| 1 | @c This is part of the Emacs manual. |
| 2 | @c Copyright (C) 1985, 1986, 1987, 1993, 1994, 1995, 1997, 2000, 2001, |
| 3 | @c 2002, 2003, 2004, 2005 Free Software Foundation, Inc. |
| 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 |
| 14 | * Faces:: How to change the display style using faces. |
| 15 | * Standard Faces:: Emacs' predefined faces. |
| 16 | * Font Lock:: Minor mode for syntactic highlighting using faces. |
| 17 | * Highlight Interactively:: Tell Emacs what text to highlight. |
| 18 | * Highlight Changes:: Using colors to show where you changed the buffer. |
| 19 | * Scrolling:: Moving text up and down in a window. |
| 20 | * Horizontal Scrolling:: Moving text left and right in a window. |
| 21 | * Fringes:: Enabling or disabling window fringes. |
| 22 | * Useless Whitespace:: Showing possibly-spurious trailing whitespace. |
| 23 | * Follow Mode:: Follow mode lets two windows scroll as one. |
| 24 | * Selective Display:: Hiding lines with lots of indentation. |
| 25 | * Optional Mode Line:: Optional mode line display features. |
| 26 | * Text Display:: How text characters are normally displayed. |
| 27 | * Cursor Display:: Features for displaying the cursor. |
| 28 | * Display Custom:: Information on variables for customizing display. |
| 29 | @end menu |
| 30 | |
| 31 | @node Faces |
| 32 | @section Using Multiple Typefaces |
| 33 | @cindex faces |
| 34 | |
| 35 | You can specify various styles for displaying text using |
| 36 | @dfn{faces}. Each face can specify various @dfn{face attributes}, |
| 37 | such as the font family, the height, weight and slant of the |
| 38 | characters, the foreground and background color, and underlining or |
| 39 | overlining. A face does not have to specify all of these attributes; |
| 40 | often it inherits most of them from another face. |
| 41 | |
| 42 | On a window system, all the Emacs face attributes are meaningful. |
| 43 | On a character terminal, only some of them work. Some character |
| 44 | terminals support inverse video, bold, and underline attributes; some |
| 45 | support colors. Character terminals generally do not support changing |
| 46 | the height and width or the font family. |
| 47 | |
| 48 | The easiest way to use faces is to turn on Font Lock mode. |
| 49 | @xref{Font Lock}, for more information about Font Lock mode and |
| 50 | syntactic highlighting. You can print out the buffer with the |
| 51 | highlighting that appears on your screen using the command |
| 52 | @code{ps-print-buffer-with-faces}. @xref{PostScript}. |
| 53 | |
| 54 | Features which rely on text in multiple faces (such as Font Lock mode) |
| 55 | will also work on non-windowed terminals that can display more than one |
| 56 | face, whether by colors or underlining and emboldening. This includes |
| 57 | the console on GNU/Linux, an @code{xterm} which supports colors, the |
| 58 | MS-DOS display (@pxref{MS-DOS}), and the MS-Windows version invoked with |
| 59 | the @option{-nw} option. Emacs determines automatically whether the |
| 60 | terminal has this capability. |
| 61 | |
| 62 | You control the appearance of a part of the text in the buffer by |
| 63 | specifying the face or faces to use for it. The style of display used |
| 64 | for any given character is determined by combining the attributes of |
| 65 | all the applicable faces specified for that character. Any attribute |
| 66 | that isn't specified by these faces is taken from the @code{default} face, |
| 67 | whose attributes reflect the default settings of the frame itself. |
| 68 | |
| 69 | Enriched mode, the mode for editing formatted text, includes several |
| 70 | commands and menus for specifying faces for text in the buffer. |
| 71 | @xref{Format Faces}, for how to specify the font for text in the |
| 72 | buffer. @xref{Format Colors}, for how to specify the foreground and |
| 73 | background color. |
| 74 | |
| 75 | @cindex face colors, setting |
| 76 | @findex set-face-foreground |
| 77 | @findex set-face-background |
| 78 | To alter the appearance of a face, use the customization buffer. |
| 79 | @xref{Face Customization}. You can also use X resources to specify |
| 80 | attributes of particular faces (@pxref{Resources}). Alternatively, |
| 81 | you can change the foreground and background colors of a specific face |
| 82 | with @kbd{M-x set-face-foreground} and @kbd{M-x set-face-background}. |
| 83 | These commands prompt in the minibuffer for a face name and a color |
| 84 | name, with completion, and then set that face to use the specified |
| 85 | color. Changing the colors of the @code{default} face also changes |
| 86 | the foreground and background colors on all frames, both existing and |
| 87 | those to be created in the future. (You can also set foreground and |
| 88 | background colors for the current frame only; see @ref{Frame |
| 89 | Parameters}.) |
| 90 | |
| 91 | Emacs can correctly display variable-width fonts, but Emacs commands |
| 92 | that calculate width and indentation do not know how to calculate |
| 93 | variable widths. This can sometimes lead to incorrect results when |
| 94 | you use variable-width fonts. In particular, indentation commands can |
| 95 | give inconsistent results, so we recommend you avoid variable-width |
| 96 | fonts for editing program source code. Filling will sometimes make |
| 97 | lines too long or too short. We plan to address these issues in |
| 98 | future Emacs versions. |
| 99 | |
| 100 | @node Standard Faces |
| 101 | @section Standard Faces |
| 102 | |
| 103 | @findex list-faces-display |
| 104 | To see what faces are currently defined, and what they look like, |
| 105 | type @kbd{M-x list-faces-display}. It's possible for a given face to |
| 106 | look different in different frames; this command shows the appearance |
| 107 | in the frame in which you type it. |
| 108 | |
| 109 | Here are the standard faces for specifying text appearance. You can |
| 110 | use them on specific text, when you want the effects they produce. |
| 111 | |
| 112 | @table @code |
| 113 | @item default |
| 114 | This face is used for ordinary text that doesn't specify any other face. |
| 115 | @item bold |
| 116 | This face uses a bold variant of the default font, if it has one. |
| 117 | It's up to you to choose a default font that has a bold variant, |
| 118 | if you want to use one. |
| 119 | @item italic |
| 120 | This face uses an italic variant of the default font, if it has one. |
| 121 | @item bold-italic |
| 122 | This face uses a bold italic variant of the default font, if it has one. |
| 123 | @item underline |
| 124 | This face underlines text. |
| 125 | @item fixed-pitch |
| 126 | This face forces use of a particular fixed-width font. |
| 127 | @item variable-pitch |
| 128 | This face forces use of a particular variable-width font. It's |
| 129 | reasonable to customize this to use a different variable-width font, |
| 130 | if you like, but you should not make it a fixed-width font. |
| 131 | @item shadow |
| 132 | This face is used for making the text less noticeable than the surrounding |
| 133 | ordinary text. Usually this can be achieved by using shades of gray in |
| 134 | contrast with either black or white default foreground color. |
| 135 | @end table |
| 136 | |
| 137 | Here's an incomplete list of faces used to highlight parts of the |
| 138 | text temporarily for specific purposes. (Many other modes define |
| 139 | their own faces for this purpose.) |
| 140 | |
| 141 | @table @code |
| 142 | @item highlight |
| 143 | This face is used for highlighting portions of text, in various modes. |
| 144 | For example, mouse-sensitive text is highlighted using this face. |
| 145 | @item mode-line-highlight |
| 146 | Like @code{highlight}, but used for portions of text on mode lines. |
| 147 | @item isearch |
| 148 | This face is used for highlighting Isearch matches. |
| 149 | @item lazy-highlight |
| 150 | This face is used for lazy highlighting of Isearch and Query Replace |
