@c This is part of the Emacs manual.
-@c Copyright (C) 1985, 86, 87, 93, 94, 95, 1997, 2000 Free Software Foundation, Inc.
+@c Copyright (C) 1985, 86, 87, 93, 94, 95, 1997, 2000, 2001
+@c Free Software Foundation, Inc.
@c See file emacs.texi for copying conditions.
@node Display, Search, Registers, Top
@chapter Controlling the Display
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.
+* Trailing Whitespace:: Showing possibly-spurious trailing whitespace.
* Scrolling:: Moving text up and down in a window.
* Horizontal Scrolling:: Moving text left and right in a window.
* Follow Mode:: Follow mode lets two windows scroll as one.
* Cursor Display:: Features for displaying the cursor.
@end menu
+@node Faces
+@section Using Multiple Typefaces
+@cindex faces
+
+ When using Emacs with a window system, you can set up multiple
+styles of displaying characters. Each style is called a @dfn{face}.
+Each face can specify various attributes, such as the height, weight
+and slant of the characters, the foreground and background color, and
+underlining. But it does not have to specify all of them.
+
+ 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 default face,
+which embodies 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 X}). 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.
+
+ 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 standardly 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 mode lines. 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 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 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-nil.
+@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.
+
+@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
+ Comment and string fontification (or ``syntactic'' fontification)
+relies on analysis of the syntactic structure of the buffer text. For
+the purposes of speed, some modes including C mode and Lisp mode rely on
+a special convention: an open-parenthesis in the leftmost column always
+defines the @w{beginning} of a defun, and is thus always outside any string
+or comment. (@xref{Defuns}.) If you don't follow this convention,
+then Font Lock mode can misfontify the text after an open-parenthesis 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
+
+@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 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 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 Trailing Whitespace
+@section Trailing Whitespace
+
+@cindex trailing whitespace
+@cindex whitespace, trailing
+@vindex show-trailing-whitespace
+ It is easy to leave unnecessary spaces at the end of a line 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 visible on the screen by setting
+the variable @code{show-trailing-whitespace} to @code{t}. Then Emacs
+displays trailing whitespace in the face @code{trailing-whitespace}.
+
+ Trailing whitespace is defined as spaces or tabs at the end of a
+line. But trailing whitespace is not displayed specially if point is
+at the end of the line containing the whitespace. (Doing that looks
+ugly while you are typing in new text, and the location of point is
+enough in that case to show you that the spaces are present.)
+
+@vindex indicate-empty-lines
+@vindex default-indicate-empty-lines
+@cindex empty lines
+ Emacs can indicate empty lines at the end of the buffer with a
+special bitmap on the left fringe of the window. To enable this
+feature, set the buffer-local variable @code{indicate-empty-lines} to
+a non-@code{nil} value. The default value of this variable is
+controlled by the variable @code{default-indicate-empty-lines};
+by setting that variable, you can enable or disable this feature
+for all new buffers.
+
@node Scrolling
@section Scrolling
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 further to the right than the amount
+to scroll the window, but never farther to the right than the amount
you previously set by @code{scroll-left}.
@vindex automatic-hscrolling
@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,
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 $
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
by means of a display table. @xref{Display Tables,, Display Tables,
elisp, The Emacs Lisp Reference Manual}.
-@cindex busy-cursor display
-@vindex busy-cursor-delay
+@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{busy-cursor-delay}.
+displayed, by setting the variable @code{hourglass-delay}.
@node Cursor Display
@section Displaying the Cursor
@cindex cursor in non-selected windows
@vindex cursor-in-non-selected-windows
- Normally, the cursor in non-selected windows is shown as a hollow
-box. To turn off cursor display in non-selected windows, set the
-variable @code{cursor-in-non-selected-windows} to @code{nil}.
+ Normally, the cursor in non-selected windows is shown as a hollow box.
+To turn off cursor display in non-selected windows, customize the option
+@code{cursor-in-non-selected-windows} to assign it a @code{nil} value.