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 mode lines. By default, it's drawn with shadows
104 for a ``raised'' effect on window systems, and drawn as the inverse of
105 the default face on non-windowed terminals. @xref{Display Custom}.
107 Similar to @code{mode-line} for a window's header line. Most modes
108 don't use the header line, but the Info mode does.
110 This face is used for highlighting portions of text, in various modes.
111 For example, mouse-sensitive text is highlighted using this face.
113 This face is used for highlighting Isearch matches.
114 @item isearch-lazy-highlight-face
115 This face is used for lazy highlighting of Isearch matches other than
118 This face is used for displaying a selected region (when Transient Mark
119 mode is enabled---see below).
120 @item secondary-selection
121 This face is used for displaying a secondary X selection (@pxref{Secondary
124 This face uses a bold variant of the default font, if it has one.
126 This face uses an italic variant of the default font, if it has one.
128 This face uses a bold italic variant of the default font, if it has one.
130 This face underlines text.
132 The basic fixed-pitch face.
135 The face for the fringes to the left and right of windows on graphic
136 displays. (The fringes are the narrow portions of the Emacs frame
137 between the text area and the window's right and left borders.)
139 This face determines the visual appearance of the scroll bar.
141 This face determines the color of the frame border.
143 This face determines the color of the cursor.
145 This face determines the color of the mouse pointer.
147 This is the basic tool-bar face. No text appears in the tool bar, but the
148 colors of this face affect the appearance of tool bar icons.
150 This face is used for tooltips.
152 This face determines the colors and font of Emacs's menus. Setting the
153 font of LessTif/Motif menus is currently not supported; attempts to set
154 the font are ignored in this case.
155 @item trailing-whitespace
156 The face for highlighting trailing whitespace when
157 @code{show-trailing-whitespace} is non-nil; see @ref{Trailing Whitespace}.
159 The basic variable-pitch face.
162 @cindex @code{region} face
163 When Transient Mark mode is enabled, the text of the region is
164 highlighted when the mark is active. This uses the face named
165 @code{region}; you can control the style of highlighting by changing the
166 style of this face (@pxref{Face Customization}). @xref{Transient Mark},
167 for more information about Transient Mark mode and activation and
168 deactivation of the mark.
170 One easy way to use faces is to turn on Font Lock mode. This minor
171 mode, which is always local to a particular buffer, arranges to
172 choose faces according to the syntax of the text you are editing. It
173 can recognize comments and strings in most languages; in several
174 languages, it can also recognize and properly highlight various other
175 important constructs. @xref{Font Lock}, for more information about
176 Font Lock mode and syntactic highlighting.
178 You can print out the buffer with the highlighting that appears
179 on your screen using the command @code{ps-print-buffer-with-faces}.
183 @section Font Lock mode
184 @cindex Font Lock mode
185 @cindex mode, Font Lock
186 @cindex syntax highlighting and coloring
188 Font Lock mode is a minor mode, always local to a particular
189 buffer, which highlights (or ``fontifies'') using various faces
190 according to the syntax of the text you are editing. It can
191 recognize comments and strings in most languages; in several
192 languages, it can also recognize and properly highlight various other
193 important constructs---for example, names of functions being defined
194 or reserved keywords.
196 @findex font-lock-mode
197 @findex turn-on-font-lock
198 The command @kbd{M-x font-lock-mode} turns Font Lock mode on or off
199 according to the argument, and toggles the mode when it has no argument.
200 The function @code{turn-on-font-lock} unconditionally enables Font Lock
201 mode. This is useful in mode-hook functions. For example, to enable
202 Font Lock mode whenever you edit a C file, you can do this:
205 (add-hook 'c-mode-hook 'turn-on-font-lock)
208 @findex global-font-lock-mode
209 @vindex global-font-lock-mode
210 To turn on Font Lock mode automatically in all modes which support
211 it, customize the user option @code{global-font-lock-mode} or use the
212 function @code{global-font-lock-mode} in your @file{.emacs} file, like
216 (global-font-lock-mode 1)
219 Font Lock mode uses several specifically named faces to do its job,
220 including @code{font-lock-string-face}, @code{font-lock-comment-face},
221 and others. The easiest way to find them all is to use completion
222 on the face name in @code{set-face-foreground}.
