@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
-@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998 Free Software Foundation, Inc.
+@c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2000
+@c Free Software Foundation, Inc.
@c See the file elisp.texi for copying conditions.
@setfilename ../info/text
@node Text, Non-ASCII Characters, Markers, Top
This chapter describes the functions that deal with the text in a
buffer. Most examine, insert, or delete text in the current buffer,
-often in the vicinity of point. Many are interactive. All the
-functions that change the text provide for undoing the changes
-(@pxref{Undo}).
+often operating at point or on text adjacent to point. Many are
+interactive. All the functions that change the text provide for undoing
+the changes (@pxref{Undo}).
Many text-related functions operate on a region of text defined by two
buffer positions passed in arguments named @var{start} and @var{end}.
@cindex buffer contents
Throughout this chapter, ``text'' refers to the characters in the
-buffer, together with their properties (when relevant).
+buffer, together with their properties (when relevant). Keep in mind
+that point is always between two characters, and the cursor appears on
+the character after point.
@menu
* Near Point:: Examining text in the vicinity of point.
How to control how much information is kept.
* Filling:: Functions for explicit filling.
* Margins:: How to specify margins for filling commands.
+* Adaptive Fill:: Adaptive Fill mode chooses a fill prefix from context.
* Auto Filling:: How auto-fill mode is implemented to break lines.
* Sorting:: Functions for sorting parts of the buffer.
* Columns:: Computing horizontal positions, and using them.
* Transposition:: Swapping two portions of a buffer.
* Registers:: How registers are implemented. Accessing the text or
position stored in a register.
+* Base 64:: Conversion to or from base 64 encoding.
* Change Hooks:: Supplying functions to be run when text is changed.
@end menu
Several simple functions are described here. See also @code{looking-at}
in @ref{Regexp Search}.
-@defun char-after position
+@defun char-after &optional position
This function returns the character in the current buffer at (i.e.,
immediately after) position @var{position}. If @var{position} is out of
range for this purpose, either before the beginning of the buffer, or at
-or beyond the end, then the value is @code{nil}.
+or beyond the end, then the value is @code{nil}. The default for
+@var{position} is point.
In the following example, assume that the first character in the
buffer is @samp{@@}:
@end example
@end defun
-@defun char-before position
+@defun char-before &optional position
This function returns the character in the current buffer immediately
before position @var{position}. If @var{position} is out of range for
this purpose, either before the beginning of the buffer, or at or beyond
-the end, then the value is @code{nil}.
+the end, then the value is @code{nil}. The default for
+@var{position} is point.
@end defun
@defun following-char
at the second character.
@example
-(compare-buffer-substring nil 6 11 nil 16 21)
+(compare-buffer-substrings nil 6 11 nil 16 21)
@result{} 2
@end example
@end defun
type.
Insertion functions signal an error if the current buffer is
-read-only.
+read-only or if they insert within read-only text.
These functions copy text characters from strings and buffers along
with their properties. The inserted characters have exactly the same
In an interactive call, @var{count} is the numeric prefix argument.
This command calls @code{auto-fill-function} whenever that is
-non-@code{nil} and the character inserted is a space or a newline
-(@pxref{Auto Filling}).
+non-@code{nil} and the character inserted is in the table
+@code{auto-fill-chars} (@pxref{Auto Filling}).
@c Cross refs reworded to prevent overfull hbox. --rjc 15mar92
This command performs abbrev expansion if Abbrev mode is enabled and
This is also responsible for calling @code{blink-paren-function} when
the inserted character has close parenthesis syntax (@pxref{Blinking}).
+
+Do not try substituting your own definition of
+@code{self-insert-command} for the standard one. The editor command
+loop handles this function specially.
@end deffn
@deffn Command newline &optional number-of-newlines
@end deffn
@defvar overwrite-mode
-This variable controls whether overwrite mode is in effect: a
-non-@code{nil} value enables the mode. It is automatically made
-buffer-local when set in any fashion.
+This variable controls whether overwrite mode is in effect. The value
+should be @code{overwrite-mode-textual}, @code{overwrite-mode-binary},
+or @code{nil}. @code{overwrite-mode-textual} specifies textual
+overwrite mode (treats newlines and tabs specially), and
+@code{overwrite-mode-binary} specifies binary overwrite mode (treats
+newlines and tabs like any other characters).
@end defvar
@node Deletion
All of the deletion functions operate on the current buffer, and all
return a value of @code{nil}.
-@defun erase-buffer
+@deffn Command erase-buffer
This function deletes the entire text of the current buffer, leaving it
empty. If the buffer is read-only, it signals a @code{buffer-read-only}
-error. Otherwise, it deletes the text without asking for any
-confirmation. It returns @code{nil}.
