Gtk theme engine

[Simon Steinbeiß]

Hey Peter,

with respect to the engine, I'd go for 1). The checkboxes are drawn with svg or png assets in most Gtk3 themes, including Adwaita, I'm pretty png doesn't load (much) slower than cairo draws something as complex as a checkbox.

If you ask me, we can leave creating themes to themers. As has been elaborated many times, creating themes for Gtk3 is laborious (mostly because of the versioning). If for 4.14 new contributors propose themes for Gtk3 that we like, we can always include them. But personally, I wouldn't put that on the roadmap as an item. But yeah, there's still lots of time to discuss and think about 4.14 ;)

Cheers
Simon