Issue caused by inconsistency in GPUFramebuffer viewport state
between Metal and OpenGL. The MTLFramebuffer code has been
modified such that framebuffer viewport/scissor state is retained
and only updated if attachments are modified during bind.
This is consistent with OpenGL. Previously, other updates to the
framebuffer in Metal would reset the viewport region, especially
if attachments were temporarily removed. This caused the color
picker selection to be misaligned.
Authored by Apple: Michael Parkin-White
Michael Parkin-White