Geometric (GPU-less) picking
Redesign picking to avoid using the GPU. Previously picking involved several GPU operations per mouse movement, but now the GPU/GL isn't used at all.
It's probably not obvious but by avoiding OpenGL and the graphics driver we also reduce CPU usage. Despite reimplementing the logic on the CPU, it still takes less CPU time than going through GL did. According to two sources (below) this branch reduces the CPU usage of cursor movement by 37.5%.