1 @c This is part of the Emacs manual.
2 @c Copyright (C) 1985, 86, 87, 93, 94, 95, 1997, 2000, 2001
3 @c Free Software Foundation, Inc.
4 @c See file emacs.texi for copying conditions.
5 @node Display, Search, Registers, Top
6 @chapter Controlling the Display
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
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.
18 * Trailing Whitespace:: Showing possibly-spurious trailing whitespace.
19 * Scrolling:: Moving text up and down in a window.
20 * Horizontal Scrolling:: Moving text left and right in a window.
21 * Follow Mode:: Follow mode lets two windows scroll as one.
22 * Selective Display:: Hiding lines with lots of indentation.
23 * Optional Mode Line:: Optional mode line display features.
24 * Text Display:: How text characters are normally displayed.
25 * Display Custom:: Information on variables for customizing display.
26 * Cursor Display:: Features for displaying the cursor.
30 @section Using Multiple Typefaces
33 Emacs supports using multiple styles of displaying characters. Each
34 style is called a @dfn{face}. Each face can specify various @dfn{face
35 attributes}, such as the font family, the height, weight and slant of
36 the characters, the foreground and background color, and underlining
37 or overlining. A face does not have to specify all of these
38 attributes; often it inherits many of them from another face.
40 On a window system, all the Emacs face attributes are meaningful.
41 On a character terminal, only some of them work. Some character
42 terminals support inverse video, bold, and underline attributes; some
43 support colors. Character terminals generally do not support changing
44 the height and width or the font family.
46 Features which rely on text in multiple faces (such as Font Lock mode)
47 will also work on non-windowed terminals that can display more than one
48 face, whether by colors or underlining and emboldening. This includes
49 the console on GNU/Linux, an @code{xterm} which supports colors, the
50 MS-DOS display (@pxref{MS-DOS}), and the MS-Windows version invoked with
51 the @option{-nw} option. Emacs determines automatically whether the
52 terminal has this capability.
54 You control the appearance of a part of the text in the buffer by
55 specifying the face or faces to use for it. The style of display used
56 for any given character is determined by combining the attributes of
57 all the applicable faces specified for that character. Any attribute
58 that isn't specified by these faces is taken from the @code{default} face,
59 whose attributes reflect the default settings of the frame itself.
61 Enriched mode, the mode for editing formatted text, includes several
62 commands and menus for specifying faces for text in the buffer.
63 @xref{Format Faces}, for how to specify the font for text in the
64 buffer. @xref{Format Colors}, for how to specify the foreground and
67 @cindex face colors, setting
68 @findex set-face-foreground
69 @findex set-face-background
70 To alter the appearance of a face, use the customization buffer.
71 @xref{Face Customization}. You can also use X resources to specify
72 attributes of particular faces (@pxref{Resources}). Alternatively,
73 you can change the foreground and background colors of a specific face
74 with @kbd{M-x set-face-foreground} and @kbd{M-x set-face-background}.
75 These commands prompt in the minibuffer for a face name and a color
76 name, with completion, and then set that face to use the specified
77 color. Changing the colors of the @code{default} face also changes
78 the foreground and background colors on all frames, both existing and
79 those to be created in the future. (You can also set foreground and
80 background colors for the current frame only; see @ref{Frame
83 Emacs 21 can correctly display variable-width fonts, but Emacs
84 commands that calculate width and indentation do not know how to
85 calculate variable widths. This can sometimes lead to incorrect
86 results when you use variable-width fonts. In particular, indentation
87 commands can give inconsistent results, so we recommend you avoid
88 variable-width fonts for editing program source code. Filling will
89 sometimes make lines too long or too short. We plan to address these
90 issues in future Emacs versions.
92 @findex list-faces-display
93 To see what faces are currently defined, and what they look like, type
94 @kbd{M-x list-faces-display}. It's possible for a given face to look
95 different in different frames; this command shows the appearance in the
96 frame in which you type it. Here's a list of the standard defined
101 This face is used for ordinary text that doesn't specify any other face.
103 This face is used for the mode line of the currently selected window.
104 By default, it's drawn with shadows for a ``raised'' effect on window
105 systems, and drawn as the inverse of the default face on non-windowed
106 terminals. @xref{Display Custom}.
107 @item mode-line-inactive
108 Like @code{mode-line}, but used for mode lines of the windows other
109 than the selected one (if @code{mode-line-in-non-selected-windows} is
112 Similar to @code{mode-line} for a window's header line. Most modes
113 don't use the header line, but the Info mode does.
114 @item minibuffer-prompt
115 This face is used for the prompt strings displayed in the minibuffer.
117 This face is used for highlighting portions of text, in various modes.
118 For example, mouse-sensitive text is highlighted using this face.
120 This face is used for highlighting Isearch matches.
121 @item isearch-lazy-highlight-face
122 This face is used for lazy highlighting of Isearch matches other than
125 This face is used for displaying a selected region (when Transient Mark
126 mode is enabled---see below).
