X-Git-Url: https://code.delx.au/gnu-emacs/blobdiff_plain/2811080bdda0153dacff30604f78b631b3a13cce..f79bdb3aa2f26d28e775af39417981c6dcb0484c:/lispref/display.texi diff --git a/lispref/display.texi b/lispref/display.texi index 9748855ec5..bccab7323e 100644 --- a/lispref/display.texi +++ b/lispref/display.texi @@ -1,7 +1,7 @@ @c -*-texinfo-*- @c This is part of the GNU Emacs Lisp Reference Manual. -@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2000, 2001 -@c Free Software Foundation, Inc. +@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2000, 2001, +@c 2002, 2005 Free Software Foundation, Inc. @c See the file elisp.texi for copying conditions. @setfilename ../info/display @node Display, Calendar, Processes, Top @@ -15,20 +15,29 @@ that Emacs presents to the user. * Forcing Redisplay:: Forcing redisplay. * Truncation:: Folding or wrapping long text lines. * The Echo Area:: Where messages are displayed. +* Warnings:: Displaying warning messages for the user. +* Progress:: Informing user about progress of a long operation. * Invisible Text:: Hiding part of the buffer text. * Selective Display:: Hiding part of the buffer text (the old way). * 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. +* Overlays:: Use overlays to highlight parts of the buffer. * Width:: How wide a character or string is on the screen. -* Faces:: A face defines a graphics style for text characters: +* Line Height:: Controlling the height of lines. +* Faces:: A face defines a graphics style for text characters: font, colors, etc. +* Fringes:: Controlling window fringes. +* Fringe Bitmaps:: Displaying bitmaps in the window fringes. +* Customizing Bitmaps:: Specifying your own bitmaps to use in the fringes. +* Scroll Bars:: Controlling vertical scroll bars. +* Pointer Shape:: Controlling the mouse pointer shape. * Display Property:: Enabling special display features. * Images:: Displaying images in Emacs buffers. +* Buttons:: Adding clickable buttons to Emacs buffers. * Blinking:: How Emacs shows the matching open parenthesis. -* Inverse Video:: Specifying how the screen looks. -* Usual Display:: The usual conventions for displaying nonprinting chars. -* Display Tables:: How to specify other conventions. +* Inverse Video:: Specifying how the screen looks. +* Usual Display:: The usual conventions for displaying nonprinting chars. +* Display Tables:: How to specify other conventions. * Beeping:: Audible signal to the user. * Window Systems:: Which window system is being used. @end menu @@ -50,6 +59,17 @@ Even more powerful is @code{redraw-display}: This function clears and redisplays all visible frames. @end deffn + This function forces certain windows to be redisplayed +but does not clear them. + +@defun force-window-update object +This function forces redisplay of some or all windows. If +@var{object} is a window, it forces redisplay of that window. If +@var{object} is a buffer or buffer name, it forces redisplay of all +windows displaying that buffer. If @var{object} is @code{nil}, it +forces redisplay of all windows. +@end defun + 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 @@ -111,10 +131,9 @@ 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}.) -@cindex fringes, and line continuation/truncation indicators On a windowed display, the @samp{$} and @samp{\} indicators are -replaced with graphics bitmaps displayed on the thin areas right near -the window edges, called the @dfn{fringes}. +replaced with graphics bitmaps displayed in the window fringes +(@pxref{Fringes}). Note that continuation is different from filling; continuation happens on the screen only, not in the buffer contents, and it breaks a line @@ -327,6 +346,309 @@ sequence are echoed immediately.) If the value is zero, then command input is not echoed. @end defvar +@node Warnings +@section Reporting Warnings +@cindex warnings + + @dfn{Warnings} are a facility for a program to inform the user of a +possible problem, but continue running. + +@menu +* Warning Basics:: Warnings concepts and functions to report them. +* Warning Variables:: Variables programs bind to customize their warnings. +* Warning Options:: Variables users set to control display of warnings. +@end menu + +@node Warning Basics +@subsection Warning Basics +@cindex severity level + + Every warning has a textual message, which explains the problem for +the user, and a @dfn{severity level} which is a symbol. Here are the +possible severity levels, in order of decreasing severity, and their +meanings: + +@table @code +@item :emergency +A problem that will seriously impair Emacs operation soon +if you do not attend to it promptly. +@item :error +A report of data or circumstances that are inherently wrong. +@item :warning +A report of data or circumstances that are not inherently wrong, but +raise suspicion of a possible problem. +@item :debug +A report of information that may be useful if you are debugging. +@end table + + When your program encounters invalid input data, it can either +signal a Lisp error by calling @code{error} or @code{signal} or report +a warning with severity @code{:error}. Signaling a Lisp error is the +easiest thing to do, but it means the program cannot continue +processing. If you want to take the trouble to implement a way to +continue processing despite the bad data, then reporting a warning of +severity @code{:error} is the right way to inform the user of the +problem. For instance, the Emacs Lisp byte compiler can report an +error that way and continue compiling other functions. (If the +program signals a Lisp error and then handles it with +@code{condition-case}, the user won't see the error message; it could +show the message to the user by reporting it as a warning.) + +@cindex warning type + Each warning has a @dfn{warning type} to classify it. The type is a +list of symbols. The first symbol should be the custom group that you +use for the program's user options. For example, byte compiler +warnings use the warning type @code{(bytecomp)}. You can also +subcategorize the warnings, if you wish, by using more symbols in the +list. + +@defun display-warning type message &optional level buffer-name +This function reports a warning, using @var{message} as the message +and @var{type} as the warning type. @var{level} should be the +severity level, with @code{:warning} being the default. + +@var{buffer-name}, if non-@code{nil}, specifies the name of the buffer +for logging the warning. By default, it is @samp{*Warnings*}. +@end defun + +@defun lwarn type level message &rest args +This function reports a warning using the value of @code{(format +@var{message} @var{args}...)} as the message. In other respects it is +equivalent to @code{display-warning}. +@end defun + +@defun warn message &rest args +This function reports a warning using the value of @code{(format +@var{message} @var{args}...)} as the message, @code{(emacs)} as the +type, and @code{:warning} as the severity level. It exists for +compatibility only; we recommend not using it, because you should +specify a specific warning type. +@end defun + +@node Warning Variables +@subsection Warning Variables + + Programs can customize how their warnings appear by binding +the variables described in this section. + +@defvar warning-levels +This list defines the meaning and severity order of the warning +severity levels. Each element defines one severity level, +and they are arranged in order of decreasing severity. + +Each element has the form @code{(@var{level} @var{string} +@var{function})}, where @var{level} is the severity level it defines. +@var{string} specifies the textual description of this level. +@var{string} should use @samp{%s} to specify where to put the warning +type information, or it can omit the @samp{%s} so as not to include +that information. + +The optional @var{function}, if non-@code{nil}, is a function to call +with no arguments, to get the user's attention. + +Normally you should not change the value of this variable. +@end defvar + +@defvar warning-prefix-function +If non-@code{nil}, the value is a function to generate prefix text for +warnings. Programs can bind the variable to a suitable function. +@code{display-warning} calls this function with the warnings buffer +current, and the function can insert text in it. That text becomes +the beginning of the warning message. + +The function is called with two arguments, the severity level and its +entry in @code{warning-levels}. It should return a list to use as the +entry (this value need not be an actual member of +@code{warning-levels}). By constructing this value, the function can +change the severity of the warning, or specify different handling for +a given severity level. + +If the variable's value is @code{nil} then there is no function +to call. +@end defvar + +@defvar warning-series +Programs can bind this variable to @code{t} to say that the next +warning should begin a series. When several warnings form a series, +that means to leave point on the first warning of the series, rather +than keep moving it for each warning so that it appears on the last one. +The series ends when the local binding is unbound and +@code{warning-series} becomes @code{nil} again. + +The value can also be a symbol with a function definition. That is +equivalent to @code{t}, except that the next warning will also call +the function with no arguments with the warnings buffer current. The +function can insert text which will serve as a header for the series +of warnings. + +Once a series has begun, the value is a marker which points to the +buffer position in the warnings buffer of the start of the series. + +The variable's normal value is @code{nil}, which means to handle +each warning separately. +@end defvar + +@defvar warning-fill-prefix +When this variable is non-@code{nil}, it specifies a fill prefix to +use for filling each warning's text. +@end defvar + +@defvar warning-type-format +This variable specifies the format for displaying the warning type +in the warning message. The result of formatting the type this way +gets included in the message under the control of the string in the +entry in @code{warning-levels}. The default value is @code{" (%s)"}. +If you bind it to @code{""} then the warning type won't appear at +all. +@end defvar + +@node Warning Options +@subsection Warning Options + + These variables are used by users to control what happens +when a Lisp program reports a warning. + +@defopt warning-minimum-level +This user option specifies the minimum severity level that should be +shown immediately to the user. The default is @code{:warning}, which +means to immediately display all warnings except @code{:debug} +warnings. +@end defopt + +@defopt warning-minimum-log-level +This user option specifies the minimum severity level that should be +logged in the warnings buffer. The default is @code{:warning}, which +means to log all warnings except @code{:debug} warnings. +@end defopt + +@defopt warning-suppress-types +This list specifies which warning types should not be displayed +immediately for the user. Each element of the list should be a list +of symbols. If its elements match the first elements in a warning +type, then that warning is not displayed immediately. +@end defopt + +@defopt warning-suppress-log-types +This list specifies which warning types should not be logged in the +warnings buffer. Each element of the list should be a list of +symbols. If it matches the first few elements in a warning type, then +that warning is not logged. +@end defopt + +@node Progress +@section Reporting Operation Progress +@cindex progress reporting + +When an operation can take a while to finish, you should inform the +user about the progress it makes. This way the user can estimate +remaining time and clearly see that Emacs is busy working, not hung. + +Functions listed in this section provide simple and efficient way of +reporting operation progress. Here is a working example that does +nothing useful: + +@example +(let ((progress-reporter + (make-progress-reporter "Collecting some mana for Emacs..." + 0 500))) + (dotimes (k 500) + (sit-for 0.01) + (progress-reporter-update progress-reporter