Re: [PATCH] Delayed loading of image libraries

[Miles Bader <miles@lsi.nec.co.jp>]

Juanma Barranquero <jmbarranquero@wke.es> writes:

> On Fri, 02 Jul 2004 16:56:51 +0900
> Miles Bader <miles@lsi.nec.co.jp> wrote:
>
>> I have no particular opinion about which exact function does it, but it
>> _should_ be done `transparently' -- that is any place where a lisp value
>> is used to compute deeper information (for display or otherwise).
>
> If it is done transparently, what to do when the image type is not
> available?  You're worried about the case where you write an image and
> load it afterwards on the same Emacs, but in the general case, you can
> write an (image) lisp value with one Emacs and load it with another
> (which could not support the type).  What's the expected behaviour at
> that point?

That seems obvious -- just don't display it.

> If my reading of the code is right, when lookup_image_type returns NULL
> anything can happen.

If lookup_image_type returns null, at least valid_image_p should return
0 (after my change), and many places use that as a guard.  Perhaps there
are more places checks should be inserted -- but inserting such checks
seems like the right thing to do.

-Miles
-- 
Is it true that nothing can be known?  If so how do we know this?  -Woody Allen