@c -*-texinfo-*-
@c This is part of the GNU Emacs Lisp Reference Manual.
-@c Copyright (C) 1999 Free Software Foundation, Inc.
+@c Copyright (C) 1999, 2002, 2003, 2004, 2005,
+@c 2006 Free Software Foundation, Inc.
@c See the file elisp.texi for copying conditions.
@c This node must have no pointers.
-@c @node Antinews, GNU Free Documentation License, System Interface, Top
-@appendix Emacs 20 Antinews
+@node Antinews, GNU Free Documentation License, System Interface, Top
+@appendix Emacs 21 Antinews
For those users who live backwards in time, here is information about
-downgrading to Emacs version 20.4. We hope you will enjoy the greater
-simplicity that results from the absence of many Emacs 21 features. In
-the following section, we carry this information back to Emacs
-20.3, for which the previous printed edition of this manual was made.
+downgrading to Emacs version 21.4. We hope you will enjoy the greater
+simplicity that results from the absence of many Emacs @value{EMACSVER}
+features.
-@section Old Lisp Features in Emacs 20
+@section Old Lisp Features in Emacs 21
@itemize @bullet
@item
-The @code{push} and @code{pop} macros are not defined.
-Neither are @code{dolist} and @code{dotimes}.
+Many unnecessary features of redisplay have been eliminated. (The
+earlier major release, Emacs 20, will have a completely rewritten
+redisplay engine, which will be even simpler.)
+@itemize @minus
@item
-You can't display images in buffers. (Emacs is meant for editing text.)
-With no images, there are no display margins, and no tool bars.
+The function @code{force-window-update} has been removed. It
+shouldn't be needed, since changes in window contents are detected
+automatically. In case they aren't, call @code{redraw-display} to
+redraw everything.
@item
-The @code{display} text property has no special meaning; you can use it
-freely in Lisp programs, with no effects except what you implement for
-yourself. With no images, who needs the @code{display} text property?
+Point no longer moves out from underneath invisible text at the end of
+each command. This allows the user to detect invisible text by moving
+the cursor around---if the cursor gets stuck, there is something
+invisible in the way. If you really want cursor motion to ignore the
+text, try marking it as intangible.
@item
-The @code{field} text property has no special meaning; buffers are no
-longer subdivided into fields. (The division of information into
-fields is always rather arbitrary.)
+Support for image maps and image slices has been removed. Emacs was
+always meant for editing text, anyway.
@item
-Faces have fewer attributes. The attributes @code{:family},
-@code{:height}, @code{:width}, @code{:weight}, and @code{:slant},
-have been replaced with a font name, a ``bold'' flag, and an
-``italic'' flag.
+The mode line now accepts all text properties, as well as
+@code{:propertize} and @code{:eval} forms, regardless of the
+@code{risky-local-variable} property.
-The attributes @code{:overline}, @code{:strike-through} and @code{:box}
-have been eliminated too. Underlining now always has the same color as
-the text---using any other color would be bad taste.
+@item
+The @code{line-height} and @code{line-spacing} properties no longer
+have any meaning for newline characters. Such properties wouldn't
+make sense, since newlines are not really characters; they just tell
+you where to break a line.
-With fewer font attributes, there are no functions
-@code{set-face-attribute} and @code{face-attribute}. Instead, you
-access these attributes using functions such as @code{face-font}, and
-set them with functions such as @code{set-face-font}. (These functions
-were available in Emacs 21, but are not as useful there.)
+@item
+Considerable simplifications have been made to the display
+specification @code{(space . @var{props})}, which is used for
+displaying a space of specified width and height. Pixel-based
+specifications and Lisp expressions are no longer accepted.
@item
-The standard faces @code{scroll-bar}, @code{menu}, @code{border},
-@code{cursor}, and @code{mouse} have been eliminated. They are rather
-strange, as faces, and therefore shouldn't really exist. You can use
-@code{set-border-color}, @code{set-cursor-color} and
-@code{set-mouse-color} to specify the colors for the frame border, the
-text cursor, and the mouse cursor. To specify menu colors, use X
-resources.
+Many features associated with the fringe areas have been removed, to
+encourage people to concentrate on the main editing area (the fringe
+will be completely removed in Emacs 20.) Arbitrary bitmaps can no
+longer be displayed in the fringe; an overlay arrow can still be
+displayed, but there can only be one overlay arrow at a time (any more
+would be confusing.) The fringe widths cannot be adjusted, and
+individual windows cannot have their own fringe settings. A mouse
+click on the fringe no longer generates a special event.
@item
-Colors and other face attributes are no longer supported on character
-terminals, so you no longer have to worry about terminals making faces
-at you.