k)) + (progress-reporter-done progress-reporter)) +@end example + +@defun make-progress-reporter message min-value max-value &optional current-value min-change min-time +This function creates a progress reporter---the object you will use as +an argument for all other functions listed here. The idea is to +precompute as much data as possible to make progress reporting very +fast. + +The @var{message} will be displayed in the echo area, followed by +progress percentage. @var{message} is treated as a simple string. If +you need it to depend on a filename, for instance, use @code{format} +before calling this function. + +@var{min-value} and @var{max-value} arguments stand for starting and +final states of your operation. For instance, if you scan a buffer, +they should be the results of @code{point-min} and @code{point-max} +correspondingly. It is required that @var{max-value} is greater than +@var{min-value}. If you create progress reporter when some part of +the operation has already been completed, then specify +@var{current-value} argument. But normally you should omit it or set +it to @code{nil}---it will default to @var{min-value} then. + +Remaining arguments control the rate of echo area updates. Progress +reporter will wait for at least @var{min-change} more percents of the +operation to be completed before printing next message. +@var{min-time} specifies the minimum time in seconds to pass between +successive prints. It can be fractional. Depending on Emacs and +system capabilities, progress reporter may or may not respect this +last argument or do it with varying precision. Default value for +@var{min-change} is 1 (one percent), for @var{min-time}---0.2 +(seconds.) + +This function calls @code{progress-reporter-update}, so the first +message is printed immediately. +@end defun + +@defun progress-reporter-update reporter value +This function does the main work of reporting progress of your +operation. It print the message of @var{reporter} followed by +progress percentage determined by @var{value}. If percentage is zero, +then it is not printed at all. + +@var{reporter} must be the result of a call to +@code{make-progress-reporter}. @var{value} specifies the current +state of your operation and must be between @var{min-value} and +@var{max-value} (inclusive) as passed to +@code{make-progress-reporter}. For instance, if you scan a buffer, +then @var{value} should be the result of a call to @code{point}. + +This function respects @var{min-change} and @var{min-time} as passed +to @code{make-progress-reporter} and so does not output new messages +on every invocation. It is thus very fast and normally you should not +try to reduce the number of calls to it: resulting overhead will most +likely negate your effort. +@end defun + +@defun progress-reporter-force-update reporter value &optional new-message +This function is similar to @code{progress-reporter-update} except +that it prints a message in the echo area unconditionally. + +The first two arguments have the same meaning as for +@code{progress-reporter-update}. Optional @var{new-message} allows +you to change the message of the @var{reporter}. Since this functions +always updates the echo area, such a change will be immediately +presented to the user. +@end defun + +@defun progress-reporter-done reporter +This function should be called when the operation is finished. It +prints the message of @var{reporter} followed by word ``done'' in the +echo area. + +You should always call this function and not hope for +@code{progress-reporter-update} to print ``100%.'' Firstly, it may +never print it, there are many good reasons for this not to happen. +Secondly, ``done'' is more explicit. +@end defun + +@defmac dotimes-with-progress-reporter (var count [result]) message body... +This is a convenience macro that works the same way as @code{dotimes} +does, but also reports loop progress using the functions described +above. It allows you to save some typing. + +You can rewrite the example in the beginning of this node using +this macro this way: + +@example +(dotimes-with-progress-reporter + (k 500) + "Collecting some mana for Emacs..." + (sit-for 0.01)) +@end example +@end defmac + @node Invisible Text @section Invisible Text @@ -339,7 +661,9 @@ text property (@pxref{Text Properties}) or a property of an overlay 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{invisible} property works. +@code{invisible} property works. You should normally use @code{t} +as the value of the @code{invisible} property if you don't plan +to set @code{buffer-invisibility-spec} yourself. More generally, you can use the variable @code{buffer-invisibility-spec} to control which values of the @code{invisible} property make text @@ -357,7 +681,8 @@ the buffer looking for properties to change. @defvar buffer-invisibility-spec This variable specifies which kinds of @code{invisible} properties -actually make a character invisible. +actually make a character invisible. Setting this variable makes it +buffer-local. @table @asis @item @code{t} @@ -387,25 +712,29 @@ by a visible newline, it displays an ellipsis. @code{buffer-invisibility-spec} and removing elements from it. @defun add-to-invisibility-spec element -Add the element @var{element} to @code{buffer-invisibility-spec} -(if it is not already present in that list). +This function adds the element @var{element} to +@code{buffer-invisibility-spec} (if it is not already present in that +list). If @code{buffer-invisibility-spec} was @code{t}, it changes to +a list, @code{(t)}, so that text whose @code{invisible} property +is @code{t} remains invisible. @end defun @defun remove-from-invisibility-spec element -Remove the element @var{element} from @code{buffer-invisibility-spec}. -This does nothing if @var{element} is not in the list. +This removes the element @var{element} from +@code{buffer-invisibility-spec}. This does nothing if @var{element} +is not in the list. @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: + A convention for 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)) +(add-to-invisibility-spec '(my-symbol . t)) ;; @r{If you don't want ellipsis:} -(add-to-invisibility-spec 'my-symbol) +(add-to-invisibility-spec 'my-symbol) (overlay-put (make-overlay beginning end) 'invisible 'my-symbol) @@ -417,12 +746,22 @@ property: @end example @vindex line-move-ignore-invisible - Ordinarily, commands that operate on text or move point do not care + Ordinarily, functions 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. + However, if a command ends with point inside or immediately after +invisible text, the main editing loop moves point further forward or +further backward (in the same direction that the command already moved +it) until that condition is no longer true. Thus, if the command +moved point back into an invisible range, Emacs moves point back to +the beginning of that range, following the previous visible character. +If the command moved point forward into an invisible range, Emacs +moves point forward past the first visible character that follows the +invisible text. + 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} @@ -477,7 +816,7 @@ effect is seen only within Emacs. @defvar selective-display This buffer-local variable enables selective display. This means that -lines, or portions of lines, may be made invisible. +lines, or portions of lines, may be made invisible. @itemize @bullet @item @@ -566,7 +905,6 @@ interface to debuggers, the overlay arrow indicates the line of code about to be executed. @defvar overlay-arrow-string -@cindex fringe, and overlay arrow display This variable holds the string to display to call attention to a particular line, or @code{nil} if the arrow feature is not in use. On a graphical display the contents of the string are ignored; instead a @@ -606,11 +944,13 @@ 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 +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. +end, and also scans it for function and variable names to make them +into clickable cross-references. @xref{Docstring hyperlinks, , Tips +for Documentation Strings}, in particular the item on hyperlinks in +documentation strings, for more details. The string @var{buffer-name} specifies the temporary buffer, which need not already exist. The argument must be a string, not a buffer. @@ -746,8 +1086,14 @@ 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. +An overlays uses markers to record its beginning and end; thus, +editing the text of the buffer adjusts the beginning and end of each +overlay so that it stays with the text. When you create the overlay, +you can specify whether text inserted at the beginning should be +inside the overlay or outside, and likewise for the end of the overlay. + @menu -* Overlay Properties:: How to read and set properties. +* Overlay Properties:: How to read and set properties. What properties do to the screen display. * Managing Overlays:: Creating and moving overlays. * Finding Overlays:: Searching for overlays. @@ -781,6 +1127,10 @@ is @code{nil}. @defun overlay-put overlay prop value This function sets the value of property @var{prop} recorded in @var{overlay} to @var{value}. It returns @var{value}. +@end defun + +@defun overlay-properties overlay +This returns a copy of the property list of @var{overlay}. @end defun See also the function @code{get-char-property} which checks both @@ -793,12 +1143,14 @@ of them: @table @code @item priority @kindex priority @r{(overlay property)} -This property's value (which should be a nonnegative number) determines -the priority of the overlay. The priority matters when two or more -overlays cover the same character and both specify a face for display; -the one whose @code{priority} value is larger takes priority over the -other, and its face attributes override the face attributes of the lower -priority overlay. +This property's value (which should be a nonnegative integer number) +determines the priority of the overlay. The priority matters when two +or more overlays cover the same character and both specify the same +property; the one whose @code{priority} value is larger takes priority +over the other. For the @code{face} property, the higher priority +value does not completely replace the other; instead, its face +attributes override the face attributes of the lower priority +@code{face} property. Currently, all overlays take priority over text properties. Please avoid using negative priority values, as we have not yet decided just @@ -857,11 +1209,11 @@ or shorter, higher or lower, wider or narrower, or replaced with an image. @xref{Display Property}. @item help-echo -@kindex help-echo @r{(text property)} +@kindex help-echo @r{(overlay property)} If an overlay has a @code{help-echo} property, then when you move the mouse onto the text in the overlay, Emacs displays a help string in the echo area, or in the tooltip window. For details see @ref{Text -help-echo}. This feature is available starting in Emacs 21. +help-echo}. @item modification-hooks @kindex modification-hooks @r{(overlay property)} @@ -932,7 +1284,9 @@ sense---only on the screen. @item evaporate @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). +if it becomes empty (i.e., if its length becomes zero). If you give +an empty overlay a non-@code{nil} @code{evaporate} property, that deletes +it immediately. @item local-map @cindex keymap of character (and overlays) @@ -954,6 +1308,10 @@ property) rather than replacing it. This section describes the functions to create, delete and move overlays, and to examine their contents. +@defun overlayp object +This function returns @code{t} if @var{object} is an overlay. +@end defun + @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} @@ -963,7 +1321,11 @@ 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, respectively. @xref{Marker Insertion Types}. +overlay, respectively. @xref{Marker Insertion Types}. If +@var{front-advance} is non-@code{nil}, text inserted at the beginning +of the overlay is excluded from the overlay. If @var{read-advance} is +non-@code{nil}, text inserted at the beginning of the overlay is +included in the overlay. @end defun @defun overlay-start overlay @@ -1160,11 +1522,107 @@ the beginning of the result if one multi-column character in @example (truncate-string-to-width "\tab\t" 12 4) @result{} "ab" -(truncate-string-to-width "\tab\t" 12 4 ?