Chromium Fragment Items: Storage, Lifecycle, and Memory Architecture

These sources explain the technical implementation and storage of Fragment Items within Google’s Blink rendering engine. They clarify that while line boxes exist as nodes in the fragment tree, the actual content of an inline formatting context is stored as a flattened list for improved performance. These FragmentItems are not kept in a separate map but are tail-allocated directly within the memory of the owning PhysicalBoxFragment. This architectural choice facilitates faster operations for painting, hit testing, and selection by providing a pre-order traversal model. The documents also detail the layout lifecycle, illustrating how logical line items are converted into physical coordinates and linked back to their original LayoutObjects. Finally, the text highlights how this system supports incremental layout reuse and handles complex scenarios like block fragmentation.