Mercurial > hg > xemacs-beta
annotate man/xemacs/major.texi @ 5353:38e24b8be4ea
Improve the lexical scoping in #'block, #'return-from.
lisp/ChangeLog addition:
2011-02-07 Aidan Kehoe <kehoea@parhasard.net>
* bytecomp.el:
* bytecomp.el (byte-compile-initial-macro-environment):
Shadow `block', `return-from' here, we implement them differently
when byte-compiling.
* bytecomp.el (byte-compile-active-blocks): New.
* bytecomp.el (byte-compile-block-1): New.
* bytecomp.el (byte-compile-return-from-1): New.
* bytecomp.el (return-from-1): New.
* bytecomp.el (block-1): New.
These are two aliases that exist to have their own associated
byte-compile functions, which functions implement `block' and
`return-from'.
* cl-extra.el (cl-macroexpand-all):
Fix a bug here when macros in the environment have been compiled.
* cl-macs.el (block):
* cl-macs.el (return):
* cl-macs.el (return-from):
Be more careful about lexical scope in these macros.
* cl.el:
* cl.el ('cl-block-wrapper): Removed.
* cl.el ('cl-block-throw): Removed.
These aren't needed in code generated by this XEmacs. They
shouldn't be needed in code generated by XEmacs 21.4, but if it
turns out the packages do need them, we can put them back.
2011-01-30 Mike Sperber <mike@xemacs.org>
* font-lock.el (font-lock-fontify-pending-extents): Don't fail if
`font-lock-mode' is unset, which can happen in the middle of
`revert-buffer'.
2011-01-23 Aidan Kehoe <kehoea@parhasard.net>
* cl-macs.el (delete):
* cl-macs.el (delq):
* cl-macs.el (remove):
* cl-macs.el (remq):
Don't use the compiler macro if these functions were given the
wrong number of arguments, as happens in lisp-tests.el.
* cl-seq.el (remove, remq): Removed.
I added these to subr.el, and forgot to remove them from here.
2011-01-22 Aidan Kehoe <kehoea@parhasard.net>
* bytecomp.el (byte-compile-setq, byte-compile-set):
Remove kludge allowing keywords' values to be set, all the code
that does that is gone.
* cl-compat.el (elt-satisfies-test-p):
* faces.el (set-face-parent):
* faces.el (face-doc-string):
* gtk-font-menu.el:
* gtk-font-menu.el (gtk-reset-device-font-menus):
* msw-font-menu.el:
* msw-font-menu.el (mswindows-reset-device-font-menus):
* package-get.el (package-get-installedp):
* select.el (select-convert-from-image-data):
* sound.el:
* sound.el (load-sound-file):
* x-font-menu.el (x-reset-device-font-menus-core):
Don't quote keywords, they're self-quoting, and the
win from backward-compatibility is sufficiently small now that the
style problem overrides it.
2011-01-22 Aidan Kehoe <kehoea@parhasard.net>
* cl-macs.el (block, return-from): Require that NAME be a symbol
in these macros, as always documented in the #'block docstring and
as required by Common Lisp.
* descr-text.el (unidata-initialize-unihan-database):
Correct the use of non-symbols in #'block and #'return-from in
this function.
2011-01-15 Aidan Kehoe <kehoea@parhasard.net>
* cl-extra.el (concatenate): Accept more complicated TYPEs in this
function, handing the sequences over to #'coerce if we don't
understand them here.
* cl-macs.el (inline): Don't proclaim #'concatenate as inline, its
compiler macro is more useful than doing that.
2011-01-11 Aidan Kehoe <kehoea@parhasard.net>
* subr.el (delete, delq, remove, remq): Move #'remove, #'remq
here, they don't belong in cl-seq.el; move #'delete, #'delq here
from fns.c, implement them in terms of #'delete*, allowing support
for sequences generally.
* update-elc.el (do-autoload-commands): Use #'delete*, not #'delq
here, now the latter's no longer dumped.
* cl-macs.el (delete, delq): Add compiler macros transforming
#'delete and #'delq to #'delete* calls.
2011-01-10 Aidan Kehoe <kehoea@parhasard.net>
* dialog.el (make-dialog-box): Correct a misplaced parenthesis
here, thank you Mats Lidell in 87zkr9gqrh.fsf@mail.contactor.se !