| 151 | matches other than the current one. |
| 152 | @item region |
| 153 | This face is used for displaying a selected region (when Transient Mark |
| 154 | mode is enabled---see below). |
| 155 | @item secondary-selection |
| 156 | This face is used for displaying a secondary X selection (@pxref{Secondary |
| 157 | Selection}). |
| 158 | @item trailing-whitespace |
| 159 | The face for highlighting excess spaces and tabs at the end of a line |
| 160 | when @code{show-trailing-whitespace} is non-@code{nil}; see |
| 161 | @ref{Useless Whitespace}. |
| 162 | @item nobreak-space |
| 163 | The face for displaying the character ``nobreak space''. |
| 164 | @item escape-glyph |
| 165 | The face for highlighting the @samp{\} or @samp{^} that indicates |
| 166 | a control character. It's also used when @samp{\} indicates a |
| 167 | nobreak space or nobreak (soft) hyphen. |
| 168 | @end table |
| 169 | |
| 170 | @cindex @code{region} face |
| 171 | When Transient Mark mode is enabled, the text of the region is |
| 172 | highlighted when the mark is active. This uses the face named |
| 173 | @code{region}; you can control the style of highlighting by changing the |
| 174 | style of this face (@pxref{Face Customization}). @xref{Transient Mark}, |
| 175 | for more information about Transient Mark mode and activation and |
| 176 | deactivation of the mark. |
| 177 | |
| 178 | These faces control the appearance of parts of the Emacs frame. |
| 179 | They exist as faces to provide a consistent way to customize the |
| 180 | appearance of these parts of the frame. |
| 181 | |
| 182 | @table @code |
| 183 | @item mode-line |
| 184 | @itemx modeline |
| 185 | This face is used for the mode line of the currently selected window, |
| 186 | and for menu bars when toolkit menus are not used. By default, it's |
| 187 | drawn with shadows for a ``raised'' effect on window systems, and |
| 188 | drawn as the inverse of the default face on non-windowed terminals. |
| 189 | @code{modeline} is an alias for the @code{mode-line} face, for |
| 190 | compatibility with old Emacs versions. |
| 191 | @item mode-line-inactive |
| 192 | Like @code{mode-line}, but used for mode lines of the windows other |
| 193 | than the selected one (if @code{mode-line-in-non-selected-windows} is |
| 194 | non-@code{nil}). This face inherits from @code{mode-line}, so changes |
| 195 | in that face affect mode lines in all windows. |
| 196 | @item header-line |
| 197 | Similar to @code{mode-line} for a window's header line. Most modes |
| 198 | don't use the header line, but some special modes, such the Info mode, do. |
| 199 | @item vertical-border |
| 200 | This face is used for the vertical divider between windows. |
| 201 | By default this face inherits from the @code{mode-line-inactive} face |
| 202 | on character terminals. On window systems the foreground color of |
| 203 | this face is used for the vertical line between windows without |
| 204 | scrollbars. |
| 205 | @item minibuffer-prompt |
| 206 | @cindex @code{minibuffer-prompt} face |
| 207 | @vindex minibuffer-prompt-properties |
| 208 | This face is used for the prompt strings displayed in the minibuffer. |
| 209 | By default, Emacs automatically adds this face to the value of |
| 210 | @code{minibuffer-prompt-properties}, which is a list of text |
| 211 | properties used to display the prompt text. |
| 212 | @item fringe |
| 213 | @cindex @code{fringe} face |
| 214 | The face for the fringes to the left and right of windows on graphic |
| 215 | displays. (The fringes are the narrow portions of the Emacs frame |
| 216 | between the text area and the window's right and left borders.) |
| 217 | @xref{Fringes}. |
| 218 | @item scroll-bar |
| 219 | This face determines the visual appearance of the scroll bar. |
| 220 | @xref{Scroll Bars}. |
| 221 | @item border |
| 222 | This face determines the color of the frame border. |
| 223 | @item cursor |
| 224 | This face determines the color of the cursor. |
| 225 | @item mouse |
| 226 | This face determines the color of the mouse pointer. |
| 227 | @item tool-bar |
| 228 | This is the basic tool-bar face. No text appears in the tool bar, but the |
| 229 | colors of this face affect the appearance of tool bar icons. @xref{Tool Bars}. |
| 230 | @item tooltip |
| 231 | This face is used for tooltips. @xref{Tooltips}. |
| 232 | @item menu |
| 233 | @cindex menu bar appearance |
| 234 | @cindex @code{menu} face, no effect if customized |
| 235 | @cindex customization of @code{menu} face |
| 236 | This face determines the colors and font of Emacs's menus. @xref{Menu |
| 237 | Bars}. Setting the font of LessTif/Motif menus is currently not |
| 238 | supported; attempts to set the font are ignored in this case. |
| 239 | Likewise, attempts to customize this face in Emacs built with GTK and |
| 240 | in the MS-Windows port are ignored by the respective GUI toolkits; |
| 241 | you need to use system-wide styles and options to change the |
| 242 | appearance of the menus. |
| 243 | @end table |
| 244 | |
| 245 | @node Font Lock |
| 246 | @section Font Lock mode |
| 247 | @cindex Font Lock mode |
| 248 | @cindex mode, Font Lock |
| 249 | @cindex syntax highlighting and coloring |
| 250 | |
| 251 | Font Lock mode is a minor mode, always local to a particular buffer, |
| 252 | which highlights (or ``fontifies'') the buffer contents according to |
| 253 | the syntax of the text you are editing. It can recognize comments and |
| 254 | strings in most languages; in several languages, it can also recognize |
| 255 | and properly highlight various other important constructs---for |
| 256 | example, names of functions being defined or reserved keywords. |
| 257 | Some special modes, such as Occur mode and Info mode, have completely |
| 258 | specialized ways of assigning fonts for Font Lock mode. |
| 259 | |
| 260 | @findex font-lock-mode |
| 261 | Font Lock mode is turned on by default in all modes which support it. |
| 262 | You can toggle font-lock for each buffer with the command @kbd{M-x |
| 263 | font-lock-mode}. Using a positive argument unconditionally turns Font |
| 264 | Lock mode on, and a negative or zero argument turns it off. |
| 265 | |
| 266 | @findex global-font-lock-mode |
| 267 | @vindex global-font-lock-mode |
| 268 | If you do not wish Font Lock mode to be turned on by default, |
| 269 | customize the variable @code{global-font-lock-mode} using the Customize |
| 270 | interface (@pxref{Easy Customization}), or use the function |
| 271 | @code{global-font-lock-mode} in your @file{.emacs} file, like this: |
| 272 | |
| 273 | @example |
| 274 | (global-font-lock-mode 0) |
| 275 | @end example |
| 276 | |
| 277 | @findex turn-on-font-lock |
| 278 | If you have disabled Global Font Lock mode, you can still enable font |
| 279 | lock for specific major modes by adding the function |
| 280 | @code{turn-on-font-lock} to the mode hooks (@pxref{Hooks}). For |
| 281 | example, to enable Font Lock mode for editing C files, you can do this: |
| 282 | |
| 283 | @example |
| 284 | (add-hook 'c-mode-hook 'turn-on-font-lock) |
| 285 | @end example |
| 286 | |
| 287 | Font Lock mode uses several specifically named faces to do its job, |
| 288 | including @code{font-lock-string-face}, @code{font-lock-comment-face}, |
| 289 | and others. The easiest way to find them all is to use |
| 290 | @kbd{M-x customize-group @key{RET} font-lock-faces @key{RET}}. |
| 291 | |
| 292 | To change the colors or the fonts used by Font Lock mode to fontify |
| 293 | different parts of text, just change these faces. There are |
| 294 | two ways to do it: |
| 295 | |
| 296 | @itemize @bullet |
| 297 | @item |
| 298 | Invoke @kbd{M-x set-face-foreground} or @kbd{M-x set-face-background} |
| 299 | to change the colors of a particular face used by Font Lock. |
| 300 | @xref{Faces}. The command @kbd{M-x list-faces-display} displays all |
| 301 | the faces currently known to Emacs, including those used by Font Lock. |
