X-Git-Url: https://git.hcoop.net/bpt/emacs.git/blobdiff_plain/860dab78d36f1e56a2b866d592920839b8bd92de..289978b5e2fb86a4d433e84c0de9a1f8f7f8e809:/man/display.texi diff --git a/man/display.texi b/man/display.texi index aab2493ff3..2c530ec480 100644 --- a/man/display.texi +++ b/man/display.texi @@ -1,5 +1,6 @@ @c This is part of the Emacs manual. -@c Copyright (C) 1985, 86, 87, 93, 94, 95, 1997 Free Software Foundation, Inc. +@c Copyright (C) 1985, 86, 87, 93, 94, 95, 1997, 2000, 2001, 2002 +@c Free Software Foundation, Inc. @c See file emacs.texi for copying conditions. @node Display, Search, Registers, Top @chapter Controlling the Display @@ -10,15 +11,400 @@ allow you to specify which part of the text you want to see, and how to display it. @menu +* Faces:: How to change the display style using faces. +* Font Lock:: Minor mode for syntactic highlighting using faces. +* Highlight Changes:: Using colors to show where you changed the buffer. +* Highlight Interactively:: Tell Emacs what text to highlight. * Scrolling:: Moving text up and down in a window. * Horizontal Scrolling:: Moving text left and right in a window. +* Fringes:: Enabling or disabling window fringes. +* Useless Whitespace:: Showing possibly-spurious trailing whitespace. * Follow Mode:: Follow mode lets two windows scroll as one. * Selective Display:: Hiding lines with lots of indentation. * Optional Mode Line:: Optional mode line display features. * Text Display:: How text characters are normally displayed. -* Display Vars:: Information on variables for customizing display. +* Display Custom:: Information on variables for customizing display. +* Cursor Display:: Features for displaying the cursor. @end menu +@node Faces +@section Using Multiple Typefaces +@cindex faces + + Emacs supports using multiple styles of displaying characters. Each +style is called a @dfn{face}. Each face can specify various @dfn{face +attributes}, such as the font family, the height, weight and slant of +the characters, the foreground and background color, and underlining +or overlining. A face does not have to specify all of these +attributes; often it inherits many of them from another face. + + On a window system, all the Emacs face attributes are meaningful. +On a character terminal, only some of them work. Some character +terminals support inverse video, bold, and underline attributes; some +support colors. Character terminals generally do not support changing +the height and width or the font family. + + Features which rely on text in multiple faces (such as Font Lock mode) +will also work on non-windowed terminals that can display more than one +face, whether by colors or underlining and emboldening. This includes +the console on GNU/Linux, an @code{xterm} which supports colors, the +MS-DOS display (@pxref{MS-DOS}), and the MS-Windows version invoked with +the @option{-nw} option. Emacs determines automatically whether the +terminal has this capability. + + You control the appearance of a part of the text in the buffer by +specifying the face or faces to use for it. The style of display used +for any given character is determined by combining the attributes of +all the applicable faces specified for that character. Any attribute +that isn't specified by these faces is taken from the @code{default} face, +whose attributes reflect the default settings of the frame itself. + + Enriched mode, the mode for editing formatted text, includes several +commands and menus for specifying faces for text in the buffer. +@xref{Format Faces}, for how to specify the font for text in the +buffer. @xref{Format Colors}, for how to specify the foreground and +background color. + +@cindex face colors, setting +@findex set-face-foreground +@findex set-face-background + To alter the appearance of a face, use the customization buffer. +@xref{Face Customization}. You can also use X resources to specify +attributes of particular faces (@pxref{Resources}). Alternatively, +you can change the foreground and background colors of a specific face +with @kbd{M-x set-face-foreground} and @kbd{M-x set-face-background}. +These commands prompt in the minibuffer for a face name and a color +name, with completion, and then set that face to use the specified +color. Changing the colors of the @code{default} face also changes +the foreground and background colors on all frames, both existing and +those to be created in the future. (You can also set foreground and +background colors for the current frame only; see @ref{Frame +Parameters}.) + + Emacs 21 can correctly display variable-width fonts, but Emacs +commands that calculate width and indentation do not know how to +calculate variable widths. This can sometimes lead to incorrect +results when you use variable-width fonts. In particular, indentation +commands can give inconsistent results, so we recommend you avoid +variable-width fonts for editing program source code. Filling will +sometimes make lines too long or too short. We plan to address these +issues in future Emacs versions. + +@findex list-faces-display + To see what faces are currently defined, and what they look like, type +@kbd{M-x list-faces-display}. It's possible for a given face to look +different in different frames; this command shows the appearance in the +frame in which you type it. Here's a list of the standard defined +faces: + +@table @code +@item default +This face is used for ordinary text that doesn't specify any other face. +@item mode-line +This face is used for the mode line of the currently selected window. +By default, it's drawn with shadows for a ``raised'' effect on window +systems, and drawn as the inverse of the default face on non-windowed +terminals. @xref{Display Custom}. +@item mode-line-inactive +Like @code{mode-line}, but used for mode lines of the windows other +than the selected one (if @code{mode-line-in-non-selected-windows} is +non-@code{nil}). This face inherits from @code{mode-line}, so changes +in that face affect mode lines in all windows. +@item header-line +Similar to @code{mode-line} for a window's header line. Most modes +don't use the header line, but the Info mode does. +@item minibuffer-prompt +This face is used for the prompt strings displayed in the minibuffer. +@item highlight +This face is used for highlighting portions of text, in various modes. +For example, mouse-sensitive text is highlighted using this face. +@item isearch +This face is used for highlighting Isearch matches. +@item isearch-lazy-highlight-face +This face is used for lazy highlighting of Isearch matches other than +the current one. +@item region +This face is used for displaying a selected region (when Transient Mark +mode is enabled---see below). +@item secondary-selection +This face is used for displaying a secondary X selection (@pxref{Secondary +Selection}). +@item bold +This face uses a bold variant of the default font, if it has one. +@item italic +This face uses an italic variant of the default font, if it has one. +@item bold-italic +This face uses a bold italic variant of the default font, if it has one. +@item underline +This face underlines text. +@item fixed-pitch +The basic fixed-pitch face. +@item fringe +@cindex fringe +The face for the fringes to the left and right of windows on graphic +displays. (The fringes are the narrow portions of the Emacs frame +between the text area and the window's right and left borders.) +@item scroll-bar +This face determines the visual appearance of the scroll bar. +@item border +This face determines the color of the frame border. +@item cursor +This face determines the color of the cursor. +@item mouse +This face determines the color of the mouse pointer. +@item tool-bar +This is the basic tool-bar face. No text appears in the tool bar, but the +colors of this face affect the appearance of tool bar icons. +@item tooltip +This face is used for tooltips. +@item menu +This face determines the colors and font of Emacs's menus. Setting the +font of LessTif/Motif menus is currently not supported; attempts to set +the font are ignored in this case. +@item trailing-whitespace +The face for highlighting trailing whitespace when +@code{show-trailing-whitespace} is non-@code{nil}; see @ref{Useless +Whitespace}. +@item variable-pitch +The basic variable-pitch face. +@end table + +@cindex @code{region} face + When Transient Mark mode is enabled, the text of the region is +highlighted when the mark is active. This uses the face named +@code{region}; you can control the style of highlighting by changing the +style of this face (@pxref{Face Customization}). @xref{Transient Mark}, +for more information about Transient Mark mode and activation and +deactivation of the mark. + + One easy way to use faces is to turn on Font Lock mode. This minor +mode, which is always local to a particular buffer, arranges to +choose faces according to the syntax of the text you are editing. It +can recognize comments and strings in most languages; in several +languages, it can also recognize and properly highlight various other +important constructs. @xref{Font Lock}, for more information about +Font Lock mode and syntactic highlighting. + + You can print out the buffer with the highlighting that appears +on your screen using the command @code{ps-print-buffer-with-faces}. +@xref{PostScript}. + +@node Font Lock +@section Font Lock mode +@cindex Font Lock mode +@cindex mode, Font Lock +@cindex syntax highlighting and coloring + + Font Lock mode is a minor mode, always local to a particular buffer, +which highlights (or ``fontifies'') using various faces according to +the syntax of the text you are editing. It can recognize comments and +strings in most languages; in several languages, it can also recognize +and properly highlight various other important constructs---for +example, names of functions being defined or reserved keywords. +Some special modes, such as Occur mode and Info mode, have completely +specialized ways of assigning fonts for Font Lock mode. + +@findex font-lock-mode +@findex turn-on-font-lock + The command @kbd{M-x font-lock-mode} turns Font Lock mode on or off +according to the argument, and toggles the mode when it has no argument. +The function @code{turn-on-font-lock} unconditionally enables Font Lock +mode. This is useful in mode-hook functions. For example, to enable +Font Lock mode whenever you edit a C file, you can do this: + +@example +(add-hook 'c-mode-hook 'turn-on-font-lock) +@end example + +@findex global-font-lock-mode +@vindex global-font-lock-mode + To turn on Font Lock mode automatically in all modes which support +it, customize the user option @code{global-font-lock-mode} or use the +function @code{global-font-lock-mode} in your @file{.emacs} file, like +this: + +@example +(global-font-lock-mode 1) +@end example + + Font Lock mode uses several specifically named faces to do its job, +including @code{font-lock-string-face}, @code{font-lock-comment-face}, +and others. The easiest way to find them all is to use completion +on the face name in @code{set-face-foreground}. + + To change the colors or the fonts used by Font Lock mode to fontify +different parts of text, just change these faces. There are +two ways to do it: + +@itemize @bullet +@item +Invoke @kbd{M-x set-face-foreground} or @kbd{M-x set-face-background} +to change the colors of a particular face used by Font Lock. +@xref{Faces}. The command @kbd{M-x list-faces-display} displays all +the faces currently known to Emacs, including those used by Font Lock. + +@item +Customize the faces interactively with @kbd{M-x customize-face}, as +described in @ref{Face Customization}. +@end itemize + + To get the full benefit of Font Lock mode, you need to choose a +default font which has bold, italic, and bold-italic variants; or else +you need to have a color or gray-scale screen. + +@vindex font-lock-maximum-decoration + The variable @code{font-lock-maximum-decoration} specifies the +preferred level of fontification, for modes that provide multiple +levels. Level 1 is the least amount of fontification; some modes +support levels as high as 3. The normal default is ``as high as +possible.'' You can specify an integer, which applies to all modes, or +you can specify different numbers for particular major modes; for +example, to use level 1 for C/C++ modes, and the default level +otherwise, use this: + +@example +(setq font-lock-maximum-decoration + '((c-mode . 1) (c++-mode . 1))) +@end example + +@vindex font-lock-maximum-size + Fontification can be too slow for large buffers, so you can suppress +it. The variable @code{font-lock-maximum-size} specifies a buffer size, +beyond which buffer fontification is suppressed. + +@c @w is used below to prevent a bad page-break. +@vindex font-lock-beginning-of-syntax-function +@cindex incorrect fontification +@cindex parenthesis in column zero and fontification +@cindex brace in column zero and fontification + Comment and string fontification (or ``syntactic'' fontification) +relies on analysis of the syntactic structure of the buffer text. For +the sake of speed, some modes, including C mode and Lisp mode, +rely on a special convention: an open-parenthesis or open-brace in the +leftmost column always defines the @w{beginning} of a defun, and is +thus always outside any string or comment. (@xref{Left Margin +Paren}.) If you don't follow this convention, Font Lock mode can +misfontify the text that follows an open-parenthesis or open-brace in +the leftmost column that is inside a string or comment. + +@cindex slow display during scrolling + The variable @code{font-lock-beginning-of-syntax-function} (always +buffer-local) specifies how Font Lock mode can find a position +guaranteed to be outside any comment or string. In modes which use the +leftmost column parenthesis convention, the default value of the variable +is @code{beginning-of-defun}---that tells Font Lock mode to use the +convention. If you set this variable to @code{nil}, Font Lock no longer +relies on the convention. This avoids incorrect results, but the price +is that, in some cases, fontification for a changed text must rescan +buffer text from the beginning of the buffer. This can considerably +slow down redisplay while scrolling, particularly if you are close to +the end of a large buffer. + +@findex font-lock-add-keywords + Font Lock highlighting patterns already exist for many modes, but you +may want to fontify additional patterns. You can use the function +@code{font-lock-add-keywords}, to add your own highlighting patterns for +a particular mode. For example, to highlight @samp{FIXME:} words in C +comments, use this: + +@example +(font-lock-add-keywords + 'c-mode + '(("\\<\\(FIXME\\):" 1 font-lock-warning-face t))) +@end example + +@findex font-lock-remove-keywords + To remove keywords from the font-lock highlighting patterns, use the +function @code{font-lock-remove-keywords}. @xref{Search-based +Fontification,,,elisp}, for documentation of the format of this list. + +@cindex just-in-time (JIT) font-lock +@cindex background syntax highlighting + Fontifying large buffers can take a long time. To avoid large +delays when a file is visited, Emacs fontifies only the visible +portion of a buffer. As you scroll through the buffer, each portion +that becomes visible is fontified as soon as it is displayed. The +parts of the buffer that are not displayed are fontified +``stealthily'', in the background, i.e.@: when Emacs is idle. You can +control this background fontification, called @dfn{Just-In-Time}, or +@dfn{JIT} Font Lock, by customizing various options in the +customization group @samp{jit-lock}. @xref{Specific Customization}. + +@node Highlight Changes +@section Highlight Changes Mode + +@findex highlight-changes-mode + Use @kbd{M-x highlight-changes-mode} to enable a minor mode +that uses faces (colors, typically) to indicate which parts of +the buffer were changed most recently. + +@node Highlight Interactively +@section Interactive Highlighting by Matching +@cindex highlighting by matching +@cindex interactive highlighting + + It is sometimes useful to highlight the strings that match a certain +regular expression. For example, you might wish to see all the +references to a certain variable in a program source file, or highlight +certain parts in a voluminous output of some program, or make certain +cliches stand out in an article. + +@findex hi-lock-mode + Use the @kbd{M-x hi-lock-mode} command to turn on a minor mode that +allows you to specify regular expressions of the text to be +highlighted. Hi-lock mode works like Font Lock (@pxref{Font Lock}), +except that it lets you specify explicitly what parts of text to +highlight. You control Hi-lock mode with these commands: + +@table @kbd +@item C-x w h @var{regexp} @key{RET} @var{face} @key{RET} +@kindex C-x w h +@findex highlight-regexp +Highlight text that matches +@var{regexp} using face @var{face} (@code{highlight-regexp}). +By using this command more than once, you can highlight various +parts of the text in different ways. + +@item C-x w r @var{regexp} @key{RET} +@kindex C-x w r +@findex unhighlight-regexp +Unhighlight @var{regexp} (@code{unhighlight-regexp}). You must enter +one of the regular expressions currently specified for highlighting. +(You can use