default frame parameters, or else the specified list | |
1073 | of frame parameters. | |
1074 | @end defun | |
1075 | ||
1076 | @defvar special-display-function | |
1077 | This variable holds the function to call to display a buffer specially. | |
1078 | It receives the buffer as an argument, and should return the window in | |
1079 | which it is displayed. | |
1080 | ||
1081 | The default value of this variable is | |
1082 | @code{special-display-popup-frame}. | |
1083 | @end defvar | |
1084 | ||
1085 | @defun special-display-popup-frame buffer &optional args | |
1086 | This function makes @var{buffer} visible in a frame of its own. If | |
1087 | @var{buffer} is already displayed in a window in some frame, it makes | |
1088 | the frame visible and raises it, to use that window. Otherwise, it | |
1089 | creates a frame that will be dedicated to @var{buffer}. This | |
1090 | function returns the window it used. | |
1091 | ||
1092 | If @var{args} is an alist, it specifies frame parameters for the new | |
1093 | frame. | |
1094 | ||
1095 | If @var{args} is a list whose @sc{car} is a symbol, then @code{(car | |
1096 | @var{args})} is called as a function to actually create and set up the | |
1097 | frame; it is called with @var{buffer} as first argument, and @code{(cdr | |
1098 | @var{args})} as additional arguments. | |
1099 | ||
1100 | This function always uses an existing window displaying @var{buffer}, | |
1101 | whether or not it is in a frame of its own; but if you set up the above | |
1102 | variables in your init file, before @var{buffer} was created, then | |
1103 | presumably the window was previously made by this function. | |
1104 | @end defun | |
1105 | ||
1106 | @defopt special-display-frame-alist | |
1107 | @anchor{Definition of special-display-frame-alist} | |
1108 | This variable holds frame parameters for | |
1109 | @code{special-display-popup-frame} to use when it creates a frame. | |
1110 | @end defopt | |
1111 | ||
1112 | @defopt same-window-buffer-names | |
1113 | A list of buffer names for buffers that should be displayed in the | |
1114 | selected window. If the buffer's name is in this list, | |
1115 | @code{display-buffer} handles the buffer by switching to it in the | |
1116 | selected window. | |
1117 | @end defopt | |
1118 | ||
1119 | @defopt same-window-regexps | |
1120 | A list of regular expressions that specify buffers that should be | |
1121 | displayed in the selected window. If the buffer's name matches any of | |
1122 | the regular expressions in this list, @code{display-buffer} handles the | |
1123 | buffer by switching to it in the selected window. | |
1124 | @end defopt | |
1125 | ||
1126 | @defun same-window-p buffer-name | |
1127 | This function returns @code{t} if displaying a buffer | |
1128 | named @var{buffer-name} with @code{display-buffer} would | |
1129 | put it in the selected window. | |
1130 | @end defun | |
1131 | ||
1132 | @c Emacs 19 feature | |
1133 | @defvar display-buffer-function | |
1134 | This variable is the most flexible way to customize the behavior of | |
1135 | @code{display-buffer}. If it is non-@code{nil}, it should be a function | |
1136 | that @code{display-buffer} calls to do the work. The function should | |
1137 | accept two arguments, the first two arguments that @code{display-buffer} | |
1138 | received. It should choose or create a window, display the specified | |
1139 | buffer in it, and then return the window. | |
1140 | ||
1141 | This hook takes precedence over all the other options and hooks | |
1142 | described above. | |
1143 | @end defvar | |
1144 | ||
1145 | @c Emacs 19 feature | |
1146 | @cindex dedicated window | |
1147 | A window can be marked as ``dedicated'' to its buffer. Then | |
1148 | @code{display-buffer} will not try to use that window to display any | |
1149 | other buffer. | |
1150 | ||
1151 | @defun window-dedicated-p window | |
1152 | This function returns non-@code{nil} if @var{window} is marked as | |
1153 | dedicated; otherwise @code{nil}. | |
1154 | @end defun | |
1155 | ||
1156 | @defun set-window-dedicated-p window flag | |
1157 | This function marks @var{window} as dedicated if @var{flag} is | |
1158 | non-@code{nil}, and nondedicated otherwise. | |
1159 | @end defun | |
1160 | ||
1161 | @node Window Point | |
1162 | @section Windows and Point | |
1163 | @cindex window position | |
1164 | @cindex window point | |
1165 | @cindex position in window | |
1166 | @cindex point in window | |
1167 | ||
1168 | Each window has its own value of point, independent of the value of | |
1169 | point in other windows displaying the same buffer. This makes it useful | |
1170 | to have multiple windows showing one buffer. | |
1171 | ||
1172 | @itemize @bullet | |
1173 | @item | |
1174 | The window point is established when a window is first created; it is | |
1175 | initialized from the buffer's point, or from the window point of another | |
1176 | window opened on the buffer if such a window exists. | |
1177 | ||
1178 | @item | |
1179 | Selecting a window sets the value of point in its buffer from the | |
1180 | window's value of point. Conversely, deselecting a window sets the | |
1181 | window's value of point from that of the buffer. Thus, when you switch | |
1182 | between windows that display a given buffer, the point value for the | |
1183 | selected window is in effect in the buffer, while the point values for | |
1184 | the other windows are stored in those windows. | |
1185 | ||
1186 | @item | |
1187 | As long as the selected window displays the current buffer, the window's | |
1188 | point and the buffer's point always move together; they remain equal. | |
1189 | @end itemize | |
1190 | ||
1191 | @noindent | |
1192 | @xref{Positions}, for more details on buffer positions. | |
1193 | ||
1194 | @cindex cursor | |
1195 | As far as the user is concerned, point is where the cursor is, and | |
1196 | when the user switches to another buffer, the cursor jumps to the | |
1197 | position of point in that buffer. | |
1198 | ||
1199 | @defun window-point &optional window | |
1200 | This function returns the current position of point in @var{window}. | |
1201 | For a nonselected window, this is the value point would have (in that | |
1202 | window's buffer) if that window were selected. If @var{window} is | |
1203 | @code{nil}, the selected window is used. | |
1204 | ||
1205 | When @var{window} is the selected window and its buffer is also the | |
1206 | current buffer, the value returned is the same as point in that buffer. | |
1207 | ||
1208 | Strictly speaking, it would be more correct to return the | |
1209 | ``top-level'' value of point, outside of any @code{save-excursion} | |
1210 | forms. But that value is hard to find. | |
1211 | @end defun | |
1212 | ||
1213 | @defun set-window-point window position | |
1214 | This function positions point in @var{window} at position | |
1215 | @var{position} in @var{window}'s buffer. It returns @var{position}. | |
1216 | ||
1217 | If @var{window} is selected, and its buffer is current, | |
1218 | this simply does @code{goto-char}. | |
1219 | @end defun | |
1220 | ||
1221 | @node Window Start | |
1222 | @section The Window Start Position | |
1223 | @cindex window start position | |
1224 | ||
1225 | Each window contains a marker used to keep track of a buffer position | |
1226 | that specifies where in the buffer display should start. This position | |
1227 | is called the @dfn{display-start} position of the window (or just the | |
1228 | @dfn{start}). The character after this position is the one that appears | |
1229 | at the upper left corner of the window. It is usually, but not | |
1230 | inevitably, at the beginning of a text line. | |
1231 | ||
1232 | @defun window-start &optional window | |
1233 | @cindex window top line | |
1234 | This function returns the display-start position of window | |
1235 | @var{window}. If @var{window} is @code{nil}, the selected window is | |
1236 | used. For example, | |
1237 | ||
1238 | @example | |
1239 | @group | |
1240 | (window-start) | |
1241 | @result{} 7058 | |
1242 | @end group | |
1243 | @end example | |
1244 | ||
1245 | When you create a window, or display a different buffer in it, the | |
1246 | display-start position is set to a display-start position recently used | |
1247 | for the same buffer, or 1 if the buffer doesn't have any. | |
1248 | ||
1249 | Redisplay updates the window-start position (if you have not specified | |
