- Calling nextDrawable may result in a nil drawable, or a drawable with no
pixel format. Attempt several times to retrieve a drawable with a valid
pixel format, and if unsuccessful, return an error from vkQueuePresentKHR()
and vkAcquireNextImageKHR(), to force swapchain to be re-created.
- Reorganize MVKQueuePresentSurfaceSubmission::execute() to detect drawable
with invalid format, attach MTLCommandBuffer completion handler just before
commit, and delay enqueuing MTLCommandBuffer until commit.
- Refactor mvkOSVersionIsAtLeast() for clarity (unrelated).
7fe4963985