The calling convention of the callback should be
stdcall
. But besides that
MSDN says:
Zitat:
Note The MagSetImageScalingCallback function is deprecated in Windows 7 and later, and should not be used in new applications. There is no alternate functionality.
and
Zitat:
This function works only when Desktop Window Manager (DWM) is off.
I guess the "magnifier window" uses a
DirectX surface to display the desktop screenshot. It might be possible to obtain its
handle (e.g. by hooking the corresponding
DirectX interface(s), if there is no other way to do it).