1250 | it explicitly since the previous redisplay)---for example, to make sure | |
1251 | point appears on the screen. Nothing except redisplay automatically | |
1252 | changes the window-start position; if you move point, do not expect the | |
1253 | window-start position to change in response until after the next | |
1254 | redisplay. | |
1255 | ||
1256 | For a realistic example of using @code{window-start}, see the | |
1257 | description of @code{count-lines}. @xref{Definition of count-lines}. | |
1258 | @end defun | |
1259 | ||
1260 | @defun window-end &optional window update | |
1261 | This function returns the position of the end of the display in window | |
1262 | @var{window}. If @var{window} is @code{nil}, the selected window is | |
1263 | used. | |
1264 | ||
1265 | Simply changing the buffer text or moving point does not update the | |
1266 | value that @code{window-end} returns. The value is updated only when | |
1267 | Emacs redisplays and redisplay completes without being preempted. | |
1268 | ||
1269 | If the last redisplay of @var{window} was preempted, and did not finish, | |
1270 | Emacs does not know the position of the end of display in that window. | |
1271 | In that case, this function returns @code{nil}. | |
1272 | ||
1273 | If @var{update} is non-@code{nil}, @code{window-end} always returns an | |
1274 | up-to-date value for where the window ends, based on the current | |
1275 | @code{window-start} value. If the saved value is valid, | |
1276 | @code{window-end} returns that; otherwise it computes the correct | |
1277 | value by scanning the buffer text. | |
1278 | ||
1279 | Even if @var{update} is non-@code{nil}, @code{window-end} does not | |
1280 | attempt to scroll the display if point has moved off the screen, the | |
1281 | way real redisplay would do. It does not alter the | |
1282 | @code{window-start} value. In effect, it reports where the displayed | |
1283 | text will end if scrolling is not required. | |
1284 | @end defun | |
1285 | ||
1286 | @defun set-window-start window position &optional noforce | |
1287 | This function sets the display-start position of @var{window} to | |
1288 | @var{position} in @var{window}'s buffer. It returns @var{position}. | |
1289 | ||
1290 | The display routines insist that the position of point be visible when a | |
1291 | buffer is displayed. Normally, they change the display-start position | |
1292 | (that is, scroll the window) whenever necessary to make point visible. | |
1293 | However, if you specify the start position with this function using | |
1294 | @code{nil} for @var{noforce}, it means you want display to start at | |
1295 | @var{position} even if that would put the location of point off the | |
1296 | screen. If this does place point off screen, the display routines move | |
1297 | point to the left margin on the middle line in the window. | |
1298 | ||
1299 | For example, if point @w{is 1} and you set the start of the window @w{to | |
1300 | 2}, then point would be ``above'' the top of the window. The display | |
1301 | routines will automatically move point if it is still 1 when redisplay | |
1302 | occurs. Here is an example: | |
1303 | ||
1304 | @example | |
1305 | @group | |
1306 | ;; @r{Here is what @samp{foo} looks like before executing} | |
1307 | ;; @r{the @code{set-window-start} expression.} | |
1308 | @end group | |
1309 | ||
1310 | @group | |
1311 | ---------- Buffer: foo ---------- | |
1312 | @point{}This is the contents of buffer foo. | |
1313 | 2 | |
1314 | 3 | |
1315 | 4 | |
1316 | 5 | |
1317 | 6 | |
1318 | ---------- Buffer: foo ---------- | |
1319 | @end group | |
1320 | ||
1321 | @group | |
1322 | (set-window-start | |
1323 | (selected-window) | |
1324 | (1+ (window-start))) | |
1325 | @result{} 2 | |
1326 | @end group | |
1327 | ||
1328 | @group | |
1329 | ;; @r{Here is what @samp{foo} looks like after executing} | |
1330 | ;; @r{the @code{set-window-start} expression.} | |
1331 | ---------- Buffer: foo ---------- | |
1332 | his is the contents of buffer foo. | |
1333 | 2 | |
1334 | 3 | |
1335 | @point{}4 | |
1336 | 5 | |
1337 | 6 | |
1338 | ---------- Buffer: foo ---------- | |
1339 | @end group | |
1340 | @end example | |
1341 | ||
1342 | If @var{noforce} is non-@code{nil}, and @var{position} would place point | |
1343 | off screen at the next redisplay, then redisplay computes a new window-start | |
1344 | position that works well with point, and thus @var{position} is not used. | |
1345 | @end defun | |
1346 | ||
1347 | @defun pos-visible-in-window-p &optional position window partially | |
1348 | This function returns non-@code{nil} if @var{position} is within the | |
1349 | range of text currently visible on the screen in @var{window}. It | |
1350 | returns @code{nil} if @var{position} is scrolled vertically out of | |
1351 | view. Locations that are partially obscured are not considered | |
1352 | visible unless @var{partially} is non-@code{nil}. The argument | |
1353 | @var{position} defaults to the current position of point in | |
1354 | @var{window}; @var{window}, to the selected window. | |
1355 | ||
1356 | If @var{position} is @code{t}, that means to check the last visible | |
1357 | position in @var{window}. | |
1358 | ||
1359 | The @code{pos-visible-in-window-p} function considers only vertical | |
1360 | scrolling. If @var{position} is out of view only because @var{window} | |
1361 | has been scrolled horizontally, @code{pos-visible-in-window-p} returns | |
1362 | non-@code{nil} anyway. @xref{Horizontal Scrolling}. | |
1363 | ||
1364 | If @var{position} is visible, @code{pos-visible-in-window-p} returns | |
1365 | @code{t} if @var{partially} is @code{nil}; if @var{partially} is | |
1366 | non-@code{nil}, and the character after @var{position} is fully | |
1367 | visible, it returns a list of the form @code{(@var{x} @var{y})}, where | |
1368 | @var{x} and @var{y} are the pixel coordinates relative to the top left | |
1369 | corner of the window; otherwise it returns an extended list of the | |
1370 | form @code{(@var{x} @var{y} @var{rtop} @var{rbot} @var{rowh} | |
1371 | @var{vpos})}, where the @var{rtop} and @var{rbot} specify the number | |
1372 | of off-window pixels at the top and bottom of the row at | |
1373 | @var{position}, @var{rowh} specifies the visible height of that row, | |
1374 | and @var{vpos} specifies the vertical position (zero-based row number) | |
1375 | of that row. | |
1376 | ||
1377 | Here is an example: | |
1378 | ||
1379 | @example | |
1380 | @group | |
1381 | ;; @r{If point is off the screen now, recenter it now.} | |
1382 | (or (pos-visible-in-window-p | |
1383 | (point) (selected-window)) | |
1384 | (recenter 0)) | |
1385 | @end group | |
1386 | @end example | |
1387 | @end defun | |
1388 | ||
1389 | @defun window-line-height &optional line window | |
1390 | This function returns information about text line @var{line} in @var{window}. | |
1391 | If @var{line} is one of @code{header-line} or @code{mode-line}, | |
1392 | @code{window-line-height} returns information about the corresponding | |
1393 | line of the window. Otherwise, @var{line} is a text line number | |
1394 | starting from 0. A negative number counts from the end of the window. | |
1395 | The argument @var{line} defaults to the current line in @var{window}; | |
1396 | @var{window}, to the selected window. | |
1397 | ||
1398 | If the display is not up to date, @code{window-line-height} returns | |
1399 | @code{nil}. In that case, @code{pos-visible-in-window-p} may be used | |
1400 | to obtain related information. | |
1401 | ||
1402 | If there is no line corresponding to the specified @var{line}, | |
1403 | @code{window-line-height} returns @code{nil}. Otherwise, it returns | |
1404 | a list @code{(@var{height} @var{vpos} @var{ypos} @var{offbot})}, | |
1405 | where @var{height} is the height in pixels of the visible part of the | |
1406 | line, @var{vpos} and @var{ypos} are the vertical position in lines and | |
1407 | pixels of the line relative to the top of the first text line, and | |
1408 | @var{offbot} is the number of off-window pixels at the bottom of the | |
1409 | text line. If there are off-window pixels at the top of the (first) | |
1410 | text line, @var{ypos} is negative. | |
1411 | @end defun | |
1412 | ||
1413 | @node Textual Scrolling | |
1414 | @section Textual Scrolling | |
1415 | @cindex textual scrolling | |
1416 | @cindex scrolling textually | |
