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Code Issues Releases Activity

(Image Cache): Document image-refresh.

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Chong Yidong 2007-08-07 16:43:16 +00:00
parent a607dc9298
commit 108af9594b
1 changed files with 36 additions and 12 deletions
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lispref/display.texi
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@ -4281,13 +4281,43 @@ cache, it can always be displayed, even if the value of
@subsection Image Cache
@cindex image cache
Emacs stores images in an image cache when it displays them, so it can
display them again more efficiently. It removes an image from the cache
when it hasn't been displayed for a specified period of time.
Emacs stores images in an image cache so that it can display them
again more efficiently. When Emacs displays an image, it searches the
image cache for an existing image specification @code{equal} to the
desired specification. If a match is found, the image is displayed
from the cache; otherwise, Emacs loads the image normally.
When an image is looked up in the cache, its specification is compared
with cached image specifications using @code{equal}. This means that
all images with equal specifications share the same image in the cache.
Occasionally, you may need to tell Emacs to refresh the images
associated with a given image specification. For example, suppose you
display an image using a specification that contains a @code{:file}
property. The image is loaded from the given file and stored in the
image cache. If you later display the image again, using the same
image specification, the image is displayed from the image cache.
Normally, this is not a problem. However, if the image file has
changed in the meantime, Emacs would be displaying the old version of
the image. In such a situation, it is necessary to ``refresh'' the
image using @code{image-refresh}.
@defun image-refresh spec &optional frame
This function refreshes any images having image specifications
@code{equal} to @var{spec} on frame @var{frame}. If @var{frame} is
@code{nil}, the selected frame is used. If @var{frame} is @code{t},
the refresh is applied to all existing frames.
This works by removing all image with image specifications matching
@var{spec} from the image cache. Thus, the next time the image is
displayed, Emacs will load the image again.
@end defun
@defun clear-image-cache &optional frame
This function clears the entire image cache. If @var{frame} is
non-@code{nil}, only the cache for that frame is cleared. Otherwise,
all frames' caches are cleared.
@end defun
If an image in the image cache has not been displayed for a specified
period of time, Emacs removes it from the cache and frees the
associated memory.
@defvar image-cache-eviction-delay
This variable specifies the number of seconds an image can remain in the
@ -4299,12 +4329,6 @@ except when you explicitly clear it. This mode can be useful for
debugging.
@end defvar
@defun clear-image-cache &optional frame
This function clears the image cache. If @var{frame} is non-@code{nil},
only the cache for that frame is cleared. Otherwise all frames' caches
are cleared.
@end defun
@node Buttons
@section Buttons
@cindex buttons in buffers