| 1 | @c This is part of the Emacs manual. |
| 2 | @c Copyright (C) 1985-1987, 1993-1995, 1997, 2000-2014 Free Software |
| 3 | @c Foundation, Inc. |
| 4 | |
| 5 | @c See file emacs.texi for copying conditions. |
| 6 | @node Display |
| 7 | @chapter Controlling the Display |
| 8 | |
| 9 | Since only part of a large buffer fits in the window, Emacs has to |
| 10 | show only a part of it. This chapter describes commands and variables |
| 11 | that let you specify which part of the text you want to see, and how |
| 12 | the text is displayed. |
| 13 | |
| 14 | @menu |
| 15 | * Scrolling:: Commands to move text up and down in a window. |
| 16 | * Recentering:: A scroll command that centers the current line. |
| 17 | * Auto Scrolling:: Redisplay scrolls text automatically when needed. |
| 18 | * Horizontal Scrolling:: Moving text left and right in a window. |
| 19 | * Narrowing:: Restricting display and editing to a portion |
| 20 | of the buffer. |
| 21 | * View Mode:: Viewing read-only buffers. |
| 22 | * Follow Mode:: Follow mode lets two windows scroll as one. |
| 23 | * Faces:: How to change the display style using faces. |
| 24 | * Colors:: Specifying colors for faces. |
| 25 | * Standard Faces:: The main predefined faces. |
| 26 | * Text Scale:: Increasing or decreasing text size in a buffer. |
| 27 | * Font Lock:: Minor mode for syntactic highlighting using faces. |
| 28 | * Highlight Interactively:: Tell Emacs what text to highlight. |
| 29 | * Fringes:: Enabling or disabling window fringes. |
| 30 | * Displaying Boundaries:: Displaying top and bottom of the buffer. |
| 31 | * Useless Whitespace:: Showing possibly spurious trailing whitespace. |
| 32 | * Selective Display:: Hiding lines with lots of indentation. |
| 33 | * Optional Mode Line:: Optional mode line display features. |
| 34 | * Text Display:: How text characters are normally displayed. |
| 35 | * Cursor Display:: Features for displaying the cursor. |
| 36 | * Line Truncation:: Truncating lines to fit the screen width instead |
| 37 | of continuing them to multiple screen lines. |
| 38 | * Visual Line Mode:: Word wrap and screen line-based editing. |
| 39 | * Display Custom:: Information on variables for customizing display. |
| 40 | @end menu |
| 41 | |
| 42 | @node Scrolling |
| 43 | @section Scrolling |
| 44 | @cindex scrolling |
| 45 | |
| 46 | If a window is too small to display all the text in its buffer, it |
| 47 | displays only a portion of it. @dfn{Scrolling} commands change which |
| 48 | portion of the buffer is displayed. |
| 49 | |
| 50 | Scrolling ``forward'' or ``up'' advances the portion of the buffer |
| 51 | displayed in the window; equivalently, it moves the buffer text |
| 52 | upwards relative to the window. Scrolling ``backward'' or ``down'' |
| 53 | displays an earlier portion of the buffer, and moves the text |
| 54 | downwards relative to the window. |
| 55 | |
| 56 | In Emacs, scrolling ``up'' or ``down'' refers to the direction that |
| 57 | the text moves in the window, @emph{not} the direction that the window |
| 58 | moves relative to the text. This terminology was adopted by Emacs |
| 59 | before the modern meaning of ``scrolling up'' and ``scrolling down'' |
| 60 | became widespread. Hence, the strange result that @key{PageDown} |
| 61 | scrolls ``up'' in the Emacs sense. |
| 62 | |
| 63 | The portion of a buffer displayed in a window always contains point. |
| 64 | If you move point past the bottom or top of the window, scrolling |
| 65 | occurs automatically to bring it back onscreen (@pxref{Auto |
| 66 | Scrolling}). You can also scroll explicitly with these commands: |
| 67 | |
| 68 | @table @kbd |
| 69 | @item C-v |
| 70 | @itemx @key{next} |
| 71 | @itemx @key{PageDown} |
| 72 | Scroll forward by nearly a full window (@code{scroll-up-command}). |
| 73 | @item M-v |
| 74 | @itemx @key{prior} |
| 75 | @itemx @key{PageUp} |
| 76 | Scroll backward (@code{scroll-down-command}). |
| 77 | @end table |
| 78 | |
| 79 | @kindex C-v |
| 80 | @kindex M-v |
| 81 | @kindex next |
| 82 | @kindex prior |
| 83 | @kindex PageDown |
| 84 | @kindex PageUp |
| 85 | @findex scroll-up-command |
| 86 | @findex scroll-down-command |
| 87 | @kbd{C-v} (@code{scroll-up-command}) scrolls forward by nearly the |
| 88 | whole window height. The effect is to take the two lines at the |
| 89 | bottom of the window and put them at the top, followed by lines that |
| 90 | were not previously visible. If point was in the text that scrolled |
| 91 | off the top, it ends up on the window's new topmost line. The |
| 92 | @key{next} (or @key{PageDown}) key is equivalent to @kbd{C-v}. |
| 93 | |
| 94 | @kbd{M-v} (@code{scroll-down-command}) scrolls backward in a similar |
| 95 | way. The @key{prior} (or @key{PageUp}) key is equivalent to |
| 96 | @kbd{M-v}. |
| 97 | |
| 98 | @vindex next-screen-context-lines |
| 99 | The number of lines of overlap left by these scroll commands is |
| 100 | controlled by the variable @code{next-screen-context-lines}, whose |
| 101 | default value is 2. You can supply the commands with a numeric prefix |
| 102 | argument, @var{n}, to scroll by @var{n} lines; Emacs attempts to leave |
| 103 | point unchanged, so that the text and point move up or down together. |
| 104 | @kbd{C-v} with a negative argument is like @kbd{M-v} and vice versa. |
| 105 | |
| 106 | @vindex scroll-error-top-bottom |
| 107 | By default, these commands signal an error (by beeping or flashing |
| 108 | the screen) if no more scrolling is possible, because the window has |
| 109 | reached the beginning or end of the buffer. If you change the |
| 110 | variable @code{scroll-error-top-bottom} to @code{t}, the command moves |
| 111 | point to the farthest possible position. If point is already there, |
| 112 | the command signals an error. |
| 113 | |
| 114 | @vindex scroll-preserve-screen-position |
| 115 | @cindex @code{scroll-command} property |
| 116 | Some users like scroll commands to keep point at the same screen |
| 117 | position, so that scrolling back to the same screen conveniently |
| 118 | returns point to its original position. You can enable this behavior |
| 119 | via the variable @code{scroll-preserve-screen-position}. If the value |
| 120 | is @code{t}, Emacs adjusts point to keep the cursor at the same screen |
| 121 | position whenever a scroll command moves it off-window, rather than |
| 122 | moving it to the topmost or bottommost line. With any other |
| 123 | non-@code{nil} value, Emacs adjusts point this way even if the scroll |
| 124 | command leaves point in the window. This variable affects all the |
| 125 | scroll commands documented in this section, as well as scrolling with |
| 126 | the mouse wheel (@pxref{Mouse Commands}); in general, it affects any |
| 127 | command that has a non-@code{nil} @code{scroll-command} property. |
| 128 | @xref{Property Lists,,, elisp, The Emacs Lisp Reference Manual}. |
| 129 | |
| 130 | @vindex scroll-up |
| 131 | @vindex scroll-down |
| 132 | @findex scroll-up-line |
| 133 | @findex scroll-down-line |
| 134 | The commands @kbd{M-x scroll-up} and @kbd{M-x scroll-down} behave |
| 135 | similarly to @code{scroll-up-command} and @code{scroll-down-command}, |
| 136 | except they do not obey @code{scroll-error-top-bottom}. Prior to |
| 137 | Emacs 24, these were the default commands for scrolling up and down. |
| 138 | The commands @kbd{M-x scroll-up-line} and @kbd{M-x scroll-down-line} |
| 139 | scroll the current window by one line at a time. If you intend to use |
| 140 | any of these commands, you might want to give them key bindings |
| 141 | (@pxref{Init Rebinding}). |
| 142 | |
| 143 | @node Recentering |
| 144 | @section Recentering |
| 145 | |
| 146 | @table @kbd |
| 147 | @item C-l |
| 148 | Scroll the selected window so the current line is the center-most text |
| 149 | line; on subsequent consecutive invocations, make the current line the |
| 150 | top line, the bottom line, and so on in cyclic order. Possibly |
| 151 | redisplay the screen too (@code{recenter-top-bottom}). |
| 152 | |
| 153 | @item M-x recenter |
| 154 | Scroll the selected window so the current line is the center-most text |
| 155 | line. Possibly redisplay the screen too. |
| 156 | |
| 157 | @item C-M-l |
| 158 | Scroll heuristically to bring useful information onto the screen |
| 159 | (@code{reposition-window}). |
| 160 | @end table |
| 161 | |
| 162 | @kindex C-l |
| 163 | @findex recenter-top-bottom |
| 164 | The @kbd{C-l} (@code{recenter-top-bottom}) command @dfn{recenters} |
| 165 | the selected window, scrolling it so that the current screen line is |
| 166 | exactly in the center of the window, or as close to the center as |
| 167 | possible. |
| 168 | |
| 169 | Typing @kbd{C-l} twice in a row (@kbd{C-l C-l}) scrolls the window |
| 170 | so that point is on the topmost screen line. Typing a third @kbd{C-l} |
| 171 | scrolls the window so that point is on the bottom-most screen line. |
| 172 | Each successive @kbd{C-l} cycles through these three positions. |
| 173 | |
| 174 | @vindex recenter-positions |
| 175 | You can change the cycling order by customizing the list variable |
| 176 | @code{recenter-positions}. Each list element should be the symbol |
| 177 | @code{top}, @code{middle}, or @code{bottom}, or a number; an integer |
| 178 | means to move the line to the specified screen line, while a |
| 179 | floating-point number between 0.0 and 1.0 specifies a percentage of |
| 180 | the screen space from the top of the window. The default, |
| 181 | @code{(middle top bottom)}, is the cycling order described above. |
| 182 | Furthermore, if you change the variable @code{scroll-margin} to a |
| 183 | non-zero value @var{n}, @kbd{C-l} always leaves at least @var{n} |
| 184 | screen lines between point and the top or bottom of the window |
| 185 | (@pxref{Auto Scrolling}). |
| 186 | |
| 187 | You can also give @kbd{C-l} a prefix argument. A plain prefix |
| 188 | argument, @kbd{C-u C-l}, simply recenters point. A positive argument |
| 189 | @var{n} puts point @var{n} lines down from the top of the window. An |
| 190 | argument of zero puts point on the topmost line. A negative argument |
| 191 | @var{-n} puts point @var{n} lines from the bottom of the window. When |
| 192 | given an argument, @kbd{C-l} does not clear the screen or cycle |
| 193 | through different screen positions. |
| 194 | |
| 195 | @vindex recenter-redisplay |
| 196 | If the variable @code{recenter-redisplay} has a non-@code{nil} |
| 197 | value, each invocation of @kbd{C-l} also clears and redisplays the |
| 198 | screen; the special value @code{tty} (the default) says to do this on |
| 199 | text-terminal frames only. Redisplaying is useful in case the screen |
| 200 | becomes garbled for any reason (@pxref{Screen Garbled}). |
| 201 | |
| 202 | @findex recenter |
| 203 | The more primitive command @kbd{M-x recenter} behaves like |
| 204 | @code{recenter-top-bottom}, but does not cycle among screen positions. |
| 205 | |
| 206 | @kindex C-M-l |
| 207 | @findex reposition-window |