completion, or choose from a menu, to enter one of them +conveniently.) + +@item C-x w l @var{regexp} @key{RET} @var{face} @key{RET} +@kindex C-x w l +@findex highlight-lines-matching-regexp +@cindex lines, highlighting +@cindex highlighting lines of text +Highlight entire lines containing a match for @var{regexp}, using face +@var{face} (@code{highlight-lines-matching-regexp}). + +@item C-x w b +@kindex C-x w b +@findex hi-lock-write-interactive-patterns +Insert all the current highlighting regexp/face pairs into the buffer +at point, with comment delimiters to prevent them from changing your +program. This key binding runs the +@code{hi-lock-write-interactive-patterns} command. + +These patterns will be read the next time you visit the file while +Hi-lock mode is enabled, or whenever you use the @kbd{M-x +hi-lock-find-patterns} command. + +@item C-x w i +@kindex C-x w i +@findex hi-lock-find-patterns +@vindex hi-lock-exclude-modes +Re-read regexp/face pairs in the current buffer +(@code{hi-lock-write-interactive-patterns}). The list of pairs is +found no matter where in the buffer it may be. + +This command does nothing if the major mode is a member of the list +@code{hi-lock-exclude-modes}. +@end table + @node Scrolling @section Scrolling @@ -43,10 +429,12 @@ point vertically within it (@code{recenter}). @item C-v Scroll forward (a windowful or a specified number of lines) (@code{scroll-up}). @item @key{NEXT} +@itemx @key{PAGEDOWN} Likewise, scroll forward. @item M-v Scroll backward (@code{scroll-down}). @item @key{PRIOR} +@itemx @key{PAGEUP} Likewise, scroll backward. @item @var{arg} C-l Scroll so point is on line @var{arg} (@code{recenter}). @@ -66,30 +454,42 @@ down from the top of the window. @kindex M-v @kindex NEXT @kindex PRIOR +@kindex PAGEDOWN +@kindex PAGEUP @findex scroll-up @findex scroll-down - The scrolling commands @kbd{C-v} and @kbd{M-v} let you move all the text -in the window up or down a few lines. @kbd{C-v} (@code{scroll-up}) with an -argument shows you that many more lines at the bottom of the window, moving -the text and point up together as @kbd{C-l} might. @kbd{C-v} with a -negative argument shows you more lines at the top of the window. -@kbd{M-v} (@code{scroll-down}) is like @kbd{C-v}, but moves in the -opposite direction. The function keys @key{NEXT} and @key{PRIOR} are -equivalent to @kbd{C-v} and @kbd{M-v}. - - The names of scroll commands are based on the direction that the text -moves in the window. Thus, the command to scroll forward is called -@code{scroll-up} because it moves the text upward on the screen. - @vindex next-screen-context-lines - To read the buffer a windowful at a time, use @kbd{C-v} with no argument. -It takes the last two lines at the bottom of the window and puts them at -the top, followed by nearly a whole windowful of lines not previously -visible. If point was in the text scrolled off the top, it moves to the -new top of the window. @kbd{M-v} with no argument moves backward with -overlap similarly. The number of lines of overlap across a @kbd{C-v} or -@kbd{M-v} is controlled by the variable @code{next-screen-context-lines}; by -default, it is 2. + To read the buffer a windowful at a time, use @kbd{C-v} +(@code{scroll-up}) with no argument. This scrolls forward by nearly +the whole window height. The effect is to take the two lines at the +bottom of the window and put them at the top, followed by nearly a +whole windowful of lines that were not previously visible. If point +was in the text that scrolled off the top, it ends up at the new top +of the window. + + @kbd{M-v} (@code{scroll-down}) with no argument scrolls backward in +a similar way, also with overlap. The number of lines of overlap +across a @kbd{C-v} or @kbd{M-v} is controlled by the variable +@code{next-screen-context-lines}; by default, it is 2. The function +keys @key{NEXT} and @key{PRIOR}, or @key{PAGEDOWN} and @key{PAGEUP}, +are equivalent to @kbd{C-v} and @kbd{M-v}. + + The commands @kbd{C-v} and @kbd{M-v} with a numeric argument scroll +the text in the selected window up or down a few lines. @kbd{C-v} +with an argument moves the text and point up, together, that many +lines; it brings the same number of new lines into view at the bottom +of the window. @kbd{M-v} with numeric argument scrolls the text +downward, bringing that many new lines into view at the top of the +window. @kbd{C-v} with a negative argument is like @kbd{M-v} and vice +versa. + + The names of scroll commands are based on the direction that the +text moves in the window. Thus, the command to scroll forward is +called @code{scroll-up} because it moves the text upward on the +screen. The keys @key{PAGEDOWN} and @key{PAGEUP} derive their names +and customary meanings from a different convention that developed +elsewhere; hence the strange result that @key{PAGEDOWN} runs +@code{scroll-up}. @vindex scroll-preserve-screen-position Some users like the full-screen scroll commands to keep point at the @@ -109,8 +509,8 @@ point on the very top line. Point does not move with respect to the text; rather, the text and point move rigidly on the screen. @kbd{C-l} with a negative argument puts point that many lines from the bottom of the window. For example, @kbd{C-u - 1 C-l} puts point on the bottom line, and @kbd{C-u -- 5 C-l} puts it five lines from the bottom. Just @kbd{C-u} as argument, -as in @kbd{C-u C-l}, scrolls point to the center of the selected window. +- 5 C-l} puts it five lines from the bottom. @kbd{C-u C-l} scrolls to put +point at the center (vertically) of the selected window. @kindex C-M-l @findex reposition-window @@ -120,34 +520,35 @@ the screen. For example, in a Lisp file, this command tries to get the entire current defun onto the screen if possible. @vindex