2011-01-02 Aidan Kehoe <kehoea@parhasard.net>
* dialog.el (make-dialog-box):
* list-mode.el (display-completion-list):
These functions used to use cl-parsing-keywords; change them to
use defun* instead, fixing the build. (Not sure what led to me
not including this change in d1b17a33450b!)
2011-01-02 Aidan Kehoe <kehoea@parhasard.net>
* cl-macs.el (define-star-compiler-macros):
Make sure the form has ITEM and LIST specified before attempting
to change to calls with explicit tests; necessary for some tests
in lisp-tests.el to compile correctly.
(stable-union, stable-intersection): Add compiler macros for these
functions, in the same way we do for most of the other functions
in cl-seq.el.
2011-01-01 Aidan Kehoe <kehoea@parhasard.net>
* cl-macs.el (dolist, dotimes, do-symbols, macrolet)
(symbol-macrolet):
Define these macros with defmacro* instead of parsing the argument
list by hand, for the sake of style and readability; use backquote
where appropriate, instead of calling #'list and and friends, for
the same reason.
2010-12-30 Aidan Kehoe <kehoea@parhasard.net>
* x-misc.el (device-x-display):
Provide this function, documented in the Lispref for years, but
not existing previously. Thank you Julian Bradfield, thank you
Jeff Mincy.
2010-12-30 Aidan Kehoe <kehoea@parhasard.net>
* cl-seq.el:
Move the heavy lifting from this file to C. Dump the
cl-parsing-keywords macro, but don't use defun* for the functions
we define that do take keywords, dynamic scope lossage makes that
not practical.
* subr.el (sort, fillarray): Move these aliases here.
(map-plist): #'nsublis is now built-in, but at this point #'eql
isn't necessarily available as a test; use #'eq.
* obsolete.el (cl-delete-duplicates): Make this available for old
compiler macros and old code.
(memql): Document that this is equivalent to #'member*, and worse.
* cl.el (adjoin, subst): Removed. These are in C.
2010-12-30 Aidan Kehoe <kehoea@parhasard.net>
* simple.el (assoc-ignore-case): Remove a duplicate definition of
this function (it's already in subr.el).
* iso8859-1.el (char-width):
On non-Mule, make this function equivalent to that produced by
(constantly 1), but preserve its docstring.
* subr.el (subst-char-in-string): Define this in terms of
#'substitute, #'nsubstitute.
(string-width): Define this using #'reduce and #'char-width.
(char-width): Give this a simpler definition, it makes far more
sense to check for mule at load time and redefine, as we do in
iso8859-1.el.
(store-substring): Implement this in terms of #'replace, now
#'replace is cheap.
2010-12-30 Aidan Kehoe <kehoea@parhasard.net>
* update-elc.el (lisp-files-needed-for-byte-compilation)
(lisp-files-needing-early-byte-compilation):
cl-macs belongs in the former, not the latter, it is as
fundamental as bytecomp.el.
2010-12-30 Aidan Kehoe <kehoea@parhasard.net>
* cl.el:
Provde the Common Lisp program-error, type-error as error
symbols. This doesn't nearly go far enough for anyone using the
Common Lisp errors.
2010-12-29 Aidan Kehoe <kehoea@parhasard.net>
* cl-macs.el (delete-duplicates):
If the form has an incorrect number of arguments, don't attempt a
compiler macroexpansion.
2010-12-29 Aidan Kehoe <kehoea@parhasard.net>
* cl-macs.el (cl-safe-expr-p):
Forms that start with the symbol lambda are also safe.
2010-12-29 Aidan Kehoe <kehoea@parhasard.net>
* cl-macs.el (= < > <= >=):
For these functions' compiler macros, the optimisation is safe
even if the first and the last arguments have side effects, since
they're only used the once.
2010-12-29 Aidan Kehoe <kehoea@parhasard.net>
* cl-macs.el (inline-side-effect-free-compiler-macros):
Unroll a loop here at macro-expansion time, so these compiler
macros are compiled. Use #'eql instead of #'eq in a couple of
places for better style.
