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This is Info file ../../info/lispref.info, produced by Makeinfo version 1.68 from the input file lispref.texi. Edition History: GNU Emacs Lisp Reference Manual Second Edition (v2.01), May 1993 GNU Emacs Lisp Reference Manual Further Revised (v2.02), August 1993 Lucid Emacs Lisp Reference Manual (for 19.10) First Edition, March 1994 XEmacs Lisp Programmer's Manual (for 19.12) Second Edition, April 1995 GNU Emacs Lisp Reference Manual v2.4, June 1995 XEmacs Lisp Programmer's Manual (for 19.13) Third Edition, July 1995 XEmacs Lisp Reference Manual (for 19.14 and 20.0) v3.1, March 1996 XEmacs Lisp Reference Manual (for 19.15 and 20.1, 20.2) v3.2, April, May 1997 Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995 Free Software Foundation, Inc. Copyright (C) 1994, 1995 Sun Microsystems, Inc. Copyright (C) 1995, 1996 Ben Wing. Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that this permission notice may be stated in a translation approved by the Foundation. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided also that the section entitled "GNU General Public License" is included exactly as in the original, and provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that the section entitled "GNU General Public License" may be included in a translation approved by the Free Software Foundation instead of in the original English. File: lispref.info, Node: Glyph Types, Next: Mouse Pointer, Prev: Images, Up: Glyphs Glyph Types =========== Each glyph has a particular type, which controls how the glyph's image is generated. Each glyph type has a corresponding list of allowable image instance types that can be generated. When you call `glyph-image-instance' to retrieve the image instance of a glyph, XEmacs does the equivalent of calling `make-image-instance' and passing in DEST-TYPES the list of allowable image instance types for the glyph's type. * `buffer' glyphs can be used as the begin-glyph or end-glyph of an extent, in the modeline, and in the toolbar. Their image can be instantiated as `nothing', `mono-pixmap', `color-pixmap', `text', and `subwindow'. * `pointer' glyphs can be used to specify the mouse pointer. Their image can be instantiated as `pointer'. * `icon' glyphs can be used to specify the icon used when a frame is iconified. Their image can be instantiated as `mono-pixmap' and `color-pixmap'. - Function: glyph-type GLYPH This function returns the type of the given glyph. The return value will be a symbol, one of `buffer', `pointer', or `icon'. - Function: valid-glyph-type-p GLYPH-TYPE Given a GLYPH-TYPE, this function returns non-`nil' if it is valid. - Function: glyph-type-list This function returns a list of valid glyph types. - Function: buffer-glyph-p OBJECT This function returns non-`nil' if OBJECT is a glyph of type `buffer'. - Function: icon-glyph-p OBJECT This function returns non-`nil' if OBJECT is a glyph of type `icon'. - Function: pointer-glyph-p OBJECT This function returns non-`nil' if OBJECT is a glyph of type `pointer'. File: lispref.info, Node: Mouse Pointer, Next: Redisplay Glyphs, Prev: Glyph Types, Up: Glyphs Mouse Pointer ============= The shape of the mouse pointer when over a particular section of a frame is controlled using various glyph variables. Since the image of a glyph is a specifier, it can be controlled on a per-buffer, per-frame, per-window, or per-device basis. You should use `set-glyph-image' to set the following variables, *not* `setq'. - Glyph: text-pointer-glyph This variable specifies the shape of the mouse pointer when over text. - Glyph: nontext-pointer-glyph This variable specifies the shape of the mouse pointer when over a buffer, but not over text. If unspecified in a particular domain, `text-pointer-glyph' is used. - Glyph: modeline-pointer-glyph This variable specifies the shape of the mouse pointer when over the modeline. If unspecified in a particular domain, `nontext-pointer-glyph' is used. - Glyph: selection-pointer-glyph This variable specifies the shape of the mouse pointer when over a selectable text region. If unspecified in a particular domain, `text-pointer-glyph' is used. - Glyph: gc-pointer-glyph This variable specifies the shape of the mouse pointer when a garbage collection is in progress. If the selected window is on a window system and this glyph specifies a value (i.e. a pointer image instance) in the domain of the selected window, the pointer will be changed as specified during garbage collection. Otherwise, a message will be printed in the echo area, as controlled by `gc-message'. - Glyph: busy-pointer-glyph This variable specifies the shape of the mouse pointer when XEmacs is busy. If unspecified in a particular domain, the pointer is not changed when XEmacs is busy. - Glyph: menubar-pointer-glyph This variable specifies the shape of the mouse pointer when over the menubar. If unspecified in a particular domain, the window-system-provided default pointer is used. - Glyph: scrollbar-pointer-glyph This variable specifies the shape of the mouse pointer when over a scrollbar. If unspecified in a particular domain, the window-system-provided default pointer is used. - Glyph: toolbar-pointer-glyph This variable specifies the shape of the mouse pointer when over a toolbar. If unspecified in a particular domain, `nontext-pointer-glyph' is used. Internally, these variables are implemented in `default-mouse-motion-handler', and thus only take effect when the mouse moves. That function calls `set-frame-pointer', which sets the current mouse pointer for a frame. - Function: set-frame-pointer FRAME IMAGE-INSTANCE This function sets the mouse pointer