+error; if some of the text in it is read-only, it signals a
+@code{text-read-only} error. Otherwise, it deletes the text without
+asking for any confirmation. It returns @code{nil}.
Normally, deleting a large amount of text from a buffer inhibits further
auto-saving of that buffer ``because it has shrunk''. However,
@code{erase-buffer} does not do this, the idea being that the future
text is not really related to the former text, and its size should not
be compared with that of the former text.
-@end defun
+@end deffn
@deffn Command delete-region start end
-This command deletes the text in the current buffer in the region
-defined by @var{start} and @var{end}. The value is @code{nil}. If
-point was inside the deleted region, its value afterward is @var{start}.
+This command deletes the text between positions @var{start} and
+@var{end} in the current buffer, and returns @code{nil}. If point was
+inside the deleted region, its value afterward is @var{start}.
Otherwise, point relocates with the surrounding text, as markers do.
@end deffn
+@defun delete-and-extract-region start end
+@tindex delete-and-extract-region
+This function deletes the text between positions @var{start} and
+@var{end} in the current buffer, and returns a string containing the
+text just deleted.
+
+If point was inside the deleted region, its value afterward is
+@var{start}. Otherwise, point relocates with the surrounding text, as
+markers do.
+@end defun
+
@deffn Command delete-char count &optional killp
This command deletes @var{count} characters directly after point, or
before point if @var{count} is negative. If @var{killp} is
@end deffn
@defopt backward-delete-char-untabify-method
-@tindex backward-delete-char-untabify-method
This option specifies how @code{backward-delete-char-untabify} should
deal with whitespace. Possible values include @code{untabify}, the
default, meaning convert a tab to many spaces and delete one;
the mark.
@c Emacs 19 feature
-If the buffer is read-only, @code{kill-region} modifies the kill ring
-just the same, then signals an error without modifying the buffer. This
-is convenient because it lets the user use all the kill commands to copy
-text into the kill ring from a read-only buffer.
+If the buffer or text is read-only, @code{kill-region} modifies the kill
+ring just the same, then signals an error without modifying the buffer.
+This is convenient because it lets the user use a series of kill
+commands to copy text from a read-only buffer into the kill ring.
@end deffn
+@defopt kill-read-only-ok
+If this option is non-@code{nil}, @code{kill-region} does not signal an
+error if the buffer or text is read-only. Instead, it simply returns,
+updating the kill ring but not changing the buffer.
+@end defopt
+
@deffn Command copy-region-as-kill start end
This command saves the region defined by @var{start} and @var{end} on
the kill ring (including text properties), but does not delete the text
Here are the kinds of elements an undo list can have:
@table @code
-@item @var{integer}
-This kind of element records a previous value of point. Ordinary cursor
-motion does not get any sort of undo record, but deletion operations use
-these entries to record where point was before the command.
+@item @var{position}
+This kind of element records a previous value of point; undoing this
+element moves point to @var{position}. Ordinary cursor motion does not
+make any sort of undo record, but deletion operations use these entries
+to record where point was before the command.
@item (@var{beg} . @var{end})
This kind of element indicates how to delete text that was inserted.
@var{adjustment} character positions. Undoing this element moves
@var{marker} @minus{} @var{adjustment} characters.
-@item @var{position}
-This element indicates where point was at an earlier time. Undoing this
-element sets point to @var{position}. Deletion normally creates an
-element of this kind as well as a reinsertion element.
-
@item nil
This element is a boundary. The elements between two boundaries are
called a @dfn{change group}; normally, each change group corresponds to
boundaries. @xref{Paragraphs,,, emacs, The Emacs Manual}.
@end deffn
-@deffn Command fill-region start end &optional justify
+@deffn Command fill-region start end &optional justify nosqueeze to-eop
This command fills each of the paragraphs in the region from @var{start}
to @var{end}. It justifies as well if @var{justify} is
non-@code{nil}.
+If @var{nosqueeze} is non-@code{nil}, that means to leave whitespace
+other than line breaks untouched. If @var{to-eop} is non-@code{nil},
+that means to keep filling to the end of the paragraph---or the next hard
+newline, if @code{use-hard-newlines} is enabled (see below).
+
The variable @code{paragraph-separate} controls how to distinguish
paragraphs. @xref{Standard Regexps}.
@end deffn
-@deffn Command fill-individual-paragraphs start end &optional justify mail-flag
+@deffn Command fill-individual-paragraphs start end &optional justify citation-regexp
This command fills each paragraph in the region according to its
individual fill prefix. Thus, if the lines of a paragraph were indented
with spaces, the filled paragraph will remain indented in the same
The first two arguments, @var{start} and @var{end}, are the beginning
and end of the region to be filled. The third and fourth arguments,
-@var{justify} and @var{mail-flag}, are optional. If
+@var{justify} and @var{citation-regexp}, are optional. If
@var{justify} is non-@code{nil}, the paragraphs are justified as
-well as filled. If @var{mail-flag} is non-@code{nil}, it means the
+well as filled. If @var{citation-regexp} is non-@code{nil}, it means the
function is operating on a mail message and therefore should not fill
-the header lines.