\ ) +(truncate-string-to-width "\tab\t" 12 4 ?\s) @result{} " ab " @end example @end defun +@node Line Height +@section Line Height +@cindex line height + + The total height of each display line consists of the height of the +contents of the line, and additional vertical line spacing below the +display row. + + The height of the line contents is normally determined from the +maximum height of any character or image on that display line, +including the final newline if there is one. (A line that is +continued doesn't include a final newline.) In the most common case, +the line height equals the height of the default frame font. + + There are several ways to explicitly control or change the line +height, either by specifying an absolute height for the display line, +or by adding additional vertical space below one or all lines. + +@kindex line-height @r{(text property)} + A newline can have a @code{line-height} text or overlay property +that controls the total height of the display line ending in that +newline. + + If the property value is a list @code{(@var{height} @var{total})}, +then @var{height} is used as the actual property value for the +@code{line-height}, and @var{total} specifies the total displayed +height of the line, so the line spacing added below the line equals +the @var{total} height minus the actual line height. In this case, +the other ways to specify the line spacing are ignored. + + If the property value is @code{t}, the displayed height of the +line is exactly what its contents demand; no line-spacing is added. +This case is useful for tiling small images or image slices without +adding blank areas between the images. + + If the property value is not @code{t}, it is a height spec. A height +spec stands for a numeric height value; this heigh spec specifies the +actual line height, @var{line-height}. There are several ways to +write a height spec; here's how each of them translates into a numeric +height: + +@table @code +@item @var{integer} +If the height spec is a positive integer, the height value is that integer. +@item @var{float} +If the height spec is a float, @var{float}, the numeric height value +is @var{float} times the frame's default line height. +@item (@var{face} . @var{ratio}) +If the height spec is a cons of the format shown, the numeric height +is @var{ratio} times the height of face @var{face}. @var{ratio} can +be any type of number, or @code{nil} which means a ratio of 1. +If @var{face} is @code{t}, it refers to the current face. +@item (@code{nil} . @var{ratio}) +If the height spec is a cons of the format shown, the numeric height +is @var{ratio} times the height of the contents of the line. +@end table + + Thus, any valid non-@code{t} property value specifies a height in pixels, +@var{line-height}, one way or another. If the line contents' height +is less than @var{line-height}, Emacs adds extra vertical space above +the line to achieve the total height @var{line-height}. Otherwise, +@var{line-height} has no effect. + + If you don't specify the @code{line-height} propery, the line's +height consists of the contents' height plus the line spacing. +There are several ways to specify the line spacing for different +parts of Emacs text. + +@vindex default-line-spacing + You can specify the line spacing for all lines in a frame with the +@code{line-spacing} frame parameter, @xref{Window Frame Parameters}. +However, if the variable @code{default-line-spacing} is +non-@code{nil}, it overrides the frame's @code{line-spacing} +parameter. An integer value specifies the number of pixels put below +lines on window systems. A floating point number specifies the +spacing relative to the frame's default line height. + +@vindex line-spacing + You can specify the line spacing for all lines in a buffer via the +buffer-local @code{line-spacing} variable. An integer value specifies +the number of pixels put below lines on window systems. A floating +point number specifies the spacing relative to the default frame line +height. This overrides line spacings specified for the frame. + +@kindex line-spacing @r{(text property)} + Finally, a newline can have a @code{line-spacing} text or overlay +property that controls the height of the display line ending with that +newline. The property value overrides the default frame line spacing +and the buffer local @code{line-spacing} variable. + + One way or another, these mechanisms specify a Lisp value for the +spacing of each line. The value is a height spec, and it translates +into a Lisp value as described above. However, in this case the +numeric height value specifies the line spacing, rather than the line +height. + @node Faces @section Faces @cindex faces @@ -1193,10 +1651,10 @@ face name a special meaning in one frame if you wish. * Standard Faces:: The faces Emacs normally comes with. * Defining Faces:: How to define a face with @code{defface}. * Face Attributes:: What is in a face? -* Attribute Functions:: Functions to examine and set face attributes. -* Merging Faces:: How Emacs combines the faces specified for a character. +* Attribute Functions:: Functions to examine and set face attributes. +* Displaying Faces:: How Emacs combines the faces specified for a character. * Font Selection:: Finding the best available font for a face. -* Face Functions:: How to define and examine faces. +* Face Functions:: How to define and examine faces. * Auto Faces:: Hook for automatic face assignment. * Font Lookup:: Looking up the names of available fonts and information about them. @@ -1218,15 +1676,21 @@ This face is used for ordinary text. @item mode-line @kindex mode-line @r{(face name)} -This face is used for mode lines, and for menu bars when toolkit menus -are not used---but only if @code{mode-line-inverse-video} is -non-@code{nil}. +This face is used for the mode line of the selected window, and for +menu bars when toolkit menus are not used---but only if +@code{mode-line-inverse-video} is non-@code{nil}. @item modeline @kindex modeline @r{(face name)} This is an alias for the @code{mode-line} face, for compatibility with old Emacs versions. +@item mode-line-inactive +@kindex mode-line-inactive @r{(face name)} +This face is used for mode lines of non-selected windows. +This face inherits from @code{mode-line}, so changes +in that face affect all windows. + @item header-line @kindex header-line @r{(face name)} This face is used for the header lines of windows that have them. @@ -1237,7 +1701,7 @@ font. (This works only on certain systems.) @item fringe @kindex fringe @r{(face name)} -This face controls the colors of window fringes, the thin areas on +This face controls the default colors of window fringes, the thin areas on either side that are used to display continuation and truncation glyphs. @item minibuffer-prompt @@ -1324,7 +1788,7 @@ 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]... +@defmac defface face spec doc [keyword value]... This declares @var{face} as a customizable face that defaults according to @var{spec}. You should not quote the symbol @var{face}. The argument @var{doc} specifies the face documentation. The keywords you @@ -1374,6 +1838,17 @@ What kinds of colors the frame supports---either @code{color}, @item background The kind of background---either @code{light} or @code{dark}. + +@item min-colors +An integer that represents the minimum number of colors the frame should +support, it is compared with the result of @code{display-color-cells}. + +@item supports +Whether or not the frame can display the face attributes given in +@var{value}@dots{} (@pxref{Face Attributes}). See the documentation +for the function @code{display-supports-face-attributes-p} for more +information on exactly how this testing is done. @xref{Display Face +Attribute Testing}. @end table If an element of @var{display} specifies more than one @var{value} for a @@ -1389,17 +1864,20 @@ frame must match one of the @var{value}s specified for it in @example @group -(defface region - `((((type tty) (class color)) - (:background "blue" :foreground "white")) + '((((class color) (min-colors 88) (background dark)) + :background "blue3") @end group + (((class color) (min-colors 88) (background light)) + :background "lightgoldenrod2") + (((class color) (min-colors 16) (background dark)) + :background "blue3") + (((class color) (min-colors 16) (background light)) + :background "lightgoldenrod2") + (((class color) (min-colors 8)) + :background "blue" :foreground "white") (((type tty) (class mono)) - (:inverse-video t)) - (((class color) (background dark)) - (:background "blue")) - (((class color) (background light)) - (:background "lightblue")) - (t (:background "gray"))) + :inverse-video t) + (t :background "gray")) @group "Basic face for highlighting the region." :group 'basic-faces) @@ -1428,7 +1906,7 @@ as if they had a light background. attributes}. This table lists all the face attributes, and what they mean. Note that in general, more than one face can be specified for a given piece of text; when that happens, the attributes of all the faces -are merged to specify how to display the text. @xref{Merging Faces}. +are merged to specify how to display the text. @xref{Displaying Faces}. In Emacs 21, any attribute in a face can have the value @code{unspecified}. This means the face doesn't specify that attribute. @@ -1454,13 +1932,13 @@ set width. This should be one of the symbols @code{ultra-condensed}, @code{extra-condensed}, @code{condensed}, @code{semi-condensed}, @code{normal}, @code{semi-expanded}, @code{expanded}, @code{extra-expanded}, or @code{ultra-expanded}. - + @item :height Either the font height, an integer in units of 1/10 point, a floating point number specifying the amount by which to scale the height of any underlying face, or a function, which is called with the old height (from the underlying face), and should return the new height. - + @item :weight Font weight---a symbol from this series (from most dense to most faint): @code{ultra-bold}, @code{extra-bold}, @code{bold}, @code{semi-bold}, @@ -1479,10 +1957,14 @@ On a text-only terminal, slanted text is displayed as half-bright, if the terminal supports the feature. @item :foreground -Foreground color, a string. - +Foreground color, a string. The value can be a system-defined color +name, or a hexadecimal color specification of the form +@samp{#@var{rr}@var{gg}@var{bb}}. (@samp{#000000} is black, +@samp{#ff0000} is red, @samp{#00ff00} is green, @samp{#0000ff} is +blue, and @samp{#ffffff} is white.) + @item :background -Background color, a string. +Background color, a string, like the foreground color. @item :inverse-video Whether or not characters should be displayed in inverse video. The @@ -1630,8 +2112,8 @@ Thus, @example (set-face-attribute 'foo nil - :width :extended - :weight :bold + :width 'extended + :weight 'bold :underline "red") @end example @@ -1641,7 +2123,7 @@ to the corresponding values. @end defun @tindex face-attribute -@defun face-attribute face attribute &optional frame +@defun face-attribute face attribute &optional frame inherit This returns the value of the @var{attribute} attribute of face @var{face} on @var{frame}. If @var{frame} is @code{nil}, that means the selected frame (@pxref{Input Focus}). @@ -1649,6 +2131,21 @@ that means the selected frame (@pxref{Input Focus}). If @var{frame} is @code{t}, the value is the default for @var{face} for new frames. +If @var{inherit} is @code{nil}, only attributes directly defined by +@var{face} are considered, so the return value may be +@code{unspecified}, or a relative value. If @var{inherit} is +non-@code{nil}, @var{face}'s definition of @var{attribute} is merged +with the faces specified by its @code{:inherit} attribute; however the +return value may still be @code{unspecified} or relative. If +@var{inherit} is a face or a list of faces, then the result is further +merged with that face (or faces), until it becomes specified and +absolute. + +To ensure that the return value is always