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Layout: refactor the box tree update logic for better readability (#37390)
Refactor the box tree update logic to improve readability and facilitate the addition of incremental update logic in the following PRs. Testing: No logic changed, just covered by existing WPT tests Fixes: Nothing to fix Signed-off-by: sharpshooter_pt <ibluegalaxy_taoj@163.com>
This commit is contained in:
JoeDow
GitHub
parent
6818d5c600
commit
5159529888
1 changed files with 191 additions and 162 deletions
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@ -125,168 +125,11 @@ impl BoxTree {
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/// * how intrinsic content sizes are computed eagerly makes it hard
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/// to update those sizes for ancestors of the node from which we
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/// made an incremental update.
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pub fn update(context: &LayoutContext, mut dirty_node: ServoLayoutNode<'_>) -> bool {
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#[allow(clippy::enum_variant_names)]
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enum UpdatePoint {
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AbsolutelyPositionedBlockLevelBox(ArcRefCell<BlockLevelBox>),
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AbsolutelyPositionedInlineLevelBox(ArcRefCell<InlineItem>, usize),
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AbsolutelyPositionedFlexLevelBox(ArcRefCell<FlexLevelBox>),
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AbsolutelyPositionedTaffyLevelBox(ArcRefCell<TaffyItemBox>),
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}
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fn update_point(
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node: ServoLayoutNode<'_>,
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) -> Option<(Arc<ComputedValues>, DisplayInside, UpdatePoint)> {
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if !node.is_element() {
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return None;
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}
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if node.type_id() == LayoutNodeType::Element(LayoutElementType::HTMLBodyElement) {
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// This can require changes to the canvas background.
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return None;
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}
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// Don't update unstyled nodes or nodes that have pseudo-elements.
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let element_data = node.style_data()?.element_data.borrow();
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if !element_data.styles.pseudos.is_empty() {
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return None;
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}
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let layout_data = NodeExt::layout_data(&node)?;
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if layout_data.pseudo_before_box.borrow().is_some() {
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return None;
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}
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if layout_data.pseudo_after_box.borrow().is_some() {
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return None;
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}
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let primary_style = element_data.styles.primary();
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let box_style = primary_style.get_box();
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if !box_style.position.is_absolutely_positioned() {
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return None;
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}
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let display_inside = match Display::from(box_style.display) {
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Display::GeneratingBox(DisplayGeneratingBox::OutsideInside { inside, .. }) => {
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inside
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},
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_ => return None,
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};
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let update_point =
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match &*AtomicRef::filter_map(layout_data.self_box.borrow(), Option::as_ref)? {
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LayoutBox::DisplayContents(..) => return None,
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LayoutBox::BlockLevel(block_level_box) => match &*block_level_box.borrow() {
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BlockLevelBox::OutOfFlowAbsolutelyPositionedBox(_)
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if box_style.position.is_absolutely_positioned() =>
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{
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UpdatePoint::AbsolutelyPositionedBlockLevelBox(block_level_box.clone())
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},
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_ => return None,
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},
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LayoutBox::InlineLevel(inline_level_items) => {
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let inline_level_box = inline_level_items.first()?;
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let InlineItem::OutOfFlowAbsolutelyPositionedBox(_, text_offset_index) =
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&*inline_level_box.borrow()
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else {
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return None;
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};
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UpdatePoint::AbsolutelyPositionedInlineLevelBox(
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inline_level_box.clone(),
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*text_offset_index,
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)
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},
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LayoutBox::FlexLevel(flex_level_box) => match &*flex_level_box.borrow() {
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FlexLevelBox::OutOfFlowAbsolutelyPositionedBox(_)
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if box_style.position.is_absolutely_positioned() =>
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{
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UpdatePoint::AbsolutelyPositionedFlexLevelBox(flex_level_box.clone())
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},
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_ => return None,
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},
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LayoutBox::TableLevelBox(..) => return None,
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LayoutBox::TaffyItemBox(taffy_level_box) => match &taffy_level_box
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.borrow()
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.taffy_level_box
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{
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TaffyItemBoxInner::OutOfFlowAbsolutelyPositionedBox(_)
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if box_style.position.is_absolutely_positioned() =>
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{
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UpdatePoint::AbsolutelyPositionedTaffyLevelBox(taffy_level_box.clone())
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},
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_ => return None,
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},
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};
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Some((primary_style.clone(), display_inside, update_point))
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}
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loop {
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let Some((primary_style, display_inside, update_point)) = update_point(dirty_node)
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else {
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dirty_node = match dirty_node.parent_node() {
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Some(parent) => parent,
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None => return false,
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};
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continue;
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};
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let contents = ReplacedContents::for_element(dirty_node, context)