127 @item secondary-selection
128 This face is used for displaying a secondary X selection (@pxref{Secondary
131 This face uses a bold variant of the default font, if it has one.
133 This face uses an italic variant of the default font, if it has one.
135 This face uses a bold italic variant of the default font, if it has one.
137 This face underlines text.
139 The basic fixed-pitch face.
142 The face for the fringes to the left and right of windows on graphic
143 displays. (The fringes are the narrow portions of the Emacs frame
144 between the text area and the window's right and left borders.)
146 This face determines the visual appearance of the scroll bar.
148 This face determines the color of the frame border.
150 This face determines the color of the cursor.
152 This face determines the color of the mouse pointer.
154 This is the basic tool-bar face. No text appears in the tool bar, but the
155 colors of this face affect the appearance of tool bar icons.
157 This face is used for tooltips.
159 This face determines the colors and font of Emacs's menus. Setting the
160 font of LessTif/Motif menus is currently not supported; attempts to set
161 the font are ignored in this case.
162 @item trailing-whitespace
163 The face for highlighting trailing whitespace when
164 @code{show-trailing-whitespace} is non-nil; see @ref{Trailing Whitespace}.
166 The basic variable-pitch face.
169 @cindex @code{region} face
170 When Transient Mark mode is enabled, the text of the region is
171 highlighted when the mark is active. This uses the face named
172 @code{region}; you can control the style of highlighting by changing the
173 style of this face (@pxref{Face Customization}). @xref{Transient Mark},
174 for more information about Transient Mark mode and activation and
175 deactivation of the mark.
177 One easy way to use faces is to turn on Font Lock mode. This minor
178 mode, which is always local to a particular buffer, arranges to
179 choose faces according to the syntax of the text you are editing. It
180 can recognize comments and strings in most languages; in several
181 languages, it can also recognize and properly highlight various other
182 important constructs. @xref{Font Lock}, for more information about
183 Font Lock mode and syntactic highlighting.
185 You can print out the buffer with the highlighting that appears
186 on your screen using the command @code{ps-print-buffer-with-faces}.
190 @section Font Lock mode
191 @cindex Font Lock mode
192 @cindex mode, Font Lock
193 @cindex syntax highlighting and coloring
195 Font Lock mode is a minor mode, always local to a particular
196 buffer, which highlights (or ``fontifies'') using various faces
197 according to the syntax of the text you are editing. It can
198 recognize comments and strings in most languages; in several
199 languages, it can also recognize and properly highlight various other
200 important constructs---for example, names of functions being defined
201 or reserved keywords.
203 @findex font-lock-mode
204 @findex turn-on-font-lock
205 The command @kbd{M-x font-lock-mode} turns Font Lock mode on or off
206 according to the argument, and toggles the mode when it has no argument.
207 The function @code{turn-on-font-lock} unconditionally enables Font Lock
208 mode. This is useful in mode-hook functions. For example, to enable
209 Font Lock mode whenever you edit a C file, you can do this:
212 (add-hook 'c-mode-hook 'turn-on-font-lock)
215 @findex global-font-lock-mode
216 @vindex global-font-lock-mode
217 To turn on Font Lock mode automatically in all modes which support
218 it, customize the user option @code{global-font-lock-mode} or use the
219 function @code{global-font-lock-mode} in your @file{.emacs} file, like
223 (global-font-lock-mode 1)
226 Font Lock mode uses several specifically named faces to do its job,
227 including @code{font-lock-string-face}, @code{font-lock-comment-face},
228 and others. The easiest way to find them all is to use completion
229 on the face name in @code{set-face-foreground}.
231 To change the colors or the fonts used by Font Lock mode to fontify
232 different parts of text, just change these faces. There are
237 Invoke @kbd{M-x set-face-foreground} or @kbd{M-x set-face-background}
238 to change the colors of a particular face used by Font Lock.
239 @xref{Faces}. The command @kbd{M-x list-faces-display} displays all
240 the faces currently known to Emacs, including those used by Font Lock.
243 Customize the faces interactively with @kbd{M-x customize-face}, as
244 described in @ref{Face Customization}.
247 To get the full benefit of Font Lock mode, you need to choose a
248 default font which has bold, italic, and bold-italic variants; or else
249 you need to have a color or gray-scale screen.
251 @vindex font-lock-maximum-decoration
252 The variable @code{font-lock-maximum-decoration} specifies the
253 preferred level of fontification, for modes that provide multiple
254 levels. Level 1 is the least amount of fontification; some modes
255 support levels as high as 3. The normal default is ``as high as
256 possible.'' You can specify an integer, which applies to all modes, or
257 you can specify different numbers for particular major modes; for
258 example, to use level 1 for C/C++ modes, and the default level
262 (setq font-lock-maximum-decoration
263 '((c-mode . 1) (c++-mode . 1)))
266 @vindex font-lock-maximum-size
267 Fontification can be too slow for large buffers, so you can suppress
268 it. The variable @code{font-lock-maximum-size} specifies a buffer size,
269 beyond which buffer fontification is suppressed.
