We need to reduce the number of buffer bindings to 8 so it can run on
all WebGPU devices. The best candidate was to combine info and bin_data,
which are written by two different stages (draw_leaf and binning,
respectively), both read by coarse, and are unstructured, so the only
real shader change needed is to add the offset for the binning data.
I thought I was going to have to do a blit to make it fit, but
fortunately that wasn't needed.
Progress to #202
* add comment for ClipInp::path_ix
* update comment for SceneBuilder drawtags
* remove copy of blend data through info buffer. Instead, update EndClip's DrawMonoid::scene_offset to point to the same scene data of the associated EndClip.
* Add comment about avoiding NaNs to inverse alpha divisions
* Change inverse alpha computations to use max(a, epsilon) rather than +
* Emit alpha component in blit fragment shader (enables support for partially transparent windows)
A number of things weren't being computed correctly for strokes,
including bounding boxes and also incorrectly applying y_edge logic
(which is only correct for fills).
* add writeable image support to engine
* add external resources to engine
* update fine to output to a texture
* copy over original piet-gpu test scenes
* put it all in a pretty (resizable!) window
Now that wgsl-analyzer 0.6 is released, most explicit type annotations on vec can be dropped (the exception being when it is a type conversion).
Also changes mix to select when the selector is actually boolean.
As stated by the README, the intention is for the shaders to be
provided under the terms of the Unlicense in addition to the MIT
and Apache-2.0 licenses.
While here, add a self-contained UNLICENSE file to replace the
external reference to unlicense.org.
This is a checkpoint of partly completed work. Much of the GPU side is done, very little of the CPU side.
For clips, the clip_els bindings (binding 6 of draw_leaf) are not added. Clip logic is missing from coarse. The overflow buffer is missing from fine, as is its size calculation in coarse (but it should work as long as the max depth fits within BLEND_STACK_SPLIT).
For gradients, the texture binding is missing (binding 6) is missing from fine, as is the infrastructure in engine to deal with texture resources, and of course porting over the logic to fill it.
The code is not tested, bugs may lurk.
Note that this is evidence in favor of https://github.com/gfx-rs/naga/issues/2098 - my code is actually wrong, and it was caught by trying to port it to run in Chrome Canary.
All streams of the scene are combined into a single buffer. This is very much like existing piet-gpu, however the various outputs from the compute stages (whether computed on CPU or GPU) will retain their separate bindings, which is more native to WGSL.
There's a touch of ergonomics loss, in particular when we do transforms we'll need to unmarshal them by hand, but I think overall not too bad.
The bones of coarse rasterization are in place (so far, fills only). Still not suitable for end-to-end (need to generate bounding boxes, among other things), but getting closer.
This lets us use https://github.com/wgsl-analyzer/wgsl-analyzer for writing the wgsl files.
The imports (for wgsl-analyzer) have to be machine specific at the moment - to use this you need to configure .vscode/settings.json yourself. The alternative is to point them at static files on GitHub, which is tempting to make things easier, but would potentially go out of sync with what is actually used.