1417 | ||
1418 | @dfn{Textual scrolling} means moving the text up or down through a | |
1419 | window. It works by changing the value of the window's display-start | |
1420 | location. It may also change the value of @code{window-point} to keep | |
1421 | point on the screen. | |
1422 | ||
1423 | Textual scrolling was formerly called ``vertical scrolling,'' but we | |
1424 | changed its name to distinguish it from the new vertical fractional | |
1425 | scrolling feature (@pxref{Vertical Scrolling}). | |
1426 | ||
1427 | In the commands @code{scroll-up} and @code{scroll-down}, the directions | |
1428 | ``up'' and ``down'' refer to the motion of the text in the buffer at which | |
1429 | you are looking through the window. Imagine that the text is | |
1430 | written on a long roll of paper and that the scrolling commands move the | |
1431 | paper up and down. Thus, if you are looking at text in the middle of a | |
1432 | buffer and repeatedly call @code{scroll-down}, you will eventually see | |
1433 | the beginning of the buffer. | |
1434 | ||
1435 | Some people have urged that the opposite convention be used: they | |
1436 | imagine that the window moves over text that remains in place. Then | |
1437 | ``down'' commands would take you to the end of the buffer. This view is | |
1438 | more consistent with the actual relationship between windows and the | |
1439 | text in the buffer, but it is less like what the user sees. The | |
1440 | position of a window on the terminal does not move, and short scrolling | |
1441 | commands clearly move the text up or down on the screen. We have chosen | |
1442 | names that fit the user's point of view. | |
1443 | ||
1444 | The textual scrolling functions (aside from | |
1445 | @code{scroll-other-window}) have unpredictable results if the current | |
1446 | buffer is different from the buffer that is displayed in the selected | |
1447 | window. @xref{Current Buffer}. | |
1448 | ||
1449 | If the window contains a row which is taller than the height of the | |
1450 | window (for example in the presence of a large image), the scroll | |
1451 | functions will adjust the window vscroll to scroll the partially | |
1452 | visible row. To disable this feature, Lisp code may bind the variable | |
1453 | `auto-window-vscroll' to @code{nil} (@pxref{Vertical Scrolling}). | |
1454 | ||
1455 | @deffn Command scroll-up &optional count | |
1456 | This function scrolls the text in the selected window upward | |
1457 | @var{count} lines. If @var{count} is negative, scrolling is actually | |
1458 | downward. | |
1459 | ||
1460 | If @var{count} is @code{nil} (or omitted), then the length of scroll | |
1461 | is @code{next-screen-context-lines} lines less than the usable height of | |
1462 | the window (not counting its mode line). | |
1463 | ||
1464 | @code{scroll-up} returns @code{nil}, unless it gets an error | |
1465 | because it can't scroll any further. | |
1466 | @end deffn | |
1467 | ||
1468 | @deffn Command scroll-down &optional count | |
1469 | This function scrolls the text in the selected window downward | |
1470 | @var{count} lines. If @var{count} is negative, scrolling is actually | |
1471 | upward. | |
1472 | ||
1473 | If @var{count} is omitted or @code{nil}, then the length of the scroll | |
1474 | is @code{next-screen-context-lines} lines less than the usable height of | |
1475 | the window (not counting its mode line). | |
1476 | ||
1477 | @code{scroll-down} returns @code{nil}, unless it gets an error because | |
1478 | it can't scroll any further. | |
1479 | @end deffn | |
1480 | ||
1481 | @deffn Command scroll-other-window &optional count | |
1482 | This function scrolls the text in another window upward @var{count} | |
1483 | lines. Negative values of @var{count}, or @code{nil}, are handled | |
1484 | as in @code{scroll-up}. | |
1485 | ||
1486 | You can specify which buffer to scroll by setting the variable | |
1487 | @code{other-window-scroll-buffer} to a buffer. If that buffer isn't | |
1488 | already displayed, @code{scroll-other-window} displays it in some | |
1489 | window. | |
1490 | ||
1491 | When the selected window is the minibuffer, the next window is normally | |
1492 | the one at the top left corner. You can specify a different window to | |
1493 | scroll, when the minibuffer is selected, by setting the variable | |
1494 | @code{minibuffer-scroll-window}. This variable has no effect when any | |
1495 | other window is selected. When it is non-@code{nil} and the | |
1496 | minibuffer is selected, it takes precedence over | |
1497 | @code{other-window-scroll-buffer}. @xref{Definition of | |
1498 | minibuffer-scroll-window}. | |
1499 | ||
1500 | When the minibuffer is active, it is the next window if the selected | |
1501 | window is the one at the bottom right corner. In this case, | |
1502 | @code{scroll-other-window} attempts to scroll the minibuffer. If the | |
1503 | minibuffer contains just one line, it has nowhere to scroll to, so the | |
1504 | line reappears after the echo area momentarily displays the message | |
1505 | @samp{Beginning of buffer}. | |
1506 | @end deffn | |
1507 | ||
1508 | @c Emacs 19 feature | |
1509 | @defvar other-window-scroll-buffer | |
1510 | If this variable is non-@code{nil}, it tells @code{scroll-other-window} | |
1511 | which buffer to scroll. | |
1512 | @end defvar | |
1513 | ||
1514 | @defopt scroll-margin | |
1515 | This option specifies the size of the scroll margin---a minimum number | |
1516 | of lines between point and the top or bottom of a window. Whenever | |
1517 | point gets within this many lines of the top or bottom of the window, | |
1518 | redisplay scrolls the text automatically (if possible) to move point | |
1519 | out of the margin, closer to the center of the window. | |
1520 | @end defopt | |
1521 | ||
1522 | @defopt scroll-conservatively | |
1523 | This variable controls how scrolling is done automatically when point | |
1524 | moves off the screen (or into the scroll margin). If the value is a | |
1525 | positive integer @var{n}, then redisplay scrolls the text up to | |
1526 | @var{n} lines in either direction, if that will bring point back into | |
1527 | proper view. This action is called @dfn{conservative scrolling}. | |
1528 | Otherwise, scrolling happens in the usual way, under the control of | |
1529 | other variables such as @code{scroll-up-aggressively} and | |
1530 | @code{scroll-down-aggressively}. | |
1531 | ||
1532 | The default value is zero, which means that conservative scrolling | |
1533 | never happens. | |
1534 | @end defopt | |
1535 | ||
1536 | @defopt scroll-down-aggressively | |
1537 | The value of this variable should be either @code{nil} or a fraction | |
1538 | @var{f} between 0 and 1. If it is a fraction, that specifies where on | |
1539 | the screen to put point when scrolling down. More precisely, when a | |
1540 | window scrolls down because point is above the window start, the new | |
1541 | start position is chosen to put point @var{f} part of the window | |
1542 | height from the top. The larger @var{f}, the more aggressive the | |
1543 | scrolling. | |
1544 | ||
1545 | A value of @code{nil} is equivalent to .5, since its effect is to center | |
1546 | point. This variable automatically becomes buffer-local when set in any | |
1547 | fashion. | |
1548 | @end defopt | |
1549 | ||
1550 | @defopt scroll-up-aggressively | |
1551 | Likewise, for scrolling up. The value, @var{f}, specifies how far | |
1552 | point should be placed from the bottom of the window; thus, as with | |
1553 | @code{scroll-up-aggressively}, a larger value scrolls more aggressively. | |
1554 | @end defopt | |
1555 | ||
1556 | @defopt scroll-step | |
1557 | This variable is an older variant of @code{scroll-conservatively}. The | |
1558 | difference is that it if its value is @var{n}, that permits scrolling | |
1559 | only by precisely @var{n} lines, not a smaller number. This feature | |
1560 | does not work with @code{scroll-margin}. The default value is zero. | |
1561 | @end defopt | |
1562 | ||
1563 | @defopt scroll-preserve-screen-position | |
1564 | If this option is @code{t}, scrolling which would move the current | |
1565 | point position out of the window chooses the new position of point | |
1566 | so that the vertical position of the cursor is unchanged, if possible. | |
1567 | ||
1568 | If it is non-@code{nil} and not @code{t}, then the scrolling functions | |