| 208 | @kbd{C-M-l} (@code{reposition-window}) scrolls the current window |
| 209 | heuristically in a way designed to get useful information onto the |
| 210 | screen. For example, in a Lisp file, this command tries to get the |
| 211 | entire current defun onto the screen if possible. |
| 212 | |
| 213 | @node Auto Scrolling |
| 214 | @section Automatic Scrolling |
| 215 | |
| 216 | @cindex automatic scrolling |
| 217 | Emacs performs @dfn{automatic scrolling} when point moves out of the |
| 218 | visible portion of the text. Normally, automatic scrolling centers |
| 219 | point vertically in the window, but there are several ways to alter |
| 220 | this behavior. |
| 221 | |
| 222 | @vindex scroll-conservatively |
| 223 | If you set @code{scroll-conservatively} to a small number @var{n}, |
| 224 | then moving point just a little off the screen (no more than @var{n} |
| 225 | lines) causes Emacs to scroll just enough to bring point back on |
| 226 | screen; if doing so fails to make point visible, Emacs scrolls just |
| 227 | far enough to center point in the window. If you set |
| 228 | @code{scroll-conservatively} to a large number (larger than 100), |
| 229 | automatic scrolling never centers point, no matter how far point |
| 230 | moves; Emacs always scrolls text just enough to bring point into view, |
| 231 | either at the top or bottom of the window depending on the scroll |
| 232 | direction. By default, @code{scroll-conservatively} is@tie{}0, which |
| 233 | means to always center point in the window. |
| 234 | |
| 235 | @vindex scroll-step |
| 236 | Another way to control automatic scrolling is to customize the |
| 237 | variable @code{scroll-step}. Its value determines the number of lines |
| 238 | by which to automatically scroll, when point moves off the screen. If |
| 239 | scrolling by that number of lines fails to bring point back into view, |
| 240 | point is centered instead. The default value is zero, which (by |
| 241 | default) causes point to always be centered after scrolling. |
| 242 | |
| 243 | @cindex aggressive scrolling |
| 244 | @vindex scroll-up-aggressively |
| 245 | @vindex scroll-down-aggressively |
| 246 | A third way to control automatic scrolling is to customize the |
| 247 | variables @code{scroll-up-aggressively} and |
| 248 | @code{scroll-down-aggressively}, which directly specify the vertical |
| 249 | position of point after scrolling. The value of |
| 250 | @code{scroll-up-aggressively} should be either @code{nil} (the |
| 251 | default), or a floating point number @var{f} between 0 and 1. The |
| 252 | latter means that when point goes below the bottom window edge (i.e., |
| 253 | scrolling forward), Emacs scrolls the window so that point is @var{f} |
| 254 | parts of the window height from the bottom window edge. Thus, larger |
| 255 | @var{f} means more aggressive scrolling: more new text is brought into |
| 256 | view. The default value, @code{nil}, is equivalent to 0.5. |
| 257 | |
| 258 | Likewise, @code{scroll-down-aggressively} is used when point goes |
| 259 | above the bottom window edge (i.e., scrolling backward). The value |
| 260 | specifies how far point should be from the top margin of the window |
| 261 | after scrolling. Thus, as with @code{scroll-up-aggressively}, a |
| 262 | larger value is more aggressive. |
| 263 | |
| 264 | Note that the variables @code{scroll-conservatively}, |
| 265 | @code{scroll-step}, and @code{scroll-up-aggressively} / |
| 266 | @code{scroll-down-aggressively} control automatic scrolling in |
| 267 | contradictory ways. Therefore, you should pick no more than one of |
| 268 | these methods to customize automatic scrolling. In case you customize |
| 269 | multiple variables, the order of priority is: |
| 270 | @code{scroll-conservatively}, then @code{scroll-step}, and finally |
| 271 | @code{scroll-up-aggressively} / @code{scroll-down-aggressively}. |
| 272 | |
| 273 | @vindex scroll-margin |
| 274 | The variable @code{scroll-margin} restricts how close point can come |
| 275 | to the top or bottom of a window (even if aggressive scrolling |
| 276 | specifies a fraction @var{f} that is larger than the window portion |
| 277 | between the top and the bottom margins). Its value is a number of screen |
| 278 | lines; if point comes within that many lines of the top or bottom of |
| 279 | the window, Emacs performs automatic scrolling. By default, |
| 280 | @code{scroll-margin} is 0. |
| 281 | |
| 282 | @node Horizontal Scrolling |
| 283 | @section Horizontal Scrolling |
| 284 | @cindex horizontal scrolling |
| 285 | |
| 286 | @vindex auto-hscroll-mode |
| 287 | @dfn{Horizontal scrolling} means shifting all the lines sideways |
| 288 | within a window, so that some of the text near the left margin is not |
| 289 | displayed. When the text in a window is scrolled horizontally, text |
| 290 | lines are truncated rather than continued (@pxref{Line Truncation}). |
| 291 | If a window shows truncated lines, Emacs performs automatic horizontal |
| 292 | scrolling whenever point moves off the left or right edge of the |
| 293 | screen. To disable automatic horizontal scrolling, set the variable |
| 294 | @code{auto-hscroll-mode} to @code{nil}. Note that when the automatic |
| 295 | horizontal scrolling is turned off, if point moves off the edge of the |
| 296 | screen, the cursor disappears to indicate that. (On text terminals, |
| 297 | the cursor is left at the edge instead.) |
| 298 | |
| 299 | @vindex hscroll-margin |
| 300 | The variable @code{hscroll-margin} controls how close point can get |
| 301 | to the window's left and right edges before automatic scrolling |
| 302 | occurs. It is measured in columns. For example, if the value is 5, |
| 303 | then moving point within 5 columns of an edge causes horizontal |
| 304 | scrolling away from that edge. |
| 305 | |
| 306 | @vindex hscroll-step |
| 307 | The variable @code{hscroll-step} determines how many columns to |
| 308 | scroll the window when point gets too close to the edge. Zero, the |
| 309 | default value, means to center point horizontally within the window. |
| 310 | A positive integer value specifies the number of columns to scroll by. |
| 311 | A floating-point number specifies the fraction of the window's width |
| 312 | to scroll by. |
| 313 | |
| 314 | You can also perform explicit horizontal scrolling with the |
| 315 | following commands: |
| 316 | |
| 317 | @table @kbd |
| 318 | @item C-x < |
| 319 | Scroll text in current window to the left (@code{scroll-left}). |
| 320 | @item C-x > |
| 321 | Scroll to the right (@code{scroll-right}). |
| 322 | @end table |
| 323 | |
| 324 | @kindex C-x < |
| 325 | @kindex C-x > |
| 326 | @findex scroll-left |
| 327 | @findex scroll-right |
| 328 | @kbd{C-x <} (@code{scroll-left}) scrolls text in the selected window |
| 329 | to the left by the full width of the window, less two columns. (In |
| 330 | other words, the text in the window moves left relative to the |
| 331 | window.) With a numeric argument @var{n}, it scrolls by @var{n} |
| 332 | columns. |
| 333 | |
| 334 | If the text is scrolled to the left, and point moves off the left |
| 335 | edge of the window, the cursor will freeze at the left edge of the |
| 336 | window, until point moves back to the displayed portion of the text. |
| 337 | This is independent of the current setting of |
| 338 | @code{auto-hscroll-mode}, which, for text scrolled to the left, only |
| 339 | affects the behavior at the right edge of the window. |
| 340 | |
| 341 | @kbd{C-x >} (@code{scroll-right}) scrolls similarly to the right. |
| 342 | The window cannot be scrolled any farther to the right once it is |
| 343 | displayed normally, with each line starting at the window's left |
| 344 | margin; attempting to do so has no effect. This means that you don't |
| 345 | have to calculate the argument precisely for @w{@kbd{C-x >}}; any |
| 346 | sufficiently large argument will restore the normal display. |
| 347 | |
| 348 | If you use those commands to scroll a window horizontally, that sets |
| 349 | a lower bound for automatic horizontal scrolling. Automatic scrolling |
| 350 | will continue to scroll the window, but never farther to the right |
| 351 | than the amount you previously set by @code{scroll-left}. |
| 352 | |
| 353 | @node Narrowing |
| 354 | @section Narrowing |
| 355 | @cindex widening |
| 356 | @cindex restriction |
| 357 | @cindex narrowing |
| 358 | @cindex accessible portion |
| 359 | |
| 360 | @dfn{Narrowing} means focusing in on some portion of the buffer, |
| 361 | making the rest temporarily inaccessible. The portion which you can |
| 362 | still get to is called the @dfn{accessible portion}. Canceling the |
| 363 | narrowing, which makes the entire buffer once again accessible, is |
| 364 | called @dfn{widening}. The bounds of narrowing in effect in a buffer |
| 365 | are called the buffer's @dfn{restriction}. |
| 366 | |
| 367 | Narrowing can make it easier to concentrate on a single subroutine or |
| 368 | paragraph by eliminating clutter. It can also be used to limit the |
| 369 | range of operation of a replace command or repeating keyboard macro. |
| 370 | |
| 371 | @table @kbd |
| 372 | @item C-x n n |
| 373 | Narrow down to between point and mark (@code{narrow-to-region}). |
| 374 | @item C-x n w |
| 375 | Widen to make the entire buffer accessible again (@code{widen}). |
| 376 | @item C-x n p |
| 377 | Narrow down to the current page (@code{narrow-to-page}). |
| 378 | @item C-x n d |
| 379 | Narrow down to the current defun (@code{narrow-to-defun}). |
| 380 | @end table |
| 381 | |
| 382 | When you have narrowed down to a part of the buffer, that part appears |
| 383 | to be all there is. You can't see the rest, you can't move into it |
| 384 | (motion commands won't go outside the accessible part), you can't change |
| 385 | it in any way. However, it is not gone, and if you save the file all |
| 386 | the inaccessible text will be saved. The word @samp{Narrow} appears in |
| 387 | the mode line whenever narrowing is in effect. |
| 388 | |
| 389 | @kindex C-x n n |
| 390 | @findex narrow-to-region |
| 391 | The primary narrowing command is @kbd{C-x n n} (@code{narrow-to-region}). |
| 392 | It sets the current buffer's restrictions so that the text in the current |
| 393 | region remains accessible, but all text before the region or after the |
| 394 | region is inaccessible. Point and mark do not change. |
| 395 | |
| 396 | @kindex C-x n p |
| 397 | @findex narrow-to-page |
| 398 | @kindex C-x n d |
| 399 | @findex narrow-to-defun |
| 400 | Alternatively, use @kbd{C-x n p} (@code{narrow-to-page}) to narrow |
| 401 | down to the current page. @xref{Pages}, for the definition of a page. |
| 402 | @kbd{C-x n d} (@code{narrow-to-defun}) narrows down to the defun |
| 403 | containing point (@pxref{Defuns}). |
| 404 | |
| 405 | @kindex C-x n w |
| 406 | @findex widen |
| 407 | The way to cancel narrowing is to widen with @kbd{C-x n w} |
| 408 | (@code{widen}). This makes all text in the buffer accessible again. |
| 409 | |
