This patch adds a map of Layout::Node to FormattingState::NodeState.
Instead of updating layout nodes incrementally as layout progresses
through the formatting contexts, all updates are now written to the
corresponding NodeState instead.
At the end of layout, FormattingState::commit() is called, which
transfers all the values from the NodeState objects to the Node.
This will soon allow us to perform completely non-destructive layouts
which don't affect the tree.
Note that there are many imperfections here, and still many places
where we assign to the NodeState, but later read directly from the Node
instead. I'm just committing at this stage to make subsequent diffs
easier to understand.
Here's roughly how this works:
- InlineLevelIterator keeps a nesting stack of inline-level nodes with
box model metrics.
- When entering a node with box model metrics, we add them to the
current "leading metrics".
- When exiting a node with box model metrics, we add them to the
current "trailing metrics".
- Pending leading metrics are consumed by the first fragment added
to the line.
- Pending trailing metrics are consumed by the last fragment added
to the line.
Like before, the position of a line box fragment is the top left of its
content box. However, fragments are placed horizontally along the line
with space inserted for padding and border.
InlineNode::paint() now expands the content rect as appropriate when
painting background and borders.
Note that margins and margin collapsing is not yet implemented.
This makes the eyes on ACID2 horizontally centered. :^)
This is poorly factored. TextNode needs to know whether the most
recently inserted fragment on the current line was empty or ended in
whitespace. This is used when deciding what to do with leading
whitespace in text nodes.
Let's keep this working for now, but we should eventually sort this out
and make text chunk iteration not depend on this information.
When collapsing whitespace, we can skip over all-whitespace chunks at
the start of each line, and immediately following fragments that
themselves end in whitespace.
This patch adds a new mechanism that allows InlineFormattingContext to
build line boxes incrementally instead of all-in-one go.
Incremental build will eventually allow much better support for CSS
floating objects.