+the header lines. If @var{citation-regexp} is a string, it is used as
+a regular expression; if it matches the beginning of a line, that line
+is treated as a citation marker.
Ordinarily, @code{fill-individual-paragraphs} regards each change in
indentation as starting a new paragraph. If
described above.
@end defopt
-@deffn Command fill-region-as-paragraph start end &optional justify
+@deffn Command fill-region-as-paragraph start end &optional justify nosqueeze squeeze-after
This command considers a region of text as a single paragraph and fills
it. If the region was made up of many paragraphs, the blank lines
between paragraphs are removed. This function justifies as well as
In an interactive call, any prefix argument requests justification.
-@cindex Adaptive Fill mode
-In Adaptive Fill mode, which is enabled by default, calling the function
-@code{fill-region-as-paragraph} on an indented paragraph when there is
-no fill prefix uses the indentation of the second line of the paragraph
-as the fill prefix.
+If @var{nosqueeze} is non-@code{nil}, that means to leave whitespace
+other than line breaks untouched. If @var{squeeze-after} is
+non-@code{nil}, it specifies a position in the region, and means don't
+canonicalize spaces before that position.
+
+In Adaptive Fill mode, this command calls @code{fill-context-prefix} to
+choose a fill prefix by default. @xref{Adaptive Fill}.
@end deffn
-@deffn Command justify-current-line how eop nosqueeze
+@deffn Command justify-current-line &optional how eop nosqueeze
This command inserts spaces between the words of the current line so
that the line ends exactly at @code{fill-column}. It returns
@code{nil}.
the text around point.
@end defun
+@defopt sentence-end-double-space
+If this variable is non-@code{nil}, a period followed by just one space
+does not count as the end of a sentence, and the filling functions
+avoid breaking the line at such a place.
+@end defopt
+
@defvar fill-paragraph-function
This variable provides a way for major modes to override the filling of
paragraphs. If the value is non-@code{nil}, @code{fill-paragraph} calls
The fill prefix follows the left margin whitespace, if any.
@end defopt
-@defvar fill-column
+@defopt fill-column
This buffer-local variable specifies the maximum width of filled lines.
Its value should be an integer, which is a number of columns. All the
filling, justification, and centering commands are affected by this
read, you should set @code{fill-column} to no more than 70. Otherwise
the line will be too long for people to read comfortably, and this can
make the text seem clumsy.
-@end defvar
+@end defopt
@defvar default-fill-column
The value of this variable is the default value for @code{fill-column} in
indentation if that doesn't match the left margin value.
@end deffn
-@defun delete-to-left-margin from to
-This function removes left margin indentation from the text
-between @var{from} and @var{to}. The amount of indentation
-to delete is determined by calling @code{current-left-margin}.
-In no case does this function delete non-whitespace.
+@defun delete-to-left-margin &optional from to
+This function removes left margin indentation from the text between
+@var{from} and @var{to}. The amount of indentation to delete is
+determined by calling @code{current-left-margin}. In no case does this
+function delete non-whitespace. If @var{from} and @var{to} are omitted,
+they default to the whole buffer.
@end defun
@defun indent-to-left-margin
@end defvar
@defvar fill-nobreak-predicate
-@tindex fill-nobreak-predicate
This variable gives major modes a way to specify not to break a line at
certain places. Its value should be a function. This function is
called during filling, with no arguments and with point located at the
non-@code{nil}, then the line won't be broken there.
@end defvar
+@node Adaptive Fill
+@section Adaptive Fill Mode
+@cindex Adaptive Fill mode
+
+ Adaptive Fill mode chooses a fill prefix automatically from the text
+in each paragraph being filled.
+
+@defopt adaptive-fill-mode
+Adaptive Fill mode is enabled when this variable is non-@code{nil}.
+It is @code{t} by default.
+@end defopt
+
+@defun fill-context-prefix from to
+This function implements the heart of Adaptive Fill mode; it chooses a
+fill prefix based on the text between @var{from} and @var{to}. It does
+this by looking at the first two lines of the paragraph, based on the
+variables described below.
+@c The optional argument first-line-regexp is not documented
+@c because it exists for internal purposes and might be eliminated
+@c in the future.
+@end defun
+
+@defopt adaptive-fill-regexp
+This variable holds a regular expression to control Adaptive Fill mode.
+Adaptive Fill mode matches this regular expression against the text
+starting after the left margin whitespace (if any) on a line; the
+characters it matches are that line's candidate for the fill prefix.
