Additional information about the message. The exact meaning depends on the message value.
如果message=WM_MOUSEMOVE
wParam
Indicates whether various virtual keys are down. This parameter can be one or more of the following values.
lParam
The low-order word specifies the x-coordinate of the cursor. The coordinate is relative to the upper-left corner of the client area.
The high-order word specifies the y-coordinate of the cursor. The coordinate is relative to the upper-left corner of the client area.