WM_MOUSEMOVE
fwKeys = wParam; // key flags
xPos = LOWORD(lParam); // horizontal position of cursor
yPos = HIWORD(lParam); // vertical position of cursor
fwKeys
Value of wParam. Indicates whether various virtual keys are down. This parameter can be any combination of the following values: Value Description
MK_CONTROL Set if the ctrl key is down.
MK_LBUTTON Set if the left mouse button is down.
MK_MBUTTON Set if the middle mouse button is down.
MK_RBUTTON Set if the right mouse button is down.
MK_SHIFT Set if the shift key is down.