This patch implements the "remove irrelevant boxes" and "generate
missing child wrappers" parts of table fixup.
"Generate missing parents" is left as a task for our future selves.
Various whitespace-related issues have been fixed, and support for the
different CSS white-space values is improved enough that I think we can
stop doing the hack where we just prune whitespace nodes from the tree
and actually let them show up.
This is a nice step forward for correctness with the slight downside of
cluttering up layout tree dumps with tons of whitespace text nodes.
But hey, that's the web we know & love. :^)
Fixes#4427.
The StyleResolver can find the specified CSS values for the parent
element via the DOM. Forcing everyone to locate specified values for
their parent was completely unnecessary.
Layout nodes now only carry CSS computer values with them. The main
idea here is to give them only what they need to perform layout, and
leave the rest back in the DOM.
Just because an inline-block is inline doesn't mean it's ready to
accept random inline children. If it's a block, we may need to create
an anonymous wrapper first.
Fixes#4604.
We were incorrectly hoisting non-inline children of inline-block boxes
to the nearest non-inline ancestor.
Since inline-block boxes are only inline on the *outside*, it's fine
for them to have non-inline children.
Eventually we should clarify these relationships by making the inside
and outside display types more explicit.
We can now build partial layout trees (this happens for example when an
element's "display" property is programmatically toggled from "none" to
something else.)
We can't say that "no replaced boxes can have children", since that
breaks SVG. Instead, let each LayoutNode decide whether it's allowed
to have children.
Fixes#4223.
We were messing up the box tree for tables by hoisting cells up to
become children of the table row group (instead of the table row.)
Table rows are non-block boxes, and it's fine for them to have cell
(block) children.
Fixes#4225.
Inline layout nodes cannot have block children (except inline-block,
of course.)
When encountering a block box child of an inline, we now hoist the
block up to the inline's containing block, and also wrap any preceding
inline siblings in an anonymous wrapper block.
This improves the ACID2 situation quite a bit (although we still need
floats to really bring it home.)
I also took this opportunity to move all tree building logic into
Layout::TreeBuilder, to continue the theme of absolving our LayoutNode
objects of responsibilities. :^)
