Enhance/modernize painting API #3
Description
There are several issues with current painting API:
- drawing line of more than 1 pixel is extremely slow using raster API
- Off screen rendering with currently OpenGL implies to copy back textures from GPU to CPU which is expensive on Mac (likely Windows too)
- OpenGL rendering is done in the main thread, could moving to a dedicated thread improve performances?
- OpenGL is deprecated on Mac (for a long time), is a custom Metal painter an option on Mac?
- Qt has introduced QRhi, could it be used in NeoQCP?