Ensure reference frame is popped in layout 2020
closes: #26066
Should be equivalent to https://github.com/servo/servo/pull/26063 for layout2020
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layout_2020: Stop throwing away hoisted boxes in nested absolutes
We were previously throwing away some boxes hoisted to containing blocks
for all descendants when they were contained by absolutes. This prevents
panics in existing web platform tests that would otherwise be triggered
by the addition of the `unreachable!` statement.
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We were previously throwing away some boxes hoisted to containing blocks
for all descendants when they were contained by absolutes. This prevents
panics in existing web platform tests that would otherwise be triggered
by the addition of the `unreachable!` statement.
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).
layout_2020: Use ArcRefCell in the fragment tree
This will allow mutability which is useful for things like animations.
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Partial text decoration support for layout 2020
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix#25166
- [X] There are tests for these changes
When calculating scrolling overflow calculation we cannot currently use
the actual containing block in all cases. This change increases the
amount that we do use the containing block.
layout_2020: Fix a documentation comment
I inadvertently failed to complete this doc comment.
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Add support for tracking containing blocks when doing inline layout.
This requires setting up a PositioningContext for inline boxes when
necessary. Instead of using the PositioningContext helper methods
and we reuse the contexts between line breaks.
Fixes#25279.
Add a few helper methods which allow removing duplicate code in
PositioningContext. These methods will also be used to properly
implement hoisting in inline layout.
Instead of painting hoisted position fragments in the order to which
they are hoisted, paint them in tree order and properly incorporate them
into the stacking context.
We do this by creating a placeholder fragment in the original tree position
of hoisted fragments. The ghost fragment contains an atomic id which
links back to the hoisted fragment in the containing block.
While building the stacking context, we keep track of containing blocks
and their children. When encountering a placeholder fragment we look at
the containing block's hoisted children in order to properly paint the
hoisted fragment.
One notable design modification in this change is that hoisted fragments
no longer need an AnonymousFragment as their parent. Instead they are
now direct children of the fragment that establishes their containing block.
