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802b0ea7 | 1 | @c This is part of the Emacs manual. |
846a13b8 | 2 | @c Copyright (C) 1985, 86, 87, 93, 94, 95, 1997, 2000, 2001, 2002 |
b8f3a9e3 | 3 | @c Free Software Foundation, Inc. |
6bf7aab6 DL |
4 | @c See file emacs.texi for copying conditions. |
5 | @node Display, Search, Registers, Top | |
6 | @chapter Controlling the Display | |
7 | ||
8 | Since only part of a large buffer fits in the window, Emacs tries to | |
9 | show a part that is likely to be interesting. Display-control commands | |
10 | allow you to specify which part of the text you want to see, and how to | |
11 | display it. | |
12 | ||
13 | @menu | |
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14 | * Faces:: How to change the display style using faces. |
15 | * Font Lock:: Minor mode for syntactic highlighting using faces. | |
16 | * Highlight Changes:: Using colors to show where you changed the buffer. | |
17 | * Highlight Interactively:: Tell Emacs what text to highlight. | |
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18 | * Scrolling:: Moving text up and down in a window. |
19 | * Horizontal Scrolling:: Moving text left and right in a window. | |
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20 | * Fringes:: Enabling or disabling window fringes. |
21 | * Useless Whitespace:: Showing possibly-spurious trailing whitespace. | |
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22 | * Follow Mode:: Follow mode lets two windows scroll as one. |
23 | * Selective Display:: Hiding lines with lots of indentation. | |
24 | * Optional Mode Line:: Optional mode line display features. | |
25 | * Text Display:: How text characters are normally displayed. | |
e598186c | 26 | * Display Custom:: Information on variables for customizing display. |
099bfef9 | 27 | * Cursor Display:: Features for displaying the cursor. |
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28 | @end menu |
29 | ||
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30 | @node Faces |
31 | @section Using Multiple Typefaces | |
32 | @cindex faces | |
33 | ||
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34 | Emacs supports using multiple styles of displaying characters. Each |
35 | style is called a @dfn{face}. Each face can specify various @dfn{face | |
36 | attributes}, such as the font family, the height, weight and slant of | |
37 | the characters, the foreground and background color, and underlining | |
38 | or overlining. A face does not have to specify all of these | |
39 | attributes; often it inherits many of them from another face. | |
40 | ||
41 | On a window system, all the Emacs face attributes are meaningful. | |
42 | On a character terminal, only some of them work. Some character | |
43 | terminals support inverse video, bold, and underline attributes; some | |
44 | support colors. Character terminals generally do not support changing | |
45 | the height and width or the font family. | |
c1b45553 | 46 | |
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47 | Features which rely on text in multiple faces (such as Font Lock mode) |
48 | will also work on non-windowed terminals that can display more than one | |
49 | face, whether by colors or underlining and emboldening. This includes | |
50 | the console on GNU/Linux, an @code{xterm} which supports colors, the | |
51 | MS-DOS display (@pxref{MS-DOS}), and the MS-Windows version invoked with | |
52 | the @option{-nw} option. Emacs determines automatically whether the | |
53 | terminal has this capability. | |
b8f3a9e3 | 54 | |
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55 | You control the appearance of a part of the text in the buffer by |
56 | specifying the face or faces to use for it. The style of display used | |
57 | for any given character is determined by combining the attributes of | |
58 | all the applicable faces specified for that character. Any attribute | |
0ec1f115 | 59 | that isn't specified by these faces is taken from the @code{default} face, |
04d0b662 | 60 | whose attributes reflect the default settings of the frame itself. |
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61 | |
62 | Enriched mode, the mode for editing formatted text, includes several | |
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63 | commands and menus for specifying faces for text in the buffer. |
64 | @xref{Format Faces}, for how to specify the font for text in the | |
65 | buffer. @xref{Format Colors}, for how to specify the foreground and | |
66 | background color. | |
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67 | |
68 | @cindex face colors, setting | |
69 | @findex set-face-foreground | |
70 | @findex set-face-background | |
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71 | To alter the appearance of a face, use the customization buffer. |
72 | @xref{Face Customization}. You can also use X resources to specify | |
186e9bcc | 73 | attributes of particular faces (@pxref{Resources}). Alternatively, |
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74 | you can change the foreground and background colors of a specific face |
75 | with @kbd{M-x set-face-foreground} and @kbd{M-x set-face-background}. | |
76 | These commands prompt in the minibuffer for a face name and a color | |
77 | name, with completion, and then set that face to use the specified | |
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78 | color. Changing the colors of the @code{default} face also changes |
79 | the foreground and background colors on all frames, both existing and | |
80 | those to be created in the future. (You can also set foreground and | |
81 | background colors for the current frame only; see @ref{Frame | |
82 | Parameters}.) | |
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83 | |
84 | Emacs 21 can correctly display variable-width fonts, but Emacs | |
85 | commands that calculate width and indentation do not know how to | |
86 | calculate variable widths. This can sometimes lead to incorrect | |
87 | results when you use variable-width fonts. In particular, indentation | |
88 | commands can give inconsistent results, so we recommend you avoid | |
89 | variable-width fonts for editing program source code. Filling will | |
90 | sometimes make lines too long or too short. We plan to address these | |
91 | issues in future Emacs versions. | |
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92 | |
93 | @findex list-faces-display | |
94 | To see what faces are currently defined, and what they look like, type | |
95 | @kbd{M-x list-faces-display}. It's possible for a given face to look | |
96 | different in different frames; this command shows the appearance in the | |
04d0b662 | 97 | frame in which you type it. Here's a list of the standard defined |
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98 | faces: |
99 | ||
100 | @table @code | |
101 | @item default | |
102 | This face is used for ordinary text that doesn't specify any other face. | |
103 | @item mode-line | |
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104 | This face is used for the mode line of the currently selected window. |
105 | By default, it's drawn with shadows for a ``raised'' effect on window | |
106 | systems, and drawn as the inverse of the default face on non-windowed | |
107 | terminals. @xref{Display Custom}. | |
108 | @item mode-line-inactive | |
109 | Like @code{mode-line}, but used for mode lines of the windows other | |
110 | than the selected one (if @code{mode-line-in-non-selected-windows} is | |
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111 | non-@code{nil}). This face inherits from @code{mode-line}, so changes |