| 302 | |
| 303 | @item |
| 304 | Customize the faces interactively with @kbd{M-x customize-face}, as |
| 305 | described in @ref{Face Customization}. |
| 306 | @end itemize |
| 307 | |
| 308 | @vindex font-lock-maximum-decoration |
| 309 | The variable @code{font-lock-maximum-decoration} specifies the |
| 310 | preferred level of fontification, for modes that provide multiple |
| 311 | levels. Level 1 is the least amount of fontification; some modes |
| 312 | support levels as high as 3. The normal default is ``as high as |
| 313 | possible.'' You can specify an integer, which applies to all modes, or |
| 314 | you can specify different numbers for particular major modes; for |
| 315 | example, to use level 1 for C/C++ modes, and the default level |
| 316 | otherwise, use this: |
| 317 | |
| 318 | @example |
| 319 | (setq font-lock-maximum-decoration |
| 320 | '((c-mode . 1) (c++-mode . 1))) |
| 321 | @end example |
| 322 | |
| 323 | @vindex font-lock-maximum-size |
| 324 | Fontification can be too slow for large buffers, so you can suppress |
| 325 | it. The variable @code{font-lock-maximum-size} specifies a buffer size, |
| 326 | beyond which buffer fontification is suppressed. |
| 327 | |
| 328 | @c @w is used below to prevent a bad page-break. |
| 329 | @vindex font-lock-beginning-of-syntax-function |
| 330 | @cindex incorrect fontification |
| 331 | @cindex parenthesis in column zero and fontification |
| 332 | @cindex brace in column zero and fontification |
| 333 | Comment and string fontification (or ``syntactic'' fontification) |
| 334 | relies on analysis of the syntactic structure of the buffer text. For |
| 335 | the sake of speed, some modes, including C mode and Lisp mode, |
| 336 | rely on a special convention: an open-parenthesis or open-brace in the |
| 337 | leftmost column always defines the @w{beginning} of a defun, and is |
| 338 | thus always outside any string or comment. (@xref{Left Margin |
| 339 | Paren}.) If you don't follow this convention, Font Lock mode can |
| 340 | misfontify the text that follows an open-parenthesis or open-brace in |
| 341 | the leftmost column that is inside a string or comment. |
| 342 | |
| 343 | @cindex slow display during scrolling |
| 344 | The variable @code{font-lock-beginning-of-syntax-function} (always |
| 345 | buffer-local) specifies how Font Lock mode can find a position |
| 346 | guaranteed to be outside any comment or string. In modes which use the |
| 347 | leftmost column parenthesis convention, the default value of the variable |
| 348 | is @code{beginning-of-defun}---that tells Font Lock mode to use the |
| 349 | convention. If you set this variable to @code{nil}, Font Lock no longer |
| 350 | relies on the convention. This avoids incorrect results, but the price |
| 351 | is that, in some cases, fontification for a changed text must rescan |
| 352 | buffer text from the beginning of the buffer. This can considerably |
| 353 | slow down redisplay while scrolling, particularly if you are close to |
| 354 | the end of a large buffer. |
| 355 | |
| 356 | @findex font-lock-add-keywords |
| 357 | Font Lock highlighting patterns already exist for many modes, but you |
| 358 | may want to fontify additional patterns. You can use the function |
| 359 | @code{font-lock-add-keywords}, to add your own highlighting patterns for |
| 360 | a particular mode. For example, to highlight @samp{FIXME:} words in C |
| 361 | comments, use this: |
| 362 | |
| 363 | @example |
| 364 | (font-lock-add-keywords |
| 365 | 'c-mode |
| 366 | '(("\\<\\(FIXME\\):" 1 font-lock-warning-face t))) |
| 367 | @end example |
| 368 | |
| 369 | @findex font-lock-remove-keywords |
| 370 | To remove keywords from the font-lock highlighting patterns, use the |
| 371 | function @code{font-lock-remove-keywords}. @xref{Search-based |
| 372 | Fontification,,, elisp, The Emacs Lisp Reference Manual}, for |
| 373 | documentation of the format of this list. |
| 374 | |
| 375 | @cindex just-in-time (JIT) font-lock |
| 376 | @cindex background syntax highlighting |
| 377 | Fontifying large buffers can take a long time. To avoid large |
| 378 | delays when a file is visited, Emacs fontifies only the visible |
| 379 | portion of a buffer. As you scroll through the buffer, each portion |
| 380 | that becomes visible is fontified as soon as it is displayed. The |
| 381 | parts of the buffer that are not displayed are fontified |
| 382 | ``stealthily,'' in the background, i.e.@: when Emacs is idle. You can |
| 383 | control this background fontification, also called @dfn{Just-In-Time} |
| 384 | (or @dfn{JIT}) Lock, by customizing variables in the customization |
| 385 | group @samp{jit-lock}. @xref{Specific Customization}. |
| 386 | |
| 387 | @node Highlight Interactively |
| 388 | @section Interactive Highlighting by Matching |
| 389 | @cindex highlighting by matching |
| 390 | @cindex interactive highlighting |
| 391 | |
| 392 | It is sometimes useful to highlight the strings that match a certain |
| 393 | regular expression. For example, you might wish to see all the |
| 394 | references to a certain variable in a program source file, or highlight |
| 395 | certain parts in a voluminous output of some program, or make certain |
| 396 | cliches stand out in an article. |
| 397 | |
| 398 | @findex hi-lock-mode |
| 399 | Use the @kbd{M-x hi-lock-mode} command to turn on a minor mode that |
| 400 | allows you to specify regular expressions of the text to be |
| 401 | highlighted. Hi-lock mode works like Font Lock (@pxref{Font Lock}), |
| 402 | except that it lets you specify explicitly what parts of text to |
| 403 | highlight. You control Hi-lock mode with these commands: |
| 404 | |
| 405 | @table @kbd |
| 406 | @item C-x w h @var{regexp} @key{RET} @var{face} @key{RET} |
| 407 | @kindex C-x w h |
| 408 | @findex highlight-regexp |
| 409 | Highlight text that matches |
| 410 | @var{regexp} using face @var{face} (@code{highlight-regexp}). |
| 411 | By using this command more than once, you can highlight various |
| 412 | parts of the text in different ways. |
| 413 | |
| 414 | @item C-x w r @var{regexp} @key{RET} |
| 415 | @kindex C-x w r |
| 416 | @findex unhighlight-regexp |
| 417 | Unhighlight @var{regexp} (@code{unhighlight-regexp}). You must enter |
| 418 | one of the regular expressions currently specified for highlighting. |
| 419 | (You can use completion, or choose from a menu, to enter one of them |
| 420 | conveniently.) |
| 421 | |
| 422 | @item C-x w l @var{regexp} @key{RET} @var{face} @key{RET} |
| 423 | @kindex C-x w l |
| 424 | @findex highlight-lines-matching-regexp |
| 425 | @cindex lines, highlighting |
| 426 | @cindex highlighting lines of text |
| 427 | Highlight entire lines containing a match for @var{regexp}, using face |
| 428 | @var{face} (@code{highlight-lines-matching-regexp}). |
| 429 | |
| 430 | @item C-x w b |
| 431 | @kindex C-x w b |
| 432 | @findex hi-lock-write-interactive-patterns |
| 433 | Insert all the current highlighting regexp/face pairs into the buffer |
| 434 | at point, with comment delimiters to prevent them from changing your |
| 435 | program. This key binding runs the |
| 436 | @code{hi-lock-write-interactive-patterns} command. |
| 437 | |
| 438 | These patterns will be read the next time you visit the file while |
| 439 | Hi-lock mode is enabled, or whenever you use the @kbd{M-x |
| 440 | hi-lock-find-patterns} command. |
| 441 | |
| 442 | @item C-x w i |
| 443 | @kindex C-x w i |
| 444 | @findex hi-lock-find-patterns |
| 445 | @vindex hi-lock-exclude-modes |
| 446 | Re-read regexp/face pairs in the current buffer |
| 447 | (@code{hi-lock-write-interactive-patterns}). The list of pairs is |
| 448 | found no matter where in the buffer it may be. |
| 449 | |
| 450 | This command does nothing if the major mode is a member of the list |
| 451 | @code{hi-lock-exclude-modes}. |
| 452 | @end table |
| 453 | |
| 454 | @node Highlight Changes |
