When attempting to start a GTK application with a Solaris X server,
we get the following cairo error:
Error: Cairo does not yet support the requested image format:
        Depth: 8
        Alpha mask: 0x00000000
        Red   mask: 0x00000000
        Green mask: 0x00000000
        Blue  mask: 0x00000000
Please file an enhacement request (quoting the above) at:
http://bugs.freedesktop.org/enter_bug.cgi?product=cairo
cairo-image-surface.c:155: failed assertion `NOT_REACHED'
Abort (core dumped)

I assume this is because the Solaris XServer has a default
PseudoColor visual. The visual entry from xdpyinfo:
  default visual id:  0x20
  visual:
    visual id:    0x20
    class:    PseudoColor
    depth:    8 planes
    available colormap entries:    256
    red, green, blue masks:    0x0, 0x0, 0x0
    significant bits in color specification:    8 bits

I'm not the most knowlegeable X person, so maybe there is
a way to I could request a different visual that would
be supported by cairo? I tried forcing CAIRO_FORMAT_RGB24
in this case just to see what would happen but still get a core dump.