112 | in that face affect mode lines in all windows. | |
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113 | @item header-line |
114 | Similar to @code{mode-line} for a window's header line. Most modes | |
115 | don't use the header line, but the Info mode does. | |
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116 | @item minibuffer-prompt |
117 | This face is used for the prompt strings displayed in the minibuffer. | |
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118 | @item highlight |
119 | This face is used for highlighting portions of text, in various modes. | |
120 | For example, mouse-sensitive text is highlighted using this face. | |
121 | @item isearch | |
122 | This face is used for highlighting Isearch matches. | |
123 | @item isearch-lazy-highlight-face | |
124 | This face is used for lazy highlighting of Isearch matches other than | |
125 | the current one. | |
126 | @item region | |
127 | This face is used for displaying a selected region (when Transient Mark | |
128 | mode is enabled---see below). | |
129 | @item secondary-selection | |
130 | This face is used for displaying a secondary X selection (@pxref{Secondary | |
131 | Selection}). | |
132 | @item bold | |
133 | This face uses a bold variant of the default font, if it has one. | |
134 | @item italic | |
135 | This face uses an italic variant of the default font, if it has one. | |
136 | @item bold-italic | |
137 | This face uses a bold italic variant of the default font, if it has one. | |
138 | @item underline | |
139 | This face underlines text. | |
140 | @item fixed-pitch | |
141 | The basic fixed-pitch face. | |
142 | @item fringe | |
143 | @cindex fringe | |
144 | The face for the fringes to the left and right of windows on graphic | |
145 | displays. (The fringes are the narrow portions of the Emacs frame | |
940627fe | 146 | between the text area and the window's right and left borders.) |
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147 | @item scroll-bar |
148 | This face determines the visual appearance of the scroll bar. | |
149 | @item border | |
150 | This face determines the color of the frame border. | |
151 | @item cursor | |
152 | This face determines the color of the cursor. | |
153 | @item mouse | |
154 | This face determines the color of the mouse pointer. | |
155 | @item tool-bar | |
156 | This is the basic tool-bar face. No text appears in the tool bar, but the | |
157 | colors of this face affect the appearance of tool bar icons. | |
158 | @item tooltip | |
159 | This face is used for tooltips. | |
160 | @item menu | |
161 | This face determines the colors and font of Emacs's menus. Setting the | |
162 | font of LessTif/Motif menus is currently not supported; attempts to set | |
163 | the font are ignored in this case. | |
164 | @item trailing-whitespace | |
165 | The face for highlighting trailing whitespace when | |
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166 | @code{show-trailing-whitespace} is non-@code{nil}; see @ref{Useless |
167 | Whitespace}. | |
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168 | @item variable-pitch |
169 | The basic variable-pitch face. | |
170 | @end table | |
171 | ||
172 | @cindex @code{region} face | |
173 | When Transient Mark mode is enabled, the text of the region is | |
174 | highlighted when the mark is active. This uses the face named | |
175 | @code{region}; you can control the style of highlighting by changing the | |
176 | style of this face (@pxref{Face Customization}). @xref{Transient Mark}, | |
177 | for more information about Transient Mark mode and activation and | |
178 | deactivation of the mark. | |
179 | ||
180 | One easy way to use faces is to turn on Font Lock mode. This minor | |
181 | mode, which is always local to a particular buffer, arranges to | |
182 | choose faces according to the syntax of the text you are editing. It | |
183 | can recognize comments and strings in most languages; in several | |
184 | languages, it can also recognize and properly highlight various other | |
185 | important constructs. @xref{Font Lock}, for more information about | |
186 | Font Lock mode and syntactic highlighting. | |
187 | ||
188 | You can print out the buffer with the highlighting that appears | |
189 | on your screen using the command @code{ps-print-buffer-with-faces}. | |
190 | @xref{PostScript}. | |
191 | ||
192 | @node Font Lock | |
193 | @section Font Lock mode | |
194 | @cindex Font Lock mode | |
195 | @cindex mode, Font Lock | |
196 | @cindex syntax highlighting and coloring | |
197 | ||
8cc11660 RS |
198 | Font Lock mode is a minor mode, always local to a particular buffer, |
199 | which highlights (or ``fontifies'') using various faces according to | |
200 | the syntax of the text you are editing. It can recognize comments and | |
201 | strings in most languages; in several languages, it can also recognize | |
202 | and properly highlight various other important constructs---for | |
203 | example, names of functions being defined or reserved keywords. | |
204 | Some special modes, such as Occur mode and Info mode, have completely | |
205 | specialized ways of assigning fonts for Font Lock mode. | |
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206 | |
207 | @findex font-lock-mode | |
208 | @findex turn-on-font-lock | |
209 | The command @kbd{M-x font-lock-mode} turns Font Lock mode on or off | |
210 | according to the argument, and toggles the mode when it has no argument. | |
211 | The function @code{turn-on-font-lock} unconditionally enables Font Lock | |
212 | mode. This is useful in mode-hook functions. For example, to enable | |
213 | Font Lock mode whenever you edit a C file, you can do this: | |
214 | ||
215 | @example | |
216 | (add-hook 'c-mode-hook 'turn-on-font-lock) | |
217 | @end example | |
218 | ||
219 | @findex global-font-lock-mode | |
220 | @vindex global-font-lock-mode | |
221 | To turn on Font Lock mode automatically in all modes which support | |
222 | it, customize the user option @code{global-font-lock-mode} or use the | |
223 | function @code{global-font-lock-mode} in your @file{.emacs} file, like | |
224 | this: | |
225 | ||
226 | @example | |
227 | (global-font-lock-mode 1) | |
228 | @end example | |
229 | ||
230 | Font Lock mode uses several specifically named faces to do its job, | |
231 | including @code{font-lock-string-face}, @code{font-lock-comment-face}, | |
232 | and others. The easiest way to find them all is to use completion | |
233 | on the face name in @code{set-face-foreground}. | |
234 | ||
235 | To change the colors or the fonts used by Font Lock mode to fontify | |
236 | different parts of text, just change these faces. There are | |
237 | two ways to do it: | |
238 | ||
239 | @itemize @bullet | |
240 | @item | |
241 | Invoke @kbd{M-x set-face-foreground} or @kbd{M-x set-face-background} | |
242 | to change the colors of a particular face used by Font Lock. | |
243 | @xref{Faces}. The command @kbd{M-x list-faces-display} displays all | |
244 | the faces currently known to Emacs, including those used by Font Lock. | |
245 | ||
246 | @item | |
247 | Customize the faces interactively with @kbd{M-x customize-face}, as | |
248 | described in @ref{Face Customization}. | |
249 | @end itemize | |
250 | ||
251 | To get the full benefit of Font Lock mode, you need to choose a | |
252 | default font which has bold, italic, and bold-italic variants; or else | |
253 | you need to have a color or gray-scale screen. | |
254 | ||
255 | @vindex font-lock-maximum-decoration | |
