Looks pretty good, but there are some things that I would consider changing.
I am not an expert in GTK theming by any measure, however, so my suggestions might be pure insanity. I just took a look at how some other widgets are doing things.
One comment in general: do we really need to query the title widget to find out the borders that will be drawn on the toplevel? Something seems wrong here. I would have expected that we can query this information directly from the window itself in some way (and avoid the ugly hacks about assuming zeros).
Looks pretty good, but there are some things that I would consider changing.
I am not an expert in GTK theming by any measure, however, so my suggestions might be pure insanity. I just took a look at how some other widgets are doing things.
One comment in general: do we really need to query the title widget to find out the borders that will be drawn on the toplevel? Something seems wrong here. I would have expected that we can query this information directly from the window itself in some way (and avoid the ugly hacks about assuming zeros).