224 To change the colors or the fonts used by Font Lock mode to fontify
225 different parts of text, just change these faces. There are
230 Invoke @kbd{M-x set-face-foreground} or @kbd{M-x set-face-background}
231 to change the colors of a particular face used by Font Lock.
232 @xref{Faces}. The command @kbd{M-x list-faces-display} displays all
233 the faces currently known to Emacs, including those used by Font Lock.
236 Customize the faces interactively with @kbd{M-x customize-face}, as
237 described in @ref{Face Customization}.
240 To get the full benefit of Font Lock mode, you need to choose a
241 default font which has bold, italic, and bold-italic variants; or else
242 you need to have a color or gray-scale screen.
244 @vindex font-lock-maximum-decoration
245 The variable @code{font-lock-maximum-decoration} specifies the
246 preferred level of fontification, for modes that provide multiple
247 levels. Level 1 is the least amount of fontification; some modes
248 support levels as high as 3. The normal default is ``as high as
249 possible.'' You can specify an integer, which applies to all modes, or
250 you can specify different numbers for particular major modes; for
251 example, to use level 1 for C/C++ modes, and the default level
255 (setq font-lock-maximum-decoration
256 '((c-mode . 1) (c++-mode . 1)))
259 @vindex font-lock-maximum-size
260 Fontification can be too slow for large buffers, so you can suppress
261 it. The variable @code{font-lock-maximum-size} specifies a buffer size,
262 beyond which buffer fontification is suppressed.
264 @c @w is used below to prevent a bad page-break.
265 @vindex font-lock-beginning-of-syntax-function
266 @cindex incorrect fontification
267 @cindex parenthesis in column zero and fontification
268 @cindex brace in column zero and fontification
269 Comment and string fontification (or ``syntactic'' fontification)
270 relies on analysis of the syntactic structure of the buffer text. For
271 the sake of speed, some modes, including C mode and Lisp mode,
272 rely on a special convention: an open-parenthesis or open-brace in the
273 leftmost column always defines the @w{beginning} of a defun, and is
274 thus always outside any string or comment. (@xref{Left Margin
275 Paren}.) If you don't follow this convention, Font Lock mode can
276 misfontify the text that follows an open-parenthesis or open-brace in
277 the leftmost column that is inside a string or comment.
279 @cindex slow display during scrolling
280 The variable @code{font-lock-beginning-of-syntax-function} (always
281 buffer-local) specifies how Font Lock mode can find a position
282 guaranteed to be outside any comment or string. In modes which use the
283 leftmost column parenthesis convention, the default value of the variable
284 is @code{beginning-of-defun}---that tells Font Lock mode to use the
285 convention. If you set this variable to @code{nil}, Font Lock no longer
286 relies on the convention. This avoids incorrect results, but the price
287 is that, in some cases, fontification for a changed text must rescan
288 buffer text from the beginning of the buffer. This can considerably
289 slow down redisplay while scrolling, particularly if you are close to
290 the end of a large buffer.
292 @findex font-lock-add-keywords
293 Font Lock highlighting patterns already exist for many modes, but you
294 may want to fontify additional patterns. You can use the function
295 @code{font-lock-add-keywords}, to add your own highlighting patterns for
296 a particular mode. For example, to highlight @samp{FIXME:} words in C
300 (font-lock-add-keywords
302 '(("\\<\\(FIXME\\):" 1 font-lock-warning-face t)))
305 @findex font-lock-remove-keywords
306 To remove keywords from the font-lock highlighting patterns, use the
307 function @code{font-lock-remove-keywords}.
309 @cindex just-in-time (JIT) font-lock
310 @cindex background syntax highlighting
311 Fontifying large buffers can take a long time. To avoid large
312 delays when a file is visited, Emacs fontifies only the visible
313 portion of a buffer. As you scroll through the buffer, each portion
314 that becomes visible is fontified as soon as it is displayed. The
315 parts of the buffer that are not displayed are fontified
316 ``stealthily'', in the background, i.e.@: when Emacs is idle. You can
317 control this background fontification, called @dfn{Just-In-Time}, or
318 @dfn{JIT} Font Lock, by customizing various options in the
319 customization group @samp{jit-lock}. @xref{Specific Customization}.
