[cairo] Firefox/Gtk3 - possible cairo clipping bug

[Martin Stransky]

Hi folks,

I work on Firefox Gtk3 port and there's a strange bug [1][2]. It looks 
like in some case cairo_clip() does not work. The code is from 
_gtk_theming_background_paint_color() [3] and looks like:

_gtk_rounded_box_path (&clip_box, cr);
cairo_clip (cr);
gdk_cairo_set_source_rgba (cr, &bg->bg_color);
cairo_paint (cr);

_gtk_rounded_box_path creates a rounded box for gtk_entry element. When 
the code is called from a simple testcase, cairo_clip() works and the 
cairo_paint() is clipped by the area, i.e. gtkEntry background is rendered.

When tha same code is called from Firefox, cairo_clip() does not take 
effect and whole surface is filled by the color.

Do you guys have an idea where should I look at? Any debugging hints?

Thanks,
ma.


[1] https://bugzilla.gnome.org/show_bug.cgi?id=694086
[2] https://bugzilla.mozilla.org/show_bug.cgi?id=877606
[3] 
https://github.com/jdapena/gtk/blob/master/gtk/gtkthemingbackground.c#L139