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.

@c -*-texinfo-*-
@c This is part of the XEmacs Lisp Reference Manual.
@c Copyright (C) 1994, 1995 Ben Wing.
@c Copyright (C) 1999 Andy Piper.
@c Copyright (C) 1999 Stephen J. Turnbull.
@c See the file lispref.texi for copying conditions.
@setfilename ../../info/gutter.info
@node Gutter, Scrollbars, Toolbar, top
@chapter Gutter
@cindex gutter

  A gutter is a rectangle displayed along one edge of a frame.  It
can contain arbitrary text or graphics.

@menu
* Gutter Intro::		An introduction.
* Creating Gutters::            How to create a gutter.
* Specifying a Gutter::		Setting a gutter's contents.
* Other Gutter Variables::	Controlling the size of gutters.
* Common Gutter Widgets::       Things to put in gutters.
@end menu

@node Gutter Intro, Creating Gutters, Gutter, Gutter
@section Gutter Intro

  A @dfn{gutter} is a rectangle displayed along one edge of a frame.  It
can contain arbitrary text or graphics.  It could be considered a
generalization of a toolbar, although toolbars are not currently
implemented using gutters.

  In XEmacs, a gutter can be displayed along any of the four edges
of the frame, and two or more different edges can be displaying
gutters simultaneously.  The contents, thickness, and visibility of
the gutters can be controlled separately, and the values can
be per-buffer, per-frame, etc., using specifiers (@pxref{Specifiers}).

  Normally, there is one gutter displayed in a frame.  Usually, this is
the default gutter, containing buffer tabs, but modes can override this
and substitute their own gutter.  This default gutter is usually
positioned along the top of the frame, but this can be changed using
@code{set-default-gutter-position}.

  Note that, for each of the gutter properties (contents, thickness,
and visibility), there is a separate specifier for each of the four
gutter positions (top, bottom, left, and right), and an additional
specifier for the ``default'' gutter, i.e. the gutter whose
position is controlled by @code{set-default-gutter-position}.  The
way this works is that @code{set-default-gutter-position} arranges
things so that the appropriate position-specific specifiers for the
default position inherit from the corresponding default specifiers.
That way, if the position-specific specifier does not give a value
(which it usually doesn't), then the value from the default
specifier applies.  If you want to control the default gutter, you
just change the default specifiers, and everything works.  A package
such as VM that wants to put its own gutter in a different location
from the default just sets the position-specific specifiers, and if
the user sets the default gutter to the same position, it will just
not be visible.

@node Creating Gutters, Specifying a Gutter, Gutter Intro, Gutter
@section Creating Gutters

@defun make-gutter-specifier spec-list

Return a new @code{gutter} specifier object with the given specification
list.  @var{spec-list} can be a list of specifications (each of which is
a cons of a locale and a list of instantiators), a single instantiator,
or a list of instantiators.  @xref{Specifiers}, for more information
about specifiers.

Gutter specifiers are used to specify the format of a gutter.  The
values of the variables @code{default-gutter}, @code{top-gutter},
@code{left-gutter}, @code{right-gutter}, and @code{bottom-gutter} are
always gutter specifiers.

Valid gutter instantiators are called ``gutter descriptors.''  A gutter
descriptor may be a string, a property-list with symbol keys and string
values, or @code{nil}.  If @code{nil}, nothing will be displayed in the
gutter.  If a string, the string will be displayed, with text properties
such as faces and additional glyphs taken from the extents in the
string, if any.  If a property-list of strings, the string values will
be conditionally concatenated according to the contents of the
corresponding @samp{gutter-visible} variable, and displayed according to
any text properties they contain.
@end defun

@defun make-gutter-size-specifier spec-list

Return a new @code{gutter-size} specifier object with the given spec
list.  @var{spec-list} can be a list of specifications (each of which is
a cons of a locale and a list of instantiators), a single instantiator,
or a list of instantiators.  @xref{Specifiers}, for more information
about specifiers.

Gutter-size specifiers are used to specify the size of a gutter.
The width of top and bottom gutters and the height of left and right
gutters are always adjusted to the size of the frame, so ``size'' means
``thickness,'' @emph{i.e.}, height for top and bottom gutters and width
for left and right gutters.  The values of the variables
@code{default-gutter-size}, @code{top-gutter-size},
@code{left-gutter-size}, @code{right-gutter-size}, and
@code{bottom-gutter-size} are always gutter-size specifiers.

