Remove Drawing

[danirabbit]

Fixes #567

• BufferSurface is only used in Gala
• RoundedRectangle is only being used in Gala and to mask images (which we can do natively in Gtk now with overflow)
• average_color () is already copied in the places it's used
• Granite.Color is only used in Gala as well

[JoseExposito]

This functions would need to be migrated to Gala, right?

I think that Gala should avoid GTK (in reference to your comment about overflow) and stick to its drawing API.

[davidmhewitt]

Agreed, this shouldn't be merged until Gala has replacements or else the daily builds/installs will break as these methods will go missing from the shared library.

And yes, when adding things to Gala, GTK should be avoided. There's already issues with the GTK code in Gala that's preventing the Wayland transition.

Edit: Revised my comment above, since gala still depends on granite, not granite-7. We split the libraries when we moved to GTK4 for exactly this reason. So it should be fine to remove this now.

[danirabbit]

Sorry for being unclear. What I meant regarding rounded rectangle was that in our Gtk components we can use overflow, so the only place this is actually used is in Gala. I didn't mean to imply we could use Gtk drawing in Gala, only that this function isn't useful outside of Gala anymore