[cairo] cairo-xlib-surface.c:402: _swap_ximage_to_native:Assertion `NOT_REACHED' failed.

[Daniel Amelang]

On 11/19/06, Erik Ohrnberger <Erik at echohome.org> wrote:
> > -----Original Message-----
> > From: cairo-bounces at cairographics.org
> > [mailto:cairo-bounces at cairographics.org] On Behalf Of Daniel Amelang
> > Sent: Sunday, November 19, 2006 11:10 PM
> > To: Vladimir Vukicevic
> > Cc: cairo at cairographics.org; Erik at 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 at pobox.com> wrote:
> > > ----- Daniel Amelang <daniel.amelang at gmail.com> wrote:
> > > > On 11/18/06, Erik Ohrnberger <Erik at 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