scroll-conservatively - Scrolling happens automatically if point has moved out of the visible -portion of the text when it is time to display. Normally, automatic -scrolling centers point vertically within the window. However, if you -set @code{scroll-conservatively} to a small number @var{n}, then if you -move point just a little off the screen---less than @var{n} lines---then -Emacs scrolls the text just far enough to bring point back on screen. -By default, @code{scroll-conservatively} is 0. + Scrolling happens automatically when point moves out of the visible +portion of the text. Normally, automatic scrolling centers point +vertically within the window. However, if you set +@code{scroll-conservatively} to a small number @var{n}, then if you +move point just a little off the screen---less than @var{n} +lines---then Emacs scrolls the text just far enough to bring point +back on screen. By default, @code{scroll-conservatively} is 0. @cindex aggressive scrolling @vindex scroll-up-aggressively -@vindex scroll-down-aggressively - If you prefer a more aggressive scrolling, customize the values of the -variables @code{scroll-up-aggressively} and -@code{scroll-down-aggressively}. The value of -@code{scroll-up-aggressively} should be either nil or a fraction @var{f} -between 0 and 1. If it is a fraction, that specifies where on the -screen to put point when scrolling upward. More precisely, when a -window scrolls up because point is above the window start, the new start -position is chosen to put point @var{f} part of the window height from -the top. The larger @var{f}, the more aggressive the scrolling. - -A value of @code{nil} is equivalent to .5, since its effect is to center -point. - -Likewise, @code{scroll-down-aggressively} is used for scrolling down. -The value, @var{f}, specifies how far point should be placed from the -bottom of the window; thus, as with @code{scroll-up-aggressively}, a -larger value scrolls more aggressively. +@vindex scroll-down-aggressively + When the window does scroll by a longer distance, you can control +how aggressively it scrolls, by setting the variables +@code{scroll-up-aggressively} and @code{scroll-down-aggressively}. +The value of @code{scroll-up-aggressively} should be either +@code{nil}, or a fraction @var{f} between 0 and 1. A fraction +specifies where on the screen to put point when scrolling upward. +More precisely, when a window scrolls up because point is above the +window start, the new start position is chosen to put point @var{f} +part of the window height from the top. The larger @var{f}, the more +aggressive the scrolling. + + @code{nil}, which is the default, scrolls to put point at the center. +So it is equivalent to .5. + + Likewise, @code{scroll-down-aggressively} is used for scrolling +down. The value, @var{f}, specifies how far point should be placed +from the bottom of the window; thus, as with +@code{scroll-up-aggressively}, a larger value is more aggressive. @vindex scroll-margin The variable @code{scroll-margin} restricts how close point can come @@ -161,8 +562,18 @@ window, Emacs recenters the window. By default, @code{scroll-margin} is @cindex horizontal scrolling @dfn{Horizontal scrolling} means shifting all the lines sideways -within a window---so that some of the text near the left margin -is not displayed at all. +within a window---so that some of the text near the left margin is not +displayed at all. Emacs does this automatically in any window that +uses line truncation rather than continuation: whenever point moves +off the left or right edge of the screen, Emacs scrolls the buffer +horizontally to make point visible. + + When a window has been scrolled horizontally, text lines are truncated +rather than continued (@pxref{Continuation Lines}), with a @samp{$} +appearing in the first column when there is text truncated to the left, +and in the last column when there is text truncated to the right. + + You can use these commands to do explicit horizontal scrolling. @table @kbd @item C-x < @@ -171,11 +582,6 @@ Scroll text in current window to the left (@code{scroll-left}). Scroll to the right (@code{scroll-right}). @end table - When a window has been scrolled horizontally, text lines are truncated -rather than continued (@pxref{Continuation Lines}), with a @samp{$} -appearing in the first column when there is text truncated to the left, -and in the last column when there is text truncated to the right. - @kindex C-x < @kindex C-x > @findex scroll-left @@ -193,17 +599,111 @@ attempting to do so has no effect. This means that you don't have to calculate the argument precisely for @w{@kbd{C-x >}}; any sufficiently large argument will restore the normal display. -@cindex horizontal scrolling -@vindex automatic-hscrolling - Emacs automatically scrolls a window horizontally whenever that is -necessary to keep point visible and not too far from the left or right -edge. If you don't want this, customize the variable -@code{automatic-hscrolling} and set it to nil. + If you scroll a window horizontally by hand, that sets a lower bound +for automatic horizontal scrolling. Automatic scrolling will continue +to scroll the window, but never farther to the right than the amount +you previously set by @code{scroll-left}. + +@vindex hscroll-margin + The value of the variable @code{hscroll-margin} controls how close +to the window's edges point is allowed to get before the window will +be automatically scrolled. It is measured in columns. If the value +is 5, then moving point within 5 columns of the edge causes horizontal +scrolling away from that edge. + +@vindex hscroll-step + The variable @code{hscroll-step} determines how many columns to +scroll the window when point gets too close to the edge. If it's +zero, horizontal