1569 | always preserve the vertical position of point, if possible. | |
1570 | @end defopt | |
1571 | ||
1572 | @defopt next-screen-context-lines | |
1573 | The value of this variable is the number of lines of continuity to | |
1574 | retain when scrolling by full screens. For example, @code{scroll-up} | |
1575 | with an argument of @code{nil} scrolls so that this many lines at the | |
1576 | bottom of the window appear instead at the top. The default value is | |
1577 | @code{2}. | |
1578 | @end defopt | |
1579 | ||
1580 | @deffn Command recenter &optional count | |
1581 | @cindex centering point | |
1582 | This function scrolls the text in the selected window so that point is | |
1583 | displayed at a specified vertical position within the window. It does | |
1584 | not ``move point'' with respect to the text. | |
1585 | ||
1586 | If @var{count} is a nonnegative number, that puts the line containing | |
1587 | point @var{count} lines down from the top of the window. If | |
1588 | @var{count} is a negative number, then it counts upward from the | |
1589 | bottom of the window, so that @minus{}1 stands for the last usable | |
1590 | line in the window. If @var{count} is a non-@code{nil} list, then it | |
1591 | stands for the line in the middle of the window. | |
1592 | ||
1593 | If @var{count} is @code{nil}, @code{recenter} puts the line containing | |
1594 | point in the middle of the window, then clears and redisplays the entire | |
1595 | selected frame. | |
1596 | ||
1597 | When @code{recenter} is called interactively, @var{count} is the raw | |
1598 | prefix argument. Thus, typing @kbd{C-u} as the prefix sets the | |
1599 | @var{count} to a non-@code{nil} list, while typing @kbd{C-u 4} sets | |
1600 | @var{count} to 4, which positions the current line four lines from the | |
1601 | top. | |
1602 | ||
1603 | With an argument of zero, @code{recenter} positions the current line at | |
1604 | the top of the window. This action is so handy that some people make a | |
1605 | separate key binding to do this. For example, | |
1606 | ||
1607 | @example | |
1608 | @group | |
1609 | (defun line-to-top-of-window () | |
1610 | "Scroll current line to top of window. | |
1611 | Replaces three keystroke sequence C-u 0 C-l." | |
1612 | (interactive) | |
1613 | (recenter 0)) | |
1614 | ||
1615 | (global-set-key [kp-multiply] 'line-to-top-of-window) | |
1616 | @end group | |
1617 | @end example | |
1618 | @end deffn | |
1619 | ||
1620 | @node Vertical Scrolling | |
1621 | @section Vertical Fractional Scrolling | |
1622 | @cindex vertical fractional scrolling | |
1623 | ||
1624 | @dfn{Vertical fractional scrolling} means shifting the image in the | |
1625 | window up or down by a specified multiple or fraction of a line. | |
1626 | Each window has a @dfn{vertical scroll position}, | |
1627 | which is a number, never less than zero. It specifies how far to raise | |
1628 | the contents of the window. Raising the window contents generally makes | |
1629 | all or part of some lines disappear off the top, and all or part of some | |
1630 | other lines appear at the bottom. The usual value is zero. | |
1631 | ||
1632 | The vertical scroll position is measured in units of the normal line | |
1633 | height, which is the height of the default font. Thus, if the value is | |
1634 | .5, that means the window contents are scrolled up half the normal line | |
1635 | height. If it is 3.3, that means the window contents are scrolled up | |
1636 | somewhat over three times the normal line height. | |
1637 | ||
1638 | What fraction of a line the vertical scrolling covers, or how many | |
1639 | lines, depends on what the lines contain. A value of .5 could scroll a | |
1640 | line whose height is very short off the screen, while a value of 3.3 | |
1641 | could scroll just part of the way through a tall line or an image. | |
1642 | ||
1643 | @defun window-vscroll &optional window pixels-p | |
1644 | This function returns the current vertical scroll position of | |
1645 | @var{window}. If @var{window} is @code{nil}, the selected window is | |
1646 | used. If @var{pixels-p} is non-@code{nil}, the return value is | |
1647 | measured in pixels, rather than in units of the normal line height. | |
1648 | ||
1649 | @example | |
1650 | @group | |
1651 | (window-vscroll) | |
1652 | @result{} 0 | |
1653 | @end group | |
1654 | @end example | |
1655 | @end defun | |
1656 | ||
1657 | @defun set-window-vscroll window lines &optional pixels-p | |
1658 | This function sets @var{window}'s vertical scroll position to | |
1659 | @var{lines}. The argument @var{lines} should be zero or positive; if | |
1660 | not, it is taken as zero. | |
1661 | ||
1662 | If @var{window} is @code{nil}, the selected window is used. | |
1663 | ||
1664 | The actual vertical scroll position must always correspond | |
1665 | to an integral number of pixels, so the value you specify | |
1666 | is rounded accordingly. | |
1667 | ||
1668 | The return value is the result of this rounding. | |
1669 | ||
1670 | @example | |
1671 | @group | |
1672 | (set-window-vscroll (selected-window) 1.2) | |
1673 | @result{} 1.13 | |
1674 | @end group | |
1675 | @end example | |
1676 | ||
1677 | If @var{pixels-p} is non-@code{nil}, @var{lines} specifies a number of | |
1678 | pixels. In this case, the return value is @var{lines}. | |
1679 | @end defun | |
1680 | ||
1681 | @defvar auto-window-vscroll | |
1682 | If this variable is non-@code{nil}, the line-move, scroll-up, and | |
1683 | scroll-down functions will automatically modify the window vscroll to | |
1684 | scroll through display rows that are taller that the height of the | |
1685 | window, for example in the presence of large images. | |
1686 | @end defvar | |
1687 | ||
1688 | @node Horizontal Scrolling | |
1689 | @section Horizontal Scrolling | |
1690 | @cindex horizontal scrolling | |
1691 | ||
1692 | @dfn{Horizontal scrolling} means shifting the image in the window left | |
1693 | or right by a specified multiple of the normal character width. Each | |
1694 | window has a @dfn{horizontal scroll position}, which is a number, never | |
1695 | less than zero. It specifies how far to shift the contents left. | |
1696 | Shifting the window contents left generally makes all or part of some | |
1697 | characters disappear off the left, and all or part of some other | |
1698 | characters appear at the right. The usual value is zero. | |
1699 | ||
1700 | The horizontal scroll position is measured in units of the normal | |
1701 | character width, which is the width of space in the default font. Thus, | |
1702 | if the value is 5, that means the window contents are scrolled left by 5 | |
1703 | times the normal character width. How many characters actually | |
1704 | disappear off to the left depends on their width, and could vary from | |
1705 | line to line. | |
1706 | ||
1707 | Because we read from side to side in the ``inner loop,'' and from top | |
1708 | to bottom in the ``outer loop,'' the effect of horizontal scrolling is | |
1709 | not like that of textual or vertical scrolling. Textual scrolling | |
1710 | involves selection of a portion of text to display, and vertical | |
1711 | scrolling moves the window contents contiguously; but horizontal | |
1712 | scrolling causes part of @emph{each line} to go off screen. | |
1713 | ||
1714 | Usually, no horizontal scrolling is in effect; then the leftmost | |
1715 | column is at the left edge of the window. In this state, scrolling to | |
1716 | the right is meaningless, since there is no data to the left of the edge | |
1717 | to be revealed by it; so this is not allowed. Scrolling to the left is | |
1718 | allowed; it scrolls the first columns of text off the edge of the window | |
1719 | and can reveal additional columns on the right that were truncated | |
1720 | before. Once a window has a nonzero amount of leftward horizontal | |
1721 | scrolling, you can scroll it back to the right, but only so far as to | |
1722 | reduce the net horizontal scroll to zero. There is no limit to how far | |
1723 | left you can scroll, but eventually all the text will disappear off the | |
1724 | left edge. | |
1725 | ||
1726 | @vindex auto-hscroll-mode | |
1727 | If @code{auto-hscroll-mode} is set, redisplay automatically alters | |
1728 | the horizontal scrolling of a window as necessary to ensure that point | |
1729 | is always visible. However, you can still set the horizontal | |