256 | The variable @code{font-lock-maximum-decoration} specifies the | |
257 | preferred level of fontification, for modes that provide multiple | |
258 | levels. Level 1 is the least amount of fontification; some modes | |
259 | support levels as high as 3. The normal default is ``as high as | |
260 | possible.'' You can specify an integer, which applies to all modes, or | |
261 | you can specify different numbers for particular major modes; for | |
262 | example, to use level 1 for C/C++ modes, and the default level | |
263 | otherwise, use this: | |
264 | ||
265 | @example | |
266 | (setq font-lock-maximum-decoration | |
267 | '((c-mode . 1) (c++-mode . 1))) | |
268 | @end example | |
269 | ||
270 | @vindex font-lock-maximum-size | |
271 | Fontification can be too slow for large buffers, so you can suppress | |
272 | it. The variable @code{font-lock-maximum-size} specifies a buffer size, | |
273 | beyond which buffer fontification is suppressed. | |
274 | ||
275 | @c @w is used below to prevent a bad page-break. | |
276 | @vindex font-lock-beginning-of-syntax-function | |
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277 | @cindex incorrect fontification |
278 | @cindex parenthesis in column zero and fontification | |
279 | @cindex brace in column zero and fontification | |
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280 | Comment and string fontification (or ``syntactic'' fontification) |
281 | relies on analysis of the syntactic structure of the buffer text. For | |
0ec1f115 | 282 | the sake of speed, some modes, including C mode and Lisp mode, |
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283 | rely on a special convention: an open-parenthesis or open-brace in the |
284 | leftmost column always defines the @w{beginning} of a defun, and is | |
ee6038a6 | 285 | thus always outside any string or comment. (@xref{Left Margin |
9048ad82 | 286 | Paren}.) If you don't follow this convention, Font Lock mode can |
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287 | misfontify the text that follows an open-parenthesis or open-brace in |
288 | the leftmost column that is inside a string or comment. | |
b8f3a9e3 | 289 | |
6bb2ed9b | 290 | @cindex slow display during scrolling |
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291 | The variable @code{font-lock-beginning-of-syntax-function} (always |
292 | buffer-local) specifies how Font Lock mode can find a position | |
293 | guaranteed to be outside any comment or string. In modes which use the | |
294 | leftmost column parenthesis convention, the default value of the variable | |
295 | is @code{beginning-of-defun}---that tells Font Lock mode to use the | |
296 | convention. If you set this variable to @code{nil}, Font Lock no longer | |
297 | relies on the convention. This avoids incorrect results, but the price | |
298 | is that, in some cases, fontification for a changed text must rescan | |
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299 | buffer text from the beginning of the buffer. This can considerably |
300 | slow down redisplay while scrolling, particularly if you are close to | |
301 | the end of a large buffer. | |
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302 | |
303 | @findex font-lock-add-keywords | |
304 | Font Lock highlighting patterns already exist for many modes, but you | |
305 | may want to fontify additional patterns. You can use the function | |
306 | @code{font-lock-add-keywords}, to add your own highlighting patterns for | |
307 | a particular mode. For example, to highlight @samp{FIXME:} words in C | |
308 | comments, use this: | |
309 | ||
310 | @example | |
311 | (font-lock-add-keywords | |
312 | 'c-mode | |
313 | '(("\\<\\(FIXME\\):" 1 font-lock-warning-face t))) | |
314 | @end example | |
315 | ||
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316 | @findex font-lock-remove-keywords |
317 | To remove keywords from the font-lock highlighting patterns, use the | |
cd77ce13 | 318 | function @code{font-lock-remove-keywords}. @xref{Search-based |
a7b94a53 | 319 | Fontification,,,elisp}, for documentation of the format of this list. |
4063fff3 | 320 | |
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321 | @cindex just-in-time (JIT) font-lock |
322 | @cindex background syntax highlighting | |
323 | Fontifying large buffers can take a long time. To avoid large | |
324 | delays when a file is visited, Emacs fontifies only the visible | |
325 | portion of a buffer. As you scroll through the buffer, each portion | |
326 | that becomes visible is fontified as soon as it is displayed. The | |
327 | parts of the buffer that are not displayed are fontified | |
328 | ``stealthily'', in the background, i.e.@: when Emacs is idle. You can | |
329 | control this background fontification, called @dfn{Just-In-Time}, or | |
330 | @dfn{JIT} Font Lock, by customizing various options in the | |
331 | customization group @samp{jit-lock}. @xref{Specific Customization}. | |
332 | ||
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333 | @node Highlight Changes |
334 | @section Highlight Changes Mode | |
335 | ||
336 | @findex highlight-changes-mode | |
337 | Use @kbd{M-x highlight-changes-mode} to enable a minor mode | |
338 | that uses faces (colors, typically) to indicate which parts of | |
339 | the buffer were changed most recently. | |
340 | ||
341 | @node Highlight Interactively | |
342 | @section Interactive Highlighting by Matching | |
343 | @cindex highlighting by matching | |
344 | @cindex interactive highlighting | |
345 | ||
346 | It is sometimes useful to highlight the strings that match a certain | |
347 | regular expression. For example, you might wish to see all the | |
348 | references to a certain variable in a program source file, or highlight | |
349 | certain parts in a voluminous output of some program, or make certain | |
350 | cliches stand out in an article. | |
351 | ||
352 | @findex hi-lock-mode | |
353 | Use the @kbd{M-x hi-lock-mode} command to turn on a minor mode that | |
354 | allows you to specify regular expressions of the text to be | |
355 | highlighted. Hi-lock mode works like Font Lock (@pxref{Font Lock}), | |
356 | except that it lets you specify explicitly what parts of text to | |
357 | highlight. You control Hi-lock mode with these commands: | |
358 | ||
359 | @table @kbd | |
360 | @item C-x w h @var{regexp} @key{RET} @var{face} @key{RET} | |
361 | @kindex C-x w h | |
362 | @findex highlight-regexp | |
363 | Highlight text that matches | |
364 | @var{regexp} using face @var{face} (@code{highlight-regexp}). | |
365 | By using this command more than once, you can highlight various | |
366 | parts of the text in different ways. | |
367 | ||
368 | @item C-x w r @var{regexp} @key{RET} | |
369 | @kindex C-x w r | |
370 | @findex unhighlight-regexp | |
371 | Unhighlight @var{regexp} (@code{unhighlight-regexp}). You must enter | |
372 | one of the regular expressions currently specified for highlighting. | |
04d0b662 | 373 | (You can use completion, or choose from a menu, to enter one of them |
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374 | conveniently.) |
375 | ||
376 | @item C-x w l @var{regexp} @key{RET} @var{face} @key{RET} | |
377 | @kindex C-x w l | |
378 | @findex highlight-lines-matching-regexp | |
379 | @cindex lines, highlighting | |
380 | @cindex highlighting lines of text | |
04d0b662 | 381 | Highlight entire lines containing a match for @var{regexp}, using face |
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382 | @var{face} (@code{highlight-lines-matching-regexp}). |
383 | ||
384 | @item C-x w b | |
385 | @kindex C-x w b | |