271 @c @w is used below to prevent a bad page-break.
272 @vindex font-lock-beginning-of-syntax-function
273 @cindex incorrect fontification
274 @cindex parenthesis in column zero and fontification
275 @cindex brace in column zero and fontification
276 Comment and string fontification (or ``syntactic'' fontification)
277 relies on analysis of the syntactic structure of the buffer text. For
278 the sake of speed, some modes, including C mode and Lisp mode,
279 rely on a special convention: an open-parenthesis or open-brace in the
280 leftmost column always defines the @w{beginning} of a defun, and is
281 thus always outside any string or comment. (@xref{Left Margin
282 Paren}.) If you don't follow this convention, Font Lock mode can
283 misfontify the text that follows an open-parenthesis or open-brace in
284 the leftmost column that is inside a string or comment.
286 @cindex slow display during scrolling
287 The variable @code{font-lock-beginning-of-syntax-function} (always
288 buffer-local) specifies how Font Lock mode can find a position
289 guaranteed to be outside any comment or string. In modes which use the
290 leftmost column parenthesis convention, the default value of the variable
291 is @code{beginning-of-defun}---that tells Font Lock mode to use the
292 convention. If you set this variable to @code{nil}, Font Lock no longer
293 relies on the convention. This avoids incorrect results, but the price
294 is that, in some cases, fontification for a changed text must rescan
295 buffer text from the beginning of the buffer. This can considerably
296 slow down redisplay while scrolling, particularly if you are close to
297 the end of a large buffer.
299 @findex font-lock-add-keywords
300 Font Lock highlighting patterns already exist for many modes, but you
301 may want to fontify additional patterns. You can use the function
302 @code{font-lock-add-keywords}, to add your own highlighting patterns for
303 a particular mode. For example, to highlight @samp{FIXME:} words in C
307 (font-lock-add-keywords
309 '(("\\<\\(FIXME\\):" 1 font-lock-warning-face t)))
312 @findex font-lock-remove-keywords
313 To remove keywords from the font-lock highlighting patterns, use the
314 function @code{font-lock-remove-keywords}.
316 @cindex just-in-time (JIT) font-lock
317 @cindex background syntax highlighting
318 Fontifying large buffers can take a long time. To avoid large
319 delays when a file is visited, Emacs fontifies only the visible
320 portion of a buffer. As you scroll through the buffer, each portion
321 that becomes visible is fontified as soon as it is displayed. The
322 parts of the buffer that are not displayed are fontified
323 ``stealthily'', in the background, i.e.@: when Emacs is idle. You can
324 control this background fontification, called @dfn{Just-In-Time}, or
325 @dfn{JIT} Font Lock, by customizing various options in the
326 customization group @samp{jit-lock}. @xref{Specific Customization}.
328 @node Highlight Changes
329 @section Highlight Changes Mode
331 @findex highlight-changes-mode
332 Use @kbd{M-x highlight-changes-mode} to enable a minor mode
333 that uses faces (colors, typically) to indicate which parts of
334 the buffer were changed most recently.
336 @node Highlight Interactively
337 @section Interactive Highlighting by Matching
338 @cindex highlighting by matching
339 @cindex interactive highlighting
341 It is sometimes useful to highlight the strings that match a certain
342 regular expression. For example, you might wish to see all the
343 references to a certain variable in a program source file, or highlight
344 certain parts in a voluminous output of some program, or make certain
345 cliches stand out in an article.
348 Use the @kbd{M-x hi-lock-mode} command to turn on a minor mode that
349 allows you to specify regular expressions of the text to be
350 highlighted. Hi-lock mode works like Font Lock (@pxref{Font Lock}),
351 except that it lets you specify explicitly what parts of text to
352 highlight. You control Hi-lock mode with these commands:
355 @item C-x w h @var{regexp} @key{RET} @var{face} @key{RET}
357 @findex highlight-regexp
358 Highlight text that matches
359 @var{regexp} using face @var{face} (@code{highlight-regexp}).
360 By using this command more than once, you can highlight various
361 parts of the text in different ways.
363 @item C-x w r @var{regexp} @key{RET}
365 @findex unhighlight-regexp
366 Unhighlight @var{regexp} (@code{unhighlight-regexp}). You must enter
367 one of the regular expressions currently specified for highlighting.
368 (You can use completion, or choose from a menu, to enter one of them
371 @item C-x w l @var{regexp} @key{RET} @var{face} @key{RET}
373 @findex highlight-lines-matching-regexp
374 @cindex lines, highlighting
375 @cindex highlighting lines of text
376 Highlight entire lines containing a match for @var{regexp}, using face
377 @var{face} (@code{highlight-lines-matching-regexp}).
