To improve speed
RestoreScreen redraws only the modified screen area. But if there was
screen output produced by non-FAR functions (for example, if an external program was executed from
a plugin),
RestoreScreen cannot correctly calculate this area.
In that case you need first to call
RestoreScreen with
hScreen set to
NULL to inform FAR that the screen was changed and then call
RestoreScreen as usual with
SaveScreen handle.