@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
-@c Copyright (C) 1990, 1991, 1992, 1993, 1994 Free Software Foundation, Inc.
+@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998 Free Software Foundation, Inc.
@c See the file elisp.texi for copying conditions.
@setfilename ../info/display
-@node Display, Calendar, System Interface, Top
+@node Display, Calendar, Processes, Top
@chapter Emacs Display
This chapter describes a number of features related to the display
@menu
* Refresh Screen:: Clearing the screen and redrawing everything on it.
-* Screen Size:: How big is the Emacs screen.
* Truncation:: Folding or wrapping long text lines.
* The Echo Area:: Where messages are displayed.
* Invisible Text:: Hiding part of the buffer text.
* Overlay Arrow:: Display of an arrow to indicate position.
* Temporary Displays:: Displays that go away automatically.
* Overlays:: Use overlays to highlight parts of the buffer.
+* Width:: How wide is a character or string.
* Faces:: A face defines a graphics appearance: font, color, etc.
* Blinking:: How Emacs shows the matching open parenthesis.
* Inverse Video:: Specifying how the screen looks.
@section Refreshing the Screen
The function @code{redraw-frame} redisplays the entire contents of a
-given frame. @xref{Frames}.
+given frame (@pxref{Frames}).
@c Emacs 19 feature
@defun redraw-frame frame
This function clears and redisplays all visible frames.
@end deffn
+ 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
@cindex suspend (cf. @code{no-redraw-on-reenter})
@cindex resume (cf. @code{no-redraw-on-reenter})
This variable controls whether Emacs redraws the entire screen after it
-has been suspended and resumed. Non-@code{nil} means yes, @code{nil}
-means no.
+has been suspended and resumed. Non-@code{nil} means there is no need
+to redraw, @code{nil} means redrawing is needed. The default is @code{nil}.
@end defvar
- 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.
-
-@node Screen Size
-@section Screen Size
-@cindex size of screen
-@cindex screen size
-@cindex display lines
-@cindex display columns
-@cindex resize redisplay
-
- The screen size functions access or specify the height or width of
-the terminal. When you are using multiple frames, they apply to the
-selected frame (@pxref{Frames}).
-
-@defun screen-height
-This function returns the number of lines on the screen that are
-available for display.
-
-@example
-@group
-(screen-height)
- @result{} 50
-@end group
-@end example
-@end defun
-
-@defun screen-width
-This function returns the number of columns on the screen that are
-available for display.
-
-@example
-@group
-(screen-width)
- @result{} 80
-@end group
-@end example
-@end defun
-
-@defun set-screen-height lines &optional not-actual-size
-This function declares that the terminal can display @var{lines} lines.
-The sizes of existing windows are altered proportionally to fit.
-
-If @var{not-actual-size} is non-@code{nil}, then Emacs displays
-@var{lines} lines of output, but does not change its value for the
-actual height of the screen. (Knowing the correct actual size may be
-necessary for correct cursor positioning.) Using a smaller height than
-the terminal actually implements may be useful to reproduce behavior
-observed on a smaller screen, or if the terminal malfunctions when using
-its whole screen.
-
-If @var{lines} is different from what it was previously, then the
-entire screen is cleared and redisplayed using the new size.
-
-This function returns @code{nil}.
-@end defun
-
-@defun set-screen-width columns &optional not-actual-size
-This function declares that the terminal can display @var{columns}
-columns. The details are as in @code{set-screen-height}.
-@end defun
-
@node Truncation
@section Truncation
@cindex line wrapping
one screen line. The additional screen lines used to display a long
text line are called @dfn{continuation} lines. Normally, a @samp{$} in
the rightmost column of the window indicates truncation; a @samp{\} on
-the rightmost column indicates a line that ``wraps'' or is continued
-onto the next line. (The display table can specify alternative
-indicators; see @ref{Display Tables}.)
+the rightmost column indicates a line that ``wraps'' onto the next line,
+which is also called @dfn{continuing} the line. (The display table can
+specify alternative indicators; see @ref{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
frame) regardless of the value of @code{truncate-lines}.
@end defopt
-@defvar default-truncate-lines
+@defopt default-truncate-lines
This variable is the default value for @code{truncate-lines}, for
-buffers that do not have local values for it.
-@end defvar
+buffers that do not have buffer-local values for it.
+@end defopt
@defopt truncate-partial-width-windows
This variable controls display of lines that extend beyond the right
@code{truncate-lines} says what to do with them.
@end defopt
- You can override the images that indicate continuation or truncation
-with the display table; see @ref{Display Tables}.
+ When horizontal scrolling (@pxref{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 @ref{Display Tables}.
