Skia with dawn

[sudo]

Hi, I'm a bit confused about how to use skia (M117) with dawn.

Passing only skia_use_dawn=true and trying to compile gives me this message:

ninja: error: obj/third_party/externals/dawn/src/dawn/native/webgpu_dawn_static.ninja:13: multiple rules generate obj/BUILD_DIR/gen/third_party/externals/dawn/src/dawn/native/webgpu_dawn.webgpu_dawn_native_proc.obj [-w dupbuild=err]

ninja: Entering directory `out/Static'

Any help would be appreciated.

[John Stiles]

Try invoking ninja like this:

    ninja -C out/Static -w dupbuild=warn

I also see the "multiple rules" message when I build Dawn, so that's normal. On my computer, it's a warning, not an error, and in practice it hasn't caused any issues (yet?). I'm not sure why you are seeing an error instead, but `-w dupbuild=warn` should let you ignore it.

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[sudo]

Thanks for your reply!

It seems like I at some point have moved depot_tools without updating PATH, and so a newer version of ninja got used instead. Now with PATH updated I also just get a warning and it compiles fine.

The new issue is creating the device needed by

`skgpu::graphite::ContextFactory::MakeDawn(...)`

First I try creating an instance:

`auto instance = wgpu::CreateInstance(); // program crashes`

```

// dawn_proc.c

// wgpu::CreateInstance calls this function

WGPUInstance wgpuCreateInstance(WGPUInstanceDescriptor const * descriptor) {

    return procs.createInstance(descriptor); // everything in procs is null and crash happens here
}

```

Any ideas what I'm doing wrong?

Also, judging by the recent commits, I take that M117 is the last version with dawn backend in ganesh?

[John Stiles]

Just searching the code, it looks like other places which do this first call `dawnProcSetProcs(&native::GetProcs());`.

Take a look: https://source.chromium.org/chromium/chromium/src/+/main:third_party/dawn/src/dawn/tests/end2end/WindowSurfaceTests.cpp;l=56;drc=681f1eff1c06b5c88aa41b662308f869155caa2d

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[sudo]

Nice, that worked, I followed this example just to confirm that something can be drawn and shown on screen.

So, this is where I'm at now using skia graphite:

I've created an SkSurface and want to render to screen.

How would I go about doing that?

[John Stiles]

That's a broad question. I would recommend looking at the built-in Viewer app that we ship with Skia. For instance, start with the GraphiteDawnWindowContext class (in tools/window) and set some breakpoints; see how it's used and where it's called.

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