Valid gutter-size instantiators are either integers or the special
symbol @code{autodetect}.  If a gutter-size is set to @code{autodetect}
them the size of the gutter will be adjusted to just accommodate the
gutter's contents.  @code{autodetect} only works for top and bottom
gutters.
@end defun

@defun make-gutter-visible-specifier spec-list

Return a new @code{gutter-visible} specifier object with the given spec
list.  @var{spec-list} can be a list of specifications (each of which is
a cons of a locale and a list of instantiators), a single instantiator,
or a list of instantiators.  @xref{Specifiers}, for more information
about specifiers.

Gutter-visible specifiers are used to specify the visibility of a
gutter.  The values of the variables @code{default-gutter-visible-p},
@code{top-gutter-visible-p}, @code{left-gutter-visible-p},
@code{right-gutter-visible-p}, and @code{bottom-gutter-visible-p} are
always gutter-visible specifiers.

Valid gutter-visible instantiators are @code{t}, @code{nil} or a list of
symbols.  If a gutter-visible instantiator is set to a list of symbols,
and the corresponding gutter specification is a property-list of strings,
then property values of the gutter specification will only be visible if the
corresponding key occurs in the gutter-visible instantiator.
@end defun

@node Specifying a Gutter, Other Gutter Variables, Creating Gutters, Gutter
@section Specifying a Gutter

  In order to specify the contents of a gutter, set one of the specifier
variables @code{default-gutter}, @code{top-gutter},
@code{bottom-gutter}, @code{left-gutter}, or @code{right-gutter}.
These are specifiers, which means you set them with @code{set-specifier}
and query them with @code{specifier-specs} or @code{specifier-instance}.
You will get an error if you try to set them using @code{setq}.  The
valid instantiators for these specifiers are gutter descriptors, as
described above.  @xref{Specifiers}, for more information.

  Most of the time, you will set @code{default-gutter}, which allows
the user to choose where the gutter should go.

@defvr Specifier default-gutter
The position of this gutter is specified in the function
@code{default-gutter-position}.  If the corresponding
position-specific gutter (e.g. @code{top-gutter} if
@code{default-gutter-position} is @code{top}) does not specify a
gutter in a particular domain, then the value of @code{default-gutter}
in that domain, of any, will be used instead.
@end defvr

  Note that the gutter at any particular position will not be displayed
unless its thickness (width or height, depending on orientation) is
non-zero and its visibility status is true.  The thickness is controlled
by the specifiers @code{top-gutter-height},
@code{bottom-gutter-height}, @code{left-gutter-width}, and
@code{right-gutter-width}, and the visibility status is controlled by
the specifiers @code{top-gutter-visible-p},
@code{bottom-gutter-visible-p}, @code{left-gutter-visible-p}, and
@code{right-gutter-visible-p} (@pxref{Other Gutter Variables}).

@defun set-default-gutter-position position
This function sets the position that the @code{default-gutter} will be
displayed at.  Valid positions are the symbols @code{top},
@code{bottom}, @code{left} and @code{right}.  What this actually does is
set the fallback specifier for the position-specific specifier
corresponding to the given position to @code{default-gutter}, and set
the fallbacks for the other position-specific specifiers to @code{nil}.
It also does the same thing for the position-specific thickness and
visibility specifiers, which inherit from one of
@code{default-gutter-height} or @code{default-gutter-width}, and from
@code{default-gutter-visible-p}, respectively (@pxref{Other Gutter
Variables}).
@end defun

@defun default-gutter-position
This function returns the position that the @code{default-gutter} will
be displayed at.
@end defun

  You can also explicitly set a gutter at a particular position.  When
redisplay determines what to display at a particular position in a
particular domain (i.e. window), it first consults the position-specific
gutter.  If that does not yield a gutter descriptor, the
@code{default-gutter} is consulted if @code{default-gutter-position}
indicates this position.

@defvr Specifier top-gutter
Specifier for the gutter at the top of the frame.
@end defvr

@defvr Specifier bottom-gutter
Specifier for the gutter at the bottom of the frame.
@end defvr

@defvr Specifier left-gutter
Specifier for the gutter at the left edge of the frame.
@end defvr

@defvr Specifier right-gutter
Specifier for the gutter at the right edge of the frame.
@end defvr

@defun gutter-specifier-p object
This function returns non-@code{nil} if @var{object} is a gutter specifier.
Gutter specifiers are the actual objects contained in the gutter
variables described above, and their valid instantiators are
gutter descriptors.
@end defun

@node Other Gutter Variables, Common Gutter Widgets, Specifying a Gutter, Gutter
@section Other Gutter Variables

  The variables to control the gutter thickness, visibility status, and
captioned status are all specifiers.  @xref{Specifiers}.

