This chapter describes a number of features related to the display that Emacs presents to the user.
The function redraw-frame redisplays the entire contents of a
given frame (see section Frames).
Even more powerful is redraw-display:
Processing user input takes absolute priority over redisplay. If you call these functions when input is available, they do nothing immediately, but a full redisplay does happen eventually--after all the input has been processed.
Normally, suspending and resuming Emacs also refreshes the screen. Some terminal emulators record separate contents for display-oriented programs such as Emacs and for ordinary sequential display. If you are using such a terminal, you might want to inhibit the redisplay on resumption.
nil means there is no need
to redraw, nil means redrawing is needed. The default is nil.
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 continuation lines. Normally, a `$' in the rightmost column of the window indicates truncation; a `\' on the rightmost column indicates a line that "wraps" onto the next line, which is also called continuing the line. (The display table can specify alternative indicators; see section Display Tables.)
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. See section Filling.
nil, which
specifies continuation. If the value is non-nil, then these
lines are truncated.
If the variable truncate-partial-width-windows is non-nil,
then truncation is always used for side-by-side windows (within one
frame) regardless of the value of truncate-lines.
truncate-lines, for
buffers that do not have buffer-local values for it.
nil, these lines are truncated; otherwise,
truncate-lines says what to do with them.
When horizontal scrolling (see section Horizontal Scrolling) is in use in a window, that forces truncation.
You can override the glyphs that indicate continuation or truncation using the display table; see section Display Tables.
If your buffer contains very long lines, and you use
continuation to display them, just thinking about them can make Emacs
redisplay slow. The column computation and indentation functions also
become slow. Then you might find it advisable to set
cache-long-line-scans to t.
nil, various indentation and motion
functions, and Emacs redisplay, cache the results of scanning the
buffer, and consult the cache to avoid rescanning regions of the buffer
unless they are modified.
Turning on the cache slows down processing of short lines somewhat.
This variable is automatically buffer-local in every buffer.
The echo area is used for displaying messages made with the
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
GNU Emacs Manual specifies the rules for resolving conflicts
between the echo area and the minibuffer for use of that screen space
(see section `The Minibuffer' in The GNU Emacs Manual).
Error messages appear in the echo area; see section Errors.
You can write output in the echo area by using the Lisp printing
functions with t as the stream (see section Output Functions), or as
follows:
printf control
string. See format in section Conversion of Characters and Strings, for the details
on the conversion specifications. message returns the
constructed string.
In batch mode, message prints the message text on the standard
error stream, followed by a newline.
If string is nil, message clears the echo area. If
the minibuffer is active, this brings the minibuffer contents back onto
the screen immediately.
(message "Minibuffer depth is %d."
(minibuffer-depth))
-| Minibuffer depth is 0.
=> "Minibuffer depth is 0."
---------- Echo Area ----------
Minibuffer depth is 0.
---------- Echo Area ----------
message, but may display it
in a dialog box instead of the echo area. If this function is called in
a command that was invoked using the mouse--more precisely, if
last-nonmenu-event (see section Information from the Command Loop) is either
nil or a list--then it uses a dialog box or pop-up menu to
display the message. Otherwise, it uses the echo area. (This is the
same criterion that y-or-n-p uses to make a similar decision; see
section Yes-or-No Queries.)
You can force use of the mouse or of the echo area by binding
last-nonmenu-event to a suitable value around the call.
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
support them, then message-box uses the echo area, like
message.
nil if there is none.
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 nil; Lisp programs bind it to t
for brief periods of time.
(message nil) or for any other reason.
Almost all the messages displayed in the echo area are also recorded in the `*Messages*' buffer.
t means there is no limit on how many lines to
keep. The value nil disables message logging entirely. Here's
how to display a message and prevent it from being logged:
(let (message-log-max) (message ...))
If the value is zero, then command input is not echoed.
You can make characters invisible, so that they do not appear on
the screen, with the invisible property. This can be either a
text property (see section Text Properties) or a property of an overlay
(see section Overlays).