| 410 | You can get information on what part of the buffer you are narrowed down |
| 411 | to using the @kbd{C-x =} command. @xref{Position Info}. |
| 412 | |
| 413 | Because narrowing can easily confuse users who do not understand it, |
| 414 | @code{narrow-to-region} is normally a disabled command. Attempting to use |
| 415 | this command asks for confirmation and gives you the option of enabling it; |
| 416 | if you enable the command, confirmation will no longer be required for |
| 417 | it. @xref{Disabling}. |
| 418 | |
| 419 | @node View Mode |
| 420 | @section View Mode |
| 421 | @cindex View mode |
| 422 | @cindex mode, View |
| 423 | |
| 424 | @kindex s @r{(View mode)} |
| 425 | @kindex SPC @r{(View mode)} |
| 426 | @kindex DEL @r{(View mode)} |
| 427 | View mode is a minor mode that lets you scan a buffer by sequential |
| 428 | screenfuls. It provides commands for scrolling through the buffer |
| 429 | conveniently but not for changing it. Apart from the usual Emacs |
| 430 | cursor motion commands, you can type @key{SPC} to scroll forward one |
| 431 | windowful, @key{S-SPC} or @key{DEL} to scroll backward, and @kbd{s} to |
| 432 | start an incremental search. |
| 433 | |
| 434 | @kindex q @r{(View mode)} |
| 435 | @kindex e @r{(View mode)} |
| 436 | @findex View-quit |
| 437 | @findex View-exit |
| 438 | Typing @kbd{q} (@code{View-quit}) disables View mode, and switches |
| 439 | back to the buffer and position before View mode was enabled. Typing |
| 440 | @kbd{e} (@code{View-exit}) disables View mode, keeping the current |
| 441 | buffer and position. |
| 442 | |
| 443 | @findex view-buffer |
| 444 | @findex view-file |
| 445 | @kbd{M-x view-buffer} prompts for an existing Emacs buffer, switches |
| 446 | to it, and enables View mode. @kbd{M-x view-file} prompts for a file |
| 447 | and visits it with View mode enabled. |
| 448 | |
| 449 | @node Follow Mode |
| 450 | @section Follow Mode |
| 451 | @cindex Follow mode |
| 452 | @cindex mode, Follow |
| 453 | @findex follow-mode |
| 454 | @cindex windows, synchronizing |
| 455 | @cindex synchronizing windows |
| 456 | |
| 457 | @dfn{Follow mode} is a minor mode that makes two windows, both |
| 458 | showing the same buffer, scroll as a single tall ``virtual window''. |
| 459 | To use Follow mode, go to a frame with just one window, split it into |
| 460 | two side-by-side windows using @kbd{C-x 3}, and then type @kbd{M-x |
| 461 | follow-mode}. From then on, you can edit the buffer in either of the |
| 462 | two windows, or scroll either one; the other window follows it. |
| 463 | |
| 464 | In Follow mode, if you move point outside the portion visible in one |
| 465 | window and into the portion visible in the other window, that selects |
| 466 | the other window---again, treating the two as if they were parts of |
| 467 | one large window. |
| 468 | |
| 469 | To turn off Follow mode, type @kbd{M-x follow-mode} a second time. |
| 470 | |
| 471 | @node Faces |
| 472 | @section Text Faces |
| 473 | @cindex faces |
| 474 | |
| 475 | Emacs can display text in several different styles, called |
| 476 | @dfn{faces}. Each face can specify various @dfn{face attributes}, |
| 477 | such as the font, height, weight, slant, foreground and background |
| 478 | color, and underlining or overlining. Most major modes assign faces |
| 479 | to the text automatically, via Font Lock mode. @xref{Font Lock}, for |
| 480 | more information about how these faces are assigned. |
| 481 | |
| 482 | @findex list-faces-display |
| 483 | To see what faces are currently defined, and what they look like, |
| 484 | type @kbd{M-x list-faces-display}. With a prefix argument, this |
| 485 | prompts for a regular expression, and displays only faces with names |
| 486 | matching that regular expression (@pxref{Regexps}). |
| 487 | |
| 488 | @vindex frame-background-mode |
| 489 | It's possible for a given face to look different in different |
| 490 | frames. For instance, some text terminals do not support all face |
| 491 | attributes, particularly font, height, and width, and some support a |
| 492 | limited range of colors. In addition, most Emacs faces are defined so |
| 493 | that their attributes are different on light and dark frame |
| 494 | backgrounds, for reasons of legibility. By default, Emacs |
| 495 | automatically chooses which set of face attributes to display on each |
| 496 | frame, based on the frame's current background color. However, you |
| 497 | can override this by giving the variable @code{frame-background-mode} |
| 498 | a non-@code{nil} value. A value of @code{dark} makes Emacs treat all |
| 499 | frames as if they have a dark background, whereas a value of |
| 500 | @code{light} makes it treat all frames as if they have a light |
| 501 | background. |
| 502 | |
| 503 | @cindex background color |
| 504 | @cindex default face |
| 505 | You can customize a face to alter its attributes, and save those |
| 506 | customizations for future Emacs sessions. @xref{Face Customization}, |
| 507 | for details. |
| 508 | |
| 509 | The @code{default} face is the default for displaying text, and all |
| 510 | of its attributes are specified. Its background color is also used as |
| 511 | the frame's background color. @xref{Colors}. |
| 512 | |
| 513 | @cindex cursor face |
| 514 | Another special face is the @code{cursor} face. On graphical |
| 515 | displays, the background color of this face is used to draw the text |
| 516 | cursor. None of the other attributes of this face have any effect; |
| 517 | the foreground color for text under the cursor is taken from the |
| 518 | background color of the underlying text. On text terminals, the |
| 519 | appearance of the text cursor is determined by the terminal, not by |
| 520 | the @code{cursor} face. |
| 521 | |
| 522 | You can also use X resources to specify attributes of any particular |
| 523 | face. @xref{Resources}. |
| 524 | |
| 525 | Emacs can display variable-width fonts, but some Emacs commands, |
| 526 | particularly indentation commands, do not account for variable |
| 527 | character display widths. Therefore, we recommend not using |
| 528 | variable-width fonts for most faces, particularly those assigned by |
| 529 | Font Lock mode. |
| 530 | |
| 531 | @node Colors |
| 532 | @section Colors for Faces |
| 533 | @cindex color name |
| 534 | @cindex RGB triplet |
| 535 | |
| 536 | Faces can have various foreground and background colors. When you |
| 537 | specify a color for a face---for instance, when customizing the face |
| 538 | (@pxref{Face Customization})---you can use either a @dfn{color name} |
| 539 | or an @dfn{RGB triplet}. |
| 540 | |
| 541 | @findex list-colors-display |
| 542 | @vindex list-colors-sort |
| 543 | A color name is a pre-defined name, such as @samp{dark orange} or |
| 544 | @samp{medium sea green}. To view a list of color names, type @kbd{M-x |
| 545 | list-colors-display}. To control the order in which colors are shown, |
| 546 | customize @code{list-colors-sort}. If you run this command on a |
| 547 | graphical display, it shows the full range of color names known to |
| 548 | Emacs (these are the standard X11 color names, defined in X's |
| 549 | @file{rgb.txt} file). If you run the command on a text terminal, it |
| 550 | shows only a small subset of colors that can be safely displayed on |
| 551 | such terminals. However, Emacs understands X11 color names even on |
| 552 | text terminals; if a face is given a color specified by an X11 color |
| 553 | name, it is displayed using the closest-matching terminal color. |
| 554 | |
| 555 | An RGB triplet is a string of the form @samp{#RRGGBB}. Each of the |
| 556 | R, G, and B components is a hexadecimal number specifying the |
| 557 | component's relative intensity, one to four digits long (usually two |
| 558 | digits are used). The components must have the same number of digits. |
| 559 | For hexadecimal values A to F, either upper or lower case are |
| 560 | acceptable. |
| 561 | |
| 562 | The @kbd{M-x list-colors-display} command also shows the equivalent |
| 563 | RGB triplet for each named color. For instance, @samp{medium sea |
| 564 | green} is equivalent to @samp{#3CB371}. |
| 565 | |
| 566 | @cindex face colors, setting |
| 567 | @findex set-face-foreground |
| 568 | @findex set-face-background |
| 569 | You can change the foreground and background colors of a face with |
| 570 | @kbd{M-x set-face-foreground} and @kbd{M-x set-face-background}. |
| 571 | These commands prompt in the minibuffer for a face name and a color, |
| 572 | with completion, and then set that face to use the specified color. |
| 573 | They affect the face colors on all frames, but their effects do not |
| 574 | persist for future Emacs sessions, unlike using the customization |
| 575 | buffer or X resources. You can also use frame parameters to set |
| 576 | foreground and background colors for a specific frame; @xref{Frame |
| 577 | Parameters}. |
| 578 | |
| 579 | @node Standard Faces |
| 580 | @section Standard Faces |
| 581 | |
| 582 | Here are the standard faces for specifying text appearance. You can |
| 583 | apply them to specific text when you want the effects they produce. |
| 584 | |
| 585 | @table @code |
| 586 | @item default |
| 587 | This face is used for ordinary text that doesn't specify any face. |
| 588 | Its background color is used as the frame's background color. |
| 589 | @item bold |
| 590 | This face uses a bold variant of the default font. |
| 591 | @item italic |
| 592 | This face uses an italic variant of the default font. |
| 593 | @item bold-italic |
| 594 | This face uses a bold italic variant of the default font. |
| 595 | @item underline |
| 596 | This face underlines text. |
| 597 | @item fixed-pitch |
| 598 | This face forces use of a fixed-width font. It's reasonable to |
| 599 | customize this face to use a different fixed-width font, if you like, |
| 600 | but you should not make it a variable-width font. |
| 601 | @item variable-pitch |
| 602 | This face forces use of a variable-width font. |
| 603 | @item shadow |
| 604 | This face is used for making the text less noticeable than the surrounding |
| 605 | ordinary text. Usually this can be achieved by using shades of gray in |
| 606 | contrast with either black or white default foreground color. |
| 607 | @end table |
| 608 | |
| 609 | Here's an incomplete list of faces used to highlight parts of the |
| 610 | text temporarily for specific purposes. (Many other modes define |
| 611 | their own faces for this purpose.) |
| 612 | |
| 613 | @table @code |
| 614 | @item highlight |
| 615 | This face is used for text highlighting in various contexts, such as |
| 616 | when the mouse cursor is moved over a hyperlink. |
| 617 | @item isearch |
| 618 | This face is used to highlight the current Isearch match |
| 619 | (@pxref{Incremental Search}). |
| 620 | @item query-replace |
| 621 | This face is used to highlight the current Query Replace match |
| 622 | (@pxref{Replace}). |
| 623 | @item lazy-highlight |