2010-12-29 Aidan Kehoe <kehoea@parhasard.net>
* cl-extra.el (notany, notevery): Avoid some dynamic scope
stupidity with local variable names in these functions, when they
weren't prefixed with cl-; go into some more detail in the doc
strings.
2010-12-29 Aidan Kehoe <kehoea@parhasard.net>
* byte-optimize.el (side-effect-free-fns): #'remove, #'remq are
free of side-effects.
(side-effect-and-error-free-fns):
Drop dot, dot-marker from the list.
2010-11-17 Aidan Kehoe <kehoea@parhasard.net>
* cl-extra.el (coerce):
In the argument list, name the first argument OBJECT, not X; the
former name was always used in the doc string and is clearer.
Handle vector type specifications which include the length of the
target sequence, error if there's a mismatch.
* cl-macs.el (cl-make-type-test): Handle type specifications
starting with the symbol 'eql.
2010-11-14 Aidan Kehoe <kehoea@parhasard.net>
* cl-macs.el (eql): Don't remove the byte-compile property of this
symbol. That was necessary to override a bug in bytecomp.el where
#'eql was confused with #'eq, which bug we no longer have.
If neither expression is constant, don't attempt to handle the
expression in this compiler macro, leave it to byte-compile-eql,
which produces better code anyway.
* bytecomp.el (eq): #'eql is not the function associated with the
byte-eq byte code.
(byte-compile-eql): Add an explicit compile method for this
function, for cases where the cl-macs compiler macro hasn't
reduced it to #'eq or #'equal.
2010-10-25 Aidan Kehoe <kehoea@parhasard.net>
Add compiler macros and compilation sanity-checking for various
functions that take keywords.
* byte-optimize.el (side-effect-free-fns): #'symbol-value is
side-effect free and not error free.
* bytecomp.el (byte-compile-normal-call): Check keyword argument
lists for sanity; store information about the positions where
keyword arguments start using the new byte-compile-keyword-start
property.
* cl-macs.el (cl-const-expr-val): Take a new optional argument,
cl-not-constant, defaulting to nil, in this function; return it if
the expression is not constant.
(cl-non-fixnum-number-p): Make this into a separate function, we
want to pass it to #'every.
(eql): Use it.
(define-star-compiler-macros): Use the same code to generate the
member*, assoc* and rassoc* compiler macros; special-case some
code in #'add-to-list in subr.el.
(remove, remq): Add compiler macros for these two functions, in
preparation for #'remove being in C.
(define-foo-if-compiler-macros): Transform (remove-if-not ...) calls to
(remove ... :if-not) at compile time, which will be a real win
once the latter is in C.
(define-substitute-if-compiler-macros)
(define-subst-if-compiler-macros): Similarly for these functions.
(delete-duplicates): Change this compiler macro to use
#'plists-equal; if we don't have information about the type of
SEQUENCE at compile time, don't bother attempting to inline the
call, the function will be in C soon enough.
(equalp): Remove an old commented-out compiler macro for this, if
we want to see it it's in version control.
(subst-char-in-string): Transform this to a call to nsubstitute or
nsubstitute, if that is appropriate.
* cl.el (ldiff): Don't call setf here, this makes for a load-time
dependency problem in cl-macs.el
2010-06-14 Stephen J. Turnbull <stephen@xemacs.org>
* term/vt100.el:
Refer to XEmacs, not GNU Emacs, in permissions.
* term/bg-mouse.el:
* term/sup-mouse.el:
Put copyright notice in canonical "Copyright DATE AUTHOR" form.
Refer to XEmacs, not GNU Emacs, in permissions.
* site-load.el:
Add permission boilerplate.
* mule/canna-leim.el:
* alist.el:
Refer to XEmacs, not APEL/this program, in permissions.
* mule/canna-leim.el:
Remove my copyright, I've assigned it to the FSF.
2010-06-14 Stephen J. Turnbull <stephen@xemacs.org>
* gtk.el:
* gtk-widget-accessors.el:
* gtk-package.el:
* gtk-marshal.el:
* gtk-compose.el:
* gnome.el:
Add copyright notice based on internal evidence.
2010-06-14 Stephen J. Turnbull <stephen@xemacs.org>
* easymenu.el: Add reference to COPYING to permission notice.