In the simplest case, any non-nil invisible property makes
a character invisible. This is the default case--if you don't alter
the default value of buffer-invisibility-spec, this is how the
invisible property works.
More generally, you can use the variable buffer-invisibility-spec
to control which values of the invisible property make text
invisible. This permits you to classify the text into different subsets
in advance, by giving them different invisible values, and
subsequently make various subsets visible or invisible by changing the
value of buffer-invisibility-spec.
Controlling visibility with buffer-invisibility-spec is
especially useful in a program to display the list of entries in a data
base. It permits the implementation of convenient filtering commands to
view just a part of the entries in the data base. Setting this variable
is very fast, much faster than scanning all the text in the buffer
looking for properties to change.
invisible properties
actually make a character invisible.
t
invisible property is
non-nil. This is the default.
invisible property fits any one of these criteria,
the character is invisible. The list can have two kinds of elements:
atom
invisible property value
is atom or if it is a list with atom as a member.
(atom . t)
invisible property value
is atom or if it is a list with atom as a member.
Moreover, if this character is at the end of a line and is followed
by a visible newline, it displays an ellipsis.
Two functions are specifically provided for adding elements to
buffer-invisibility-spec and removing elements from it.
buffer-invisibility-spec
(if it is not already present in that list).
buffer-invisibility-spec.
One convention about the use of buffer-invisibility-spec is
that a major mode should use the mode's own name as an element of
buffer-invisibility-spec and as the value of the invisible
property:
;; If you want to display an ellipsis:
(add-to-invisibility-spec '(my-symbol . t))
;; If you don't want ellipsis:
(add-to-invisibility-spec 'my-symbol)
(overlay-put (make-overlay beginning end)
'invisible 'my-symbol)
;; When done with the overlays:
(remove-from-invisibility-spec '(my-symbol . t))
;; Or respectively:
(remove-from-invisibility-spec 'my-symbol)
Ordinarily, commands that operate on text or move point do not care
whether the text is invisible. The user-level line motion commands
explicitly ignore invisible newlines if
line-move-ignore-invisible is non-nil, but only because
they are explicitly programmed to do so.
Incremental search can make invisible overlays visible temporarily
and/or permanently when a match includes invisible text. To enable
this, the overlay should have a non-nil
isearch-open-invisible property. The property value should be a
function to be called with the overlay as an argument. This function
should make the overlay visible permanently; it is used when the match
overlaps the overlay on exit from the search.
During the search, such overlays are made temporarily visible by
temporarily modifying their invisible and intangible properties. If you
want this to be done differently for a certain overlay, give it an
isearch-open-invisible-temporary property which is a function.
The function is called with two arguments: the first is the overlay, and
the second is t to make the overlay visible, or nil to
make it invisible again.
Selective display refers to a pair of related features for hiding certain lines on the screen.
The first variant, explicit selective display, is designed for use in a Lisp program: it controls which lines are hidden by altering the text. The invisible text feature (see section Invisible Text) has partially replaced this feature.
In the second variant, the choice of lines to hide is made automatically based on indentation. This variant is designed to be a user-level feature.
The way you control explicit selective display is by replacing a newline (control-j) with a carriage return (control-m). The text that 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, C-f (forward-char) moves point unhesitatingly into
invisible text. However, the replacement of newline characters with
carriage return characters affects some editing commands. For example,
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 that make parts of the text
visible or invisible.
When you write a selectively displayed buffer into a file, all the control-m's are output as 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 Emacs.
selective-display is t, then any portion
of a line that follows a control-m is not displayed. This is explicit
selective display.
selective-display is a positive integer, then
lines that start with more than that many columns of indentation are not
displayed.
When some portion of a buffer is invisible, the vertical movement
commands operate as if that portion did not exist, allowing a single
next-line command to skip any number of invisible lines.
However, character movement commands (such as 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, we show the display appearance of the
buffer foo, which changes with the value of
selective-display. The contents of the buffer do not
change.
