@c -*-texinfo-*-
@c This is part of the XEmacs Lisp Reference Manual.
@c Copyright (C) 1990, 1991, 1992, 1993 Free Software Foundation, Inc. 
@c See the file lispref.texi for copying conditions.
@setfilename ../../info/display.info
@node Display, Processes, Annotations, Top
@chapter Emacs Display

  This chapter describes a number of other features related to the display
that XEmacs presents to the user.

@menu
* Refresh Screen::      Clearing the screen and redrawing everything on it.
* Truncation::          Folding or wrapping long text lines.
* The Echo Area::       Where messages are displayed.
* Selective Display::   Hiding part of the buffer text.
* Overlay Arrow::       Display of an arrow to indicate position.
* Temporary Displays::  Displays that go away automatically.
* Blinking::            How XEmacs shows the matching open parenthesis.
* Usual Display::	The usual conventions for displaying nonprinting chars.
* Display Tables::	How to specify other conventions.
* Beeping::             Audible signal to the user.
@end menu

@node Refresh Screen
@section Refreshing the Screen

The function @code{redraw-frame} redisplays the entire contents of a
given frame.  @xref{Frames}.

@c Emacs 19 feature
@defun redraw-frame frame
This function clears and redisplays frame @var{frame}.
@end defun

Even more powerful is @code{redraw-display}.

@deffn Command redraw-display &optional device
This function redraws all frames on @var{device} marked as having their
image garbled.  @var{device} defaults to the selected device.  If
@var{device} is @code{t}, all devices will have their frames checked.
@end deffn

  Normally, suspending and resuming XEmacs also refreshes the screen.
Some terminal emulators record separate contents for display-oriented
programs such as XEmacs and for ordinary sequential display.  If you are
using such a terminal, you might want to inhibit the redisplay on
resumption.  @xref{Suspending XEmacs}.

@defvar no-redraw-on-reenter
@cindex suspend (cf. @code{no-redraw-on-reenter})
@cindex resume (cf. @code{no-redraw-on-reenter})
This variable controls whether XEmacs redraws the entire screen after it
has been suspended and resumed.  Non-@code{nil} means yes, @code{nil}
means no.
@end defvar

@cindex display update
@cindex update display
@cindex refresh display
  The above functions do not actually cause the display to be updated;
rather, they clear out the internal display records that XEmacs
maintains, so that the next time the display is updated it will be
redrawn from scratch.  Normally this occurs the next time that
@code{next-event} or @code{sit-for} is called; however, a display update
will not occur if there is input pending.  @xref{Command Loop}.

@deffn Command force-redisplay
@cindex force redisplay
This function causes an immediate update of the display in all
circumstances, whether or not input is pending. (This function does
not exist in FSF Emacs.)
@end deffn

@defun force-cursor-redisplay
This function causes an immediate update of the cursor on the selected
frame. (This function does not exist in FSF Emacs.)
@end defun

@node Truncation
@section Truncation
@cindex line wrapping
@cindex continuation lines
@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 truncated or continued on the next line.  When a line
is truncated, this is normally shown with a @samp{\} in the rightmost
column of the window on X displays, and with a @samp{$} on TTY devices.
When a line is continued or ``wrapped'' onto the next line, this is
shown with a curved arrow in the rightmost column of the window (or with
a @samp{\} on TTY devices).  The additional screen lines used to display
a long text line are called @dfn{continuation} lines.  (Note that
wrapped lines are not filled; filling has nothing to do with
continuation and truncation.  @xref{Filling}.)

  Normally, whenever line truncation is in effect for a particular
window, a horizontal scrollbar is displayed in that window if the
device supports scrollbars.  @xref{Scrollbars}.

@defopt truncate-lines
   This buffer-local variable controls how XEmacs displays lines that
extend beyond the right edge of the window.  If it is non-@code{nil},
then XEmacs does not display continuation lines; rather each line of
text occupies exactly one screen line, and a backslash appears at the
edge of any line that extends to or beyond the edge of the window.  The
default is @code{nil}.