+@end defopt
+
+@defopt adaptive-fill-first-line-regexp
+In a one-line paragraph, if the candidate fill prefix matches this
+regular expression, or if it matches @code{comment-start-skip}, then it
+is used---otherwise, spaces amounting to the same width are used
+instead.
+
+However, the fill prefix is never taken from a one-line paragraph
+if it would act as a paragraph starter on subsequent lines.
+@end defopt
+
+@defopt adaptive-fill-function
+You can specify more complex ways of choosing a fill prefix
+automatically by setting this variable to a function. The function is
+called when @code{adaptive-fill-regexp} does not match, with point after
+the left margin of a line, and it should return the appropriate fill
+prefix based on that line. If it returns @code{nil}, that means it sees
+no fill prefix in that line.
+@end defopt
+
@node Auto Filling
@comment node-name, next, previous, up
@section Auto Filling
@defvar auto-fill-function
The value of this variable should be a function (of no arguments) to be
-called after self-inserting a space or a newline. It may be @code{nil},
-in which case nothing special is done in that case.
+called after self-inserting a character from the table
+@code{auto-fill-chars}. It may be @code{nil}, in which case nothing
+special is done in that case.
The value of @code{auto-fill-function} is @code{do-auto-fill} when
Auto-Fill mode is enabled. That is a function whose sole purpose is to
Fill works.
@end defvar
+@defvar auto-fill-chars
+A char table of characters which invoke @code{auto-fill-function} when
+self-inserted---space and newline in most language environments. They
+have an entry @code{t} in the table.
+@end defvar
+
@node Sorting
@section Sorting Text
@cindex sorting text
@end group
@group
(interactive "P\nr")
- (save-restriction
- (narrow-to-region beg end)
- (goto-char (point-min))
- (sort-subr reverse 'forward-line 'end-of-line)))
+ (save-excursion
+ (save-restriction
+ (narrow-to-region beg end)
+ (goto-char (point-min))
+ (sort-subr reverse 'forward-line 'end-of-line))))
@end group
@end example
@example
@group
(sort-subr reverse
- (function
- (lambda () (skip-chars-forward "\n \t\f")))
+ (function
+ (lambda ()
+ (while (and (not (eobp))
+ (looking-at paragraph-separate))
+ (forward-line 1))))
'forward-paragraph)
@end group
@end example
position after @code{sort-subr} returns.
@end defun
+@defopt sort-fold-case
+If this variable is non-@code{nil}, @code{sort-subr} and the other
+buffer sorting functions ignore case when comparing strings.
+@end defopt
+
@deffn Command sort-regexp-fields reverse record-regexp key-regexp start end
This command sorts the region between @var{start} and @var{end}
alphabetically as specified by @var{record-regexp} and @var{key-regexp}.
@var{force}, since there is no way to split them.
The argument @var{force} also has an effect if the line isn't long
-enough to reach column @var{column}; in that case, it says to add
-whitespace at the end of the line to reach that column.
+enough to reach column @var{column}; if it is @code{t}, that means to
+add whitespace at the end of the line to reach that column.
If @var{column} is not an integer, an error is signaled.
@deffn Command reindent-then-newline-and-indent
@comment !!SourceFile simple.el
This command reindents the current line, inserts a newline at point,
-and then reindents the new line (the one following the newline just
+and then indents the new line (the one following the newline just
inserted).
This command does indentation on both lines according to the current
only when text is examined.
* Clickable Text:: Using text properties to make regions of text
do something when you click on them.
+* Fields:: The @code{field} property defines
+ fields within the buffer.
* Not Intervals:: Why text properties do not use
Lisp-visible text intervals.
@end menu
Since text properties are considered part of the contents of the
buffer (or string), and can affect how a buffer looks on the screen, any
-change in buffer text properties mark the buffer as modified. Buffer
+change in buffer text properties marks the buffer as modified. Buffer
text property changes are undoable also (@pxref{Undo}).
@defun put-text-property start end prop value &optional object
@example
(set-text-properties @var{start} @var{end} nil)
@end example
+@end defun
+
+ The easiest way to make a string with text properties
+is with @code{propertize}:
+
+@defun propertize string &rest properties
+@tindex propertize
+This function returns a copy of @var{string} which has the text
+properties @var{properties}. These properties apply to all the
+characters in the string that is returned. Here is an example that
+constructs a string with a @code{face} property and a @code{mouse-face}
+property:
+
+@smallexample
+(propertize "foo" 'face 'italic
+ 'mouse-face 'bold-italic)
+ @result{} #("foo" 0 3 (mouse-face bold-italic face italic))
+@end smallexample
+
+To put different properties on various parts of a string, you can
+construct each part with @code{propertize} and then combine them with
+@code{concat}:
+
+@smallexample
+(concat
+ (propertize "foo" 'face 'italic
+ 'mouse-face 'bold-italic)
+ " and "
+ (propertize "bar" 'face 'italic
+ 'mouse-face 'bold-italic))
+ @result{} #("foo and bar"
+ 0 3 (face italic mouse-face bold-italic)
+ 3 8 nil
+ 8 11 (face italic mouse-face bold-italic))
+@end smallexample
@end defun
See also the function @code{buffer-substring-no-properties}
@end defun
@defun next-char-property-change position &optional limit
-@tindex next-char-property-change
This is like @code{next-property-change} except that it considers
overlay properties as well as text properties. There is no @var{object}
operand because this function operates only on the current buffer. It
@end defun
@defun previous-char-property-change position &optional limit
-@tindex previous-char-property-change
This is like @code{next-char-property-change}, but scans back from
@var{position} instead of forward.