+Individual windows cannot have their own scroll-bar settings.
@item
-Emacs will respect your peace and quiet, aside from occasional beeps,
-because there are no facilities for playing sounds.
+You can no longer use @samp{default} in a @code{defface} to specify
+defaults for subsequent faces.
@item
-Emacs 20 provides a complex and badly designed method for handling
-character composition for languages such as Thai that display several
-letters as a single combined image. We are too ashamed of it to tell
-you any more than that.
+The function @code{display-supports-face-attributes-p} has been
+removed. In @code{defface} specifications, the @code{supports}
+predicate is no longer supported.
@item
-@code{delete-and-extract-region} has been deleted; instead, use
-@code{buffer-substring} to extract the text, then use
-@code{delete-region} to delete it.
+@code{face-attribute-relative-p} and @code{merge-face-attribute} have
+been removed.
@item
-Regular expressions do not support the POSIX character classes
-such as @samp{[:alpha:]}. All characters are created equal.
+The priority of faces in a list supplied by the @code{:inherit} face
+attribute has been reversed. We like to make changes like this once
+in a while, to keep Emacs Lisp programmers on their toes.
@item
-Hash tables have been eliminated; use alists instead.
+The @code{min-colors} face attribute, used for tailoring faces to
+limited-color displays, does not exist. If in doubt, use colors like
+``white'' and ``black'', which ought to be defined everywhere.
@item
-The Lisp printer does not detect and report circular structure. That is
-ok, because the Lisp reader cannot recreate circular structure anyway.
-However, there is a library @samp{cust-print.el} which can report
-circular structure.
+The @code{tty-color-mode} frame parameter does not exist. You should
+just trust the terminal capabilities database.
+@end itemize
@item
-Emacs provides its own implementation of scroll bars, instead
-of using those of the X toolkit. They always use the frame foreground
-and background colors, so you cannot specify different colors for
-the scroll bars.
+Several simplifications have been made to mouse support:
+@itemize @minus
@item
-For simplicity, all @sc{ascii} characters now have the same height and width.
-(Certain characters, such as Chinese characters, always have twice
-the standard width.) All characters are created equal.
+Clicking @kbd{mouse-1} won't follow links, as that is alien to the
+spirit of Emacs. Therefore, the @code{follow-link} property doesn't
+has any special meaning, and the function @code{mouse-on-link-p} has
+been removed.
@item
-You can now resize any Emacs window, and size changes in one window can
-propagate to all others. Windows can no longer use
-@code{window-size-fixed} to get special privileges.
+The variable @code{void-text-area-pointer} has been removed, so the
+mouse pointer shape remains unchanged when moving between valid text
+areas and void text areas. The @code{pointer} image and text
+properties are no longer supported.
@item
-The function @code{intern-soft} no longer accepts a symbol as argument.
+Mouse events will no longer specify the timestamp, the object clicked,
+equivalent buffer positions (for marginal or fringe areas), glyph
+coordinates, or relative pixel coordinates.
+@end itemize
@item
-The function @code{bitmap-spec-p} has been renamed to
-@code{pixmap-spec-p} to encourage users to practice Emacs' help system
-while trying to find it.
+Simplifications have also been made to the way Emacs handles keymaps
+and key sequences:
+@itemize @minus
@item
-Tooltips operate using ordinary Emacs frames.
+The @code{kbd} macro has been removed. It isn't that difficult to
+write key sequences using the string and vector representations, and
+we want to encourage users to learn.
@item
-Areas of the mode line are not mouse-sensitive; however, some mouse
-commands are available for the mode line as a whole.
+Emacs no longer supports key remapping. You can do pretty much the
+same thing with @code{substitute-key-definition}, or by advising the
+relevant command.
@item
-Windows cannot have header lines. Conversely, there is no way to turn
-off the mode line of a window unless it is a minibuffer.
+The @code{keymap} text and overlay property is now overridden by minor
+mode keymaps, and will not work at the ends of text properties and
+overlays.
@item
-Plain dashes are the only separators you can use in a menu.
+The functions @code{map-keymap}, @code{keymap-prompt}, and
+@code{current-active-maps} have been removed.
+@end itemize
@item
-Vertical fractional scrolling does not exist.
+Process support has been pared down to a functional minimum. The
+functions @code{call-process-shell-command} and @code{process-file}
+have been deleted. Processes no longer maintain property lists, and
+they won't ask any questions when the user tries to exit Emacs (which
+would simply be rude.) The function @code{signal-process} won't
+accept a process object, only the process id; determining the process
+id from a process object is left as an exercise to the programmer.
