If this variable is @code{nil}, Emacs does not check for input during
redisplay, and redisplay cannot be preempted by input.
-@emph{Note} that this variable is only available if Emacs is built
-with support for sub-second timers.
+This variable is only obeyed on graphical terminals. For
+text terminals, see @ref{Terminal Output}.
@end defvar
@defvar redisplay-dont-pause
regardless of whether input is available.
@end defvar
-@findex sit-for
- You can request a display update, but only if no input is pending,
-with @code{(sit-for 0)}. To force a display update even when input is
-pending, use @code{(sit-for -1)}.
+@defun redisplay &optional force
+This function performs an immediate redisplay provided there are no
+pending input events. This is equivalent to @code{(sit-for 0)}.
+
+If the optional argument @var{force} is non-@code{nil}, it forces an
+immediate and complete redisplay even if input is available.
+
+Returns @code{t} if redisplay was performed, or @code{nil} otherwise.
+@end defun
@node Truncation
@section Truncation
@cindex @samp{$} in display
@cindex @samp{\} in display
- When a line of text extends beyond the right edge of a window, the
-line can either be continued on the next screen line, or truncated to
-one screen line. The additional screen lines used to display a long
-text line are called @dfn{continuation} lines. Normally, tiny arrow images
-are displayed in the window fringes to indicate truncated and continued
-lines (*note Fringes).
-
- On a text terminal, a `$' in the rightmost column of the window
-indicates truncation; a `\' on the rightmost column indicates a
-continued line that "wraps" onto the next line. (The display table can
-specify alternative indicators; see *Note Display Tables.)
-
- On a graphical display, the @samp{$} and @samp{\} indicators are
-replaced with arrow images displayed in the window fringes
-(@pxref{Fringes}).
-
- Note that continuation is different from filling; continuation happens
-on the screen only, not in the buffer contents, and it breaks a line
-precisely at the right margin, not at a word boundary. @xref{Filling}.
+ When a line of text extends beyond the right edge of a window, Emacs
+can @dfn{continue} the line (make it ``wrap'' to the next screen
+line), or @dfn{truncate} the line (limit it to one screen line). The
+additional screen lines used to display a long text line are called
+@dfn{continuation} lines. Continuation is not the same as filling;
+continuation happens on the screen only, not in the buffer contents,
+and it breaks a line precisely at the right margin, not at a word
+boundary. @xref{Filling}.
+
+ On a graphical display, tiny arrow images in the window fringes
+indicate truncated and continued lines (@pxref{Fringes}). On a text
+terminal, a @samp{$} in the rightmost column of the window indicates
+truncation; a @samp{\} on the rightmost column indicates a line that
+``wraps.'' (The display table can specify alternate characters to use
+for this; @pxref{Display Tables}).
@defopt truncate-lines
This buffer-local variable controls how Emacs displays lines that extend
@end defun
@defun message-box format-string &rest arguments
+@anchor{message-box}
This function displays a message like @code{message}, but uses a dialog
box (or a pop-up menu) whenever that is possible. If it is impossible
to use a dialog box or pop-up menu, because the terminal does not
This is the only valid way to change the endpoints of an overlay. Do
not try modifying the markers in the overlay by hand, as that fails to
update other vital data structures and can cause some overlays to be
-``lost''.
+``lost.''
@end defun
@defun remove-overlays &optional start end name value
The effect of using a face is determined by a fixed set of @dfn{face
attributes}. This table lists all the face attributes, and what they
-mean. Note that in general, more than one face can be specified for a
-given piece of text; when that happens, the attributes of all the faces
-are merged to specify how to display the text. @xref{Displaying Faces}.
+mean. You can specify more than one face for a given piece of text;
+Emacs merges the attributes of all the faces to determine how to
+display the text. @xref{Displaying Faces}.
Any attribute in a face can have the value @code{unspecified}. This
means the face doesn't specify that attribute. In face merging, when
A non-@code{nil} value specifies an italic font.
@end table
- For compatibility, you can still set these ``attributes'', even
+ For compatibility, you can still set these ``attributes,'' even
though they are not real face attributes. Here is what that does:
@table @code
@node Attribute Functions
@subsection Face Attribute Functions
- You can modify the attributes of an existing face with the following
-functions. If you specify @var{frame}, they affect just that frame;
-otherwise, they affect all frames as well as the defaults that apply to
-new frames.
+ This section describes the functions for accessing and modifying the
+attributes of an existing face.