1730 | scrolling value explicitly. The value you specify serves as a lower | |
1731 | bound for automatic scrolling, i.e. automatic scrolling will not | |
1732 | scroll a window to a column less than the specified one. | |
1733 | ||
1734 | @deffn Command scroll-left &optional count set-minimum | |
1735 | This function scrolls the selected window @var{count} columns to the | |
1736 | left (or to the right if @var{count} is negative). The default | |
1737 | for @var{count} is the window width, minus 2. | |
1738 | ||
1739 | The return value is the total amount of leftward horizontal scrolling in | |
1740 | effect after the change---just like the value returned by | |
1741 | @code{window-hscroll} (below). | |
1742 | ||
1743 | Once you scroll a window as far right as it can go, back to its normal | |
1744 | position where the total leftward scrolling is zero, attempts to scroll | |
1745 | any farther right have no effect. | |
1746 | ||
1747 | If @var{set-minimum} is non-@code{nil}, the new scroll amount becomes | |
1748 | the lower bound for automatic scrolling; that is, automatic scrolling | |
1749 | will not scroll a window to a column less than the value returned by | |
1750 | this function. Interactive calls pass non-@code{nil} for | |
1751 | @var{set-minimum}. | |
1752 | @end deffn | |
1753 | ||
1754 | @deffn Command scroll-right &optional count set-minimum | |
1755 | This function scrolls the selected window @var{count} columns to the | |
1756 | right (or to the left if @var{count} is negative). The default | |
1757 | for @var{count} is the window width, minus 2. Aside from the direction | |
1758 | of scrolling, this works just like @code{scroll-left}. | |
1759 | @end deffn | |
1760 | ||
1761 | @defun window-hscroll &optional window | |
1762 | This function returns the total leftward horizontal scrolling of | |
1763 | @var{window}---the number of columns by which the text in @var{window} | |
1764 | is scrolled left past the left margin. | |
1765 | ||
1766 | The value is never negative. It is zero when no horizontal scrolling | |
1767 | has been done in @var{window} (which is usually the case). | |
1768 | ||
1769 | If @var{window} is @code{nil}, the selected window is used. | |
1770 | ||
1771 | @example | |
1772 | @group | |
1773 | (window-hscroll) | |
1774 | @result{} 0 | |
1775 | @end group | |
1776 | @group | |
1777 | (scroll-left 5) | |
1778 | @result{} 5 | |
1779 | @end group | |
1780 | @group | |
1781 | (window-hscroll) | |
1782 | @result{} 5 | |
1783 | @end group | |
1784 | @end example | |
1785 | @end defun | |
1786 | ||
1787 | @defun set-window-hscroll window columns | |
1788 | This function sets horizontal scrolling of @var{window}. The value of | |
1789 | @var{columns} specifies the amount of scrolling, in terms of columns | |
1790 | from the left margin. The argument @var{columns} should be zero or | |
1791 | positive; if not, it is taken as zero. Fractional values of | |
1792 | @var{columns} are not supported at present. | |
1793 | ||
1794 | Note that @code{set-window-hscroll} may appear not to work if you test | |
1795 | it by evaluating a call with @kbd{M-:} in a simple way. What happens | |
1796 | is that the function sets the horizontal scroll value and returns, but | |
1797 | then redisplay adjusts the horizontal scrolling to make point visible, | |
1798 | and this overrides what the function did. You can observe the | |
1799 | function's effect if you call it while point is sufficiently far from | |
1800 | the left margin that it will remain visible. | |
1801 | ||
1802 | The value returned is @var{columns}. | |
1803 | ||
1804 | @example | |
1805 | @group | |
1806 | (set-window-hscroll (selected-window) 10) | |
1807 | @result{} 10 | |
1808 | @end group | |
1809 | @end example | |
1810 | @end defun | |
1811 | ||
1812 | Here is how you can determine whether a given position @var{position} | |
1813 | is off the screen due to horizontal scrolling: | |
1814 | ||
1815 | @example | |
1816 | @group | |
1817 | (defun hscroll-on-screen (window position) | |
1818 | (save-excursion | |
1819 | (goto-char position) | |
1820 | (and | |
1821 | (>= (- (current-column) (window-hscroll window)) 0) | |
1822 | (< (- (current-column) (window-hscroll window)) | |
1823 | (window-width window))))) | |
1824 | @end group | |
1825 | @end example | |
1826 | ||
1827 | @node Size of Window | |
1828 | @section The Size of a Window | |
1829 | @cindex window size | |
1830 | @cindex size of window | |
1831 | ||
1832 | An Emacs window is rectangular, and its size information consists of | |
1833 | the height (the number of lines) and the width (the number of character | |
1834 | positions in each line). The mode line is included in the height. But | |
1835 | the width does not count the scroll bar or the column of @samp{|} | |
1836 | characters that separates side-by-side windows. | |
1837 | ||
1838 | The following three functions return size information about a window: | |
1839 | ||
1840 | @defun window-height &optional window | |
1841 | This function returns the number of lines in @var{window}, including | |
1842 | its mode line and header line, if any. If @var{window} fills its | |
1843 | entire frame except for the echo area, this is typically one less than | |
1844 | the value of @code{frame-height} on that frame. | |
1845 | ||
1846 | If @var{window} is @code{nil}, the function uses the selected window. | |
1847 | ||
1848 | @example | |
1849 | @group | |
1850 | (window-height) | |
1851 | @result{} 23 | |
1852 | @end group | |
1853 | @group | |
1854 | (split-window-vertically) | |
1855 | @result{} #<window 4 on windows.texi> | |
1856 | @end group | |
1857 | @group | |
1858 | (window-height) | |
1859 | @result{} 11 | |
1860 | @end group | |
1861 | @end example | |
1862 | @end defun | |
1863 | ||
1864 | @defun window-body-height &optional window | |
1865 | Like @code{window-height} but the value does not include the | |
1866 | mode line (if any) or the header line (if any). | |
1867 | @end defun | |
1868 | ||
1869 | @defun window-width &optional window | |
1870 | This function returns the number of columns in @var{window}. If | |
1871 | @var{window} fills its entire frame, this is the same as the value of | |
1872 | @code{frame-width} on that frame. The width does not include the | |
1873 | window's scroll bar or the column of @samp{|} characters that separates | |
1874 | side-by-side windows. | |
1875 | ||
1876 | If @var{window} is @code{nil}, the function uses the selected window. | |
1877 | ||
1878 | @example | |
1879 | @group | |
1880 | (window-width) | |
1881 | @result{} 80 | |
1882 | @end group | |
1883 | @end example | |
1884 | @end defun | |
1885 | ||
1886 | @defun window-full-width-p &optional window | |
1887 | This function returns non-@code{nil} if @var{window} is as wide as | |
1888 | the frame that contains it; otherwise @code{nil}. | |
1889 | If @var{window} is @code{nil}, the function uses the selected window. | |
1890 | @end defun | |
1891 | ||
1892 | @defun window-edges &optional window | |
1893 | This function returns a list of the edge coordinates of @var{window}. | |
1894 | If @var{window} is @code{nil}, the selected window is used. | |
1895 | ||
1896 | The order of the list is @code{(@var{left} @var{top} @var{right} | |
1897 | @var{bottom})}, all elements relative to 0, 0 at the top left corner of | |
1898 | the frame. The element @var{right} of the value is one more than the | |
1899 | rightmost column used by @var{window}, and @var{bottom} is one more than | |
1900 | the bottommost row used by @var{window} and its mode-line. | |
1901 | ||
1902 | The edges include the space used by the window's scroll bar, display | |
1903 | margins, fringes, header line, and mode line, if it has them. Also, | |
1904 | if the window has a neighbor on the right, its right edge value | |
1905 | includes the width of the separator line between the window and that | |
1906 | neighbor. Since the width of the window does not include this | |
1907 | separator, the width does not usually equal the difference between the | |
1908 | right and left edges. | |
1909 | @end defun | |
1910 | ||
1911 | @defun window-inside-edges &optional window | |
1912 | This is similar to @code{window-edges}, but the edge values | |
1913 | it returns include only the text area of the window. They | |
1914 | do not include the header line, mode line, scroll bar or | |
1915 | vertical separator, fringes, or display margins. | |