  If the variable @code{truncate-partial-width-windows} is
non-@code{nil}, then truncation is used for windows that are not the
full width of the screen, regardless of the value of
@code{truncate-lines}.
@end defopt

@defvar default-truncate-lines
  This variable is the default value for @code{truncate-lines} in buffers
that do not have local values for it.
@end defvar

@defopt truncate-partial-width-windows
  This variable determines how lines that are too wide to fit on the
screen are displayed in side-by-side windows (@pxref{Splitting
Windows}).  If it is non-@code{nil}, then wide lines are truncated (with
a @samp{\} at the end of the line); otherwise they wrap to the next
screen line (with a curved arrow at the end of the line).
@end defopt

  The backslash and curved arrow used to indicate truncated or continued
lines are only defaults, and can be changed.  These images are actually
glyphs (@pxref{Glyphs}).  XEmacs provides a great deal of flexibility
in how glyphs can be controlled. (This differs from FSF Emacs, which
uses display tables to control these images.)

@defvar truncation-glyph
  This variable holds the glyph that is displayed at the end of
truncated lines.
@end defvar

@defvar continuation-glyph
  This variable holds the glyphs that is displayed at the end of wrapped
lines.
@end defvar

@node The Echo Area
@section The Echo Area
@cindex error display
@cindex echo area

  The @dfn{echo area} is used for displaying messages made with the
@code{message} primitive, and for echoing keystrokes.  It is not the
same as the minibuffer, despite the fact that the minibuffer appears
(when active) in the same place on the screen as the echo area.  The
@cite{XEmacs Reference Manual} specifies the rules for resolving conflicts
between the echo area and the minibuffer for use of that screen space
(@pxref{Minibuffer,, The Minibuffer, emacs, The XEmacs Reference Manual}).
Error messages appear in the echo area; see @ref{Errors}.

You can write output in the echo area by using the Lisp printing
functions with @code{t} as the stream (@pxref{Output Functions}), or as
follows:

@defun message string &rest arguments
  This function prints a one-line message in the echo area.  The
argument @var{string} is similar to a C language @code{printf} control
string.  See @code{format} in @ref{String Conversion}, for the details
on the conversion specifications.  @code{message} returns the
constructed string.

@c Emacs 19 feature
If @var{string} is @code{nil}, @code{message} clears the echo area.  If
the minibuffer is active, this brings the minibuffer contents back onto
the screen immediately.
@example
@group
(message
 "Minibuffer depth is %d."
 (minibuffer-depth))
@result{} "Minibuffer depth is 0."
@end group

@group
---------- Echo Area ----------
Minibuffer depth is 0.
---------- Echo Area ----------
@end group
@end example
@end defun

@defvar cursor-in-echo-area
  This variable controls where the cursor appears when a message is
displayed in the echo area.  If it is non-@code{nil}, then the cursor
appears at the end of the message.  Otherwise, the cursor appears at
point---not in the echo area at all.

  The value is normally @code{nil}; Lisp programs bind it to @code{t}
for brief periods of time.
@end defvar

@node Selective Display
@section Selective Display
@cindex selective display

  @dfn{Selective display} is a class of minor modes in which specially
marked lines do not appear on the screen, or in which highly indented
lines do not appear.

  The first variant, explicit selective display, is designed for use in
a Lisp program.  The program controls which lines are hidden by altering
the text.  Outline mode uses this variant.  In the second variant, the
choice of lines to hide is made automatically based on indentation.
This variant is designed as a user-level feature.

  The way you control explicit selective display is by replacing a
newline (control-j) with a control-m.  The text which was formerly a
line following that newline is now invisible.  Strictly speaking, it is
temporarily no longer a line at all, since only newlines can separate
lines; it is now part of the previous line.

