Tk_MainWindow - find the main window for an application
#include <tk.h>
Tk_Window Tk_MainWindow(interp)
Interpreter associated with the application.
If interp is associated with a Tk application then Tk_MainWindow returns the application's main window. If there is no Tk application associated with interp then Tk_MainWindow returns NULL and leaves an error message in interp->result.
application, main window