1916 | @end defun | |
1917 | ||
1918 | Here are the results obtained on a typical 24-line terminal with just | |
1919 | one window, with menu bar enabled: | |
1920 | ||
1921 | @example | |
1922 | @group | |
1923 | (window-edges (selected-window)) | |
1924 | @result{} (0 1 80 23) | |
1925 | @end group | |
1926 | @group | |
1927 | (window-inside-edges (selected-window)) | |
1928 | @result{} (0 1 80 22) | |
1929 | @end group | |
1930 | @end example | |
1931 | ||
1932 | @noindent | |
1933 | The bottom edge is at line 23 because the last line is the echo area. | |
1934 | The bottom inside edge is at line 22, which is the window's mode line. | |
1935 | ||
1936 | If @var{window} is at the upper left corner of its frame, and there is | |
1937 | no menu bar, then @var{bottom} returned by @code{window-edges} is the | |
1938 | same as the value of @code{(window-height)}, @var{right} is almost the | |
1939 | same as the value of @code{(window-width)}, and @var{top} and | |
1940 | @var{left} are zero. For example, the edges of the following window | |
1941 | are @w{@samp{0 0 8 5}}. Assuming that the frame has more than 8 | |
1942 | columns, the last column of the window (column 7) holds a border | |
1943 | rather than text. The last row (row 4) holds the mode line, shown | |
1944 | here with @samp{xxxxxxxxx}. | |
1945 | ||
1946 | @example | |
1947 | @group | |
1948 | 0 | |
1949 | _______ | |
1950 | 0 | | | |
1951 | | | | |
1952 | | | | |
1953 | | | | |
1954 | xxxxxxxxx 4 | |
1955 | ||
1956 | 7 | |
1957 | @end group | |
1958 | @end example | |
1959 | ||
1960 | In the following example, let's suppose that the frame is 7 | |
1961 | columns wide. Then the edges of the left window are @w{@samp{0 0 4 3}} | |
1962 | and the edges of the right window are @w{@samp{4 0 7 3}}. | |
1963 | The inside edges of the left window are @w{@samp{0 0 3 2}}, | |
1964 | and the inside edges of the right window are @w{@samp{4 0 7 2}}, | |
1965 | ||
1966 | @example | |
1967 | @group | |
1968 | ___ ___ | |
1969 | | | | | |
1970 | | | | | |
1971 | xxxxxxxxx | |
1972 | ||
1973 | 0 34 7 | |
1974 | @end group | |
1975 | @end example | |
1976 | ||
1977 | @defun window-pixel-edges &optional window | |
1978 | This function is like @code{window-edges} except that, on a graphical | |
1979 | display, the edge values are measured in pixels instead of in | |
1980 | character lines and columns. | |
1981 | @end defun | |
1982 | ||
1983 | @defun window-inside-pixel-edges &optional window | |
1984 | This function is like @code{window-inside-edges} except that, on a | |
1985 | graphical display, the edge values are measured in pixels instead of | |
1986 | in character lines and columns. | |
1987 | @end defun | |
1988 | ||
1989 | @node Resizing Windows | |
1990 | @section Changing the Size of a Window | |
1991 | @cindex window resizing | |
1992 | @cindex resize window | |
1993 | @cindex changing window size | |
1994 | @cindex window size, changing | |
1995 | ||
1996 | The window size functions fall into two classes: high-level commands | |
1997 | that change the size of windows and low-level functions that access | |
1998 | window size. Emacs does not permit overlapping windows or gaps between | |
1999 | windows, so resizing one window affects other windows. | |
2000 | ||
2001 | @deffn Command enlarge-window size &optional horizontal | |
2002 | This function makes the selected window @var{size} lines taller, | |
2003 | stealing lines from neighboring windows. It takes the lines from one | |
2004 | window at a time until that window is used up, then takes from another. | |
2005 | If a window from which lines are stolen shrinks below | |
2006 | @code{window-min-height} lines, that window disappears. | |
2007 | ||
2008 | If @var{horizontal} is non-@code{nil}, this function makes | |
2009 | @var{window} wider by @var{size} columns, stealing columns instead of | |
2010 | lines. If a window from which columns are stolen shrinks below | |
2011 | @code{window-min-width} columns, that window disappears. | |
2012 | ||
2013 | If the requested size would exceed that of the window's frame, then the | |
2014 | function makes the window occupy the entire height (or width) of the | |
2015 | frame. | |
2016 | ||
2017 | If there are various other windows from which lines or columns can be | |
2018 | stolen, and some of them specify fixed size (using | |
2019 | @code{window-size-fixed}, see below), they are left untouched while | |
2020 | other windows are ``robbed.'' If it would be necessary to alter the | |
2021 | size of a fixed-size window, @code{enlarge-window} gets an error | |
2022 | instead. | |
2023 | ||
2024 | If @var{size} is negative, this function shrinks the window by | |
2025 | @minus{}@var{size} lines or columns. If that makes the window smaller | |
2026 | than the minimum size (@code{window-min-height} and | |
2027 | @code{window-min-width}), @code{enlarge-window} deletes the window. | |
2028 | ||
2029 | @code{enlarge-window} returns @code{nil}. | |
2030 | @end deffn | |
2031 | ||
2032 | @deffn Command enlarge-window-horizontally columns | |
2033 | This function makes the selected window @var{columns} wider. | |
2034 | It could be defined as follows: | |
2035 | ||
2036 | @example | |
2037 | @group | |
2038 | (defun enlarge-window-horizontally (columns) | |
2039 | (interactive "p") | |
2040 | (enlarge-window columns t)) | |
2041 | @end group | |
2042 | @end example | |
2043 | @end deffn | |
2044 | ||
2045 | @deffn Command shrink-window size &optional horizontal | |
2046 | This function is like @code{enlarge-window} but negates the argument | |
2047 | @var{size}, making the selected window smaller by giving lines (or | |
2048 | columns) to the other windows. If the window shrinks below | |
2049 | @code{window-min-height} or @code{window-min-width}, then it disappears. | |
2050 | ||
2051 | If @var{size} is negative, the window is enlarged by @minus{}@var{size} | |
2052 | lines or columns. | |
2053 | @end deffn | |
2054 | ||
2055 | @deffn Command shrink-window-horizontally columns | |
2056 | This function makes the selected window @var{columns} narrower. | |
2057 | It could be defined as follows: | |
2058 | ||
2059 | @example | |
2060 | @group | |
2061 | (defun shrink-window-horizontally (columns) | |
2062 | (interactive "p") | |
2063 | (shrink-window columns t)) | |
2064 | @end group | |
2065 | @end example | |
2066 | @end deffn | |
2067 | ||
2068 | @defun adjust-window-trailing-edge window delta horizontal | |
2069 | This function makes the selected window @var{delta} lines taller or | |
2070 | @var{delta} columns wider, by moving the bottom or right edge. This | |
2071 | function does not delete other windows; if it cannot make the | |
2072 | requested size adjustment, it signals an error. On success, this | |
2073 | function returns @code{nil}. | |
2074 | @end defun | |
2075 | ||
2076 | @defun fit-window-to-buffer &optional window max-height min-height | |
2077 | This function makes @var{window} the right height to display its | |
2078 | contents exactly. If @var{window} is omitted or @code{nil}, it uses | |
2079 | the selected window. | |
2080 | ||
2081 | The argument @var{max-height} specifies the maximum height the window | |
2082 | is allowed to be; @code{nil} means use the frame height. The argument | |
2083 | @var{min-height} specifies the minimum height for the window; | |
2084 | @code{nil} means use @code{window-min-height}. All these height | |
2085 | values include the mode-line and/or header-line. | |
2086 | @end defun | |
2087 | ||
2088 | @deffn Command shrink-window-if-larger-than-buffer &optional window | |
2089 | This command shrinks @var{window} vertically to be as small as | |
2090 | possible while still showing the full contents of its buffer---but not | |
2091 | less than @code{window-min-height} lines. If @var{window} is not | |
2092 | given, it defaults to the selected window. | |
2093 | ||
2094 | However, the command does nothing if the window is already too small to | |
2095 | display the whole text of the buffer, or if part of the contents are | |
2096 | currently scrolled off screen, or if the window is not the full width of | |
2097 | its frame, or if the window is the only window in its frame. | |
2098 | ||
2099 | This command returns non-@code{nil} if it actually shrank the window | |
2100 | and @code{nil} otherwise. | |
2101 | @end deffn | |
2102 | ||
2103 | @defvar window-size-fixed | |