386 | @findex hi-lock-write-interactive-patterns | |
387 | Insert all the current highlighting regexp/face pairs into the buffer | |
388 | at point, with comment delimiters to prevent them from changing your | |
389 | program. This key binding runs the | |
390 | @code{hi-lock-write-interactive-patterns} command. | |
391 | ||
392 | These patterns will be read the next time you visit the file while | |
393 | Hi-lock mode is enabled, or whenever you use the @kbd{M-x | |
394 | hi-lock-find-patterns} command. | |
395 | ||
396 | @item C-x w i | |
397 | @kindex C-x w i | |
398 | @findex hi-lock-find-patterns | |
399 | @vindex hi-lock-exclude-modes | |
400 | Re-read regexp/face pairs in the current buffer | |
401 | (@code{hi-lock-write-interactive-patterns}). The list of pairs is | |
402 | found no matter where in the buffer it may be. | |
403 | ||
404 | This command does nothing if the major mode is a member of the list | |
405 | @code{hi-lock-exclude-modes}. | |
406 | @end table | |
407 | ||
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408 | @node Scrolling |
409 | @section Scrolling | |
410 | ||
411 | If a buffer contains text that is too large to fit entirely within a | |
412 | window that is displaying the buffer, Emacs shows a contiguous portion of | |
413 | the text. The portion shown always contains point. | |
414 | ||
415 | @cindex scrolling | |
416 | @dfn{Scrolling} means moving text up or down in the window so that | |
417 | different parts of the text are visible. Scrolling forward means that text | |
418 | moves up, and new text appears at the bottom. Scrolling backward moves | |
419 | text down and new text appears at the top. | |
420 | ||
421 | Scrolling happens automatically if you move point past the bottom or top | |
422 | of the window. You can also explicitly request scrolling with the commands | |
423 | in this section. | |
424 | ||
425 | @table @kbd | |
426 | @item C-l | |
427 | Clear screen and redisplay, scrolling the selected window to center | |
428 | point vertically within it (@code{recenter}). | |
429 | @item C-v | |
430 | Scroll forward (a windowful or a specified number of lines) (@code{scroll-up}). | |
431 | @item @key{NEXT} | |
04d0b662 | 432 | @itemx @key{PAGEDOWN} |
6bf7aab6 DL |
433 | Likewise, scroll forward. |
434 | @item M-v | |
435 | Scroll backward (@code{scroll-down}). | |
436 | @item @key{PRIOR} | |
04d0b662 | 437 | @itemx @key{PAGEUP} |
6bf7aab6 DL |
438 | Likewise, scroll backward. |
439 | @item @var{arg} C-l | |
440 | Scroll so point is on line @var{arg} (@code{recenter}). | |
441 | @item C-M-l | |
442 | Scroll heuristically to bring useful information onto the screen | |
443 | (@code{reposition-window}). | |
444 | @end table | |
445 | ||
446 | @kindex C-l | |
447 | @findex recenter | |
448 | The most basic scrolling command is @kbd{C-l} (@code{recenter}) with | |
449 | no argument. It clears the entire screen and redisplays all windows. | |
450 | In addition, it scrolls the selected window so that point is halfway | |
451 | down from the top of the window. | |
452 | ||
453 | @kindex C-v | |
454 | @kindex M-v | |
455 | @kindex NEXT | |
456 | @kindex PRIOR | |
04d0b662 RS |
457 | @kindex PAGEDOWN |
458 | @kindex PAGEUP | |
6bf7aab6 DL |
459 | @findex scroll-up |
460 | @findex scroll-down | |
6bf7aab6 | 461 | @vindex next-screen-context-lines |
04d0b662 RS |
462 | To read the buffer a windowful at a time, use @kbd{C-v} |
463 | (@code{scroll-up}) with no argument. This scrolls forward by nearly | |
464 | the whole window height. The effect is to take the two lines at the | |
465 | bottom of the window and put them at the top, followed by nearly a | |
466 | whole windowful of lines that were not previously visible. If point | |
467 | was in the text that scrolled off the top, it ends up at the new top | |
468 | of the window. | |
469 | ||
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470 | @kbd{M-v} (@code{scroll-down}) with no argument scrolls backward in |
471 | a similar way, also with overlap. The number of lines of overlap | |
472 | across a @kbd{C-v} or @kbd{M-v} is controlled by the variable | |
04d0b662 RS |
473 | @code{next-screen-context-lines}; by default, it is 2. The function |
474 | keys @key{NEXT} and @key{PRIOR}, or @key{PAGEDOWN} and @key{PAGEUP}, | |
475 | are equivalent to @kbd{C-v} and @kbd{M-v}. | |
476 | ||
477 | The commands @kbd{C-v} and @kbd{M-v} with a numeric argument scroll | |
478 | the text in the selected window up or down a few lines. @kbd{C-v} | |
479 | with an argument moves the text and point up, together, that many | |
480 | lines; it brings the same number of new lines into view at the bottom | |
481 | of the window. @kbd{M-v} with numeric argument scrolls the text | |
482 | downward, bringing that many new lines into view at the top of the | |
483 | window. @kbd{C-v} with a negative argument is like @kbd{M-v} and vice | |
484 | versa. | |
485 | ||
486 | The names of scroll commands are based on the direction that the | |
487 | text moves in the window. Thus, the command to scroll forward is | |
488 | called @code{scroll-up} because it moves the text upward on the | |
489 | screen. The keys @key{PAGEDOWN} and @key{PAGEUP} derive their names | |
490 | and customary meanings from a different convention that developed | |
491 | elsewhere; hence the strange result that @key{PAGEDOWN} runs | |
492 | @code{scroll-up}. | |
6bf7aab6 DL |
493 | |
494 | @vindex scroll-preserve-screen-position | |
495 | Some users like the full-screen scroll commands to keep point at the | |
496 | same screen line. To enable this behavior, set the variable | |
497 | @code{scroll-preserve-screen-position} to a non-@code{nil} value. This | |
498 | mode is convenient for browsing through a file by scrolling by | |
499 | screenfuls; if you come back to the screen where you started, point goes | |
500 | back to the line where it started. However, this mode is inconvenient | |
501 | when you move to the next screen in order to move point to the text | |
502 | there. | |
503 | ||
504 | Another way to do scrolling is with @kbd{C-l} with a numeric argument. | |
505 | @kbd{C-l} does not clear the screen when given an argument; it only scrolls | |
506 | the selected window. With a positive argument @var{n}, it repositions text | |
507 | to put point @var{n} lines down from the top. An argument of zero puts | |
508 | point on the very top line. Point does not move with respect to the text; | |
509 | rather, the text and point move rigidly on the screen. @kbd{C-l} with a | |
510 | negative argument puts point that many lines from the bottom of the window. | |
511 | For example, @kbd{C-u - 1 C-l} puts point on the bottom line, and @kbd{C-u | |
04d0b662 RS |
512 | - 5 C-l} puts it five lines from the bottom. @kbd{C-u C-l} scrolls to put |
513 | point at the center (vertically) of the selected window. | |
6bf7aab6 DL |
514 | |
515 | @kindex C-M-l | |
516 | @findex reposition-window | |
517 | The @kbd{C-M-l} command (@code{reposition-window}) scrolls the current | |
518 | window heuristically in a way designed to get useful information onto | |
519 | the screen. For example, in a Lisp file, this command tries to get the | |
520 | entire current defun onto the screen if possible. | |
521 | ||
522 | @vindex scroll-conservatively | |
04d0b662 RS |
523 | Scrolling happens automatically when point moves out of the visible |
524 | portion of the text. Normally, automatic scrolling centers point | |
525 | vertically within the window. However, if you set | |
526 | @code{scroll-conservatively} to a small number @var{n}, then if you | |
