As suggested by Joshua, this commit adds the 2-clause BSD license as a
comment block to the top of every source file.
For the first pass, I've just added myself for simplicity. I encourage
everyone to add themselves as copyright holders of any file they've
added or modified in some significant way. If I've added myself in
error somewhere, feel free to replace it with the appropriate copyright
holder instead.
Going forward, all new source files should include a license header.
To streamline the layout tree and remove irrelevant data from classes
that don't need it, this patch adds two new LayoutNode subclasses.
LayoutNodeWithStyleAndBoxModelMetrics should be inherited by any layout
node that cares about box model metrics (margin, border, and padding.)
LayoutBox should be inherited by any layout node that can have a rect.
This makes LayoutText significantly smaller (from 140 to 40 bytes) and
clarifies a lot of things about the layout tree.
I'm also adding next_sibling() and previous_sibling() overloads to
LayoutBlock that return a LayoutBlock*. This is okay since blocks only
ever have block siblings.
Do also note that the semantics of is<T> slightly change in this patch:
is<T>(nullptr) now returns true, to facilitate allowing to<T>(nullptr).
The <br> element will produce a special LayoutBreak node in the layout
tree, which forces a break in the line layout whenever encountered.
This patch also makes LayoutBlock use the current line-height as the
minimum effective height for each line box. This ensures that having
multiple <br> elements in a row doesn't create 0-height line boxes.