  Selective display does not directly affect editing commands.  For
example, @kbd{C-f} (@code{forward-char}) moves point unhesitatingly into
invisible space.  However, the replacement of newline characters with
carriage return characters affects some editing commands.  For example,
@code{next-line} skips invisible lines, since it searches only for
newlines.  Modes that use selective display can also define commands
that take account of the newlines, or which make parts of the text
visible or invisible.

  When you write a selectively displayed buffer into a file, all the
control-m's are replaced by their original newlines.  This means that
when you next read in the file, it looks OK, with nothing invisible.
The selective display effect is seen only within XEmacs.

@defvar selective-display
  This buffer-local variable enables selective display.  This means that
lines, or portions of lines, may be made invisible.  

@itemize @bullet
@item
If the value of @code{selective-display} is @code{t}, then any portion
of a line that follows a control-m is not displayed.

@item
If the value of @code{selective-display} is a positive integer, then
lines that start with more than @code{selective-display} columns of
indentation are not displayed.
@end itemize

  When some portion of a buffer is invisible, the vertical movement
commands operate as if that portion did not exist, allowing a single
@code{next-line} command to skip any number of invisible lines.
However, character movement commands (such as @code{forward-char}) do
not skip the invisible portion, and it is possible (if tricky) to insert
or delete text in an invisible portion.

  In the examples below, what is shown is the @emph{display} of the buffer
@code{foo}, which changes with the value of @code{selective-display}.  The
@emph{contents} of the buffer do not change.

@example
@group
(setq selective-display nil)
     @result{} nil

---------- Buffer: foo ----------
1 on this column
 2on this column
  3n this column
  3n this column
 2on this column
1 on this column
---------- Buffer: foo ----------
@end group

@group
(setq selective-display 2)
     @result{} 2

---------- Buffer: foo ----------
1 on this column
 2on this column
 2on this column
1 on this column
---------- Buffer: foo ----------
@end group
@end example
@end defvar

@defvar selective-display-ellipses
If this buffer-local variable is non-@code{nil}, then XEmacs displays
@samp{@dots{}} at the end of a line that is followed by invisible text.
This example is a continuation of the previous one.

@example
@group
(setq selective-display-ellipses t)
     @result{} t

---------- Buffer: foo ----------
1 on this column
 2on this column ...
 2on this column
1 on this column
---------- Buffer: foo ----------
@end group
@end example

You can use a display table to substitute other text for the ellipsis
(@samp{@dots{}}).  @xref{Display Tables}.
@end defvar

@node Overlay Arrow
@section Overlay Arrow
@cindex overlay arrow

  The @dfn{overlay arrow} is useful for directing the user's attention
to a particular line in a buffer.  For example, in the modes used for
interface to debuggers, the overlay arrow indicates the line of code
about to be executed.

@defvar overlay-arrow-string
This variable holds the string to display as an arrow, or @code{nil} if
the arrow feature is not in use.  Despite its name, the value of this
variable can be either a string or a glyph (@pxref{Glyphs}).
@end defvar

@defvar overlay-arrow-position
This variable holds a marker which indicates where to display the arrow.
It should point at the beginning of a line.  The arrow text is
displayed at the beginning of that line, overlaying any text that would
otherwise appear.  Since the arrow is usually short, and the line
usually begins with indentation, normally nothing significant is
overwritten.

The overlay string is displayed only in the buffer which this marker
points into.  Thus, only one buffer can have an overlay arrow at any
given time.
@c !!! overlay-arrow-position: but the overlay string may remain in the display
@c of some other buffer until an update is required.  This should be fixed
@c now.  Is it?
@end defvar

@node Temporary Displays
@section Temporary Displays

  Temporary displays are used by commands to put output into a buffer
and then present it to the user for perusal rather than for editing.
Many of the help commands use this feature.

@defspec with-output-to-temp-buffer buffer-name forms@dots{}
  This function executes @var{forms} while arranging to insert any
output they print into the buffer named @var{buffer-name}.  The buffer
is then shown in some window for viewing, displayed but not selected.