of FRAME to the given pointer image instance. You should not call this function directly. (If you do, the pointer will change again the next time the mouse moves.) File: lispref.info, Node: Redisplay Glyphs, Next: Subwindows, Prev: Mouse Pointer, Up: Glyphs Redisplay Glyphs ================ - Glyph: truncation-glyph This variable specifies what is displayed at the end of truncated lines. - Glyph: continuation-glyph This variable specifies what is displayed at the end of wrapped lines. - Glyph: octal-escape-glyph This variable specifies what to prefix character codes displayed in octal with. - Glyph: hscroll-glyph This variable specifies what to display at the beginning of horizontally scrolled lines. - Glyph: invisible-text-glyph This variable specifies what to use to indicate the presence of invisible text. This is the glyph that is displayed when an ellipsis is called for, according to `selective-display-ellipses' or `buffer-invisibility-spec'). Normally this is three dots ("..."). - Glyph: control-arrow-glyph This variable specifies what to use as an arrow for control characters. File: lispref.info, Node: Subwindows, Prev: Redisplay Glyphs, Up: Glyphs Subwindows ========== Subwindows are not currently implemented. - Function: subwindowp OBJECT This function returns non-`nil' if OBJECT is a subwindow. File: lispref.info, Node: Annotations, Next: Display, Prev: Glyphs, Up: Top Annotations *********** An "annotation" is a pixmap or string that is not part of a buffer's text but is displayed next to a particular location in a buffer. Annotations can be displayed intermixed with text, in any whitespace at the beginning or end of a line, or in a special area at the left or right side of the frame called a "margin", whose size is controllable. Annotations are implemented using extents (*note Extents::.); but you can work with annotations without knowing how extents work. * Menu: * Annotation Basics:: Introduction to annotations. * Annotation Primitives:: Creating and deleting annotations. * Annotation Properties:: Retrieving and changing the characteristics of an annotation. * Margin Primitives:: Controlling the size of the margins. * Locating Annotations:: Looking for annotations in a buffer. * Annotation Hooks:: Hooks called at certain times during an annotation's lifetime. File: lispref.info, Node: Annotation Basics, Next: Annotation Primitives, Up: Annotations Annotation Basics ================= Marginal annotations are notes associated with a particular location in a buffer. They may be displayed in a margin created on the left-hand or right-hand side of the frame, in any whitespace at the beginning or end of a line, or inside of the text itself. Every annotation may have an associated action to be performed when the annotation is selected. The term "annotation" is used to refer to an individual note. The term "margin" is generically used to refer to the whitespace before the first character on a line or after the last character on a line. Each annotation has the following characteristics: GLYPH This is a glyph object and is used as the displayed representation of the annotation. DOWN-GLYPH If given, this glyph is used as the displayed representation of the annotation when the mouse is pressed down over the annotation. FACE The face with which to display the glyph. SIDE Which side of the text (left or right) the annotation is displayed at. ACTION If non-`nil', this field must contain a function capable of being the first argument to `funcall'. This function is normally evaluated with a single argument, the value of the DATA field, each time the annotation is selected. However, if the WITH-EVENT parameter to `make-annotation' is non-`nil', the function is called with two arguments. The first argument is the same as before, and the second argument is the event (a button-up event, usually) that activated the annotation. DATA Not used internally. This field can contain any E-Lisp object. It is passed as the first argument to ACTION described above. MENU A menu displayed when the right mouse button is pressed over the annotation. The margin is divided into "outside" and "inside". The outside margin is space on the left or right side of the frame which normal text cannot be displayed in. The inside margin is that space between the leftmost or rightmost point at which text can be displayed and where the first or last character actually is. There are four different "layout types" which affect the exact location an annotation appears. `outside-margin' The annotation is placed in the outside margin area. as close as possible to the edge of the frame. If the outside margin is not wide enough for an annotation to fit, it is not displayed. `inside-margin' The annotation is placed in the inside margin area, as close as possible to the edge of the frame. If the inside margin is not wide enough for the annotation to fit, it will be displayed using any available outside margin space if and only if the specifier `use-left-overflow' or `use-right-overflow' (depending on which side the annotation appears in) is non-`nil'. `whitespace' The annotation is placed in the inside margin area, as close as possible to the first or last non-whitespace character on a line. If the inside margin is not wide enough for the annotation to fit, it will be displayed if and only if the specifier `use-left-overflow' or `use-right-overflow' (depending on which side the annotation appears in) is non-`nil'. `text' The annotation is placed at the position it is inserted. It will create enough space for itself inside of the text area. It does not take up a place in the logical buffer, only in the display of the buffer. The