321 @node Highlight Changes
322 @section Highlight Changes Mode
324 @findex highlight-changes-mode
325 Use @kbd{M-x highlight-changes-mode} to enable a minor mode
326 that uses faces (colors, typically) to indicate which parts of
327 the buffer were changed most recently.
329 @node Highlight Interactively
330 @section Interactive Highlighting by Matching
331 @cindex highlighting by matching
332 @cindex interactive highlighting
334 It is sometimes useful to highlight the strings that match a certain
335 regular expression. For example, you might wish to see all the
336 references to a certain variable in a program source file, or highlight
337 certain parts in a voluminous output of some program, or make certain
338 cliches stand out in an article.
341 Use the @kbd{M-x hi-lock-mode} command to turn on a minor mode that
342 allows you to specify regular expressions of the text to be
343 highlighted. Hi-lock mode works like Font Lock (@pxref{Font Lock}),
344 except that it lets you specify explicitly what parts of text to
345 highlight. You control Hi-lock mode with these commands:
348 @item C-x w h @var{regexp} @key{RET} @var{face} @key{RET}
350 @findex highlight-regexp
351 Highlight text that matches
352 @var{regexp} using face @var{face} (@code{highlight-regexp}).
353 By using this command more than once, you can highlight various
354 parts of the text in different ways.
356 @item C-x w r @var{regexp} @key{RET}
358 @findex unhighlight-regexp
359 Unhighlight @var{regexp} (@code{unhighlight-regexp}). You must enter
360 one of the regular expressions currently specified for highlighting.
361 (You can use completion, or choose from a menu, to enter one of them
364 @item C-x w l @var{regexp} @key{RET} @var{face} @key{RET}
366 @findex highlight-lines-matching-regexp
367 @cindex lines, highlighting
368 @cindex highlighting lines of text
369 Highlight entire lines containing a match for @var{regexp}, using face
370 @var{face} (@code{highlight-lines-matching-regexp}).
374 @findex hi-lock-write-interactive-patterns
375 Insert all the current highlighting regexp/face pairs into the buffer
376 at point, with comment delimiters to prevent them from changing your
377 program. This key binding runs the
378 @code{hi-lock-write-interactive-patterns} command.
380 These patterns will be read the next time you visit the file while
381 Hi-lock mode is enabled, or whenever you use the @kbd{M-x
382 hi-lock-find-patterns} command.
386 @findex hi-lock-find-patterns
387 @vindex hi-lock-exclude-modes
388 Re-read regexp/face pairs in the current buffer
389 (@code{hi-lock-write-interactive-patterns}). The list of pairs is
390 found no matter where in the buffer it may be.
392 This command does nothing if the major mode is a member of the list
393 @code{hi-lock-exclude-modes}.
396 @node Trailing Whitespace
397 @section Trailing Whitespace
399 @cindex trailing whitespace
400 @cindex whitespace, trailing
401 @vindex show-trailing-whitespace
402 It is easy to leave unnecessary spaces at the end of a line without
403 realizing it. In most cases, this @dfn{trailing whitespace} has no
404 effect, but there are special circumstances where it matters.
406 You can make trailing whitespace visible on the screen by setting the
407 buffer-local variable @code{show-trailing-whitespace} to @code{t}. Then
408 Emacs displays trailing whitespace in the face
409 @code{trailing-whitespace}.
411 Trailing whitespace is defined as spaces or tabs at the end of a
412 line. But trailing whitespace is not displayed specially if point is
413 at the end of the line containing the whitespace. (Doing that looks
414 ugly while you are typing in new text, and the location of point is
415 enough in that case to show you that the spaces are present.)
417 @findex delete-trailing-whitespace
418 To delete all trailing whitespace within the current buffer's
419 restriction (@pxref{Narrowing}), type @kbd{M-x
420 delete-trailing-whitespace @key{RET}}. (This command does not remove
421 the form-feed characters.)
423 @vindex indicate-empty-lines
424 @vindex default-indicate-empty-lines
426 @cindex fringes, and empty line indication
427 Emacs can indicate empty lines at the end of the buffer with a
428 special bitmap on the left fringe of the window. To enable this
429 feature, set the buffer-local variable @code{indicate-empty-lines} to
430 a non-@code{nil} value. The default value of this variable is
431 controlled by the variable @code{default-indicate-empty-lines};
432 by setting that variable, you can enable or disable this feature
433 for all new buffers. (This feature currently doesn't work on
434 character terminals.)
