Sets a custom titlebar for window.
If you set a custom titlebar, GTK+ will do its best to convince
the window manager not to put its own titlebar on the window.
Depending on the system, this function may not work for a window
that is already visible, so you set the titlebar before calling
gtk_widget_show().
Sets a custom titlebar for window. If you set a custom titlebar, GTK+ will do its best to convince the window manager not to put its own titlebar on the window. Depending on the system, this function may not work for a window that is already visible, so you set the titlebar before calling gtk_widget_show().