@end defun
@cindex face codes of text
@kindex face @r{(text property)}
You can use the property @code{face} to control the font and color of
-text. Its value is a face name or a list of face names. @xref{Faces},
-for more information.
+text. @xref{Faces}, for more information.
+
+In the simplest case, the value is a face name. It can also be a list;
+then each element can be any of these possibilities;
+
+@itemize @bullet
+@item
+A face name (a symbol or string).
+
+@item
+Starting in Emacs 21, a property list of face attributes. This has the
+form (@var{keyword} @var{value} @dots{}), where each @var{keyword} is a
+face attribute name and @var{value} is a meaningful value for that
+attribute. With this feature, you do not need to create a face each
+time you want to specify a particular attribute for certain text.
+@xref{Face Attributes}.
+
+@item
+A cons cell of the form @code{(foreground-color . @var{color-name})} or
+@code{(background-color . @var{color-name})}. These elements specify
+just the foreground color or just the background color.
-If the property value is a list, elements may also have the form
-@code{(foreground-color . @var{color-name})} or @code{(background-color
-. @var{color-name})}. These elements specify just the foreground color
-or just the background color; therefore, there is no need to create a
-face for each color that you want to use.
+@code{(foreground-color . @var{color-name})} is equivalent to
+@code{(:foreground @var{color-name})}, and likewise for the background.
+@end itemize
@xref{Font Lock Mode}, for information on how to update @code{face}
properties automatically based on the contents of the text.
that all text between the character and where the mouse is have the same
@code{mouse-face} property value.
+@item fontified
+@kindex fontified @r{(text property)}
+This property, if non-@code{nil}, says that text in the buffer has
+had faces assigned automatically by a feature such as Font-Lock mode.
+@xref{Auto Faces}.
+
+@item display
+@kindex display @r{(text property)}
+This property activates various features that change the
+way text is displayed. For example, it can make text appear taller
+or shorter, higher or lower, wider or narrow, or replaced with an image.
+@xref{Display Property}.
+
+@item help-echo
+@kindex help-echo @r{(text property)}
+@anchor{Text help-echo}
+If text has a string as its @code{help-echo} property, then when you
+move the mouse onto that text, Emacs displays that string in the echo
+area, or in the tooltip window.
+
+If the value of the @code{help-echo} property is a function, that
+function is called with three arguments, @var{window}, @var{object} and
+@var{position} and should return a help string or @var{nil} for
+none. The first argument, @var{window} is the window in which
+the help was found. The second, @var{object}, is the buffer, overlay or
+string which had the @code{help-echo} property. The @var{position}
+argument is as follows:
+
+@itemize @bullet{}
+@item
+If @var{object} is a buffer, @var{pos} is the position in the buffer
+where the @code{help-echo} text property was found.
+@item
+If @var{object} is an overlay, that overlay has a @code{help-echo}
+property, and @var{pos} is the position in the overlay's buffer under
+the mouse.
+@item
+If @var{object} is a string (an overlay string or a string displayed
+with the @code{display} property), @var{pos} is the position in that
+string under the mouse.
+@end itemize
+
+If the value of the @code{help-echo} property is neither a function nor
+a string, it is evaluated to obtain a help string.
+
+You can alter the way help text is displayed by setting the variable
+@code{show-help-function} (@pxref{Help display}).
+
+This feature is used in the mode line and for other active text. It is
+available starting in Emacs 21.
+
@item local-map
@cindex keymap of character
@kindex local-map @r{(text property)}
@cindex read-only character
@kindex read-only @r{(text property)}
If a character has the property @code{read-only}, then modifying that
-character is not allowed. Any command that would do so gets an error.
+character is not allowed. Any command that would do so gets an error,
+@code{text-read-only}.
Insertion next to a read-only character is an error if inserting
ordinary text there would inherit the @code{read-only} property due to
When the variable @code{inhibit-point-motion-hooks} is non-@code{nil},
the @code{intangible} property is ignored.
