[Emacs-diffs] Changes to emacs/man/display.texi [gnus-5_10-branch]

[Miles Bader]

Index: emacs/man/display.texi
diff -c /dev/null emacs/man/display.texi:1.73.2.1
*** /dev/null   Sat Sep  4 12:02:55 2004
--- emacs/man/display.texi      Sat Sep  4 12:01:14 2004
***************
*** 0 ****
--- 1,1066 ----
+ @c This is part of the Emacs manual.
+ @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
+ 
+   Since only part of a large buffer fits in the window, Emacs tries to
+ show a part that is likely to be interesting.  Display-control commands
+ 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 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
+ address@hidden).  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 address@hidden; 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, The Emacs Lisp Reference Manual}, 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
+ 
+   If a buffer contains text that is too large to fit entirely within a
+ window that is displaying the buffer, Emacs shows a contiguous portion of
+ the text.  The portion shown always contains point.
+ 
+ @cindex scrolling
+   @dfn{Scrolling} means moving text up or down in the window so that
+ different parts of the text are visible.  Scrolling forward means that text
+ moves up, and new text appears at the bottom.  Scrolling backward moves
+ text down and new text appears at the top.
+ 
+   Scrolling happens automatically if you move point past the bottom or top
+ of the window.  You can also explicitly request scrolling with the commands
+ in this section.
+ 
+ @table @kbd
+ @item C-l
+ Clear screen and redisplay, scrolling the selected window to center
+ 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}).
+ @item C-M-l
+ Scroll heuristically to bring useful information onto the screen
+ (@code{reposition-window}).
+ @end table
+ 
+ @kindex C-l
+ @findex recenter
+   The most basic scrolling command is @kbd{C-l} (@code{recenter}) with
+ no argument.  It clears the entire screen and redisplays all windows.
+ In addition, it scrolls the selected window so that point is halfway
+ down from the top of the window.
+ 
+ @kindex C-v
+ @kindex M-v
+ @kindex NEXT
+ @kindex PRIOR
+ @kindex PAGEDOWN
+ @kindex PAGEUP
+ @findex scroll-up
+ @findex scroll-down
+ @vindex next-screen-context-lines
+   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
+ same screen line.  To enable this behavior, set the variable
+ @code{scroll-preserve-screen-position} to a address@hidden value.  This
+ mode is convenient for browsing through a file by scrolling by
+ screenfuls; if you come back to the screen where you started, point goes
+ back to the line where it started.  However, this mode is inconvenient
+ when you move to the next screen in order to move point to the text
+ there.
+ 
+   Another way to do scrolling is with @kbd{C-l} with a numeric argument.
+ @kbd{C-l} does not clear the screen when given an argument; it only scrolls
+ the selected window.  With a positive argument @var{n}, it repositions text
+ to put point @var{n} lines down from the top.  An argument of zero puts
+ 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.  @kbd{C-u C-l} scrolls to put
+ point at the center (vertically) of the selected window.
+ 
+ @kindex C-M-l
+ @findex reposition-window
+   The @kbd{C-M-l} command (@code{reposition-window}) scrolls the current
+ window heuristically in a way designed to get useful information onto
+ 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 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
+   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
+ to the top or bottom of a window.  Its value is a number of screen
+ lines; if point comes within that many lines of the top or bottom of the
+ window, Emacs recenters the window.  By default, @code{scroll-margin} is
+ 0.
+ 
+ @node Horizontal Scrolling
+ @section Horizontal Scrolling
+ @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.  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 <
+ Scroll text in current window to the left (@code{scroll-left}).
+ @item C-x >
+ Scroll to the right (@code{scroll-right}).
+ @end table
+ 
+ @kindex C-x <
+ @kindex C-x >
+ @findex scroll-left
+ @findex scroll-right
+   The command @kbd{C-x <} (@code{scroll-left}) scrolls the selected
+ window to the left by @var{n} columns with argument @var{n}.  This moves
+ part of the beginning of each line off the left edge of the window.
+ With no argument, it scrolls by almost the full width of the window (two
+ columns less, to be precise).
+ 
+   @kbd{C-x >} (@code{scroll-right}) scrolls similarly to the right.  The
+ window cannot be scrolled any farther to the right once it is displayed
+ normally (with each line starting at the window's left margin);
+ attempting to do so has no effect.  This means that you don't have to
+ calculate the argument precisely for @address@hidden >}}; any sufficiently 
large
+ argument will restore the normal display.
+ 
+   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 address@hidden 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,
+ go to a frame with just one window, split it into two side-by-side
+ 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 $
+ 
+   Emacs has the ability to hide lines indented more than a certain number
+ of columns (you specify how many columns).  You can use this to get an
+ overview of a part of a program.
+ 
+   To hide lines, type @kbd{C-x $} (@code{set-selective-display}) with a
+ numeric argument @var{n}.  Then lines with at least @var{n} columns of
+ indentation disappear from the screen.  The only indication of their
+ presence is that three dots (@address@hidden) appear at the end of each
+ visible line that is followed by one or more hidden ones.