specified and absolute, use +a value of @code{default} for @var{inherit}; this will resolve any +unspecified or relative values by merging with the @code{default} face +(which is always completely specified). + For example, @example @@ -1661,6 +2158,21 @@ For example, with older Emacs versions, you can use the following functions to set and examine the face attributes which existed in those versions. +@tindex face-attribute-relative-p +@defun face-attribute-relative-p attribute value +This function returns non-@code{nil} if @var{value}, when used as +the value of the face attribute @var{attribute}, is relative (that is, +if it modifies an underlying or inherited value of @var{attribute}). +@end defun + +@tindex merge-face-attribute +@defun merge-face-attribute attribute value1 value2 +If @var{value1} is a relative value for the face attribute +@var{attribute}, returns it merged with the underlying value +@var{value2}; otherwise, if @var{value1} is an absolute value for the +face attribute @var{attribute}, returns @var{value1} unchanged. +@end defun + @defun set-face-foreground face color &optional frame @defunx set-face-background face color &optional frame These functions set the foreground (or background, respectively) color @@ -1725,15 +2237,30 @@ specify @var{frame}, they refer to the default data for new frames. They return the symbol @code{unspecified} if the face doesn't define any value for that attribute. -@defun face-foreground face &optional frame +@defun face-foreground face &optional frame inherit @defunx face-background face &optional frame These functions return the foreground color (or background color, respectively) of face @var{face}, as a string. + +If @var{inherit} is @code{nil}, only a color directly defined by the face is +returned. If @var{inherit} is non-@code{nil}, any faces specified by its +@code{:inherit} attribute are considered as well, and if @var{inherit} +is a face or a list of faces, then they are also considered, until a +specified color is found. To ensure that the return value is always +specified, use a value of @code{default} for @var{inherit}. @end defun -@defun face-stipple face &optional frame +@defun face-stipple face &optional frame inherit This function returns the name of the background stipple pattern of face @var{face}, or @code{nil} if it doesn't have one. + +If @var{inherit} is @code{nil}, only a stipple directly defined by the +face is returned. If @var{inherit} is non-@code{nil}, any faces +specified by its @code{:inherit} attribute are considered as well, and +if @var{inherit} is a face or a list of faces, then they are also +considered, until a specified stipple is found. To ensure that the +return value is always specified, use a value of @code{default} for +@var{inherit}. @end defun @defun face-font face &optional frame @@ -1758,8 +2285,8 @@ This function returns the @code{:underline} attribute of face @var{face}. This function returns the @code{:inverse-video} attribute of face @var{face}. @end defun -@node Merging Faces -@subsection Merging Faces for Display +@node Displaying Faces +@subsection Displaying Faces Here are the ways to specify which faces to use for display of text: @@ -1790,7 +2317,7 @@ With a region that is active. In Transient Mark mode, the region is highlighted with the face @code{region} (@pxref{Standard Faces}). @item -With special glyphs. Each glyph can specify a particular face +With special glyphs. Each glyph can specify a particular face number. @xref{Glyphs}. @end itemize @@ -1819,28 +2346,6 @@ face attributes, as determined by face merging, specify most of the font choice, but not all. Part of the choice depends on what character it is. - For multibyte characters, typically each font covers only one -character set. So each character set (@pxref{Character Sets}) specifies -a registry and encoding to use, with the character set's -@code{x-charset-registry} property. Its value is a string containing -the registry and the encoding, with a dash between them: - -@example -(plist-get (charset-plist 'latin-iso8859-1) - 'x-charset-registry) - @result{} "ISO8859-1" -@end example - - Unibyte text does not have character sets, so displaying a unibyte -character takes the registry and encoding from the variable -@code{face-default-registry}. - -@defvar face-default-registry -This variable specifies which registry and encoding to use in choosing -fonts for unibyte characters. The value is initialized at Emacs startup -time from the font the user specified for Emacs. -@end defvar - If the face specifies a fontset name, that fontset determines a pattern for fonts of the given charset. If the face specifies a font family, a font pattern is constructed. @@ -1943,6 +2448,21 @@ If @var{unload-p} is non-@code{nil}, that means to unload all unused fonts as well. @end defun +@defvar face-font-rescale-alist +This variable specifies scaling for certain faces. Its value should +be a list of elements of the form + +@example +(@var{fontname-regexp} . @var{scale-factor}) +@end example + +If @var{fontname-regexp} matches the font name that is about to be +used, this says to choose a larger similar font according to the +factor @var{scale-factor}. You would use this feature to normalize +the font size if certain fonts are bigger or smaller than their +nominal heights and widths would suggest. +@end defvar + @node Face Functions @subsection Functions for Working with Faces @@ -1988,10 +2508,8 @@ same attributes for display. @end defun @defun face-differs-from-default-p face &optional frame -This returns @code{t} if the face @var{face} displays differently from -the default face. A face is considered to be ``the same'' as the -default face if each attribute is either the same as that of the default -face, or unspecified (meaning to inherit from the default). +This returns non-@code{nil} if the face @var{face} displays +differently from the default face. @end defun @node Auto Faces @@ -2078,9 +2596,10 @@ The first five elements correspond to face attributes; if you specify these attributes for a face, it will use this font. The last three elements give additional information about the font. -@var{fixed-p} is non-nil if the font is fixed-pitch. @var{full} is the -full name of the font, and @var{registry-and-encoding} is a string -giving the registry and encoding of the font. +@var{fixed-p} is non-@code{nil} if the font is fixed-pitch. +@var{full} is the full name of the font, and +@var{registry-and-encoding} is a string giving the registry and +encoding of the font. The result list is sorted according to the current face font sort order. @end defun @@ -2162,7 +2681,7 @@ times in the specification string. For the remaining character sets, those that you don't specify explicitly, Emacs chooses a font based on @var{fontpattern}: it replaces @samp{fontset-@var{alias}} with a value that names one character set. -For the @sc{ascii} character set, @samp{fontset-@var{alias}} is replaced +For the @acronym{ASCII} character set, @samp{fontset-@var{alias}} is replaced with @samp{ISO8859-1}. In addition, when several consecutive fields are wildcards, Emacs @@ -2178,7 +2697,7 @@ better to use the smaller font in its own size, which Emacs does. @end example @noindent -the font specification for @sc{ascii} characters would be this: +the font specification for @acronym{ASCII} characters would be this: @example -*-fixed-medium-r-normal-*-24-*-ISO8859-1 @@ -2207,6 +2726,303 @@ Then, the font specifications for all but Chinese GB2312 characters have Chinese GB2312 characters has a wild card @samp{*} in the @var{family} field. +@defun set-fontset-font name character fontname &optional frame +This function modifies the existing fontset @var{name} to +use the font name @var{fontname} for the character @var{character}. + +If @var{name} is @code{nil}, this function modifies the default +fontset, whose short name is @samp{fontset-default}. + +@var{character} may be a cons; @code{(@var{from} . @var{to})}, where +@var{from} and @var{to} are non-generic characters. In that case, use +@var{fontname} for all characters in the range @var{from} and @var{to} +(inclusive). + +@var{character} may be a charset. In that case, use +@var{fontname} for all character in the charsets. + +@var{fontname} may be a cons; @code{(@var{family} . @var{registry})}, +where @var{family} is a family name of a font (possibly including a +foundry name at the head), @var{registry} is a registry name of a font +(possibly including an encoding name at the tail). + +For instance, this changes the default fontset to use a font of which +registry name is @samp{JISX0208.1983} for all characters belonging to +the charset @code{japanese-jisx0208}. + +@example +(set-fontset-font nil 'japanese-jisx0208 '(nil . "JISX0208.1983")) +@end example + +@end defun + +@defun char-displayable-p char +This function returns @code{t} if Emacs ought to be able to display +@var{char}. More precisely, if the selected frame's fontset has a +font to display the character set that @var{char} belongs to. + +Fontsets can specify a font on a per-character basis; when the fontset +does that, this function's value may not be accurate. +@end defun + +@node Fringes +@section Fringes +@cindex Fringes + + The @dfn{fringes} of a window are thin vertical strips down the +sides that are used for displaying bitmaps that indicate truncation, +continuation, horizontal scrolling, and the overlay arrow. The +fringes normally appear between the display margins and the window +text, but you can put them outside the display margins for a specific +buffer by setting @code{fringes-outside-margins} buffer-locally to a +non-@code{nil} value. + +@defvar fringes-outside-margins +If the value is non-@code{nil}, the frames appear outside +the display margins. +@end defvar + +@defvar left-fringe-width +This variable, if non-@code{nil}, specifies the width of the left +fringe in pixels. +@end defvar + +@defvar right-fringe-width +This variable, if non-@code{nil}, specifies the width of the right +fringe in pixels. +@end defvar + + The values of these variables take effect when you display the +buffer in a window. If you change them while the buffer is visible, +you can call @code{set-window-buffer} to display it once again in the +same window, to make the changes take effect. + +@defun set-window-fringes window left &optional right outside-margins +This function sets the fringe widths of window @var{window}. +If @var{window} is @code{nil}, the selected window is used. + +The argument @var{left} specifies the width in pixels of the left +fringe, and likewise @var{right} for the right fringe. A value of +@code{nil} for either one stands for the default width. If +@var{outside-margins} is non-@code{nil}, that specifies that fringes +should appear outside of the display margins. +@end defun + +@defun window-fringes &optional window +This function returns information about the fringes of a window +@var{window}. If @var{window} is omitted or @code{nil}, the selected +window is used. The value has the form @code{(@var{left-width} +@var{right-width} @var{frames-outside-margins})}. +@end defun + +@defvar overflow-newline-into-fringe +If this is non-@code{nil}, lines exactly as wide as the window (not +counting the final newline character) are not continued. Instead, +when point is at the end of the line, the cursor appears in the right +fringe. +@end defvar + +@node Fringe Bitmaps +@section Fringe Bitmaps +@cindex fringe bitmaps +@cindex bitmaps, fringe + + The @dfn{fringe bitmaps} are tiny icons Emacs displays in the window +fringe (on a graphic display) to indicate truncated or continued +lines, buffer boundaries, overlay arrow, etc. The fringe bitmaps are +shared by all frames and windows. You can redefine the built-in +fringe bitmaps, and you can define new fringe bitmaps. + + The way to display a bitmap in the left or right fringes for a given +line in a window is by specifying the @code{display} property for one +of the characters that appears in it. Use a display specification of +the form @code{(left-fringe @var{bitmap} [@var{face}])} or +@code{(right-fringe @var{bitmap} [@var{face}])} (@pxref{Display +Property}). Here, @var{bitmap} is