  The string @var{buffer-name} specifies the temporary buffer, which
need not already exist.  The argument must be a string, not a buffer.
The buffer is erased initially (with no questions asked), and it is
marked as unmodified after @code{with-output-to-temp-buffer} exits.

  @code{with-output-to-temp-buffer} binds @code{standard-output} to the
temporary buffer, then it evaluates the forms in @var{forms}.  Output
using the Lisp output functions within @var{forms} goes by default to
that buffer (but screen display and messages in the echo area, although
output in the general sense of the word, are not affected).
@xref{Output Functions}.

  The value of the last form in @var{forms} is returned.

@example
@group
---------- Buffer: foo ----------
 This is the contents of foo.
---------- Buffer: foo ----------
@end group

@group
(with-output-to-temp-buffer "foo"
    (print 20)
    (print standard-output))
@result{} #<buffer foo>

---------- Buffer: foo ----------
20

#<buffer foo>

---------- Buffer: foo ----------
@end group
@end example
@end defspec

@defvar temp-buffer-show-function
  The value of this variable, if non-@code{nil}, is called as a function
to display a help buffer.  This variable is used by
@code{with-output-to-temp-buffer}.

In Emacs versions 18 and earlier, this variable was called
@code{temp-buffer-show-hook}.
@end defvar

@defun momentary-string-display string position &optional char message
  This function momentarily displays @var{string} in the current
buffer at @var{position} (which is a character offset from the
beginning of the buffer).  The display remains until the next
character is typed.

  If the next character the user types is @var{char}, XEmacs ignores it.
Otherwise, that character remains buffered for subsequent use as input.
Thus, typing @var{char} will simply remove the string from the display,
while typing (say) @kbd{C-f} will remove the string from the display and
later (presumably) move point forward.  The argument @var{char} is a
space by default.

  The return value of @code{momentary-string-display} is not meaningful.

  If @var{message} is non-@code{nil}, it is displayed in the echo area
while @var{string} is displayed in the buffer.  If it is @code{nil},
then instructions to type @var{char} are displayed there, e.g.,
@samp{Type RET to continue editing}.

  In this example, point is initially located at the beginning of the
second line:

@example
@group
---------- Buffer: foo ----------
This is the contents of foo.
@point{}Second line.
---------- Buffer: foo ----------
@end group

@group
(momentary-string-display
   "**** Important Message! ****" (point) ?\r
   "Type RET when done reading")
@result{} t
@end group

@group
---------- Buffer: foo ----------
This is the contents of foo.
**** Important Message! ****Second line.
---------- Buffer: foo ----------

---------- Echo Area ----------
Type RET when done reading
---------- Echo Area ----------
@end group
@end example

  This function works by actually changing the text in the buffer.  As a
result, if you later undo in this buffer, you will see the message come
and go.
@end defun

@node Blinking
@section Blinking
@cindex parenthesis matching
@cindex blinking
@cindex balancing parentheses
@cindex close parenthesis

  This section describes the mechanism by which XEmacs shows a matching
open parenthesis when the user inserts a close parenthesis.

@vindex blink-paren-hook
@defvar blink-paren-function
  The value of this variable should be a function (of no arguments) to
be called whenever a char with close parenthesis syntax is inserted.
The value of @code{blink-paren-function} may be @code{nil}, in which
case nothing is done.

@quotation
@strong{Please note:} this variable was named @code{blink-paren-hook} in
older Emacs versions, but since it is not called with the standard
convention for hooks, it was renamed to @code{blink-paren-function} in
version 19.
@end quotation
@end defvar

@defvar blink-matching-paren
If this variable is @code{nil}, then @code{blink-matching-open} does
nothing.
@end defvar

@defvar blink-matching-paren-distance
This variable specifies the maximum distance to scan for a matching
parenthesis before giving up.
@end defvar

@defun blink-matching-open
This function is the default value of @code{blink-paren-function}.  It
assumes that point follows a character with close parenthesis syntax and
moves the cursor momentarily to the matching opening character.  If that
character is not already on the screen, then its context is shown by
displaying it in the echo area.  To avoid long delays, this function
does not search farther than @code{blink-matching-paren-distance}
characters.