- If your buffer contains @strong{very} long lines, and you use
+ If your buffer contains @emph{very} long lines, and you use
continuation to display them, just thinking about them can make Emacs
-redisplay slow.
+redisplay slow. The column computation and indentation functions also
+become slow. Then you might find it advisable to set
+@code{cache-long-line-scans} to @code{t}.
@defvar cache-long-line-scans
If this variable is non-@code{nil}, various indentation and motion
-functions, and Emacs redisplay, cache the results of their scans for
-newlines, and consult the cache to avoid rescanning regions of the
-buffer unless they are modified.
+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 newline cache slows down processing of short lines.
+Turning on the cache slows down processing of short lines somewhat.
-This variable is automatically local in every buffer.
+This variable is automatically buffer-local in every buffer.
@end defvar
@node The Echo Area
@end example
@end defun
+@tindex with-temp-message
+@defmac with-temp-message message &rest body
+This construct displays a message in the echo area temporarily, during
+the execution of @var{body}. It displays @var{message}, executes
+@var{body}, then returns the value of the last body form while restoring
+the previous echo area contents.
+@end defmac
+
+@defun message-or-box string &rest arguments
+This function displays a message like @code{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
+@code{last-nonmenu-event} (@pxref{Command Loop Info}) is either
+@code{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 @code{y-or-n-p} uses to make a similar decision; see
+@ref{Yes-or-No Queries}.)
+
+You can force use of the mouse or of the echo area by binding
+@code{last-nonmenu-event} to a suitable value around the call.
+@end defun
+
+@defun message-box string &rest arguments
+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
+support them, then @code{message-box} uses the echo area, like
+@code{message}.
+@end defun
+
+@defun current-message
+@tindex current-message
+This function returns the message currently being displayed in the
+echo area, or @code{nil} if there is none.
+@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
+
+@defvar echo-area-clear-hook
+@tindex echo-area-clear-hook
+This normal hook is run whenever the echo area is cleared---either by
+@code{(message nil)} or for any other reason.
+@end defvar
+
Almost all the messages displayed in the echo area are also recorded
in the @samp{*Messages*} buffer.
@end example
@end defopt
-@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.
+@defvar echo-keystrokes
+This variable determines how much time should elapse before command
+characters echo. Its value must be an integer, which specifies the
+number of seconds to wait before echoing. If the user types a prefix
+key (such as @kbd{C-x}) and then delays this many seconds before
+continuing, the prefix key is echoed in the echo area. (Once echoing
+begins in a key sequence, all subsequent characters in the same key
+sequence are echoed immediately.)
-The value is normally @code{nil}; Lisp programs bind it to @code{t}
-for brief periods of time.
+If the value is zero, then command input is not echoed.
@end defvar
@node Invisible Text
@cindex invisible text
You can make characters @dfn{invisible}, so that they do not appear on
the screen, with the @code{invisible} property. This can be either a
-text property or a property of an overlay.
+text property (@pxref{Text Properties}) or a property of an overlay
+(@pxref{Overlays}).
In the simplest case, any non-@code{nil} @code{invisible} property makes
a character invisible. This is the default case---if you don't alter
the default value of @code{buffer-invisibility-spec}, this is how the
-@code{invisibility} property works. This feature is much like selective
-display (@pxref{Selective Display}), but more general and cleaner.
+@code{invisible} property works.
More generally, you can use the variable @code{buffer-invisibility-spec}
to control which values of the @code{invisible} property make text
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 things to change.
+looking for properties to change.
@defvar buffer-invisibility-spec
This variable specifies which kinds of @code{invisible} properties
non-@code{nil}. This is the default.
@item a list
-Each element of the list makes certain characters invisible.
-Ultimately, a character is invisible if any of the elements of this list
-applies to it. The list can have two kinds of elements:
+Each element of the list specifies a criterion for invisibility; if a
+character's @code{invisible} property fits any one of these criteria,
+the character is invisible. The list can have two kinds of elements:
@table @code
@item @var{atom}
-A character is invisible if its @code{invisible} propery value
+A character is invisible if its @code{invisible} property value
is @var{atom} or if it is a list with @var{atom} as a member.
@item (@var{atom} . t)
-A character is invisible if its @code{invisible} propery value
+A character is invisible if its @code{invisible} property value
is @var{atom} or if it is a list with @var{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.
@end table
@end defvar
+ Two functions are specifically provided for adding elements to
+@code{buffer-invisibility-spec} and removing elements from it.
+
+@defun add-to-invisibility-spec element
+@tindex add-to-invisibility-spec
+Add the element @var{element} to @code{buffer-invisibility-spec}
+(if it is not already present in that list).
+@end defun
+
+@defun remove-from-invisibility-spec element
+@tindex remove-from-invisibility-spec
+Remove the element @var{element} from @code{buffer-invisibility-spec}.
