Re: Problems with expose_event->region patch

[Sven Neumann <sven gimp org>]

Hi,

Alexander Larsson <alla lysator liu se> writes:

> On 7 Mar 2001, Owen Taylor wrote:
> 
> > At least with backing store, I don't follow this. Only the region
> > is copied from the back buffer to the screen, so painting outside
> > the region doesn't matter. There is an implicit clip to the region
> > passed to gtk_window_begin_paint().
> >
> > (Have you changed gtk_main_do_event to call gtk_window_begin_paint_region?
> > Now that you have the region in the expose?)
> 
> No, i must have missed this. I'm not very good at the backing store stuff,
> and i don't think many are. Have you written any docs on that?
> 
> When i made this change everything works just perfect.

Well, as expected it seems to work just fine for the backing-store-case
but breaks redrawing if backing store is not available (or implemented
differently).

> > For the non-backing-store case we could even add a
> > gdk_drawable_set_clip_region() call and emulate it by changing the
> > GC's clips, though that could be rather inefficient without a
> > lot of complexity.

I'm now trying to fix redrawing in the DirectFB port (which does a
much simplified version of backing store in the hardware, not using 
pixmaps). Just to assure that I got the principle correct:

The region as passed to gdk_window_begin_paint_region() is supposed to 
be a list of rectangles all following clearing and drawing operations 
have to be clipped to until gdk_window_end_paint() is called? If this
is assured all clearing and redrawing should work correctly. Is this 
correct?


Salut, Sven