The WM_CAPTURECHANGED message is sent to the window that is losing the mouse capture.
WM_CAPTURECHANGED
hwndNewCapture = (HWND) lParam; // handle of window to gain mouse capture
Parameters
hwndNewCapture
Value of lParam. Identifies the window that is gaining the mouse capture.
Return Values
An application should return zero if it processes this message.
Remarks
A window receives this message even if it calls ReleaseCapture itself. An application should not attempt to set the mouse capture in response to this message.
When it receives this message, a window should redraw itself, if necessary, to reflect the new mouse-capture state.
See Also