439 If a buffer contains text that is too large to fit entirely within a
440 window that is displaying the buffer, Emacs shows a contiguous portion of
441 the text. The portion shown always contains point.
444 @dfn{Scrolling} means moving text up or down in the window so that
445 different parts of the text are visible. Scrolling forward means that text
446 moves up, and new text appears at the bottom. Scrolling backward moves
447 text down and new text appears at the top.
449 Scrolling happens automatically if you move point past the bottom or top
450 of the window. You can also explicitly request scrolling with the commands
455 Clear screen and redisplay, scrolling the selected window to center
456 point vertically within it (@code{recenter}).
458 Scroll forward (a windowful or a specified number of lines) (@code{scroll-up}).
460 @itemx @key{PAGEDOWN}
461 Likewise, scroll forward.
463 Scroll backward (@code{scroll-down}).
466 Likewise, scroll backward.
468 Scroll so point is on line @var{arg} (@code{recenter}).
470 Scroll heuristically to bring useful information onto the screen
471 (@code{reposition-window}).
476 The most basic scrolling command is @kbd{C-l} (@code{recenter}) with
477 no argument. It clears the entire screen and redisplays all windows.
478 In addition, it scrolls the selected window so that point is halfway
479 down from the top of the window.
489 @vindex next-screen-context-lines
490 To read the buffer a windowful at a time, use @kbd{C-v}
491 (@code{scroll-up}) with no argument. This scrolls forward by nearly
492 the whole window height. The effect is to take the two lines at the
493 bottom of the window and put them at the top, followed by nearly a
494 whole windowful of lines that were not previously visible. If point
495 was in the text that scrolled off the top, it ends up at the new top
498 @kbd{M-v} (@code{scroll-down}) with no argument scrolls backward in
499 a similar way, also with overlap. The number of lines of overlap
500 across a @kbd{C-v} or @kbd{M-v} is controlled by the variable
501 @code{next-screen-context-lines}; by default, it is 2. The function
502 keys @key{NEXT} and @key{PRIOR}, or @key{PAGEDOWN} and @key{PAGEUP},
503 are equivalent to @kbd{C-v} and @kbd{M-v}.
505 The commands @kbd{C-v} and @kbd{M-v} with a numeric argument scroll
506 the text in the selected window up or down a few lines. @kbd{C-v}
507 with an argument moves the text and point up, together, that many
508 lines; it brings the same number of new lines into view at the bottom
509 of the window. @kbd{M-v} with numeric argument scrolls the text
510 downward, bringing that many new lines into view at the top of the
511 window. @kbd{C-v} with a negative argument is like @kbd{M-v} and vice
514 The names of scroll commands are based on the direction that the
515 text moves in the window. Thus, the command to scroll forward is
516 called @code{scroll-up} because it moves the text upward on the
517 screen. The keys @key{PAGEDOWN} and @key{PAGEUP} derive their names
518 and customary meanings from a different convention that developed
519 elsewhere; hence the strange result that @key{PAGEDOWN} runs
522 @vindex scroll-preserve-screen-position
523 Some users like the full-screen scroll commands to keep point at the
524 same screen line. To enable this behavior, set the variable
525 @code{scroll-preserve-screen-position} to a non-@code{nil} value. This
526 mode is convenient for browsing through a file by scrolling by
527 screenfuls; if you come back to the screen where you started, point goes
528 back to the line where it started. However, this mode is inconvenient
529 when you move to the next screen in order to move point to the text
532 Another way to do scrolling is with @kbd{C-l} with a numeric argument.
533 @kbd{C-l} does not clear the screen when given an argument; it only scrolls
534 the selected window. With a positive argument @var{n}, it repositions text
535 to put point @var{n} lines down from the top. An argument of zero puts
536 point on the very top line. Point does not move with respect to the text;
537 rather, the text and point move rigidly on the screen. @kbd{C-l} with a
538 negative argument puts point that many lines from the bottom of the window.
539 For example, @kbd{C-u - 1 C-l} puts point on the bottom line, and @kbd{C-u
540 - 5 C-l} puts it five lines from the bottom. @kbd{C-u C-l} scrolls to put
541 point at the center (vertically) of the selected window.