+@item field
+@kindex field @r{(text property)}
+Consecutive characters with the same @code{field} property constitute a
+@dfn{field}. Some motion functions including @code{forward-word} and
+@code{beginning-of-line} stop moving at a field boundary.
+@xref{Fields}.
+
@item modification-hooks
@cindex change hooks for a character
@cindex hooks for changing a character
@code{let}.
@end defvar
+@defvar show-help-function
+@tindex show-help-function
+@anchor{Help display} If this variable is non-@code{nil}, it specifies a
+function called to display help strings. These may be @code{help-echo}
+properties, menu help strings (@pxref{Simple Menu Items},
+@pxref{Extended Menu Items}), or tool bar help strings (@pxref{Tool
+Bar}). The specified function is called with one argument, the help
+string to display. Tooltip mode (@pxref{(emacs)Tooltips}) provides an
+example.
+@end defvar
+
@node Format Properties
@subsection Formatted Text Properties
using these primitives.
When you do insertion with inheritance, @emph{which} properties are
-inherited depends on two specific properties: @code{front-sticky} and
-@code{rear-nonsticky}.
-
- Insertion after a character inherits those of its properties that are
+inherited, and from where, depends on which properties are @dfn{sticky}.
+Insertion after a character inherits those of its properties that are
@dfn{rear-sticky}. Insertion before a character inherits those of its
-properties that are @dfn{front-sticky}. By default, a text property is
-rear-sticky but not front-sticky. Thus, the default is to inherit all
-the properties of the preceding character, and nothing from the
-following character. You can request different behavior by specifying
-the stickiness of certain properties.
+properties that are @dfn{front-sticky}. When both sides offer different
+sticky values for the same property, the previous character's value
+takes precedence.
+
+ By default, a text property is rear-sticky but not front-sticky; thus,
+the default is to inherit all the properties of the preceding character,
+and nothing from the following character.
+
+ You can control the stickiness of various text properties with two
+specific text properties, @code{front-sticky} and @code{rear-nonsticky},
+and with the variable @code{text-property-default-nonsticky}. You can
+use the variable to specify a different default for a given property.
+You can use those two text properties to make any specific properties
+sticky or nonsticky in any particular part of the text.
If a character's @code{front-sticky} property is @code{t}, then all
its properties are front-sticky. If the @code{front-sticky} property is
then insertion before the character can inherit its @code{face} property
and its @code{read-only} property, but no others.
- The @code{rear-nonsticky} works the opposite way. Every property is
-rear-sticky by default, so the @code{rear-nonsticky} property says which
-properties are @emph{not} rear-sticky. If a character's
-@code{rear-nonsticky} property is @code{t}, then none of its properties
-are rear-sticky. If the @code{rear-nonsticky} property is a list,
-properties are rear-sticky @emph{unless} their names are in the list.
+ The @code{rear-nonsticky} property works the opposite way. Most
+properties are rear-sticky by default, so the @code{rear-nonsticky}
+property says which properties are @emph{not} rear-sticky. If a
+character's @code{rear-nonsticky} property is @code{t}, then none of its
+properties are rear-sticky. If the @code{rear-nonsticky} property is a
+list, properties are rear-sticky @emph{unless} their names are in the
+list.
- When you insert text with inheritance, it inherits all the rear-sticky
-properties of the preceding character, and all the front-sticky
-properties of the following character. The previous character's
-properties take precedence when both sides offer different sticky values
-for the same property.
+@defvar text-property-default-nonsticky
+@tindex text-property-default-nonsticky
+This variable holds an alist which defines the default rear-stickiness
+of various text properties. Each element has the form
+@code{(@var{property} . @var{nonstickiness})}, and it defines the
+stickiness of a particular text property, @var{property}.
+
+If @var{nonstickiness} is non-@code{nil}, this means that the property
+@var{property} is rear-nonsticky by default. Since all properties are
+front-nonsticky by default, this makes @var{property} nonsticky in both
+directions by default.
+
+The text properties @code{front-sticky} and @code{rear-nonsticky}, when
+used, take precedence over the default @var{nonstickiness} specifed in
+@code{text-property-default-nonsticky}.
+@end defvar
Here are the functions that insert text with inheritance of properties:
file to visit, based on the position found in the event.
Instead of defining a mouse command for the major mode, you can define
-a key binding for the clickable text itself, using the @code{local-map}
+a key binding for the clickable text itself, using the @code{keymap}
text property:
@example
(let ((map (make-sparse-keymap)))
- (define-key-binding map [mouse-2] 'operate-this-button)
+ (define-key map [mouse-2] 'operate-this-button)
(put-text-property (point)
(save-excursion
(dired-move-to-end-of-filename)
(point))
- 'local-map map))
+ 'keymap map))
@end example
@noindent
global definition) remains available for the rest of the text in the
buffer.