(setq selective-display nil)
=> 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 ----------
(setq selective-display 2)
=> 2
---------- Buffer: foo ----------
1 on this column
2on this column
2on this column
1 on this column
---------- Buffer: foo ----------
nil, then Emacs displays
`...' at the end of a line that is followed by invisible text.
This example is a continuation of the previous one.
(setq selective-display-ellipses t)
=> t
---------- Buffer: foo ----------
1 on this column
2on this column ...
2on this column
1 on this column
---------- Buffer: foo ----------
You can use a display table to substitute other text for the ellipsis (`...'). See section Display Tables.
The 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.
nil if the arrow feature is not in use.
The overlay string is displayed only in the buffer that this marker points into. Thus, only one buffer can have an overlay arrow at any given time.
You can do a similar job by creating an overlay with a
before-string property. See section Overlay Properties.
Temporary displays are used by Lisp programs to put output into a buffer and then present it to the user for perusal rather than for editing. Many help commands use this feature.
The string 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 with-output-to-temp-buffer exits.
with-output-to-temp-buffer binds standard-output to the
temporary buffer, then it evaluates the forms in forms. Output
using the Lisp output functions within forms goes by default to
that buffer (but screen display and messages in the echo area, although
they are "output" in the general sense of the word, are not affected).
See section Output Functions.
The value of the last form in forms is returned.
---------- Buffer: foo ----------
This is the contents of foo.
---------- Buffer: foo ----------
(with-output-to-temp-buffer "foo"
(print 20)
(print standard-output))
=> #<buffer foo>
---------- Buffer: foo ----------
20
#<buffer foo>
---------- Buffer: foo ----------
nil, with-output-to-temp-buffer
calls it as a function to do the job of displaying a help buffer. The
function gets one argument, which is the buffer it should display.
It is a good idea for this function to run temp-buffer-show-hook
just as with-output-to-temp-buffer normally would, inside of
save-window-excursion and with the chosen window and buffer
selected.
with-output-to-temp-buffer after
displaying the help buffer. When the hook runs, the help buffer is
current, and the window it was displayed in is selected.
The momentary display remains until the next input event. If the next
input event is char, momentary-string-display ignores it
and returns. Otherwise, that event remains buffered for subsequent use
as input. Thus, typing char will simply remove the string from
the display, while typing (say) C-f will remove the string from
the display and later (presumably) move point forward. The argument
char is a space by default.
The return value of momentary-string-display is not meaningful.
If the string string does not contain control characters, you can
do the same job in a more general way by creating (and then subsequently
deleting) an overlay with a before-string property.
See section Overlay Properties.
If message is non-nil, it is displayed in the echo area
while string is displayed in the buffer. If it is nil, a
default message says to type char to continue.
In this example, point is initially located at the beginning of the second line:
---------- Buffer: foo ---------- This is the contents of foo. -!-Second line. ---------- Buffer: foo ---------- (momentary-string-display "**** Important Message! ****" (point) ?\r "Type RET when done reading") => t ---------- Buffer: foo ---------- This is the contents of foo. **** Important Message! ****Second line. ---------- Buffer: foo ---------- ---------- Echo Area ---------- Type RET when done reading ---------- Echo Area ----------
You can use overlays to alter the appearance of a buffer's text on the screen, for the sake of presentation features. An overlay is an object that belongs to a particular buffer, and has a specified beginning and end. It also has properties that you can examine and set; these affect the display of the text within the overlay.
Overlay properties are like text properties in that the properties that alter how a character is displayed can come from either source. But in most respects they are different. Text properties are considered a part of the text; overlays are specifically considered not to be part of the text. Thus, copying text between various buffers and strings preserves text properties, but does not try to preserve overlays. Changing a buffer's text properties marks the buffer as modified, while moving an overlay or changing its properties does not. Unlike text property changes, overlay changes are not recorded in the buffer's undo list. See section Text Properties, for comparison.
priority
priority value is larger takes priority over the
other, and its face attributes override the face attributes of the lower
priority overlay.