2104 | If this variable is non-@code{nil}, in any given buffer, | |
2105 | then the size of any window displaying the buffer remains fixed | |
2106 | unless you explicitly change it or Emacs has no other choice. | |
2107 | ||
2108 | If the value is @code{height}, then only the window's height is fixed; | |
2109 | if the value is @code{width}, then only the window's width is fixed. | |
2110 | Any other non-@code{nil} value fixes both the width and the height. | |
2111 | ||
2112 | This variable automatically becomes buffer-local when set. | |
2113 | ||
2114 | Explicit size-change functions such as @code{enlarge-window} | |
2115 | get an error if they would have to change a window size which is fixed. | |
2116 | Therefore, when you want to change the size of such a window, | |
2117 | you should bind @code{window-size-fixed} to @code{nil}, like this: | |
2118 | ||
2119 | @example | |
2120 | (let ((window-size-fixed nil)) | |
2121 | (enlarge-window 10)) | |
2122 | @end example | |
2123 | ||
2124 | Note that changing the frame size will change the size of a | |
2125 | fixed-size window, if there is no other alternative. | |
2126 | @end defvar | |
2127 | ||
2128 | @cindex minimum window size | |
2129 | The following two variables constrain the window-structure-changing | |
2130 | functions to a minimum height and width. | |
2131 | ||
2132 | @defopt window-min-height | |
2133 | The value of this variable determines how short a window may become | |
2134 | before it is automatically deleted. Making a window smaller than | |
2135 | @code{window-min-height} automatically deletes it, and no window may | |
2136 | be created shorter than this. The default value is 4. | |
2137 | ||
2138 | The absolute minimum window height is one; actions that change window | |
2139 | sizes reset this variable to one if it is less than one. | |
2140 | @end defopt | |
2141 | ||
2142 | @defopt window-min-width | |
2143 | The value of this variable determines how narrow a window may become | |
2144 | before it is automatically deleted. Making a window smaller than | |
2145 | @code{window-min-width} automatically deletes it, and no window may be | |
2146 | created narrower than this. The default value is 10. | |
2147 | ||
2148 | The absolute minimum window width is two; actions that change window | |
2149 | sizes reset this variable to two if it is less than two. | |
2150 | @end defopt | |
2151 | ||
2152 | @node Coordinates and Windows | |
2153 | @section Coordinates and Windows | |
2154 | ||
2155 | This section describes how to relate screen coordinates to windows. | |
2156 | ||
2157 | @defun window-at x y &optional frame | |
2158 | This function returns the window containing the specified cursor | |
2159 | position in the frame @var{frame}. The coordinates @var{x} and @var{y} | |
2160 | are measured in characters and count from the top left corner of the | |
2161 | frame. If they are out of range, @code{window-at} returns @code{nil}. | |
2162 | ||
2163 | If you omit @var{frame}, the selected frame is used. | |
2164 | @end defun | |
2165 | ||
2166 | @defun coordinates-in-window-p coordinates window | |
2167 | This function checks whether a particular frame position falls within | |
2168 | the window @var{window}. | |
2169 | ||
2170 | The argument @var{coordinates} is a cons cell of the form @code{(@var{x} | |
2171 | . @var{y})}. The coordinates @var{x} and @var{y} are measured in | |
2172 | characters, and count from the top left corner of the screen or frame. | |
2173 | ||
2174 | The value returned by @code{coordinates-in-window-p} is non-@code{nil} | |
2175 | if the coordinates are inside @var{window}. The value also indicates | |
2176 | what part of the window the position is in, as follows: | |
2177 | ||
2178 | @table @code | |
2179 | @item (@var{relx} . @var{rely}) | |
2180 | The coordinates are inside @var{window}. The numbers @var{relx} and | |
2181 | @var{rely} are the equivalent window-relative coordinates for the | |
2182 | specified position, counting from 0 at the top left corner of the | |
2183 | window. | |
2184 | ||
2185 | @item mode-line | |
2186 | The coordinates are in the mode line of @var{window}. | |
2187 | ||
2188 | @item header-line | |
2189 | The coordinates are in the header line of @var{window}. | |
2190 | ||
2191 | @item vertical-line | |
2192 | The coordinates are in the vertical line between @var{window} and its | |
2193 | neighbor to the right. This value occurs only if the window doesn't | |
2194 | have a scroll bar; positions in a scroll bar are considered outside the | |
2195 | window for these purposes. | |
2196 | ||
2197 | @item left-fringe | |
2198 | @itemx right-fringe | |
2199 | The coordinates are in the left or right fringe of the window. | |
2200 | ||
2201 | @item left-margin | |
2202 | @itemx right-margin | |
2203 | The coordinates are in the left or right margin of the window. | |
2204 | ||
2205 | @item nil | |
2206 | The coordinates are not in any part of @var{window}. | |
2207 | @end table | |
2208 | ||
2209 | The function @code{coordinates-in-window-p} does not require a frame as | |
2210 | argument because it always uses the frame that @var{window} is on. | |
2211 | @end defun | |
2212 | ||
2213 | @node Window Tree | |
2214 | @section The Window Tree | |
2215 | @cindex window tree | |
2216 | ||
2217 | A @dfn{window tree} specifies the layout, size, and relationship | |
2218 | between all windows in one frame. | |
2219 | ||
2220 | @defun window-tree &optional frame | |
2221 | This function returns the window tree for frame @var{frame}. | |
2222 | If @var{frame} is omitted, the selected frame is used. | |
2223 | ||
2224 | The return value is a list of the form @code{(@var{root} @var{mini})}, | |
2225 | where @var{root} represents the window tree of the frame's | |
2226 | root window, and @var{mini} is the frame's minibuffer window. | |
2227 | ||
2228 | If the root window is not split, @var{root} is the root window itself. | |
2229 | Otherwise, @var{root} is a list @code{(@var{dir} @var{edges} @var{w1} | |
2230 | @var{w2} ...)} where @var{dir} is @code{nil} for a horizontal split, | |
2231 | and @code{t} for a vertical split, @var{edges} gives the combined size and | |
2232 | position of the subwindows in the split, and the rest of the elements | |
2233 | are the subwindows in the split. Each of the subwindows may again be | |
2234 | a window or a list representing a window split, and so on. The | |
2235 | @var{edges} element is a list @code{(@var{left}@var{ top}@var{ right}@var{ bottom})} | |
2236 | similar to the value returned by @code{window-edges}. | |
2237 | @end defun | |
2238 | ||
2239 | @node Window Configurations | |
2240 | @section Window Configurations | |
2241 | @cindex window configurations | |
2242 | @cindex saving window information | |
2243 | ||
2244 | A @dfn{window configuration} records the entire layout of one | |
619fb9ee RS |
2245 | frame---all windows, their sizes, which buffers they contain, how |
2246 | those buffers are scrolled, and their values of point and the mark; | |
2247 | also their fringes, margins, and scroll bar settings. It also | |
b8d4c8d0 | 2248 | includes the values of @code{window-min-height}, |
619fb9ee RS |
2249 | @code{window-min-width} and @code{minibuffer-scroll-window}. As a |
2250 | special exception, the window configuration does not record the value | |
2251 | of point in the selected window for the current buffer. | |
b8d4c8d0 GM |
2252 | |
2253 | You can bring back an entire previous layout by restoring a window | |
2254 | configuration previously saved. If you want to record all frames | |
2255 | instead of just one, use a frame configuration instead of a window | |
2256 | configuration. @xref{Frame Configurations}. | |
2257 | ||
2258 | @defun current-window-configuration &optional frame | |
2259 | This function returns a new object representing @var{frame}'s current | |
2260 | window configuration. If @var{frame} is omitted, the selected frame | |
2261 | is used. | |
2262 | @end defun | |
2263 | ||
2264 | @defun set-window-configuration configuration | |
2265 | This function restores the configuration of windows and buffers as | |
2266 | specified by @var{configuration}, for the frame that @var{configuration} | |
2267 | was created for. | |
2268 | ||
2269 | The argument @var{configuration} must be a value that was previously | |
2270 | returned by @code{current-window-configuration}. This configuration is | |