544 @findex reposition-window
545 The @kbd{C-M-l} command (@code{reposition-window}) scrolls the current
546 window heuristically in a way designed to get useful information onto
547 the screen. For example, in a Lisp file, this command tries to get the
548 entire current defun onto the screen if possible.
550 @vindex scroll-conservatively
551 Scrolling happens automatically when point moves out of the visible
552 portion of the text. Normally, automatic scrolling centers point
553 vertically within the window. However, if you set
554 @code{scroll-conservatively} to a small number @var{n}, then if you
555 move point just a little off the screen---less than @var{n}
556 lines---then Emacs scrolls the text just far enough to bring point
557 back on screen. By default, @code{scroll-conservatively} is 0.
559 @cindex aggressive scrolling
560 @vindex scroll-up-aggressively
561 @vindex scroll-down-aggressively
562 When the window does scroll by a longer distance, you can control
563 how aggressively it scrolls, by setting the variables
564 @code{scroll-up-aggressively} and @code{scroll-down-aggressively}.
565 The value of @code{scroll-up-aggressively} should be either
566 @code{nil}, or a fraction @var{f} between 0 and 1. A fraction
567 specifies where on the screen to put point when scrolling upward.
568 More precisely, when a window scrolls up because point is above the
569 window start, the new start position is chosen to put point @var{f}
570 part of the window height from the top. The larger @var{f}, the more
571 aggressive the scrolling.
573 @code{nil}, which is the default, scrolls to put point at the center.
574 So it is equivalent to .5.
576 Likewise, @code{scroll-down-aggressively} is used for scrolling
577 down. The value, @var{f}, specifies how far point should be placed
578 from the bottom of the window; thus, as with
579 @code{scroll-up-aggressively}, a larger value is more aggressive.
581 @vindex scroll-margin
582 The variable @code{scroll-margin} restricts how close point can come
583 to the top or bottom of a window. Its value is a number of screen
584 lines; if point comes within that many lines of the top or bottom of the
585 window, Emacs recenters the window. By default, @code{scroll-margin} is
588 @node Horizontal Scrolling
589 @section Horizontal Scrolling
590 @cindex horizontal scrolling
592 @dfn{Horizontal scrolling} means shifting all the lines sideways
593 within a window---so that some of the text near the left margin is not
594 displayed at all. Emacs does this automatically in any window that
595 uses line truncation rather than continuation: whenever point moves
596 off the left or right edge of the screen, Emacs scrolls the buffer
597 horizontally to make point visible.
599 When a window has been scrolled horizontally, text lines are truncated
600 rather than continued (@pxref{Continuation Lines}), with a @samp{$}
601 appearing in the first column when there is text truncated to the left,
602 and in the last column when there is text truncated to the right.
604 You can use these commands to do explicit horizontal scrolling.
608 Scroll text in current window to the left (@code{scroll-left}).
610 Scroll to the right (@code{scroll-right}).
617 The command @kbd{C-x <} (@code{scroll-left}) scrolls the selected
618 window to the left by @var{n} columns with argument @var{n}. This moves
619 part of the beginning of each line off the left edge of the window.
620 With no argument, it scrolls by almost the full width of the window (two
621 columns less, to be precise).
623 @kbd{C-x >} (@code{scroll-right}) scrolls similarly to the right. The
624 window cannot be scrolled any farther to the right once it is displayed
625 normally (with each line starting at the window's left margin);
626 attempting to do so has no effect. This means that you don't have to
627 calculate the argument precisely for @w{@kbd{C-x >}}; any sufficiently large
628 argument will restore the normal display.
630 If you scroll a window horizontally by hand, that sets a lower bound
631 for automatic horizontal scrolling. Automatic scrolling will continue
632 to scroll the window, but never farther to the right than the amount
633 you previously set by @code{scroll-left}.
635 @vindex automatic-hscrolling
636 To disable automatic horizontal scrolling, set the variable
637 @code{automatic-hscrolling} to @code{nil}.
644 @cindex windows, synchronizing
645 @cindex synchronizing windows
647 @dfn{Follow mode} is a minor mode that makes two windows showing the
648 same buffer scroll as one tall ``virtual window.'' To use Follow mode,
649 go to a frame with just one window, split it into two side-by-side
650 windows using @kbd{C-x 3}, and then type @kbd{M-x follow-mode}. From
651 then on, you can edit the buffer in either of the two windows, or scroll
652 either one; the other window follows it.