527 | move point just a little off the screen---less than @var{n} | |
528 | lines---then Emacs scrolls the text just far enough to bring point | |
529 | back on screen. By default, @code{scroll-conservatively} is 0. | |
6bf7aab6 | 530 | |
6dd5e8cc EZ |
531 | @cindex aggressive scrolling |
532 | @vindex scroll-up-aggressively | |
177c0ea7 | 533 | @vindex scroll-down-aggressively |
e598186c RS |
534 | When the window does scroll by a longer distance, you can control |
535 | how aggressively it scrolls, by setting the variables | |
536 | @code{scroll-up-aggressively} and @code{scroll-down-aggressively}. | |
537 | The value of @code{scroll-up-aggressively} should be either | |
538 | @code{nil}, or a fraction @var{f} between 0 and 1. A fraction | |
539 | specifies where on the screen to put point when scrolling upward. | |
540 | More precisely, when a window scrolls up because point is above the | |
541 | window start, the new start position is chosen to put point @var{f} | |
542 | part of the window height from the top. The larger @var{f}, the more | |
543 | aggressive the scrolling. | |
544 | ||
545 | @code{nil}, which is the default, scrolls to put point at the center. | |
546 | So it is equivalent to .5. | |
547 | ||
548 | Likewise, @code{scroll-down-aggressively} is used for scrolling | |
549 | down. The value, @var{f}, specifies how far point should be placed | |
550 | from the bottom of the window; thus, as with | |
551 | @code{scroll-up-aggressively}, a larger value is more aggressive. | |
6dd5e8cc | 552 | |
6bf7aab6 DL |
553 | @vindex scroll-margin |
554 | The variable @code{scroll-margin} restricts how close point can come | |
555 | to the top or bottom of a window. Its value is a number of screen | |
556 | lines; if point comes within that many lines of the top or bottom of the | |
557 | window, Emacs recenters the window. By default, @code{scroll-margin} is | |
558 | 0. | |
559 | ||
560 | @node Horizontal Scrolling | |
561 | @section Horizontal Scrolling | |
562 | @cindex horizontal scrolling | |
563 | ||
564 | @dfn{Horizontal scrolling} means shifting all the lines sideways | |
e598186c | 565 | within a window---so that some of the text near the left margin is not |
04d0b662 | 566 | displayed at all. Emacs does this automatically in any window that |
e598186c RS |
567 | uses line truncation rather than continuation: whenever point moves |
568 | off the left or right edge of the screen, Emacs scrolls the buffer | |
569 | horizontally to make point visible. | |
570 | ||
571 | When a window has been scrolled horizontally, text lines are truncated | |
572 | rather than continued (@pxref{Continuation Lines}), with a @samp{$} | |
573 | appearing in the first column when there is text truncated to the left, | |
574 | and in the last column when there is text truncated to the right. | |
575 | ||
576 | You can use these commands to do explicit horizontal scrolling. | |
6bf7aab6 DL |
577 | |
578 | @table @kbd | |
579 | @item C-x < | |
580 | Scroll text in current window to the left (@code{scroll-left}). | |
581 | @item C-x > | |
582 | Scroll to the right (@code{scroll-right}). | |
583 | @end table | |
584 | ||
6bf7aab6 DL |
585 | @kindex C-x < |
586 | @kindex C-x > | |
587 | @findex scroll-left | |
588 | @findex scroll-right | |
589 | The command @kbd{C-x <} (@code{scroll-left}) scrolls the selected | |
590 | window to the left by @var{n} columns with argument @var{n}. This moves | |
591 | part of the beginning of each line off the left edge of the window. | |
592 | With no argument, it scrolls by almost the full width of the window (two | |
593 | columns less, to be precise). | |
594 | ||
595 | @kbd{C-x >} (@code{scroll-right}) scrolls similarly to the right. The | |
596 | window cannot be scrolled any farther to the right once it is displayed | |
597 | normally (with each line starting at the window's left margin); | |
598 | attempting to do so has no effect. This means that you don't have to | |
599 | calculate the argument precisely for @w{@kbd{C-x >}}; any sufficiently large | |
600 | argument will restore the normal display. | |
601 | ||
e598186c RS |
602 | If you scroll a window horizontally by hand, that sets a lower bound |
603 | for automatic horizontal scrolling. Automatic scrolling will continue | |
97357fc9 | 604 | to scroll the window, but never farther to the right than the amount |
e598186c | 605 | you previously set by @code{scroll-left}. |
6bf7aab6 | 606 | |
c86cd4e4 EZ |
607 | @vindex hscroll-margin |
608 | The value of the variable @code{hscroll-margin} controls how close | |
609 | to the window's edges point is allowed to get before the window will | |
610 | be automatically scrolled. It is measured in columns. If the value | |
611 | is 5, then moving point within 5 columns of the edge causes horizontal | |
612 | scrolling away from that edge. | |
613 | ||
614 | @vindex hscroll-step | |
615 | The variable @code{hscroll-step} determines how many columns to | |
616 | scroll the window when point gets too close to the edge. If it's | |
617 | zero, horizontal scrolling centers point horizontally within the | |
618 | window. If it's a positive integer, it specifies the number of | |
9b474b4e RS |
619 | columns to scroll by. If it's a floating-point number, it specifies |
620 | the fraction of the window's width to scroll by. The default is zero. | |
04bee768 | 621 | |
c86cd4e4 | 622 | @vindex auto-hscroll-mode |
e598186c | 623 | To disable automatic horizontal scrolling, set the variable |
c86cd4e4 | 624 | @code{auto-hscroll-mode} to @code{nil}. |
03ff8aab | 625 | |
fad78d58 RS |
626 | @node Fringes |
627 | @section Window Fringes | |
628 | @cindex fringes | |
629 | ||
630 | On a graphical display, each Emacs window normally has narrow | |
631 | @dfn{fringes} on the left and right edges. The fringes display | |
632 | indications about the text in the window. | |
633 | ||
634 | The most common use of the fringes is to indicate a continuation | |
635 | line, when one line of text is split into multiple lines on the | |
636 | screen. The left fringe shows a curving arrow for each screen line | |
637 | except the first, indicating that ``this is not the real beginning.'' | |
638 | The right fringe shows a curving arrow for each screen line except the | |
639 | last, indicating that ``this is not the real end.'' | |
640 | ||
566da2e7 | 641 | The fringes indicate line truncation with short horizontal arrows |
fad78d58 | 642 | meaning ``there's more text on this line which is scrolled |
566da2e7 EZ |
643 | horizontally out of view;'' clicking the mouse on one of the arrows |
644 | scrolls the display horizontally in the direction of the arrow. The | |
645 | fringes also indicate other things such as empty lines, or where a | |
646 | program you are debugging is executing (@pxref{Debuggers}). | |
fad78d58 RS |
647 | |
648 | @findex set-fringe-style | |
649 | @findex fringe-mode | |
650 | You can enable and disable the fringes for all frames using | |
651 | @kbd{M-x fringe-mode}. To enable and disable the fringes | |
652 | for the selected frame, use @kbd{M-x set-fringe-style}. | |
653 | ||
654 | @node Useless Whitespace | |
655 | @section Useless Whitespace | |
656 | ||
657 | @cindex trailing whitespace | |
658 | @cindex whitespace, trailing | |
659 | @vindex show-trailing-whitespace | |
660 | It is easy to leave unnecessary spaces at the end of a line, or | |
661 | empty lines at the end of a file, without realizing it. In most | |
662 | cases, this @dfn{trailing whitespace} has no effect, but there are | |
663 | special circumstances where it matters. | |
664 | ||
665 | You can make trailing whitespace at the end of a line visible on the | |