current layout policy is that all `whitespace' annotations are displayed first. Next, all `inside-margin' annotations are displayed using any remaining space. Finally as many `outside-margin' annotations are displayed as possible. The `text' annotations will always display as they create their own space to display in. File: lispref.info, Node: Annotation Primitives, Next: Annotation Properties, Prev: Annotation Basics, Up: Annotations Annotation Primitives ===================== - Function: make-annotation GLYPH &optional POSITION LAYOUT BUFFER WITH-EVENT D-GLYPH RIGHTP This function creates a marginal annotation at position POS in BUFFER. The annotation is displayed using GLYPH, which should be a glyph object or a string, and is positioned using layout policy LAYOUT. If POS is `nil', point is used. If LAYOUT is `nil', `whitespace' is used. If BUFFER is `nil', the current buffer is used. If WITH-EVENT is non-`nil', then when an annotation is activated, the triggering event is passed as the second arg to the annotation function. If D-GLYPH is non-`nil' then it is used as the glyph that will be displayed when button1 is down. If RIGHTP is non-`nil' then the glyph will be displayed on the right side of the buffer instead of the left. The newly created annotation is returned. - Function: delete-annotation ANNOTATION This function removes ANNOTATION from its buffer. This does not modify the buffer text. - Function: annotationp ANNOTATION This function returns `t' if ANNOTATION is an annotation, `nil' otherwise. File: lispref.info, Node: Annotation Properties, Next: Margin Primitives, Prev: Annotation Primitives, Up: Annotations Annotation Properties ===================== - Function: annotation-glyph ANNOTATION This function returns the glyph object used to display ANNOTATION. - Function: set-annotation-glyph ANNOTATION GLYPH &optional LAYOUT SIDE This function sets the glyph of ANNOTATION to GLYPH, which should be a glyph object. If LAYOUT is non-`nil', set the layout policy of ANNOTATION to LAYOUT. If SIDE is `left' or `right', change the side of the buffer at which the annotation is displayed to the given side. The new value of `annotation-glyph' is returned. - Function: annotation-down-glyph ANNOTATION This function returns the glyph used to display ANNOTATION when the left mouse button is depressed on the annotation. - Function: set-annotation-down-glyph ANNOTATION GLYPH This function returns the glyph used to display ANNOTATION when the left mouse button is depressed on the annotation to GLYPH, which should be a glyph object. - Function: annotation-face ANNOTATION This function returns the face associated with ANNOTATION. - Function: set-annotation-face ANNOTATION FACE This function sets the face associated with ANNOTATION to FACE. - Function: annotation-layout ANNOTATION This function returns the layout policy of ANNOTATION. - Function: set-annotation-layout ANNOTATION LAYOUT This function sets the layout policy of ANNOTATION to LAYOUT. - Function: annotation-side ANNOTATION This function returns the side of the buffer that ANNOTATION is displayed on. Return value is a symbol, either `left' or `right'. - Function: annotation-data ANNOTATION This function returns the data associated with ANNOTATION. - Function: set-annotation-data ANNOTATION DATA This function sets the data field of ANNOTATION to DATA. DATA is returned. - Function: annotation-action ANNOTATION This function returns the action associated with ANNOTATION. - Function: set-annotation-action ANNOTATION ACTION This function sets the action field of ANNOTATION to ACTION. ACTION is returned.. - Function: annotation-menu ANNOTATION This function returns the menu associated with ANNOTATION. - Function: set-annotation-menu ANNOTATION MENU This function sets the menu associated with ANNOTATION to MENU. This menu will be displayed when the right mouse button is pressed over the annotation. - Function: annotation-visible ANNOTATION This function returns `t' if there is enough available space to display ANNOTATION, `nil' otherwise. - Function: annotation-width ANNOTATION This function returns the width of ANNOTATION in pixels. - Function: hide-annotation ANNOTATION This function removes ANNOTATION's glyph, making it invisible. - Function: reveal-annotation ANNOTATION This function restores ANNOTATION's glyph, making it visible. File: lispref.info, Node: Locating Annotations, Next: Annotation Hooks, Prev: Margin Primitives, Up: Annotations Locating Annotations ==================== - Function: annotations-in-region START END BUFFER This function returns a list of all annotations in BUFFER which are between START and END inclusively. - Function: annotations-at &optional POSITION BUFFER This function returns a list of all annotations at POSITION in BUFFER. If POSITION is `nil' point is used. If BUFFER is `nil' the current buffer is used. - Function: annotation-list &optional BUFFER This function returns a list of all annotations in BUFFER. If BUFFER is `nil', the current buffer is used. - Function: all-annotations This function returns a list of all annotations in all buffers in existence. File: lispref.info, Node: Margin Primitives, Next: Locating Annotations, Prev: Annotation Properties, Up: Annotations Margin Primitives ================= The margin widths are controllable on a buffer-local, window-local, frame-local, device-local, or device-type-local basis through the use of specifiers. *Note Specifiers::. - Specifier: left-margin-width This is a specifier variable controlling the width of the left outside margin, in characters. Use `set-specifier' to change its value. - Specifier: right-margin-width This is a specifier