Currently, all overlays take priority over text properties. Please
avoid using negative priority values, as we have not yet decided just
what they should mean.
window
window property is non-nil, then the overlay
applies only on that window.
category
category property, we call it the
category of the overlay. It should be a symbol. The properties
of the symbol serve as defaults for the properties of the overlay.
face
(foreground-color . color-name) or (background-color
. color-name). These elements specify just the foreground color
or just the background color; therefore, there is no need to create a
face for each color that you want to use.
mouse-face
face when the mouse is within
the range of the overlay.
modification-hooks
nil, and the beginning and end of the text range to be
modified.
When called after a change, each function receives five arguments: the
overlay, t, the beginning and end of the text range just
modified, and the length of the pre-change text replaced by that range.
(For an insertion, the pre-change length is zero; for a deletion, that
length is the number of characters deleted, and the post-change
beginning and end are equal.)
insert-in-front-hooks
modification-hooks functions.
insert-behind-hooks
modification-hooks functions.
invisible
invisible property can make the text in the overlay
invisible, which means that it does not appear on the screen.
See section Invisible Text, for details.
intangible
intangible property on an overlay works just like the
intangible text property. See section Properties with Special Meanings, for details.
isearch-open-invisible
isearch-open-invisible-temporary
before-string
after-string
evaporate
nil, the overlay is deleted automatically
if it ever becomes empty (i.e., if it spans no characters).
local-map
nil, it specifies a keymap for a portion
of the text. The property's value replaces the buffer's local map, when
the character after point is within the overlay. See section Active Keymaps.
These are the functions for reading and writing the properties of an overlay.
category property which is a
symbol, that symbol's prop property is used. Otherwise, the value
is nil.
See also the function get-char-property which checks both
overlay properties and text properties for a given character.
See section Examining Text Properties.
This section describes the functions to create, delete and move overlays, and to examine their contents.
The arguments front-advance and rear-advance specify the insertion type for the start of the overlay and for the end of the overlay. See section Marker Insertion Types.
A deleted overlay is not permanently useless. You can give it
a new buffer position by calling move-overlay.
The return value is overlay.
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".
Since not all characters have the same width, these functions let you check the width of a character. See section Indentation Primitives, and section Motion by Screen Lines, for related functions.
If string does not reach width, then the result ends where string ends. If one multi-column character in string extends across the column width, that character is not included in the result. Thus, the result can fall short of width but cannot go beyond it.
The optional argument start-column specifies the starting column.
If this is non-nil, then the first start-column columns of
the string are omitted from the value. If one multi-column character in
string extends across the column start-column, that
character is not included.
The optional argument padding, if non-nil, is a padding
character added at the beginning and end of the result string, to extend
it to exactly width columns. The padding character is used at the
end of the result if it falls short of width. It is also used at
the beginning of the result if one multi-column character in
string extends across the column start-column.
(truncate-string-to-width "\tab\t" 12 4)
=> "ab"
(truncate-string-to-width "\tab\t" 12 4 ?\ )
=> " ab "
A face is a named collection of graphical attributes: font, foreground color, background color, and optional underlining. Faces control the display of text on the screen.
Each face has its own face number, which distinguishes faces at low levels within Emacs. However, for most purposes, you can refer to faces in Lisp programs by their names.
t if object is a face name symbol (or
if it is a vector of the kind used internally to record face data). It
returns nil otherwise.
Each face name is meaningful for all frames, and by default it has the same meaning in all frames. But you can arrange to give a particular face name a special meaning in one frame if you wish.
This table lists all the standard faces and their uses.
default
modeline
region
secondary-selection
highlight
underline
bold
italic
bold-italic
The way to define a new face is with defface. This creates a
kind of customization item (see section Writing Customization Definitions) which the user can
customize using the Customization buffer (see section `Easy Customization' in The GNU Emacs Manual).
When defface executes, it defines the face according to
spec, then uses any customizations that were read from the
`.emacs' file to override that specification.