* gutter.el:
* gutter-items.el:
* menubar-items.el:
Fix typo "Xmacs" in permissions notice.
2010-06-14 Stephen J. Turnbull <stephen@xemacs.org>
* auto-save.el:
* font.el:
* fontconfig.el:
* mule/kinsoku.el:
Add "part of XEmacs" text to permission notice.
2010-10-14 Aidan Kehoe <kehoea@parhasard.net>
* byte-optimize.el (side-effect-free-fns):
* cl-macs.el (remf, getf):
* cl-extra.el (tailp, cl-set-getf, cl-do-remf):
* cl.el (ldiff, endp):
Tighten up Common Lisp compatibility for #'ldiff, #'endp, #'tailp;
add circularity checking for the first two.
#'cl-set-getf and #'cl-do-remf were Lisp implementations of
#'plist-put and #'plist-remprop; change the names to aliases,
changes the macros that use them to using #'plist-put and
#'plist-remprop directly.
2010-10-12 Aidan Kehoe <kehoea@parhasard.net>
* abbrev.el (fundamental-mode-abbrev-table, global-abbrev-table):
Create both these abbrev tables using the usual
#'define-abbrev-table calls, rather than attempting to
special-case them.
* cl-extra.el: Force cl-macs to be loaded here, if cl-extra.el is
being loaded interpreted. Previously other, later files would
redundantly call (load "cl-macs") when interpreted, it's more
reasonable to do it here, once.
* cmdloop.el (read-quoted-char-radix): Use defcustom here, we
don't have any dump-order dependencies that would prevent that.
* custom.el (eval-when-compile): Don't load cl-macs when
interpreted or when byte-compiling, rely on cl-extra.el in the
former case and the appropriate entry in bytecomp-load-hook in the
latter. Get rid of custom-declare-variable-list, we have no
dump-time dependencies that would require it.
* faces.el (eval-when-compile): Don't load cl-macs when
interpreted or when byte-compiling.
* packages.el: Remove some inaccurate comments.
* post-gc.el (cleanup-simple-finalizers): Use #'delete-if-not
here, now the order of preloaded-file-list has been changed to
make it available.
* subr.el (custom-declare-variable-list): Remove. No need for it.
Also remove a stub define-abbrev-table from this file, given the
current order of preloaded-file-list there's no need for it.
2010-10-10 Aidan Kehoe <kehoea@parhasard.net>
* bytecomp.el (byte-compile-constp) Forms quoted with FUNCTION are
also constant.
(byte-compile-initial-macro-environment): In #'the, if FORM is
constant and does not match TYPE, warn at byte-compile time.
2010-10-10 Aidan Kehoe <kehoea@parhasard.net>
* backquote.el (bq-vector-contents, bq-list*): Remove; the former
is equivalent to (append VECTOR nil), the latter to (list* ...).
(bq-process-2): Use (append VECTOR nil) instead of using
#'bq-vector-contents to convert to a list.
(bq-process-1): Now we use list* instead of bq-list
* subr.el (list*): Moved from cl.el, since it is now required to
be available the first time a backquoted form is encountered.
* cl.el (list*): Move to subr.el.
2010-09-16 Aidan Kehoe <kehoea@parhasard.net>
* test-harness.el (Check-Message):
Add an omitted comma here, thank you the buildbot.
2010-09-16 Aidan Kehoe <kehoea@parhasard.net>
* hash-table.el (hash-table-key-list, hash-table-value-list)
(hash-table-key-value-alist, hash-table-key-value-plist):
Remove some useless #'nreverse calls in these files; our hash
tables have no order, it's not helpful to pretend they do.
* behavior.el (read-behavior):
Do the same in this file, in some code evidently copied from
hash-table.el.
2010-09-16 Aidan Kehoe <kehoea@parhasard.net>
* info.el (Info-insert-dir):
* format.el (format-deannotate-region):
* files.el (cd, save-buffers-kill-emacs):
Use #'some, #'every and related functions for applying boolean
operations to lists, instead of rolling our own ones that cons and
don't short-circuit.
2010-09-16 Aidan Kehoe <kehoea@parhasard.net>
* bytecomp.el (byte-compile-initial-macro-environment):
* cl-macs.el (the):
Rephrase the docstring, make its implementation when compiling
files a little nicer.
