Fix event handling on QGLBackend
Clip drawn elements
Persist and reuse drawing elements
Fix persistence of graphics state
Add text rendering based on vispy text visual
Move clear call where it belongs
Distribute draw calls
Remove unused import
Persist rendering elements for better performance
Use an actual transform matrix for graphics context ctm
Fix text size by adapting to projection size
Add rotation to graphics context
Minor refactor of text rendering
Hack text extent code so that it sort of works