variable controlling the width of the right outside margin, in characters. Use `set-specifier' to change its value. - Specifier: use-left-overflow If non-`nil', use the left outside margin as extra whitespace when displaying `whitespace' and `inside-margin' annotations. Defaults to `nil'. This is a specifier variable; use `set-specifier' to change its value. - Specifier: use-right-overflow If non-`nil', use the right outside margin as extra whitespace when displaying `whitespace' and `inside-margin' annotations. Defaults to `nil'. This is a specifier variable; use `set-specifier' to change its value. - Function: window-left-margin-pixel-width &optional WINDOW This function returns the width in pixels of the left outside margin of WINDOW. If WINDOW is `nil', the selected window is assumed. - Function: window-right-margin-pixel-width &optional WINDOW This function returns the width in pixels of the right outside margin of WINDOW. If WINDOW is `nil', the selected window is assumed. The margin colors are controlled by the faces `left-margin' and `right-margin'. These can be set using the X resources `Emacs.left-margin.background' and `Emacs.left-margin.foreground'; likewise for the right margin. File: lispref.info, Node: Annotation Hooks, Prev: Locating Annotations, Up: Annotations Annotation Hooks ================ The following three hooks are provided for use with the marginal annotations: `before-delete-annotation-hook' This hook is called immediately before an annotation is destroyed. It is passed a single argument, the annotation being destroyed. `after-delete-annotation-hook' This normal hook is called immediately after an annotation is destroyed. `make-annotation-hook' This hook is called immediately after an annotation is created. It is passed a single argument, the newly created annotation. File: lispref.info, Node: Display, Next: Hash Tables, Prev: Annotations, Up: Top Emacs Display ************* This chapter describes a number of other features related to the display that XEmacs presents to the user. * Menu: * Refresh Screen:: Clearing the screen and redrawing everything on it. * Truncation:: Folding or wrapping long text lines. * The Echo Area:: Where messages are displayed. * 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. * Blinking:: How XEmacs shows the matching open parenthesis. * Usual Display:: The usual conventions for displaying nonprinting chars. * Display Tables:: How to specify other conventions. * Beeping:: Audible signal to the user. File: lispref.info, Node: Refresh Screen, Next: Truncation, Up: Display Refreshing the Screen ===================== The function `redraw-frame' redisplays the entire contents of a given frame. *Note Frames::. - Function: redraw-frame FRAME This function clears and redisplays frame FRAME. Even more powerful is `redraw-display': - Command: redraw-display &optional DEVICE This function redraws all frames on DEVICE marked as having their image garbled. DEVICE defaults to the selected device. If DEVICE is `t', all devices will have their frames checked. Processing user input takes absolute priority over redisplay. If you call these functions when input is available, they do nothing immediately, but a full redisplay does happen eventually--after all the input has been processed. Normally, suspending and resuming XEmacs also refreshes the screen. Some terminal emulators record separate contents for display-oriented programs such as XEmacs and for ordinary sequential display. If you are using such a terminal, you might want to inhibit the redisplay on resumption. *Note Suspending XEmacs::. - Variable: no-redraw-on-reenter This variable controls whether XEmacs redraws the entire screen after it has been suspended and resumed. Non-`nil' means yes, `nil' means no. The above functions do not actually cause the display to be updated; rather, they clear out the internal display records that XEmacs maintains, so that the next time the display is updated it will be redrawn from scratch. Normally this occurs the next time that `next-event' or `sit-for' is called; however, a display update will not occur if there is input pending. *Note Command Loop::. - Command: force-redisplay This function causes an immediate update of the display in all circumstances, whether or not input is pending. (This function does not exist in FSF Emacs.) - Function: force-cursor-redisplay This function causes an immediate update of the cursor on the selected frame. (This function does not exist in FSF Emacs.) File: lispref.info, Node: Truncation, Next: The Echo Area, Prev: Refresh Screen, Up: Display Truncation ========== When a line of text extends beyond the right edge of a window, the line can either be truncated or continued on the next line. When a line is truncated, this is normally shown with a `\' in the rightmost column of the window on X displays, and with a `$' on TTY devices. When a line is continued or "wrapped" onto the next line, this is shown with a curved arrow in the rightmost column of the window (or with a `\' on TTY devices). The additional screen lines used to display a long text line are called "continuation" lines. Normally, whenever line truncation is in effect for a particular window, a horizontal scrollbar is displayed in that window if the device supports scrollbars. *Note Scrollbars::. Note that continuation is different from filling; continuation happens on the screen only, not in the buffer contents, and it breaks a line precisely at the right margin, not at a word boundary. *Note Filling::. - User Option: truncate-lines This buffer-local variable controls how XEmacs displays lines that extend beyond the right edge of the