Instead of computing it on the fly while painting each layout node,
they now remember their selection state. This avoids a whole bunch
of tree traversal while painting with anything selected.
You can now cycle through focusable elements (currently only hyperlinks
are focusable) with the Tab key.
The focus outline is rendered in a new FocusOutline paint phase.
The text cursor follows slightly different "intuitive" rules than the
regular hit testing. Clicking past the right edge of a text box should
still "hit" the text box, and place the cursor at its end, for example.
We solve this by adding a HitTestType enum that is passed to hit_test()
and determines whether past-the-edge candidates are considered.
This works everywhere right now, but it's obviously not going to stay
that way forever. :^)
Note that this does not advance the cursor correctly for whitespace
since the cursor is DOM-based and doesn't take whitespace collapsing
into account yet.
Each Web::Frame now has a cursor that sits at a DOM::Position. It will
blink and look like a nice regular text cursor.
It doesn't really do anything yet, but it will eventually.
