Yet another reason window pictures suck

[Soeren Sandmann]

Chris Wilson <chris at chris-wilson.co.uk> writes:

> On Fri, 21 May 2010 11:44:39 -0400, Adam Jackson <ajax at redhat.com> wrote:
> > Context:
> > 
> > https://bugzilla.redhat.com/show_bug.cgi?id=533879
> > 
> > If you've got a 24bpp framebuffer, you poor misguided soul you, then you
> > have a conundrum.  Pixmaps are 32bpp but Windows aren't.  Suppose you
> > make a Picture out of a Window.  You would think you'd be required to
> > use one of the Formats with an associated Visual.  What does the spec
> > say about it?
> > 
> [...]
> > 
> > b) Fix the spec to be more strict, and fix cairo and whoever else to be
> > more careful about picking Visual Formats for Window Pictures.
> 
> The bad news here is that the XRenderFormat chosen (for
> cairo_xlib_surface_create_with_xrender_format()) is entirely the
> responsibility of the application. Visuals are mapped to XRenderFormats
> using the mapping supplied by RenderQueryPictFormats. Cairo itself
> only creates [ax]rgb32 (and a8) pixmaps. So we would need to teach the
> toolkits to handle 24bpp Windows.
> 
> The implementation should be fixed though, let's return BadMatch and
> stop this silent corruption.

Is it actually silent corruption? pixman will explode spectactularly
if you give it a format that it doesn't know about.

Isn't the problem just that render advertises a bogus format that some
applications will then make use of?


Søren