@defvr Specifier default-gutter-height
This specifies the height of the default gutter, if it's oriented
horizontally.  The position of the default gutter is specified by the
function @code{set-default-gutter-position}.  If the corresponding
position-specific gutter thickness specifier
(e.g. @code{top-gutter-height} if @code{default-gutter-position} is
@code{top}) does not specify a thickness in a particular domain (a
window or a frame), then the value of @code{default-gutter-height} or
@code{default-gutter-width} (depending on the gutter orientation) in
that domain, if any, will be used instead.
@end defvr

@defvr Specifier default-gutter-width
This specifies the width of the default gutter, if it's oriented
vertically.  This behaves like @code{default-gutter-height}.
@end defvr

  Note that @code{default-gutter-height} is only used when
@code{default-gutter-position} is @code{top} or @code{bottom}, and
@code{default-gutter-width} is only used when
@code{default-gutter-position} is @code{left} or @code{right}.

@defvr Specifier top-gutter-height
This specifies the height of the top gutter.
@end defvr

@defvr Specifier bottom-gutter-height
This specifies the height of the bottom gutter.
@end defvr

@defvr Specifier left-gutter-width
This specifies the width of the left gutter.
@end defvr

@defvr Specifier right-gutter-width
This specifies the width of the right gutter.
@end defvr

  Note that all of the position-specific gutter thickness specifiers
have a fallback value of zero when they do not correspond to the
default gutter.  Therefore, you will have to set a non-zero thickness
value if you want a position-specific gutter to be displayed.

@defvr Specifier default-gutter-visible-p
This specifies whether the default gutter is visible.  The position of
the default gutter is specified by the function
@code{set-default-gutter-position}.  If the corresponding position-specific
gutter visibility specifier (e.g. @code{top-gutter-visible-p} if
@code{default-gutter-position} is @code{top}) does not specify a
visible-p value in a particular domain (a window or a frame), then the
value of @code{default-gutter-visible-p} in that domain, if any, will
be used instead.
@end defvr

@defvr Specifier top-gutter-visible-p
This specifies whether the top gutter is visible.
@end defvr

@defvr Specifier bottom-gutter-visible-p
This specifies whether the bottom gutter is visible.
@end defvr

@defvr Specifier left-gutter-visible-p
This specifies whether the left gutter is visible.
@end defvr

@defvr Specifier right-gutter-visible-p
This specifies whether the right gutter is visible.
@end defvr

@code{default-gutter-visible-p} and all of the position-specific
gutter visibility specifiers have a fallback value of true.

@c #### is this true?
  Internally, gutter thickness and visibility specifiers are instantiated
in both window and frame domains, for different purposes.  The value in
the domain of a frame's selected window specifies the actual gutter
thickness or visibility that you will see in that frame.  The value in
the domain of a frame itself specifies the gutter thickness or
visibility that is used in frame geometry calculations.

  Thus, for example, if you set the frame width to 80 characters and the
left gutter width for that frame to 68 pixels, then the frame will be
sized to fit 80 characters plus a 68-pixel left gutter.  If you then
set the left gutter width to 0 for a particular buffer (or if that
buffer does not specify a left gutter or has a @code{nil} value specified for
@code{left-gutter-visible-p}), you will find that, when that buffer is
displayed in the selected window, the window will have a width of 86 or
87 characters -- the frame is sized for a 68-pixel left gutter but the
selected window specifies that the left gutter is not visible, so it is
expanded to take up the slack.

@node Common Gutter Widgets, , Other Gutter Variables, Gutter
@section Common Gutter Widgets

  A gutter can contain arbitrary text.  So, for example, in an Info
buffer you could put the title of the current node in the top gutter,
and it would not scroll out of view in a long node.  (This is an
artificial example, since usually the node name is sufficiently
descriptive, and Info puts that in the mode line.)

  A more common use for the gutter is to hold some kind of active
widget.  The buffer-tab facility, available in all XEmacs frames,
creates an array of file-folder-like tabs, which the user can click with
the mouse to switch buffers.  W3 and font-lock use progress-bar widgets in the
bottom gutter to give a visual indication of the progress of
time-consuming operations like downloading and syntax highlighting.

@c #### Remove the following sentence when the subnodes are created.
These widgets are currently documented only in the library
@file{gutter-items}.

@menu
* Buffer Tabs::         Tabbed divider index metaphor for switching buffers.
* Progress Bars::       Visual indication of operation progress.
@end menu


@node Buffer Tabs, Progress Bars, ,Common Gutter Widgets
@subsection Buffer Tabs

  Not documented yet.


@node Progress Bars,  , Buffer Tabs, Common Gutter Widgets
@subsection Progress Bars

  Not documented yet.