| 455 | @section Highlight Changes Mode |
| 456 | |
| 457 | @findex highlight-changes-mode |
| 458 | Use @kbd{M-x highlight-changes-mode} to enable a minor mode |
| 459 | that uses faces (colors, typically) to indicate which parts of |
| 460 | the buffer were changed most recently. |
| 461 | |
| 462 | @node Scrolling |
| 463 | @section Scrolling |
| 464 | |
| 465 | If a buffer contains text that is too large to fit entirely within a |
| 466 | window that is displaying the buffer, Emacs shows a contiguous portion of |
| 467 | the text. The portion shown always contains point. |
| 468 | |
| 469 | @cindex scrolling |
| 470 | @dfn{Scrolling} means moving text up or down in the window so that |
| 471 | different parts of the text are visible. Scrolling forward means that text |
| 472 | moves up, and new text appears at the bottom. Scrolling backward moves |
| 473 | text down and new text appears at the top. |
| 474 | |
| 475 | Scrolling happens automatically if you move point past the bottom or top |
| 476 | of the window. You can also explicitly request scrolling with the commands |
| 477 | in this section. |
| 478 | |
| 479 | @table @kbd |
| 480 | @item C-l |
| 481 | Clear screen and redisplay, scrolling the selected window to center |
| 482 | point vertically within it (@code{recenter}). |
| 483 | @item C-v |
| 484 | Scroll forward (a windowful or a specified number of lines) (@code{scroll-up}). |
| 485 | @item @key{NEXT} |
| 486 | @itemx @key{PAGEDOWN} |
| 487 | Likewise, scroll forward. |
| 488 | @item M-v |
| 489 | Scroll backward (@code{scroll-down}). |
| 490 | @item @key{PRIOR} |
| 491 | @itemx @key{PAGEUP} |
| 492 | Likewise, scroll backward. |
| 493 | @item @var{arg} C-l |
| 494 | Scroll so point is on line @var{arg} (@code{recenter}). |
| 495 | @item C-M-l |
| 496 | Scroll heuristically to bring useful information onto the screen |
| 497 | (@code{reposition-window}). |
| 498 | @end table |
| 499 | |
| 500 | @kindex C-l |
| 501 | @findex recenter |
| 502 | The most basic scrolling command is @kbd{C-l} (@code{recenter}) with |
| 503 | no argument. It scrolls the selected window so that point is halfway |
| 504 | down from the top of the window. On a text terminal, it also clears |
| 505 | the screen and redisplays all windows. That is useful in case the |
| 506 | screen is garbled (@pxref{Screen Garbled}). |
| 507 | |
| 508 | @kindex C-v |
| 509 | @kindex M-v |
| 510 | @kindex NEXT |
| 511 | @kindex PRIOR |
| 512 | @kindex PAGEDOWN |
| 513 | @kindex PAGEUP |
| 514 | @findex scroll-up |
| 515 | @findex scroll-down |
| 516 | @vindex next-screen-context-lines |
| 517 | To read the buffer a windowful at a time, use @kbd{C-v} |
| 518 | (@code{scroll-up}) with no argument. This scrolls forward by nearly |
| 519 | the whole window height. The effect is to take the two lines at the |
| 520 | bottom of the window and put them at the top, followed by nearly a |
| 521 | whole windowful of lines that were not previously visible. If point |
| 522 | was in the text that scrolled off the top, it ends up at the new top |
| 523 | of the window. |
| 524 | |
| 525 | @kbd{M-v} (@code{scroll-down}) with no argument scrolls backward in |
| 526 | a similar way, also with overlap. The number of lines of overlap |
| 527 | across a @kbd{C-v} or @kbd{M-v} is controlled by the variable |
| 528 | @code{next-screen-context-lines}; by default, it is 2. The function |
| 529 | keys @key{NEXT} and @key{PRIOR}, or @key{PAGEDOWN} and @key{PAGEUP}, |
| 530 | are equivalent to @kbd{C-v} and @kbd{M-v}. |
| 531 | |
| 532 | The commands @kbd{C-v} and @kbd{M-v} with a numeric argument scroll |
| 533 | the text in the selected window up or down a few lines. @kbd{C-v} |
| 534 | with an argument moves the text and point up, together, that many |
| 535 | lines; it brings the same number of new lines into view at the bottom |
| 536 | of the window. @kbd{M-v} with numeric argument scrolls the text |
| 537 | downward, bringing that many new lines into view at the top of the |
| 538 | window. @kbd{C-v} with a negative argument is like @kbd{M-v} and vice |
| 539 | versa. |
| 540 | |
| 541 | The names of scroll commands are based on the direction that the |
| 542 | text moves in the window. Thus, the command to scroll forward is |
| 543 | called @code{scroll-up} because it moves the text upward on the |
| 544 | screen. The keys @key{PAGEDOWN} and @key{PAGEUP} derive their names |
| 545 | and customary meanings from a different convention that developed |
| 546 | elsewhere; hence the strange result that @key{PAGEDOWN} runs |
| 547 | @code{scroll-up}. |
| 548 | |
| 549 | @vindex scroll-preserve-screen-position |
| 550 | Some users like the full-screen scroll commands to keep point at the |
| 551 | same screen line. To enable this behavior, set the variable |
| 552 | @code{scroll-preserve-screen-position} to a non-@code{nil} value. In |
| 553 | this mode, when scrolling shifts point off the screen, or into the |
| 554 | scrolling margins, Emacs moves point to keep the same vertical |
| 555 | position within the window. This mode is convenient for browsing |
| 556 | through a file by scrolling by screenfuls; if you come back to the |
| 557 | screen where you started, point goes back to the line where it |
| 558 | started. However, this mode is inconvenient when you move to the next |
| 559 | screen in order to move point to the text there. |
| 560 | |
| 561 | Another way to do scrolling is with @kbd{C-l} with a numeric argument. |
| 562 | @kbd{C-l} does not clear the screen when given an argument; it only scrolls |
| 563 | the selected window. With a positive argument @var{n}, it repositions text |
| 564 | to put point @var{n} lines down from the top. An argument of zero puts |
| 565 | point on the very top line. Point does not move with respect to the text; |
| 566 | rather, the text and point move rigidly on the screen. @kbd{C-l} with a |
| 567 | negative argument puts point that many lines from the bottom of the window. |
| 568 | For example, @kbd{C-u - 1 C-l} puts point on the bottom line, and @kbd{C-u |
| 569 | - 5 C-l} puts it five lines from the bottom. @kbd{C-u C-l} scrolls to put |
| 570 | point at the center (vertically) of the selected window. |
| 571 | |
| 572 | @kindex C-M-l |
| 573 | @findex reposition-window |
| 574 | The @kbd{C-M-l} command (@code{reposition-window}) scrolls the current |
| 575 | window heuristically in a way designed to get useful information onto |
| 576 | the screen. For example, in a Lisp file, this command tries to get the |
| 577 | entire current defun onto the screen if possible. |
| 578 | |
| 579 | @vindex scroll-conservatively |
| 580 | Scrolling happens automatically when point moves out of the visible |
| 581 | portion of the text. Normally, automatic scrolling centers point |
| 582 | vertically within the window. However, if you set |
| 583 | @code{scroll-conservatively} to a small number @var{n}, then if you |
| 584 | move point just a little off the screen---less than @var{n} |
| 585 | lines---then Emacs scrolls the text just far enough to bring point |
| 586 | back on screen. By default, @code{scroll-conservatively} is 0. |
| 587 | |
| 588 | @cindex aggressive scrolling |
| 589 | @vindex scroll-up-aggressively |
| 590 | @vindex scroll-down-aggressively |
| 591 | When the window does scroll by a longer distance, you can control |
| 592 | how aggressively it scrolls, by setting the variables |
| 593 | @code{scroll-up-aggressively} and @code{scroll-down-aggressively}. |
| 594 | The value of @code{scroll-up-aggressively} should be either |
| 595 | @code{nil}, or a fraction @var{f} between 0 and 1. A fraction |
| 596 | specifies where on the screen to put point when scrolling upward. |
| 597 | More precisely, when a window scrolls up because point is above the |
| 598 | window start, the new start position is chosen to put point @var{f} |
| 599 | part of the window height from the top. The larger @var{f}, the more |
| 600 | aggressive the scrolling. |
