Embedding Tk into a native Win32 GUI
In the window below, that is a Win32 API based progam, with a HWND embedded
into the client area of the toplevel window. In that HWND is a Tk window with a
packed frame with 2 buttons and a canvas. The canvas draws little circles when
you click on it. This is about 35 lines of Tcl/Tk, and about 45 lines of C.