+@node Fields
+@subsection Defining and Using Fields
+@cindex fields
+
+ A field is a range of consecutive characters in the buffer that are
+identified by having the same value (comparing with @code{eq}) of the
+@code{field} property (either a text-property or an overlay property).
+This section describes special functions that are available for
+operating on fields.
+
+ You specify a field with a buffer position, @var{pos}. We think of
+each field as containing a range of buffer positions, so the position
+you specify stands for the field containing that position.
+
+ When the characters before and after @var{pos} are part of the same
+field, there is no doubt which field contains @var{pos}: the one those
+characters both belong to. When @var{pos} is at a boundary between
+fields, which field it belongs to depends on the stickiness of the
+@code{field} properties of the two surrounding characters (@pxref{Sticky
+Properties}). The field whose property would be inherited by text
+inserted at @var{pos} is the field that contains @var{pos}.
+
+ There is an anomalous case where newly inserted text at @var{pos}
+would not inherit the @code{field} property from either side. This
+happens if the previous character's @code{field} property is not
+rear-sticky, and the following character's @code{field} property is not
+front-sticky. In this case, @var{pos} belongs to neither the preceding
+field nor the following field; the field functions treat it as belonging
+to an empty field whose beginning and end are both at @var{pos}.
+
+ In all of these functions, if @var{pos} is omitted or @code{nil}, the
+value of point is used by default.
+
+@defun field-beginning &optional pos escape-from-edge
+@tindex field-beginning
+This function returns the beginning of the field specified by @var{pos}.
+
+If @var{pos} is at the beginning of its field, and
+@var{escape-from-edge} is non-@code{nil}, then the return value is
+always the beginning of the preceding field that @emph{ends} at @var{pos},
+regardless of the stickiness of the @code{field} properties around
+@var{pos}.
+@end defun
+
+@defun field-end &optional pos escape-from-edge
+@tindex field-end
+This function returns the end of the field specified by @var{pos}.
+
+If @var{pos} is at the end of its field, and @var{escape-from-edge} is
+non-@code{nil}, then the return value is always the end of the following
+field that @emph{begins} at @var{pos}, regardless of the stickiness of
+the @code{field} properties around @var{pos}.
+@end defun
+
+@defun field-string &optional pos
+@tindex field-string
+This function returns the contents of the field specified by @var{pos},
+as a string.
+@end defun
+
+@defun field-string-no-properties &optional pos
+@tindex field-string-no-properties
+This function returns the contents of the field specified by @var{pos},
+as a string, discarding text properties.
+@end defun
+
+@defun delete-field &optional pos
+@tindex delete-field
+This function deletes the text of the field specified by @var{pos}.
+@end defun
+
+@defun constrain-to-field new-pos old-pos &optional escape-from-edge only-in-line inhibit-capture-property
+@tindex constrain-to-field
+This function ``constrains'' @var{new-pos} to the field that
+@var{old-pos} belongs to---in other words, it returns the position
+closest to @var{new-pos} that is in the same field as @var{old-pos}.
+
+If @var{new-pos} is @code{nil}, then @code{constrain-to-field} uses
+the value of point instead, and moves point to the resulting position.
+
+If @var{old-pos} is at the boundary of two fields, then the acceptable
+positions for @var{new-pos} depend on the value of the optional argument
+@var{escape-from-edge}. If @var{escape-from-edge} is @code{nil}, then
+@var{new-pos} is constrained to the field that has the same @code{field}
+property (either a text-property or an overlay property) that new
+characters inserted at @var{old-pos} would get. (This depends on the
+stickiness of the @code{field} property for the characters before and
+after @var{old-pos}.) If @var{escape-from-edge} is non-@code{nil},
+@var{new-pos} is constrained to the union of the two adjacent fields.
+Additionally, if two fields are separated by another field with the
+special value @code{boundary}, then any point within this special field
+is also considered to be ``on the boundary.''
+
+If the optional argument @var{only-in-line} is non-@code{nil}, and
+constraining @var{new-pos} in the usual way would move it to a different
+line, @var{new-pos} is returned unconstrained. This used in commands
+that move by line, such as @code{next-line} and
+@code{beginning-of-line}, so that they respect field boundaries only in
+the case where they can still move to the right line.
+
+If the optional argument @var{inhibit-capture-property} is
+non-@code{nil}, and @var{old-pos} has a non-@code{nil} property of that
+name, then any field boundaries are ignored.
+
+You can cause @code{constrain-to-field} to ignore all field boundaries
+(and so never constrain anything) by binding the variable
+@code{inhibit-field-text-motion} to a non-nil value.
+@end defun
+
@node Not Intervals
@subsection Why Text Properties are not Intervals
@cindex intervals
with the character @var{new-char} in the region of the current buffer
defined by @var{start} and @var{end}.
