An application sends this message to IME window to get the position of the composition window. An IME may adjust the position of a composition window regarding to some concerns. An application can get the real position of composition window to decide whether it want to reposition it to another position.
lParam
Address of a COMPOSITIONFORM structure that receives the position of the composition window.
The return value in the buffer is in the client coordinates of the focus window of an application. The UI window receives this message.