Screen: Remove superfluous guards.
The code commented with nowrap!
has no use: _cuX
and _cuY
get
updated to this value on image resize. This code also appeared in
functions unrelated to horizontal wrapping.
I also took the liberty to update the conditions which determine whether to use "default values." Before, the conditions only checked for zero instead of (invalid/explosive) negative numbers (maybe a few Q_ASSERT's are desired here?).