381 @findex hi-lock-write-interactive-patterns
382 Insert all the current highlighting regexp/face pairs into the buffer
383 at point, with comment delimiters to prevent them from changing your
384 program. This key binding runs the
385 @code{hi-lock-write-interactive-patterns} command.
387 These patterns will be read the next time you visit the file while
388 Hi-lock mode is enabled, or whenever you use the @kbd{M-x
389 hi-lock-find-patterns} command.
393 @findex hi-lock-find-patterns
394 @vindex hi-lock-exclude-modes
395 Re-read regexp/face pairs in the current buffer
396 (@code{hi-lock-write-interactive-patterns}). The list of pairs is
397 found no matter where in the buffer it may be.
399 This command does nothing if the major mode is a member of the list
400 @code{hi-lock-exclude-modes}.
403 @node Trailing Whitespace
404 @section Trailing Whitespace
406 @cindex trailing whitespace
407 @cindex whitespace, trailing
408 @vindex show-trailing-whitespace
409 It is easy to leave unnecessary spaces at the end of a line without
410 realizing it. In most cases, this @dfn{trailing whitespace} has no
411 effect, but there are special circumstances where it matters.
413 You can make trailing whitespace visible on the screen by setting the
414 buffer-local variable @code{show-trailing-whitespace} to @code{t}. Then
415 Emacs displays trailing whitespace in the face
416 @code{trailing-whitespace}.
418 Trailing whitespace is defined as spaces or tabs at the end of a
419 line. But trailing whitespace is not displayed specially if point is
420 at the end of the line containing the whitespace. (Doing that looks
421 ugly while you are typing in new text, and the location of point is
422 enough in that case to show you that the spaces are present.)
424 @findex delete-trailing-whitespace
425 To delete all trailing whitespace within the current buffer's
426 restriction (@pxref{Narrowing}), type @kbd{M-x
427 delete-trailing-whitespace @key{RET}}. (This command does not remove
428 the form-feed characters.)
430 @vindex indicate-empty-lines
431 @vindex default-indicate-empty-lines
433 @cindex fringes, and empty line indication
434 Emacs can indicate empty lines at the end of the buffer with a
435 special bitmap on the left fringe of the window. To enable this
436 feature, set the buffer-local variable @code{indicate-empty-lines} to
437 a non-@code{nil} value. The default value of this variable is
438 controlled by the variable @code{default-indicate-empty-lines};
439 by setting that variable, you can enable or disable this feature
440 for all new buffers. (This feature currently doesn't work on
441 character terminals.)
446 If a buffer contains text that is too large to fit entirely within a
447 window that is displaying the buffer, Emacs shows a contiguous portion of
448 the text. The portion shown always contains point.
451 @dfn{Scrolling} means moving text up or down in the window so that
452 different parts of the text are visible. Scrolling forward means that text
453 moves up, and new text appears at the bottom. Scrolling backward moves
454 text down and new text appears at the top.
456 Scrolling happens automatically if you move point past the bottom or top
457 of the window. You can also explicitly request scrolling with the commands
462 Clear screen and redisplay, scrolling the selected window to center
463 point vertically within it (@code{recenter}).
465 Scroll forward (a windowful or a specified number of lines) (@code{scroll-up}).
467 @itemx @key{PAGEDOWN}
468 Likewise, scroll forward.
470 Scroll backward (@code{scroll-down}).
473 Likewise, scroll backward.
475 Scroll so point is on line @var{arg} (@code{recenter}).
477 Scroll heuristically to bring useful information onto the screen
478 (@code{reposition-window}).
483 The most basic scrolling command is @kbd{C-l} (@code{recenter}) with
484 no argument. It clears the entire screen and redisplays all windows.
485 In addition, it scrolls the selected window so that point is halfway
486 down from the top of the window.
496 @vindex next-screen-context-lines
497 To read the buffer a windowful at a time, use @kbd{C-v}
498 (@code{scroll-up}) with no argument. This scrolls forward by nearly
499 the whole window height. The effect is to take the two lines at the
500 bottom of the window and put them at the top, followed by nearly a
501 whole windowful of lines that were not previously visible. If point
502 was in the text that scrolled off the top, it ends up at the new top
505 @kbd{M-v} (@code{scroll-down}) with no argument scrolls backward in
506 a similar way, also with overlap. The number of lines of overlap
507 across a @kbd{C-v} or @kbd{M-v} is controlled by the variable
508 @code{next-screen-context-lines}; by default, it is 2. The function
509 keys @key{NEXT} and @key{PRIOR}, or @key{PAGEDOWN} and @key{PAGEUP},
510 are equivalent to @kbd{C-v} and @kbd{M-v}.
