This patch begins the support for the 'view-box' attribute that can be
attached to <svg>'s.
The FormattingContext determines the size of the Element according to
the specified 'width' and 'height' or if they are not given by the
'viewbox' or by the bounding box of the path if nothing is specified.
When we try to paint a SVG Path that belongs to a <svg> that has the
'view-box' and a specified 'height'/'width', all the parts of the path
get scaled/moved accordingly.
There probably are many edge cases and bugs still to be found, but this
is a nice start. :^)
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.
The purpose of this new object will be to keep track of various states
during an ongoing layout.
Until now, we've been updating layout tree nodes as we go during layout,
which adds an invisible layer of implicit serialization to the whole
layout system.
My idea with FormattingState is that running layout will produce a
result entirely contained within the FormattingState object. At the end
of layout, it can then be applied to the layout tree, or simply queried
for some metrics we were trying to determine.
When doing subtree layouts to determine intrinsic sizes, we will
eventually be able to clone the current FormattingState, and run the
subtree layout in isolation, opening up opportunities for parallelism.
This first patch doesn't go very far though, it merely adds the object
as a skeleton class, and makes sure the root BFC has one. :^)
This makes the selected-in-the-inspector outline appear in the right
place. We take the stroke-width into account when producing the
bounding box, which makes the fit nice and snug. :^)
This property represents the CSS content size, so let's reduce ambiguity
by using the spec terminology.
We also bring a bunch of related functions along for the ride.
Instead of trying to layout SVG boxes as if they are regular CSS boxes,
let's invent an "SVG formatting context" and let it manage SVG boxes.
To facilitate this, Layout::SVGBox no longer inherits from ReplacedBox,
and is instead a simple, "inline-block" style BlockBox.