2010-09-16 Aidan Kehoe <kehoea@parhasard.net>
* descr-text.el (unidata-initialize-unicodedata-database)
(unidata-initialize-unihan-database, describe-char-unicode-data)
(describe-char-unicode-data):
Wrap calls to the database functions with (with-fboundp ...),
avoiding byte compile warnings on builds without support for the
database functions.
(describe-char): (reduce #'max ...), not (apply #'max ...), no
need to cons needlessly.
(describe-char): Remove a redundant lambda wrapping
#'extent-properties.
(describe-char-unicode-data): Call #'nsubst when replacing "" with
nil in the result of #'split-string, instead of consing inside
mapcar.
2010-09-16 Aidan Kehoe <kehoea@parhasard.net>
* x-faces.el (x-available-font-sizes):
* specifier.el (let-specifier):
* package-ui.el (pui-add-required-packages):
* msw-faces.el (mswindows-available-font-sizes):
* modeline.el (modeline-minor-mode-menu):
* minibuf.el (minibuf-directory-files):
Replace the O2N (delq nil (mapcar (lambda (W) (and X Y)) Z)) with
the ON (mapcan (lambda (W) (and X (list Y))) Z) in these files.
2010-09-16 Aidan Kehoe <kehoea@parhasard.net>
* cl-macs.el (= < > <= >=):
When these functions are handed more than two arguments, and those
arguments have no side effects, transform to a series of two
argument calls, avoiding funcall in the byte-compiled code.
* mule/mule-cmds.el (finish-set-language-environment):
Take advantage of this change in a function called 256 times at
startup.
2010-09-16 Aidan Kehoe <kehoea@parhasard.net>
* bytecomp.el (byte-compile-function-form, byte-compile-quote)
(byte-compile-quote-form):
Warn at compile time, and error at runtime, if a (quote ...) or a
(function ...) form attempts to quote more than one object.
2010-09-16 Aidan Kehoe <kehoea@parhasard.net>
* byte-optimize.el (byte-optimize-apply): Transform (apply 'nconc
(mapcar ...)) to (mapcan ...); warn about use of the first idiom.
* update-elc.el (do-autoload-commands):
* packages.el (packages-find-package-library-path):
* frame.el (frame-list):
* extents.el (extent-descendants):
* etags.el (buffer-tag-table-files):
* dumped-lisp.el (preloaded-file-list):
* device.el (device-list):
* bytecomp-runtime.el (proclaim-inline, proclaim-notinline)
Use #'mapcan, not (apply #'nconc (mapcar ...) in all these files.
* bytecomp-runtime.el (eval-when-compile, eval-and-compile):
In passing, mention that these macros also evaluate the body when
interpreted.
tests/ChangeLog addition:
2011-02-07 Aidan Kehoe <kehoea@parhasard.net>
* automated/lisp-tests.el:
Test lexical scope for `block', `return-from'; add a
Known-Bug-Expect-Failure for a contorted example that fails when
byte-compiled.