| 601 | |
| 602 | @code{nil}, which is the default, scrolls to put point at the center. |
| 603 | So it is equivalent to .5. |
| 604 | |
| 605 | Likewise, @code{scroll-down-aggressively} is used for scrolling |
| 606 | down. The value, @var{f}, specifies how far point should be placed |
| 607 | from the bottom of the window; thus, as with |
| 608 | @code{scroll-up-aggressively}, a larger value is more aggressive. |
| 609 | |
| 610 | @vindex scroll-margin |
| 611 | The variable @code{scroll-margin} restricts how close point can come |
| 612 | to the top or bottom of a window. Its value is a number of screen |
| 613 | lines; if point comes within that many lines of the top or bottom of the |
| 614 | window, Emacs recenters the window. By default, @code{scroll-margin} is |
| 615 | 0. |
| 616 | |
| 617 | @node Horizontal Scrolling |
| 618 | @section Horizontal Scrolling |
| 619 | @cindex horizontal scrolling |
| 620 | |
| 621 | @dfn{Horizontal scrolling} means shifting all the lines sideways |
| 622 | within a window---so that some of the text near the left margin is not |
| 623 | displayed at all. When the text in a window is scrolled horizontally, |
| 624 | text lines are truncated rather than continued (@pxref{Display |
| 625 | Custom}). Whenever a window shows truncated lines, Emacs |
| 626 | automatically updates its horizontal scrolling whenever point moves |
| 627 | off the left or right edge of the screen. You can also use these |
| 628 | commands to do explicit horizontal scrolling. |
| 629 | |
| 630 | @table @kbd |
| 631 | @item C-x < |
| 632 | Scroll text in current window to the left (@code{scroll-left}). |
| 633 | @item C-x > |
| 634 | Scroll to the right (@code{scroll-right}). |
| 635 | @end table |
| 636 | |
| 637 | @kindex C-x < |
| 638 | @kindex C-x > |
| 639 | @findex scroll-left |
| 640 | @findex scroll-right |
| 641 | The command @kbd{C-x <} (@code{scroll-left}) scrolls the selected |
| 642 | window to the left by @var{n} columns with argument @var{n}. This moves |
| 643 | part of the beginning of each line off the left edge of the window. |
| 644 | With no argument, it scrolls by almost the full width of the window (two |
| 645 | columns less, to be precise). |
| 646 | |
| 647 | @kbd{C-x >} (@code{scroll-right}) scrolls similarly to the right. The |
| 648 | window cannot be scrolled any farther to the right once it is displayed |
| 649 | normally (with each line starting at the window's left margin); |
| 650 | attempting to do so has no effect. This means that you don't have to |
| 651 | calculate the argument precisely for @w{@kbd{C-x >}}; any sufficiently large |
| 652 | argument will restore the normal display. |
| 653 | |
| 654 | If you use those commands to scroll a window horizontally, that sets |
| 655 | a lower bound for automatic horizontal scrolling. Automatic scrolling |
| 656 | will continue to scroll the window, but never farther to the right |
| 657 | than the amount you previously set by @code{scroll-left}. |
| 658 | |
| 659 | @vindex hscroll-margin |
| 660 | The value of the variable @code{hscroll-margin} controls how close |
| 661 | to the window's edges point is allowed to get before the window will |
| 662 | be automatically scrolled. It is measured in columns. If the value |
| 663 | is 5, then moving point within 5 columns of the edge causes horizontal |
| 664 | scrolling away from that edge. |
| 665 | |
| 666 | @vindex hscroll-step |
| 667 | The variable @code{hscroll-step} determines how many columns to |
| 668 | scroll the window when point gets too close to the edge. If it's |
| 669 | zero, horizontal scrolling centers point horizontally within the |
| 670 | window. If it's a positive integer, it specifies the number of |
| 671 | columns to scroll by. If it's a floating-point number, it specifies |
| 672 | the fraction of the window's width to scroll by. The default is zero. |
| 673 | |
| 674 | @vindex auto-hscroll-mode |
| 675 | To disable automatic horizontal scrolling, set the variable |
| 676 | @code{auto-hscroll-mode} to @code{nil}. |
| 677 | |
| 678 | @node Fringes |
| 679 | @section Window Fringes |
| 680 | @cindex fringes |
| 681 | |
| 682 | On a graphical display, each Emacs window normally has narrow |
| 683 | @dfn{fringes} on the left and right edges. The fringes display |
| 684 | indications about the text in the window. |
| 685 | |
| 686 | The most common use of the fringes is to indicate a continuation |
| 687 | line, when one line of text is split into multiple lines on the |
| 688 | screen. The left fringe shows a curving arrow for each screen line |
| 689 | except the first, indicating that ``this is not the real beginning.'' |
| 690 | The right fringe shows a curving arrow for each screen line except the |
| 691 | last, indicating that ``this is not the real end.'' |
| 692 | |
| 693 | The fringes indicate line truncation with short horizontal arrows |
| 694 | meaning ``there's more text on this line which is scrolled |
| 695 | horizontally out of view;'' clicking the mouse on one of the arrows |
| 696 | scrolls the display horizontally in the direction of the arrow. The |
| 697 | fringes can also indicate other things, such as empty lines, or where a |
| 698 | program you are debugging is executing (@pxref{Debuggers}). |
| 699 | |
| 700 | @findex set-fringe-style |
| 701 | @findex fringe-mode |
| 702 | You can enable and disable the fringes for all frames using |
| 703 | @kbd{M-x fringe-mode}. To enable and disable the fringes |
| 704 | for the selected frame, use @kbd{M-x set-fringe-style}. |
| 705 | |
| 706 | @node Useless Whitespace |
| 707 | @section Useless Whitespace |
| 708 | |
| 709 | @cindex trailing whitespace |
| 710 | @cindex whitespace, trailing |
| 711 | @vindex show-trailing-whitespace |
| 712 | It is easy to leave unnecessary spaces at the end of a line, or |
| 713 | empty lines at the end of a file, without realizing it. In most |
| 714 | cases, this @dfn{trailing whitespace} has no effect, but there are |
| 715 | special circumstances where it matters. |
| 716 | |
| 717 | You can make trailing whitespace at the end of a line visible on the |
| 718 | screen by setting the buffer-local variable |
| 719 | @code{show-trailing-whitespace} to @code{t}. Then Emacs displays |
| 720 | trailing whitespace in the face @code{trailing-whitespace}. |
| 721 | |
| 722 | This feature does not apply when point is at the end of the line |
| 723 | containing the whitespace. Strictly speaking, that is ``trailing |
| 724 | whitespace'' nonetheless, but displaying it specially in that case |
| 725 | looks ugly while you are typing in new text. In this special case, |
| 726 | the location of point is enough to show you that the spaces are |
| 727 | present. |
| 728 | |
| 729 | @findex delete-trailing-whitespace |
| 730 | To delete all trailing whitespace within the current buffer's |
| 731 | accessible portion (@pxref{Narrowing}), type @kbd{M-x |
| 732 | delete-trailing-whitespace @key{RET}}. (This command does not remove |
| 733 | the form-feed characters.) |
| 734 | |
| 735 | @vindex indicate-empty-lines |
| 736 | @vindex default-indicate-empty-lines |
| 737 | @cindex unused lines |
| 738 | @cindex fringes, and unused line indication |
| 739 | Emacs can indicate unused lines at the end of the window with a |
| 740 | small image in the left fringe (@pxref{Fringes}). The image appears |
| 741 | for window lines that do not correspond to any buffer text. Blank |
| 742 | lines at the end of the buffer then stand out because they do not have |
| 743 | this image in the fringe. |
| 744 | |
| 745 | To enable this feature, set the buffer-local variable |
| 746 | @code{indicate-empty-lines} to a non-@code{nil} value. The default |
| 747 | value of this variable is controlled by the variable |
| 748 | @code{default-indicate-empty-lines}; by setting that variable, you |
| 749 | can enable or disable this feature for all new buffers. (This feature |
