This commit adds timestamps to compute pass boundaries for command style timer queries on metal.
It also updates the code in piet-gpu/stages, piet-gpu/lib.rs and tests/ to use the new ComputePass type.
The one that takes T is more useful than the one that takes references
to T. When specialization lands, we will be able to have both under the
`extend` name.
This patch includes a number of changes to encourage reading and writing
buffers through mapping rather than copying data as before.
This includes a new `BufWrite` abstraction which is designed for filling
buffers. It behaves much like a Vec<u8>, but with fixed capacity.
There's a bit of reorganizing as well. Shader stages are made available
from piet-gpu to the test rig, config is now a proper structure
(marshaled with bytemuck).
This commit just has the transform stage, which is a simple monoid scan
of affine transforms.
Progress toward #119
Reduce allocation of descriptor heaps. This change also enables clearing
of buffers, as the handles are needed at command dispatch time.
Also updates the tests to use clear_buffers on DX12. Looking forward to
being able to get rid of the compute shader workaround on Metal.
This is a followup on #125, and progress toward #95
Use an array of bindtypes rather than the previous situation, which was
a choice of buffer counts, or a heavier builder pattern.
The main thing this unlocks is distinguishing between readonly and
read/write buffers, which is important for DX12.
This is WIP, the Metal part hasn't been done, and the old stuff not
deleted.
Part of #125
Have a structured way of gathering test results, rather than the
existing ad hoc approach of just printing stuff.
The details are still pretty primitive, but there's room to grow.