+@end defun
+
+ One convention about the use of @code{buffer-invisibility-spec} is
+that a major mode should use the mode's own name as an element of
+@code{buffer-invisibility-spec} and as the value of the @code{invisible}
+property:
+
+@example
+;; @r{If you want to display an ellipsis:}
+(add-to-invisibility-spec '(my-symbol . t))
+;; @r{If you don't want ellipsis:}
+(add-to-invisibility-spec 'my-symbol)
+
+(overlay-put (make-overlay beginning end)
+ 'invisible 'my-symbol)
+
+;; @r{When done with the overlays:}
+(remove-from-invisibility-spec '(my-symbol . t))
+;; @r{Or respectively:}
+(remove-from-invisibility-spec 'my-symbol)
+@end example
+
+@vindex line-move-ignore-invisible
+ 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
+@code{line-move-ignore-invisible} is non-@code{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-@code{nil}
+@code{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
+@code{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 @code{t} to make the overlay visible, or @code{nil} to
+make it invisible again.
+
@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.
+ @dfn{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. The program controls which lines are hidden by altering
-the text. Outline mode has traditionally used this variant. It has
-been partially replaced by the invisible text feature (@pxref{Invisible
-Text}); there is a new version of Outline mode which uses that instead.
+a Lisp program: it controls which lines are hidden by altering the text.
+The invisible text feature (@pxref{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 as a
+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
@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.
+of a line that follows a control-m is not displayed. This is explicit
+selective display.
@item
If the value of @code{selective-display} is a positive integer, then
@c now. Is it?
@end defvar
- You can do the same job by creating an overlay with a
+ You can do a similar job by creating an overlay with a
@code{before-string} property. @xref{Overlay Properties}.
@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. Nowadays you can do the
-same job by creating an overlay with a @code{before-string} property.
-@xref{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.
@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.
+This function executes @var{forms} while arranging to insert any output
+they print into the buffer named @var{buffer-name}, which is first
+created if necessary, and put into Help mode. Finally, the buffer is
+displayed in some window, but not selected.
+
+If the @var{forms} do not change the major mode in the output buffer, so
+that it is still Help mode at the end of their execution, then
+@code{with-output-to-temp-buffer} makes this buffer read-only at the
+end, and also scans it for function and variable names to make them into
+clickable cross-references.
The string @var{buffer-name} specifies the temporary buffer, which
need not already exist. The argument must be a string, not a buffer.
they are ``output'' in the general sense of the word, are not affected).
@xref{Output Functions}.
+Several hooks are available for customizing the behavior
+of this construct; they are listed below.
+
The value of the last form in @var{forms} is returned.
@example
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.
-In Emacs versions 18 and earlier, this variable was called
-@code{temp-buffer-show-hook}.
+It is a good idea for this function to run @code{temp-buffer-show-hook}
+just as @code{with-output-to-temp-buffer} normally would, inside of
+@code{save-selected-window} and with the chosen window and buffer
+selected.
+@end defvar
+
+@defvar temp-buffer-setup-hook
+@tindex temp-buffer-setup-hook
+This normal hook is run by @code{with-output-to-temp-buffer} before
+evaluating @var{body}. When the hook runs, the help buffer is current.
+This hook is normally set up with a function to put the buffer in Help
+mode.
+@end defvar
+
+@defvar temp-buffer-show-hook
+This normal hook is run by @code{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. This hook is
+normally set up with a function to make the buffer read only, and find
+function names and variable names in it, provided the major mode is
+still Help mode.
@end defvar
@defun momentary-string-display string position &optional char message
The return value of @code{momentary-string-display} is not meaningful.
+If the string @var{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 @code{before-string} property.
+@xref{Overlay Properties}.
+
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}, a
default message says to type @var{char} to continue.
@cindex overlays
You can use @dfn{overlays} to alter the appearance of a buffer's text on
-the screen. 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.
+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.
@menu
* Overlay Properties:: How to read and set properties.
@node Overlay Properties
@subsection Overlay Properties
-Overlay properties are like text properties in some respects, but the
-differences are more important than the similarities. 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 propery changes, overlay changes are not recorded in the
-buffer's undo list.
+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.
+@xref{Text Properties}, for comparison.
@table @code
@item priority
@item category
@kindex category @r{(overlay property)}
If an overlay has a @code{category} property, we call it the
-@dfn{category} of the character. It should be a symbol. The properties
+@dfn{category} of the overlay. It should be a symbol. The properties
of the symbol serve as defaults for the properties of the overlay.
