bug#68006: 30.0.50; Image-mode speed

[Manuel Giraud via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

Eli Zaretskii <eliz@gnu.org> writes:

[...]

>> -    ;; Discard any stale image data before looking it up again.
>> -    (image-flush image)
>> +    (if image-mode-eager-cache-flush
>> +        ;; Discard any stale image data before looking it up again.
>> +        (image-flush image)
>> +      ;; Add a content based hash into image spec to be sure that the
>> +      ;; cache is updated should the on disk image change.
>> +      (when (and filename (file-exists-p filename))
>> +        (setq image (append image (list :hash (image-contents-sha1 filename))))))
>> +
>
> I'm probably missing something: how would this assure that if the
> image file is replaced, we re-read it from disk?

The logic goes like this:

    - I compute a new hash of the content on disk
    - This hash is add to the spec
    - Now a key in the image cache is computed for this spec
      (i.e. filename, size and *hash* included)
    - If the hash was changed the cache will miss and read the new image
      content.  If hash and size had not changed the cache will hit and
      return the correct image.

Is it more clear?  Or maybe I do not answer your question?

I'll try to address your other remarks in a new version of this patch.
-- 
Manuel Giraud