When running without a compositor, there is an ugly black border.
This branch fixes that by: 1) Adding an 'is_composited' argument to defaults_get_bubble_shadow_size and defaults_get_bubble_corner_radius. If we're not composited, they return 0.0f. 2) Adding a 'GdkScreen **screen' argument to defaults_get_top_corner 3) Using these throughout to check composited state wherever these are used.
Additionally, I had to add some oddness in bubble.c for _refresh_background. There is a bit of code that draws a (seemingly unnecessary) image in shadow-size-units even in the uncomposited case. But it can't use 0 because that causes a crash to create a 0-sized image. So I used 1 for that special case. Seems like it would be cleaner to avoid that path in uncomposited mode, but I didn't feel confident enough to make that change.