[cairo] rsvg and cairo alpha puzzle

Carl Worth cworth at cworth.org
Fri Nov 30 10:24:52 PST 2007


On Fri, 30 Nov 2007 19:16:11 +0100, Bertram Felgenhauer wrote:
> That's my code. The thing that probably goes wrong is the fiddling
> with device offsets that is done in rsvg_handle_render_cairo_sub():
...
> Apparently with a push_group in effect changing the device offsets
> like this does not affect the rendering to the group.

Yeah. The whole device_offset thing is fairly messy. We invented it
for a very specific purpose for GTK+, and then we've started using it
here and there. You're using it here in librsvg and the cairo group
code also uses it---and apparently those two uses are conflicting.

Maybe the rule should be that if you didn't create the surface
yourself, you shouldn't be messing with the device offset.

> I'll work on a patch to fix this properly in rsvg, and hopefully
> have code to show by the end of the weekend.

That sounds great.

> Is there already a bug report about this?

There's what I posted to the librsvg mailing list, which should be a
fairly good bug report. But I don't know that anyone has shoved
anything into bugzilla yet.

-Carl
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