GET_WHEEL_DELTA_WPARAM macro in C#

Question

How would I go about using the GET_WHEEL_DELTA_WPARAM macro in C#?

Answer 1

For maximum clarity, I would define a set of functions like this:

internal static class NativeMethods
{
    internal static ushort HIWORD(IntPtr dwValue)
    {
        return (ushort)((((long)dwValue) >> 0x10) & 0xffff);
    }

    internal static ushort HIWORD(uint dwValue)
    {
        return (ushort)(dwValue >> 0x10);
    }

    internal static int GET_WHEEL_DELTA_WPARAM(IntPtr wParam)
    {
        return (short)HIWORD(wParam);
    }

    internal static int GET_WHEEL_DELTA_WPARAM(uint wParam)
    {
        return (short)HIWORD(wParam);
    }
}

And then use the function like so, where wParam is the WPARAM parameter you get from handling the Win32 WM_MOUSEWHEEL or WM_MOUSEHWHEEL messages:

int zDelta = NativeMethods.GET_WHEEL_DELTA_WPARAM(wParam);

You might need to suppress overflow-checking in order for this to work properly. To do so, either change your project settings, or wrap the relevant conversion functions in an unchecked block.

Answer 2

High-order word, signed:

 ((short)(wParam>>16))