This is a first (huge) step towards modernizing the layout architecture
and bringing it closer to spec language.
Layout is now performed by a stack of formatting contexts, operating on
the box tree (or layout tree, if you will.)
There are currently three types of formatting context:
- BlockFormattingContext (BFC)
- InlineFormattingContext (IFC)
- TableFormattingContext (TFC)
Document::layout() creates the initial BlockFormattingContext (BFC)
which lays out the initial containing block (ICB), and then we recurse
through the tree, creating BFC, IFC or TFC as appropriate and handing
over control at the context boundaries.
The majority of this patch is just refactoring the old logic spread out
in LayoutBlock and LayoutTableRowGroup, and turning into these context
classes instead. A lot more cleanup will be needed.
There are many architectural wins here, the main one being that layout
is no longer performed by boxes themselves, which gives us much greater
flexibility in the outer/inner layout of a given box.
Const pointers into the DOM was a nice idea, but in practice, there are
too many situations where the layout tree wants to some non-const thing
to the DOM.
LibWeb keeps growing and the Web namespace is filling up fast.
Let's put DOM stuff into Web::DOM, just like we already started doing
with SVG stuff in Web::SVG.
To make this possible, I also had to give each LayoutNode a Document&
so it can resolve document-specific colors correctly. There's probably
ways to avoid having this extra member by resolving colors later, but
this works for now.
Table row layout is now split into two phases:
1. Compute all the column widths (even taking colspan into account!)
2. Place all cells at the correct x,y offsets based on column widths.
Both phases visit all rows and all cells.