@item face
@kindex face @r{(overlay property)}
-This property controls the font and color of text. Its value is a face
-name or a list of face names. @xref{Faces}, for more information. This
-feature may be temporary; in the future, we may replace it with other
-ways of specifying how to display text.
+This property controls the way text is displayed---for example, which
+font and which colors. Its value is a face name or a list of face
+names. @xref{Faces}, for more information.
+
+If the property value is a list, elements may also have the form
+@code{(foreground-color . @var{color-name})} or @code{(background-color
+. @var{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.
@item mouse-face
@kindex mouse-face @r{(overlay property)}
This property is used instead of @code{face} when the mouse is within
-the range of the overlay. This feature may be temporary, like
-@code{face}.
+the range of the overlay.
@item modification-hooks
@kindex modification-hooks @r{(overlay property)}
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 at the same place.)
+beginning and end are equal.)
@item insert-in-front-hooks
@kindex insert-in-front-hooks @r{(overlay property)}
@item intangible
@kindex intangible @r{(overlay property)}
The @code{intangible} property on an overlay works just like the
-@code{intangible} text propert. @xref{Special Properties}, for details.
+@code{intangible} text property. @xref{Special Properties}, for details.
+
+@item isearch-open-invisible
+This property tells incremental search how to make an invisible overlay
+visible, permanently, if the final match overlaps it. @xref{Invisible
+Text}.
+
+@item isearch-open-invisible-temporary
+This property tells incremental search how to make an invisible overlay
+visible, temporarily, during the search. @xref{Invisible Text}.
@item before-string
@kindex before-string @r{(overlay property)}
@kindex evaporate @r{(overlay property)}
If this property is non-@code{nil}, the overlay is deleted automatically
if it ever becomes empty (i.e., if it spans no characters).
+
+@item local-map
+@cindex keymap of character (and overlays)
+@kindex local-map @r{(overlay property)}
+If this property is non-@code{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. @xref{Active Keymaps}.
@end table
These are the functions for reading and writing the properties of an
This section describes the functions to create, delete and move
overlays, and to examine their contents.
-@defun make-overlay start end &optional buffer
+@defun make-overlay start end &optional buffer front-advance rear-advance
This function creates and returns an overlay that belongs to
@var{buffer} and ranges from @var{start} to @var{end}. Both @var{start}
and @var{end} must specify buffer positions; they may be integers or
markers. If @var{buffer} is omitted, the overlay is created in the
current buffer.
+
+The arguments @var{front-advance} and @var{rear-advance} specify the
+insertion type for the start of the overlay and for the end of the
+overlay. @xref{Marker Insertion Types}.
@end defun
@defun overlay-start overlay
-This function returns the position at which @var{overlay} starts.
+This function returns the position at which @var{overlay} starts,
+as an integer.
@end defun
@defun overlay-end overlay
-This function returns the position at which @var{overlay} ends.
+This function returns the position at which @var{overlay} ends,
+as an integer.
@end defun
@defun overlay-buffer overlay
@defun delete-overlay overlay
This function deletes @var{overlay}. The overlay continues to exist as
-a Lisp object, but ceases to be part of the buffer it belonged to, and
-ceases to have any effect on display.
+a Lisp object, but ceases to be attached to the buffer it belonged to,
+and ceases to have any effect on display.
+
+A deleted overlay is not permanently useless. You can give it
+a new buffer position by calling @code{move-overlay}.
@end defun
@defun move-overlay overlay start end &optional buffer
@var{pos}, and ends after @var{pos}.
@end defun
+@defun overlays-in beg end
+@tindex overlays-in
+This function returns a list of the overlays that overlap the region
+@var{beg} through @var{end}. ``Overlap'' means that at least one
+character is contained within the overlay and also contained within the
+specified region; however, empty overlays are included in the result if
+they are located at @var{beg} or between @var{beg} and @var{end}.
+@end defun
+
@defun next-overlay-change pos
This function returns the buffer position of the next beginning or end
of an overlay, after @var{pos}.
end of an overlay, before @var{pos}.
@end defun
+@node Width
+@section Width
+
+Since not all characters have the same width, these functions let you
+check the width of a character. @xref{Primitive Indent}, and
+@ref{Screen Lines}, for related functions.
+
+@defun char-width char
+@tindex char-width
+This function returns the width in columns of the character @var{char},
+if it were displayed in the current buffer and the selected window.
+@end defun
+
+@defun string-width string
+@tindex string-width
+This function returns the width in columns of the string @var{string},
+if it were displayed in the current buffer and the selected window.
+@end defun
+
+@defun truncate-string-to-width string width &optional start-column padding
+@tindex truncate-string-to-width
+This function returns the part of @var{string} that fits within
+@var{width} columns, as a new string.