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.map_or_else(|| NonReplacedContents::OfElement.into(), Contents::Replaced);
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let info = NodeAndStyleInfo::new(dirty_node, Arc::clone(&primary_style));
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let out_of_flow_absolutely_positioned_box = ArcRefCell::new(
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AbsolutelyPositionedBox::construct(context, &info, display_inside, contents),
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);
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match update_point {
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UpdatePoint::AbsolutelyPositionedBlockLevelBox(block_level_box) => {
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*block_level_box.borrow_mut() = BlockLevelBox::OutOfFlowAbsolutelyPositionedBox(
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out_of_flow_absolutely_positioned_box,
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);
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},
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UpdatePoint::AbsolutelyPositionedInlineLevelBox(
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inline_level_box,
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text_offset_index,
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) => {
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*inline_level_box.borrow_mut() = InlineItem::OutOfFlowAbsolutelyPositionedBox(
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out_of_flow_absolutely_positioned_box,
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text_offset_index,
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);
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},
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UpdatePoint::AbsolutelyPositionedFlexLevelBox(flex_level_box) => {
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*flex_level_box.borrow_mut() = FlexLevelBox::OutOfFlowAbsolutelyPositionedBox(
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out_of_flow_absolutely_positioned_box,
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);
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},
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UpdatePoint::AbsolutelyPositionedTaffyLevelBox(taffy_level_box) => {
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taffy_level_box.borrow_mut().taffy_level_box =
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TaffyItemBoxInner::OutOfFlowAbsolutelyPositionedBox(
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out_of_flow_absolutely_positioned_box,
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);
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},
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}
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break;
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}
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// We are going to rebuild the box tree from the update point downward, but this update
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// point is an absolute, which means that it needs to be laid out again in the containing
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// block for absolutes, which is established by one of its ancestors. In addition,
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// absolutes, when laid out, can produce more absolutes (either fixed or absolutely
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// positioned) elements, so there may be yet more layout that has to happen in this
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// ancestor.
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//
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// We do not know which ancestor is the one that established the containing block for this
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// update point, so just invalidate the fragment cache of all ancestors, meaning that even
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// though the box tree is preserved, the fragment tree from the root to the update point and
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// all of its descendants will need to be rebuilt. This isn't as bad as it seems, because
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// siblings and siblings of ancestors of this path through the tree will still have cached
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// fragments.
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//
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// TODO: Do better. This is still a very crude way to do incremental layout.
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while let Some(parent_node) = dirty_node.parent_node() {
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parent_node.invalidate_cached_fragment();
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dirty_node = parent_node;
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}
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pub fn update(context: &LayoutContext, dirty_root_from_script: ServoLayoutNode<'_>) -> bool {
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let Some(box_tree_update) = IncrementalBoxTreeUpdate::find(dirty_root_from_script) else {
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return false;
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};
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box_tree_update.update_from_dirty_root(context);
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true
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}
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}
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@ -400,3 +243,189 @@ impl BoxTree {
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)
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}
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}
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#[allow(clippy::enum_variant_names)]
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enum DirtyRootBoxTreeNode {
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AbsolutelyPositionedBlockLevelBox(ArcRefCell<BlockLevelBox>),
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AbsolutelyPositionedInlineLevelBox(ArcRefCell<InlineItem>, usize),
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AbsolutelyPositionedFlexLevelBox(ArcRefCell<FlexLevelBox>),
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AbsolutelyPositionedTaffyLevelBox(ArcRefCell<TaffyItemBox>),
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}
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struct IncrementalBoxTreeUpdate<'dom> {
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node: ServoLayoutNode<'dom>,
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box_tree_node: DirtyRootBoxTreeNode,
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primary_style: Arc<ComputedValues>,
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display_inside: DisplayInside,
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}
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impl<'dom> IncrementalBoxTreeUpdate<'dom> {
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fn find(dirty_root_from_script: ServoLayoutNode<'dom>) -> Option<Self> {
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let mut maybe_dirty_root_node = Some(dirty_root_from_script);
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while let Some(dirty_root_node) = maybe_dirty_root_node {
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if let Some(dirty_root) = Self::new_if_valid(dirty_root_node) {
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return Some(dirty_root);
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}
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maybe_dirty_root_node = dirty_root_node.parent_node();
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}
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None
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}
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fn new_if_valid(potential_dirty_root_node: ServoLayoutNode<'dom>) -> Option<Self> {
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if !potential_dirty_root_node.is_element() {
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return None;
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}
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if potential_dirty_root_node.type_id() ==
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LayoutNodeType::Element(LayoutElementType::HTMLBodyElement)
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{
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// This can require changes to the canvas background.
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return None;
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}
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// Don't update unstyled nodes or nodes that have pseudo-elements.
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let element_data = potential_dirty_root_node
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.style_data()?