scrolling centers point horizontally within the +window. If it's a positive integer, it specifies the number of +columns to scroll by. If it's a floating-point number, it specifies +the fraction of the window's width to scroll by. The default is zero. + +@vindex auto-hscroll-mode + To disable automatic horizontal scrolling, set the variable +@code{auto-hscroll-mode} to @code{nil}. + +@node Fringes +@section Window Fringes +@cindex fringes + + On a graphical display, each Emacs window normally has narrow +@dfn{fringes} on the left and right edges. The fringes display +indications about the text in the window. + + The most common use of the fringes is to indicate a continuation +line, when one line of text is split into multiple lines on the +screen. The left fringe shows a curving arrow for each screen line +except the first, indicating that ``this is not the real beginning.'' +The right fringe shows a curving arrow for each screen line except the +last, indicating that ``this is not the real end.'' + + The fringes indicate line truncation with short horizontal arrows +meaning ``there's more text on this line which is scrolled +horizontally out of view;'' clicking the mouse on one of the arrows +scrolls the display horizontally in the direction of the arrow. The +fringes also indicate other things such as empty lines, or where a +program you are debugging is executing (@pxref{Debuggers}). + +@findex set-fringe-style +@findex fringe-mode + You can enable and disable the fringes for all frames using +@kbd{M-x fringe-mode}. To enable and disable the fringes +for the selected frame, use @kbd{M-x set-fringe-style}. + +@node Useless Whitespace +@section Useless Whitespace + +@cindex trailing whitespace +@cindex whitespace, trailing +@vindex show-trailing-whitespace + It is easy to leave unnecessary spaces at the end of a line, or +empty lines at the end of a file, without realizing it. In most +cases, this @dfn{trailing whitespace} has no effect, but there are +special circumstances where it matters. + + You can make trailing whitespace at the end of a line visible on the +screen by setting the buffer-local variable +@code{show-trailing-whitespace} to @code{t}. Then Emacs displays +trailing whitespace in the face @code{trailing-whitespace}. + + This feature does not apply when point is at the end of the line +containing the whitespace. Strictly speaking, that is ``trailing +whitespace'' nonetheless, but displaying it specially in that case +looks ugly while you are typing in new text. In this special case, +the location of point is enough to show you that the spaces are +present. + +@findex delete-trailing-whitespace + To delete all trailing whitespace within the current buffer's +accessible portion (@pxref{Narrowing}), type @kbd{M-x +delete-trailing-whitespace @key{RET}}. (This command does not remove +the form-feed characters.) + +@vindex indicate-unused-lines +@vindex default-indicate-empty-lines +@cindex unused lines +@cindex fringes, and unused line indication + Emacs can indicate unused lines at the end of the window with a +small image in the left fringe (@pxref{Fringes}). The image appears +for window lines that do not correspond to any buffer text. Blank +lines at the end of the buffer then stand out because they do not have +this image in the fringe. + + To enable this feature, set the buffer-local variable +@code{indicate-unused-lines} to a non-@code{nil} value. The default +value of this variable is controlled by the variable +@code{default-indicate-unused-lines}; by setting that variable, you +can enable or disable this feature for all new buffers. (This feature +currently doesn't work on character terminals.) @node Follow Mode @section Follow Mode @cindex Follow mode @cindex mode, Follow +@findex follow-mode +@cindex windows, synchronizing +@cindex synchronizing windows @dfn{Follow mode} is a minor mode that makes two windows showing the same buffer scroll as one tall ``virtual window.'' To use Follow mode, @@ -212,10 +712,16 @@ windows using @kbd{C-x 3}, and then type @kbd{M-x follow-mode}. From then on, you can edit the buffer in either of the two windows, or scroll either one; the other window follows it. + In Follow mode, if you move point outside the portion visible in one +window and into the portion visible in the other window, that selects +the other window---again, treating the two as if they were parts of +one large window. + To turn off Follow mode, type @kbd{M-x follow-mode} a second time. @node Selective Display @section Selective Display +@cindex selective display @findex set-selective-display @kindex C-x $ @@ -250,24 +756,55 @@ hidden lines. This variable becomes local automatically when set. @node Optional Mode Line @section Optional Mode Line Features -@cindex Line Number mode -@cindex mode, Line Number +@cindex buffer size display +@cindex display of buffer size +@findex size-indication-mode + The buffer percentage @var{pos} indicates the percentage of the +buffer above the top of the window. You can additionally display the +size of the buffer by typing @kbd{M-x size-indication-mode} to turn on +Size Indication mode. The size will be displayed immediately +following the buffer percentage like this: + +@example +@var{POS} of @var{SIZE} +@end example + +@noindent +Here @var{SIZE} is the human readable representation of the number of +characters in the buffer, which means that @samp{k} for 10^3, @samp{M} +for 10^6, @samp{G} for 10^9, etc., are used to abbreviate. + +@cindex narrowing, and buffer size display + If you have narrowed the buffer (@pxref{Narrowing}), the size of the +accessible part of the buffer is shown. + +@cindex line number display +@cindex display of line number @findex line-number-mode The current line number