@item
-The functions @code{format} and @code{message} ignore and discard text
-properties.
+Networking has also been simplified: @code{make-network-process} and
+its various associated function have all been replaced with a single
+easy-to-use function, @code{open-network-stream}, which can't use UDP,
+can't act as a server, and can't set up non-blocking connections.
+Also, deleting a network process with @code{delete-process} won't call
+the sentinel.
@item
-The function @code{propertize} does not exist;
-you can get the job done using @code{set-text-properties}.
+Many programming shortcuts have been deleted, to provide you with the
+enjoyment of ``rolling your own''. The macros @code{while-no-input},
+@code{with-local-quit}, and @code{with-selected-window}, along with
+@code{dynamic-completion-table} and @code{lazy-completion-table} no
+longer exist. Also, there are no built-in progress reporters;
+with Emacs, you can take progress for granted.
@item
-Colors are supported only on window systems, not on text-only terminals.
-So the support functions for colors on text-only terminals are
-not needed, and have been eliminated.
+Variable aliases are no longer supported. Aliases are for functions,
+not for variables.
@item
-The functions @code{color-values}, @code{color-defined-p} and
-@code{defined-colors} have been renamed to @code{x-color-values},
-@code{x-color-defined-p} and @code{x-defined-colors}.
+The variables @code{most-positive-fixnum} and
+@code{most-negative-fixnum} do not exist. On 32 bit machines, the
+most positive integer is probably 134217727, and the most negative
+integer is probably -134217728.
@item
-Windows cannot be made fixed-width or fixed-height;
-Emacs will adjust the size of all windows when it needs to.
+The functions @code{eql} and @code{macroexpand-all} are no longer
+available. However, you can find similar functions in the @code{cl}
+package.
@item
-The string used as the value of the @code{before-string} or
-@code{after-string} property must contain only characters that display
-as a single column---control characters, including tabs and newlines,
-will give strange results.
+The list returned by @code{split-string} won't include null substrings
+for separators at the beginning or end of a string. If you want to
+check for such separators, do it separately.
@item
-The minibuffer prompt does not actually appear in content of the
-minibuffer; it is displayed specially in the minibuffer window.
+The function @code{assoc-string} has been removed. Use
+@code{assoc-ignore-case} or @code{assoc-ignore-representation} (which
+are no longer obsolete.)
@item
-The ``exclusive open'' feature of @code{write-region}
-has been eliminated; any non-@code{nil} value for the seventh
-argument now means to ask the user for confirmation.
+The escape sequence @samp{\s} is always interpreted as a super
+modifier, never a space.
@item
-The function @code{buffer-size} always reports on the
-current buffer.
+The variable @code{buffer-save-without-query} has been removed, to
+prevent Emacs from sneakily saving buffers. Also, the hook
+@code{before-save-hook} has been removed, so if you want something to
+be done before saving, advise or redefine @code{basic-save-buffer}.
@item
-The function @code{assoc-delete-all} has itself been deleted.
-So there!
+The variable @code{buffer-auto-save-file-format} has been renamed to
+@code{auto-save-file-format}, and is no longer a permanent local.
@item
-The keyword @code{:set-after} no longer does anything in
-@code{defcustom}.
+The function @code{visited-file-modtime} now returns a cons, instead
+of a list of two integers. The primitive @code{set-file-times} has
+been eliminated.
@item
-The variable @code{small-temporary-file-directory} has no special
-meaning. There's only one variable for specifying which directory to
-use for temporary files, @code{temporary-file-directory}, but not all
-Emacs features use it anyway. Some use the @code{TMP} environment
-variable, and some use the @code{TMPDIR} environment variable.
+The function @code{file-remote-p} is no longer available.
@item
-If the second argument of @code{save-some-buffers}, @var{pred}, is not
-@code{nil}, then the precise value no longer matters. Any
-non-@code{nil} value means the same as @code{t}: offer to save each
-non-file buffer that has a non-@code{nil} value for
-@code{buffer-offer-save}.
+When determining the filename extension, a leading dot in a filename
+is no longer ignored. Thus, @file{.emacs} is considered to have
+extension @file{emacs}, rather than being extensionless.
@item
-The variable @code{inhibit-modification-hooks}
-has no special meaning.
+Emacs looks for special file handlers in a more efficient manner: it
+will choose the first matching handler in
+@code{file-name-handler-alist}, rather than trying to figure out which
+provides the closest match.
@item
-The hook @code{fontification-functions} has been eliminated,
-but there are other hooks, such as @code{window-scroll-functions},
-that you can use to do a similar job.
