U++

I am somewhat reluctant to provide this: move to GTK was primarily intended to isolate us from X11, so that when e.g. wayland takes over, we are safe. Or perhaps to support more platforms.

I think you should rather use

class Ctrl {
public:
    GdkWindow *gdk() const { return top ? top->window->window : NULL; }
    GtkWindow *gtk() const { return top ? (GtkWindow *)top->window : NULL; }
}

and then use gdk/gtk functions to retrieve X11 handle (possible with #ifdef GDK_WINDOWING_X11).

Any solution for me is good, as long as I can get the platform window handle for a DHCtrl.
I'm creating an OpenCascade control and it needs a windowed control and its handle.

IMHO, the best would be to provide the handle from inside DHCtrl with a protected function, so when you
adds new platform you just have to provide this function for new platforms and the rest stays almost
platform-independent, but any way will do the trick for me.

If you add it in some way, I'll adapt my code.

Well, what I wanted to say is that for GTK backend the apparent handle is not X11 id, but GtkWindow * (or GdkWindow *)....

I am not quite sure whether creating something like

void *GetWindowHandle();

is a good idea - I think you would still have to provide platform specific code (plus it is not quite defined which one of 3 possible handles it should return for GTK/X11).

Hi,

I tested with gtk() and gdk() functions, but they return NULL.
I guess (just lurked a bit inside your code...) because DHCtrl, in GTK mode, is simply an alias of Ctrl which don't get a window (aka top==NULL).

I think that DHCtrl should be a windowed control as in win32 and x11 mode, otherwise it becomes useless.
And I think, once it's windowed, it could contain a member function to get its handle.
The latter isn't mandatory, of course, but why have a DHCtrl then, if there's no access need to plaform-dependent window ?