Vincent Hamm
Xcode11 and ios13 added support for metal simulator.
Here is a quick and dirty patch to enable it. Pretty early and only tested on a few samples for now. Required mostly to enable metal support on correct version of ios, generate simulator compatible shaders and enforce buffer alignments on simulator (same as osx).
- Use a single buffer for various non-changing constants accessed by the GPU, instead of multiple buffers.
- Do the half-pixel offset for points and lines using a transform matrix so we don't need a malloc when rendering.
- Don't add a half-pixel offset for other primitives and textures. This matches D3D and GL render behaviour.
- Remove the half-texel texture coordinate offset since it's not needed now that there's no more half-pixel position offset when rendering a texture.
- Don't try to set texture usage on iOS 8 since it doesn't exist there.