| 624 | This face is used to highlight ``lazy matches'' for Isearch and Query |
| 625 | Replace (matches other than the current one). |
| 626 | @item region |
| 627 | This face is used for displaying an active region (@pxref{Mark}). |
| 628 | When Emacs is built with GTK support, its colors are taken from the |
| 629 | current GTK theme. |
| 630 | @item secondary-selection |
| 631 | This face is used for displaying a secondary X selection (@pxref{Secondary |
| 632 | Selection}). |
| 633 | @item trailing-whitespace |
| 634 | The face for highlighting excess spaces and tabs at the end of a line |
| 635 | when @code{show-trailing-whitespace} is non-@code{nil} (@pxref{Useless |
| 636 | Whitespace}). |
| 637 | @item escape-glyph |
| 638 | The face for displaying control characters and escape sequences |
| 639 | (@pxref{Text Display}). |
| 640 | @item nobreak-space |
| 641 | The face for displaying ``no-break'' space characters (@pxref{Text |
| 642 | Display}). |
| 643 | @end table |
| 644 | |
| 645 | The following faces control the appearance of parts of the Emacs |
| 646 | frame: |
| 647 | |
| 648 | @table @code |
| 649 | @item mode-line |
| 650 | This face is used for the mode line of the currently selected window, |
| 651 | and for menu bars when toolkit menus are not used. By default, it's |
| 652 | drawn with shadows for a ``raised'' effect on graphical displays, and |
| 653 | drawn as the inverse of the default face on non-windowed terminals. |
| 654 | @item mode-line-inactive |
| 655 | Like @code{mode-line}, but used for mode lines of the windows other |
| 656 | than the selected one (if @code{mode-line-in-non-selected-windows} is |
| 657 | non-@code{nil}). This face inherits from @code{mode-line}, so changes |
| 658 | in that face affect mode lines in all windows. |
| 659 | @item mode-line-highlight |
| 660 | Like @code{highlight}, but used for portions of text on mode lines. |
| 661 | @item mode-line-buffer-id |
| 662 | This face is used for buffer identification parts in the mode line. |
| 663 | @item header-line |
| 664 | Similar to @code{mode-line} for a window's header line, which appears |
| 665 | at the top of a window just as the mode line appears at the bottom. |
| 666 | Most windows do not have a header line---only some special modes, such |
| 667 | Info mode, create one. |
| 668 | @item vertical-border |
| 669 | This face is used for the vertical divider between windows on text |
| 670 | terminals. |
| 671 | @item minibuffer-prompt |
| 672 | @cindex @code{minibuffer-prompt} face |
| 673 | @vindex minibuffer-prompt-properties |
| 674 | This face is used for the prompt strings displayed in the minibuffer. |
| 675 | By default, Emacs automatically adds this face to the value of |
| 676 | @code{minibuffer-prompt-properties}, which is a list of text |
| 677 | properties used to display the prompt text. (This variable takes |
| 678 | effect when you enter the minibuffer.) |
| 679 | @item fringe |
| 680 | @cindex @code{fringe} face |
| 681 | The face for the fringes to the left and right of windows on graphic |
| 682 | displays. (The fringes are the narrow portions of the Emacs frame |
| 683 | between the text area and the window's right and left borders.) |
| 684 | @xref{Fringes}. |
| 685 | @item cursor |
| 686 | The @code{:background} attribute of this face specifies the color of |
| 687 | the text cursor. @xref{Cursor Display}. |
| 688 | @item tooltip |
| 689 | This face is used for tooltip text. By default, if Emacs is built |
| 690 | with GTK support, tooltips are drawn via GTK and this face has no |
| 691 | effect. @xref{Tooltips}. |
| 692 | @item mouse |
| 693 | This face determines the color of the mouse pointer. |
| 694 | @end table |
| 695 | |
| 696 | The following faces likewise control the appearance of parts of the |
| 697 | Emacs frame, but only on text terminals, or when Emacs is built on X |
| 698 | with no toolkit support. (For all other cases, the appearance of the |
| 699 | respective frame elements is determined by system-wide settings.) |
| 700 | |
| 701 | @table @code |
| 702 | @item scroll-bar |
| 703 | This face determines the visual appearance of the scroll bar. |
| 704 | @xref{Scroll Bars}. |
| 705 | @item tool-bar |
| 706 | This face determines the color of tool bar icons. @xref{Tool Bars}. |
| 707 | @item menu |
| 708 | @cindex menu bar appearance |
| 709 | @cindex @code{menu} face, no effect if customized |
| 710 | @cindex customization of @code{menu} face |
| 711 | This face determines the colors and font of Emacs's menus. @xref{Menu |
| 712 | Bars}. |
| 713 | @item tty-menu-enabled-face |
| 714 | @cindex faces for text-mode menus |
| 715 | @cindex TTY menu faces |
| 716 | This face is used to display enabled menu items on text-mode |
| 717 | terminals. |
| 718 | @item tty-menu-disabled-face |
| 719 | This face is used to display disabled menu items on text-mode |
| 720 | terminals. |
| 721 | @item tty-menu-selected-face |
| 722 | This face is used to display on text-mode terminals the menu item that |
| 723 | would be selected if you click a mouse or press @key{RET}. |
| 724 | @end table |
| 725 | |
| 726 | @node Text Scale |
| 727 | @section Text Scale |
| 728 | |
| 729 | @cindex adjust buffer face height |
| 730 | @findex text-scale-adjust |
| 731 | @kindex C-x C-+ |
| 732 | @kindex C-x C-- |
| 733 | @kindex C-x C-= |
| 734 | @kindex C-x C-0 |
| 735 | To increase the height of the default face in the current buffer, |
| 736 | type @kbd{C-x C-+} or @kbd{C-x C-=}. To decrease it, type @kbd{C-x |
| 737 | C--}. To restore the default (global) face height, type @kbd{C-x |
| 738 | C-0}. These keys are all bound to the same command, |
| 739 | @code{text-scale-adjust}, which looks at the last key typed to |
| 740 | determine which action to take. |
| 741 | |
| 742 | The final key of these commands may be repeated without the leading |
| 743 | @kbd{C-x}. For instance, @kbd{C-x C-= C-= C-=} increases the face |
| 744 | height by three steps. Each step scales the text height by a factor |
| 745 | of 1.2; to change this factor, customize the variable |
| 746 | @code{text-scale-mode-step}. A numeric argument of 0 |
| 747 | to the @code{text-scale-adjust} command restores the default height, |
| 748 | the same as typing @kbd{C-x C-0}. |
| 749 | |
| 750 | @cindex increase buffer face height |
| 751 | @findex text-scale-increase |
| 752 | @cindex decrease buffer face height |
| 753 | @findex text-scale-decrease |
| 754 | The commands @code{text-scale-increase} and |
| 755 | @code{text-scale-decrease} increase or decrease the height of the |
| 756 | default face, just like @kbd{C-x C-+} and @kbd{C-x C--} respectively. |
| 757 | You may find it convenient to bind to these commands, rather than |
| 758 | @code{text-scale-adjust}. |
| 759 | |
| 760 | @cindex set buffer face height |
| 761 | @findex text-scale-set |
| 762 | The command @code{text-scale-set} scales the height of the default |
| 763 | face in the current buffer to an absolute level specified by its |
| 764 | prefix argument. |
| 765 | |
| 766 | @findex text-scale-mode |
| 767 | The above commands automatically enable the minor mode |
| 768 | @code{text-scale-mode} if the current font scaling is other than 1, |
| 769 | and disable it otherwise. |
| 770 | |
| 771 | @node Font Lock |
| 772 | @section Font Lock mode |
| 773 | @cindex Font Lock mode |
| 774 | @cindex mode, Font Lock |
| 775 | @cindex syntax highlighting and coloring |
| 776 | |
| 777 | Font Lock mode is a minor mode, always local to a particular buffer, |
| 778 | which assigns faces to (or @dfn{fontifies}) the text in the buffer. |
| 779 | Each buffer's major mode tells Font Lock mode which text to fontify; |
| 780 | for instance, programming language modes fontify syntactically |
| 781 | relevant constructs like comments, strings, and function names. |
| 782 | |
| 783 | @findex font-lock-mode |
| 784 | Font Lock mode is enabled by default. To toggle it in the current |
| 785 | buffer, type @kbd{M-x font-lock-mode}. A positive numeric argument |
| 786 | unconditionally enables Font Lock mode, and a negative or zero |
| 787 | argument disables it. |
| 788 | |
| 789 | @findex global-font-lock-mode |
| 790 | @vindex global-font-lock-mode |
| 791 | Type @kbd{M-x global-font-lock-mode} to toggle Font Lock mode in all |
| 792 | buffers. To impose this setting for future Emacs sessions, customize |
| 793 | the variable @code{global-font-lock-mode} (@pxref{Easy |
| 794 | Customization}), or add the following line to your init file: |
| 795 | |
| 796 | @example |
| 797 | (global-font-lock-mode 0) |
| 798 | @end example |
| 799 | |
| 800 | @noindent |
| 801 | If you have disabled Global Font Lock mode, you can still enable Font |
| 802 | Lock for specific major modes by adding the function |
| 803 | @code{font-lock-mode} to the mode hooks (@pxref{Hooks}). For example, |
| 804 | to enable Font Lock mode for editing C files, you can do this: |
| 805 | |
| 806 | @example |
| 807 | (add-hook 'c-mode-hook 'font-lock-mode) |
| 808 | @end example |
| 809 | |
| 810 | Font Lock mode uses several specifically named faces to do its job, |
| 811 | including @code{font-lock-string-face}, @code{font-lock-comment-face}, |
| 812 | and others. The easiest way to find them all is to use @kbd{M-x |
| 813 | customize-group @key{RET} font-lock-faces @key{RET}}. You can then |
| 814 | use that customization buffer to customize the appearance of these |
| 815 | faces. @xref{Face Customization}. |
| 816 | |
| 817 | @vindex font-lock-maximum-decoration |
| 818 | You can customize the variable @code{font-lock-maximum-decoration} |
| 819 | to alter the amount of fontification applied by Font Lock mode, for |
| 820 | major modes that support this feature. The value should be a number |
| 821 | (with 1 representing a minimal amount of fontification; some modes |
| 822 | support levels as high as 3); or @code{t}, meaning ``as high as |
| 823 | possible'' (the default). You can also specify different numbers for |
| 824 | particular major modes; for example, to use level 1 for C/C++ modes, |
| 825 | and the default level otherwise, use the value |
| 826 | |
| 827 | @example |
| 828 | '((c-mode . 1) (c++-mode . 1))) |
| 829 | @end example |
| 830 | |
| 831 | @vindex font-lock-beginning-of-syntax-function |
| 832 | @cindex incorrect fontification |
| 833 | @cindex parenthesis in column zero and fontification |
| 834 | @cindex brace in column zero and fontification |
| 835 | Comment and string fontification (or ``syntactic'' fontification) |
| 836 | relies on analysis of the syntactic structure of the buffer text. For |
| 837 | the sake of speed, some modes, including Lisp mode, rely on a special |
| 838 | convention: an open-parenthesis or open-brace in the leftmost column |
| 839 | always defines the beginning of a defun, and is thus always outside |
| 840 | any string or comment. Therefore, you should avoid placing an |
| 841 | open-parenthesis or open-brace in the leftmost column, if it is inside |
| 842 | a string or comment. @xref{Left Margin Paren}, for details. |
| 843 | |