Here is an example of calling this function explicitly.

@smallexample
@group
(defun interactive-blink-matching-open ()
@c Do not break this line! -- rms.
@c The first line of a doc string
@c must stand alone.
  "Indicate momentarily the start of sexp before point."
  (interactive)
@end group
@group
  (let ((blink-matching-paren-distance
         (buffer-size))
        (blink-matching-paren t))
    (blink-matching-open)))
@end group
@end smallexample
@end defun

@node Usual Display
@section Usual Display Conventions

  The usual display conventions define how to display each character
code.  You can override these conventions by setting up a display table
(@pxref{Display Tables}).  Here are the usual display conventions:

@itemize @bullet
@item
Character codes 32 through 126 map to glyph codes 32 through 126.
Normally this means they display as themselves.

@item
Character code 9 is a horizontal tab.  It displays as whitespace
up to a position determined by @code{tab-width}.

@item
Character code 10 is a newline.

@item
All other codes in the range 0 through 31, and code 127, display in one
of two ways according to the value of @code{ctl-arrow}.  If it is is
non-@code{nil}, these codes map to sequences of two glyphs, where the
first glyph is the ASCII code for @samp{^}.  Otherwise, these codes map
just like the codes in the range 128 to 255.

@item
Character codes 128 through 255 map to sequences of four glyphs, where
the first glyph is the ASCII code for @samp{\}, and the others are digit
characters representing the code in octal.
@end itemize

  The usual display conventions apply even when there is a display
table, for any character whose entry in the active display table is
@code{nil}.  Thus, when you set up a display table, you need only
specify the the characters for which you want unusual behavior.

  These variables affect the way certain characters are displayed on the
screen.  Since they change the number of columns the characters occupy,
they also affect the indentation functions.

@defopt ctl-arrow
@cindex control characters in display
  This buffer-local variable controls how control characters are
displayed.  If it is non-@code{nil}, they are displayed as a caret
followed by the character: @samp{^A}.  If it is @code{nil}, they are
displayed as a backslash followed by three octal digits: @samp{\001}.
@end defopt

@c Following may have overfull hbox.
@defvar default-ctl-arrow
  The value of this variable is the default value for @code{ctl-arrow} in
buffers that do not override it.  This is the same as executing the
following expression:

@example
(default-value 'ctl-arrow)
@end example

@noindent
@xref{Default Value}.
@end defvar

@defopt tab-width
  The value of this variable is the spacing between tab stops used for
displaying tab characters in Emacs buffers.  The default is 8.  Note
that this feature is completely independent from the user-settable tab
stops used by the command @code{tab-to-tab-stop}.  @xref{Indent Tabs}.
@end defopt

@node Display Tables
@section Display Tables

@cindex display table
You can use the @dfn{display table} feature to control how all 256
possible character codes display on the screen.  This is useful for
displaying European languages that have letters not in the ASCII
character set.

The display table maps each character code into a sequence of
@dfn{runes}, each rune being an image that takes up one character
position on the screen.  You can also define how to display each rune
on your terminal, using the @dfn{rune table}.

@menu
* Display Table Format::	What a display table consists of.
* Active Display Table::	How XEmacs selects a display table to use.
* Character Descriptors::	Format of an individual element of a
				  display table.
@end menu

@ignore Not yet working in XEmacs?
* ISO Latin 1::			How to use display tables
				  to support the ISO Latin 1 character set.
@end ignore

@node Display Table Format
@subsection Display Table Format

  A display table is an array of 256 elements. (In FSF Emacs, a display
table is 261 elements.  The five extra elements specify the truncation
and continuation glyphs, etc.  This method is very kludgey, and in
XEmacs the variables @code{truncation-glyph}, @code{continuation-glyph},
etc. are used.  @xref{Truncation}.  )

@defun make-display-table
This creates and returns a display table.  The table initially has
@code{nil} in all elements.
@end defun

  The 256 elements correspond to character codes; the @var{n}th
element says how to display the character code @var{n}.  The value
should be @code{nil}, a string, a glyph, or a vector of strings and
glyphs (@pxref{Character Descriptors}).  If an element is @code{nil},
it says to display that character according to the usual display
conventions (@pxref{Usual Display}).

