WIP. Most of the GPU-side work should be done (though it's not tested
end-to-end and it's certainly possible I missed something), but still
needs work on encoding side.
Move types into the toplevel and hide implementation details. Remove
deref of hub CmdBuf to mux. Restrict public visibility of internals.
Most items have some docs, though improvements are still possible. In
particular, there should be detailed safety info.
Add workgroup size to dispatch call (needed by metal). Change all fence
references to mutable for consistency.
Move backend traits to a separate file (move them out of the toplevel
namespace in preparation for the hub types going there, to make the
public API nicer).
Add a method and macro for automatically choosing shader code, and
change collatz example to generate all 3 kinds on build.
Make the hub abstraction connect to the mux, rather than directly to the
Vulkan back-end.
As of this commit, both command line and winit examples work (on
Vulkan). In theory it should be possible to get them working on Dx12 as
well by translating the shader code, but there's a lot that can go
wrong.
This commit also contains a bunch of changes to mux to make conditional
compilation of match arms work, and new methods to support swapchain.
Adds a new "mux" module which can have multiple backends. As of this
commit, it's not wired up at all, but the functionality should be
reasonably complete.
Minor tweaks to the backend trait to accommodate this, mostly changing
Fence and Semaphore to references so they don't need to be Copy.
Part of the work toward #95
Adds an example binary that can be run with `cargo apk`.
One thing that will still need manual tuning (for now) is the size of
the canvas. A good followup is to sense that from the window size.
