Image Cache
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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.
When an image is looked up in the cache, its specification is
compared with cached image specifications using `equal'. This means
that all images with equal specifications share the same image in the
cache.
- Variable: image-cache-eviction-delay
This variable specifies the number of seconds an image can remain
in the cache without being displayed. When an image is not
displayed for this length of time, Emacs removes it from the image
cache.
If the value is `nil', Emacs does not remove images from the cache
except when you explicitly clear it. This mode can be useful for
debugging.
- Function: clear-image-cache &optional frame
This function clears the image cache. If FRAME is non-`nil', only
the cache for that frame is cleared. Otherwise all frames' caches
are cleared.