of point appears in the mode line when Line Number mode is enabled. Use the command @kbd{M-x line-number-mode} to turn this mode on and off; normally it is on. The line number appears -before the buffer percentage @var{pos}, with the letter @samp{L} to +after the buffer percentage @var{pos}, with the letter @samp{L} to indicate what it is. @xref{Minor Modes}, for more information about minor modes and about how to use this command. +@cindex narrowing, and line number display + If you have narrowed the buffer (@pxref{Narrowing}), the displayed +line number is relative to the accessible portion of the buffer. + @vindex line-number-display-limit -@cindex line number display, removing the limit If the buffer is very large (larger than the value of @code{line-number-display-limit}), then the line number doesn't appear. Emacs doesn't compute the line number when the buffer is large, because -that would be too slow. Set it to @code{nil} to remove the limit. If -you have narrowed the buffer (@pxref{Narrowing}), the displayed line -number is relative to the accessible portion of the buffer. +that would be too slow. Set it to @code{nil} to remove the limit. + +@vindex line-number-display-limit-width + Line-number computation can also be slow if the lines in the buffer +are too long. For this reason, Emacs normally doesn't display line +numbers if the average width, in characters, of lines near point is +larger than the value of the variable +@code{line-number-display-limit-width}. The default value is 200 +characters. @cindex Column Number mode @cindex mode, Column Number @@ -300,50 +837,93 @@ to @code{t}. @cindex mail (on mode line) @vindex display-time-use-mail-icon @vindex display-time-mail-face +@vindex display-time-mail-file +@vindex display-time-mail-directory The word @samp{Mail} appears after the load level if there is mail for you that you have not read yet. On a graphical display you can use an icon instead of @samp{Mail} by customizing @code{display-time-use-mail-icon}; this may save some space on the mode line. You can customize @code{display-time-mail-face} to make the mail -indicator prominent. +indicator prominent. Use @code{display-time-mail-file} to specify +the mail file to check, or set @code{display-time-mail-directory} +to specify the directory to check for incoming mail (any nonempty regular +file in the directory is considered as ``newly arrived mail''). + +@cindex mode line, 3D appearance +@cindex attributes of mode line, changing +@cindex non-integral number of lines in a window + By default, the mode line is drawn on graphics displays with +3D-style highlighting, like that of a button when it is not being +pressed. If you don't like this effect, you can disable the 3D +highlighting of the mode line, by customizing the attributes of the +@code{mode-line} face in your @file{.emacs} init file, like this: + +@example +(set-face-attribute 'mode-line nil :box nil) +@end example + +@noindent +Alternatively, you can turn off the box attribute in your +@file{.Xdefaults} file: + +@example +Emacs.mode-line.AttributeBox: off +@end example + +@cindex non-selected windows, mode line appearance + By default, the mode line of nonselected windows is displayed in a +different face, called @code{mode-line-inactive}. Only the selected +window is displayed in the @code{mode-line} face. This helps show +which window is selected. When the minibuffer is selected, since +it has no mode line, the window from which you activated the minibuffer +has its mode line displayed using @code{mode-line}; as a result, +ordinary entry to the minibuffer does not change any mode lines. + +@vindex mode-line-in-non-selected-windows + You can disable use of @code{mode-line-inactive} by setting variable +@code{mode-line-in-non-selected-windows} to @code{nil}; then all mode +lines are displayed in the @code{mode-line} face. @node Text Display @section How Text Is Displayed @cindex characters (in text) - ASCII printing characters (octal codes 040 through 0176) in Emacs -buffers are displayed with their graphics. So are non-ASCII multibyte + @acronym{ASCII} printing characters (octal codes 040 through 0176) in Emacs +buffers are displayed with their graphics, as are non-ASCII multibyte printing characters (octal codes above 0400). - Some ASCII control characters are displayed in special ways. The + Some @acronym{ASCII} control characters are displayed in special ways. The newline character (octal code 012) is displayed by starting a new line. The tab character (octal code 011) is displayed by moving to the next tab stop column (normally every 8 columns). - Other ASCII control characters are normally displayed as a caret + Other @acronym{ASCII} control characters are normally displayed as a caret (@samp{^}) followed by the non-control version of the character; thus, control-A is displayed as @samp{^A}. - Non-ASCII characters 0200 through 0377 are displayed with octal escape -sequences; thus, character code 0243 (octal) is displayed as -@samp{\243}. However, if you enable European display, most of these -characters become non-ASCII printing characters, and are displayed using -their graphics (assuming your terminal supports them). -@xref{Single-Byte Character Support}. + Non-@acronym{ASCII} characters 0200 through 0237 (octal) are displayed with +octal escape sequences; thus, character code 0230 (octal) is displayed +as @samp{\230}. The display of character codes 0240 through 0377 +(octal) may be either as escape sequences or as graphics. They do not +normally occur in multibyte buffers, but if they do, they are displayed +as Latin-1 graphics. In unibyte mode, if you enable European display +they are displayed using their graphics (assuming your terminal supports +them), otherwise as escape