FvwmButtons (a module of fvwm window manager) has the Swallow function, that embeds the window of an application into a panel.
I have to do something like this with Motif and Xlib. I want to embed an Xclock into my application. I guess I have to change the Window ID of the embedded app.
How can I do that?
the only supported and reliable mechanism is XEmbed, but it requires the embedded app to cooperate. Without a cooperating app, you're in a world of scary hacks.
The basic thing you need to do is XReparentWindow() but the problem is that you're fighting the window manager which will also want to reparent the window. You're also potentially confusing the app, which will be expecting ICCCM and EWMH behavior, and expecting the parent window to be a WM frame.
Really old GNOME 1.x versions of gnome panel had a swallow feature you could try to steal hacks from maybe.
Without pretty extensive X knowledge this will be painful, and even with it's not necessarily possible to make 100% reliable.
来源：https://stackoverflow.com/questions/5395044/embed-an-app-into-a-window