Bug 9102

As discussed in the mailing list:

On 11/19/06, Erik Ohrnberger <Erik@echohome.org> wrote:
> > -----Original Message-----
> > From: cairo-bounces@cairographics.org 
> > [mailto:cairo-bounces@cairographics.org] On Behalf Of Daniel Amelang
> > Sent: Sunday, November 19, 2006 11:10 PM
> > To: Vladimir Vukicevic
> > Cc: cairo@cairographics.org; Erik@echohome.org
> > Subject: Re: [cairo] cairo-xlib-surface.c:402:
> > _swap_ximage_to_native:Assertion `NOT_REACHED' failed.
> >
> > On 11/19/06, Vladimir Vukicevic <vladimir@pobox.com> wrote:
> > > ----- Daniel Amelang <daniel.amelang@gmail.com> wrote:
> > > > On 11/18/06, Erik Ohrnberger <Erik@echohome.org> wrote:
> > > > > Generally, I'm running an X Window server emulator on
> > my Windows
> > > > > PC and pipe the display up there.  The PC is set to 32
> > bit color
> > > > > depth, and when the DISLPAY env var is set to the IP of the 
> > > > > Windows PC, that is when the applications fail with this error.
> > > > >
> > > > > Is there a setting someplace on the Linux side where I
> > can force a
> > > > > similar color depth as to the Option "Pixmap" "32" you
> > mention below?
> > > > >
> > > > > Thanks for the help, I really appreciate it.
> > > >
> > > > Hmmm...your question is outside the scope of this list, as your 
> > > > problem is not cairo-related. You'll find better answers here 
> > > > (especially the cygwin-xfree part):
> > >
> > > Well, it is sort of cairo related -- these X severs /are/
> > out there (including Xvnc and various others), and having cairo 
> > assert out on them is not a good solution, IMO.
> >
> > Yea, totally agree. I was reponding to his question about cygwin/X.
> > Sorry for the confusion, I didn't mean to imply that no one is going 
> > to address the root of the problem. As I said in my first response 
> > to Erik, I think this should problem should be in bugzilla and get 
> > the proper attention.
> >
> > Dan
> >
>
> I have to admit that it's not cygwin/X, but an old program called 
> VisionWare, and has served me faithfully for a long number of years.

Ah, sorry for jumping to conclusions. Unfortunately, I have no idea how to get 
VisionWare's XVision into 32bpp mode. In fact, the following posting seems to 
say that XVision doesn't support 32bpp Pixmaps at all :(

http://www.cygwin.com/ml/cygwin-xfree/2002-04/msg00366.html

So I'm all out of ideas for workarounds. Sorry.

> Specific version information that could proove helpful:
>
> gtkmm-2.8.1, gtk+-2.6.10, cairo-0.1.6           works
> gtkmm-1.2.9-r2, gtk+-2.8.19, cairo-1.0.4        does not work

Cairo has changed so much from 0.1.6 to 1.0.4, especially in the place in xlib-
surface where the problem is. I can see the before and after code paths, but 
it doesn't help solve the problem. Thing is, libpixman in now used in places 
that previously only contained X calls. And it's pixman's lack of support for 
24bpp that is the root of the problem. At least that's my understanding.

> Should I go and put this information in bugzilla?  I'd be willing to 
> do so, but I'd have to find out where the bugzilla site is.

Here:

https://bugs.freedesktop.org/enter_bug.cgi?product=cairo

Thanks for reporting this.

Carl/whoever is listening: could a quick stopgap measure be to do a conversion 
from 24bpp to 32bpp before the image is handed over to pixman (or write a 
conversion function in pixman that cairo-xlib can call)? Ideally, one would 
want pixman to support 24bpp directly, but since that's a lot of work, and 
this isn't a common case, it might be worth considering a slow and messy 
approach. People don't call _acquire_(source|dest)_image in their display loop 
anyways, right?

Dan
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