Stacking contexts are sorted after building a tree of them. They are
sorted by z-index first, DOM tree order second.
Sorting was previously *very* slow on pages with many stacking contexts.
That was because the sort() function used Node::is_before() in the
quick_sort comparator to see if one StackingContext was before another.
is_before() does tree traversal and can take quite a long time per call.
This patch avoids all that by letting StackingContext know its index
among all StackingContexts within the same document in tree order.
There's a noticeable snappiness increase on the CSS-FLEXBOX-1 spec page,
for instance. :^)
It returns a PaintableBox (a PaintableWithLines, to be specific), not a
'PaintBox'. paintable_box() without the cast is already available
through BlockContainer's Box base class, we don't need to shadow it.
The name "initial containing block" was wrong for this, as it doesn't
correspond to the HTML element, and that's specifically what it's
supposed to do! :^)
2023-02-28 12:21:56 +01:00
Renamed from Userland/Libraries/LibWeb/Layout/InitialContainingBlock.cpp (Browse further)