a symbol identifying the bitmap +you want, and @var{face} (which is optional) is the name of the face +whose colors should be used for displaying the bitmap. + + These are the symbols identify the standard fringe bitmaps. +Evaluate @code{(require 'fringe)} to define them. Fringe bitmap +symbols have their own name space. + +@table @asis +@item Truncation and continuation line bitmaps: +@code{left-truncation}, @code{right-truncation}, +@code{continued-line}, @code{continuation-line}. + +@item Buffer indication bitmaps: +@code{up-arrow}, @code{down-arrow}, +@code{top-left-angle}, @code{top-right-angle}, +@code{bottom-left-angle}, @code{bottom-right-angle}, +@code{left-bracket}, @code{right-bracket}. + +@item Empty line indication bitmap: +@code{empty-line}. + +@item Overlay arrow bitmap: +@code{overlay-arrow}. + +@item Bitmaps for displaying the cursor in right fringe: +@code{filled-box-cursor}, @code{hollow-box-cursor}, @code{hollow-square}, +@code{bar-cursor}, @code{hbar-cursor}. +@end table + +@defun fringe-bitmaps-at-pos &optional pos window +This function returns the fringe bitmaps of the display line +containing position @var{pos} in window @var{window}. The return +value has the form @code{(@var{left} @var{right} @var{ov})}, where @var{left} +is the symbol for the fringe bitmap in the left fringe (or @code{nil} +if no bitmap), @var{right} is similar for the right fringe, and @var{ov} +is non-@code{nil} if there is an overlay arrow in the left fringe. + +The value is @code{nil} if @var{pos} is not visible in @var{window}. +If @var{window} is @code{nil}, that stands for the selected window. +If @var{pos} is @code{nil}, that stands for the value of point in +@var{window}. +@end defun + +@node Customizing Bitmaps +@section Customizing Fringe Bitmaps + +@defun define-fringe-bitmap bitmap bits &optional height width align +This function defines the symbol @var{bitmap} as a new fringe bitmap, +or replaces an existing bitmap with that name. + +The argument @var{bits} specifies the image to use. It should be +either a string or a vector of integers, where each element (an +integer) corresponds to one row of the bitmap. Each bit of an integer +corresponds to one pixel of the bitmap, where the low bit corresponds +to the rightmost pixel of the bitmap. + +The height is normally the length of @var{bits}. However, you +can specify a different height with non-@code{nil} @var{height}. The width +is normally 8, but you can specify a different width with non-@code{nil} +@var{width}. The width must be an integer between 1 and 16. + +The argument @var{align} specifies the positioning of the bitmap +relative to the range of rows where it is used; the default is to +center the bitmap. The allowed values are @code{top}, @code{center}, +or @code{bottom}. + +The @var{align} argument may also be a list @code{(@var{align} +@var{periodic})} where @var{align} is interpreted as described above. +If @var{periodic} is non-@code{nil}, it specifies that the rows in +@code{bits} should be repeated enough times to reach the specified +height. + +The return value on success is an integer identifying the new bitmap. +You should save that integer in a variable so it can be used to select +this bitmap. + +This function signals an error if there are no more free bitmap slots. +@end defun + +@defun destroy-fringe-bitmap bitmap +This function destroy the fringe bitmap identified by @var{bitmap}. +If @var{bitmap} identifies a standard fringe bitmap, it actually +restores the standard definition of that bitmap, instead of +eliminating it entirely. +@end defun + +@defun set-fringe-bitmap-face bitmap &optional face +This sets the face for the fringe bitmap @var{bitmap} to @var{face}. +If @var{face} is @code{nil}, it selects the @code{fringe} face. The +bitmap's face controls the color to draw it in. + +The face you use here should be derived from @code{fringe}, and should +specify only the foreground color. +@end defun + +@node Scroll Bars +@section Scroll Bars + +Normally the frame parameter @code{vertical-scroll-bars} controls +whether the windows in the frame have vertical scroll bars. A +non-@code{nil} parameter value means they do. The frame parameter +@code{scroll-bar-width} specifies how wide they are (@code{nil} +meaning the default). @xref{Window Frame Parameters}. + +@vindex vertical-scroll-bar + You can enable or disable scroll bars for a particular buffer, +by setting the variable @code{vertical-scroll-bar}. This variable +automatically becomes buffer-local when set. The possible values are +@code{left}, @code{right}, @code{t}, which means to use the +frame's default, and @code{nil} for no scroll bar. + + You can also control this for individual windows. Call the function +@code{set-window-scroll-bars} to specify what to do for a specific window: + +@defun set-window-scroll-bars window width &optional vertical-type horizontal-type +This function sets the width and type of scroll bars for window +@var{window}. + +@var{width} specifies the scroll bar width in pixels (@code{nil} means +use the width specified for the frame). @var{vertical-type} specifies +whether to have a vertical scroll bar and, if so, where. The possible +values are @code{left}, @code{right} and @code{nil}, just like the +values of the @code{vertical-scroll-bars} frame parameter. + +The argument @var{horizontal-type} is meant to specify whether and +where to have horizontal scroll bars, but since they are not +implemented, it has no effect. If @var{window} is @code{nil}, the +selected window is used. +@end defun + +@defun window-scroll-bars &optional window +Report the width and type of scroll bars specified for @var{window}. +If @var{window} is omitted or @code{nil}, the selected window is used. +The value is a list of the form @code{(@var{width} +@var{cols} @var{vertical-type} @var{horizontal-type})}. The value +@var{width} is the value that was specified for the width (which may +be @code{nil}); @var{cols} is the number of columns that the scroll +bar actually occupies. + +@var{horizontal-type} is not actually meaningful. +@end defun + +If you don't specify these values for a window with +@code{set-window-scroll-bars}, the buffer-local variables +@code{scroll-bar-mode} and @code{scroll-bar-width} in the buffer being +displayed control the window's vertical scroll bars. The function +@code{set-window-buffer} examines these variables. If you change them +in a buffer that is already visible in a window, you can make the +window take note of the new values by calling @code{set-window-buffer} +specifying the same buffer that is already displayed. + +@defvar scroll-bar-mode +This variable, always local in all buffers, controls whether and where +to put scroll bars in windows displaying the buffer. The possible values +are @code{nil} for no scroll bar, @code{left} to put a scroll bar on +the left, and @code{right} to put a scroll bar on the right. +@end defvar + +@defvar scroll-bar-width +This variable, always local in all buffers, specifies the width of the +buffer's scroll bars, measured in pixels. A value of @code{nil} means +to use the value specified by the frame. +@end defvar + +@node Pointer Shape +@section Pointer Shape + + Normally, the mouse pointer has the @code{text} shape over text and +the @code{arrow} shape over window areas which do not correspond to +any buffer text. You can specify the mouse pointer shape over text or +images via the @code{pointer} text property, and for images with the +@code{:pointer} and @code{:map} image properties. + + The available pointer shapes are: @code{text} (or @code{nil}), +@code{arrow}, @code{hand}, @code{vdrag}, @code{hdrag}, +@code{modeline}, and @code{hourglass}. + +@defvar void-text-area-pointer +@tindex void-text-area-pointer +This variable specifies the mouse pointer shape in void text areas, +i.e. the areas after the end of a line or below the last line in the +buffer. The default is to use the @code{arrow} (non-text) pointer. +@end defvar + @node Display Property @section The @code{display} Property @cindex display specification @@ -2221,12 +3037,13 @@ this section describes several kinds of display specifications and what they mean. @menu -* Specified Space:: Displaying one space with a specified width. -* Other Display Specs:: Displaying an image; magnifying text; moving it - up or down on the page; adjusting the width +* Specified Space:: Displaying one space with a specified width. +* Pixel Specification:: Specifying space width or height in pixels. +* Other Display Specs:: Displaying an image; magnifying text; moving it + up or down on the page; adjusting the width of spaces within text. * Display Margins:: Displaying text or images to the side of the main text. -* Conditional Display:: Making any of the above features conditional +* Conditional Display:: Making any of the above features conditional depending on some Lisp expression. @end menu @@ -2242,13 +3059,14 @@ specification of the form @code{(space . @var{props})}, where values). You can put this property on one or more consecutive characters; a space of the specified height and width is displayed in place of @emph{all} of those characters. These are the properties you -can use to specify the weight of the space: +can use in @var{props} to specify the weight of the space: @table @code @item :width @var{width} -Specifies that the space width should be @var{width} times the normal -character width. @var{width} can be an integer or floating point -number. +If @var{width} is an integer or floating point number, it specifies +that the space width should be @var{width} times the normal character +width. @var{width} can also be a @dfn{pixel width} specification +(@pxref{Pixel Specification}). @item :relative-width @var{factor} Specifies that the width of the stretch should be computed from the @@ -2257,42 +3075,131 @@ same @code{display} property. The space width is the width of that character, multiplied by @var{factor}. @item :align-to @var{hpos} -Specifies that the space should be wide enough to reach @var{hpos}. The -value @var{hpos} is measured in units of the normal character width. It -may be an interer or a floating point number. +Specifies that the space should be wide enough to reach @var{hpos}. +If @var{hpos} is a number, it is measured in units of the normal +character width. @var{hpos} can also be a @dfn{pixel width} +specification (@pxref{Pixel Specification}). @end table - Exactly one of the above properties should be used. You can also -specify the height of the space, with other properties: + You should use one and only one of the above properties. You can +also specify the height of the space, with these properties: @table @code @item :height @var{height} -Specifies the height of the space, as @var{height}, -measured in terms of the normal line height. +Specifies the height of the space. +If @var{height} is an integer or floating point number, it specifies +that the space height should be @var{height} times the normal character +height. The @var{height} may also be a @dfn{pixel height} specification +(@pxref{Pixel Specification}). @item :relative-height @var{factor} Specifies the height of the space, multiplying the ordinary height of the text having this display specification by @var{factor}. @item :ascent @var{ascent} -Specifies that @var{ascent} percent of the height of the space should be -considered as the ascent of the space---that is, the part above the -baseline. The value of @var{ascent} must be a non-negative number no -greater than 100. +If the value of @var{ascent} is a non-negative number no greater than +100, it specifies that @var{ascent} percent of the height of the space +should be considered as the ascent of the space---that is, the part +above the baseline. The ascent may also be specified in pixel units +with a @dfn{pixel ascent} specification (@pxref{Pixel Specification}). + @end table - You should not use both @code{:height} and @code{:relative-height} -together. + Don't use both @code{:height} and @code{:relative-height} together. + + The @code{:height} and @code{:align-to} properties are supported on +non-graphic terminals, but the other space properties in this section +are not. + +@node Pixel Specification +@subsection Pixel Specification for Spaces +@cindex spaces, pixel specification + + The value of the @code{:width}, @code{:align-to}, @code{:height}, +and @code{:ascent} properties can be a special kind of expression that +is evaluated during redisplay. The result of the evaluation is used +as an absolute number of pixels. + + The following expressions are supported: + +@example +@group + @var{expr} ::= @var{num} | (@var{num}) | @var{unit} | @var{elem} | @var{pos} | @var{image} | @var{form} + @var{num} ::= @var{integer} | @var{float} | @var{symbol} + @var{unit} ::= in | mm | cm | width | height + @var{elem} ::= left-fringe | right-fringe | left-margin | right-margin + | scroll-bar | text + @var{pos} ::= left | center | right + @var{form} ::= (@var{num} . @var{expr}) | (@var{op} @var{expr} ...) + @var{op} ::= + | - +@end group +@end example + + The form @var{num} specifies a fraction of the default frame font +height or width. The form @code{(@var{num})} specifies an absolute +number of pixels. If @var{num} is a symbol, @var{symbol}, its +buffer-local variable binding is used. + + The @code{in}, @code{mm}, and @code{cm} units specify the number of +pixels per inch, millimeter, and centimeter, respectively. The +@code{width} and @code{height} units correspond to the default width +and height of the current face. An image specification @code{image} +corresponds to the width or height of the image. + + The @code{left-fringe}, @code{right-fringe}, @code{left-margin}, +@code{right-margin}, @code{scroll-bar}, and @code{text} elements +specify to the width of the corresponding area of the window. + + The @code{left}, @code{center}, and @code{right} positions can be +used with @code{:align-to} to specify a position relative to the left +edge, center, or right edge of the text area. + + Any of the above window elements (except @code{text}) can also be +used with @code{:align-to} to specify that the position is relative to +the left edge of the given area. Once the base offset for a relative +position has been set (by the first occurrence of one of these +symbols), further occurrences of these symbols are interpreted as the +width of the specified area. For example, to align to the center of +the left-margin, use + +@example +:align-to (+ left-margin (0.5 . left-margin)) +@end example + + If no specific base offset is set for alignment, it is always relative +to the left edge of the text area. For example, @samp{:align-to 0} in a +header-line aligns with the first text column in the text area. + + A value of the form @code{(@var{num} . @var{expr})} stands +multiplying the values of @var{num} and @var{expr}. For example, +@code{(2 . in)} specifies a width of 2 inches, while @code{(0.5 . +@var{image})} specifies half the width (or height) of the specified image. + + The form @code{(+ @var{expr} ...)} adds up the value of the +expressions. The form @code{(- @var{expr} ...)} negates or subtracts +the value of the expressions. @node Other Display Specs @subsection Other Display Specifications + Here are the other sorts of display specifications that you can use +in the @code{display} text property. + @table @code @item (image . @var{image-props}) This is in fact an image descriptor (@pxref{Images}). When used as a display specification, it means to display the image instead of the text that has the display specification. +@item (slice @var{x} @var{y} @var{width} @var{height}) +This specification together with @code{image} specifies a @dfn{slice} +(a partial area) of the image to display. The elements @var{y} and +@var{x} specify the top left corner of the slice, within the image; +@var{width} and @var{height} specify the width and height of the +slice. Integer values are numbers of pixels. A floating point number +in the range 0.0--1.0 stands for that fraction of the width or height +of the entire image. + @item ((margin nil) @var{string}) @itemx @var{string} A display specification of this form means to display @var{string} @@ -2300,9 +3207,8 @@ instead of the text that has the display specification, at the same position as that text. This is a special case of marginal display (@pxref{Display Margins}). -Recursive display specifications are not supported, i.e.@: string -display specifications that have a display specification property -themselves. +Recursive display specifications are not supported---string display +specifications must not have @code{display} properties themselves. @item (space-width @var{factor}) This display specification affects all the space characters within the @@ -2405,7 +3311,7 @@ Thus, you can make changes take effect by calling @defun set-window-margins window left &optional right @tindex set-window-margins This function specifies the margin widths for window @var{window}. -The argument @var{left} controls the left margin and +The argument @var{left} controls the left margin and @var{right} controls the right margin (default @code{0}). @end defun @@ -2441,8 +3347,13 @@ property of text that is displayed (@pxref{Display Property}). Like the @code{display} property, this feature is available starting in Emacs 21. Emacs can display a number of different image formats; some of them -are supported only if particular support libraries are installed on your -machine. The supported image formats include XBM, XPM (needing the +are supported only if particular support libraries are installed on +your machine. In some environments, Emacs allows loading image +libraries on demand; if so, the variable @code{image-library-alist} +can be used to modify the set of known names for these dynamic +libraries (though it is not possible to add new image formats). + + The supported image formats include XBM, XPM (needing the libraries @code{libXpm} version 3.4k and @code{libz}), GIF (needing @code{libungif} 4.1.0), Postscript, PBM, JPEG (needing the @code{libjpeg} library version v6a), TIFF (needing @code{libtiff} v3.4), @@ -2454,9 +3365,46 @@ type symbols are @code{xbm}, @code{xpm}, @code{gif}, @code{postscript}, @defvar image-types This variable contains a list of those image type symbols that are -supported in the current configuration. +potentially supported in the current configuration. +@emph{Potentially} here means that Emacs knows about the image types, +not necessarily that they can be loaded (they could depend on +unavailable dynamic libraries, for example). + +To know which image types are really available, use +@code{image-type-available-p}. +@end defvar + +@defvar image-library-alist +This in an alist of image types vs external libraries needed to +display them. + +Each element is a list @code{(@var{image-type} @var{library}...)}, +where the car is a supported image format from @code{image-types}, and +the rest are strings giving alternate filenames for the corresponding +external libraries to load. + +Emacs tries to load the libraries in the order they appear on the +list; if none is loaded, the running session of Emacs won't support +the image type. @code{pbm} and @code{xbm} don't need to be listed; +they're always supported. + +This variable is ignored if the image libraries are statically linked +into Emacs. @end defvar +@defun image-type-available-p type +@findex image-type-available-p + +This function returns non-@code{nil} if image type @var{type} is +available, i.e., if images of this type can be loaded and displayed in +Emacs. @var{type} should be one of the types contained in +@code{image-types}. + +For image types whose support libraries are statically linked, this +function always returns @code{t}; for other image types, it returns +@code{t} if the dynamic library could be loaded, @code{nil} otherwise. +@end defun + @menu * Image Descriptors:: How to specify an image for use in @code{:display}. * XBM Images:: Special features for XBM format. @@ -2508,7 +3456,7 @@ image properties along with @code{:data}. @item :margin @var{margin} The @code{:margin} property specifies how many pixels to add as an -extra margin around the image. The value, @var{margin}, must be a a +extra margin around the image. The value, @var{margin}, must be a non-negative number, or a pair @code{(@var{x} . @var{y})} of such numbers. If it is a pair, @var{x} specifies how many pixels to add horizontally, and @var{y} specifies how many pixels to add vertically. @@ -2625,9 +3573,46 @@ color from the corners is the background color of the image. Otherwise, @var{bg} must be a list @code{(@var{red} @var{green} @var{blue})} specifying the color to assume for the background of the image. -If @var{mask} is nil, remove a mask from the image, if it has one. Images -in some formats include a mask which can be removed by specifying -@code{:mask nil}. +If @var{mask} is @code{nil}, remove a mask from the image, if it has +one. Images in some formats include a mask which can be removed by +specifying @code{:mask nil}. + +@item :pointer @var{shape} +This specifies the pointer shape when the mouse pointer is over this +image. @xref{Pointer Shape}, for available pointer shapes. + +@item :map @var{map} +This associates an image map of @dfn{hot spots} with this image. + +An image map is an alist where each element has the format +@code{(@var{area} @var{id} @var{plist})}. An @var{area} is specified +as either a rectangle, a circle, or a polygon. + +A rectangle is a cons +@code{(rect . ((@var{x0} . @var{y0}) . (@var{x1} . @var{y1})))} +which specifies the pixel coordinates of the upper left and bottom right +corners of the rectangle area. + +A circle is a cons +@code{(circle . ((@var{x0} . @var{y0}) . @var{r}))} +which specifies the center and the radius of the circle; @var{r} may +be a float or integer. + +A polygon is a cons +@code{(poly . [@var{x0} @var{y0} @var{x1} @var{y1} ...])} +where each pair in the vector describes one corner in the polygon. + +When the mouse pointer is above a hot-spot area of an image, the +@var{plist} of that hot-spot is consulted; if it contains a @code{help-echo} +property it defines a tool-tip for the hot-spot, and if it contains +a @code{pointer} property, it defines the shape of the mouse cursor when +it is over the hot-spot. +@xref{Pointer Shape}, for available pointer shapes. + +When you click the mouse when the mouse pointer is over a hot-spot, an +event is composed by combining the @var{id} of the hot-spot with the +mouse event; for instance, @code{[area4 mouse-1]} if the hot-spot's +@var{id} is @code{area4}. @end table @defun image-mask-p spec &optional frame @@ -2720,7 +3705,7 @@ specifies the actual color to use for displaying that name. For GIF images, specify image type @code{gif}. Because of the patents in the US covering the LZW algorithm, the continued use of GIF format is a problem for the whole Internet; to end this problem, it is a good idea -for everyone, even outside the US, to stop using GIFS right away +for everyone, even outside the US, to stop using GIFs right away (@uref{http://www.burnallgifs.org/}). But if you still want to use them, Emacs can display them. @@ -2728,8 +3713,8 @@ them, Emacs can display them. @item :index @var{index} You can use @code{:index} to specify one image from a GIF file that contains more than one image. This property specifies use of image -number @var{index} from the file. An error is signaled if the GIF file -doesn't contain an image with index @var{index}. +number @var{index} from the file. If the GIF file doesn't contain an +image with index @var{index}, the image displays as a hollow box. @end table @ignore @@ -2819,10 +3804,12 @@ background color. The functions @code{create-image}, @code{defimage} and @code{find-image} provide convenient ways to create image descriptors. -@defun create-image file &optional type &rest props +@defun create-image file-or-data &optional type data-p &rest props @tindex create-image This function creates and returns an image descriptor which uses the -data in @var{file}. +data in @var{file-or-data}. @var{file-or-data} can be a file name or +a string containing the image data; @var{data-p} should be @code{nil} +for the former case, non-@code{nil} for the latter case. The optional argument @var{type} is a symbol specifying the image type. If @var{type} is omitted or @code{nil}, @code{create-image} tries to @@ -2833,7 +3820,7 @@ The remaining arguments, @var{props}, specify additional image properties---for example, @example -(create-image "foo.xpm" 'xpm :heuristic-mask t) +(create-image "foo.xpm" 'xpm nil :heuristic-mask t) @end example The function returns @code{nil} if images of this type are not @@ -2856,8 +3843,8 @@ example: @example (defimage test-image - '((:type xpm :file "~/test1.xpm") - (:type xbm :file "~/test1.xbm"))) + ((:type xpm :file "~/test1.xpm") + (:type xbm :file "~/test1.xbm"))) @end example @code{defimage} tests each argument, one by one, to see if it is @@ -2895,7 +3882,7 @@ The image is looked for first on @code{load-path} and then in property yourself, but it is easier to use the functions in this section. -@defun insert-image image &optional string area +@defun insert-image image &optional string area slice This function inserts @var{image} in the current buffer at point. The value @var{image} should be an image descriptor; it could be a value returned by @code{create-image}, or the value of a symbol defined with @@ -2908,11 +3895,26 @@ If it is @code{left-margin}, the image appears in the left margin; @code{nil} or omitted, the image is displayed at point within the buffer's text. +The argument @var{slice} specifies a slice of the image to insert. If +@var{slice} is @code{nil} or omitted the whole image is inserted. +Otherwise, @var{slice} is a list @code{(@var{x} @var{y} @var{width} +@var{height})} which specifies the @var{x} and @var{y} positions and +@var{width} and @var{height} of the image area to insert. Integer +values are in units of pixels. A floating point number in the range +0.0--1.0 stands for that fraction of the width or height of the entire +image. + Internally, this function inserts @var{string} in the buffer, and gives it a @code{display} property which specifies @var{image}. @xref{Display Property}. @end defun +@defun insert-sliced-image image &optional string area rows cols +This function inserts @var{image} in the current buffer at point, like +@code{insert-image}, but splits the image into @var{rows}x@var{cols} +equally sized slices. +@end defun + @defun put-image image pos &optional string area This function puts image @var{image} in front of @var{pos} in the current buffer. The argument @var{pos} should be an integer or a @@ -2948,10 +3950,10 @@ This removes only images that were put into @var{buffer} the way @tindex image-size This function returns the size of an image as a pair @w{@code{(@var{width} . @var{height})}}. @var{spec} is an image -specification. @var{pixels} non-nil means return sizes measured in -pixels, otherwise return sizes measured in canonical character units -(fractions of the width/height of the frame's default font). -@var{frame} is the frame on which the image will be displayed. +specification. @var{pixels} non-@code{nil} means return sizes +measured in pixels, otherwise return sizes measured in canonical +character units (fractions of the width/height of the frame's default +font). @var{frame} is the frame on which the image will be displayed. @var{frame} null or omitted means use the selected frame (@pxref{Input Focus}). @end defun @@ -2985,6 +3987,357 @@ only the cache for that frame is cleared. Otherwise all frames' caches are cleared. @end defun +@node Buttons +@section Buttons +@cindex buttons +@cindex buttons in buffers +@cindex clickable buttons in buffers + + The @emph{button} package defines functions for inserting and +manipulating clickable (with the mouse, or via keyboard commands) +buttons in Emacs buffers, such as might be used for help hyper-links, +etc. Emacs uses buttons for the hyper-links in help text and the like. + +A button is essentially a set of properties attached (via text +properties or overlays) to a region of text in an Emacs buffer, which +are called its button properties. @xref{Button Properties}. + +One of the these properties (@code{action}) is a function, which will +be called when the user invokes it using the keyboard or the mouse. +The invoked function may then examine the button and use its other +properties as desired. + +In some ways the Emacs button package duplicates functionality offered +by the widget package (@pxref{Top, , Introduction, widget, The Emacs +Widget Library}), but the button package has the advantage that it is +much faster, much smaller, and much simpler to use (for elisp +programmers---for users, the result is about the same). The extra +speed and space savings are useful mainly if you need to create many +buttons in a buffer (for instance an @code{*Apropos*} buffer uses +buttons to make entries clickable, and may contain many thousands of +entries). + +@menu +* Button Properties:: Button properties with special meanings. +* Button Types:: Defining common properties for classes of buttons. +* Making Buttons:: Adding buttons to Emacs buffers. +* Manipulating Buttons:: Getting and setting properties of buttons. +* Button Buffer Commands:: Buffer-wide commands and bindings for buttons. +* Manipulating Button Types:: +@end menu + +@node Button Properties +@subsection Button Properties +@cindex button properties + + Buttons have an associated list of properties defining their +appearance and behavior, and other arbitrary properties may be used +for application specific purposes. + +Some properties that have special meaning to the button package +include: + +@table @code + +@item action +@kindex action @r{(button property)} +The function to call when the user invokes the button, which is passed +the single argument @var{button}. By default this is @code{ignore}, +which does nothing. + +@item mouse-action +@kindex mouse-action @r{(button property)} +This is similar to @code{action}, and when present, will be used +instead of @code{action} for button invocations resulting from +mouse-clicks (instead of the user hitting @key{RET}). If not +present, mouse-clicks use @code{action} instead. + +@item face +@kindex face @r{(button property)} +This is an Emacs face controlling how buttons of this type are +displayed; by default this is the @code{button} face. + +@item mouse-face +@kindex mouse-face @r{(button property)} +This is an additional face which controls appearance during +mouse-overs (merged with the usual button face); by default this is +the usual Emacs @code{highlight} face. + +@item keymap +@kindex keymap @r{(button property)} +The button's keymap, defining bindings active within the button +region. By default this is the usual button region keymap, stored +in the variable @code{button-map}, which defines @key{RET} and +@key{mouse-2} to invoke the button. + +@item type +@kindex type @r{(button property)} +The button-type of the button. When creating a button, this is +usually specified using the @code{:type} keyword argument. +@xref{Button Types}. + +@item help-echo +@kindex help-index @r{(button property)} +A string displayed by the Emacs tool-tip help system; by default, +@code{"mouse-2, RET: Push this button"}. + +@item follow-link +@kindex follow-link @r{(button property)} +The follow-link property, defining how a @key{Mouse-1} click behaves +on this button, @xref{Links and Mouse-1}. + +@item button +@kindex button @r{(button property)} +All buttons have a non-@code{nil} @code{button} property, which may be useful +in finding regions of text that comprise buttons (which is what the +standard button functions do). +@end table + +There are other properties defined for the regions of text in a +button, but these are not generally interesting for typical uses. + +@node Button Types +@subsection Button Types +@cindex button types + + Every button has a button @emph{type}, which defines default values +for the button's properties. Button types are arranged in a +hierarchy, with specialized types inheriting from more general types, +so that it's easy to define special-purpose types of buttons for +specific tasks. + +@defun define-button-type name &rest properties +@tindex define-button-type +Define a `button type' called @var{name}. The remaining arguments +form a sequence of @var{property value} pairs, specifying default +property values for buttons with this type (a button's type may be set +by giving it a @code{type} property when creating the button, using +the @code{:type} keyword argument). + +In addition, the keyword argument @code{:supertype} may be used to +specify a button-type from which @var{name} inherits its default +property values. Note that this inheritance happens only when +@var{name} is defined; subsequent changes to a supertype are not +reflected in its subtypes. +@end defun + +Using @code{define-button-type} to define default properties for +buttons is not necessary---buttons without any specified type use the +built-in button-type @code{button}---but it is is encouraged, since +doing so usually makes the resulting code clearer and more efficient. + +@node Making Buttons +@subsection Making Buttons +@cindex making buttons + + Buttons are associated with a region of text, using an overlay or +text-properties to hold button-specific information, all of which are +initialized from the button's type (which defaults to the built-in +button type @code{button}). Like all Emacs text, the appearance of +the button is governed by the @code{face} property; by default (via +the @code{face} property inherited from the @code{button} button-type) +this is a simple underline, like a typical web-page link. + +For convenience, there are two sorts of button-creation functions, +those that add button properties to an existing region of a buffer, +called @code{make-...button}, and those also insert the button text, +called @code{insert-...button}. + +The button-creation functions all take the @code{&rest} argument +@var{properties}, which should be a sequence of @var{property value} +pairs, specifying properties to add to the button; see @ref{Button +Properties}. In addition, the keyword argument @code{:type} may be +used to specify a button-type from which to inherit other properties; +see @ref{Button Types}. Any properties not explicitly specified +during creation will be inherited from the button's type (if the type +defines such a property). + +The following functions add a button using an overlay +(@pxref{Overlays}) to hold the button properties: + +@defun make-button beg end &rest properties +@tindex make-button +Make a button from @var{beg} to @var{end} in the current buffer. +@end defun + +@defun insert-button label &rest properties +@tindex insert-button +Insert a button with the label @var{label}. +@end defun + +The following functions are similar, but use Emacs text-properties +(@pxref{Text Properties}) to hold the button properties, making the +button actually part of the text instead of being a property of the +buffer (using text-properties is usually faster than using overlays, +so this may be preferable when creating large numbers of buttons): + +@defun make-text-button beg end &rest properties +@tindex make-text-button +Make a button from @var{beg} to @var{end} in the current buffer, using +text-properties. +@end defun + +@defun insert-text-button label &rest properties +@tindex insert-text-button +Insert a button with the label @var{label}, using text-properties. +@end defun + +Buttons using text-properties retain no markers into the buffer are +retained, which is important for speed in cases where there are +extremely large numbers of buttons. + +@node Manipulating Buttons +@subsection Manipulating Buttons +@cindex manipulating buttons + +These are functions for getting and setting properties of buttons. +Often these are used by a button's invocation function to determine +what to do. + +Where a @var{button} parameter is specified, it means an object +referring to a specific button, either an overlay (for overlay +buttons), or a buffer-position or marker (for text property buttons). +Such an object is passed as the first argument to a button's +invocation function when it is invoked. + +@defun button-start button +@tindex button-start +Return the position at which @var{button} starts. +@end defun + +@defun button-end button +@tindex button-end +Return