This means all the antiailasing is done inside the fragment shader. We use a Signed Distance Field to draw the 2D rounded boxes. This ensure the best quality for AA. This reduce the averge Batch for widget to 16 verts instead of ~600 and reduce overshading a lot. Theme Emboss alpha and tria alpha needs to be changed after this refactor. The shadow drawing is left unchanged and still use geometry. Reviewed By: Severin Differential Revision: https://developer.blender.org/D7833