Compositor Scheduler Lifecycle: Commit and Invalidation Coalescing

What this episode covers

These sources explain the lifecycle management of rendering trees within the Chromium compositor (cc), focusing on how the scheduler handles requests for updates. A core principle established is that the system strictly enforces one pending tree at a time, meaning any request to create a new tree—whether via a main-thread commit or an impl-side invalidation—must wait if a tree is currently being rasterized. The text describes the step-by-step pipeline for both update types, detailing how incoming requests are queued as state flags when the slot is occupied. When the slot frees up, the scheduler’s priority rules usually favor the main-thread commit, and any outstanding impl-side invalidation is merged or coalesced into that commit action to prevent redundant tree creation. The overall goal is to ensure sequential, non-concurrent execution of tree-building actions.

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