512 The commands @kbd{C-v} and @kbd{M-v} with a numeric argument scroll
513 the text in the selected window up or down a few lines. @kbd{C-v}
514 with an argument moves the text and point up, together, that many
515 lines; it brings the same number of new lines into view at the bottom
516 of the window. @kbd{M-v} with numeric argument scrolls the text
517 downward, bringing that many new lines into view at the top of the
518 window. @kbd{C-v} with a negative argument is like @kbd{M-v} and vice
521 The names of scroll commands are based on the direction that the
522 text moves in the window. Thus, the command to scroll forward is
523 called @code{scroll-up} because it moves the text upward on the
524 screen. The keys @key{PAGEDOWN} and @key{PAGEUP} derive their names
525 and customary meanings from a different convention that developed
526 elsewhere; hence the strange result that @key{PAGEDOWN} runs
529 @vindex scroll-preserve-screen-position
530 Some users like the full-screen scroll commands to keep point at the
531 same screen line. To enable this behavior, set the variable
532 @code{scroll-preserve-screen-position} to a non-@code{nil} value. This
533 mode is convenient for browsing through a file by scrolling by
534 screenfuls; if you come back to the screen where you started, point goes
535 back to the line where it started. However, this mode is inconvenient
536 when you move to the next screen in order to move point to the text
539 Another way to do scrolling is with @kbd{C-l} with a numeric argument.
540 @kbd{C-l} does not clear the screen when given an argument; it only scrolls
541 the selected window. With a positive argument @var{n}, it repositions text
542 to put point @var{n} lines down from the top. An argument of zero puts
543 point on the very top line. Point does not move with respect to the text;
544 rather, the text and point move rigidly on the screen. @kbd{C-l} with a
545 negative argument puts point that many lines from the bottom of the window.
546 For example, @kbd{C-u - 1 C-l} puts point on the bottom line, and @kbd{C-u
547 - 5 C-l} puts it five lines from the bottom. @kbd{C-u C-l} scrolls to put
548 point at the center (vertically) of the selected window.
551 @findex reposition-window
552 The @kbd{C-M-l} command (@code{reposition-window}) scrolls the current
553 window heuristically in a way designed to get useful information onto
554 the screen. For example, in a Lisp file, this command tries to get the
555 entire current defun onto the screen if possible.
557 @vindex scroll-conservatively
558 Scrolling happens automatically when point moves out of the visible
559 portion of the text. Normally, automatic scrolling centers point
560 vertically within the window. However, if you set
561 @code{scroll-conservatively} to a small number @var{n}, then if you
562 move point just a little off the screen---less than @var{n}
563 lines---then Emacs scrolls the text just far enough to bring point
564 back on screen. By default, @code{scroll-conservatively} is 0.
566 @cindex aggressive scrolling
567 @vindex scroll-up-aggressively
568 @vindex scroll-down-aggressively
569 When the window does scroll by a longer distance, you can control
570 how aggressively it scrolls, by setting the variables
571 @code{scroll-up-aggressively} and @code{scroll-down-aggressively}.
572 The value of @code{scroll-up-aggressively} should be either
573 @code{nil}, or a fraction @var{f} between 0 and 1. A fraction
574 specifies where on the screen to put point when scrolling upward.
575 More precisely, when a window scrolls up because point is above the
576 window start, the new start position is chosen to put point @var{f}
577 part of the window height from the top. The larger @var{f}, the more
578 aggressive the scrolling.
580 @code{nil}, which is the default, scrolls to put point at the center.
581 So it is equivalent to .5.
583 Likewise, @code{scroll-down-aggressively} is used for scrolling
584 down. The value, @var{f}, specifies how far point should be placed
585 from the bottom of the window; thus, as with
586 @code{scroll-up-aggressively}, a larger value is more aggressive.
588 @vindex scroll-margin
589 The variable @code{scroll-margin} restricts how close point can come
590 to the top or bottom of a window. Its value is a number of screen
591 lines; if point comes within that many lines of the top or bottom of the
592 window, Emacs recenters the window. By default, @code{scroll-margin} is
595 @node Horizontal Scrolling
596 @section Horizontal Scrolling
597 @cindex horizontal scrolling
599 @dfn{Horizontal scrolling} means shifting all the lines sideways
600 within a window---so that some of the text near the left margin is not
601 displayed at all. Emacs does this automatically in any window that
602 uses line truncation rather than continuation: whenever point moves
603 off the left or right edge of the screen, Emacs scrolls the buffer
604 horizontally to make point visible.
606 When a window has been scrolled horizontally, text lines are truncated
607 rather than continued (@pxref{Continuation Lines}), with a @samp{$}
608 appearing in the first column when there is text truncated to the left,
609 and in the last column when there is text truncated to the right.
611 You can use these commands to do explicit horizontal scrolling.
615 Scroll text in current window to the left (@code{scroll-left}).
617 Scroll to the right (@code{scroll-right}).
624 The command @kbd{C-x <} (@code{scroll-left}) scrolls the selected
625 window to the left by @var{n} columns with argument @var{n}. This moves
626 part of the beginning of each line off the left edge of the window.