window. If it is non-`nil', then XEmacs does not display continuation lines; rather each line of text occupies exactly one screen line, and a backslash appears at the edge of any line that extends to or beyond the edge of the window. The default is `nil'. If the variable `truncate-partial-width-windows' is non-`nil', then truncation is always used for side-by-side windows (within one frame) regardless of the value of `truncate-lines'. - User Option: default-truncate-lines This variable is the default value for `truncate-lines', for buffers that do not have local values for it. - User Option: truncate-partial-width-windows This variable controls display of lines that extend beyond the right edge of the window, in side-by-side windows (*note Splitting Windows::.). If it is non-`nil', these lines are truncated; otherwise, `truncate-lines' says what to do with them. The backslash and curved arrow used to indicate truncated or continued lines are only defaults, and can be changed. These images are actually glyphs (*note Glyphs::.). XEmacs provides a great deal of flexibility in how glyphs can be controlled. (This differs from FSF Emacs, which uses display tables to control these images.) For details, *Note Redisplay Glyphs::. File: lispref.info, Node: The Echo Area, Next: Invisible Text, Prev: Truncation, Up: Display The Echo Area ============= The "echo area" is used for displaying messages made with the `message' primitive, and for echoing keystrokes. It is not the same as the minibuffer, despite the fact that the minibuffer appears (when active) in the same place on the screen as the echo area. The `XEmacs Reference Manual' specifies the rules for resolving conflicts between the echo area and the minibuffer for use of that screen space (*note The Minibuffer: (emacs)Minibuffer.). Error messages appear in the echo area; see *Note Errors::. You can write output in the echo area by using the Lisp printing functions with `t' as the stream (*note Output Functions::.), or as follows: - Function: message STRING &rest ARGUMENTS This function displays a one-line message in the echo area. The argument STRING is similar to a C language `printf' control string. See `format' in *Note String Conversion::, for the details on the conversion specifications. `message' returns the constructed string. In batch mode, `message' prints the message text on the standard error stream, followed by a newline. If STRING is `nil', `message' clears the echo area. If the minibuffer is active, this brings the minibuffer contents back onto the screen immediately. (message "Minibuffer depth is %d." (minibuffer-depth)) -| Minibuffer depth is 0. => "Minibuffer depth is 0." ---------- Echo Area ---------- Minibuffer depth is 0. ---------- Echo Area ---------- Some of the messages displayed in the echo area are also recorded in the ` *Message-Log*' buffer. - User Option: log-message-max-size This variable specifies the maximum size of `* Message-Log*' buffer. - Variable: echo-keystrokes This variable determines how much time should elapse before command characters echo. Its value must be an integer, which specifies the number of seconds to wait before echoing. If the user types a prefix key (such as `C-x') and then delays this many seconds before continuing, the prefix key is echoed in the echo area. Any subsequent characters in the same command will be echoed as well. If the value is zero, then command input is not echoed. - Variable: cursor-in-echo-area This variable controls where the cursor appears when a message is displayed in the echo area. If it is non-`nil', then the cursor appears at the end of the message. Otherwise, the cursor appears at point--not in the echo area at all. The value is normally `nil'; Lisp programs bind it to `t' for brief periods of time. File: lispref.info, Node: Invisible Text, Next: Selective Display, Prev: The Echo Area, Up: Display Invisible Text ============== You can make characters "invisible", so that they do not appear on the screen, with the `invisible' property. This can be either a text property or a property of an overlay. In the simplest case, any non-`nil' `invisible' property makes a character invisible. This is the default case--if you don't alter the default value of `buffer-invisibility-spec', this is how the `invisibility' property works. This feature is much like selective display (*note Selective Display::.), but more general and cleaner. More generally, you can use the variable `buffer-invisibility-spec' to control which values of the `invisible' property make text invisible. This permits you to classify the text into different subsets in advance, by giving them different `invisible' values, and subsequently make various subsets visible or invisible by changing the value of `buffer-invisibility-spec'. Controlling visibility with `buffer-invisibility-spec' is especially useful in a program to display the list of entries in a data base. It permits the implementation of convenient filtering commands to view just a part of the entries in the data base. Setting this variable is very fast, much faster than scanning all the text in the buffer looking for properties to change. - Variable: buffer-invisibility-spec This variable specifies which kinds of `invisible' properties actually make a character invisible. `t' A character is invisible if its `invisible' property is non-`nil'. This is the default. a list Each element of the list makes certain characters invisible. Ultimately, a character is invisible if any of the elements of this list applies to it. The list can have two kinds of elements: `ATOM' A character is invisible if its `invisible' propery value is ATOM or if