| 750 | currently doesn't work on character terminals.) |
| 751 | |
| 752 | @node Follow Mode |
| 753 | @section Follow Mode |
| 754 | @cindex Follow mode |
| 755 | @cindex mode, Follow |
| 756 | @findex follow-mode |
| 757 | @cindex windows, synchronizing |
| 758 | @cindex synchronizing windows |
| 759 | |
| 760 | @dfn{Follow mode} is a minor mode that makes two windows, both |
| 761 | showing the same buffer, scroll as a single tall ``virtual window.'' |
| 762 | To use Follow mode, go to a frame with just one window, split it into |
| 763 | two side-by-side windows using @kbd{C-x 3}, and then type @kbd{M-x |
| 764 | follow-mode}. From then on, you can edit the buffer in either of the |
| 765 | two windows, or scroll either one; the other window follows it. |
| 766 | |
| 767 | In Follow mode, if you move point outside the portion visible in one |
| 768 | window and into the portion visible in the other window, that selects |
| 769 | the other window---again, treating the two as if they were parts of |
| 770 | one large window. |
| 771 | |
| 772 | To turn off Follow mode, type @kbd{M-x follow-mode} a second time. |
| 773 | |
| 774 | @node Selective Display |
| 775 | @section Selective Display |
| 776 | @cindex selective display |
| 777 | @findex set-selective-display |
| 778 | @kindex C-x $ |
| 779 | |
| 780 | Emacs has the ability to hide lines indented more than a certain number |
| 781 | of columns (you specify how many columns). You can use this to get an |
| 782 | overview of a part of a program. |
| 783 | |
| 784 | To hide lines in the current buffer, type @kbd{C-x $} |
| 785 | (@code{set-selective-display}) with a numeric argument @var{n}. Then |
| 786 | lines with at least @var{n} columns of indentation disappear from the |
| 787 | screen. The only indication of their presence is that three dots |
| 788 | (@samp{@dots{}}) appear at the end of each visible line that is |
| 789 | followed by one or more hidden ones. |
| 790 | |
| 791 | The commands @kbd{C-n} and @kbd{C-p} move across the hidden lines as |
| 792 | if they were not there. |
| 793 | |
| 794 | The hidden lines are still present in the buffer, and most editing |
| 795 | commands see them as usual, so you may find point in the middle of the |
| 796 | hidden text. When this happens, the cursor appears at the end of the |
| 797 | previous line, after the three dots. If point is at the end of the |
| 798 | visible line, before the newline that ends it, the cursor appears before |
| 799 | the three dots. |
| 800 | |
| 801 | To make all lines visible again, type @kbd{C-x $} with no argument. |
| 802 | |
| 803 | @vindex selective-display-ellipses |
| 804 | If you set the variable @code{selective-display-ellipses} to |
| 805 | @code{nil}, the three dots do not appear at the end of a line that |
| 806 | precedes hidden lines. Then there is no visible indication of the |
| 807 | hidden lines. This variable becomes local automatically when set. |
| 808 | |
| 809 | See also @ref{Outline Mode} for another way to hide part of |
| 810 | the text in a buffer. |
| 811 | |
| 812 | @node Optional Mode Line |
| 813 | @section Optional Mode Line Features |
| 814 | |
| 815 | @cindex buffer size display |
| 816 | @cindex display of buffer size |
| 817 | @findex size-indication-mode |
| 818 | The buffer percentage @var{pos} indicates the percentage of the |
| 819 | buffer above the top of the window. You can additionally display the |
| 820 | size of the buffer by typing @kbd{M-x size-indication-mode} to turn on |
| 821 | Size Indication mode. The size will be displayed immediately |
| 822 | following the buffer percentage like this: |
| 823 | |
| 824 | @example |
| 825 | @var{POS} of @var{SIZE} |
| 826 | @end example |
| 827 | |
| 828 | @noindent |
| 829 | Here @var{SIZE} is the human readable representation of the number of |
| 830 | characters in the buffer, which means that @samp{k} for 10^3, @samp{M} |
| 831 | for 10^6, @samp{G} for 10^9, etc., are used to abbreviate. |
| 832 | |
| 833 | @cindex narrowing, and buffer size display |
| 834 | If you have narrowed the buffer (@pxref{Narrowing}), the size of the |
| 835 | accessible part of the buffer is shown. |
| 836 | |
| 837 | @cindex line number display |
| 838 | @cindex display of line number |
| 839 | @findex line-number-mode |
| 840 | The current line number of point appears in the mode line when Line |
| 841 | Number mode is enabled. Use the command @kbd{M-x line-number-mode} to |
| 842 | turn this mode on and off; normally it is on. The line number appears |
| 843 | after the buffer percentage @var{pos}, with the letter @samp{L} to |
| 844 | indicate what it is. @xref{Minor Modes}, for more information about |
| 845 | minor modes and about how to use this command. |
| 846 | |
| 847 | @cindex narrowing, and line number display |
| 848 | If you have narrowed the buffer (@pxref{Narrowing}), the displayed |
| 849 | line number is relative to the accessible portion of the buffer. |
| 850 | |
| 851 | @vindex line-number-display-limit |
| 852 | If the buffer is very large (larger than the value of |
| 853 | @code{line-number-display-limit}), then the line number doesn't appear. |
| 854 | Emacs doesn't compute the line number when the buffer is large, because |
| 855 | that would be too slow. Set it to @code{nil} to remove the limit. |
| 856 | |
| 857 | @vindex line-number-display-limit-width |
| 858 | Line-number computation can also be slow if the lines in the buffer |
| 859 | are too long. For this reason, Emacs normally doesn't display line |
| 860 | numbers if the average width, in characters, of lines near point is |
| 861 | larger than the value of the variable |
| 862 | @code{line-number-display-limit-width}. The default value is 200 |
| 863 | characters. |
| 864 | |
| 865 | @cindex Column Number mode |
| 866 | @cindex mode, Column Number |
| 867 | @findex column-number-mode |
| 868 | You can also display the current column number by turning on Column |
| 869 | Number mode. It displays the current column number preceded by the |
| 870 | letter @samp{C}. Type @kbd{M-x column-number-mode} to toggle this mode. |
| 871 | |
| 872 | @findex display-time |
| 873 | @cindex time (on mode line) |
| 874 | Emacs can optionally display the time and system load in all mode |
| 875 | lines. To enable this feature, type @kbd{M-x display-time} or customize |
| 876 | the option @code{display-time-mode}. The information added to the mode |
| 877 | line usually appears after the buffer name, before the mode names and |
| 878 | their parentheses. It looks like this: |
| 879 | |
| 880 | @example |
| 881 | @var{hh}:@var{mm}pm @var{l.ll} |
| 882 | @end example |
| 883 | |
| 884 | @noindent |
| 885 | @vindex display-time-24hr-format |
| 886 | Here @var{hh} and @var{mm} are the hour and minute, followed always by |
| 887 | @samp{am} or @samp{pm}. @var{l.ll} is the average number of running |
| 888 | processes in the whole system recently. (Some fields may be missing if |
| 889 | your operating system cannot support them.) If you prefer time display |
| 890 | in 24-hour format, set the variable @code{display-time-24hr-format} |
| 891 | to @code{t}. |
| 892 | |
| 893 | @cindex mail (on mode line) |
| 894 | @vindex display-time-use-mail-icon |
| 895 | @vindex display-time-mail-face |
| 896 | @vindex display-time-mail-file |
| 897 | @vindex display-time-mail-directory |
| 898 | The word @samp{Mail} appears after the load level if there is mail |
| 899 | for you that you have not read yet. On a graphical display you can use |
| 900 | an icon instead of @samp{Mail} by customizing |
| 901 | @code{display-time-use-mail-icon}; this may save some space on the mode |
| 902 | line. You can customize @code{display-time-mail-face} to make the mail |
| 903 | indicator prominent. Use @code{display-time-mail-file} to specify |
| 904 | the mail file to check, or set @code{display-time-mail-directory} |
| 905 | to specify the directory to check for incoming mail (any nonempty regular |