+The @code{predicate} argument for @code{read-file-name} has been
+removed, and so have the variables @code{read-file-name-function} and
+@code{read-file-name-completion-ignore-case}. The function
+@code{read-directory-name} has also been removed.
@item
-The variable @code{redisplay-dont-pause}
-has no special meaning.
+The functions @code{all-completions} and @code{try-completion} will no
+longer accept lists of strings or hash tables (it will still accept
+alists, obarrays, and functions.) In addition, the function
+@code{test-completion} is no longer available.
@item
-The hook @code{calendar-move-hook} has been deleted.
+The @samp{G} interactive code character is no longer supported.
+Use @samp{F} instead.
@item
-The function @code{move-to-column} treats any non-@code{nil}
-second argument just like @code{t}.
-@end itemize
+Arbitrary Lisp functions can no longer be recorded into
+@code{buffer-undo-list}. As a consequence, @code{yank-undo-function}
+is obsolete, and has been removed.
-@section Old Lisp Features in Emacs 20.3
+@item
+Emacs will never complain about commands that accumulate too much undo
+information, so you no longer have to worry about binding
+@code{buffer-undo-list} to @code{t} for such commands (though you may
+want to do that anyway, to avoid taking up unnecessary memory space.)
-Here are the most important of the features that you will learn
-to do without in Emacs 20.3:
+@item
+Atomic change groups are no longer supported.
-Here are changes in the Lisp language itself:
+@item
+The list returned by @code{(match-data t)} no longer records the
+buffer as a final element.
-@itemize @bullet
@item
-The functions @code{line-beginning-position} and @code{line-end-position}
-have been eliminated.
+The function @code{looking-back} has been removed, so we no longer
+have the benefit of hindsight.
@item
-The functions @code{directory-files-and-attributes},
-@code{file-attributes-lessp}, and @code{file-expand-wildcards}, have
-been eliminated.
+The variable @code{search-spaces-regexp} does not exist. Spaces
+always stand for themselves in regular expression searches.
@item
-The functions @code{decode-coding-region} and @code{encode-coding-region}
-leave text properties untouched, in case that is useful. (It rarely makes
-any sense, though.)
+The functions @code{skip-chars-forward} and @code{skip-chars-backward}
+no longer accepts character classes such as @samp{[:alpha:]}. All
+characters are created equal.
@item
-The functions @code{position-bytes} and @code{byte-to-position} have
-been eliminated.
+The @code{yank-handler} text property no longer has any meaning.
+Also, @code{yank-excluded-properties}, @code{insert-for-yank}, and
+@code{insert-buffer-substring-as-yank} have all been removed.
+
+@item
+The variable @code{char-property-alias-alist} has been deleted.
+Aliases are for functions, not for properties.
+
+@item
+The function @code{get-char-property-and-overlay} has been deleted.
+If you want the properties at a point, find the text properties at the
+point; then, find the overlays at the point, and find the properties
+on those overlays.
+
+@item
+Font Lock mode only manages @code{face} properties; you can't use
+font-lock keywords to specify arbitrary text properties for it to
+manage. After all, it is called Font Lock mode, not Arbitrary
+Properties Lock mode.
+
+@item
+The arguments to @code{remove-overlays} are no longer optional.
+
+@item
+In @code{replace-match}, the replacement text now inherits properties
+from the surrounding text.
+
+@item
+@code{mode-line-format} no longer supports the @code{:propertize},
+@code{%i}, and @code{%I} constructs. The function
+@code{format-mode-line} has been removed.
+
+@item
+The functions @code{window-inside-edges} and @code{window-body-height}
+have been removed. You should do the relevant calculations yourself,
+starting with @code{window-width} and @code{window-height}.
@item
-Temporary buffers made with @code{with-output-to-temp-buffer} are now
-modifiable by default, and use Fundamental mode rather than Help mode.
+The functions @code{window-pixel-edges} and
+@code{window-inside-pixel-edges} have been removed. We prefer to
+think in terms of lines and columns, not pixel coordinates. (Sometime
+in the distant past, we will do away with graphical terminals
+entirely, in favor of text terminals.) For similar reasons, the
+functions @code{posn-at-point}, @code{posn-at-x-y}, and
+@code{pos-visible-in-window-p} have been removed.
@item
-The functions @code{sref} interprets its @var{index} argument as a
-number of bytes, not a number of characters. And the function
-@code{char-bytes} actually tries to report on the number of bytes that a
-character occupies.
+The macro @code{save-selected-window} only saves the selected window
+of the selected frame, so don't try selecting windows in other frames.
@item
-The function @code{process-running-child-p} has been eliminated.
+The function @code{minibufferp} is no longer available.