  For example, here is how to construct a display table that mimics the
effect of setting @code{ctl-arrow} to a non-@code{nil} value:

@example
(setq disptab (make-display-table))
(let ((i 0))
  (while (< i 32)
    (or (= i ?\t) (= i ?\n)
        (aset disptab i (concat "^" (char-to-string (+ i 64)))))
    (setq i (1+ i)))
  (aset disptab 127 "^?"))
@end example

@node Active Display Table
@subsection Active Display Table
@cindex active display table

  The active display table is controlled by the variable
@code{current-display-table}.  This is a specifier, which means
that you can specify separate values for it in individual buffers,
windows, frames, and devices, as well as a global value.  It also
means that you cannot set this variable using @code{setq}; use
@code{set-specifier} instead.  @xref{Specifiers}. (FSF Emacs
uses @code{window-display-table}, @code{buffer-display-table},
@code{standard-display-table}, etc. to control the display table.
However, specifiers are a cleaner and more powerful way of doing
the same thing.  FSF Emacs also uses a different format for
the contents of a display table, using additional indirection
to a ``glyph table'' and such.  Note that ``glyph'' has a different
meaning in XEmacs.)

  Individual faces can also specify an overriding display table;
this is set using @code{set-face-display-table}.  @xref{Faces}.

  If no display table can be determined for a particular window,
then XEmacs uses the usual display conventions.  @xref{Usual Display}.

@node Character Descriptors
@subsection Character Descriptors

@cindex character descriptor
  Each element of the display-table vector describes how to display
a particular character and is called a @dfn{character descriptor}.
A character descriptor can be:

@table @asis
@item a string
Display this particular string wherever the character is to be displayed.

@item a glyph
Display this particular glyph wherever the character is to be displayed.

@item a vector
The vector may contain strings and/or glyphs.  Display the elements of
the vector one after another wherever the character is to be displayed.

@item @code{nil}
Display according to the standard interpretation (@pxref{Usual Display}).
@end table

@ignore Not yet working in XEmacs?
@node ISO Latin 1
@subsection ISO Latin 1

If you have a terminal that can handle the entire ISO Latin 1 character
set, you can arrange to use that character set as follows:

@example
(require 'disp-table)
;; @r{Set char codes 160--255 to display as themselves.}
;; @r{(Codes 128--159 are the additional control characters.)}
(standard-display-8bit 160 255)
@end example

If you are editing buffers written in the ISO Latin 1 character set and
your terminal doesn't handle anything but ASCII, you can load the file
@file{iso-ascii} to set up a display table which makes the other ISO
characters display as sequences of ASCII characters.  For example, the
character ``o with umlaut'' displays as @samp{@{"o@}}.

Some European countries have terminals that don't support ISO Latin 1
but do support the special characters for that country's language.  You
can define a display table to work one language using such terminals.
For an example, see @file{lisp/iso-swed.el}, which handles certain
Swedish terminals.

You can load the appropriate display table for your terminal
automatically by writing a terminal-specific Lisp file for the terminal
type.
@end ignore

@node Beeping
@section Beeping
@cindex beeping
@cindex bell
@cindex sound

  You can make XEmacs ring a bell, play a sound, or blink the screen to
attract the user's attention.  Be conservative about how often you do
this; frequent bells can become irritating.  Also be careful not to use
beeping alone when signaling an error is appropriate.  (@xref{Errors}.)

