How do I connect wxWidgets, GTK2 widgets, and X11 windows?

Question

I gather from the various wxWidgets class references in the documentation (example) that the wxWidgets used to build a GUI basically inherit from wxWindow. I see from the comments in the source of wxWidgets/window.cpp that each wxWindow has a pointer to some GtkWidget which is stored in the m_widget member of the wxWidget object. From the same source code comments I also see that m_wxwindow is a member of the wxWindow class, and may hold a pointer to a wxPizza object in the case of a wxWindow that has a client area for drawing and children.

I am working on an application that requires this sort of functionality. I am extending a wxWidgets class to create my own widget, which needs to contain a drawable X11 window, and I'm not really sure how to connect it all up and I'm having trouble finding a solution using the documentation.

When I am creating my custom widget (in the Create method), I can see that m_widget and m_wxwindow are both NULL, so from this and what I mentioned above, I gather these are the GtkWidget objects that I should be creating to form my client area. First, I tried this:

m_widget = gtk_window_new(GTK_WINDOW_TOPLEVEL);

Which kind of works but not quite like I want it to. I'm able to get the XID from the GtkWidget and the X11 window behaves as expected. But this creates a new window outside of my main wxWidgets app window. What I want is this exact functionality except embedded inside my main wxWidgets app window. My custom class has been added to a wxBoxSizer like this:

sizer->Add(my_widget, 1, wxEXPAND | wxALL, 0);

Where sizer is a wxBoxSizer and my_widget is my custom widget.

I then tried creating m_widget as a few different types of GtkWidget but these all resulted in run-time errors when trying to use gtk_widget_realize and trying to get the XID.

// These don't work
m_widget = gtk_drawing_area_new();
m_widget = gtk_vbox_new(false, 0);

These are the error messages I'm getting when I tried the above:

Gtk: IA__gtk_widget_realize: assertion 'GTK_WIDGET_ANCHORED (widget) || GTK_IS_INVISIBLE (widget)' failed
Gdk: gdkdrawable-x11.c:952 drawable is not a pixmap or window
Check failed: xwindow.

So I this is a multi-part question:

• What is an appropriate GtkWidget type to get this accomplished? I need to be able to obtain a drawable X11 window ID (XID) and to embed it within the parent widget (wxBoxSizer).
• Do I need to use both m_widget and m_wxwindow? How do I set these up?
• Do I need to do anything other than call sizer->Add() in order to connect this up with my wxBoxSizer?

Thanks!

UPDATE: Sorry I forgot to mention, this is for GTK2. Thanks @andlabs for pointing this out.

UPDATE 2: @VZ. recommended that I clarify what I'm trying to do.

I'm using a library that needs access to an X11 window, but does not create that window itself. When I initialize the library, I need to pass it an X11 window handle (XID). The library will then draw into that window. I want to create this window to be inside my wxWidgets application. I'm trying to extend a wxWidgets class so that I will be able to add these X11 windows to widgets based on wxSizer in my application.

I know that gtk_window_new() is not what I'm looking for because it creates a new top-level window, while I want a window embedded in my wxWidgets application. It's just something I tried along the way.

Answer 1

It would be really helpful to know what exactly are you trying to do. You speak about GtkWidgetss but then show gtk_window_new() call which creates a new (top level) window, which is something quite different and can only be represented by wxTopLevelWindow at wx level.

Do you need to wrap an existing GtkWidget in a wxWidgets application? If so, you should just use wxNativeWindow. Even if you don't use the latest version with it, you can still easily reuse/duplicate its code.

Do you need to wrap an existing XWindow? Then it's more difficult because you can't easily do it with wxGTK. You could use wxX11, but this port is not in a good state, so it's probably not the best idea, unless your needs are very limited. The best would probably be to wrap X window in a GtkWidget first and then proceed as above.

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After the update, it seems that you just need a XID of an existing window. This is even simpler than embedding a GTK+ widget as you can get the GtkWidget using wxWindow::GetHandle(), then use gtk_widget_get_window() to get its GdkWindow and finally use GDK_WINDOW_XID() to get the XID.