Added support so that you can
create new foreignObjects, manipulate
existing ones, and edit their content.
No itex support. You need to use MathML
in there. But it's a start ...
They are now selectable, draggable, resizable
and rotatable.
The MathML content behave strangely when you
resize, but snaps back to its correct size when
you let go of the mouse.
(Resizing the MathML involves changing the font-size
on the containing foreignObject. No interface for
that, yet.)