654 In Follow mode, if you move point outside the portion visible in one
655 window and into the portion visible in the other window, that selects
656 the other window---again, treating the two as if they were parts of
659 To turn off Follow mode, type @kbd{M-x follow-mode} a second time.
661 @node Selective Display
662 @section Selective Display
663 @cindex selective display
664 @findex set-selective-display
667 Emacs has the ability to hide lines indented more than a certain number
668 of columns (you specify how many columns). You can use this to get an
669 overview of a part of a program.
671 To hide lines, type @kbd{C-x $} (@code{set-selective-display}) with a
672 numeric argument @var{n}. Then lines with at least @var{n} columns of
673 indentation disappear from the screen. The only indication of their
674 presence is that three dots (@samp{@dots{}}) appear at the end of each
675 visible line that is followed by one or more hidden ones.
677 The commands @kbd{C-n} and @kbd{C-p} move across the hidden lines as
678 if they were not there.
680 The hidden lines are still present in the buffer, and most editing
681 commands see them as usual, so you may find point in the middle of the
682 hidden text. When this happens, the cursor appears at the end of the
683 previous line, after the three dots. If point is at the end of the
684 visible line, before the newline that ends it, the cursor appears before
687 To make all lines visible again, type @kbd{C-x $} with no argument.
689 @vindex selective-display-ellipses
690 If you set the variable @code{selective-display-ellipses} to
691 @code{nil}, the three dots do not appear at the end of a line that
692 precedes hidden lines. Then there is no visible indication of the
693 hidden lines. This variable becomes local automatically when set.
695 @node Optional Mode Line
696 @section Optional Mode Line Features
698 @cindex line number display
699 @cindex display of line number
700 @findex line-number-mode
701 The current line number of point appears in the mode line when Line
702 Number mode is enabled. Use the command @kbd{M-x line-number-mode} to
703 turn this mode on and off; normally it is on. The line number appears
704 before the buffer percentage @var{pos}, with the letter @samp{L} to
705 indicate what it is. @xref{Minor Modes}, for more information about
706 minor modes and about how to use this command.
708 @cindex narrowing, and line number display
709 If you have narrowed the buffer (@pxref{Narrowing}), the displayed
710 line number is relative to the accessible portion of the buffer.
712 @vindex line-number-display-limit
713 If the buffer is very large (larger than the value of
714 @code{line-number-display-limit}), then the line number doesn't appear.
715 Emacs doesn't compute the line number when the buffer is large, because
716 that would be too slow. Set it to @code{nil} to remove the limit.
718 @vindex line-number-display-limit-width
719 Line-number computation can also be slow if the lines in the buffer
720 are too long. For this reason, Emacs normally doesn't display line
721 numbers if the average width, in characters, of lines near point is
722 larger than the value of the variable
723 @code{line-number-display-limit-width}. The default value is 200
726 @cindex Column Number mode
727 @cindex mode, Column Number
728 @findex column-number-mode
729 You can also display the current column number by turning on Column
730 Number mode. It displays the current column number preceded by the
731 letter @samp{C}. Type @kbd{M-x column-number-mode} to toggle this mode.
