LibWeb/WebAudio: Implement basic offline rendering loop #7611
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R-Goc
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This adds graph construction, topology ordering, and per-quantum processing based on the Web Audio rendering loop specification. A minimal set of render nodes is supported, including Destination and ConstantSource, with a fallback for unsupported node types. Does not handle audio params, scheduling, or suspend/resume logic. ConstantSource is used as a minimal probe node to validate graph wiring, ordering, and per-quantum behavior. Adds LibTest coverage exercising render graph behavior across render quanta.
Creates a minimal snapshot of the WebAudio graph to avoid accessing GC-managed AudioNode objects on the render thread. This snapshot captures the destination node, supported source nodes (ConstantSourceNode), and their connections. AudioParam connections and rendering behavior are intentionally not handled yet.
Introduce OfflineAudioRenderThread, a minimal helper for offline rendering that runs a RenderGraphDescription snapshot on a dedicated thread and writes the rendered samples into per-channel buffers. Render loop logic from spec is handled in render_a_quantum(). Adds a small unit test that verifies the thread completes and publishes a result for a constant source graph.
Connects the render-thread infrastructure to OfflineAudioContext and enables end-to-end offline rendering for simple graphs. Adds 32 passing WPT covering basic offline rendering behavior.
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This PR introduces a basic offline rendering loop to process audio for the WebAudio API, based on the work of @jonbgamble.
Description
We cannot access GC allocated objects off the main thread, so this PR creates a render thread friendly snapshot of the audio graph using
snapshot_render_graph(). This snapshot is represented as aRenderGraphDescriptionthat is then consumed byRenderGraph/RenderGraphImplto construct and process a graph ofRenderNodeson the rendering thread viaOfflineAudioRenderThread.Follows the Web Audio API rendering loop specification and adds relevant spec steps as needed.
Only implements processing for
ConstantSourceNodeto keep the scope minimal.Does not handle AudioParam processing/automation, suspend/resume, mixing, or graph updates.
Testing
TestWebAudioRenderGraph.cppto test basic quantum rendering.TestOfflineAudioRenderThread.cppto test basic helper thread API.ConstantSourceNodesand currentTime incrementing.