Question

I am using a crude system to control a Flash movie from a C++/win32 program by sending WM_MOUSEMOVE events directly to the Flash window.

It works well for one axis:

SendMessage( m_targetWindowHWND, WM_MOUSEMOVE, 0, xpos);

However I’d like to now send both x and y values. I know these are packed into a WM_MOUSEMOVEs lparam. In C++ this could be unpacked with MAKEPOINTS or GET_X_LPARAM/GET_Y_LPARAM.

But how do I pack the x and y, basically doing the reverse of the macros above.

My guess:

DWORD packed = y << 8 + x;

Thanks

Answer 1

The macro you’re looking for is MAKELPARAM:

http://msdn.microsoft.com/en-us/library/windows/desktop/ms632661(v=vs.85).aspx

LPARAM WINAPI MAKELPARAM(
    WORD wLow,
    WORD wHigh
);

I believe it’s equivalent to MAKELONG (same thing but returns a DWORD), but then again…maybe there’s a platform out there where a LPARAM and a DWORD are defined differently. :-/

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EDIT: Apparently LPARAM (and WPARAM!) are nowadays both defined under the hood to be the size of pointers on your platform. The “L” (long) and “W” (word) are historical: What are the definitions for LPARAM and WPARAM?