666 | screen by setting the buffer-local variable | |
667 | @code{show-trailing-whitespace} to @code{t}. Then Emacs displays | |
668 | trailing whitespace in the face @code{trailing-whitespace}. | |
669 | ||
670 | This feature does not apply when point is at the end of the line | |
671 | containing the whitespace. Strictly speaking, that is ``trailing | |
672 | whitespace'' nonetheless, but displaying it specially in that case | |
673 | looks ugly while you are typing in new text. In this special case, | |
674 | the location of point is enough to show you that the spaces are | |
675 | present. | |
676 | ||
677 | @findex delete-trailing-whitespace | |
678 | To delete all trailing whitespace within the current buffer's | |
679 | accessible portion (@pxref{Narrowing}), type @kbd{M-x | |
680 | delete-trailing-whitespace @key{RET}}. (This command does not remove | |
681 | the form-feed characters.) | |
682 | ||
877db12e | 683 | @vindex indicate-unused-lines |
fad78d58 | 684 | @vindex default-indicate-empty-lines |
877db12e RS |
685 | @cindex unused lines |
686 | @cindex fringes, and unused line indication | |
687 | Emacs can indicate unused lines at the end of the window with a | |
688 | small image in the left fringe (@pxref{Fringes}). The image appears | |
689 | for window lines that do not correspond to any buffer text. Blank | |
690 | lines at the end of the buffer then stand out because they do not have | |
691 | this image in the fringe. | |
692 | ||
693 | To enable this feature, set the buffer-local variable | |
694 | @code{indicate-unused-lines} to a non-@code{nil} value. The default | |
695 | value of this variable is controlled by the variable | |
696 | @code{default-indicate-unused-lines}; by setting that variable, you | |
697 | can enable or disable this feature for all new buffers. (This feature | |
698 | currently doesn't work on character terminals.) | |
fad78d58 | 699 | |
6bf7aab6 DL |
700 | @node Follow Mode |
701 | @section Follow Mode | |
702 | @cindex Follow mode | |
703 | @cindex mode, Follow | |
fd3d3075 RS |
704 | @findex follow-mode |
705 | @cindex windows, synchronizing | |
706 | @cindex synchronizing windows | |
6bf7aab6 DL |
707 | |
708 | @dfn{Follow mode} is a minor mode that makes two windows showing the | |
709 | same buffer scroll as one tall ``virtual window.'' To use Follow mode, | |
710 | go to a frame with just one window, split it into two side-by-side | |
711 | windows using @kbd{C-x 3}, and then type @kbd{M-x follow-mode}. From | |
712 | then on, you can edit the buffer in either of the two windows, or scroll | |
713 | either one; the other window follows it. | |
714 | ||
8f399c9b RS |
715 | In Follow mode, if you move point outside the portion visible in one |
716 | window and into the portion visible in the other window, that selects | |
717 | the other window---again, treating the two as if they were parts of | |
718 | one large window. | |
719 | ||
6bf7aab6 DL |
720 | To turn off Follow mode, type @kbd{M-x follow-mode} a second time. |
721 | ||
722 | @node Selective Display | |
723 | @section Selective Display | |
4946337d | 724 | @cindex selective display |
6bf7aab6 DL |
725 | @findex set-selective-display |
726 | @kindex C-x $ | |
727 | ||
728 | Emacs has the ability to hide lines indented more than a certain number | |
729 | of columns (you specify how many columns). You can use this to get an | |
730 | overview of a part of a program. | |
731 | ||
732 | To hide lines, type @kbd{C-x $} (@code{set-selective-display}) with a | |
733 | numeric argument @var{n}. Then lines with at least @var{n} columns of | |
734 | indentation disappear from the screen. The only indication of their | |
735 | presence is that three dots (@samp{@dots{}}) appear at the end of each | |
736 | visible line that is followed by one or more hidden ones. | |
737 | ||
738 | The commands @kbd{C-n} and @kbd{C-p} move across the hidden lines as | |
739 | if they were not there. | |
740 | ||
741 | The hidden lines are still present in the buffer, and most editing | |
742 | commands see them as usual, so you may find point in the middle of the | |
743 | hidden text. When this happens, the cursor appears at the end of the | |
744 | previous line, after the three dots. If point is at the end of the | |
745 | visible line, before the newline that ends it, the cursor appears before | |
746 | the three dots. | |
747 | ||
748 | To make all lines visible again, type @kbd{C-x $} with no argument. | |
749 | ||
750 | @vindex selective-display-ellipses | |
751 | If you set the variable @code{selective-display-ellipses} to | |
752 | @code{nil}, the three dots do not appear at the end of a line that | |
753 | precedes hidden lines. Then there is no visible indication of the | |
754 | hidden lines. This variable becomes local automatically when set. | |
755 | ||
756 | @node Optional Mode Line | |
757 | @section Optional Mode Line Features | |
758 | ||
6b61353c KH |
759 | @cindex buffer size display |
760 | @cindex display of buffer size | |
761 | @findex size-indication-mode | |
762 | The buffer percentage @var{pos} indicates the percentage of the | |
763 | buffer above the top of the window. You can additionally display the | |
764 | size of the buffer by typing @kbd{M-x size-indication-mode} to turn on | |
765 | Size Indication mode. The size will be displayed immediately | |
766 | following the buffer percentage like this: | |
767 | ||
768 | @example | |
769 | @var{POS} of @var{SIZE} | |
770 | @end example | |
771 | ||
772 | @noindent | |
773 | Here @var{SIZE} is the human readable representation of the number of | |
774 | characters in the buffer, which means that @samp{k} for 10^3, @samp{M} | |
775 | for 10^6, @samp{G} for 10^9, etc., are used to abbreviate. | |
776 | ||
777 | @cindex narrowing, and buffer size display | |
778 | If you have narrowed the buffer (@pxref{Narrowing}), the size of the | |
779 | accessible part of the buffer is shown. | |
780 | ||
e598186c RS |
781 | @cindex line number display |
782 | @cindex display of line number | |
6bf7aab6 DL |
783 | @findex line-number-mode |
784 | The current line number of point appears in the mode line when Line | |
785 | Number mode is enabled. Use the command @kbd{M-x line-number-mode} to | |
786 | turn this mode on and off; normally it is on. The line number appears | |
6b61353c | 787 | after the buffer percentage @var{pos}, with the letter @samp{L} to |
6bf7aab6 DL |
788 | indicate what it is. @xref{Minor Modes}, for more information about |
789 | minor modes and about how to use this command. | |
790 | ||
43f971ab EZ |
791 | @cindex narrowing, and line number display |
792 | If you have narrowed the buffer (@pxref{Narrowing}), the displayed | |
793 | line number is relative to the accessible portion of the buffer. | |
794 | ||
6bf7aab6 DL |
795 | @vindex line-number-display-limit |
796 | If the buffer is very large (larger than the value of | |
797 | @code{line-number-display-limit}), then the line number doesn't appear. | |
798 | Emacs doesn't compute the line number when the buffer is large, because | |
43f971ab EZ |
799 | that would be too slow. Set it to @code{nil} to remove the limit. |
800 | ||
801 | @vindex line-number-display-limit-width | |
802 | Line-number computation can also be slow if the lines in the buffer | |
803 | are too long. For this reason, Emacs normally doesn't display line | |
804 | numbers if the average width, in characters, of lines near point is | |
805 | larger than the value of the variable | |
806 | @code{line-number-display-limit-width}. The default value is 200 | |
