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layout: Switch display list building from bottom-up to top-down.

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This eliminates a lot of allocations and O(n^2) behavior.
This commit is contained in:
Patrick Walton 2016-03-02 15:41:50 -08:00
parent f4b95dd00b
commit d3d2dd05f2
5 changed files with 35 additions and 58 deletions
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26
components/layout/traversal.rs
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@ -215,23 +215,27 @@ impl<'a> PreorderFlowTraversal for ComputeAbsolutePositions<'a> {
}
}
#[derive(Copy, Clone)]
pub struct BuildDisplayList<'a> {
pub layout_context: &'a LayoutContext<'a>,
pub state: DisplayListBuildState<'a>,
}
impl<'a> PostorderFlowTraversal for BuildDisplayList<'a> {
impl<'a> BuildDisplayList<'a> {
#[inline]
fn process(&self, flow: &mut Flow) {
let mut state = DisplayListBuildState::new(
self.layout_context, flow::base(flow).stacking_context_id);
flow.build_display_list(&mut state);
flow::mut_base(flow).display_list_building_result = Some(state.items);
flow::mut_base(flow).restyle_damage.remove(REPAINT);
pub fn traverse(&mut self, flow: &mut Flow) {
if self.should_process() {
self.state.push_stacking_context_id(flow::base(flow).stacking_context_id);
flow.build_display_list(&mut self.state);
flow::mut_base(flow).restyle_damage.remove(REPAINT);
self.state.pop_stacking_context_id();
}
for kid in flow::child_iter(flow) {
self.traverse(kid);
}
}
#[inline]
fn should_process(&self, _: &mut Flow) -> bool {
self.layout_context.shared_context().goal == ReflowGoal::ForDisplay
fn should_process(&self) -> bool {
self.state.layout_context.shared_context().goal == ReflowGoal::ForDisplay
}
}