The purpose of spec is to specify how the face should appear on
different kinds of terminals. It should be an alist whose elements have
the form (display atts). The element's CAR,
display, specifies a class of terminals. The CDR,
atts, is a list of face attributes and their values; it specifies
what the face should look like on that kind of terminal. The possible
attributes are defined in the value of custom-face-attributes.
The display part of an element of spec determines which frames the element applies to. If more than one element of spec matches a given frame, the first matching element is the only one used for that frame. There are two possibilities for display:
t
t is used in the last (or only) element of spec.
(characteristic value...). Here
characteristic specifies a way of classifying frames, and the
values are possible classifications which display should
apply to. Here are the possible values of characteristic:
type
x, pc
(for the MS-DOS console), w32 (for MS Windows 9X/NT), or
tty.
class
color,
grayscale, or mono.
background
light or dark.
Here's how the standard face region could be defined
with defface:
(defface region
((((class color) (background dark))
(:background "blue"))
(t (:background "gray")))
"Used for displaying the region.")
Internally, defface uses the symbol property
face-defface-spec to record the face attributes specified in
defface, saved-face for the attributes saved by the user
with the customization buffer, and face-documentation for the
documentation string.
nil, specifies the background type to use for
interpreting face definitions. If it is dark, then Emacs treats
all frames as if they had a dark background, regardless of their actual
background colors. If it is light, then Emacs treats all frames
as if they had a light background.
Here are all the ways to specify which face to use for display of text:
face property; if so,
it is displayed with that face. See section Properties with Special Meanings.
If the character has a mouse-face property, that is used instead
of the face property when the mouse is "near enough" to the
character.
face and mouse-face
properties too; they apply to all the text covered by the overlay.
region-face, below).
If these various sources together specify more than one face for a particular character, Emacs merges the attributes of the various faces specified. The attributes of the faces of special glyphs come first; then comes the face for region highlighting, if appropriate; then come attributes of faces from overlays, followed by those from text properties, and last the default face.
When multiple overlays cover one character, an overlay with higher priority overrides those with lower priority. See section Overlays.
If an attribute such as the font or a color is not specified in any of the above ways, the frame's own font or color is used.
The attributes a face can specify include the font, the foreground
color, the background color, and underlining. The face can also leave
these unspecified by giving the value nil for them.
Here are the primitives for creating and changing faces.
nil. It does nothing if there is already a face named
name.
If the optional argument frame is given, this function applies only to that frame. Otherwise it applies to each frame individually, copying attributes from old-face in each frame to new-face in the same frame.
If the optional argument new-frame is given, then copy-face
copies the attributes of old-face in frame to new-name
in new-frame.
You can modify the attributes of an existing face with the following functions. If you specify frame, they affect just that frame; otherwise, they affect all frames as well as the defaults that apply to new frames.
Certain shades of gray are implemented by stipple patterns on black-and-white screens.
nil meaning don't use
stipple.
Normally there is no need to pay attention to stipple patterns, because they are used automatically to handle certain shades of gray.
nil means bold; nil means non-bold.
nil means italic; nil means non-italic.
nil means do underline; nil means don't.
These functions examine the attributes of a face. If you don't specify frame, they refer to the default data for new frames.
nil if it doesn't have one.
nil if none was specified for it.
t if the faces face1 and face2 have the
same attributes for display.
t if the face face displays differently from
the default face. A face is considered to be "the same" as the normal
face if each attribute is either the same as that of the default face or
nil (meaning to inherit from the default).
Normally, the value is the face number of the face named region.
This section describes the mechanism by which Emacs shows a matching open parenthesis when the user inserts a close parenthesis.
blink-paren-function may be nil, in which
case nothing is done.
nil, then blink-matching-open does
nothing.
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, it displays the character's
context in the echo area. To avoid long delays, this function does not
search farther than blink-matching-paren-distance characters.
Here is an example of calling this function explicitly.
(defun interactive-blink-matching-open ()
"Indicate momentarily the start of sexp before point."
(interactive)
(let ((blink-matching-paren-distance
(buffer-size))
(blink-matching-paren t))
(blink-matching-open)))
nil means yes, nil means no. The
default is nil.
nil, then mode lines are displayed in inverse video.