| 844 | @cindex slow display during scrolling |
| 845 | The variable @code{font-lock-beginning-of-syntax-function}, which is |
| 846 | always buffer-local, specifies how Font Lock mode can find a position |
| 847 | guaranteed to be outside any comment or string. In modes which use |
| 848 | the leftmost column parenthesis convention, the default value of the |
| 849 | variable is @code{beginning-of-defun}---that tells Font Lock mode to |
| 850 | use the convention. If you set this variable to @code{nil}, Font Lock |
| 851 | no longer relies on the convention. This avoids incorrect results, |
| 852 | but the price is that, in some cases, fontification for a changed text |
| 853 | must rescan buffer text from the beginning of the buffer. This can |
| 854 | considerably slow down redisplay while scrolling, particularly if you |
| 855 | are close to the end of a large buffer. |
| 856 | |
| 857 | @findex font-lock-add-keywords |
| 858 | Font Lock highlighting patterns already exist for most modes, but |
| 859 | you may want to fontify additional patterns. You can use the function |
| 860 | @code{font-lock-add-keywords}, to add your own highlighting patterns |
| 861 | for a particular mode. For example, to highlight @samp{FIXME:} words |
| 862 | in C comments, use this: |
| 863 | |
| 864 | @example |
| 865 | (add-hook 'c-mode-hook |
| 866 | (lambda () |
| 867 | (font-lock-add-keywords nil |
| 868 | '(("\\<\\(FIXME\\):" 1 |
| 869 | font-lock-warning-face t))))) |
| 870 | @end example |
| 871 | |
| 872 | @findex font-lock-remove-keywords |
| 873 | @noindent |
| 874 | To remove keywords from the font-lock highlighting patterns, use the |
| 875 | function @code{font-lock-remove-keywords}. @xref{Search-based |
| 876 | Fontification,,, elisp, The Emacs Lisp Reference Manual}. |
| 877 | |
| 878 | @cindex just-in-time (JIT) font-lock |
| 879 | @cindex background syntax highlighting |
| 880 | Fontifying large buffers can take a long time. To avoid large |
| 881 | delays when a file is visited, Emacs initially fontifies only the |
| 882 | visible portion of a buffer. As you scroll through the buffer, each |
| 883 | portion that becomes visible is fontified as soon as it is displayed; |
| 884 | this type of Font Lock is called @dfn{Just-In-Time} (or @dfn{JIT}) |
| 885 | Lock. You can control how JIT Lock behaves, including telling it to |
| 886 | perform fontification while idle, by customizing variables in the |
| 887 | customization group @samp{jit-lock}. @xref{Specific Customization}. |
| 888 | |
| 889 | @node Highlight Interactively |
| 890 | @section Interactive Highlighting |
| 891 | @cindex highlighting by matching |
| 892 | @cindex interactive highlighting |
| 893 | @cindex Highlight Changes mode |
| 894 | |
| 895 | @findex highlight-changes-mode |
| 896 | Highlight Changes mode is a minor mode that @dfn{highlights} the parts |
| 897 | of the buffer that were changed most recently, by giving that text a |
| 898 | different face. To enable or disable Highlight Changes mode, use |
| 899 | @kbd{M-x highlight-changes-mode}. |
| 900 | |
| 901 | @cindex Hi Lock mode |
| 902 | @findex hi-lock-mode |
| 903 | Hi Lock mode is a minor mode that highlights text that matches |
| 904 | regular expressions you specify. For example, you can use it to |
| 905 | highlight all the references to a certain variable in a program source |
| 906 | file, highlight certain parts in a voluminous output of some program, |
| 907 | or highlight certain names in an article. To enable or disable Hi |
| 908 | Lock mode, use the command @kbd{M-x hi-lock-mode}. To enable Hi Lock |
| 909 | mode for all buffers, use @kbd{M-x global-hi-lock-mode} or place |
| 910 | @code{(global-hi-lock-mode 1)} in your @file{.emacs} file. |
| 911 | |
| 912 | Hi Lock mode works like Font Lock mode (@pxref{Font Lock}), except |
| 913 | that you specify explicitly the regular expressions to highlight. You |
| 914 | control them with these commands: |
| 915 | |
| 916 | @table @kbd |
| 917 | @item M-s h r @var{regexp} @key{RET} @var{face} @key{RET} |
| 918 | @itemx C-x w h @var{regexp} @key{RET} @var{face} @key{RET} |
| 919 | @kindex M-s h r |
| 920 | @kindex C-x w h |
| 921 | @findex highlight-regexp |
| 922 | Highlight text that matches @var{regexp} using face @var{face} |
| 923 | (@code{highlight-regexp}). The highlighting will remain as long as |
| 924 | the buffer is loaded. For example, to highlight all occurrences of |
| 925 | the word ``whim'' using the default face (a yellow background) |
| 926 | @kbd{M-s h r whim @key{RET} @key{RET}}. Any face can be used for |
| 927 | highlighting, Hi Lock provides several of its own and these are |
| 928 | pre-loaded into a list of default values. While being prompted |
| 929 | for a face use @kbd{M-n} and @kbd{M-p} to cycle through them. |
| 930 | |
| 931 | You can use this command multiple times, specifying various regular |
| 932 | expressions to highlight in different ways. |
| 933 | |
| 934 | @item M-s h u @var{regexp} @key{RET} |
| 935 | @itemx C-x w r @var{regexp} @key{RET} |
| 936 | @kindex M-s h u |
| 937 | @kindex C-x w r |
| 938 | @findex unhighlight-regexp |
| 939 | Unhighlight @var{regexp} (@code{unhighlight-regexp}). |
| 940 | |
| 941 | If you invoke this from the menu, you select the expression to |
| 942 | unhighlight from a list. If you invoke this from the keyboard, you |
| 943 | use the minibuffer. It will show the most recently added regular |
| 944 | expression; use @kbd{M-n} to show the next older expression and |
| 945 | @kbd{M-p} to select the next newer expression. (You can also type the |
| 946 | expression by hand, with completion.) When the expression you want to |
| 947 | unhighlight appears in the minibuffer, press @kbd{@key{RET}} to exit |
| 948 | the minibuffer and unhighlight it. |
| 949 | |
| 950 | @item M-s h l @var{regexp} @key{RET} @var{face} @key{RET} |
| 951 | @itemx C-x w l @var{regexp} @key{RET} @var{face} @key{RET} |
| 952 | @kindex M-s h l |
| 953 | @kindex C-x w l |
| 954 | @findex highlight-lines-matching-regexp |
| 955 | @cindex lines, highlighting |
| 956 | @cindex highlighting lines of text |
| 957 | Highlight entire lines containing a match for @var{regexp}, using face |
| 958 | @var{face} (@code{highlight-lines-matching-regexp}). |
| 959 | |
| 960 | @item M-s h p @var{phrase} @key{RET} @var{face} @key{RET} |
| 961 | @itemx C-x w p @var{phrase} @key{RET} @var{face} @key{RET} |
| 962 | @kindex M-s h p |
| 963 | @kindex C-x w p |
| 964 | @findex highlight-phrase |
| 965 | @cindex phrase, highlighting |
| 966 | @cindex highlighting phrase |
| 967 | Highlight matches of @var{phrase}, using face @var{face} |
| 968 | (@code{highlight-phrase}). @var{phrase} can be any regexp, |
| 969 | but spaces will be replaced by matches to whitespace and |
| 970 | initial lower-case letters will become case insensitive. |
| 971 | |
| 972 | @item M-s h . |
| 973 | @itemx C-x w . |
| 974 | @kindex M-s h . |
| 975 | @kindex C-x w . |
| 976 | @findex highlight-symbol-at-point |
| 977 | @cindex symbol, highlighting |
| 978 | @cindex highlighting symbol at point |
| 979 | Highlight the symbol found near point without prompting, using the next |
| 980 | available face automatically (@code{highlight-symbol-at-point}). |
| 981 | |
| 982 | @item M-s h w |
| 983 | @itemx C-x w b |
| 984 | @kindex M-s h w |
| 985 | @kindex C-x w b |
| 986 | @findex hi-lock-write-interactive-patterns |
| 987 | Insert all the current highlighting regexp/face pairs into the buffer |
| 988 | at point, with comment delimiters to prevent them from changing your |
| 989 | program. (This key binding runs the |
| 990 | @code{hi-lock-write-interactive-patterns} command.) |
| 991 | |
| 992 | These patterns are extracted from the comments, if appropriate, if you |
| 993 | invoke @kbd{M-x hi-lock-find-patterns}, or if you visit the file while |
| 994 | Hi Lock mode is enabled (since that runs @code{hi-lock-find-patterns}). |
| 995 | |
| 996 | @item M-s h f |
| 997 | @itemx C-x w i |
| 998 | @kindex M-s h f |
| 999 | @kindex C-x w i |
| 1000 | @findex hi-lock-find-patterns |
| 1001 | Extract regexp/face pairs from comments in the current buffer |
| 1002 | (@code{hi-lock-find-patterns}). Thus, you can enter patterns |
| 1003 | interactively with @code{highlight-regexp}, store them into the file |
| 1004 | with @code{hi-lock-write-interactive-patterns}, edit them (perhaps |
| 1005 | including different faces for different parenthesized parts of the |
| 1006 | match), and finally use this command (@code{hi-lock-find-patterns}) to |
| 1007 | have Hi Lock highlight the edited patterns. |
| 1008 | |
| 1009 | @vindex hi-lock-file-patterns-policy |
| 1010 | The variable @code{hi-lock-file-patterns-policy} controls whether Hi |
| 1011 | Lock mode should automatically extract and highlight patterns found in a |
| 1012 | file when it is visited. Its value can be @code{nil} (never highlight), |
| 1013 | @code{ask} (query the user), or a function. If it is a function, |
| 1014 | @code{hi-lock-find-patterns} calls it with the patterns as argument; if |
| 1015 | the function returns non-@code{nil}, the patterns are used. The default |
| 1016 | is @code{ask}. Note that patterns are always highlighted if you call |
| 1017 | @code{hi-lock-find-patterns} directly, regardless of the value of this |
| 1018 | variable. |
| 1019 | |
| 1020 | @vindex hi-lock-exclude-modes |
| 1021 | Also, @code{hi-lock-find-patterns} does nothing if the current major |
| 1022 | mode's symbol is a member of the list @code{hi-lock-exclude-modes}. |
| 1023 | @end table |
| 1024 | |
| 1025 | @node Fringes |
| 1026 | @section Window Fringes |
| 1027 | @cindex fringes |
| 1028 | |
| 1029 | @findex set-fringe-style |
| 1030 | @findex fringe-mode |
| 1031 | @vindex fringe-mode @r{(variable)} |
| 1032 | On graphical displays, each Emacs window normally has narrow |
| 1033 | @dfn{fringes} on the left and right edges. The fringes are used to |
| 1034 | display symbols that provide information about the text in the window. |
| 1035 | You can type @kbd{M-x fringe-mode} to disable the fringes, or modify |
| 1036 | their width. This command affects fringes in all frames; to modify |
| 1037 | fringes on the selected frame only, use @kbd{M-x set-fringe-style}. |
| 1038 | You can make your changes to the fringes permanent by customizing the |
| 1039 | variable @code{fringe-mode}. |
| 1040 | |
| 1041 | The most common use of the fringes is to indicate a continuation |
| 1042 | line (@pxref{Continuation Lines}). When one line of text is split |
| 1043 | into multiple screen lines, the left fringe shows a curving arrow for |
| 1044 | each screen line except the first, indicating that ``this is not the |
| 1045 | real beginning''. The right fringe shows a curving arrow for each |
| 1046 | screen line except the last, indicating that ``this is not the real |
| 1047 | end''. If the line's direction is right-to-left (@pxref{Bidirectional |
| 1048 | Editing}), the meanings of the curving arrows in the fringes are |
| 1049 | swapped. |
| 1050 | |