627 With no argument, it scrolls by almost the full width of the window (two
628 columns less, to be precise).
630 @kbd{C-x >} (@code{scroll-right}) scrolls similarly to the right. The
631 window cannot be scrolled any farther to the right once it is displayed
632 normally (with each line starting at the window's left margin);
633 attempting to do so has no effect. This means that you don't have to
634 calculate the argument precisely for @w{@kbd{C-x >}}; any sufficiently large
635 argument will restore the normal display.
637 If you scroll a window horizontally by hand, that sets a lower bound
638 for automatic horizontal scrolling. Automatic scrolling will continue
639 to scroll the window, but never farther to the right than the amount
640 you previously set by @code{scroll-left}.
642 @vindex automatic-hscrolling
643 To disable automatic horizontal scrolling, set the variable
644 @code{automatic-hscrolling} to @code{nil}.
651 @cindex windows, synchronizing
652 @cindex synchronizing windows
654 @dfn{Follow mode} is a minor mode that makes two windows showing the
655 same buffer scroll as one tall ``virtual window.'' To use Follow mode,
656 go to a frame with just one window, split it into two side-by-side
657 windows using @kbd{C-x 3}, and then type @kbd{M-x follow-mode}. From
658 then on, you can edit the buffer in either of the two windows, or scroll
659 either one; the other window follows it.
661 In Follow mode, if you move point outside the portion visible in one
662 window and into the portion visible in the other window, that selects
663 the other window---again, treating the two as if they were parts of
666 To turn off Follow mode, type @kbd{M-x follow-mode} a second time.
668 @node Selective Display
669 @section Selective Display
670 @cindex selective display
671 @findex set-selective-display
674 Emacs has the ability to hide lines indented more than a certain number
675 of columns (you specify how many columns). You can use this to get an
676 overview of a part of a program.
678 To hide lines, type @kbd{C-x $} (@code{set-selective-display}) with a
679 numeric argument @var{n}. Then lines with at least @var{n} columns of
680 indentation disappear from the screen. The only indication of their
681 presence is that three dots (@samp{@dots{}}) appear at the end of each
682 visible line that is followed by one or more hidden ones.
684 The commands @kbd{C-n} and @kbd{C-p} move across the hidden lines as
685 if they were not there.
687 The hidden lines are still present in the buffer, and most editing
688 commands see them as usual, so you may find point in the middle of the
689 hidden text. When this happens, the cursor appears at the end of the
690 previous line, after the three dots. If point is at the end of the
691 visible line, before the newline that ends it, the cursor appears before
694 To make all lines visible again, type @kbd{C-x $} with no argument.
696 @vindex selective-display-ellipses
697 If you set the variable @code{selective-display-ellipses} to
698 @code{nil}, the three dots do not appear at the end of a line that
699 precedes hidden lines. Then there is no visible indication of the
700 hidden lines. This variable becomes local automatically when set.
702 @node Optional Mode Line
703 @section Optional Mode Line Features
705 @cindex line number display
706 @cindex display of line number
707 @findex line-number-mode
708 The current line number of point appears in the mode line when Line
709 Number mode is enabled. Use the command @kbd{M-x line-number-mode} to
710 turn this mode on and off; normally it is on. The line number appears
711 before the buffer percentage @var{pos}, with the letter @samp{L} to
712 indicate what it is. @xref{Minor Modes}, for more information about
713 minor modes and about how to use this command.
715 @cindex narrowing, and line number display
716 If you have narrowed the buffer (@pxref{Narrowing}), the displayed
717 line number is relative to the accessible portion of the buffer.
719 @vindex line-number-display-limit
720 If the buffer is very large (larger than the value of
721 @code{line-number-display-limit}), then the line number doesn't appear.
722 Emacs doesn't compute the line number when the buffer is large, because
723 that would be too slow. Set it to @code{nil} to remove the limit.
725 @vindex line-number-display-limit-width
726 Line-number computation can also be slow if the lines in the buffer
727 are too long. For this reason, Emacs normally doesn't display line
728 numbers if the average width, in characters, of lines near point is
729 larger than the value of the variable
730 @code{line-number-display-limit-width}. The default value is 200
733 @cindex Column Number mode
734 @cindex mode, Column Number
735 @findex column-number-mode
736 You can also display the current column number by turning on Column
737 Number mode. It displays the current column number preceded by the
738 letter @samp{C}. Type @kbd{M-x column-number-mode} to toggle this mode.
