Specifies a rectangle with one corner at (x1,y1), and with width given by x2, or h if
if x2 is null, and with height given by y2, or by v if y2 is null.
If a function has been specified using startEdit(), and neither
finishEdit() nor cancelEdit have been called, then this method
will discard the current data in and replace it with data from
the edit function.