add missing GTK3 implementations of GTKGetWindow()

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@75864 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/gtk/window.h

@@ -14,8 +14,10 @@
 #ifdef __WXGTK3__
     typedef struct _cairo cairo_t;
     typedef struct _GtkStyleProvider GtkStyleProvider;
+    #define WXUNUSED_IN_GTK2(x) x
     #define WXUNUSED_IN_GTK3(x)
 #else
+    #define WXUNUSED_IN_GTK2(x)
     #define WXUNUSED_IN_GTK3(x) x
 #endif
 
@@ -427,6 +429,11 @@ protected:
 
     void ConstrainSize();
 
+#ifdef __WXGTK3__
+    static GdkWindow* GTKFindWindow(GtkWidget* widget);
+    static void GTKFindWindow(GtkWidget* widget, wxArrayGdkWindows& windows);
+#endif
+
 private:
     void Init();