Re: gtk+2.8.x and cairo

[Kurt Miller <kurt intricatesoftware com>]

On Wednesday 14 December 2005 04:32 pm, Owen Taylor wrote:
> On Wed, 2005-12-14 at 14:26 -0500, Kurt Miller wrote:
> > Hi,
> >
> > There is a rather significant cairo bug that can cause all gtk+2
> > based apps to sefault upon startup in some X server setups. The
> > problem can be seen across archs (sparc/sparc64/macppc/i386) and
> > OS's and seems to be easist to reproduce when the X server is at
> > Depth 8.
> >
> > I know this is a cairo bug, but it effects all gtk+2.8.x based
> > applications when a machine happens to be configured such that the
> > bug it hit. In some cases it is not possible to configure the X
> > server to avoid the bug, so it makes all gtk+2 apps not useable.
> >
> > I'm writing this list in an attempt to raise awareness of the bug.
> >
> > https://bugs.freedesktop.org/show_bug.cgi?id=4505
>
> I'd basically consider GTK+-2.8 to require something better than 8pp;
> I know there are people who love to get new software running on
> ancient hardware, but PseudoColor really is a different and complex
> world. Getting PseudoColor support working reasonably was one of the
> most time-consuming parts of GTK+-0.9x development.
>
> (And the CPU that goes along with that vintage of hardware is going
> to perform pretty badly for Cairo ...)

I understand that ancient hardware will not be supported forever. In my 
particular case I'm seeing the problem on a < 1 year old PowerBook G4 
which is currenly stuck at Depth 8.

> That being said, it really shouldn't segfault; but it's not something
> within what the scope of the Cairo developers test on or can support
> themselves.

I've updated the bug report with instructions on how to reproduce on any 
platform / driver combination. It should be easy for anyone to 
reproduce now.

> If you catch up with Keith Packard on #cairo, I think he 
> had some ideas about how PseudoColor could be supported in cairo
> without causing excessive complexity to leak into the normal code.
>
> If the issue is 8/24 hardware defaulting to 8bpp, then it might make
> sense to have some environment variable or XSetting to make the GTK+
> default visual the GdkRGB visual rather than the system visual.

It seems the best possible solution at this time is for gtk+2 to detect 
when PseudoColor is the default and switch to TrueColor as Mark 
Kettenis suggested. Perhaps you could comment on the feasablity of that 
solution?

-Kurt