bug#40845: SVG rendering issues

[Alan Third]

On Fri, May 15, 2020 at 11:40:53PM +0200, Alan Third wrote:
> 
> Take as long as you need, I'm in no great hurry. I still need to work
> out how to calculate whether I should be using the mouse face and
> decide exactly how to handle flushing an image from the cache as
> it's somewhat broken in that patch.

I still don't know how to use the mouse face. I couldn't see any way
to detect if it's in use when we first load the image in xdisp.c.

Most likely I've missed something, but if not then I worry that the
easiest fix may be to actually support transparency when we draw to
the screen instead of generating background colours when we load the
images. I suspect we do it the way we do because it would have been
slow on older machines, but modern machines should be able to handle
it quickly via XRender and friends.

As for the cache I decided to just delete all images that match the
image spec, no matter what colours they use. It seems to me to be the
safest option, as we don't want users flushing an image from the
cache to display an updated version, only for the old one to reappear
when the face changes.
-- 
Alan Third

0001-Set-basic-SVG-attributes-bug-40845.patch
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