Previously, we were handling viewBoxes/viewports in a slightly hacky
way, asking graphics elements to figure out what viewBox to use during
layout. This does not work in all cases, and can't allow for more
complex SVGs where it is possible to have nested viewports.
This commit makes the SVGFormattingContext keep track of the
viewport/boxes, and it now lays out each viewport recursively, where
each nested `<svg>` or `<symbol>` can establish a new viewport.
This fixes some previous edge cases, and starts to allow nested
viewports (there's still some issues to resolve there).
Fixes#22931
With this change, we now have ~1200 CellAllocators across both LibJS and
LibWeb in a normal WebContent instance.
This gives us a minimum heap size of 4.7 MiB in the scenario where we
only have one cell allocated per type. Of course, in practice there will
be many more of each type, so the effective overhead is quite a bit
smaller than that in practice.
I left a few types unconverted to this mechanism because I got tired of
doing this. :^)
This commit removes DeprecatedString's "null" state, and replaces all
its users with one of the following:
- A normal, empty DeprecatedString
- Optional<DeprecatedString>
Note that null states of DeprecatedFlyString/StringView/etc are *not*
affected by this commit. However, DeprecatedString::empty() is now
considered equal to a null StringView.
I'm about to make StackingContext traverse the paintable tree instead of
actually traversing the layout tree, and it turns out we were not
creating paintables for these SVG elements.
Also switch them to Layout::Box instead of the default InlineNode to
make the trees look a bit less weird. Ultimately, we should do something
specialized for these subtrees, but for now this'll do.