Otherwise, mode lines are displayed normally, just like text. The
default is t.
For window frames, this displays mode lines using the face named
modeline, which is normally the inverse of the default face
unless you change it.
The usual display conventions define how to display each character code. You can override these conventions by setting up a display table (see section Display Tables). Here are the usual display conventions:
tab-width.
ctl-arrow. If it is
non-nil, these codes map to sequences of two glyphs, where the
first glyph is the ASCII code for `^'. (A display table can
specify a glyph to use instead of `^'.) Otherwise, these codes map
just like the codes in the range 128 to 255.
The usual display conventions apply even when there is a display
table, for any character whose entry in the active display table is
nil. Thus, when you set up a display table, you need only
specify the characters for which you want special 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. These variables also affect
how the mode line is displayed; if you want to force redisplay of the
mode line using the new values, call the function
force-mode-line-update (see section Mode Line Format).
nil, they are displayed as a caret
followed by the character: `^A'. If it is nil, they are
displayed as a backslash followed by three octal digits: `\001'.
ctl-arrow in
buffers that do not override it. See section The Default Value of a Buffer-Local Variable.
tab-to-tab-stop. See section Adjustable "Tab Stops".
You can use the display table feature to control how all 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 glyphs, each glyph being an image that takes up one character position on the screen. You can also define how to display each glyph on your terminal, using the glyph table.
Display tables affect how the mode line is displayed; if you want to
force redisplay of the mode line using a new display table, call
force-mode-line-update (see section Mode Line Format).
A display table is actually a char-table (see section Char-Tables) with
display-table as its subtype.
nil in all elements.
The ordinary elements of the display table are indexed by character
codes; the element at index c says how to display the character
code c. The value should be nil or a vector of glyph
values (see section Glyphs). If an element is nil, it says to
display that character according to the usual display conventions
(see section Usual Display Conventions).
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; nil in any slot
means to use the default for that slot, as stated below.
For example, here is how to construct a display table that mimics the
effect of setting ctl-arrow to a non-nil value:
(setq disptab (make-display-table))
(let ((i 0))
(while (< i 32)
(or (= i ?\t) (= i ?\n)
(aset disptab i (vector ?^ (+ i 64))))
(setq i (1+ i)))
(aset disptab 127 (vector ?^ ??)))
truncation, wrap, escape, control,
selective-display, and vertical-border.
truncation, wrap, escape, control,
selective-display, and vertical-border.
Each window can specify a display table, and so can each buffer. When a buffer b is displayed in window w, display uses the display table for window w if it has one; otherwise, the display table for buffer b if it has one; otherwise, the standard display table if any. The display table chosen is called the active display table.
nil
if window does not have an assigned display table.
nil.
nil, that means the buffer does not have an assigned display
table.
nil by default.
If there is no display table to use for a particular window--that is,
if the window specifies none, its buffer specifies none, and
standard-display-table is nil---then Emacs uses the usual
display conventions for all character codes in that window. See section Usual Display Conventions.
A 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.
The meaning of each integer, as a glyph, is defined by the glyph
table, which is the value of the variable glyph-table.
nil instead of a vector, then all glyphs are simple (see
below).
Here are the possible types of elements in the glyph table:
nil
If a glyph code is greater than or equal to the length of the glyph table, that code is automatically simple.
This section describes how to make Emacs ring the bell (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 just beeping when signaling an error is more appropriate. (See section Errors.)
visible-bell below).
It also terminates any keyboard macro currently executing unless
do-not-terminate is non-nil.
ding.
nil means yes, nil means no. This
is effective on a window system, and on a character-only terminal
provided the terminal's Termcap entry defines the visible bell
capability (`vb').
nil, it specifies how Emacs should "ring the
bell." Its value should be a function of no arguments.
Emacs works with several window systems, most notably the X Window 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.
x
pc
w32
nil
term-setup-hook.
This hook is used for internal purposes: setting up communication with the window system, and creating the initial window. Users should not interfere with it.
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