@defun ding &optional dont-terminate sound device
@cindex keyboard macro termination
  This function beeps, or flashes the screen (see @code{visible-bell}
below).  It also terminates any keyboard macro currently executing
unless @var{dont-terminate} is non-@code{nil}.  If @var{sound} is
specified, it should be a symbol specifying which sound to make.  This
sound will be played if @code{visible-bell} is @code{nil}. (This only
works if sound support was compiled into the executable and you are
running on the console of a Sun SparcStation, SGI, or HP9000s700.
Otherwise you just get a beep.) The optional third argument specifies
what device to make the sound on, and defaults to the selected device.
@end defun

@defun beep &optional dont-terminate sound device
This is a synonym for @code{ding}.
@end defun

@defopt visible-bell
  This variable determines whether XEmacs should flash the screen to
represent a bell.  Non-@code{nil} means yes, @code{nil} means no.  On
TTY devices, this is effective only if the Termcap entry for the
terminal type has the visible bell flag (@samp{vb}) set.
@end defopt

@defvar sound-alist
  This variable holds an alist associating names with sounds.  When
@code{beep} or @code{ding} is called with one of the name symbols, the
associated sound will be generated instead of the standard beep.

  Each element of @code{sound-alist} is a list describing a sound.  The
first element of the list is the name of the sound being defined.
Subsequent elements of the list are alternating keyword/value pairs:

@table @code
@item sound
A string of raw sound data, or the name of another sound to play.  The
symbol @code{t} here means use the default X beep.
@item volume
An integer from 0-100, defaulting to @code{bell-volume}.
@item pitch
If using the default X beep, the pitch (Hz) to generate.
@item duration
If using the default X beep, the duration (milliseconds).
@end table

For compatibility, elements of `sound-alist' may also be:

@itemize @bullet
@item
@code{( sound-name . <sound> )}
@item
@code{( sound-name <volume> <sound> )}
@end itemize

You should probably add things to this list by calling the function
@code{load-sound-file}.

Caveats:

@itemize @minus
@item
You can only play audio data if running on the console screen of a Sun
SparcStation, SGI, or HP9000s700.

@item
The pitch, duration, and volume options are available everywhere, but
many X servers ignore the `pitch' option.
@end itemize

The following beep-types are used by XEmacs itself:

@table @code
@item auto-save-error
when an auto-save does not succeed
@item command-error
when the XEmacs command loop catches an error
@item undefined-key
when you type a key that is undefined
@item undefined-click
when you use an undefined mouse-click combination
@item no-completion
during completing-read
@item y-or-n-p
when you type something other than 'y' or 'n'
@item yes-or-no-p
when you type something other than 'yes' or 'no'
@item default
used when nothing else is appropriate.
@end table

Other lisp packages may use other beep types, but these are the ones that
the C kernel of XEmacs uses.
@end defvar

@defopt bell-volume
This variable specifies the default volume for sounds, from 0 to 100.
@end defopt

@deffn Command load-default-sounds
This function loads and installs some sound files as beep-types.
@end deffn

@deffn Command load-sound-file filename sound-name &optional volume
This function reads in an audio file and adds it to @code{sound-alist}.
The sound file must be in the Sun/NeXT U-LAW format.  @var{sound-name}
should be a symbol, specifying the name of the sound.  If @var{volume}
is specified, the sound will be played at that volume; otherwise, the
value of @var{bell-volume} will be used.
@end deffn

@defun play-sound sound &optional volume device
This function plays sound @var{sound}, which should be a symbol
mentioned in @code{sound-alist}.  If @var{volume} is specified, it
overrides the value (if any) specified in @code{sound-alist}.
@var{device} specifies the device to play the sound on, and defaults
to the selected device.
@end defun

@deffn Command play-sound-file file &optional volume device
This function plays the named sound file at volume @var{volume}, which
defaults to @code{bell-volume}.  @var{device} specifies the device to
play the sound on, and defaults to the selected device.
@end deffn
