This sounds good! One other issue that's not being measured in your traces, which I mentioned on IRC but I should note for the record, is GTK theme drawing. The GTK theme API requires you to pass in an X drawable, so currently Gecko detects when the cairo context is a wrapper around an X drawable and the graphics state is "simple enough" (CTM is a pixel-aligned translation, operator is OVER, etc) and if so unwraps the X drawable and passes it directly to GTK. Ideally, the GTK theme API would change so we can tell a theme to draw directly into a cairo_t (since most themes are using cairo to draw already!) Until then, though, getting theme drawing to work performantly with cairo-gl would probably require GLX_EXT_texture_from_pixmap, and of course there would still be performance impact. Rob -- "He was pierced for our transgressions, he was crushed for our iniquities; the punishment that brought us peace was upon him, and by his wounds we are healed. We all, like sheep, have gone astray, each of us has turned to his own way; and the LORD has laid on him the iniquity of us all." [Isaiah 53:5-6]