734 @cindex time (on mode line)
735 Emacs can optionally display the time and system load in all mode
736 lines. To enable this feature, type @kbd{M-x display-time} or customize
737 the option @code{display-time-mode}. The information added to the mode
738 line usually appears after the buffer name, before the mode names and
739 their parentheses. It looks like this:
742 @var{hh}:@var{mm}pm @var{l.ll}
746 @vindex display-time-24hr-format
747 Here @var{hh} and @var{mm} are the hour and minute, followed always by
748 @samp{am} or @samp{pm}. @var{l.ll} is the average number of running
749 processes in the whole system recently. (Some fields may be missing if
750 your operating system cannot support them.) If you prefer time display
751 in 24-hour format, set the variable @code{display-time-24hr-format}
754 @cindex mail (on mode line)
755 @vindex display-time-use-mail-icon
756 @vindex display-time-mail-face
757 The word @samp{Mail} appears after the load level if there is mail
758 for you that you have not read yet. On a graphical display you can use
759 an icon instead of @samp{Mail} by customizing
760 @code{display-time-use-mail-icon}; this may save some space on the mode
761 line. You can customize @code{display-time-mail-face} to make the mail
764 @cindex mode line, 3D appearance
765 @cindex attributes of mode line, changing
766 @cindex non-integral number of lines in a window
767 By default, the mode line is drawn on graphics displays with
768 3D-style highlighting, like that of a button when it is not being
769 pressed. If you don't like this effect, you can disable the 3D
770 highlighting of the mode line, by customizing the attributes of the
771 @code{mode-line} face in your @file{.emacs} init file, like this:
774 (set-face-attribute 'mode-line nil :box nil)
778 Alternatively, you can turn off the box attribute in your
779 @file{.Xdefaults} file:
782 Emacs.mode-line.AttributeBox: off
786 @section How Text Is Displayed
787 @cindex characters (in text)
789 ASCII printing characters (octal codes 040 through 0176) in Emacs
790 buffers are displayed with their graphics, as are non-ASCII multibyte
791 printing characters (octal codes above 0400).
793 Some ASCII control characters are displayed in special ways. The
794 newline character (octal code 012) is displayed by starting a new line.
795 The tab character (octal code 011) is displayed by moving to the next
796 tab stop column (normally every 8 columns).
798 Other ASCII control characters are normally displayed as a caret
799 (@samp{^}) followed by the non-control version of the character; thus,
800 control-A is displayed as @samp{^A}.
802 Non-ASCII characters 0200 through 0237 (octal) are displayed with
803 octal escape sequences; thus, character code 0230 (octal) is displayed
804 as @samp{\230}. The display of character codes 0240 through 0377
805 (octal) may be either as escape sequences or as graphics. They do not
806 normally occur in multibyte buffers, but if they do, they are displayed
807 as Latin-1 graphics. In unibyte mode, if you enable European display
808 they are displayed using their graphics (assuming your terminal supports
809 them), otherwise as escape sequences. @xref{Single-Byte Character
813 @section Customization of Display
815 This section contains information for customization only. Beginning
816 users should skip it.
818 @vindex mode-line-inverse-video
819 The variable @code{mode-line-inverse-video} is an obsolete way of
820 controlling whether the mode line is displayed in inverse video; the
821 preferred way of doing this is to change the @code{mode-line} face.
822 @xref{Mode Line}. However, if @code{mode-line-inverse-video} has a
823 value of @code{nil}, then the @code{mode-line} face will be ignored,
824 and mode-lines will be drawn using the default text face.
827 @vindex inverse-video
828 If the variable @code{inverse-video} is non-@code{nil}, Emacs attempts
829 to invert all the lines of the display from what they normally are.
832 If the variable @code{visible-bell} is non-@code{nil}, Emacs attempts
833 to make the whole screen blink when it would normally make an audible bell
834 sound. This variable has no effect if your terminal does not have a way
835 to make the screen blink.@refill
837 @vindex no-redraw-on-reenter
838 When you reenter Emacs after suspending, Emacs normally clears the
839 screen and redraws the entire display. On some terminals with more than
840 one page of memory, it is possible to arrange the termcap entry so that
841 the @samp{ti} and @samp{te} strings (output to the terminal when Emacs
842 is entered and exited, respectively) switch between pages of memory so
843 as to use one page for Emacs and another page for other output. Then
844 you might want to set the variable @code{no-redraw-on-reenter}
845 non-@code{nil}; this tells Emacs to assume, when resumed, that the
846 screen page it is using still contains what Emacs last wrote there.
848 @vindex echo-keystrokes
849 The variable @code{echo-keystrokes} controls the echoing of multi-character
850 keys; its value is the number of seconds of pause required to cause echoing
851 to start, or zero meaning don't echo at all. @xref{Echo Area}.
854 If the variable @code{ctl-arrow} is @code{nil}, all control characters in
855 the buffer are displayed with octal escape sequences, except for newline
856 and tab. Altering the value of @code{ctl-arrow} makes it local to the
857 current buffer; until that time, the default value is in effect. The
858 default is initially @code{t}. @xref{Display Tables,, Display Tables,
859 elisp, The Emacs Lisp Reference Manual}.
