Re: Image cache

[Stefan Monnier <monnier@iro.umontreal.ca>]

> OTOH, I don't see why I should change the value of image-cache-eviction-delay,
> if it is Emacs' job to update the cache when the image data changes.
> So I found that updating the image cache after visiting an new image
> was correct before the 2006-01-30 change in image-mode.el:

> 	* image-mode.el (image-toggle-display): Use file name if possible,
> 	instead of unnecessarily allocating a (possibly huge) lisp string.

> But I don't blame this change.  It is a good optimization, but it
> revealed a problem in cache processing code.  This code doesn't update
> the cache for the file name when the file contents changes.

If someone has the time, it seems it migt be worth it to do something along
the following lines:

- add `loadtime' timestamp to the image data-structure so that staleness can
  be detected and a `refresh' function in the image_type data structure
  which, given the `loadtime' image `spec' says whether to reload or not.
- provide a new function (image-refresh IMAGE-SPEC).
- make create-image (used by image-toggle-display and others) use that
  new function.


        Stefan