807 | characters. | |
6bf7aab6 DL |
808 | |
809 | @cindex Column Number mode | |
810 | @cindex mode, Column Number | |
811 | @findex column-number-mode | |
812 | You can also display the current column number by turning on Column | |
813 | Number mode. It displays the current column number preceded by the | |
814 | letter @samp{C}. Type @kbd{M-x column-number-mode} to toggle this mode. | |
815 | ||
816 | @findex display-time | |
817 | @cindex time (on mode line) | |
818 | Emacs can optionally display the time and system load in all mode | |
4f00b8c1 DL |
819 | lines. To enable this feature, type @kbd{M-x display-time} or customize |
820 | the option @code{display-time-mode}. The information added to the mode | |
821 | line usually appears after the buffer name, before the mode names and | |
822 | their parentheses. It looks like this: | |
6bf7aab6 DL |
823 | |
824 | @example | |
825 | @var{hh}:@var{mm}pm @var{l.ll} | |
826 | @end example | |
827 | ||
828 | @noindent | |
829 | @vindex display-time-24hr-format | |
830 | Here @var{hh} and @var{mm} are the hour and minute, followed always by | |
831 | @samp{am} or @samp{pm}. @var{l.ll} is the average number of running | |
832 | processes in the whole system recently. (Some fields may be missing if | |
833 | your operating system cannot support them.) If you prefer time display | |
834 | in 24-hour format, set the variable @code{display-time-24hr-format} | |
835 | to @code{t}. | |
836 | ||
837 | @cindex mail (on mode line) | |
72bd7b7b DL |
838 | @vindex display-time-use-mail-icon |
839 | @vindex display-time-mail-face | |
fad78d58 RS |
840 | @vindex display-time-mail-file |
841 | @vindex display-time-mail-directory | |
6bf7aab6 | 842 | The word @samp{Mail} appears after the load level if there is mail |
72bd7b7b DL |
843 | for you that you have not read yet. On a graphical display you can use |
844 | an icon instead of @samp{Mail} by customizing | |
845 | @code{display-time-use-mail-icon}; this may save some space on the mode | |
846 | line. You can customize @code{display-time-mail-face} to make the mail | |
fad78d58 RS |
847 | indicator prominent. Use @code{display-time-mail-file} to specify |
848 | the mail file to check, or set @code{display-time-mail-directory} | |
849 | to specify the directory to check for incoming mail (any nonempty regular | |
850 | file in the directory is considered as ``newly arrived mail''). | |
6bf7aab6 | 851 | |
47d7776c | 852 | @cindex mode line, 3D appearance |
bd3ead08 EZ |
853 | @cindex attributes of mode line, changing |
854 | @cindex non-integral number of lines in a window | |
04d0b662 RS |
855 | By default, the mode line is drawn on graphics displays with |
856 | 3D-style highlighting, like that of a button when it is not being | |
857 | pressed. If you don't like this effect, you can disable the 3D | |
858 | highlighting of the mode line, by customizing the attributes of the | |
859 | @code{mode-line} face in your @file{.emacs} init file, like this: | |
bd3ead08 EZ |
860 | |
861 | @example | |
04d0b662 | 862 | (set-face-attribute 'mode-line nil :box nil) |
bd3ead08 EZ |
863 | @end example |
864 | ||
865 | @noindent | |
04d0b662 | 866 | Alternatively, you can turn off the box attribute in your |
bd3ead08 EZ |
867 | @file{.Xdefaults} file: |
868 | ||
869 | @example | |
04d0b662 | 870 | Emacs.mode-line.AttributeBox: off |
bd3ead08 EZ |
871 | @end example |
872 | ||
b9e58bf2 | 873 | @cindex non-selected windows, mode line appearance |
ac6875fc | 874 | By default, the mode line of nonselected windows is displayed in a |
1c9f5f23 | 875 | different face, called @code{mode-line-inactive}. Only the selected |
ac6875fc RS |
876 | window is displayed in the @code{mode-line} face. This helps show |
877 | which window is selected. When the minibuffer is selected, since | |
878 | it has no mode line, the window from which you activated the minibuffer | |
879 | has its mode line displayed using @code{mode-line}; as a result, | |
880 | ordinary entry to the minibuffer does not change any mode lines. | |
881 | ||
882 | @vindex mode-line-in-non-selected-windows | |
883 | You can disable use of @code{mode-line-inactive} by setting variable | |
1c9f5f23 KS |
884 | @code{mode-line-in-non-selected-windows} to @code{nil}; then all mode |
885 | lines are displayed in the @code{mode-line} face. | |
b9e58bf2 | 886 | |
6bf7aab6 DL |
887 | @node Text Display |
888 | @section How Text Is Displayed | |
889 | @cindex characters (in text) | |
890 | ||
6b61353c | 891 | @acronym{ASCII} printing characters (octal codes 040 through 0176) in Emacs |
13b9ee95 | 892 | buffers are displayed with their graphics, as are non-ASCII multibyte |
6bf7aab6 DL |
893 | printing characters (octal codes above 0400). |
894 | ||
6b61353c | 895 | Some @acronym{ASCII} control characters are displayed in special ways. The |
6bf7aab6 DL |
896 | newline character (octal code 012) is displayed by starting a new line. |
897 | The tab character (octal code 011) is displayed by moving to the next | |
898 | tab stop column (normally every 8 columns). | |
899 | ||
6b61353c | 900 | Other @acronym{ASCII} control characters are normally displayed as a caret |
6bf7aab6 DL |
901 | (@samp{^}) followed by the non-control version of the character; thus, |
902 | control-A is displayed as @samp{^A}. | |
903 | ||
6b61353c | 904 | Non-@acronym{ASCII} characters 0200 through 0237 (octal) are displayed with |
7c9960d7 DL |
905 | octal escape sequences; thus, character code 0230 (octal) is displayed |
906 | as @samp{\230}. The display of character codes 0240 through 0377 | |
907 | (octal) may be either as escape sequences or as graphics. They do not | |
04d0b662 | 908 | normally occur in multibyte buffers, but if they do, they are displayed |
7c9960d7 DL |
909 | as Latin-1 graphics. In unibyte mode, if you enable European display |
910 | they are displayed using their graphics (assuming your terminal supports | |
911 | them), otherwise as escape sequences. @xref{Single-Byte Character | |
912 | Support}. | |
6bf7aab6 | 913 | |
e598186c RS |
914 | @node Display Custom |
915 | @section Customization of Display | |
6bf7aab6 DL |
916 | |
917 | This section contains information for customization only. Beginning | |
918 | users should skip it. | |
919 | ||
920 | @vindex mode-line-inverse-video | |
dddbaa16 MB |
921 | The variable @code{mode-line-inverse-video} is an obsolete way of |
922 | controlling whether the mode line is displayed in inverse video; the | |
923 | preferred way of doing this is to change the @code{mode-line} face. | |
46ff99c0 MB |
924 | @xref{Mode Line}. However, if @code{mode-line-inverse-video} has a |
925 | value of @code{nil}, then the @code{mode-line} face will be ignored, | |
926 | and mode-lines will be drawn using the default text face. | |
927 | @xref{Faces}. | |
6bf7aab6 DL |
928 | |
929 | @vindex inverse-video | |
930 | If the variable @code{inverse-video} is non-@code{nil}, Emacs attempts | |
931 | to invert all the lines of the display from what they normally are. | |
932 | ||
933 | @vindex visible-bell | |
934 | If the variable @code{visible-bell} is non-@code{nil}, Emacs attempts | |
935 | to make the whole screen blink when it would normally make an audible bell | |
936 | sound. This variable has no effect if your terminal does not have a way | |
937 | to make the screen blink.@refill | |
938 | ||
939 | @vindex no-redraw-on-reenter | |
940 | When you reenter Emacs after suspending, Emacs normally clears the | |
941 | screen and redraws the entire display. On some terminals with more than | |
942 | one page of memory, it is possible to arrange the termcap entry so that | |
