compiz - Apr 2007 - GWD button drawing prob-- any Cairo pro have insights?

Since I first tried nVidia's AIGLX with Compiz I've been seeing some
pretty
consistent drawing problems on GWD's minimize and maximize buttons on hover.
It looks like part of the fill is drawn with low alpha.  I haven't been able
to
duplicate it when using Xgl...  Here's a quick vid of what I'm seeing:
http://s154.photobucket.com/albums/s273/m1kecook/Compiz/?action=view&current=gwd-button-prob.flv

The following patch seems to work around the problem (but only if I set the
alpha less than 1.0):
--- gtk/window-decorator/gtk-window-decorator.c
+++ gtk/window-decorator/gtk-window-decorator.c
@@ -943,7 +943,7 @@ button_state_paint (cairo_t   *cr,
        cairo_stroke_preserve (cr);

        if (state & IN_EVENT_WINDOW)
-           cairo_set_source_rgb (cr, 1.0, 1.0, 1.0);
+           cairo_set_source_rgba (cr, 1.0, 1.0, 1.0, 0.99);
        else
            cairo_set_source_rgba (cr, color->r, color->g, color->b,
0.95);


I'm not proficient enough with Cairo to know if this is a bug there, with
nVidia's driver, or something in GWD or somewhere else.  Anyone have
insights?

...MC

I think that happens because of how cairo maps coordinates. You have to shift
some coordinates by 0.5px
depending on the line width. The first question here explains it better than i
can:
http://cairographics.org/FAQ ( btw, i guess i'm a 'pixels are little
squares' person :) )

I already had a patch for that somewhere, I'll bring it up to date and post
it.

Mike Cook wrote:
> Since I first tried nVidia's AIGLX with Compiz I've been seeing
some pretty
> consistent drawing problems on GWD's minimize and maximize buttons on
hover.
> It looks like part of the fill is drawn with low alpha.  I haven't been
able to
> duplicate it when using Xgl...  Here's a quick vid of what I'm
seeing:
>
http://s154.photobucket.com/albums/s273/m1kecook/Compiz/?action=view&current=gwd-button-prob.flv
> 
> The following patch seems to work around the problem (but only if I set the
> alpha less than 1.0):
> --- gtk/window-decorator/gtk-window-decorator.c
> +++ gtk/window-decorator/gtk-window-decorator.c
> @@ -943,7 +943,7 @@ button_state_paint (cairo_t   *cr,
>         cairo_stroke_preserve (cr);
> 
>         if (state & IN_EVENT_WINDOW)
> -           cairo_set_source_rgb (cr, 1.0, 1.0, 1.0);
> +           cairo_set_source_rgba (cr, 1.0, 1.0, 1.0, 0.99);
>         else
>             cairo_set_source_rgba (cr, color->r, color->g,
color->b, 0.95);
> 
> 
> I'm not proficient enough with Cairo to know if this is a bug there,
with
> nVidia's driver, or something in GWD or somewhere else.  Anyone have
insights?
> 
> ...MC
> _______________________________________________
> compiz mailing list
> compiz@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/compiz
>

This patch should fix it. It seems to work good here.
The x-shift is not really necessary, but the close button looks a little sharper
that way.
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On Sat, 2007-04-07 at 20:46 -0600, Mike Cook wrote:
> Since I first tried nVidia's AIGLX with Compiz I've been seeing
some pretty
> consistent drawing problems on GWD's minimize and maximize buttons on
hover.
> It looks like part of the fill is drawn with low alpha.  I haven't been
able to
> duplicate it when using Xgl...  Here's a quick vid of what I'm
seeing:
>
http://s154.photobucket.com/albums/s273/m1kecook/Compiz/?action=view&current=gwd-button-prob.flv
> 
> The following patch seems to work around the problem (but only if I set the
> alpha less than 1.0):
> --- gtk/window-decorator/gtk-window-decorator.c
> +++ gtk/window-decorator/gtk-window-decorator.c
> @@ -943,7 +943,7 @@ button_state_paint (cairo_t   *cr,
>         cairo_stroke_preserve (cr);
> 
>         if (state & IN_EVENT_WINDOW)
> -           cairo_set_source_rgb (cr, 1.0, 1.0, 1.0);
> +           cairo_set_source_rgba (cr, 1.0, 1.0, 1.0, 0.99);
>         else
>             cairo_set_source_rgba (cr, color->r, color->g,
color->b, 0.95);
> 
> 
> I'm not proficient enough with Cairo to know if this is a bug there,
with
> nVidia's driver, or something in GWD or somewhere else.  Anyone have
insights?
Seems very much like an X server issue to me.

- David