An application sends the WM_NCPAINT message to a window when its frame must be painted.
WM_NCPAINT
hrgn = (HRGN) wParam; // handle of update region
Parameters
hrgn
Value of wParam. Identifies the update region of the window. The update region is clipped to the window frame.
Return Values
An application should return zero if it processes this message.
Remarks
The DefWindowProc function paints the window frame.
An application can intercept this message and paint its own custom window frame. The clipping region for a window is always rectangular, even if the shape of the frame is altered.
See Also