+
+If @var{string} does not reach @var{width}, then the result ends where
+@var{string} ends. If one multi-column character in @var{string}
+extends across the column @var{width}, that character is not included in
+the result. Thus, the result can fall short of @var{width} but cannot
+go beyond it.
+
+The optional argument @var{start-column} specifies the starting column.
+If this is non-@code{nil}, then the first @var{start-column} columns of
+the string are omitted from the value. If one multi-column character in
+@var{string} extends across the column @var{start-column}, that
+character is not included.
+
+The optional argument @var{padding}, if non-@code{nil}, is a padding
+character added at the beginning and end of the result string, to extend
+it to exactly @var{width} columns. The padding character is used at the
+end of the result if it falls short of @var{width}. It is also used at
+the beginning of the result if one multi-column character in
+@var{string} extends across the column @var{start-column}.
+
+@example
+(truncate-string-to-width "\tab\t" 12 4)
+ @result{} "ab"
+(truncate-string-to-width "\tab\t" 12 4 ?\ )
+ @result{} " ab "
+@end example
+@end defun
+
@node Faces
@section Faces
@cindex face
A @dfn{face} is a named collection of graphical attributes: font,
-foreground color, background color and optional underlining. Faces
+foreground color, background color, and optional underlining. Faces
control the display of text on the screen.
@cindex face id
-Each face has its own @dfn{face id number} which distinguishes faces at
+Each face has its own @dfn{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.
@menu
* Standard Faces:: The faces Emacs normally comes with.
+* Defining Faces:: How to define a face with @code{defface}.
* Merging Faces:: How Emacs decides which face to use for a character.
* Face Functions:: How to define and examine faces.
@end menu
one.
@end table
+@node Defining Faces
+@subsection Defining Faces
+
+ The way to define a new face is with @code{defface}. This creates a
+kind of customization item (@pxref{Customization}) which the user can
+customize using the Customization buffer (@pxref{Easy Customization,,,
+emacs, The GNU Emacs Manual}).
+
+@defmac defface face spec doc [keyword value]...
+@tindex defface
+Declare @var{face} as a customizable face that defaults according to
+@var{spec}. Do not quote the symbol @var{face}. The argument @var{doc}
+specifies the face documentation.
+
+When @code{defface} executes, it defines the face according to
+@var{spec}, then uses any customizations that were read from the
+@file{.emacs} file to override that specification.
+
+The purpose of @var{spec} is to specify how the face should appear on
+different kinds of terminals. It should be an alist whose elements have
+the form @code{(@var{display} @var{atts})}. The element's @sc{car},
+@var{display}, specifies a class of terminals. The @sc{cdr},
+@var{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 @code{custom-face-attributes}.
+
+The @var{display} part of an element of @var{spec} determines which
+frames the element applies to. If more than one element of @var{spec}
+matches a given frame, the first matching element is the only one used
+for that frame. There are two possibilities for @var{display}:
+
+@table @asis
+@item @code{t}
+This element of @var{spec} matches all frames. Therefore, any
+subsequent elements of @var{spec} are never used. Normally
+@code{t} is used in the last (or only) element of @var{spec}.
+
+@item a list
+If @var{display} is a list, each element should have the form
+@code{(@var{characteristic} @var{value}@dots{})}. Here
+@var{characteristic} specifies a way of classifying frames, and the
+@var{value}s are possible classifications which @var{display} should
+apply to. Here are the possible values of @var{characteristic}:
+
+@table @code
+@item type
+The kind of window system the frame uses---either @code{x}, @code{pc}
+(for the MS-DOS console), @code{w32} (for MS Windows 9X/NT), or
+@code{tty}.
+
+@item class
+What kinds of colors the frame supports---either @code{color},
+@code{grayscale}, or @code{mono}.
+
+@item background
+The kind of background---either @code{light} or @code{dark}.
+@end table
+
+If an element of @var{display} specifies more than one @var{value} for a
+given @var{characteristic}, any of those values is acceptable. If
+@var{display} has more than one element, each element should specify a
+different @var{characteristic}; then @emph{each} characteristic of the
+frame must match one of the @var{value}s specified for it in
+@var{display}.
+@end table
+@end defmac
+
+ Here's how the standard face @code{region} could be defined
+with @code{defface}:
+
+@example
+(defface region
+ ((((class color) (background dark))
+ (:background "blue"))
+ (t (:background "gray")))
+ "Used for displaying the region.")
+@end example
+
+ Internally, @code{defface} uses the symbol property
+@code{face-defface-spec} to record the face attributes specified in
+@code{defface}, @code{saved-face} for the attributes saved by the user
+with the customization buffer, and @code{face-documentation} for the
+documentation string.
