Re: [PATCH] Delayed loading of image libraries

[David Kastrup <dak@gnu.org>]

Juanma Barranquero <jmbarranquero@wke.es> writes:

> On 02 Jul 2004 09:10:55 +0200
> David Kastrup <dak@gnu.org> wrote:
> 
> > It is
> > not fine if an Emacs supporting PNG does not display a PNG.
> 
> Sure.  But currently, an Emacs supporting PNG *will* display a PNG if
> the library is made available (either statically or dynamically).  Miles
> thinks (or so I understand) that the responsability of making the
> library available rests on lookup_image_type.  I believe the proper
> thing to do is, at some point, calling `image-type-available-p'.

The way I understand this, the responsibility of making the library
available rests on the display code.  If I put the stuff into a
display property I saved just verbatim (without even taking a look at
what image formats would be in it), then after restarting an Emacs
session and restoring the display property, the PNG should display.
No calls to lookup_image_type or image-type-available-p or whatever
else by the user should be required.

> > > After loading, Emacs *must* ask at a moment or other whether the
> > > image type is available, mustn't it?
> > 
> > How about when displaying it?
> 
> And is not exactly that what I propose?

If it is, I have failed to get it.  It sounded to me like you were
proposing that the user has to something before the image cn be
displayed.

> > Why should image-type-available-p have been called?
> 
> Because, AFAICS, is the only documented way to know whether a given
> image type is supported.

What if a program does not care because it simply assumes that the
configuration is correct?  If a particular format is not supported,
we currently just get boxes.  That's ok.  It is not ok if we just get
boxes even _when_ a particular format is supported.

-- 
David Kastrup, Kriemhildstr. 15, 44793 Bochum