943 | the @samp{ti} and @samp{te} strings (output to the terminal when Emacs | |
944 | is entered and exited, respectively) switch between pages of memory so | |
945 | as to use one page for Emacs and another page for other output. Then | |
946 | you might want to set the variable @code{no-redraw-on-reenter} | |
947 | non-@code{nil}; this tells Emacs to assume, when resumed, that the | |
948 | screen page it is using still contains what Emacs last wrote there. | |
949 | ||
950 | @vindex echo-keystrokes | |
951 | The variable @code{echo-keystrokes} controls the echoing of multi-character | |
952 | keys; its value is the number of seconds of pause required to cause echoing | |
953 | to start, or zero meaning don't echo at all. @xref{Echo Area}. | |
954 | ||
955 | @vindex ctl-arrow | |
13b9ee95 | 956 | If the variable @code{ctl-arrow} is @code{nil}, all control characters in |
6bf7aab6 DL |
957 | the buffer are displayed with octal escape sequences, except for newline |
958 | and tab. Altering the value of @code{ctl-arrow} makes it local to the | |
959 | current buffer; until that time, the default value is in effect. The | |
960 | default is initially @code{t}. @xref{Display Tables,, Display Tables, | |
961 | elisp, The Emacs Lisp Reference Manual}. | |
962 | ||
963 | @vindex tab-width | |
964 | Normally, a tab character in the buffer is displayed as whitespace which | |
965 | extends to the next display tab stop position, and display tab stops come | |
966 | at intervals equal to eight spaces. The number of spaces per tab is | |
967 | controlled by the variable @code{tab-width}, which is made local by | |
968 | changing it, just like @code{ctl-arrow}. Note that how the tab character | |
969 | in the buffer is displayed has nothing to do with the definition of | |
970 | @key{TAB} as a command. The variable @code{tab-width} must have an | |
971 | integer value between 1 and 1000, inclusive. | |
972 | ||
973 | @c @vindex truncate-lines @c No index entry here, because we have one | |
974 | @c in the continuation section. | |
975 | If the variable @code{truncate-lines} is non-@code{nil}, then each | |
976 | line of text gets just one screen line for display; if the text line is | |
977 | too long, display shows only the part that fits. If | |
978 | @code{truncate-lines} is @code{nil}, then long text lines display as | |
979 | more than one screen line, enough to show the whole text of the line. | |
980 | @xref{Continuation Lines}. Altering the value of @code{truncate-lines} | |
981 | makes it local to the current buffer; until that time, the default value | |
982 | is in effect. The default is initially @code{nil}. | |
983 | ||
984 | @c @vindex truncate-partial-width-windows @c Idx entry is in Split Windows. | |
985 | If the variable @code{truncate-partial-width-windows} is | |
986 | non-@code{nil}, it forces truncation rather than continuation in any | |
987 | window less than the full width of the screen or frame, regardless of | |
988 | the value of @code{truncate-lines}. For information about side-by-side | |
989 | windows, see @ref{Split Window}. See also @ref{Display,, Display, | |
990 | elisp, The Emacs Lisp Reference Manual}. | |
991 | ||
992 | @vindex baud-rate | |
87c8b5fd RS |
993 | The variable @code{baud-rate} holds the output speed of the |
994 | terminal, as far as Emacs knows. Setting this variable does not | |
995 | change the speed of actual data transmission, but the value is used | |
996 | for calculations. On terminals, it affects padding, and decisions | |
997 | about whether to scroll part of the screen or redraw it instead. | |
c39937ea | 998 | It also affects the behavior of incremental search. |
860dab78 | 999 | |
e598186c RS |
1000 | On window-systems, @code{baud-rate} is only used to determine how |
1001 | frequently to look for pending input during display updating. A | |
1002 | higher value of @code{baud-rate} means that check for pending input | |
1003 | will be done less frequently. | |
6bf7aab6 DL |
1004 | |
1005 | You can customize the way any particular character code is displayed | |
1006 | by means of a display table. @xref{Display Tables,, Display Tables, | |
1007 | elisp, The Emacs Lisp Reference Manual}. | |
e598186c | 1008 | |
62095f01 GM |
1009 | @cindex hourglass pointer display |
1010 | @vindex hourglass-delay | |
099bfef9 RS |
1011 | On a window system, Emacs can optionally display the mouse pointer |
1012 | in a special shape to say that Emacs is busy. To turn this feature on | |
1013 | or off, customize the group @code{cursor}. You can also control the | |
1014 | amount of time Emacs must remain busy before the busy indicator is | |
62095f01 | 1015 | displayed, by setting the variable @code{hourglass-delay}. |
099bfef9 | 1016 | |
a66b12be RS |
1017 | @findex tty-suppress-bold-inverse-default-colors |
1018 | On some text-only terminals, bold face and inverse video together | |
1019 | result in text that is hard to read. Call the function | |
1020 | @code{tty-suppress-bold-inverse-default-colors} with a non-@code{nil} | |
1021 | argument to suppress the effect of bold-face in this case. | |
1022 | ||
099bfef9 RS |
1023 | @node Cursor Display |
1024 | @section Displaying the Cursor | |
1025 | ||
e598186c | 1026 | @findex blink-cursor-mode |
e90ab400 | 1027 | @vindex blink-cursor-alist |
e598186c RS |
1028 | @cindex cursor, locating visually |
1029 | @cindex cursor, blinking | |
e598186c | 1030 | You can customize the cursor's color, and whether it blinks, using |
fad78d58 RS |
1031 | the @code{cursor} Custom group (@pxref{Easy Customization}). On |
1032 | graphical terminals, the command @kbd{M-x blink-cursor-mode} enables | |
1033 | or disables the blinking of the cursor. (On text terminals, the | |
1034 | terminal itself blinks the cursor, and Emacs has no control over it.) | |
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1035 | You can control how the cursor appears when it blinks off by setting |
1036 | the variable @code{blink-cursor-alist}. | |
fad78d58 RS |
1037 | |
1038 | @cindex cursor in non-selected windows | |
1039 | @vindex cursor-in-non-selected-windows | |
1040 | Normally, the cursor appears in non-selected windows in the ``off'' | |
1041 | state, with the same appearance as when the blinking cursor blinks | |
1042 | ``off''. For a box cursor, this is a hollow box; for a bar cursor, | |
1043 | this is a thinner bar. To turn off cursors in non-selected windows, | |
1044 | customize the option @code{cursor-in-non-selected-windows} and assign | |
1045 | it a @code{nil} value. | |
099bfef9 RS |
1046 | |
1047 | @vindex x-stretch-cursor | |
1048 | @cindex wide block cursor | |
fad78d58 RS |
1049 | On graphical terminals, Emacs can optionally draw the block cursor |
1050 | as wide as the character under the cursor---for example, if the cursor | |
1051 | is on a tab character, it would cover the full width occupied by that | |
1052 | tab character. To enable this feature, set the variable | |
1053 | @code{x-stretch-cursor} to a non-@code{nil} value. | |
0f613b80 | 1054 | |
fad78d58 RS |
1055 | @findex hl-line-mode |
1056 | @findex global-hl-line-mode | |
1057 | @cindex highlight current line | |
1058 | If you find it hard to see the cursor, you might like HL Line mode, | |
1059 | a minor mode that highlights the line containing point. Use @kbd{M-x | |
1060 | hl-line-mode} to enable or disable it in the current buffer. @kbd{M-x | |
1061 | global-hl-line-mode} enables or disables the same mode globally. | |
6b61353c KH |
1062 | |
1063 | @ignore | |
1064 | arch-tag: 2219f910-2ff0-4521-b059-1bd231a536c4 | |
1065 | @end ignore |