| 906 | file in the directory is considered as ``newly arrived mail''). |
| 907 | |
| 908 | @cindex mode line, 3D appearance |
| 909 | @cindex attributes of mode line, changing |
| 910 | @cindex non-integral number of lines in a window |
| 911 | By default, the mode line is drawn on graphics displays with |
| 912 | 3D-style highlighting, like that of a button when it is not being |
| 913 | pressed. If you don't like this effect, you can disable the 3D |
| 914 | highlighting of the mode line, by customizing the attributes of the |
| 915 | @code{mode-line} face in your @file{.emacs} init file, like this: |
| 916 | |
| 917 | @example |
| 918 | (set-face-attribute 'mode-line nil :box nil) |
| 919 | @end example |
| 920 | |
| 921 | @noindent |
| 922 | Alternatively, you can turn off the box attribute in your |
| 923 | @file{.Xdefaults} file: |
| 924 | |
| 925 | @example |
| 926 | Emacs.mode-line.AttributeBox: off |
| 927 | @end example |
| 928 | |
| 929 | @cindex non-selected windows, mode line appearance |
| 930 | By default, the mode line of nonselected windows is displayed in a |
| 931 | different face, called @code{mode-line-inactive}. Only the selected |
| 932 | window is displayed in the @code{mode-line} face. This helps show |
| 933 | which window is selected. When the minibuffer is selected, since |
| 934 | it has no mode line, the window from which you activated the minibuffer |
| 935 | has its mode line displayed using @code{mode-line}; as a result, |
| 936 | ordinary entry to the minibuffer does not change any mode lines. |
| 937 | |
| 938 | @vindex mode-line-in-non-selected-windows |
| 939 | You can disable use of @code{mode-line-inactive} by setting variable |
| 940 | @code{mode-line-in-non-selected-windows} to @code{nil}; then all mode |
| 941 | lines are displayed in the @code{mode-line} face. |
| 942 | |
| 943 | @node Text Display |
| 944 | @section How Text Is Displayed |
| 945 | @cindex characters (in text) |
| 946 | |
| 947 | @acronym{ASCII} printing characters (octal codes 040 through 0176) in Emacs |
| 948 | buffers are displayed with their graphics, as are non-ASCII multibyte |
| 949 | printing characters (octal codes above 0400). |
| 950 | |
| 951 | Some @acronym{ASCII} control characters are displayed in special ways. The |
| 952 | newline character (octal code 012) is displayed by starting a new line. |
| 953 | The tab character (octal code 011) is displayed by moving to the next |
| 954 | tab stop column (normally every 8 columns). |
| 955 | |
| 956 | Other @acronym{ASCII} control characters are normally displayed as a caret |
| 957 | (@samp{^}) followed by the non-control version of the character; thus, |
| 958 | control-A is displayed as @samp{^A}. |
| 959 | |
| 960 | Non-@acronym{ASCII} characters 0200 through 0237 (octal) are displayed with |
| 961 | octal escape sequences; thus, character code 0230 (octal) is displayed |
| 962 | as @samp{\230}. The display of character codes 0240 through 0377 |
| 963 | (octal) may be either as escape sequences or as graphics. They do not |
| 964 | normally occur in multibyte buffers, but if they do, they are displayed |
| 965 | as Latin-1 graphics. In unibyte mode, if you enable European display |
| 966 | they are displayed using their graphics (assuming your terminal supports |
| 967 | them), otherwise as escape sequences. @xref{Single-Byte Character |
| 968 | Support}. |
| 969 | |
| 970 | @vindex nobreak-char-display |
| 971 | @cindex no-break space, display |
| 972 | @cindex no-break hyphen, display |
| 973 | @cindex soft hyphen, display |
| 974 | Some character sets define ``no-break'' versions of the space and |
| 975 | hyphen characters, which are used where a line should not be broken. |
| 976 | Emacs normally displays these characters with special faces |
| 977 | (respectively, @code{nobreak-space} and @code{escape-glyph}) to |
| 978 | distinguish them from ordinary spaces and hyphens. You can turn off |
| 979 | this feature by setting the variable @code{nobreak-char-display} to |
| 980 | @code{nil}. If you set the variable to any other value, that means to |
| 981 | prefix these characters with an escape character. |
| 982 | |
| 983 | @node Cursor Display |
| 984 | @section Displaying the Cursor |
| 985 | |
| 986 | @findex blink-cursor-mode |
| 987 | @vindex blink-cursor-alist |
| 988 | @cindex cursor, locating visually |
| 989 | @cindex cursor, blinking |
| 990 | You can customize the cursor's color, and whether it blinks, using |
| 991 | the @code{cursor} Custom group (@pxref{Easy Customization}). On |
| 992 | graphical terminals, the command @kbd{M-x blink-cursor-mode} enables |
| 993 | or disables the blinking of the cursor. (On text terminals, the |
| 994 | terminal itself blinks the cursor, and Emacs has no control over it.) |
| 995 | You can control how the cursor appears when it blinks off by setting |
| 996 | the variable @code{blink-cursor-alist}. |
| 997 | |
| 998 | @cindex cursor in non-selected windows |
| 999 | @vindex cursor-in-non-selected-windows |
| 1000 | Normally, the cursor appears in non-selected windows in the ``off'' |
| 1001 | state, with the same appearance as when the blinking cursor blinks |
| 1002 | ``off''. For a box cursor, this is a hollow box; for a bar cursor, |
| 1003 | this is a thinner bar. To turn off cursors in non-selected windows, |
| 1004 | customize the variable @code{cursor-in-non-selected-windows} and assign |
| 1005 | it a @code{nil} value. |
| 1006 | |
| 1007 | @vindex x-stretch-cursor |
| 1008 | @cindex wide block cursor |
| 1009 | On graphical terminals, Emacs can optionally draw the block cursor |
| 1010 | as wide as the character under the cursor---for example, if the cursor |
| 1011 | is on a tab character, it would cover the full width occupied by that |
| 1012 | tab character. To enable this feature, set the variable |
| 1013 | @code{x-stretch-cursor} to a non-@code{nil} value. |
| 1014 | |
| 1015 | @findex hl-line-mode |
| 1016 | @findex global-hl-line-mode |
| 1017 | @cindex highlight current line |
| 1018 | If you find it hard to see the cursor, you might like HL Line mode, |
| 1019 | a minor mode that highlights the line containing point. Use @kbd{M-x |
| 1020 | hl-line-mode} to enable or disable it in the current buffer. @kbd{M-x |
| 1021 | global-hl-line-mode} enables or disables the same mode globally. |
| 1022 | |
| 1023 | @node Display Custom |
| 1024 | @section Customization of Display |
| 1025 | |
| 1026 | This section contains information for customization only. Beginning |
| 1027 | users should skip it. |
| 1028 | |
| 1029 | @vindex inverse-video |
| 1030 | If the variable @code{inverse-video} is non-@code{nil}, Emacs attempts |
| 1031 | to invert all the lines of the display from what they normally are. |
| 1032 | |
| 1033 | @vindex visible-bell |
| 1034 | If the variable @code{visible-bell} is non-@code{nil}, Emacs attempts |
| 1035 | to make the whole screen blink when it would normally make an audible bell |
| 1036 | sound. This variable has no effect if your terminal does not have a way |
| 1037 | to make the screen blink. |
| 1038 | |
| 1039 | @vindex no-redraw-on-reenter |
| 1040 | On a text terminal, when you reenter Emacs after suspending, Emacs |
| 1041 | normally clears the screen and redraws the entire display. On some |
| 1042 | terminals with more than one page of memory, it is possible to arrange |
| 1043 | the termcap entry so that the @samp{ti} and @samp{te} strings (output |
| 1044 | to the terminal when Emacs is entered and exited, respectively) switch |
| 1045 | between pages of memory so as to use one page for Emacs and another |
| 1046 | page for other output. Then you might want to set the variable |
| 1047 | @code{no-redraw-on-reenter} non-@code{nil}; this tells Emacs to |
| 1048 | assume, when resumed, that the screen page it is using still contains |
| 1049 | what Emacs last wrote there. |
| 1050 | |
| 1051 | @vindex echo-keystrokes |
| 1052 | The variable @code{echo-keystrokes} controls the echoing of multi-character |