@defun set-face-attribute face frame &rest arguments
-This function sets one or more attributes of face @var{face}
-for frame @var{frame}. If @var{frame} is @code{nil}, it sets
-the attribute for all frames, and the defaults for new frames.
+This function sets one or more attributes of face @var{face} for frame
+@var{frame}. The attributes you specify this way override whatever
+the @code{defface} says.
The extra arguments @var{arguments} specify the attributes to set, and
the values for them. They should consist of alternating attribute names
@noindent
sets the attributes @code{:width}, @code{:weight} and @code{:underline}
to the corresponding values.
+
+If @var{frame} is @code{t}, this function sets the default attributes
+for new frames. Default attribute values specified this way override
+the @code{defface} for newly created frames.
+
+If @var{frame} is @code{nil}, this function sets the attributes for
+all existing frames, and the default for new frames.
@end defun
@defun face-attribute face attribute &optional frame inherit
@var{face} on @var{frame}. If @var{frame} is @code{nil},
that means the selected frame (@pxref{Input Focus}).
-If @var{frame} is @code{t}, the value is the default for
-@var{face} for new frames.
+If @var{frame} is @code{t}, this returns whatever new-frames default
+value you previously specified with @code{set-face-attribute} for the
+@var{attribute} attribute of @var{face}. If you have not specified
+one, it returns @code{nil}.
If @var{inherit} is @code{nil}, only attributes directly defined by
@var{face} are considered, so the return value may be
The functions above did not exist before Emacs 21. For compatibility
with older Emacs versions, you can use the following functions to set
and examine the face attributes which existed in those versions.
+They use values of @code{t} and @code{nil} for @var{frame}
+just like @code{set-face-attribute} and @code{face-attribute}.
@defun set-face-foreground face color &optional frame
@defunx set-face-background face color &optional frame
@end defun
These functions examine the attributes of a face. If you don't
-specify @var{frame}, they refer to the default data for new frames.
-They return the symbol @code{unspecified} if the face doesn't define any
-value for that attribute.
+specify @var{frame}, they refer to the selected frame; @code{t} refers
+to the default data for new frames. They return the symbol
+@code{unspecified} if the face doesn't define any value for that
+attribute.
@defun face-foreground face &optional frame inherit
@defunx face-background face &optional frame inherit
that there is text above the screen, and a down-arrow to show
there is text below the screen.
-There are four kinds of basic values:
+There are three kinds of basic values:
@table @asis
@item @code{nil}
-Don't display the icons.
+Don't display any of these fringe icons.
@item @code{left}
-Display them in the left fringe.
+Display the angle icons and arrows in the left fringe.
@item @code{right}
-Display them in the right fringe.
-@item @var{anything-else}
-Display the icon at the top of the window top in the left fringe, and other
-in the right fringe.
+Display the angle icons and arrows in the right fringe.
+@item any non-alist
+Display the angle icons in the left fringe
+and don't display the arrows.
@end table
-If value is a cons @code{(@var{angles} . @var{arrows})}, @var{angles}
-controls the angle icons, and @var{arrows} controls the arrows. Both
-@var{angles} and @var{arrows} work according to the table above.
-Thus, @code{(t . right)} places the top angle icon in the left
-fringe, the bottom angle icon in the right fringe, and both arrows in
-the right fringe.
+Otherwise the value should be an alist that specifies which fringe
+indicators to display and where. Each element of the alist should
+have the form @code{(@var{indicator} . @var{position})}. Here,
+@var{indicator} is one of @code{top}, @code{bottom}, @code{up},
+@code{down}, and @code{t} (which covers all the icons not yet
+specified), while @var{position} is one of @code{left}, @code{right}
+and @code{nil}.
+
+For example, @code{((top . left) (t . right))} places the top angle
+bitmap in left fringe, and the bottom angle bitmap as well as both
+arrow bitmaps in right fringe. To show the angle bitmaps in the left
+fringe, and no arrow bitmaps, use @code{((top . left) (bottom . left))}.
@end defvar
@defvar default-indicate-buffer-boundaries
descriptor, then use it as a display specifier in the @code{display}
property of text that is displayed (@pxref{Display Property}).
+ Emacs is usually able to display images when it is run on a
+graphical terminal. Images cannot be displayed in a text terminal, on
+certain graphical terminals that lack the support for this, or if
+Emacs is compiled without image support. You can use the function
+@code{display-images-p} to determine if images can in principle be
+displayed (@pxref{Display Feature Testing}).
+
Emacs can display a number of different image formats; some of them
are supported only if particular support libraries are installed on
your machine. In some environments, Emacs can load image
@end ifnottex
@item disabled
-Specifies transforming the image so that it looks ``disabled''.
