Support Wayland in wxGTK wxMediaCtrl

For GTK, the current implementation assumes X11 is the only window option.
Introduce runtime checks to manage Wayland too.

Signed-off-by: Pierluigi Passaro <pierluigi.p@variscite.com>

Closes https://github.com/wxWidgets/wxWidgets/pull/2257

include/wx/gtk/private/mediactrl.h

@@ -0,0 +1,54 @@
+///////////////////////////////////////////////////////////////////////////////
+// Name:        wx/gtk/private/mediactrl.h
+// Purpose:     Wrap runtime checks to manage GTK windows with Wayland and X11
+// Author:      Pierluigi Passaro
+// Created:     2021-03-18
+// Copyright:   (c) 2021 Pierluigi Passaro <pierluigi.p@variscite.com>
+// Licence:     wxWindows licence
+///////////////////////////////////////////////////////////////////////////////
+
+#ifndef _WX_GTK_PRIVATE_MEDIACTRL_H_
+#define _WX_GTK_PRIVATE_MEDIACTRL_H_
+
+#ifdef GDK_WINDOWING_X11
+    #include <gdk/gdkx.h>
+#endif
+#ifdef GDK_WINDOWING_WAYLAND
+    #include <gdk/gdkwayland.h>
+#endif
+
+//-----------------------------------------------------------------------------
+// "wxGtkGetIdFromWidget" from widget
+//
+// Get the windows_id performing run-time checks If the window wasn't realized
+// when Load was called, this is the callback for when it is - the purpose of
+// which is to tell GStreamer to play the video in our control
+//-----------------------------------------------------------------------------
+extern "C" {
+inline gpointer wxGtkGetIdFromWidget(GtkWidget* widget)
+{
+    gdk_flush();
+
+    GdkWindow* window = gtk_widget_get_window(widget);
+    wxASSERT(window);
+
+#ifdef GDK_WINDOWING_X11
+#ifdef __WXGTK3__
+    if ( GDK_IS_X11_WINDOW(window) )
+#endif
+    {
+        return (gpointer)GDK_WINDOW_XID(window);
+    }
+#endif
+#ifdef GDK_WINDOWING_WAYLAND
+    if ( GDK_IS_WAYLAND_WINDOW(window) )
+    {
+        return (gpointer)gdk_wayland_window_get_wl_surface(window);
+    }
+#endif
+
+    return (gpointer)NULL;
+}
+}
+
+#endif // _WX_GTK_PRIVATE_MEDIACTRL_H_