-@cindex Outline mode
@cindex undo avoidance
If @var{noundo} is non-@code{nil}, then @code{subst-char-in-region} does
not record the change for undo and does not mark the buffer as modified.
-This feature is used for controlling selective display (@pxref{Selective
-Display}).
+This was useful for controlling the old selective display feature
+(@pxref{Selective Display}).
@code{subst-char-in-region} does not move point and returns
@code{nil}.
A register is a sort of variable used in Emacs editing that can hold a
variety of different kinds of values. Each register is named by a
-single character. All ASCII characters and their meta variants (but
-with the exception of @kbd{C-g}) can be used to name registers. Thus,
-there are 255 possible registers. A register is designated in Emacs
-Lisp by the character that is its name.
+single character. All @sc{ascii} characters and their meta variants
+(but with the exception of @kbd{C-g}) can be used to name registers.
+Thus, there are 255 possible registers. A register is designated in
+Emacs Lisp by the character that is its name.
@defvar register-alist
This variable is an alist of elements of the form @code{(@var{name} .
all markers unrelocated.
@end defun
+@node Base 64
+@section Base 64 Encoding
+@cindex base 64 encoding
+
+ Base 64 code is used in email to encode a sequence of 8-bit bytes as a
+longer sequence of @sc{ascii} graphic characters. This section
+describes the functions for converting to and from this code.
+
+@defun base64-encode-region beg end &optional no-line-break
+@tindex base64-encode-region
+This function converts the region from @var{beg} to @var{end}
+into base 64 code. It returns the length of the encoded text.
+
+Normally, this function inserts newline characters into the encoded
+text, to avoid overlong lines. However, if the optional argument
+@var{no-line-break} is non-@code{nil}, these newlines are not added, so
+the output is just one long line.
+@end defun
+
+@defun base64-encode-string string &optional no-line-break
+@tindex base64-encode-string
+This function converts the string @var{string} into base 64 code. It
+returns a string containing the encoded text.
+
+Normally, this function inserts newline characters into the encoded
+text, to avoid overlong lines. However, if the optional argument
+@var{no-line-break} is non-@code{nil}, these newlines are not added, so
+the result string is just one long line.
+@end defun
+
+@defun base64-decode-region beg end
+@tindex base64-decode-region
+This function converts the region from @var{beg} to @var{end} from base
+64 code into the corresponding decoded text. It returns the length of
+the decoded text.
+
+The decoding functions ignore newline characters in the encoded text.
+@end defun
+
+@defun base64-decode-string string
+@tindex base64-decode-string
+This function converts the string @var{string} from base 64 code into
+the corresponding decoded text. It returns a string containing the
+decoded text.
+
+The decoding functions ignore newline characters in the encoded text.
+@end defun
+
@node Change Hooks
@section Change Hooks
@cindex change hooks
before the change. All three arguments are integers. The buffer that's
about to change is always the current buffer.
-The length of the old text the difference between the buffer positions
+The length of the old text is the difference between the buffer positions
before and after that text as it was before the change. As for the
changed text, its length is simply the difference between the first two
arguments.
@end defvar
@defmac combine-after-change-calls body...
-@tindex combine-after-change-calls
The macro executes @var{body} normally, but arranges to call the
after-change functions just once for a series of several changes---if
that seems safe.
made within the @code{combine-after-change-calls} body.
@strong{Warning:} You must not alter the values of
-@code{after-change-functions} and @code{after-change-function} within
+@code{after-change-functions} within
the body of a @code{combine-after-change-calls} form.
@strong{Note:} If the changes you combine occur in widely scattered
functions.
@end defmac
-@defvar before-change-function
-This obsolete variable holds one function to call before any buffer
-modification (or @code{nil} for no function). It is called just like
-the functions in @code{before-change-functions}.
-@end defvar
-
-@defvar after-change-function
-This obsolete variable holds one function to call after any buffer modification
-(or @code{nil} for no function). It is called just like the functions in
-@code{after-change-functions}.
-@end defvar
-
-The four variables above are temporarily bound to @code{nil} during the
+The two variables above are temporarily bound to @code{nil} during the
time that any of these functions is running. This means that if one of
these functions changes the buffer, that change won't run these
functions. If you do want a hook function to make changes that run
This variable is a normal hook that is run whenever a buffer is changed
that was previously in the unmodified state.
@end defvar
+
+@defvar inhibit-modification-hooks
+@tindex inhibit-modification-hooks
+If this variable is non-@code{nil}, all of the change hooks are
+disabled; none of them run. This affects all the hook variables
+described above in this section, as well as the hooks attached to
+certain special text properties (@pxref{Special Properties}) and overlay
+properties (@pxref{Overlay Properties}).
+
+This variable is available starting in Emacs 21.
+@end defvar
HCoop / bpt / emacs.git / blobdiff