+
+@tindex frame-background-mode
+@defopt frame-background-mode
+This option, if non-@code{nil}, specifies the background type to use for
+interpreting face definitions. If it is @code{dark}, then Emacs treats
+all frames as if they had a dark background, regardless of their actual
+background colors. If it is @code{light}, then Emacs treats all frames
+as if they had a light background.
+@end defopt
+
@node Merging Faces
@subsection Merging Faces for Display
@itemize @bullet
@item
-With defaults. Each frame has a @dfn{default face}, whose id number is
-zero, which is used for all text that doesn't somehow specify another
-face.
+With defaults. Each frame has a @dfn{default face}, which is used for
+all text that doesn't somehow specify another face. (We may change this
+in a forthcoming Emacs version to serve as a default for all text.)
@item
With text properties. A character may have a @code{face} property; if so,
properties too; they apply to all the text covered by the overlay.
@item
-With special glyphs. Each glyph can specify a particular face id
+With a region that is active. In Transient Mark mode, the region is
+highlighted with a particular face (see @code{region-face}, below).
+
+@item
+With special glyphs. Each glyph can specify a particular face
number. @xref{Glyphs}.
@end itemize
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.
These functions set the foreground (or background, respectively) color
of face @var{face} to @var{color}. The argument @var{color} should be a
string, the name of a color.
+
+Certain shades of gray are implemented by stipple patterns on
+black-and-white screens.
+@end defun
+
+@defun set-face-stipple face pattern &optional frame
+This function sets the background stipple pattern of face @var{face} to
+@var{pattern}. The argument @var{pattern} should be the name of a
+stipple pattern defined by the X server, or @code{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.
@end defun
@defun set-face-font face font &optional frame
This function sets the font of face @var{face}. The argument @var{font}
-should be a string.
+should be a string, either a valid font name for your system or the name
+of an Emacs fontset (@pxref{Fontsets}). Note that if you set the font
+explicitly, the bold and italic attributes cease to have any effect,
+because the precise font that you specified is always used.
+@end defun
+
+@defun set-face-bold-p face bold-p &optional frame
+@tindex set-face-bold-p
+This function sets the bold attribute of face @var{face}.
+Non-@code{nil} means bold; @code{nil} means non-bold.
+@end defun
+
+@defun set-face-italic-p face italic-p &optional frame
+@tindex set-face-italic-p
+This function sets the italic attribute of face @var{face}.
+Non-@code{nil} means italic; @code{nil} means non-italic.
@end defun
@defun set-face-underline-p face underline-p &optional frame
respectively) of face @var{face}, as a string.
@end defun
+@defun face-stipple face &optional frame
+This function returns the name of the background stipple pattern of face
+@var{face}, or @code{nil} if it doesn't have one.
+@end defun
+
@defun face-font face &optional frame
This function returns the name of the font of face @var{face}.
@end defun
+@defun face-bold-p face &optional frame
+@tindex face-bold-p
+This function returns the bold attribute of face @var{face}.
+@end defun
+
+@defun face-italic-p face &optional frame
+@tindex face-italic-p
+This function returns the italic attribute of face @var{face}.
+@end defun
+
@defun face-underline-p face &optional frame
This function returns the underline attribute of face @var{face}.
@end defun
-@defun face-id-number face
-This function returns the face id number of face @var{face}.
+@defun face-id face
+This function returns the face number of face @var{face}.
+@end defun
+
+@defun face-documentation face
+@tindex face-documentation
+This function returns the documentation string of face @var{face}, or
+@code{nil} if none was specified for it.
@end defun
@defun face-equal face1 face2 &optional frame
@end defun
@defvar region-face
-This variable's value specifies the face id to use to display characters
+This variable's value specifies the face number to use to display characters
in the region when it is active (in Transient Mark mode only). The face
thus specified takes precedence over all faces that come from text
properties and overlays, for characters in the region. @xref{The Mark},
for more information about Transient Mark mode.
-Normally, the value is the id number of the face named @code{region}.
+Normally, the value is the face number of the face named @code{region}.
@end defvar
+@tindex frame-update-face-colors
+@defun frame-update-face-colors frame
+This function updates the way faces display on @var{frame}, for a change
+in @var{frame}'s foreground or background color.
+@end defun
+
@node Blinking
@section Blinking Parentheses
@cindex parenthesis matching
This section describes the mechanism by which Emacs 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 character 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
+@defopt blink-matching-paren
If this variable is @code{nil}, then @code{blink-matching-open} does
nothing.
-@end defvar
+@end defopt
-@defvar blink-matching-paren-distance
+@defopt blink-matching-paren-distance
This variable specifies the maximum distance to scan for a matching
parenthesis before giving up.
