Retrieves the x-extent and y-extent of the window for the specified device context
#include <WinAPIGdi.au3>
_WinAPI_GetWindowExt ( $hDC )
| $hDC | Handle to the device context. |
| Success: | $tagSIZE structure that contains the x- and y-extents in page-space units, that is, logical units. |
| Failure: | Sets the @error flag to non-zero, call _WinAPI_GetLastError() to get extended error information. |
Search GetWindowExtEx in MSDN Library.