the position at which @var{button} ends. +@end defun + +@defun button-get button prop +@tindex button-get +Get the property of button @var{button} named @var{prop}. +@end defun + +@defun button-put button prop val +@tindex button-put +Set @var{button}'s @var{prop} property to @var{val}. +@end defun + +@defun button-activate button &optional use-mouse-action +@tindex button-activate +Call @var{button}'s @code{action} property (i.e., invoke it). If +@var{use-mouse-action} is non-@code{nil}, try to invoke the button's +@code{mouse-action} property instead of @code{action}; if the button +has no @code{mouse-action} property, use @code{action} as normal. +@end defun + +@defun button-label button +@tindex button-label +Return @var{button}'s text label. +@end defun + +@defun button-type button +@tindex button-type +Return @var{button}'s button-type. +@end defun + +@defun button-has-type-p button type +@tindex button-has-type-p +Return @code{t} if @var{button} has button-type @var{type}, or one of +@var{type}'s subtypes. +@end defun + +@defun button-at pos +@tindex button-at +Return the button at position @var{pos} in the current buffer, or @code{nil}. +@end defun + +@node Button Buffer Commands +@subsection Button Buffer Commands +@cindex button buffer commands + +These are commands and functions for locating and operating on +buttons in an Emacs buffer. + +@code{push-button} is the command that a user uses to actually `push' +a button, and is bound by default in the button itself to @key{RET} +and to @key{mouse-2} using a region-specific keymap. Commands +that are useful outside the buttons itself, such as +@code{forward-button} and @code{backward-button} are additionally +available in the keymap stored in @code{button-buffer-map}; a mode +which uses buttons may want to use @code{button-buffer-map} as a +parent keymap for its keymap. + +If the button has a non-@code{nil} @code{follow-link} property, and +@var{mouse-1-click-follows-link} is set, a @key{Mouse-1} click will +also activate the @code{push-button} command. + +@deffn Command push-button &optional pos use-mouse-action +@tindex push-button +Perform the action specified by a button at location @var{pos}. +@var{pos} may be either a buffer position or a mouse-event. If +@var{use-mouse-action} is non-@code{nil}, or @var{pos} is a +mouse-event (@pxref{Mouse Events}), try to invoke the button's +@code{mouse-action} property instead of @code{action}; if the button +has no @code{mouse-action} property, use @code{action} as normal. +@var{pos} defaults to point, except when @code{push-button} is invoked +interactively as the result of a mouse-event, in which case, the mouse +event's position is used. If there's no button at @var{pos}, do +nothing and return @code{nil}, otherwise return @code{t}. +@end deffn + +@deffn Command forward-button n &optional wrap display-message +@tindex forward-button +Move to the @var{n}th next button, or @var{n}th previous button if +@var{n} is negative. If @var{n} is zero, move to the start of any +button at point. If @var{wrap} is non-@code{nil}, moving past either +end of the buffer continues from the other end. If +@var{display-message} is non-@code{nil}, the button's help-echo string +is displayed. Any button with a non-@code{nil} @code{skip} property +is skipped over. Returns the button found. +@end deffn + +@deffn Command backward-button n &optional wrap display-message +@tindex backward-button +Move to the @var{n}th previous button, or @var{n}th next button if +@var{n} is negative. If @var{n} is zero, move to the start of any +button at point. If @var{wrap} is non-@code{nil}, moving past either +end of the buffer continues from the other end. If +@var{display-message} is non-@code{nil}, the button's help-echo string +is displayed. Any button with a non-@code{nil} @code{skip} property +is skipped over. Returns the button found. +@end deffn + +@defun next-button pos &optional count-current +@tindex next-button +Return the next button after position @var{pos} in the current buffer. +If @var{count-current} is non-@code{nil}, count any button at +@var{pos} in the search, instead of starting at the next button. +@end defun + +@defun previous-button pos &optional count-current +@tindex previous-button +Return the @var{n}th button before position @var{pos} in the current +buffer. If @var{count-current} is non-@code{nil}, count any button at +@var{pos} in the search, instead of starting at the next button. +@end defun + +@node Manipulating Button Types +@subsection Manipulating Button Types +@cindex manipulating button types + +@defun button-type-put type prop val +@tindex button-type-put +Set the button-type @var{type}'s @var{prop} property to @var{val}. +@end defun + +@defun button-type-get type prop +@tindex button-type-get +Get the property of button-type @var{type} named @var{prop}. +@end defun + +@defun button-type-subtype-p type supertype +@tindex button-type-subtype-p +Return @code{t} if button-type @var{type} is a subtype of @var{supertype}. +@end defun + @node Blinking @section Blinking Parentheses @cindex parenthesis matching @@ -3091,19 +4444,19 @@ Character code 10 is a newline. 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 non-@code{nil}, these codes map to sequences of two glyphs, where the -first glyph is the @sc{ascii} code for @samp{^}. (A display table can +first glyph is the @acronym{ASCII} code for @samp{^}. (A display table can specify a glyph to use instead of @samp{^}.) Otherwise, these codes map just like the codes in the range 128 to 255. On MS-DOS terminals, Emacs arranges by default for the character code 127 to be mapped to the glyph code 127, which normally displays as an -empty polygon. This glyph is used to display non-@sc{ascii} characters +empty polygon. This glyph is used to display non-@acronym{ASCII} characters that the MS-DOS terminal doesn't support. @xref{MS-DOS and MULE,,, emacs, The GNU Emacs Manual}. @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 +the first glyph is the @acronym{ASCII} code for @samp{\}, and the others are digit characters representing the character code in octal. (A display table can specify a glyph to use instead of @samp{\}.) @@ -3144,14 +4497,6 @@ The value of this variable is the default value for @code{ctl-arrow} in buffers that do not override it. @xref{Default Value}. @end defvar -@defopt indicate-empty-lines -@tindex indicate-empty-lines -@cindex fringes, and empty line indication -When this is non-@code{nil}, Emacs displays a special glyph in -each empty line at the end of the buffer, on terminals that -support it (window systems). -@end defopt - @defopt tab-width The value of this variable is the spacing between tab stops used for displaying tab characters in Emacs buffers. The value is in units of @@ -3160,13 +4505,58 @@ independent of the user-settable tab stops used by the command @code{tab-to-tab-stop}. @xref{Indent Tabs}. @end defopt +@defopt indicate-empty-lines +@tindex indicate-empty-lines +@cindex fringes, and empty line indication +When this is non-@code{nil}, Emacs displays a special glyph in the +fringe of each empty line at the end of the buffer, on terminals that +support it (window systems). @xref{Fringes}. +@end defopt + +@defvar indicate-buffer-boundaries +This buffer-local variable controls how the buffer boundaries and +window scrolling are indicated in the window fringes. + +Emacs can indicate the buffer boundaries---that is, the first and last +line in the buffer---with angle icons when they appear on the screen. +In addition, Emacs can display an up-arrow in the fringe to show +that there is text above the screen, and a down-arrow to show +there is text below the screen. + +There are four kinds of basic values: + +@table @asis +@item @code{nil} +Don't display the icons. +@item @code{left} +Display them in the left fringe. +@item @code{right} +Display them in the right fringe. +@item @var{anything-else} +Display the icon at the top of the window top in the left fringe, and other +in the right fringe. +@end table + +If value is a cons @code{(@var{angles} . @var{arrows})}, @var{angles} +controls the angle icons, and @var{arrows} controls the arrows. Both +@var{angles} and @var{arrows} work according to the table above. +Thus, @code{(t . right)} places the top angle icon in the left +fringe, the bottom angle icon in the right fringe, and both arrows in +the right fringe. +@end defvar + +@defvar default-indicate-buffer-boundaries +The value of this variable is the default value for +@code{indicate-buffer-boundaries} in buffers that do not override it. +@end defvar + @node Display Tables @section Display Tables @cindex display table 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 +European languages that have letters not in the @acronym{ASCII} character set. The display table maps each character code into a sequence of @@ -3179,9 +4569,9 @@ 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. +* 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. @end menu @node Display Table Format @@ -3218,7 +4608,7 @@ in these situations. @item 1 The glyph for the end of a continued line (the default is @samp{\}). Newer Emacs versions, on some platforms, display curved arrows to -indicate truncation---the display table has no effect in these +indicate continuation---the display table has no effect in these situations. @item 2 The glyph for indicating a character displayed as an octal character @@ -3326,17 +4716,36 @@ are defined in the library @file{disp-table}. @cindex glyph A @dfn{glyph} is a generalization of a character; it stands for an image that takes up a single character position on the screen. Glyphs -are represented in Lisp as integers, just as characters are. +are represented in Lisp as integers, just as characters are. Normally +Emacs finds glyphs in the display table (@pxref{Display Tables}). + + A glyph can be @dfn{simple} or it can be defined by the @dfn{glyph +table}. A simple glyph is just a way of specifying a character and a +face to output it in. The glyph code for a simple glyph, mod 524288, +is the character to output, and the glyph code divided by 524288 +specifies the face number (@pxref{Face Functions}) to use while +outputting it. (524288 is +@ifnottex +2**19.) +@end ifnottex +@tex +$2^{19}$.) +@end tex +@xref{Faces}. -@cindex glyph table - The meaning of each integer, as a glyph, is defined by the glyph -table, which is the value of the variable @code{glyph-table}. + On character terminals, you can set up a @dfn{glyph table} to define +the meaning of glyph codes. The glyph codes is the value of the +variable @code{glyph-table}. @defvar glyph-table The value of this variable is the current glyph table. It should be a -vector; the @var{g}th element defines glyph code @var{g}. If the value -is @code{nil} instead of a vector, then all glyphs are simple (see -below). The glyph table is not used on windowed displays. +vector; the @var{g}th element defines glyph code @var{g}. + +If a glyph code is greater than or equal to the length of the glyph +table, that code is automatically simple. If the value of +@code{glyph-table} is @code{nil} instead of a vector, then all glyphs +are simple. The glyph table is not used on graphical displays, only +on character terminals. On graphical displays, all glyphs are simple. @end defvar Here are the possible types of elements in the glyph table: @@ -3349,24 +4758,13 @@ but not under a window system. @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. +can use an alias to specify a face code for the glyph and use a small +number as its code. @item @code{nil} -This glyph is simple. 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 -@ifnottex -2**19.) -@end ifnottex -@tex -$2^{19}$.) -@end tex -@xref{Faces}. +This glyph is simple. @end table - If a glyph code is greater than or equal to the length of the glyph -table, that code is automatically simple. - @defun create-glyph string @tindex create-glyph This function returns a newly-allocated glyph code which is set up to @@ -3448,3 +4846,7 @@ 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. @end defvar + +@ignore + arch-tag: ffdf5714-7ecf-415b-9023-fbc6b409c2c6 +@end ignore