-@end defvar
+@end defopt
+
+@defopt blink-matching-delay
+This variable specifies the number of seconds for the cursor to remain
+at the matching parenthesis. A fraction of a second often gives
+good results, but the default is 1, which works on all systems.
+@end defopt
-@defun blink-matching-open
+@deffn Command 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
(blink-matching-open)))
@end group
@end smallexample
-@end defun
+@end deffn
@node Inverse Video
@section Inverse Video
@defopt mode-line-inverse-video
This variable controls the use of inverse video for mode lines. If it
-is non-@code{nil}, then mode lines are displayed in inverse video (under
-X, this uses the face named @code{modeline}, which you can set as you
-wish). Otherwise, mode lines are displayed normally, just like text.
-The default is @code{t}.
+is non-@code{nil}, then mode lines are displayed in inverse video.
+Otherwise, mode lines are displayed normally, just like text. The
+default is @code{t}.
+
+For window frames, this displays mode lines using the face named
+@code{modeline}, which is normally the inverse of the default face
+unless you change it.
@end defopt
@node Usual Display
@item
Character codes 128 through 255 map to sequences of four glyphs, where
the first glyph is the @sc{ASCII} code for @samp{\}, and the others are
-digit characters representing the code in octal. (A display table can
-specify a glyph to use instead of @samp{\}.)
+digit characters representing the character code in octal. (A display
+table can specify a glyph to use instead of @samp{\}.)
+
+@item
+Multibyte character codes above 256 are displayed as themselves, or as a
+question mark or empty box if the terminal cannot display that
+character.
@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.
+specify the characters for which you want special behavior.
+
+ These display rules apply to carriage return (character code 13), when
+it appears in the buffer. But that character may not appear in the
+buffer where you expect it, if it was eliminated as part of end-of-line
+conversion (@xref{Coding System Basics}).
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.
+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
+@code{force-mode-line-update} (@pxref{Mode Line Format}).
@defopt ctl-arrow
@cindex control characters in display
@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
+that this feature is completely independent of the user-settable tab
stops used by the command @code{tab-to-tab-stop}. @xref{Indent Tabs}.
@end defopt
@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 @sc{ASCII}
-character set.
+You can use the @dfn{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 @sc{ASCII} character
+set.
The display table maps each character code into a sequence of
@dfn{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 @dfn{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
+@code{force-mode-line-update} (@pxref{Mode Line Format}).
+
@menu
* Display Table Format:: What a display table consists of.
* Active Display Table:: How Emacs selects a display table to use.
* Glyphs:: How to define a glyph, and what glyphs mean.
-* ISO Latin 1:: How to use display tables
- to support the ISO Latin 1 character set.
@end menu
@node Display Table Format
@subsection Display Table Format
- A display table is actually an array of 262 elements.
+ A display table is actually a char-table (@pxref{Char-Tables}) with
+@code{display-table} as its subtype.
@defun make-display-table
This creates and returns a display table. The table initially has
@code{nil} in all elements.
@end defun
- The first 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} 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 (@pxref{Usual Display}).
+ 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
+(@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.''
- The remaining six elements of a display table serve special purposes,
-and @code{nil} means use the default stated below.
+ The display table also has six ``extra slots'' which serve special
+purposes. Here is a table of their meanings; @code{nil} in any slot
+means to use the default for that slot, as stated below.
@table @asis
-@item 256
+@item 0
The glyph for the end of a truncated screen line (the default for this
is @samp{$}). @xref{Glyphs}.
-@item 257
+@item 1
The glyph for the end of a continued line (the default is @samp{\}).
-@item 258
+@item 2
The glyph for indicating a character displayed as an octal character
code (the default is @samp{\}).
-@item 259
+@item 3
The glyph for indicating a control character (the default is @samp{^}).
-@item 260
+@item 4
A vector of glyphs for indicating the presence of invisible lines (the
default is @samp{...}). @xref{Selective Display}.
-@item 261
+@item 5
The glyph used to draw the border between side-by-side windows (the
default is @samp{|}). @xref{Splitting Windows}.
@end table
(aset disptab 127 (vector ?^ ??)))
@end example
+@defun display-table-slot display-table slot
+@tindex display-table-slot
+This function returns the value of the extra slot @var{slot} of
+@var{display-table}. The argument @var{slot} may be a number from 0 to
+5 inclusive, or a slot name (symbol). Valid symbols are
+@code{truncation}, @code{wrap}, @code{escape}, @code{control},
+@code{selective-display}, and @code{vertical-border}.
+@end defun
+
+@defun set-display-table-slot display-table slot value
+@tindex set-display-table-slot
+This function stores @var{value} in the extra slot @var{slot} of
+@var{display-table}. The argument @var{slot} may be a number from 0 to
+5 inclusive, or a slot name (symbol). Valid symbols are
+@code{truncation}, @code{wrap}, @code{escape}, @code{control},
+@code{selective-display}, and @code{vertical-border}.