| author | Aidan Kehoe <kehoea@parhasard.net> |
|---|---|
| date | Mon, 07 Feb 2011 12:01:24 +0000 |
| parents | 40dc584fce16 |
| children |
| rev | line source |
|---|---|
| 428 | 1 |
| 2 @node Major Modes, Indentation, Mule, Top | |
| 3 @chapter Major Modes | |
| 4 @cindex major modes | |
| 5 @kindex TAB | |
| 6 @kindex DEL | |
| 7 @kindex LFD | |
| 8 | |
| 9 Emacs has many different @dfn{major modes}, each of which customizes | |
| 10 Emacs for editing text of a particular sort. The major modes are mutually | |
| 11 exclusive; at any time, each buffer has one major mode. The mode line | |
| 12 normally contains the name of the current major mode in parentheses. | |
| 13 @xref{Mode Line}. | |
| 14 | |
| 15 The least specialized major mode is called @dfn{Fundamental mode}. This | |
| 16 mode has no mode-specific redefinitions or variable settings. Each | |
| 2736 | 17 Emacs command behaves in its most generic manner, and each option is in its |
| 428 | 18 default state. For editing any specific type of text, such as Lisp code or |
| 19 English text, you should switch to the appropriate major mode, such as Lisp | |
| 20 mode or Text mode. | |
| 21 | |
| 22 Selecting a major mode changes the meanings of a few keys to become | |
| 23 more specifically adapted to the language being edited. @key{TAB}, | |
| 24 @key{DEL}, and @key{LFD} are changed frequently. In addition, commands | |
| 25 which handle comments use the mode to determine how to delimit comments. | |
| 26 Many major modes redefine the syntactical properties of characters | |
| 27 appearing in the buffer. @xref{Syntax}. | |
| 28 | |
| 2522 | 29 The major modes fall into three major groups. Programming modes |
| 2736 | 30 (@pxref{Programs}) are for specific programming languages. They tend to |
| 31 be line-oriented, often enforcing indentation. They emphasize | |
| 32 facilities for creating and displaying structure. Text modes | |
| 2522 | 33 (like Nroff mode, @TeX{} mode, Outline mode, XML mode, etc.@:) are for |
| 34 editing human readable text. The remaining major modes are not intended | |
| 35 for direct use in editing user files; they are used in buffers created | |
| 36 by Emacs for specific purposes. Examples of such modes include Dired | |
| 37 mode which is used for buffers made by Dired (@pxref{Dired}), Mail mode | |
| 38 for buffers made by @kbd{C-x m} (@pxref{Sending Mail}), and Shell mode | |
| 39 for buffers used for communicating with an inferior shell process | |
| 428 | 40 (@pxref{Interactive Shell}). |
| 41 | |
| 42 Most programming language major modes specify that only blank lines | |
| 43 separate paragraphs. This is so that the paragraph commands remain useful. | |
| 2736 | 44 @xref{Paragraphs}. They also cause Auto Fill minor mode to use the |
| 45 definition of | |
| 428 | 46 @key{TAB} to indent the new lines it creates. This is because most lines |
| 47 in a program are usually indented. @xref{Indentation}. | |
| 48 | |
| 49 @menu | |
| 50 * Choosing Modes:: How major modes are specified or chosen. | |
| 2522 | 51 * Mode Hooks:: Customizing a major mode |
| 428 | 52 @end menu |
| 53 | |
| 2522 | 54 @node Choosing Modes, Mode Hooks, Major Modes, Major Modes |
| 428 | 55 @section Choosing Major Modes |
| 56 | |
| 57 You can select a major mode explicitly for the current buffer, but | |
| 58 most of the time Emacs determines which mode to use based on the file | |
| 59 name or some text in the file. | |
| 60 | |
| 61 Use a @kbd{M-x} command to explicitly select a new major mode. Add | |
| 62 @code{-mode} to the name of a major mode to get the name of a command to | |
| 63 select that mode. For example, to enter Lisp mode, execute @kbd{M-x | |
| 64 lisp-mode}. | |
| 65 | |
| 66 @vindex auto-mode-alist | |
| 67 When you visit a file, Emacs usually chooses the right major mode | |
| 68 based on the file's name. For example, files whose names end in | |
| 69 @code{.c} are edited in C mode. The variable @code{auto-mode-alist} | |
| 70 controls the correspondence between file names and major mode. Its value | |
| 71 is a list in which each element has the form: | |
| 72 | |
| 73 @example | |
| 74 (@var{regexp} . @var{mode-function}) | |
| 75 @end example | |
| 76 | |
| 77 @noindent | |
| 78 For example, one element normally found in the list has the form | |
| 79 @code{(@t{"\\.c$"} . c-mode)}. It is responsible for selecting C mode | |
| 80 for files whose names end in @file{.c}. (Note that @samp{\\} is needed in | |