+Specifies transforming the image so that it looks ``disabled.''
@end table
@item :mask @var{mask}
properties or overlays) to a region of text in an Emacs buffer. These
properties are called @dfn{button properties}.
- One of the these properties (@code{action}) is a function, which will
+ One of these properties (@code{action}) is a function, which will
be called when the user invokes it using the keyboard or the mouse.
The invoked function may then examine the button and use its other
properties as desired.
@subsection Abstract Display Example
Here is a simple example using functions of the ewoc package to
-implement a ``color components display'', an area in a buffer that
+implement a ``color components display,'' an area in a buffer that
represents a vector of three integers (itself representing a 24-bit RGB
value) in various ways.
The ordinary elements of the display table are indexed by character
codes; the element at index @var{c} says how to display the character
-code @var{c}. The value should be @code{nil} or a vector of glyph
-values (@pxref{Glyphs}). If an element is @code{nil}, it says to
-display that character according to the usual display conventions
+code @var{c}. The value should be @code{nil} or a vector of the
+glyphs to be output (@pxref{Glyphs}). @code{nil} says to display the
+character @var{c} according to the usual display conventions
(@pxref{Usual Display}).
- If you use the display table to change the display of newline
-characters, the whole buffer will be displayed as one long ``line.''
+ @strong{Warning:} if you use the display table to change the display
+of newline characters, the whole buffer will be displayed as one long
+``line.''
The display table also has six ``extra slots'' which serve special
purposes. Here is a table of their meanings; @code{nil} in any slot
A @dfn{glyph} is a generalization of a character; it stands for an
image that takes up a single character position on the screen. Glyphs
are represented in Lisp as integers, just as characters are. Normally
-Emacs finds glyphs in the display table (@pxref{Display Tables}).
-
- A glyph can be @dfn{simple} or it can be defined by the @dfn{glyph
-table}. A simple glyph is just a way of specifying a character and a
-face to output it in. The glyph code for a simple glyph, mod 524288,
-is the character to output, and the glyph code divided by 524288
-specifies the face number (@pxref{Face Functions}) to use while
-outputting it. (524288 is
+glyph come from vectors in the display table (@pxref{Display Tables}).
+
+ A glyph code can be @dfn{simple} or it can be defined by the
+@dfn{glyph table}. A simple glyph code is just a way of specifying a
+character and a face to output it in. When a glyph code is simple,
+the code, mod 524288, is the character to output, and the code divided
+by 524288 specifies the face number (@pxref{Face Functions}) to use
+while outputting it. (524288 is
@ifnottex
2**19.)
@end ifnottex
@xref{Faces}.
On character terminals, you can set up a @dfn{glyph table} to define
-the meaning of glyph codes. The glyph codes is the value of the
-variable @code{glyph-table}.
+the meaning of glyph codes.
@defvar glyph-table
-The value of this variable is the current glyph table. It should be a
-vector; the @var{g}th element defines glyph code @var{g}.
+The value of this variable is the current glyph table. It should be
+@code{nil} or a vector whose @var{g}th element defines glyph code
+@var{g}.
If a glyph code is greater than or equal to the length of the glyph
-table, that code is automatically simple. If the value of
-@code{glyph-table} is @code{nil} instead of a vector, then all glyphs
-are simple. The glyph table is not used on graphical displays, only
-on character terminals. On graphical displays, all glyphs are simple.
+table, that code is automatically simple. If @code{glyph-table} is
+@code{nil} then all glyph codes are simple.
+
+The glyph table is used only on character terminals. On graphical
+displays, all glyph codes are simple.
@end defvar
- Here are the possible types of elements in the glyph table:
+ Here are the meaningful types of elements in the glyph table:
@table @asis
@item @var{string}
Send the characters in @var{string} to the terminal to output
-this glyph. This alternative is available on character terminals,
-but not on graphical displays.
+this glyph code.
@item @var{integer}
Define this glyph code as an alias for glyph code @var{integer}. You
-can use an alias to specify a face code for the glyph and use a small
-number as its code.
+can use such an alias to define a small-numbered glyph code which
+specifies a face.
@item @code{nil}
-This glyph is simple.
+This glyph code is simple.
@end table
@defun create-glyph string
@section Window Systems
Emacs works with several window systems, most notably the X Window
-System. Both Emacs and X use the term ``window'', but use it
+System. Both Emacs and X use the term ``window,'' but use it
differently. An Emacs frame is a single window as far as X is
concerned; the individual Emacs windows are not known to X at all.