Registers a block of code that Metal calls immediately after it schedules the command buffer for execution on the GPU.
Mac Catalyst 13.0+
A block of code to be invoked.
You can register multiple handlers for the same command buffer. You can’t add a schedule handler after you commit the command buffer.
The device object schedules the command buffer after it identifies any dependencies with work tasks submitted by other command buffers or other APIs in the system. During the execution of the completion handler, the command buffer status is at least MTLCommandBufferStatusScheduled.