2271 | restored in the frame from which @var{configuration} was made, whether | |
2272 | that frame is selected or not. This always counts as a window size | |
2273 | change and triggers execution of the @code{window-size-change-functions} | |
2274 | (@pxref{Window Hooks}), because @code{set-window-configuration} doesn't | |
2275 | know how to tell whether the new configuration actually differs from the | |
2276 | old one. | |
2277 | ||
2278 | If the frame which @var{configuration} was saved from is dead, all this | |
2279 | function does is restore the three variables @code{window-min-height}, | |
2280 | @code{window-min-width} and @code{minibuffer-scroll-window}. In this | |
2281 | case, the function returns @code{nil}. Otherwise, it returns @code{t}. | |
2282 | ||
2283 | Here is a way of using this function to get the same effect | |
2284 | as @code{save-window-excursion}: | |
2285 | ||
2286 | @example | |
2287 | @group | |
2288 | (let ((config (current-window-configuration))) | |
2289 | (unwind-protect | |
2290 | (progn (split-window-vertically nil) | |
2291 | @dots{}) | |
2292 | (set-window-configuration config))) | |
2293 | @end group | |
2294 | @end example | |
2295 | @end defun | |
2296 | ||
2297 | @defspec save-window-excursion forms@dots{} | |
2298 | This special form records the window configuration, executes @var{forms} | |
2299 | in sequence, then restores the earlier window configuration. The window | |
2300 | configuration includes, for each window, the value of point and the | |
2301 | portion of the buffer that is visible. It also includes the choice of | |
2302 | selected window. However, it does not include the value of point in | |
2303 | the current buffer; use @code{save-excursion} also, if you wish to | |
2304 | preserve that. | |
2305 | ||
2306 | Don't use this construct when @code{save-selected-window} is sufficient. | |
2307 | ||
2308 | Exit from @code{save-window-excursion} always triggers execution of the | |
2309 | @code{window-size-change-functions}. (It doesn't know how to tell | |
2310 | whether the restored configuration actually differs from the one in | |
2311 | effect at the end of the @var{forms}.) | |
2312 | ||
2313 | The return value is the value of the final form in @var{forms}. | |
2314 | For example: | |
2315 | ||
2316 | @example | |
2317 | @group | |
2318 | (split-window) | |
2319 | @result{} #<window 25 on control.texi> | |
2320 | @end group | |
2321 | @group | |
2322 | (setq w (selected-window)) | |
2323 | @result{} #<window 19 on control.texi> | |
2324 | @end group | |
2325 | @group | |
2326 | (save-window-excursion | |
2327 | (delete-other-windows w) | |
2328 | (switch-to-buffer "foo") | |
2329 | 'do-something) | |
2330 | @result{} do-something | |
2331 | ;; @r{The screen is now split again.} | |
2332 | @end group | |
2333 | @end example | |
2334 | @end defspec | |
2335 | ||
2336 | @defun window-configuration-p object | |
2337 | This function returns @code{t} if @var{object} is a window configuration. | |
2338 | @end defun | |
2339 | ||
2340 | @defun compare-window-configurations config1 config2 | |
2341 | This function compares two window configurations as regards the | |
2342 | structure of windows, but ignores the values of point and mark and the | |
2343 | saved scrolling positions---it can return @code{t} even if those | |
2344 | aspects differ. | |
2345 | ||
2346 | The function @code{equal} can also compare two window configurations; it | |
2347 | regards configurations as unequal if they differ in any respect, even a | |
2348 | saved point or mark. | |
2349 | @end defun | |
2350 | ||
2351 | @defun window-configuration-frame config | |
2352 | This function returns the frame for which the window configuration | |
2353 | @var{config} was made. | |
2354 | @end defun | |
2355 | ||
2356 | Other primitives to look inside of window configurations would make | |
2357 | sense, but are not implemented because we did not need them. See the | |
2358 | file @file{winner.el} for some more operations on windows | |
2359 | configurations. | |
2360 | ||
2361 | @node Window Hooks | |
2362 | @section Hooks for Window Scrolling and Changes | |
2363 | @cindex hooks for window operations | |
2364 | ||
2365 | This section describes how a Lisp program can take action whenever a | |
2366 | window displays a different part of its buffer or a different buffer. | |
2367 | There are three actions that can change this: scrolling the window, | |
2368 | switching buffers in the window, and changing the size of the window. | |
2369 | The first two actions run @code{window-scroll-functions}; the last runs | |
2370 | @code{window-size-change-functions}. | |
2371 | ||
2372 | @defvar window-scroll-functions | |
2373 | This variable holds a list of functions that Emacs should call before | |
2374 | redisplaying a window with scrolling. It is not a normal hook, because | |
2375 | each function is called with two arguments: the window, and its new | |
2376 | display-start position. | |
2377 | ||
2378 | Displaying a different buffer in the window also runs these functions. | |
2379 | ||
2380 | These functions must be careful in using @code{window-end} | |
2381 | (@pxref{Window Start}); if you need an up-to-date value, you must use | |
2382 | the @var{update} argument to ensure you get it. | |
2383 | ||
2384 | @strong{Warning:} don't use this feature to alter the way the window | |
2385 | is scrolled. It's not designed for that, and such use probably won't | |
2386 | work. | |
2387 | @end defvar | |
2388 | ||
2389 | @defvar window-size-change-functions | |
2390 | This variable holds a list of functions to be called if the size of any | |
2391 | window changes for any reason. The functions are called just once per | |
2392 | redisplay, and just once for each frame on which size changes have | |
2393 | occurred. | |
2394 | ||
2395 | Each function receives the frame as its sole argument. There is no | |
2396 | direct way to find out which windows on that frame have changed size, or | |
2397 | precisely how. However, if a size-change function records, at each | |
2398 | call, the existing windows and their sizes, it can also compare the | |
2399 | present sizes and the previous sizes. | |
2400 | ||
2401 | Creating or deleting windows counts as a size change, and therefore | |
2402 | causes these functions to be called. Changing the frame size also | |
2403 | counts, because it changes the sizes of the existing windows. | |
2404 | ||
2405 | It is not a good idea to use @code{save-window-excursion} (@pxref{Window | |
2406 | Configurations}) in these functions, because that always counts as a | |
2407 | size change, and it would cause these functions to be called over and | |
2408 | over. In most cases, @code{save-selected-window} (@pxref{Selecting | |
2409 | Windows}) is what you need here. | |
2410 | @end defvar | |
2411 | ||
2412 | @defvar redisplay-end-trigger-functions | |
2413 | This abnormal hook is run whenever redisplay in a window uses text that | |
2414 | extends past a specified end trigger position. You set the end trigger | |
2415 | position with the function @code{set-window-redisplay-end-trigger}. The | |
2416 | functions are called with two arguments: the window, and the end trigger | |
2417 | position. Storing @code{nil} for the end trigger position turns off the | |
2418 | feature, and the trigger value is automatically reset to @code{nil} just | |
2419 | after the hook is run. | |
2420 | @end defvar | |
2421 | ||
2422 | @defun set-window-redisplay-end-trigger window position | |
2423 | This function sets @var{window}'s end trigger position at | |
2424 | @var{position}. | |
2425 | @end defun | |
2426 | ||
2427 | @defun window-redisplay-end-trigger &optional window | |
2428 | This function returns @var{window}'s current end trigger position. | |
2429 | If @var{window} is @code{nil} or omitted, it uses the selected window. | |
2430 | @end defun | |
2431 | ||
2432 | @defvar window-configuration-change-hook | |
2433 | A normal hook that is run every time you change the window configuration | |
2434 | of an existing frame. This includes splitting or deleting windows, | |
2435 | changing the sizes of windows, or displaying a different buffer in a | |
2436 | window. The frame whose window configuration has changed is the | |
2437 | selected frame when this hook runs. | |
2438 | @end defvar | |
2439 | ||
2440 | @ignore | |
2441 | arch-tag: 3f6c36e8-df49-4986-b757-417feed88be3 | |
2442 | @end ignore |