| 1051 | The fringes indicate line truncation with short horizontal arrows |
| 1052 | meaning ``there's more text on this line which is scrolled |
| 1053 | horizontally out of view''. Clicking the mouse on one of the arrows |
| 1054 | scrolls the display horizontally in the direction of the arrow. |
| 1055 | |
| 1056 | The fringes can also indicate other things, such as buffer |
| 1057 | boundaries (@pxref{Displaying Boundaries}), and where a program you |
| 1058 | are debugging is executing (@pxref{Debuggers}). |
| 1059 | |
| 1060 | @vindex overflow-newline-into-fringe |
| 1061 | The fringe is also used for drawing the cursor, if the current line |
| 1062 | is exactly as wide as the window and point is at the end of the line. |
| 1063 | To disable this, change the variable |
| 1064 | @code{overflow-newline-into-fringe} to @code{nil}; this causes Emacs |
| 1065 | to continue or truncate lines that are exactly as wide as the window. |
| 1066 | |
| 1067 | @node Displaying Boundaries |
| 1068 | @section Displaying Boundaries |
| 1069 | |
| 1070 | @vindex indicate-buffer-boundaries |
| 1071 | On graphical displays, Emacs can indicate the buffer boundaries in |
| 1072 | the fringes. If you enable this feature, the first line and the last |
| 1073 | line are marked with angle images in the fringes. This can be |
| 1074 | combined with up and down arrow images which say whether it is |
| 1075 | possible to scroll the window. |
| 1076 | |
| 1077 | The buffer-local variable @code{indicate-buffer-boundaries} controls |
| 1078 | how the buffer boundaries and window scrolling is indicated in the |
| 1079 | fringes. If the value is @code{left} or @code{right}, both angle and |
| 1080 | arrow bitmaps are displayed in the left or right fringe, respectively. |
| 1081 | |
| 1082 | If value is an alist, each element @code{(@var{indicator} . |
| 1083 | @var{position})} specifies the position of one of the indicators. |
| 1084 | The @var{indicator} must be one of @code{top}, @code{bottom}, |
| 1085 | @code{up}, @code{down}, or @code{t} which specifies the default |
| 1086 | position for the indicators not present in the alist. |
| 1087 | The @var{position} is one of @code{left}, @code{right}, or @code{nil} |
| 1088 | which specifies not to show this indicator. |
| 1089 | |
| 1090 | For example, @code{((top . left) (t . right))} places the top angle |
| 1091 | bitmap in left fringe, the bottom angle bitmap in right fringe, and |
| 1092 | both arrow bitmaps in right fringe. To show just the angle bitmaps in |
| 1093 | the left fringe, but no arrow bitmaps, use @code{((top . left) |
| 1094 | (bottom . left))}. |
| 1095 | |
| 1096 | @node Useless Whitespace |
| 1097 | @section Useless Whitespace |
| 1098 | |
| 1099 | @cindex trailing whitespace |
| 1100 | @cindex whitespace, trailing |
| 1101 | @vindex show-trailing-whitespace |
| 1102 | It is easy to leave unnecessary spaces at the end of a line, or |
| 1103 | empty lines at the end of a buffer, without realizing it. In most |
| 1104 | cases, this @dfn{trailing whitespace} has no effect, but sometimes it |
| 1105 | can be a nuisance. |
| 1106 | |
| 1107 | You can make trailing whitespace at the end of a line visible by |
| 1108 | setting the buffer-local variable @code{show-trailing-whitespace} to |
| 1109 | @code{t}. Then Emacs displays trailing whitespace, using the face |
| 1110 | @code{trailing-whitespace}. |
| 1111 | |
| 1112 | This feature does not apply when point is at the end of the line |
| 1113 | containing the whitespace. Strictly speaking, that is ``trailing |
| 1114 | whitespace'' nonetheless, but displaying it specially in that case |
| 1115 | looks ugly while you are typing in new text. In this special case, |
| 1116 | the location of point is enough to show you that the spaces are |
| 1117 | present. |
| 1118 | |
| 1119 | @findex delete-trailing-whitespace |
| 1120 | @vindex delete-trailing-lines |
| 1121 | Type @kbd{M-x delete-trailing-whitespace} to delete all trailing |
| 1122 | whitespace. This command deletes all extra spaces at the end of each |
| 1123 | line in the buffer, and all empty lines at the end of the buffer; to |
| 1124 | ignore the latter, change the variable @code{delete-trailing-lines} to |
| 1125 | @code{nil}. If the region is active, the command instead deletes |
| 1126 | extra spaces at the end of each line in the region. |
| 1127 | |
| 1128 | @vindex indicate-empty-lines |
| 1129 | @cindex unused lines |
| 1130 | @cindex fringes, and unused line indication |
| 1131 | On graphical displays, Emacs can indicate unused lines at the end of |
| 1132 | the window with a small image in the left fringe (@pxref{Fringes}). |
| 1133 | The image appears for screen lines that do not correspond to any |
| 1134 | buffer text, so blank lines at the end of the buffer stand out because |
| 1135 | they lack this image. To enable this feature, set the buffer-local |
| 1136 | variable @code{indicate-empty-lines} to a non-@code{nil} value. You |
| 1137 | can enable or disable this feature for all new buffers by setting the |
| 1138 | default value of this variable, e.g., @code{(setq-default |
| 1139 | indicate-empty-lines t)}. |
| 1140 | |
| 1141 | @cindex Whitespace mode |
| 1142 | @cindex mode, Whitespace |
| 1143 | @findex whitespace-mode |
| 1144 | @vindex whitespace-style |
| 1145 | Whitespace mode is a buffer-local minor mode that lets you |
| 1146 | ``visualize'' many kinds of whitespace in the buffer, by either |
| 1147 | drawing the whitespace characters with a special face or displaying |
| 1148 | them as special glyphs. To toggle this mode, type @kbd{M-x |
| 1149 | whitespace-mode}. The kinds of whitespace visualized are determined |
| 1150 | by the list variable @code{whitespace-style}. Here is a partial list |
| 1151 | of possible elements (see the variable's documentation for the full |
| 1152 | list): |
| 1153 | |
| 1154 | @table @code |
| 1155 | @item face |
| 1156 | Enable all visualizations which use special faces. This element has a |
| 1157 | special meaning: if it is absent from the list, none of the other |
| 1158 | visualizations take effect except @code{space-mark}, @code{tab-mark}, |
| 1159 | and @code{newline-mark}. |
| 1160 | |
| 1161 | @item trailing |
| 1162 | Highlight trailing whitespace. |
| 1163 | |
| 1164 | @item tabs |
| 1165 | Highlight tab characters. |
| 1166 | |
| 1167 | @item spaces |
| 1168 | Highlight space and non-breaking space characters. |
| 1169 | |
| 1170 | @item lines |
| 1171 | @vindex whitespace-line-column |
| 1172 | Highlight lines longer than 80 lines. To change the column limit, |
| 1173 | customize the variable @code{whitespace-line-column}. |
| 1174 | |
| 1175 | @item newline |
| 1176 | Highlight newlines. |
| 1177 | |
| 1178 | @item empty |
| 1179 | Highlight empty lines. |
| 1180 | |
| 1181 | @item space-mark |
| 1182 | Draw space and non-breaking characters with a special glyph. |
| 1183 | |
| 1184 | @item tab-mark |
| 1185 | Draw tab characters with a special glyph. |
| 1186 | |
| 1187 | @item newline-mark |
| 1188 | Draw newline characters with a special glyph. |
| 1189 | @end table |
| 1190 | |
| 1191 | @node Selective Display |
| 1192 | @section Selective Display |
| 1193 | @cindex selective display |
| 1194 | @findex set-selective-display |
| 1195 | @kindex C-x $ |
| 1196 | |
| 1197 | Emacs has the ability to hide lines indented more than a given |
| 1198 | number of columns. You can use this to get an overview of a part of a |
| 1199 | program. |
| 1200 | |
| 1201 | To hide lines in the current buffer, type @kbd{C-x $} |
| 1202 | (@code{set-selective-display}) with a numeric argument @var{n}. Then |
| 1203 | lines with at least @var{n} columns of indentation disappear from the |
| 1204 | screen. The only indication of their presence is that three dots |
| 1205 | (@samp{@dots{}}) appear at the end of each visible line that is |
| 1206 | followed by one or more hidden ones. |
| 1207 | |
| 1208 | The commands @kbd{C-n} and @kbd{C-p} move across the hidden lines as |
| 1209 | if they were not there. |
| 1210 | |
| 1211 | The hidden lines are still present in the buffer, and most editing |
| 1212 | commands see them as usual, so you may find point in the middle of the |
| 1213 | hidden text. When this happens, the cursor appears at the end of the |
| 1214 | previous line, after the three dots. If point is at the end of the |
| 1215 | visible line, before the newline that ends it, the cursor appears before |
| 1216 | the three dots. |
| 1217 | |
| 1218 | To make all lines visible again, type @kbd{C-x $} with no argument. |
| 1219 | |
| 1220 | @vindex selective-display-ellipses |
| 1221 | If you set the variable @code{selective-display-ellipses} to |
| 1222 | @code{nil}, the three dots do not appear at the end of a line that |
| 1223 | precedes hidden lines. Then there is no visible indication of the |
| 1224 | hidden lines. This variable becomes local automatically when set. |
| 1225 | |
| 1226 | See also @ref{Outline Mode} for another way to hide part of |
| 1227 | the text in a buffer. |
| 1228 | |
| 1229 | @node Optional Mode Line |
| 1230 | @section Optional Mode Line Features |
| 1231 | |
| 1232 | @cindex buffer size display |
| 1233 | @cindex display of buffer size |
| 1234 | @findex size-indication-mode |
| 1235 | The buffer percentage @var{pos} indicates the percentage of the |
| 1236 | buffer above the top of the window. You can additionally display the |
| 1237 | size of the buffer by typing @kbd{M-x size-indication-mode} to turn on |
| 1238 | Size Indication mode. The size will be displayed immediately |
| 1239 | following the buffer percentage like this: |
| 1240 | |
| 1241 | @example |
| 1242 | @var{POS} of @var{SIZE} |
| 1243 | @end example |
| 1244 | |
| 1245 | @noindent |
| 1246 | Here @var{SIZE} is the human readable representation of the number of |
| 1247 | characters in the buffer, which means that @samp{k} for 10^3, @samp{M} |
| 1248 | for 10^6, @samp{G} for 10^9, etc., are used to abbreviate. |
| 1249 | |
| 1250 | @cindex line number display |
| 1251 | @cindex display of line number |
| 1252 | @findex line-number-mode |
| 1253 | The current line number of point appears in the mode line when Line |
| 1254 | Number mode is enabled. Use the command @kbd{M-x line-number-mode} to |
| 1255 | turn this mode on and off; normally it is on. The line number appears |
| 1256 | after the buffer percentage @var{pos}, with the letter @samp{L} to |
| 1257 | indicate what it is. |
| 1258 | |
| 1259 | @cindex Column Number mode |
| 1260 | @cindex mode, Column Number |
| 1261 | @findex column-number-mode |
| 1262 | Similarly, you can display the current column number by turning on |
| 1263 | Column number mode with @kbd{M-x column-number-mode}. The column |
| 1264 | number is indicated by the letter @samp{C}. However, when both of |
| 1265 | these modes are enabled, the line and column numbers are displayed in |
| 1266 | parentheses, the line number first, rather than with @samp{L} and |
| 1267 | @samp{C}. For example: @samp{(561,2)}. @xref{Minor Modes}, for more |
