Struct Compositor 

pub struct Compositor { /* private fields */ }

Receives committed frames from the view thread and produces CompositorFrame for the GPU.

Owns a copy of the scroll tree + offsets so it can handle wheel events at vsync rate without waiting for the view thread.

Implementations

impl Compositor

pub fn new() -> Self

pub fn commit( &mut self, display_list: Arc<DisplayList>, layer_tree: LayerTree, scroll_tree: ScrollTree, )

Accept a committed frame from the view thread.

Chrome: LayerTreeHostImpl::FinishCommit().

Updates the display list, layer tree, and scroll tree topology. Scroll offsets are not accepted — the compositor owns them exclusively and syncs them to the view thread via ScrollSync.

pub fn try_scroll(&mut self, target: u32, delta: Offset) -> bool

Handle a scroll event directly — no view thread round-trip.

Chrome: InputHandlerProxy::RouteToTypeSpecificHandler().

pub fn produce_frame(&self) -> Option<CompositorFrame>

Produce a frame for the GPU.

The scroll offsets are passed directly — the renderer uses them to override tagged scroll transforms. Zero allocation, O(1) lookup.

pub fn scroll_offsets(&self) -> &ScrollOffsets

Current scroll offsets — for syncing back to the view thread.

pub fn scroll_tree(&self) -> &ScrollTree

pub fn has_content(&self) -> bool

pub fn hit_test_scroll_target(&self, point: Point) -> Option<u32>

Find the deepest scrollable layer at a screen point.

Chrome: InputHandler::HitTestScrollNode() — compositor-side hit test against the layer tree to determine which scrollable container should receive the scroll delta. Returns the DOM node ID of the scroll target.

Walks the layer tree depth-first, checking bounds. Returns the deepest scrollable layer whose bounds contain the point. Falls back to root_scroller() if no scrollable layer is hit.