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LibWeb: Prune old paintable pointers from layout tree after relayout

When text paintables shift around in the tree due to line wrapping,
we may end up in a situation where some text node does not generate
a paintable (due to being all whitespace, for example), even though
in the previous layout pass, it *did* generate a paintable.

To prevent holding on to old paintables in such cases, we now do a
pass in LayoutState::commit() where we explicitly detach all old
paintables from the layout tree.
This commit is contained in:
Andreas Kling 2023-08-29 16:27:16 +02:00
parent 390da2985f
commit 6d7a2f5cc9
3 changed files with 48 additions and 0 deletions

View file

@ -218,6 +218,14 @@ void LayoutState::commit(Box& root)
// Only the top-level LayoutState should ever be committed.
VERIFY(!m_parent);
// NOTE: In case this is a relayout of an existing tree, we start by detaching the old paint tree
// from the layout tree. This is done to ensure that we don't end up with any old-tree pointers
// when text paintables shift around in the tree.
root.for_each_in_inclusive_subtree_of_type<Layout::TextNode>([&](Layout::TextNode& text_node) {
text_node.set_paintable(nullptr);
return IterationDecision::Continue;
});
HashTable<Layout::TextNode*> text_nodes;
Vector<Painting::PaintableWithLines&> paintables_with_lines;