overwrite(destwin, [sminrow, smincol, dminrow, dmincol, dmaxrow,
dmaxcol])
Overwrite the window on top of destwin.
The windows need not be the same size, in which case only the
overlapping region is copied. This copy is destructive, which means
that the current background character overwrites the old contents of
destwin.
To get fine-grained control over the copied region, the second form
of overwrite() can be used. sminrow and smincol are the upper-left
coordinates of the source window, the other variables mark
a rectangle in the destination window.