These sources describe the pre-paint lifecycle phase in the Chromium Blink rendering engine, a process primarily responsible for paint invalidation and building paint property trees. The mechanism is characterized as a pre-order depth-first search across the layout tree, though it must weave together frame views and physical fragments to handle complex layouts. A preliminary post-order pass handles dirty-bit propagation for frame views, while the main recursion maintains DOM order to ensure visual effects are applied correctly. The walk includes specialized logic for fragmented content and out-of-flow objects, sometimes requiring a second pass to capture descendants that do not follow standard layout hierarchy. Ultimately, this intricate traversal ensures that all visual properties and invalidation flags are accurately updated before the actual painting begins.