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.element_data
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.borrow();
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if !element_data.styles.pseudos.is_empty() {
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return None;
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}
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let layout_data = NodeExt::layout_data(&potential_dirty_root_node)?;
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if layout_data.pseudo_before_box.borrow().is_some() {
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return None;
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}
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if layout_data.pseudo_after_box.borrow().is_some() {
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return None;
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}
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let primary_style = element_data.styles.primary();
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let box_style = primary_style.get_box();
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if !box_style.position.is_absolutely_positioned() {
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return None;
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}
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let display_inside = match Display::from(box_style.display) {
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Display::GeneratingBox(DisplayGeneratingBox::OutsideInside { inside, .. }) => inside,
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_ => return None,
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};
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let box_tree_node =
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match &*AtomicRef::filter_map(layout_data.self_box.borrow(), Option::as_ref)? {
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LayoutBox::DisplayContents(..) => return None,
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LayoutBox::BlockLevel(block_level_box) => match &*block_level_box.borrow() {
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BlockLevelBox::OutOfFlowAbsolutelyPositionedBox(_)
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if box_style.position.is_absolutely_positioned() =>
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{
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DirtyRootBoxTreeNode::AbsolutelyPositionedBlockLevelBox(
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block_level_box.clone(),
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)
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},
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_ => return None,
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},
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LayoutBox::InlineLevel(inline_level_items) => {
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let inline_level_box = inline_level_items.first()?;
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let InlineItem::OutOfFlowAbsolutelyPositionedBox(_, text_offset_index) =
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&*inline_level_box.borrow()
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else {
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return None;
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};
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DirtyRootBoxTreeNode::AbsolutelyPositionedInlineLevelBox(
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inline_level_box.clone(),
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*text_offset_index,
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)
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},
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LayoutBox::FlexLevel(flex_level_box) => match &*flex_level_box.borrow() {
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FlexLevelBox::OutOfFlowAbsolutelyPositionedBox(_)
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if box_style.position.is_absolutely_positioned() =>
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{
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DirtyRootBoxTreeNode::AbsolutelyPositionedFlexLevelBox(
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flex_level_box.clone(),
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)
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},
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_ => return None,
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},
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LayoutBox::TableLevelBox(..) => return None,
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LayoutBox::TaffyItemBox(taffy_level_box) => {
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match &taffy_level_box.borrow().taffy_level_box {
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TaffyItemBoxInner::OutOfFlowAbsolutelyPositionedBox(_)
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if box_style.position.is_absolutely_positioned() =>
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{
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DirtyRootBoxTreeNode::AbsolutelyPositionedTaffyLevelBox(
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taffy_level_box.clone(),
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)
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},
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_ => return None,
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}
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},
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};
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Some(Self {
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node: potential_dirty_root_node,
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box_tree_node,
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primary_style: primary_style.clone(),
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display_inside,
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})
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}
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fn update_from_dirty_root(&self, context: &LayoutContext) {
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let contents = ReplacedContents::for_element(self.node, context)
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.map_or_else(|| NonReplacedContents::OfElement.into(), Contents::Replaced);
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let info = NodeAndStyleInfo::new(self.node, self.primary_style.clone());
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let out_of_flow_absolutely_positioned_box = ArcRefCell::new(
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AbsolutelyPositionedBox::construct(context, &info, self.display_inside, contents),
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);
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match &self.box_tree_node {
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DirtyRootBoxTreeNode::AbsolutelyPositionedBlockLevelBox(block_level_box) => {
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*block_level_box.borrow_mut() = BlockLevelBox::OutOfFlowAbsolutelyPositionedBox(
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out_of_flow_absolutely_positioned_box,
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);
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},
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DirtyRootBoxTreeNode::AbsolutelyPositionedInlineLevelBox(
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inline_level_box,
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text_offset_index,
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) => {
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*inline_level_box.borrow_mut() = InlineItem::OutOfFlowAbsolutelyPositionedBox(
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out_of_flow_absolutely_positioned_box,
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*text_offset_index,
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);
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},
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DirtyRootBoxTreeNode::AbsolutelyPositionedFlexLevelBox(flex_level_box) => {
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*flex_level_box.borrow_mut() = FlexLevelBox::OutOfFlowAbsolutelyPositionedBox(
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out_of_flow_absolutely_positioned_box,
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);
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},
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DirtyRootBoxTreeNode::AbsolutelyPositionedTaffyLevelBox(taffy_level_box) => {
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taffy_level_box.borrow_mut().taffy_level_box =
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TaffyItemBoxInner::OutOfFlowAbsolutelyPositionedBox(
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out_of_flow_absolutely_positioned_box,
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);
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},
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}
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// We are going to rebuild the box tree from the update point downward, but this update
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// point is an absolute, which means that it needs to be laid out again in the containing
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// block for absolutes, which is established by one of its ancestors. In addition,
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// absolutes, when laid out, can produce more absolutes (either fixed or absolutely
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// positioned) elements, so there may be yet more layout that has to happen in this
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// ancestor.
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//
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// We do not know which ancestor is the one that established the containing block for this
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// update point, so just invalidate the fragment cache of all ancestors, meaning that even
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// though the box tree is preserved, the fragment tree from the root to the update point and
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// all of its descendants will need to be rebuilt. This isn't as bad as it seems, because
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// siblings and siblings of ancestors of this path through the tree will still have cached
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// fragments.
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//
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// TODO: Do better. This is still a very crude way to do incremental layout.
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let mut invalidate_start_point = self.node;
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while let Some(parent_node) = invalidate_start_point.parent_node() {
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parent_node.invalidate_cached_fragment();
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invalidate_start_point = parent_node;
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}
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}
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}
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