741 @cindex time (on mode line)
742 Emacs can optionally display the time and system load in all mode
743 lines. To enable this feature, type @kbd{M-x display-time} or customize
744 the option @code{display-time-mode}. The information added to the mode
745 line usually appears after the buffer name, before the mode names and
746 their parentheses. It looks like this:
749 @var{hh}:@var{mm}pm @var{l.ll}
753 @vindex display-time-24hr-format
754 Here @var{hh} and @var{mm} are the hour and minute, followed always by
755 @samp{am} or @samp{pm}. @var{l.ll} is the average number of running
756 processes in the whole system recently. (Some fields may be missing if
757 your operating system cannot support them.) If you prefer time display
758 in 24-hour format, set the variable @code{display-time-24hr-format}
761 @cindex mail (on mode line)
762 @vindex display-time-use-mail-icon
763 @vindex display-time-mail-face
764 The word @samp{Mail} appears after the load level if there is mail
765 for you that you have not read yet. On a graphical display you can use
766 an icon instead of @samp{Mail} by customizing
767 @code{display-time-use-mail-icon}; this may save some space on the mode
768 line. You can customize @code{display-time-mail-face} to make the mail
771 @cindex mode line, 3D appearance
772 @cindex attributes of mode line, changing
773 @cindex non-integral number of lines in a window
774 By default, the mode line is drawn on graphics displays with
775 3D-style highlighting, like that of a button when it is not being
776 pressed. If you don't like this effect, you can disable the 3D
777 highlighting of the mode line, by customizing the attributes of the
778 @code{mode-line} face in your @file{.emacs} init file, like this:
781 (set-face-attribute 'mode-line nil :box nil)
785 Alternatively, you can turn off the box attribute in your
786 @file{.Xdefaults} file:
789 Emacs.mode-line.AttributeBox: off
792 @cindex non-selected windows, mode line appearance
793 @vindex mode-line-in-non-selected-windows
794 By default, the mode line of non-selected windows is displayed in a
795 different face, called @code{mode-line-inactive}. Only the selected
796 window is displayed in the @code{mode-line} face. When you type at
797 the minibuffer prompt, the window in @code{minibuffer-scroll-window}
798 is considered to be the selected window. You can disable this
799 behavior by setting the value of the variable
800 @code{mode-line-in-non-selected-windows} to @code{nil}; then all mode
801 lines are displayed in the @code{mode-line} face.
804 @section How Text Is Displayed
805 @cindex characters (in text)
807 ASCII printing characters (octal codes 040 through 0176) in Emacs
808 buffers are displayed with their graphics, as are non-ASCII multibyte
809 printing characters (octal codes above 0400).
811 Some ASCII control characters are displayed in special ways. The
812 newline character (octal code 012) is displayed by starting a new line.
813 The tab character (octal code 011) is displayed by moving to the next
814 tab stop column (normally every 8 columns).
816 Other ASCII control characters are normally displayed as a caret
817 (@samp{^}) followed by the non-control version of the character; thus,
818 control-A is displayed as @samp{^A}.
820 Non-ASCII characters 0200 through 0237 (octal) are displayed with
821 octal escape sequences; thus, character code 0230 (octal) is displayed
822 as @samp{\230}. The display of character codes 0240 through 0377
823 (octal) may be either as escape sequences or as graphics. They do not
824 normally occur in multibyte buffers, but if they do, they are displayed
825 as Latin-1 graphics. In unibyte mode, if you enable European display
826 they are displayed using their graphics (assuming your terminal supports
827 them), otherwise as escape sequences. @xref{Single-Byte Character
831 @section Customization of Display
833 This section contains information for customization only. Beginning
834 users should skip it.
836 @vindex mode-line-inverse-video
837 The variable @code{mode-line-inverse-video} is an obsolete way of
838 controlling whether the mode line is displayed in inverse video; the
839 preferred way of doing this is to change the @code{mode-line} face.
840 @xref{Mode Line}. However, if @code{mode-line-inverse-video} has a
841 value of @code{nil}, then the @code{mode-line} face will be ignored,
842 and mode-lines will be drawn using the default text face.
845 @vindex inverse-video
846 If the variable @code{inverse-video} is non-@code{nil}, Emacs attempts
847 to invert all the lines of the display from what they normally are.
850 If the variable @code{visible-bell} is non-@code{nil}, Emacs attempts
851 to make the whole screen blink when it would normally make an audible bell
852 sound. This variable has no effect if your terminal does not have a way
853 to make the screen blink.@refill
855 @vindex no-redraw-on-reenter
856 When you reenter Emacs after suspending, Emacs normally clears the
857 screen and redraws the entire display. On some terminals with more than
858 one page of memory, it is possible to arrange the termcap entry so that
859 the @samp{ti} and @samp{te} strings (output to the terminal when Emacs
860 is entered and exited, respectively) switch between pages of memory so
861 as to use one page for Emacs and another page for other output. Then
862 you might want to set the variable @code{no-redraw-on-reenter}
863 non-@code{nil}; this tells Emacs to assume, when resumed, that the
864 screen page it is using still contains what Emacs last wrote there.
866 @vindex echo-keystrokes
867 The variable @code{echo-keystrokes} controls the echoing of multi-character
868 keys; its value is the number of seconds of pause required to cause echoing
869 to start, or zero meaning don't echo at all. @xref{Echo Area}.
