[cairo] cairo_win32_surface_create api change

[Stuart Parmenter]

This fixes trap-clip, but not self-copy.

stuart

On 12/7/05, Owen Taylor <otaylor at redhat.com> wrote:
> On Mon, 2005-12-05 at 12:16 -0800, Stuart Parmenter wrote:
> > On 12/2/05, Owen Taylor <otaylor at redhat.com> wrote:
> > > On Thu, 2005-12-01 at 14:54 -0800, Stuart Parmenter wrote:
> > > > Here is my patch.
> > > >
> > > > The things "set up so that the width/height *are not* necessary" are
> > > > broken it turns out.  You are using the clipbox as the width/height of
> > > > the surface which will almost always be wrong if you're using
> > > > clipping. Backend functions such as get_extents need to actually
> > > > return the proper values for things to work.  Both of these tests hit
> > > > code paths that use get_extents after setting the clip region to null
> > > > resulting in a 0,0,0,0 return from get_extents which ends up clipping
> > > > out lots of stuff, which isn't really what you want.
> > >
> > > Without an actual description of the code paths that aren't working,
> > > it's hard for me to propose the correct fix, but the extents of a
> > > DIB or DDB are determinable without extra API and on general grounds
> > > having a drawing operation depend on the extents of a window almost
> > > certainly indicates that something is wrong.
> > >
> > > Regards,
> > >                                                 Owen
> >
> >
> > I noticed that I only sent this to Owen previously.  Resending to list.
> >
> > Run the tests I said previously and put some break points in
> > _cairo_win32_surface_get_extents and then see what happens when you
> > get 0,0,0,0 returned.  Or simply grep for cairo_surface_get_extents
> > and look at all the callers.
>
> I spent some time tracking down the problem with trap-clip.c on win32,
> and it wasn't really related to the win32 code at all.
>
> Note that _cairo_surface_get_extents() is possibly dependent
> on the clip ... this has always been the case and was intended to be
> the case, though it isn't entirely clear from the function docs.
>
> All the code calling _cairo_surface_get_extents() expects this, but the
> problem is that the call in _cairo_clip_intersect_mask() is calling
> _cairo_surface_get_extents() on a surface *where the clip isn't
> up-to-date*. We actually set the clip on the surface lazily ... and
> only update it before actually drawing. The clip in trap-clip.c ends
> up being a clip from a previous grid square and has no intersection
> with the current code.
>
> Adding this updating code in cairo_gstate_clip() as in the attached
> patch fixes the problem, but might exact an unnecessary performance
> penalty. It might be better to do it instead in
> _cairo_clip_intersect_mask() right before calling get_extents().
>
> The issue in self-copy may be entirely different ... I haven't looked
> at it.
>
> Regards,
>                                         Owen
>
>
>
>