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Rework CB management during stacking context tree construction

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Manage containing blocks and WebRender SpaceAndClip during stacking
context tree constuction using the ContainingBlockInfo data structure.
This will allow us to reuse this data structure whenever we traverse the
fragment tree. In addition, StackingContextBuilder is no longer
necessary at all. This change also fixes some bugs where fixed position
fragments were not placed in the correct spatial node. Unfortunately,
these fixes are difficult to test because of #29659.
This commit is contained in:
Martin Robinson 2023-04-21 15:19:14 +02:00
parent 0cffe557c2
commit 0c13fcb9f2
10 changed files with 466 additions and 322 deletions
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68
components/layout_2020/flow/root.rs
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@ -6,7 +6,6 @@ use crate::cell::ArcRefCell;
use crate::context::LayoutContext;
use crate::display_list::stacking_context::{
ContainingBlock, ContainingBlockInfo, StackingContext, StackingContextBuildMode,
StackingContextBuilder,
};
use crate::dom_traversal::{iter_child_nodes, Contents, NodeAndStyleInfo, NodeExt};
use crate::element_data::LayoutBox;
@ -40,6 +39,7 @@ use style::properties::ComputedValues;
use style::selector_parser::PseudoElement;
use style::values::computed::Length;
use style_traits::CSSPixel;
use webrender_api::{ClipId, SpaceAndClipInfo, SpatialId};
#[derive(Serialize)]
pub struct BoxTree {
@ -386,30 +386,7 @@ impl BoxTree {
impl FragmentTree {
pub fn build_display_list(&self, builder: &mut crate::display_list::DisplayListBuilder) {
let mut stacking_context = StackingContext::create_root(&builder.wr);
{
let mut stacking_context_builder = StackingContextBuilder::new(&mut builder.wr);
let containing_block_info = ContainingBlockInfo {
rect: self.initial_containing_block,
nearest_containing_block: None,
containing_block_for_all_descendants: ContainingBlock::new(
&self.initial_containing_block,
stacking_context_builder.current_space_and_clip,
),
};
for fragment in &self.root_fragments {
fragment.borrow().build_stacking_context_tree(
fragment,
&mut stacking_context_builder,
&containing_block_info,
&mut stacking_context,
StackingContextBuildMode::SkipHoisted,
);
}
}
stacking_context.sort();
let stacking_context = self.build_stacking_context_tree(builder);
// Paint the canvas’ background (if any) before/under everything else
stacking_context.build_canvas_background_display_list(
@ -421,6 +398,47 @@ impl FragmentTree {
stacking_context.build_display_list(builder);
}
fn build_stacking_context_tree(
&self,
builder: &mut crate::display_list::DisplayListBuilder,
) -> StackingContext {
let mut stacking_context = StackingContext::create_root(&builder.wr);
let pipeline_id = builder.wr.pipeline_id;
let cb_for_non_fixed_descendants = ContainingBlock::new(
&self.initial_containing_block,
SpaceAndClipInfo::root_scroll(pipeline_id),
);
let cb_for_fixed_descendants = ContainingBlock::new(
&self.initial_containing_block,
SpaceAndClipInfo {
spatial_id: SpatialId::root_reference_frame(pipeline_id),
clip_id: ClipId::root(pipeline_id),
},
);
for fragment in &self.root_fragments {
fragment.borrow().build_stacking_context_tree(
fragment,
&mut builder.wr,
// We need to specify all three containing blocks here, because absolute
// descdendants of the root cannot share the containing block we specify
// for fixed descendants. In this case, they need to have the spatial
// id of the root scroll frame, whereas fixed descendants need the
// spatial id of the root reference frame so that they do not scroll with
// page content.
&ContainingBlockInfo {
for_non_absolute_descendants: &cb_for_non_fixed_descendants,
for_absolute_descendants: Some(&cb_for_non_fixed_descendants),
for_absolute_and_fixed_descendants: &cb_for_fixed_descendants,
},
&mut stacking_context,
StackingContextBuildMode::SkipHoisted,
);
}
stacking_context.sort();
stacking_context
}
pub fn print(&self) {
let mut print_tree = PrintTree::new("Fragment Tree".to_string());
for fragment in &self.root_fragments {