| 81 Lisp syntax to include a @samp{\} in the string, which is needed to | |
| 82 suppress the special meaning of @samp{.} in regexps.) The only practical | |
| 83 way to change this variable is with Lisp code. | |
| 84 | |
| 85 You can specify which major mode should be used for editing a certain | |
| 86 file by a special sort of text in the first non-blank line of the file. | |
| 87 The mode name should appear in this line both preceded and followed by | |
| 88 @samp{-*-}. Other text may appear on the line as well. For example, | |
| 89 | |
| 90 @example | |
| 91 ;-*-Lisp-*- | |
| 92 @end example | |
| 93 | |
| 94 @noindent | |
| 95 tells Emacs to use Lisp mode. Note how the semicolon is used to make Lisp | |
| 96 treat this line as a comment. Such an explicit specification overrides any | |
| 97 default mode based on the file name. | |
| 98 | |
| 99 Another format of mode specification is: | |
| 100 | |
| 101 @example | |
| 102 -*-Mode: @var{modename};-*- | |
| 103 @end example | |
| 104 | |
| 105 @noindent | |
| 106 which allows other things besides the major mode name to be specified. | |
| 107 However, Emacs does not look for anything except the mode name. | |
| 108 | |
| 109 The major mode can also be specified in a local variables list. | |
| 110 @xref{File Variables}. | |
| 111 | |
| 112 @vindex default-major-mode | |
| 113 When you visit a file that does not specify a major mode to use, or | |
| 114 when you create a new buffer with @kbd{C-x b}, Emacs uses the major mode | |
| 115 specified by the variable @code{default-major-mode}. Normally this | |
| 116 value is the symbol @code{fundamental-mode}, which specifies Fundamental | |
| 117 mode. If @code{default-major-mode} is @code{nil}, the major mode is | |
| 118 taken from the previously selected buffer. | |
| 2522 | 119 |
| 120 @node Mode Hooks, , Choosing Modes, Major Modes | |
| 121 @section Mode Hook Variables | |
| 122 | |
| 123 @cindex Hook variables | |
| 124 @cindex mode hook | |
| 125 @findex add-hook | |
| 126 @findex remove-hook | |
| 127 @vindex lisp-mode-hook | |
| 128 @vindex emacs-lisp-mode-hook | |
| 129 @vindex lisp-interaction-mode-hook | |
| 130 @vindex scheme-mode-hook | |
| 131 | |
| 132 The last step taken by a major mode, by convention, is to invoke a | |
| 2736 | 133 list of user supplied functions that are stored in a @dfn{hook} |
| 134 variable. This allows a user to further customize the major mode, and | |
| 135 is particularly convenient for associating minor modes with major modes. | |
| 136 @xref{Minor Modes}. For example, to automatically turn on the Auto Fill | |
| 137 minor mode when Text mode is invoked, add the following code to the | |
| 138 initialization file (@pxref{Init File}) | |
| 2522 | 139 |
| 140 @example | |
| 141 (add-hook 'text-mode-hook 'turn-on-auto-fill) | |
| 142 @end example | |
| 143 | |
| 2736 | 144 Derived modes often @dfn{inherit} the parent mode's hooks. For |
| 145 example, Texinfo Mode is derived from Text Mode, so customizing | |
| 146 @code{text-mode-hook} as above will also enable Auto Fill minor mode in | |
| 147 buffers containing Texinfo files. | |
| 148 | |
| 149 Hooks are also commonly used to set up buffer local variables | |
| 150 (@pxref{Locals}). | |
| 151 | |
| 152 The name of the hook variable is created by appending the string | |
| 153 @code{-hook} to the name of the function used to invoke the major mode. | |
| 154 For example, as seen above, the hook variable used by Text Mode would be | |
| 155 named @code{text-mode-hook}. By convention the mode hook function | |
| 156 receives no arguments. If a hook variable does not exist, or it has the | |
| 157 value @code{nil}, the major mode simply ignores it. | |
| 158 | |
| 159 The recommended way to add functions to a hook variable is with the | |
| 160 @code{add-hook} function. | |
| 161 @code{add-hook} will check that the function is not already | |
| 2522 | 162 listed in the hook variable before adding it. It will also create a hook |
| 163 variable with the value @code{nil} if one does not exist before adding | |
| 164 the function. @code{add-hook} adds functions to the front of the hook | |
| 165 variable list. This means that the last hook added is run first by the | |
| 166 major mode. It is considered very poor style to write hook functions | |
| 167 that depend on the order that hooks are executed. | |
| 168 | |
| 169 Hooks can be removed from hook variables with @code{remove-hook}. | |
| 170 | |
| 171 |