it is a list with ATOM as a member. `(ATOM . t)' A character is invisible if its `invisible' propery value is ATOM or if it is a list with ATOM as a member. Moreover, if this character is at the end of a line and is followed by a visible newline, it displays an ellipsis. Ordinarily, commands that operate on text or move point do not care whether the text is invisible. However, the user-level line motion commands explicitly ignore invisible newlines. File: lispref.info, Node: Selective Display, Next: Overlay Arrow, Prev: Invisible Text, Up: Display Selective Display ================= "Selective display" is a pair of features that hide certain lines on the screen. The first variant, explicit selective display, is designed for use in a Lisp program. The program controls which lines are hidden by altering the text. Outline mode has traditionally used this variant. It has been partially replaced by the invisible text feature (*note Invisible Text::.); there is a new version of Outline mode which uses that instead. In the second variant, the choice of lines to hide is made automatically based on indentation. This variant is designed to be a user-level feature. The way you control explicit selective display is by replacing a newline (control-j) with a carriage return (control-m). The text that was formerly a line following that newline is now invisible. Strictly speaking, it is temporarily no longer a line at all, since only newlines can separate lines; it is now part of the previous line. Selective display does not directly affect editing commands. For example, `C-f' (`forward-char') moves point unhesitatingly into invisible text. However, the replacement of newline characters with carriage return characters affects some editing commands. For example, `next-line' skips invisible lines, since it searches only for newlines. Modes that use selective display can also define commands that take account of the newlines, or that make parts of the text visible or invisible. When you write a selectively displayed buffer into a file, all the control-m's are output as newlines. This means that when you next read in the file, it looks OK, with nothing invisible. The selective display effect is seen only within XEmacs. - Variable: selective-display This buffer-local variable enables selective display. This means that lines, or portions of lines, may be made invisible. * If the value of `selective-display' is `t', then any portion of a line that follows a control-m is not displayed. * If the value of `selective-display' is a positive integer, then lines that start with more than that many columns of indentation are not displayed. When some portion of a buffer is invisible, the vertical movement commands operate as if that portion did not exist, allowing a single `next-line' command to skip any number of invisible lines. However, character movement commands (such as `forward-char') do not skip the invisible portion, and it is possible (if tricky) to insert or delete text in an invisible portion. In the examples below, we show the *display appearance* of the buffer `foo', which changes with the value of `selective-display'. The *contents* of the buffer do not change. (setq selective-display nil) => nil ---------- Buffer: foo ---------- 1 on this column 2on this column 3n this column 3n this column 2on this column 1 on this column ---------- Buffer: foo ---------- (setq selective-display 2) => 2 ---------- Buffer: foo ---------- 1 on this column 2on this column 2on this column 1 on this column ---------- Buffer: foo ---------- - Variable: selective-display-ellipses If this buffer-local variable is non-`nil', then XEmacs displays `...' at the end of a line that is followed by invisible text. This example is a continuation of the previous one. (setq selective-display-ellipses t) => t ---------- Buffer: foo ---------- 1 on this column 2on this column ... 2on this column 1 on this column ---------- Buffer: foo ---------- You can use a display table to substitute other text for the ellipsis (`...'). *Note Display Tables::. File: lispref.info, Node: Overlay Arrow, Next: Temporary Displays, Prev: Selective Display, Up: Display The Overlay Arrow ================= The "overlay arrow" is useful for directing the user's attention to a particular line in a buffer. For example, in the modes used for interface to debuggers, the overlay arrow indicates the line of code about to be executed. - Variable: overlay-arrow-string This variable holds the string to display to call attention to a particular line, or `nil' if the arrow feature is not in use. Despite its name, the value of this variable can be either a string or a glyph (*note Glyphs::.). - Variable: overlay-arrow-position This variable holds a marker that indicates where to display the overlay arrow. It should point at the beginning of a line. The arrow text appears at the beginning of that line, overlaying any text that would otherwise appear. Since the arrow is usually short, and the line usually begins with indentation, normally nothing significant is overwritten. The overlay string is displayed only in the buffer that this marker points into. Thus, only one buffer can have an overlay arrow at any given time. You can do the same job by creating an extent with a `begin-glyph' property. *Note Extent Properties::. File: lispref.info, Node: Temporary Displays, Next: Blinking, Prev: Overlay Arrow, Up: Display Temporary Displays ================== Temporary displays are used by commands to put output into a buffer and then present it to the user for perusal rather than for editing. Many of the help commands use this feature. - Special Form: with-output-to-temp-buffer