862 Normally, a tab character in the buffer is displayed as whitespace which
863 extends to the next display tab stop position, and display tab stops come
864 at intervals equal to eight spaces. The number of spaces per tab is
865 controlled by the variable @code{tab-width}, which is made local by
866 changing it, just like @code{ctl-arrow}. Note that how the tab character
867 in the buffer is displayed has nothing to do with the definition of
868 @key{TAB} as a command. The variable @code{tab-width} must have an
869 integer value between 1 and 1000, inclusive.
871 @c @vindex truncate-lines @c No index entry here, because we have one
872 @c in the continuation section.
873 If the variable @code{truncate-lines} is non-@code{nil}, then each
874 line of text gets just one screen line for display; if the text line is
875 too long, display shows only the part that fits. If
876 @code{truncate-lines} is @code{nil}, then long text lines display as
877 more than one screen line, enough to show the whole text of the line.
878 @xref{Continuation Lines}. Altering the value of @code{truncate-lines}
879 makes it local to the current buffer; until that time, the default value
880 is in effect. The default is initially @code{nil}.
882 @c @vindex truncate-partial-width-windows @c Idx entry is in Split Windows.
883 If the variable @code{truncate-partial-width-windows} is
884 non-@code{nil}, it forces truncation rather than continuation in any
885 window less than the full width of the screen or frame, regardless of
886 the value of @code{truncate-lines}. For information about side-by-side
887 windows, see @ref{Split Window}. See also @ref{Display,, Display,
888 elisp, The Emacs Lisp Reference Manual}.
891 The variable @code{baud-rate} holds the output speed of the
892 terminal, as far as Emacs knows. Setting this variable does not
893 change the speed of actual data transmission, but the value is used
894 for calculations. On terminals, it affects padding, and decisions
895 about whether to scroll part of the screen or redraw it instead.
896 It also affects the behavior of incremental search.
898 On window-systems, @code{baud-rate} is only used to determine how
899 frequently to look for pending input during display updating. A
900 higher value of @code{baud-rate} means that check for pending input
901 will be done less frequently.
903 You can customize the way any particular character code is displayed
904 by means of a display table. @xref{Display Tables,, Display Tables,
905 elisp, The Emacs Lisp Reference Manual}.
907 @cindex hourglass pointer display
908 @vindex hourglass-delay
909 On a window system, Emacs can optionally display the mouse pointer
910 in a special shape to say that Emacs is busy. To turn this feature on
911 or off, customize the group @code{cursor}. You can also control the
912 amount of time Emacs must remain busy before the busy indicator is
913 displayed, by setting the variable @code{hourglass-delay}.
915 @findex tty-suppress-bold-inverse-default-colors
916 On some text-only terminals, bold face and inverse video together
917 result in text that is hard to read. Call the function
918 @code{tty-suppress-bold-inverse-default-colors} with a non-@code{nil}
919 argument to suppress the effect of bold-face in this case.
922 @section Displaying the Cursor
925 @findex global-hl-line-mode
926 @cindex highlight current line
927 @findex blink-cursor-mode
928 @cindex cursor, locating visually
929 @cindex cursor, blinking
930 There are a number of ways to customize the display of the cursor.
931 @kbd{M-x hl-line-mode} enables or disables a minor mode which
932 highlights the line containing point. @kbd{M-x global-hl-line-mode}
933 enables the minor mode globally. On window systems, the command
934 @kbd{M-x blink-cursor-mode} turns on or off the blinking of the
935 cursor. (On terminals, the terminal itself blinks the cursor, and
936 Emacs has no control over it.)
938 You can customize the cursor's color, and whether it blinks, using
939 the @code{cursor} Custom group (@pxref{Easy Customization}).
941 @vindex x-stretch-cursor
942 @cindex wide block cursor
943 When displaying on a window system, Emacs can optionally draw the
944 block cursor as wide as the character under the cursor---for example,
945 if the cursor is on a tab character, it would cover the full width
946 occupied by that tab character. To enable this feature, set the
947 variable @code{x-stretch-cursor} to a non-@code{nil} value.
949 @cindex cursor in non-selected windows
950 @vindex cursor-in-non-selected-windows
951 Normally, the cursor in non-selected windows is shown as a hollow box.
952 To turn off cursor display in non-selected windows, customize the option
953 @code{cursor-in-non-selected-windows} to assign it a @code{nil} value.