layout: Split overflow calculation after fragment tree construction (#37203)

Instead of computing scrollable overflow while constructing the fragment
tree, we will now do it later. In the future this will also allow to
only recalculate the overflow without rebuilding the tree when transform
properties change, but that's left for a follow-up.

Stylo PR: https://github.com/servo/stylo/pull/194

Testing: One test is now passing (more investigation is needed), but
otherwise this isn't expected to have any effect.

Signed-off-by: Oriol Brufau <obrufau@igalia.com>
Co-authored-by: Martin Robinson <mrobinson@igalia.com>
This commit is contained in:
Oriol Brufau 2025-05-30 21:41:05 +02:00 committed by GitHub
parent 079198c898
commit de2da3b1e1
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11 changed files with 148 additions and 96 deletions

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@ -29,7 +29,7 @@ use crate::flow::inline::InlineItem;
use crate::flow::{BlockContainer, BlockFormattingContext, BlockLevelBox};
use crate::formatting_contexts::IndependentFormattingContext;
use crate::fragment_tree::FragmentTree;
use crate::geom::{LogicalVec2, PhysicalRect, PhysicalSize};
use crate::geom::{LogicalVec2, PhysicalSize};
use crate::positioned::{AbsolutelyPositionedBox, PositioningContext};
use crate::replaced::ReplacedContents;
use crate::style_ext::{Display, DisplayGeneratingBox, DisplayInside};
@ -392,31 +392,9 @@ impl BoxTree {
&mut root_fragments,
);
let scrollable_overflow = root_fragments
.iter()
.fold(PhysicalRect::zero(), |acc, child| {
let child_overflow = child.scrollable_overflow_for_parent();
// https://drafts.csswg.org/css-overflow/#scrolling-direction
// We want to clip scrollable overflow on box-start and inline-start
// sides of the scroll container.
//
// FIXME(mrobinson, bug 25564): This should take into account writing
// mode.
let child_overflow = PhysicalRect::new(
euclid::Point2D::zero(),
euclid::Size2D::new(
child_overflow.size.width + child_overflow.origin.x,
child_overflow.size.height + child_overflow.origin.y,
),
);
acc.union(&child_overflow)
});
FragmentTree::new(
layout_context,
root_fragments,
scrollable_overflow,
physical_containing_block,
self.viewport_scroll_sensitivity,
)