BUFFER-NAME FORMS... This function executes FORMS while arranging to insert any output they print into the buffer named BUFFER-NAME. The buffer is then shown in some window for viewing, displayed but not selected. The string BUFFER-NAME specifies the temporary buffer, which need not already exist. The argument must be a string, not a buffer. The buffer is erased initially (with no questions asked), and it is marked as unmodified after `with-output-to-temp-buffer' exits. `with-output-to-temp-buffer' binds `standard-output' to the temporary buffer, then it evaluates the forms in FORMS. Output using the Lisp output functions within FORMS goes by default to that buffer (but screen display and messages in the echo area, although they are "output" in the general sense of the word, are not affected). *Note Output Functions::. The value of the last form in FORMS is returned. ---------- Buffer: foo ---------- This is the contents of foo. ---------- Buffer: foo ---------- (with-output-to-temp-buffer "foo" (print 20) (print standard-output)) => #<buffer foo> ---------- Buffer: foo ---------- 20 #<buffer foo> ---------- Buffer: foo ---------- - Variable: temp-buffer-show-function If this variable is non-`nil', `with-output-to-temp-buffer' calls it as a function to do the job of displaying a help buffer. The function gets one argument, which is the buffer it should display. In Emacs versions 18 and earlier, this variable was called `temp-buffer-show-hook'. - Function: momentary-string-display STRING POSITION &optional CHAR MESSAGE This function momentarily displays STRING in the current buffer at POSITION. It has no effect on the undo list or on the buffer's modification status. The momentary display remains until the next input event. If the next input event is CHAR, `momentary-string-display' ignores it and returns. Otherwise, that event remains buffered for subsequent use as input. Thus, typing CHAR will simply remove the string from the display, while typing (say) `C-f' will remove the string from the display and later (presumably) move point forward. The argument CHAR is a space by default. The return value of `momentary-string-display' is not meaningful. You can do the same job in a more general way by creating an extent with a begin-glyph property. *Note Extent Properties::. If MESSAGE is non-`nil', it is displayed in the echo area while STRING is displayed in the buffer. If it is `nil', a default message says to type CHAR to continue. In this example, point is initially located at the beginning of the second line: ---------- Buffer: foo ---------- This is the contents of foo. -!-Second line. ---------- Buffer: foo ---------- (momentary-string-display "**** Important Message! ****" (point) ?\r "Type RET when done reading") => t ---------- Buffer: foo ---------- This is the contents of foo. **** Important Message! ****Second line. ---------- Buffer: foo ---------- ---------- Echo Area ---------- Type RET when done reading ---------- Echo Area ---------- This function works by actually changing the text in the buffer. As a result, if you later undo in this buffer, you will see the message come and go. File: lispref.info, Node: Blinking, Next: Usual Display, Prev: Temporary Displays, Up: Display Blinking Parentheses ==================== This section describes the mechanism by which XEmacs shows a matching open parenthesis when the user inserts a close parenthesis. - Variable: blink-paren-function The value of this variable should be a function (of no arguments) to be called whenever a character with close parenthesis syntax is inserted. The value of `blink-paren-function' may be `nil', in which case nothing is done. *Please note:* This variable was named `blink-paren-hook' in older Emacs versions, but since it is not called with the standard convention for hooks, it was renamed to `blink-paren-function' in version 19. - Variable: blink-matching-paren If this variable is `nil', then `blink-matching-open' does nothing. - Variable: blink-matching-paren-distance This variable specifies the maximum distance to scan for a matching parenthesis before giving up. - Variable: blink-matching-paren-delay This variable specifies the number of seconds for the cursor to remain at the matching parenthesis. A fraction of a second often gives good results, but the default is 1, which works on all systems. - Function: blink-matching-open This function is the default value of `blink-paren-function'. It assumes that point follows a character with close parenthesis syntax and moves the cursor momentarily to the matching opening character. If that character is not already on the screen, it displays the character's context in the echo area. To avoid long delays, this function does not search farther than `blink-matching-paren-distance' characters. Here is an example of calling this function explicitly. (defun interactive-blink-matching-open () "Indicate momentarily the start of sexp before point." (interactive) (let ((blink-matching-paren-distance (buffer-size)) (blink-matching-paren t)) (blink-matching-open))) File: lispref.info, Node: Usual Display, Next: Display Tables, Prev: Blinking, Up: Display Usual Display Conventions ========================= The usual display conventions define how to display each character code. You can override these conventions by setting up a display table (*note Display Tables::.). Here are the usual display conventions: * Character codes 32 through 126 map to glyph codes 32 through 126. Normally this means they display as themselves. * Character code 9 is a horizontal tab. It displays as whitespace up to a position determined by `tab-width'. * 