The RasterInvalidator Pipeline and Lifecycle in Blink

The provided sources describe the role and function of the RasterInvalidator within the Blink rendering engine's lifecycle. Positioned as the final step of the painting process, this component acts as a per-layer diff engine that identifies which specific pixels of a composited layer require re-rasterization. It operates during the paint-to-compositor handoff, comparing new paint artifacts against previous snapshots to calculate damage after the document has reached a clean paint state. By determining the symmetric difference between old and new display items and chunks, it provides the compositor with precise damage rectangles via the SetNeedsDisplayRect API. This mechanism ensures rendering efficiency by allowing the system to refresh only changed regions rather than entire layers. Ultimately, the documentation distinguishes this process from the PrePaint phase, noting that while PrePaint decides what must be repainted, the RasterInvalidator determines what must be rerasterized at the compositor level.