Determines whether any part of the specified rectangle lies within the clipping region
#include <WinAPIGdi.au3>
_WinAPI_RectVisible ( $hDC, $tRECT )
| $hDC | Handle to the device context. |
| $tRECT | $tagRECT structure that contains the logical coordinates of the specified rectangle. |
| Success: | 1, 2 - any portion of the given rectangle lies within the clipping region. 0 - Otherwise. |
| Failure: | Sets the @error flag to non-zero, @extended flag may contain an error code. |
Search RectVisible in MSDN Library.