+@end defun
+
@node Active Display Table
@subsection Active Display Table
@cindex active display table
@end defun
@defvar buffer-display-table
-This variable is automatically local in all buffers; its value in a
-particular buffer is the display table for that buffer, or @code{nil} if
-the buffer does not have an assigned display table.
+This variable is automatically buffer-local in all buffers; its value in
+a particular buffer specifies the display table for that buffer. If it
+is @code{nil}, that means the buffer does not have an assigned display
+table.
@end defvar
@defvar standard-display-table
@end defvar
If there is no display table to use for a particular window---that is,
-if the window has none, its buffer has none, and
-@code{standard-display-table} has none---then Emacs uses the usual
+if the window specifies none, its buffer specifies none, and
+@code{standard-display-table} is @code{nil}---then Emacs uses the usual
display conventions for all character codes in that window. @xref{Usual
Display}.
Here are the possible types of elements in the glyph table:
-@table @var
-@item string
+@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 under X.
+but not under a window system.
-@item integer
-Define this glyph code as an alias for code @var{integer}. You can use
-an alias to specify a face code for the glyph; see below.
+@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; see below.
@item @code{nil}
-This glyph is simple. On an ordinary terminal, the glyph code mod 256
-is the character to output. With X, the glyph code mod 256 is the
-character to output, and the glyph code divided by 256 specifies the
-@dfn{face id number} to use while outputting it. @xref{Faces}.
+This glyph is simple. On an ordinary terminal, the glyph code mod
+524288 is the character to output. In a window system, the glyph code
+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
+@ifinfo
+2**19.)
+@end ifinfo
+@tex
+$2^{19}$.)
+@end tex
+@xref{Faces}.
@end table
If a glyph code is greater than or equal to the length of the glyph
table, that code is automatically simple.
-@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 @sc{ASCII}, you can load the
-file @file{iso-ascii} to set up a display table that displays the other
-ISO characters as explanatory sequences of @sc{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.
-
@node Beeping
@section Beeping
@cindex beeping
@cindex bell
- You can make Emacs ring a 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 beeping alone
-when signaling an error is appropriate. (@xref{Errors}.)
+ 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. (@xref{Errors}.)
-@defun ding &optional dont-terminate
+@defun ding &optional do-not-terminate
@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}.
+@var{do-not-terminate} is non-@code{nil}.
@end defun
-@defun beep &optional dont-terminate
+@defun beep &optional do-not-terminate
This is a synonym for @code{ding}.
@end defun
-@defvar visible-bell
+@defopt visible-bell
This variable determines whether Emacs should flash the screen to
represent a bell. Non-@code{nil} means yes, @code{nil} means no. This
-is effective under X windows, and on a character-only terminal provided
-the terminal's Termcap entry defines the visible bell capability
-(@samp{vb}).
+is effective on a window system, and on a character-only terminal
+provided the terminal's Termcap entry defines the visible bell
+capability (@samp{vb}).
+@end defopt
+
+@defvar ring-bell-function
+@tindex ring-bell-function
+If this is non-@code{nil}, it specifies how Emacs should ``ring the
+bell.'' Its value should be a function of no arguments.
@end defvar
@node Window Systems
concerned; the individual Emacs windows are not known to X at all.
@defvar window-system
-@cindex X Window System
This variable tells Lisp programs what window system Emacs is running
-under. Its value should be a symbol such as @code{x} (if Emacs is
-running under X) or @code{nil} (if Emacs is running on an ordinary
-terminal).
-@end defvar
+under. The possible values are
-@defvar window-system-version
-This variable distinguishes between different versions of the X Window
-System. Its value is 10 or 11 when using X; @code{nil} otherwise.
+@table @code
+@item x
+@cindex X Window System
+Emacs is displaying using X.
+@item pc
+Emacs is displaying using MSDOS.
+@item w32
+Emacs is displaying using Windows NT or Windows 95.
+@item nil
+Emacs is using a character-based terminal.
+@end table
@end defvar
@defvar window-setup-hook
-This variable is a normal hook which Emacs runs after loading your
-@file{.emacs} file and the default initialization file (if any), after
-loading terminal-specific Lisp code, and after running the hook
+This variable is a normal hook which Emacs runs after handling the
+initialization files. Emacs runs this hook after it has completed
+loading your @file{.emacs} file, the default initialization file (if
+any), and the terminal-specific Lisp code, and running the hook
@code{term-setup-hook}.
This hook is used for internal purposes: setting up communication with
HCoop / bpt / emacs.git / blobdiff