sequences. @xref{Single-Byte Character +Support}. -@node Display Vars -@section Variables Controlling Display +@node Display Custom +@section Customization of Display This section contains information for customization only. Beginning users should skip it. @vindex mode-line-inverse-video - The variable @code{mode-line-inverse-video} controls whether the mode -line is displayed in inverse video (assuming the terminal supports it); -@code{nil} means don't do so. @xref{Mode Line}. If you specify the -foreground color for the @code{modeline} face, and -@code{mode-line-inverse-video} is non-@code{nil}, then the default -background color for that face is the usual foreground color. + The variable @code{mode-line-inverse-video} is an obsolete way of +controlling whether the mode line is displayed in inverse video; the +preferred way of doing this is to change the @code{mode-line} face. +@xref{Mode Line}. However, if @code{mode-line-inverse-video} has a +value of @code{nil}, then the @code{mode-line} face will be ignored, +and mode-lines will be drawn using the default text face. @xref{Faces}. @vindex inverse-video @@ -373,7 +953,7 @@ keys; its value is the number of seconds of pause required to cause echoing to start, or zero meaning don't echo at all. @xref{Echo Area}. @vindex ctl-arrow - If the variable @code{ctl-arrow} is @code{nil}, control characters in + If the variable @code{ctl-arrow} is @code{nil}, all control characters in the buffer are displayed with octal escape sequences, except for newline and tab. Altering the value of @code{ctl-arrow} makes it local to the current buffer; until that time, the default value is in effect. The @@ -410,17 +990,76 @@ windows, see @ref{Split Window}. See also @ref{Display,, Display, elisp, The Emacs Lisp Reference Manual}. @vindex baud-rate - The variable @code{baud-rate} holds the output speed of the terminal, -as far as Emacs knows. Setting this variable does not change the speed -of actual data transmission, but the value is used for calculations such -as padding. On terminals, it also affects decisions about whether to -scroll part of the screen or redraw it instead. + The variable @code{baud-rate} holds the output speed of the +terminal, as far as Emacs knows. Setting this variable does not +change the speed of actual data transmission, but the value is used +for calculations. On terminals, it affects padding, and decisions +about whether to scroll part of the screen or redraw it instead. +It also affects the behavior of incremental search. -On window-systems, @code{baud-rate} is only used to determine how -frequently to look for pending input during display updating. A higher -value of @code{baud-rate} means that check for pending input will be -done less frequently. + On window-systems, @code{baud-rate} is only used to determine how +frequently to look for pending input during display updating. A +higher value of @code{baud-rate} means that check for pending input +will be done less frequently. You can customize the way any particular character code is displayed by means of a display table. @xref{Display Tables,, Display Tables, elisp, The Emacs Lisp Reference Manual}. + +@cindex hourglass pointer display +@vindex hourglass-delay + On a window system, Emacs can optionally display the mouse pointer +in a special shape to say that Emacs is busy. To turn this feature on +or off, customize the group @code{cursor}. You can also control the +amount of time Emacs must remain busy before the busy indicator is +displayed, by setting the variable @code{hourglass-delay}. + +@findex tty-suppress-bold-inverse-default-colors + On some text-only terminals, bold face and inverse video together +result in text that is hard to read. Call the function +@code{tty-suppress-bold-inverse-default-colors} with a non-@code{nil} +argument to suppress the effect of bold-face in this case. + +@node Cursor Display +@section Displaying the Cursor + +@findex blink-cursor-mode +@vindex blink-cursor-alist +@cindex cursor, locating visually +@cindex cursor, blinking + You can customize the cursor's color, and whether it blinks, using +the @code{cursor} Custom group (@pxref{Easy Customization}). On +graphical terminals, the command @kbd{M-x blink-cursor-mode} enables +or disables the blinking of the cursor. (On text terminals, the +terminal itself blinks the cursor, and Emacs has no control over it.) +You can control how the cursor appears when it blinks off by setting +the variable @code{blink-cursor-alist}. + +@cindex cursor in non-selected windows +@vindex cursor-in-non-selected-windows + Normally, the cursor appears in non-selected windows in the ``off'' +state, with the same appearance as when the blinking cursor blinks +``off''. For a box cursor, this is a hollow box; for a bar cursor, +this is a thinner bar. To turn off cursors in non-selected windows, +customize the option @code{cursor-in-non-selected-windows} and assign +it a @code{nil} value. + +@vindex x-stretch-cursor +@cindex wide block cursor + On graphical terminals, Emacs can optionally draw the block cursor +as wide as the character under the cursor---for example, if the cursor +is on a tab character, it would cover the full width occupied by that +tab character. To enable this feature, set the variable +@code{x-stretch-cursor} to a non-@code{nil} value. + +@findex hl-line-mode +@findex global-hl-line-mode +@cindex highlight current line + If you find it hard to see the cursor, you might like HL Line mode, +a minor mode that highlights the line containing point. Use @kbd{M-x +hl-line-mode} to enable or disable it in the current buffer. @kbd{M-x +global-hl-line-mode} enables or disables the same mode globally. + +@ignore + arch-tag: 2219f910-2ff0-4521-b059-1bd231a536c4 +@end ignore