| 1268 | information about minor modes and about how to use these commands. |
| 1269 | |
| 1270 | @cindex narrowing, and line number display |
| 1271 | If you have narrowed the buffer (@pxref{Narrowing}), the displayed |
| 1272 | line number is relative to the accessible portion of the buffer. |
| 1273 | Thus, it isn't suitable as an argument to @code{goto-line}. (Use |
| 1274 | @code{what-line} command to see the line number relative to the whole |
| 1275 | file.) |
| 1276 | |
| 1277 | @vindex line-number-display-limit |
| 1278 | If the buffer is very large (larger than the value of |
| 1279 | @code{line-number-display-limit}), Emacs won't compute the line |
| 1280 | number, because that would be too slow; therefore, the line number |
| 1281 | won't appear on the mode-line. To remove this limit, set |
| 1282 | @code{line-number-display-limit} to @code{nil}. |
| 1283 | |
| 1284 | @vindex line-number-display-limit-width |
| 1285 | Line-number computation can also be slow if the lines in the buffer |
| 1286 | are too long. For this reason, Emacs doesn't display line numbers if |
| 1287 | the average width, in characters, of lines near point is larger than |
| 1288 | the value of @code{line-number-display-limit-width}. The default |
| 1289 | value is 200 characters. |
| 1290 | |
| 1291 | @findex display-time |
| 1292 | @cindex time (on mode line) |
| 1293 | Emacs can optionally display the time and system load in all mode |
| 1294 | lines. To enable this feature, type @kbd{M-x display-time} or customize |
| 1295 | the option @code{display-time-mode}. The information added to the mode |
| 1296 | line looks like this: |
| 1297 | |
| 1298 | @example |
| 1299 | @var{hh}:@var{mm}pm @var{l.ll} |
| 1300 | @end example |
| 1301 | |
| 1302 | @noindent |
| 1303 | @vindex display-time-24hr-format |
| 1304 | Here @var{hh} and @var{mm} are the hour and minute, followed always by |
| 1305 | @samp{am} or @samp{pm}. @var{l.ll} is the average number, collected |
| 1306 | for the last few minutes, of processes in the whole system that were |
| 1307 | either running or ready to run (i.e., were waiting for an available |
| 1308 | processor). (Some fields may be missing if your operating system |
| 1309 | cannot support them.) If you prefer time display in 24-hour format, |
| 1310 | set the variable @code{display-time-24hr-format} to @code{t}. |
| 1311 | |
| 1312 | @cindex mail (on mode line) |
| 1313 | @vindex display-time-use-mail-icon |
| 1314 | @vindex display-time-mail-face |
| 1315 | @vindex display-time-mail-file |
| 1316 | @vindex display-time-mail-directory |
| 1317 | The word @samp{Mail} appears after the load level if there is mail |
| 1318 | for you that you have not read yet. On graphical displays, you can |
| 1319 | use an icon instead of @samp{Mail} by customizing |
| 1320 | @code{display-time-use-mail-icon}; this may save some space on the |
| 1321 | mode line. You can customize @code{display-time-mail-face} to make |
| 1322 | the mail indicator prominent. Use @code{display-time-mail-file} to |
| 1323 | specify the mail file to check, or set |
| 1324 | @code{display-time-mail-directory} to specify the directory to check |
| 1325 | for incoming mail (any nonempty regular file in the directory is |
| 1326 | considered as ``newly arrived mail''). |
| 1327 | |
| 1328 | @cindex battery status (on mode line) |
| 1329 | @findex display-battery-mode |
| 1330 | @vindex display-battery-mode |
| 1331 | @vindex battery-mode-line-format |
| 1332 | When running Emacs on a laptop computer, you can display the battery |
| 1333 | charge on the mode-line, by using the command |
| 1334 | @code{display-battery-mode} or customizing the variable |
| 1335 | @code{display-battery-mode}. The variable |
| 1336 | @code{battery-mode-line-format} determines the way the battery charge |
| 1337 | is displayed; the exact mode-line message depends on the operating |
| 1338 | system, and it usually shows the current battery charge as a |
| 1339 | percentage of the total charge. |
| 1340 | |
| 1341 | @cindex mode line, 3D appearance |
| 1342 | @cindex attributes of mode line, changing |
| 1343 | @cindex non-integral number of lines in a window |
| 1344 | On graphical displays, the mode line is drawn as a 3D box. If you |
| 1345 | don't like this effect, you can disable it by customizing the |
| 1346 | @code{mode-line} face and setting its @code{box} attribute to |
| 1347 | @code{nil}. @xref{Face Customization}. |
| 1348 | |
| 1349 | @cindex non-selected windows, mode line appearance |
| 1350 | By default, the mode line of nonselected windows is displayed in a |
| 1351 | different face, called @code{mode-line-inactive}. Only the selected |
| 1352 | window is displayed in the @code{mode-line} face. This helps show |
| 1353 | which window is selected. When the minibuffer is selected, since |
| 1354 | it has no mode line, the window from which you activated the minibuffer |
| 1355 | has its mode line displayed using @code{mode-line}; as a result, |
| 1356 | ordinary entry to the minibuffer does not change any mode lines. |
| 1357 | |
| 1358 | @vindex mode-line-in-non-selected-windows |
| 1359 | You can disable use of @code{mode-line-inactive} by setting variable |
| 1360 | @code{mode-line-in-non-selected-windows} to @code{nil}; then all mode |
| 1361 | lines are displayed in the @code{mode-line} face. |
| 1362 | |
| 1363 | @vindex eol-mnemonic-unix |
| 1364 | @vindex eol-mnemonic-dos |
| 1365 | @vindex eol-mnemonic-mac |
| 1366 | @vindex eol-mnemonic-undecided |
| 1367 | You can customize the mode line display for each of the end-of-line |
| 1368 | formats by setting each of the variables @code{eol-mnemonic-unix}, |
| 1369 | @code{eol-mnemonic-dos}, @code{eol-mnemonic-mac}, and |
| 1370 | @code{eol-mnemonic-undecided} to the strings you prefer. |
| 1371 | |
| 1372 | @node Text Display |
| 1373 | @section How Text Is Displayed |
| 1374 | @cindex characters (in text) |
| 1375 | @cindex printing character |
| 1376 | |
| 1377 | Most characters are @dfn{printing characters}: when they appear in a |
| 1378 | buffer, they are displayed literally on the screen. Printing |
| 1379 | characters include @acronym{ASCII} numbers, letters, and punctuation |
| 1380 | characters, as well as many non-@acronym{ASCII} characters. |
| 1381 | |
| 1382 | @vindex tab-width |
| 1383 | @cindex control characters on display |
| 1384 | The @acronym{ASCII} character set contains non-printing @dfn{control |
| 1385 | characters}. Two of these are displayed specially: the newline |
| 1386 | character (Unicode code point @code{U+000A}) is displayed by starting |
| 1387 | a new line, while the tab character (@code{U+0009}) is displayed as a |
| 1388 | space that extends to the next tab stop column (normally every 8 |
| 1389 | columns). The number of spaces per tab is controlled by the |
| 1390 | buffer-local variable @code{tab-width}, which must have an integer |
| 1391 | value between 1 and 1000, inclusive. Note that how the tab character |
| 1392 | in the buffer is displayed has nothing to do with the definition of |
| 1393 | @key{TAB} as a command. |
| 1394 | |
| 1395 | Other @acronym{ASCII} control characters, whose codes are below |
| 1396 | @code{U+0020} (octal 40, decimal 32), are displayed as a caret |
| 1397 | (@samp{^}) followed by the non-control version of the character, with |
| 1398 | the @code{escape-glyph} face. For instance, the @samp{control-A} |
| 1399 | character, @code{U+0001}, is displayed as @samp{^A}. |
| 1400 | |
| 1401 | @cindex octal escapes |
| 1402 | @vindex ctl-arrow |
| 1403 | The raw bytes with codes @code{U+0080} (octal 200) through |
| 1404 | @code{U+009F} (octal 237) are displayed as @dfn{octal escape |
| 1405 | sequences}, with the @code{escape-glyph} face. For instance, |
| 1406 | character code @code{U+0098} (octal 230) is displayed as @samp{\230}. |
| 1407 | If you change the buffer-local variable @code{ctl-arrow} to |
| 1408 | @code{nil}, the @acronym{ASCII} control characters are also displayed |
| 1409 | as octal escape sequences instead of caret escape sequences. |
| 1410 | |
| 1411 | @vindex nobreak-char-display |
| 1412 | @cindex non-breaking space |
| 1413 | @cindex non-breaking hyphen |
| 1414 | @cindex soft hyphen |
| 1415 | Some non-@acronym{ASCII} characters have the same appearance as an |
| 1416 | @acronym{ASCII} space or hyphen (minus) character. Such characters |
| 1417 | can cause problems if they are entered into a buffer without your |
| 1418 | realization, e.g., by yanking; for instance, source code compilers |
| 1419 | typically do not treat non-@acronym{ASCII} spaces as whitespace |
| 1420 | characters. To deal with this problem, Emacs displays such characters |
| 1421 | specially: it displays @code{U+00A0} (no-break space) with the |
| 1422 | @code{nobreak-space} face, and it displays @code{U+00AD} (soft |
| 1423 | hyphen), @code{U+2010} (hyphen), and @code{U+2011} (non-breaking |
| 1424 | hyphen) with the @code{escape-glyph} face. To disable this, change |
| 1425 | the variable @code{nobreak-char-display} to @code{nil}. If you give |
| 1426 | this variable a non-@code{nil} and non-@code{t} value, Emacs instead |
| 1427 | displays such characters as a highlighted backslash followed by a |
| 1428 | space or hyphen. |
| 1429 | |
| 1430 | You can customize the way any particular character code is displayed |
| 1431 | by means of a display table. @xref{Display Tables,, Display Tables, |
| 1432 | elisp, The Emacs Lisp Reference Manual}. |
| 1433 | |
| 1434 | @cindex glyphless characters |
| 1435 | @cindex characters with no font glyphs |
| 1436 | On graphical displays, some characters may have no glyphs in any of |
| 1437 | the fonts available to Emacs. These @dfn{glyphless characters} are |
| 1438 | normally displayed as boxes containing the hexadecimal character code. |
| 1439 | Similarly, on text terminals, characters that cannot be displayed |
| 1440 | using the terminal encoding (@pxref{Terminal Coding}) are normally |
| 1441 | displayed as question signs. You can control the display method by |
| 1442 | customizing the variable @code{glyphless-char-display-control}. |
| 1443 | @xref{Glyphless Chars,, Glyphless Character Display, elisp, The Emacs |
| 1444 | Lisp Reference Manual}, for details. |
| 1445 | |
| 1446 | @node Cursor Display |
| 1447 | @section Displaying the Cursor |
| 1448 | @cindex text cursor |
| 1449 | |
| 1450 | @vindex visible-cursor |
| 1451 | On a text terminal, the cursor's appearance is controlled by the |
| 1452 | terminal, largely out of the control of Emacs. Some terminals offer |
| 1453 | two different cursors: a ``visible'' static cursor, and a ``very |
| 1454 | visible'' blinking cursor. By default, Emacs uses the very visible |
| 1455 | cursor, and switches to it when you start or resume Emacs. If the |
| 1456 | variable @code{visible-cursor} is @code{nil} when Emacs starts or |
| 1457 | resumes, it uses the normal cursor. |
| 1458 | |
| 1459 | @cindex cursor face |
| 1460 | @vindex cursor-type |
| 1461 | On a graphical display, many more properties of the text cursor can |
