[source = "c++"]
/*
error C2065: 'SPI_GETWHEELSCROLLLINES' : undeclared identifier
error C2065: 'WHEEL_DELTA' : undeclared identifier
error C2065: 'WM_MOUSEWHEEL' : undeclared identifier
*/
 
  ---------------------------------------------------*/
 
#include <windows.h>
...
...
...
case WM_SETTINGCHANGE:
		SystemParametersInfo (SPI_GETWHEELSCROLLLINES, 0, &ulScrollLines, 0);
 
		//ulScrollLines usually equals 3 or 0(for no scrolling)
		//WHEEL_DELTA equals 120, so iDeltaPerLine will be 40
		if(ulScrollLines)
		{
			iDeltaPerLine = WHEEL_DELTA / ulScrollLines;
		}else
		{
			iDeltaPerLine = 0;
		}
		return 0;