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layout_2020: Use ArcRefCell to track hoisted fragments

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This avoids the use of lookup tables for containing blocks when
constructing the stacking context tree.

This seems to catch some laid-out hoisted fragments that were otherwise
dropped in the previous design. The changes cause one new test to pass
and one to fail. Visual examination of the failing tests reveals that
it's a progression (list markers are appearing when they were previously
not rendered).
This commit is contained in:
Martin Robinson 2020-03-25 16:32:33 +01:00
parent ebaa73ddcd
commit 19f4b708b3
8 changed files with 105 additions and 157 deletions
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93
components/layout_2020/display_list/stacking_context.rs
View file

@ -9,10 +9,8 @@ use crate::fragments::{
AbsoluteOrFixedPositionedFragment, AnonymousFragment, BoxFragment, Fragment,
};
use crate::geom::PhysicalRect;
use crate::positioned::HoistedFragmentId;
use crate::style_ext::ComputedValuesExt;
use euclid::default::Rect;
use fnv::FnvHashMap;
use gfx_traits::{combine_id_with_fragment_type, FragmentType};
use servo_arc::Arc as ServoArc;
use std::cmp::Ordering;
@ -37,30 +35,13 @@ pub(crate) struct ContainingBlock {
/// The physical rect of this containing block.
rect: PhysicalRect<Length>,
/// Fragments for positioned descendants (including direct children) that were
/// hoisted into this containing block. They have hashed based on the
/// HoistedFragmentId that is generated during hoisting.
hoisted_children: FnvHashMap<HoistedFragmentId, ArcRefCell<Fragment>>,
}
impl ContainingBlock {
pub(crate) fn new(
rect: &PhysicalRect<Length>,
space_and_clip: wr::SpaceAndClipInfo,
children: &[ArcRefCell<Fragment>],
) -> Self {
let mut hoisted_children = FnvHashMap::default();
for child in children {
if let Some(hoisted_fragment_id) = child.borrow().hoisted_fragment_id() {
hoisted_children.insert(*hoisted_fragment_id, child.clone());
}
}
pub(crate) fn new(rect: &PhysicalRect<Length>, space_and_clip: wr::SpaceAndClipInfo) -> Self {
ContainingBlock {
space_and_clip,
rect: *rect,
hoisted_children,
}
}
}
@ -333,12 +314,14 @@ impl Fragment {
stacking_context: &mut StackingContext,
mode: StackingContextBuildMode,
) {
if mode == StackingContextBuildMode::SkipHoisted && self.is_hoisted() {
return;
}
match self {
Fragment::Box(fragment) => {
if mode == StackingContextBuildMode::SkipHoisted &&
fragment.style.clone_position().is_absolutely_positioned()
{
return;
}
fragment.build_stacking_context_tree(
fragment_ref,
builder,
@ -417,7 +400,7 @@ impl BoxFragment {
}
let new_containing_block =
ContainingBlock::new(padding_rect, builder.current_space_and_clip, &self.children);
ContainingBlock::new(padding_rect, builder.current_space_and_clip);
if self
.style
@ -750,37 +733,39 @@ impl AbsoluteOrFixedPositionedFragment {
containing_block_info: &ContainingBlockInfo,
stacking_context: &mut StackingContext,
) {
let mut build_for_containing_block = |containing_block: &ContainingBlock| {
let hoisted_child = match containing_block.hoisted_children.get(&self.0) {
Some(hoisted_child) => hoisted_child,
None => return false,
};
builder.clipping_and_scrolling_scope(|builder| {
let mut new_containing_block_info = containing_block_info.clone();
new_containing_block_info.rect = containing_block.rect;
builder.current_space_and_clip = containing_block.space_and_clip;
hoisted_child.borrow().build_stacking_context_tree(
hoisted_child,
builder,
&new_containing_block_info,
stacking_context,
StackingContextBuildMode::IncludeHoisted,
);
});
return true;
let hoisted_fragment = self.hoisted_fragment.borrow();
let fragment_ref = match hoisted_fragment.as_ref() {
Some(fragment_ref) => fragment_ref,
None => {
warn!("Found hoisted box with missing fragment.");
return;
},
};
if let Some(containing_block) = containing_block_info.nearest_containing_block.as_ref() {
if build_for_containing_block(containing_block) {
return;
}
}
let containing_block = match self.position {
ComputedPosition::Fixed => &containing_block_info.containing_block_for_all_descendants,
ComputedPosition::Absolute => containing_block_info
.nearest_containing_block
.as_ref()
.unwrap_or(&containing_block_info.containing_block_for_all_descendants),
ComputedPosition::Static | ComputedPosition::Relative => unreachable!(
"Found an AbsoluteOrFixedPositionedFragment for a \
non-absolutely or fixed position fragment."
),
};
if !build_for_containing_block(&containing_block_info.containing_block_for_all_descendants)
{
warn!("Could not find containing block of hoisted positioned child!");
}
builder.clipping_and_scrolling_scope(|builder| {
let mut new_containing_block_info = containing_block_info.clone();
new_containing_block_info.rect = containing_block.rect;
builder.current_space_and_clip = containing_block.space_and_clip;
fragment_ref.borrow().build_stacking_context_tree(
fragment_ref,
builder,
&new_containing_block_info,
stacking_context,
StackingContextBuildMode::IncludeHoisted,
);
});
}
}