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 `ctl-arrow'. If it is non-`nil', these codes map to sequences of two glyphs, where the first glyph is the ASCII code for `^'. (A display table can specify a glyph to use instead of `^'.) Otherwise, these codes map just like the codes in the range 128 to 255. * Character codes 128 through 255 map to sequences of four glyphs, where the first glyph is the ASCII code for `\', and the others are digit characters representing the code in octal. (A display table can specify a glyph to use instead of `\'.) The usual display conventions apply even when there is a display table, for any character whose entry in the active display table is `nil'. Thus, when you set up a display table, you need only specify the characters for which you want unusual behavior. These variables affect the way certain characters are displayed on the screen. Since they change the number of columns the characters occupy, they also affect the indentation functions. - User Option: ctl-arrow This buffer-local variable controls how control characters are displayed. If it is non-`nil', they are displayed as a caret followed by the character: `^A'. If it is `nil', they are displayed as a backslash followed by three octal digits: `\001'. - Variable: default-ctl-arrow The value of this variable is the default value for `ctl-arrow' in buffers that do not override it. *Note Default Value::. - User Option: tab-width The value of this variable is the spacing between tab stops used for displaying tab characters in Emacs buffers. The default is 8. Note that this feature is completely independent from the user-settable tab stops used by the command `tab-to-tab-stop'. *Note Indent Tabs::. File: lispref.info, Node: Display Tables, Next: Beeping, Prev: Usual Display, Up: Display Display Tables ============== You can use the "display table" feature to control how all 256 possible character codes display on the screen. This is useful for displaying European languages that have letters not in the ASCII character set. The display table maps each character code into a sequence of "runes", each rune being an image that takes up one character position on the screen. You can also define how to display each rune on your terminal, using the "rune table". * Menu: * Display Table Format:: What a display table consists of. * Active Display Table:: How XEmacs selects a display table to use. * Character Descriptors:: Format of an individual element of a display table. File: lispref.info, Node: Display Table Format, Next: Active Display Table, Up: Display Tables Display Table Format -------------------- A display table is an array of 256 elements. (In FSF Emacs, a display table is 262 elements. The six extra elements specify the truncation and continuation glyphs, etc. This method is very kludgey, and in XEmacs the variables `truncation-glyph', `continuation-glyph', etc. are used. *Note Truncation::.) - Function: make-display-table This creates and returns a display table. The table initially has `nil' in all elements. The 256 elements correspond to character codes; the Nth element says how to display the character code N. The value should be `nil', a string, a glyph, or a vector of strings and glyphs (*note Character Descriptors::.). If an element is `nil', it says to display that character according to the usual display conventions (*note Usual Display::.). If you use the display table to change the display of newline characters, the whole buffer will be displayed as one long "line." For example, here is how to construct a display table that mimics the effect of setting `ctl-arrow' to a non-`nil' value: (setq disptab (make-display-table)) (let ((i 0)) (while (< i 32) (or (= i ?\t) (= i ?\n) (aset disptab i (concat "^" (char-to-string (+ i 64))))) (setq i (1+ i))) (aset disptab 127 "^?")) File: lispref.info, Node: Active Display Table, Next: Character Descriptors, Prev: Display Table Format, Up: Display Tables Active Display Table -------------------- The active display table is controlled by the variable `current-display-table'. This is a specifier, which means that you can specify separate values for it in individual buffers, windows, frames, and devices, as well as a global value. It also means that you cannot set this variable using `setq'; use `set-specifier' instead. *Note Specifiers::. (FSF Emacs uses `window-display-table', `buffer-display-table', `standard-display-table', etc. to control the display table. However, specifiers are a cleaner and more powerful way of doing the same thing. FSF Emacs also uses a different format for the contents of a display table, using additional indirection to a "glyph table" and such. Note that "glyph" has a different meaning in XEmacs.) Individual faces can also specify an overriding display table; this is set using `set-face-display-table'. *Note Faces::. If no display table can be determined for a particular window, then XEmacs uses the usual display conventions. *Note Usual Display::. File: lispref.info, Node: Character Descriptors, Prev: Active Display Table, Up: Display Tables Character Descriptors --------------------- Each element of the display-table vector describes how to display a particular character and is called a "character descriptor". A character descriptor can be: a string Display this particular string wherever the character is to be displayed. a glyph Display this particular glyph wherever the character is to be displayed. a vector The vector may contain strings and/or glyphs. Display the elements of the vector one after another wherever the character is to be displayed. `nil' Display according to the standard interpretation (*note Usual Display::.).