872 If the variable @code{ctl-arrow} is @code{nil}, all control characters in
873 the buffer are displayed with octal escape sequences, except for newline
874 and tab. Altering the value of @code{ctl-arrow} makes it local to the
875 current buffer; until that time, the default value is in effect. The
876 default is initially @code{t}. @xref{Display Tables,, Display Tables,
877 elisp, The Emacs Lisp Reference Manual}.
880 Normally, a tab character in the buffer is displayed as whitespace which
881 extends to the next display tab stop position, and display tab stops come
882 at intervals equal to eight spaces. The number of spaces per tab is
883 controlled by the variable @code{tab-width}, which is made local by
884 changing it, just like @code{ctl-arrow}. Note that how the tab character
885 in the buffer is displayed has nothing to do with the definition of
886 @key{TAB} as a command. The variable @code{tab-width} must have an
887 integer value between 1 and 1000, inclusive.
889 @c @vindex truncate-lines @c No index entry here, because we have one
890 @c in the continuation section.
891 If the variable @code{truncate-lines} is non-@code{nil}, then each
892 line of text gets just one screen line for display; if the text line is
893 too long, display shows only the part that fits. If
894 @code{truncate-lines} is @code{nil}, then long text lines display as
895 more than one screen line, enough to show the whole text of the line.
896 @xref{Continuation Lines}. Altering the value of @code{truncate-lines}
897 makes it local to the current buffer; until that time, the default value
898 is in effect. The default is initially @code{nil}.
900 @c @vindex truncate-partial-width-windows @c Idx entry is in Split Windows.
901 If the variable @code{truncate-partial-width-windows} is
902 non-@code{nil}, it forces truncation rather than continuation in any
903 window less than the full width of the screen or frame, regardless of
904 the value of @code{truncate-lines}. For information about side-by-side
905 windows, see @ref{Split Window}. See also @ref{Display,, Display,
906 elisp, The Emacs Lisp Reference Manual}.
909 The variable @code{baud-rate} holds the output speed of the
910 terminal, as far as Emacs knows. Setting this variable does not
911 change the speed of actual data transmission, but the value is used
912 for calculations. On terminals, it affects padding, and decisions
913 about whether to scroll part of the screen or redraw it instead.
914 It also affects the behavior of incremental search.
916 On window-systems, @code{baud-rate} is only used to determine how
917 frequently to look for pending input during display updating. A
918 higher value of @code{baud-rate} means that check for pending input
919 will be done less frequently.
921 You can customize the way any particular character code is displayed
922 by means of a display table. @xref{Display Tables,, Display Tables,
923 elisp, The Emacs Lisp Reference Manual}.
925 @cindex hourglass pointer display
926 @vindex hourglass-delay
927 On a window system, Emacs can optionally display the mouse pointer
928 in a special shape to say that Emacs is busy. To turn this feature on
929 or off, customize the group @code{cursor}. You can also control the
930 amount of time Emacs must remain busy before the busy indicator is
931 displayed, by setting the variable @code{hourglass-delay}.
933 @findex tty-suppress-bold-inverse-default-colors
934 On some text-only terminals, bold face and inverse video together
935 result in text that is hard to read. Call the function
936 @code{tty-suppress-bold-inverse-default-colors} with a non-@code{nil}
937 argument to suppress the effect of bold-face in this case.
940 @section Displaying the Cursor
943 @findex global-hl-line-mode
944 @cindex highlight current line
945 @findex blink-cursor-mode
946 @cindex cursor, locating visually
947 @cindex cursor, blinking
948 There are a number of ways to customize the display of the cursor.
949 @kbd{M-x hl-line-mode} enables or disables a minor mode which
950 highlights the line containing point. @kbd{M-x global-hl-line-mode}
951 enables the minor mode globally. On window systems, the command
952 @kbd{M-x blink-cursor-mode} turns on or off the blinking of the
953 cursor. (On terminals, the terminal itself blinks the cursor, and
954 Emacs has no control over it.)
956 You can customize the cursor's color, and whether it blinks, using
957 the @code{cursor} Custom group (@pxref{Easy Customization}).
959 @vindex x-stretch-cursor
960 @cindex wide block cursor
961 When displaying on a window system, Emacs can optionally draw the
962 block cursor as wide as the character under the cursor---for example,
963 if the cursor is on a tab character, it would cover the full width
964 occupied by that tab character. To enable this feature, set the
965 variable @code{x-stretch-cursor} to a non-@code{nil} value.
967 @cindex cursor in non-selected windows
968 @vindex cursor-in-non-selected-windows
969 Normally, the cursor in non-selected windows is shown as a hollow box.
970 To turn off cursor display in non-selected windows, customize the option
971 @code{cursor-in-non-selected-windows} to assign it a @code{nil} value.