@item
-The function @code{interrupt-process} and similar functions no longer do
-anything special when the second argument is @code{lambda}.
+The function @code{modify-all-frames-parameters} has been removed (we
+always suspected the name was ungrammatical, anyway.)
@item
-The function @code{define-prefix-command} accepts only two arguments.
+The @code{line-spacing} variable no longer accepts float values.
@item
-The meaning of the second argument to @code{read-char},
-@code{read-event}, and @code{read-char-exclusive} has been reversed:
-they use the current input method if the argument is if @code{nil}.
+The function @code{tool-bar-local-item-from-menu} has been deleted.
+If you need to make an entry in the tool bar, you can still use
+@code{tool-bar-add-item-from-menu}, but that modifies the binding in
+the source keymap instead of copying it into the local keymap.
@item
-The function @code{with-temp-message} has been eliminated.
+When determining the major mode, the file name takes precedence over
+the interpreter magic line. The variable @code{magic-mode-alist},
+which associates certain buffer beginnings with major modes, has been
+eliminated.
@item
-The function @code{clear-this-command-keys} has been eliminated.
+The hook @code{after-change-major-mode-hook} is not defined, and
+neither are @code{run-mode-hooks} and @code{delay-mode-hooks}.
@item
-The functions @code{gap-position} and @code{gap-size} have been eliminated.
+The variable @code{minor-mode-list} has been removed.
@item
-In @code{modify-face}, an argument of @code{(nil)} has no special
+@code{define-derived-mode} will copy abbrevs from the parent mode's
+abbrev table, instead of creating a new, empty abbrev table.
+
+@item
+There are no ``system'' abbrevs. When the user saves into the abbrevs
+file, all abbrevs are saved.
+
+@item
+The Warnings facility has been removed. Just use @code{error}.
+
+@item
+Several hook variables have been renamed to flout the Emacs naming
+conventions. We feel that consistency is boring, and having
+non-standard hook names encourages users to check the documentation
+before using a hook. For instance, the normal hook
+@code{find-file-hook} has been renamed to @code{find-file-hooks}, and
+the abnormal hook @code{delete-frame-functions} has been renamed to
+@code{delete-frame-hook}.
+
+@item
+The function @code{symbol-file} does not exist. If you want to know
+which file defined a function or variable, try grepping for it.
+
+@item
+The variable @code{load-history} records function definitions just
+like variable definitions, instead of indicating which functions were
+previously autoloaded.
+
+@item
+There is a new variable, @code{recursive-load-depth-limit}, which
+specifies how many times files can recursively load themselves; it is
+50 by default, and @code{nil} means infinity. Previously, Emacs signaled an
+error after just 3 recursive loads, which was boring.
+
+@item
+Byte-compiler warnings and error messages will leave out the line and
+character positions, in order to exercise your debugging skills.
+Also, there is no @code{with-no-warnings} macro---instead of
+suppressing compiler warnings, fix your code to avoid them!
+
+@item
+The function @code{unsafep} has been removed.
+
+@item
+File local variables can now specify a string with text properties.
+Since arbitrary Lisp expressions can be embedded in text properties,
+this can provide you with a great deal of flexibility and power. On
+the other hand, @code{safe-local-eval-forms} and the
+@code{safe-local-eval-function} function property have no special
meaning.
@item
-The base64 conversion functions have been eliminated.
+You can no longer use @code{char-displayable-p} to test if Emacs can
+display a certain character.
@item
-Wildcard support has been eliminated from @code{find-file}
-and allied functions.
+The function @code{string-to-multibyte} is no longer available.
@item
-@code{file-attributes} returns the file size and the file inode number
-only as a simple integer.
+The @code{translation-table-for-input} translation table has been
+removed. Also, translation hash tables are no longer available, so we
+don't need the functions @code{lookup-character} and
+@code{lookup-integer}.
+
+@item
+The @code{table} argument to @code{translate-region} can no longer be
+a char-table; it has to be a string.
+
+@item
+The functions @code{merge-coding-systems} and
+@code{decode-coding-inserted-region}, and the variable
+@code{auto-coding-functions}, have been deleted. The
+@code{mime-text-unsuitable} coding system property no longer has any
+special meaning.
+
+@item
+If pure storage overflows while dumping, Emacs won't tell you how much
+additional pure storage it needs. Try adding in increments of 20000,
+until you have enough.
+
+@item
+The variables @code{gc-elapsed}, @code{gcs-done}, and
+@code{post-gc-hook} have been garbage-collected.
@end itemize
+
+@ignore
+ arch-tag: 1d0ef137-2bad-430e-ae8e-d820d569b5a6
+@end ignore