| 1462 | be altered. To customize its color, change the @code{:background} |
| 1463 | attribute of the face named @code{cursor} (@pxref{Face |
| 1464 | Customization}). (The other attributes of this face have no effect; |
| 1465 | the text shown under the cursor is drawn using the frame's background |
| 1466 | color.) To change its shape, customize the buffer-local variable |
| 1467 | @code{cursor-type}; possible values are @code{box} (the default), |
| 1468 | @code{hollow} (a hollow box), @code{bar} (a vertical bar), @code{(bar |
| 1469 | . @var{n})} (a vertical bar @var{n} pixels wide), @code{hbar} (a |
| 1470 | horizontal bar), @code{(hbar . @var{n})} (a horizontal bar @var{n} |
| 1471 | pixels tall), or @code{nil} (no cursor at all). |
| 1472 | |
| 1473 | @findex blink-cursor-mode |
| 1474 | @cindex cursor, blinking |
| 1475 | @cindex blinking cursor |
| 1476 | @vindex blink-cursor-mode |
| 1477 | @vindex blink-cursor-blinks |
| 1478 | @vindex blink-cursor-alist |
| 1479 | By default, the cursor stops blinking after 10 blinks. This can be |
| 1480 | changed by customizing the variable @code{blink-cursor-blinks}. To |
| 1481 | disable cursor blinking altogether, change the variable |
| 1482 | @code{blink-cursor-mode} to @code{nil} (@pxref{Easy Customization}), |
| 1483 | or add the line @code{(blink-cursor-mode 0)} to your init file. |
| 1484 | Alternatively, you can change how the cursor looks when it ``blinks |
| 1485 | off'' by customizing the list variable @code{blink-cursor-alist}. |
| 1486 | Each element in the list should have the form @code{(@var{on-type} |
| 1487 | . @var{off-type})}; this means that if the cursor is displayed as |
| 1488 | @var{on-type} when it blinks on (where @var{on-type} is one of the |
| 1489 | cursor types described above), then it is displayed as @var{off-type} |
| 1490 | when it blinks off. |
| 1491 | |
| 1492 | @vindex x-stretch-cursor |
| 1493 | @cindex wide block cursor |
| 1494 | Some characters, such as tab characters, are ``extra wide''. When |
| 1495 | the cursor is positioned over such a character, it is normally drawn |
| 1496 | with the default character width. You can make the cursor stretch to |
| 1497 | cover wide characters, by changing the variable |
| 1498 | @code{x-stretch-cursor} to a non-@code{nil} value. |
| 1499 | |
| 1500 | @cindex cursor in non-selected windows |
| 1501 | @vindex cursor-in-non-selected-windows |
| 1502 | The cursor normally appears in non-selected windows as a |
| 1503 | non-blinking hollow box. (For a bar cursor, it instead appears as a |
| 1504 | thinner bar.) To turn off cursors in non-selected windows, change the |
| 1505 | variable @code{cursor-in-non-selected-windows} to @code{nil}. |
| 1506 | |
| 1507 | @findex hl-line-mode |
| 1508 | @findex global-hl-line-mode |
| 1509 | @cindex highlight current line |
| 1510 | To make the cursor even more visible, you can use HL Line mode, a |
| 1511 | minor mode that highlights the line containing point. Use @kbd{M-x |
| 1512 | hl-line-mode} to enable or disable it in the current buffer. @kbd{M-x |
| 1513 | global-hl-line-mode} enables or disables the same mode globally. |
| 1514 | |
| 1515 | @node Line Truncation |
| 1516 | @section Line Truncation |
| 1517 | |
| 1518 | @cindex truncation |
| 1519 | @cindex line truncation, and fringes |
| 1520 | As an alternative to continuation (@pxref{Continuation Lines}), |
| 1521 | Emacs can display long lines by @dfn{truncation}. This means that all |
| 1522 | the characters that do not fit in the width of the screen or window do |
| 1523 | not appear at all. On graphical displays, a small straight arrow in |
| 1524 | the fringe indicates truncation at either end of the line. On text |
| 1525 | terminals, this is indicated with @samp{$} signs in the leftmost |
| 1526 | and/or rightmost columns. |
| 1527 | |
| 1528 | @vindex truncate-lines |
| 1529 | @findex toggle-truncate-lines |
| 1530 | Horizontal scrolling automatically causes line truncation |
| 1531 | (@pxref{Horizontal Scrolling}). You can explicitly enable line |
| 1532 | truncation for a particular buffer with the command @kbd{M-x |
| 1533 | toggle-truncate-lines}. This works by locally changing the variable |
| 1534 | @code{truncate-lines}. If that variable is non-@code{nil}, long lines |
| 1535 | are truncated; if it is @code{nil}, they are continued onto multiple |
| 1536 | screen lines. Setting the variable @code{truncate-lines} in any way |
| 1537 | makes it local to the current buffer; until that time, the default |
| 1538 | value, which is normally @code{nil}, is in effect. |
| 1539 | |
| 1540 | @vindex truncate-partial-width-windows |
| 1541 | If a split window becomes too narrow, Emacs may automatically enable |
| 1542 | line truncation. @xref{Split Window}, for the variable |
| 1543 | @code{truncate-partial-width-windows} which controls this. |
| 1544 | |
| 1545 | @node Visual Line Mode |
| 1546 | @section Visual Line Mode |
| 1547 | |
| 1548 | @cindex word wrap |
| 1549 | Another alternative to ordinary line continuation is to use |
| 1550 | @dfn{word wrap}. Here, each long logical line is divided into two or |
| 1551 | more screen lines, like in ordinary line continuation. However, Emacs |
| 1552 | attempts to wrap the line at word boundaries near the right window |
| 1553 | edge. This makes the text easier to read, as wrapping does not occur |
| 1554 | in the middle of words. |
| 1555 | |
| 1556 | @cindex mode, Visual Line |
| 1557 | @cindex Visual Line mode |
| 1558 | @findex visual-line-mode |
| 1559 | @findex global-visual-line-mode |
| 1560 | Word wrap is enabled by Visual Line mode, an optional minor mode. |
| 1561 | To turn on Visual Line mode in the current buffer, type @kbd{M-x |
| 1562 | visual-line-mode}; repeating this command turns it off. You can also |
| 1563 | turn on Visual Line mode using the menu bar: in the Options menu, |
| 1564 | select the @samp{Line Wrapping in this Buffer} submenu, followed by |
| 1565 | the @samp{Word Wrap (Visual Line Mode)} menu item. While Visual Line |
| 1566 | mode is enabled, the mode-line shows the string @samp{wrap} in the |
| 1567 | mode display. The command @kbd{M-x global-visual-line-mode} toggles |
| 1568 | Visual Line mode in all buffers. |
| 1569 | |
| 1570 | @findex beginning-of-visual-line |
| 1571 | @findex end-of-visual-line |
| 1572 | @findex next-logical-line |
| 1573 | @findex previous-logical-line |
| 1574 | In Visual Line mode, some editing commands work on screen lines |
| 1575 | instead of logical lines: @kbd{C-a} (@code{beginning-of-visual-line}) |
| 1576 | moves to the beginning of the screen line, @kbd{C-e} |
| 1577 | (@code{end-of-visual-line}) moves to the end of the screen line, and |
| 1578 | @kbd{C-k} (@code{kill-visual-line}) kills text to the end of the |
| 1579 | screen line. |
| 1580 | |
| 1581 | To move by logical lines, use the commands @kbd{M-x |
| 1582 | next-logical-line} and @kbd{M-x previous-logical-line}. These move |
| 1583 | point to the next logical line and the previous logical line |
| 1584 | respectively, regardless of whether Visual Line mode is enabled. If |
| 1585 | you use these commands frequently, it may be convenient to assign key |
| 1586 | bindings to them. @xref{Init Rebinding}. |
| 1587 | |
| 1588 | By default, word-wrapped lines do not display fringe indicators. |
| 1589 | Visual Line mode is often used to edit files that contain many long |
| 1590 | logical lines, so having a fringe indicator for each wrapped line |
| 1591 | would be visually distracting. You can change this by customizing the |
| 1592 | variable @code{visual-line-fringe-indicators}. |
| 1593 | |
| 1594 | @node Display Custom |
| 1595 | @section Customization of Display |
| 1596 | |
| 1597 | This section describes variables that control miscellaneous aspects |
| 1598 | of the appearance of the Emacs screen. Beginning users can skip it. |
| 1599 | |
| 1600 | @vindex visible-bell |
| 1601 | If the variable @code{visible-bell} is non-@code{nil}, Emacs attempts |
| 1602 | to make the whole screen blink when it would normally make an audible bell |
| 1603 | sound. This variable has no effect if your terminal does not have a way |
| 1604 | to make the screen blink. |
| 1605 | |
| 1606 | @vindex echo-keystrokes |
| 1607 | The variable @code{echo-keystrokes} controls the echoing of multi-character |
| 1608 | keys; its value is the number of seconds of pause required to cause echoing |
| 1609 | to start, or zero, meaning don't echo at all. The value takes effect when |
| 1610 | there is something to echo. @xref{Echo Area}. |
| 1611 | |
| 1612 | @cindex mouse pointer |
| 1613 | @cindex hourglass pointer display |
| 1614 | @vindex display-hourglass |
| 1615 | @vindex hourglass-delay |
| 1616 | On graphical displays, Emacs displays the mouse pointer as an |
| 1617 | hourglass if Emacs is busy. To disable this feature, set the variable |
| 1618 | @code{display-hourglass} to @code{nil}. The variable |
| 1619 | @code{hourglass-delay} determines the number of seconds of ``busy |
| 1620 | time'' before the hourglass is shown; the default is 1. |
| 1621 | |
| 1622 | @vindex make-pointer-invisible |
| 1623 | If the mouse pointer lies inside an Emacs frame, Emacs makes it |
| 1624 | invisible each time you type a character to insert text, to prevent it |
| 1625 | from obscuring the text. (To be precise, the hiding occurs when you |
| 1626 | type a ``self-inserting'' character. @xref{Inserting Text}.) Moving |
| 1627 | the mouse pointer makes it visible again. To disable this feature, |
| 1628 | set the variable @code{make-pointer-invisible} to @code{nil}. |
| 1629 | |
| 1630 | @vindex underline-minimum-offset |
| 1631 | @vindex x-underline-at-descent-line |
| 1632 | On graphical displays, the variable @code{underline-minimum-offset} |
| 1633 | determines the minimum distance between the baseline and underline, in |
| 1634 | pixels, for underlined text. By default, the value is 1; increasing |
| 1635 | it may improve the legibility of underlined text for certain fonts. |
| 1636 | (However, Emacs will never draw the underline below the current line |
| 1637 | area.) The variable @code{x-underline-at-descent-line} determines how |
| 1638 | to draw underlined text. The default is @code{nil}, which means to |
| 1639 | draw it at the baseline level of the font; if you change it to |
| 1640 | @code{nil}, Emacs draws the underline at the same height as the font's |
| 1641 | descent line. |
| 1642 | |
| 1643 | @vindex overline-margin |
| 1644 | The variable @code{overline-margin} specifies the vertical position |
| 1645 | of an overline above the text, including the height of the overline |
| 1646 | itself, in pixels; the default is 2. |
| 1647 | |
| 1648 | @findex tty-suppress-bold-inverse-default-colors |
| 1649 | On some text terminals, bold face and inverse video together result |
| 1650 | in text that is hard to read. Call the function |
| 1651 | @code{tty-suppress-bold-inverse-default-colors} with a non-@code{nil} |
| 1652 | argument to suppress the effect of bold-face in this case. |