| 1053 | keys; its value is the number of seconds of pause required to cause echoing |
| 1054 | to start, or zero meaning don't echo at all. @xref{Echo Area}. |
| 1055 | |
| 1056 | @vindex ctl-arrow |
| 1057 | If the variable @code{ctl-arrow} is @code{nil}, all control characters in |
| 1058 | the buffer are displayed with octal escape sequences, except for newline |
| 1059 | and tab. Altering the value of @code{ctl-arrow} makes it local to the |
| 1060 | current buffer; until that time, the default value is in effect. The |
| 1061 | default is initially @code{t}. @xref{Display Tables,, Display Tables, |
| 1062 | elisp, The Emacs Lisp Reference Manual}. |
| 1063 | |
| 1064 | @vindex tab-width |
| 1065 | @vindex default-tab-width |
| 1066 | Normally, a tab character in the buffer is displayed as whitespace which |
| 1067 | extends to the next display tab stop position, and display tab stops come |
| 1068 | at intervals equal to eight spaces. The number of spaces per tab is |
| 1069 | controlled by the variable @code{tab-width}, which is made local by |
| 1070 | changing it, just like @code{ctl-arrow}. Note that how the tab character |
| 1071 | in the buffer is displayed has nothing to do with the definition of |
| 1072 | @key{TAB} as a command. The variable @code{tab-width} must have an |
| 1073 | integer value between 1 and 1000, inclusive. The variable |
| 1074 | @code{default-tab-width} controls the default value of this variable |
| 1075 | for buffers where you have not set it locally. |
| 1076 | |
| 1077 | @cindex truncation |
| 1078 | @cindex line truncation, and fringes |
| 1079 | As an alternative to continuation, Emacs can display long lines by |
| 1080 | @dfn{truncation}. This means that all the characters that do not fit |
| 1081 | in the width of the screen or window do not appear at all. On |
| 1082 | graphical terminals, a small straight arrow in the fringe indicates |
| 1083 | truncation at either end of the line. On text terminals, @samp{$} |
| 1084 | appears in the first column when there is text truncated to the left, |
| 1085 | and in the last column when there is text truncated to the right. |
| 1086 | |
| 1087 | @vindex truncate-lines |
| 1088 | @findex toggle-truncate-lines |
| 1089 | Horizontal scrolling automatically causes line truncation |
| 1090 | (@pxref{Horizontal Scrolling}). You can explicitly enable line |
| 1091 | truncation for a particular buffer with the command @kbd{M-x |
| 1092 | toggle-truncate-lines}. This works by locally changing the variable |
| 1093 | @code{truncate-lines}. If that variable is non-@code{nil}, long lines |
| 1094 | are truncated; if it is @code{nil}, they are continued onto multiple |
| 1095 | screen lines. Setting the variable @code{truncate-lines} in any way |
| 1096 | makes it local to the current buffer; until that time, the default |
| 1097 | value is in effect. The default value is normally @code{nil}. |
| 1098 | |
| 1099 | @c @vindex truncate-partial-width-windows @c Idx entry is in Split Windows. |
| 1100 | If the variable @code{truncate-partial-width-windows} is |
| 1101 | non-@code{nil}, it forces truncation rather than continuation in any |
| 1102 | window less than the full width of the screen or frame, regardless of |
| 1103 | the value of @code{truncate-lines}. For information about side-by-side |
| 1104 | windows, see @ref{Split Window}. See also @ref{Display,, Display, |
| 1105 | elisp, The Emacs Lisp Reference Manual}. |
| 1106 | |
| 1107 | @vindex overflow-newline-into-fringe |
| 1108 | If the variable @code{overflow-newline-into-fringe} is |
| 1109 | non-@code{nil} on a window system, it specifies that lines which are |
| 1110 | exactly as wide as the window (not counting the final newline |
| 1111 | character) shall not be broken into two lines on the display (with |
| 1112 | just the newline on the second line). Instead, the newline |
| 1113 | overflows into the right fringe, and the cursor will be displayed in |
| 1114 | the fringe when positioned on that newline. |
| 1115 | |
| 1116 | @vindex indicate-buffer-boundaries |
| 1117 | On a window system, Emacs may indicate the buffer boundaries in the |
| 1118 | fringes. The buffer boundaries, i.e. first and last line in the |
| 1119 | buffer, can be marked with angle bitmaps in the left or right fringe. |
| 1120 | This can be combined with up and down arrow bitmaps shown at the top |
| 1121 | and bottom of the left or right fringe if the window can be scrolled |
| 1122 | in either direction. |
| 1123 | |
| 1124 | The buffer-local variable @code{indicate-buffer-boundaries} controls |
| 1125 | how the buffer boundaries and window scrolling is indicated in the |
| 1126 | fringes. |
| 1127 | |
| 1128 | If the value is @code{left} or @code{right}, both angle and arrow |
| 1129 | bitmaps are displayed in the left or right fringe, respectively. |
| 1130 | |
| 1131 | If value is an alist, each element @code{(@var{indicator} . |
| 1132 | @var{position})} specifies the position of one of the indicators. |
| 1133 | The @var{indicator} must be one of @code{top}, @code{bottom}, |
| 1134 | @code{up}, @code{down}, or @code{t} which specifies the default |
| 1135 | position for the indicators not present in the alist. |
| 1136 | The @var{position} is one of @code{left}, @code{right}, or @code{nil} |
| 1137 | which specifies not to show this indicator. |
| 1138 | |
| 1139 | For example, @code{((top . left) (t . right))} places the top angle |
| 1140 | bitmap in left fringe, the bottom angle bitmap in right fringe, and |
| 1141 | both arrow bitmaps in right fringe. To show just the angle bitmaps in |
| 1142 | the left fringe, but no arrow bitmaps, use @code{((top . left) |
| 1143 | (bottom . left))}. |
| 1144 | |
| 1145 | @vindex default-indicate-buffer-boundaries |
| 1146 | The value of the variable @code{default-indicate-buffer-boundaries} |
| 1147 | is the default value for @code{indicate-buffer-boundaries} in buffers |
| 1148 | that do not override it. |
| 1149 | |
| 1150 | @vindex baud-rate |
| 1151 | The variable @anchor{baud-rate}@code{baud-rate} holds the output speed of the |
| 1152 | terminal, as far as Emacs knows. Setting this variable does not |
| 1153 | change the speed of actual data transmission, but the value is used |
| 1154 | for calculations. On terminals, it affects padding, and decisions |
| 1155 | about whether to scroll part of the screen or redraw it instead. |
| 1156 | It also affects the behavior of incremental search. |
| 1157 | |
| 1158 | On window-systems, @code{baud-rate} is only used to determine how |
| 1159 | frequently to look for pending input during display updating. A |
| 1160 | higher value of @code{baud-rate} means that check for pending input |
| 1161 | will be done less frequently. |
| 1162 | |
| 1163 | You can customize the way any particular character code is displayed |
| 1164 | by means of a display table. @xref{Display Tables,, Display Tables, |
| 1165 | elisp, The Emacs Lisp Reference Manual}. |
| 1166 | |
| 1167 | @cindex hourglass pointer display |
| 1168 | @vindex hourglass-delay |
| 1169 | On a window system, Emacs can optionally display the mouse pointer |
| 1170 | in a special shape to say that Emacs is busy. To turn this feature on |
| 1171 | or off, customize the group @code{cursor}. You can also control the |
| 1172 | amount of time Emacs must remain busy before the busy indicator is |
| 1173 | displayed, by setting the variable @code{hourglass-delay}. |
| 1174 | |
| 1175 | @findex tty-suppress-bold-inverse-default-colors |
| 1176 | On some text-only terminals, bold face and inverse video together |
| 1177 | result in text that is hard to read. Call the function |
| 1178 | @code{tty-suppress-bold-inverse-default-colors} with a non-@code{nil} |
| 1179 | argument to suppress the effect of bold-face in this case. |
| 1180 | |
| 1181 | @ignore |
| 1182 | arch-tag: 2219f910-2ff0-4521-b059-1bd231a536c4 |
| 1183 | @end ignore |