+ 
+   The commands @kbd{C-n} and @kbd{C-p} move across the hidden lines as
+ if they were not there.
+ 
+   The hidden lines are still present in the buffer, and most editing
+ commands see them as usual, so you may find point in the middle of the
+ hidden text.  When this happens, the cursor appears at the end of the
+ previous line, after the three dots.  If point is at the end of the
+ visible line, before the newline that ends it, the cursor appears before
+ the three dots.
+ 
+   To make all lines visible again, type @kbd{C-x $} with no argument.
+ 
+ @vindex selective-display-ellipses
+   If you set the variable @code{selective-display-ellipses} to
+ @code{nil}, the three dots do not appear at the end of a line that
+ precedes hidden lines.  Then there is no visible indication of the
+ hidden lines.  This variable becomes local automatically when set.
+ 
+ @node Optional Mode Line
+ @section Optional Mode Line Features
+ 
+ @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
+ 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
+   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.
+ 
+ @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
+ @findex column-number-mode
+   You can also display the current column number by turning on Column
+ Number mode.  It displays the current column number preceded by the
+ letter @samp{C}.  Type @kbd{M-x column-number-mode} to toggle this mode.
+ 
+ @findex display-time
+ @cindex time (on mode line)
+   Emacs can optionally display the time and system load in all mode
+ lines.  To enable this feature, type @kbd{M-x display-time} or customize
+ the option @code{display-time-mode}.  The information added to the mode
+ line usually appears after the buffer name, before the mode names and
+ their parentheses.  It looks like this:
+ 
+ @example
+ @var{hh}:@var{mm}pm @var{l.ll}
+ @end example
+ 
+ @noindent
+ @vindex display-time-24hr-format
+ Here @var{hh} and @var{mm} are the hour and minute, followed always by
+ @samp{am} or @samp{pm}.  @var{l.ll} is the average number of running
+ processes in the whole system recently.  (Some fields may be missing if
+ your operating system cannot support them.)  If you prefer time display
+ in 24-hour format, set the variable @code{display-time-24hr-format}
+ 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.  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)
+ 
+   @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 @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 @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}.
+ 
+   address@hidden 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 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} 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
+   If the variable @code{inverse-video} is address@hidden, Emacs attempts
+ to invert all the lines of the display from what they normally are.
+ 
+ @vindex visible-bell
+   If the variable @code{visible-bell} is address@hidden, Emacs attempts
+ to make the whole screen blink when it would normally make an audible bell
+ sound.  This variable has no effect if your terminal does not have a way
+ to make the screen address@hidden
+ 
+ @vindex no-redraw-on-reenter
+   When you reenter Emacs after suspending, Emacs normally clears the
+ screen and redraws the entire display.  On some terminals with more than
+ one page of memory, it is possible to arrange the termcap entry so that
+ the @samp{ti} and @samp{te} strings (output to the terminal when Emacs
+ is entered and exited, respectively) switch between pages of memory so
+ as to use one page for Emacs and another page for other output.  Then
+ you might want to set the variable @code{no-redraw-on-reenter}
+ address@hidden; this tells Emacs to assume, when resumed, that the
+ screen page it is using still contains what Emacs last wrote there.
+ 
+ @vindex echo-keystrokes
+   The variable @code{echo-keystrokes} controls the echoing of multi-character
+ 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}, 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
+ default is initially @code{t}.  @xref{Display Tables,, Display Tables,
+ elisp, The Emacs Lisp Reference Manual}.
+ 
+ @vindex tab-width
+   Normally, a tab character in the buffer is displayed as whitespace which
+ extends to the next display tab stop position, and display tab stops come
+ at intervals equal to eight spaces.  The number of spaces per tab is
+ controlled by the variable @code{tab-width}, which is made local by
+ changing it, just like @code{ctl-arrow}.  Note that how the tab character
+ in the buffer is displayed has nothing to do with the definition of
+ @key{TAB} as a command.  The variable @code{tab-width} must have an
+ integer value between 1 and 1000, inclusive.
+ 
+ @c @vindex truncate-lines  @c No index entry here, because we have one
+ @c in the continuation section.
+   If the variable @code{truncate-lines} is address@hidden, then each
+ line of text gets just one screen line for display; if the text line is
+ too long, display shows only the part that fits.  If
+ @code{truncate-lines} is @code{nil}, then long text lines display as
+ more than one screen line, enough to show the whole text of the line.
+ @xref{Continuation Lines}.  Altering the value of @code{truncate-lines}
+ makes it local to the current buffer; until that time, the default value
+ is in effect.  The default is initially @code{nil}.
+ 
+ @c @vindex truncate-partial-width-windows  @c Idx entry is in Split Windows.
+   If the variable @code{truncate-partial-width-windows} is
+ address@hidden, it forces truncation rather than continuation in any
+ window less than the full width of the screen or frame, regardless of
+ the value of @code{truncate-lines}.  For information about side-by-side
+ 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.  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.
+ 
+   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 address@hidden
+ 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 address@hidden 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