Peter Kim
675f38aca7
Due to the freeing and re-creation of textures performed when binding
offscreen viewports, VR viewport textures would be needlessly
re-created every drawing iteration, leading to a negative impact on VR
frame rate.
This was brought to light by 6738ecb64e, which introduced an
additional texture clear operation on initialization and was
prohibitively costly on some systems when performed every frame.
Now, the textures for VR viewports will not be always re-created
during offscreen binding, but only when necessary using a pre-drawing
step (`wm_xr_session_surface_offscreen_ensure()`).
Reviewed By: jbakker, fclem
Differential Revision: https://developer.blender.org/D14059