@defvar buffer-invisibility-spec
This variable specifies which kinds of @code{invisible} properties
-actually make a character invisible.
+actually make a character invisible. Setting this variable makes it
+buffer-local.
@table @asis
@item @code{t}
@item evaporate
@kindex evaporate @r{(overlay property)}
If this property is non-@code{nil}, the overlay is deleted automatically
-if it becomes empty (i.e., if its length becomes zero). However,
-if the overlay is @emph{already} empty, @code{evaporate} does not
-delete it.
+if it becomes empty (i.e., if its length becomes zero). If you give
+an empty overlay a non-@code{nil} @code{evaporate} property, that deletes
+it immediately.
@item local-map
@cindex keymap of character (and overlays)
@end defun
@defun face-differs-from-default-p face &optional frame
-This returns @code{t} if the face @var{face} displays differently from
-the default face. A face is considered to be ``the same'' as the
-default face if each attribute is either the same as that of the default
-face, or unspecified (meaning to inherit from the default).
+This returns non-@code{nil} if the face @var{face} displays
+differently from the default face.
@end defun
@node Auto Faces
@code{display} property, this feature is available starting in Emacs 21.
Emacs can display a number of different image formats; some of them
-are supported only if particular support libraries are installed on your
-machine. The supported image formats include XBM, XPM (needing the
+are supported only if particular support libraries are installed on
+your machine. In some environments, Emacs allows loading image
+libraries on demand; if so, the variable @code{image-library-alist}
+can be used to modify the set of known names for these dynamic
+libraries (though it is not posible to add new image formats).
+
+ The supported image formats include XBM, XPM (needing the
libraries @code{libXpm} version 3.4k and @code{libz}), GIF (needing
@code{libungif} 4.1.0), Postscript, PBM, JPEG (needing the
@code{libjpeg} library version v6a), TIFF (needing @code{libtiff} v3.4),
@defvar image-types
This variable contains a list of those image type symbols that are
-supported in the current configuration.
+potentially supported in the current configuration.
+@emph{Potentially} here means that Emacs knows about the image types,
+not necessarily that they can be loaded (they could depend on
+unavailable dynamic libraries, for example).
+
+To know which image types are really available, use
+@code{image-type-available-p}.
@end defvar
+@defvar image-library-alist
+This in an alist of image types vs external libraries needed to
+display them.
+
+Each element is a list @code{(@var{image-type} @var{library}...)},
+where the car is a supported image format from @code{image-types}, and
+the rest are strings giving alternate filenames for the corresponding
+external libraries to load.
+
+Emacs tries to load the libraries in the order they appear on the
+list; if none is loaded, the running session of Emacs won't support
+the image type. @code{pbm} and @code{xbm} don't need to be listed;
+they're always supported.
+
+This variable is ignored if the image libraries are statically linked
+into Emacs.
+@end defvar
+
+@defun image-type-available-p type
+@findex image-type-available-p
+
+This function returns non-@code{nil} if image type @var{type} is
+available, i.e., if images of this type can be loaded and displayed in
+Emacs. @var{type} should be one of the types contained in
+@code{image-types}.
+
+For image types whose support libraries are statically linked, this
+function always returns @code{t}; for other image types, it returns
+@code{t} if the dynamic library could be loaded, @code{nil} otherwise.
+@end defun
+
@menu
* Image Descriptors:: How to specify an image for use in @code{:display}.
* XBM Images:: Special features for XBM format.
For GIF images, specify image type @code{gif}. Because of the patents
in the US covering the LZW algorithm, the continued use of GIF format is
a problem for the whole Internet; to end this problem, it is a good idea
-for everyone, even outside the US, to stop using GIFS right away
+for everyone, even outside the US, to stop using GIFs right away
(@uref{http://www.burnallgifs.org/}). But if you still want to use
them, Emacs can display them.
etc. Emacs uses buttons for the hyper-links in help text and the like.
A button is essentially a set of properties attached (via text
-properties or overlays) to a region of text in an emacs buffer, which
+properties or overlays) to a region of text in an Emacs buffer, which
are called its button properties. @xref{Button Properties}.
One of the these properties (@code{action}) is a function, which will
The invoked function may then examine the button and use its other
properties as desired.
-In some ways the emacs button package duplicates functionality offered
+In some ways the Emacs button package duplicates functionality offered
by the widget package (@pxref{Top, , Introduction, widget, The Emacs
Widget Library}), but the button package has the advantage that it is
much faster, much smaller, and much simpler to use (for elisp
@menu
* Button Properties:: Button properties with special meanings.
* Button Types:: Defining common properties for classes of buttons.
-* Making Buttons:: Adding buttons to emacs buffers.
+* Making Buttons:: Adding buttons to Emacs buffers.
* Manipulating Buttons:: Getting and setting properties of buttons.
* Button Buffer Commands:: Buffer-wide commands and bindings for buttons.
* Manipulating Button Types::
@item face
@kindex face @r{(button property)}
-This is an emacs face controlling how buttons of this type are
+This is an Emacs face controlling how buttons of this type are
displayed; by default this is the @code{button} face.
@item mouse-face
@kindex mouse-face @r{(button property)}
This is an additional face which controls appearance during
mouse-overs (merged with the usual button face); by default this is
-the usual emacs @code{highlight} face.
+the usual Emacs @code{highlight} face.
@item keymap
@kindex keymap @r{(button property)}
@item help-echo
@kindex help-index @r{(button property)}
-A string displayed by the emacs tool-tip help system; by default,
+A string displayed by the Emacs tool-tip help system; by default,
@code{"mouse-2, RET: Push this button"}.
@item button
Buttons are associated with a region of text, using an overlay or
text-properties to hold button-specific information, all of which are
initialized from the button's type (which defaults to the built-in
-button type @code{button}). Like all emacs text, the appearance of
+button type @code{button}). Like all Emacs text, the appearance of
the button is governed by the @code{face} property; by default (via
the @code{face} property inherited from the @code{button} button-type)
this is a simple underline, like a typical web-page link.
Insert a button with the label @var{label}.
@end defun
-The following functions are similar, but use emacs text-properties
+The following functions are similar, but use Emacs text-properties
(@pxref{Text Properties}) to hold the button properties, making the
button actually part of the text instead of being a property of the
buffer (using text-properties is usually faster than using overlays,
@cindex button buffer commands
These are commands and functions for locating and operating on
-buttons in an emacs buffer.
+buttons in an Emacs buffer.
@code{push-button} is the command that a user uses to actually `push'
a button, and is bound by default in the button itself to @key{RET}
HCoop / bpt / emacs.git / blobdiff