Remove unnecessary map-event callback in wxGTK wxFileDialog

Calling gtk_file_chooser_set_show_hidden() directly from Create() works
just as well and is simpler and shorter.

See https://github.com/wxWidgets/wxWidgets/pull/1413

src/gtk/filedlg.cpp

@@ -151,21 +151,6 @@ static void gtk_filedialog_update_preview_callback(GtkFileChooser *chooser,
 
 } // extern "C"
 
-extern "C"
-{
-static gboolean gtk_frame_map_callback( GtkFileChooser *file_chooser,
-                        GdkEvent * WXUNUSED(event),
-                        wxFileDialog *dlg )
-{
-/*    if ( dlg->GetWindowStyle() & wxFD_SHOW_HIDDEN )
-        gtk_file_chooser_set_show_hidden( file_chooser, TRUE );
-    else
-        gtk_file_chooser_set_show_hidden( file_chooser, FALSE );*/
-    gtk_file_chooser_set_show_hidden(file_chooser, dlg->HasFlag(wxFD_SHOW_HIDDEN));
-    return FALSE;
-}
-}
-
 void wxFileDialog::AddChildGTK(wxWindowGTK* child)
 {
     // allow dialog to be resized smaller horizontally
@@ -290,8 +275,6 @@ bool wxFileDialog::Create(wxWindow *parent, const wxString& message,
     g_signal_connect (m_widget, "selection-changed",
         G_CALLBACK (gtk_filedialog_selchanged_callback), this);
 
-    g_signal_connect (m_widget, "map_event",
-                      G_CALLBACK (gtk_frame_map_callback), this);
      // deal with extensions/filters
     SetWildcard(wildCard);
 
@@ -367,6 +350,9 @@ bool wxFileDialog::Create(wxWindow *parent, const wxString& message,
                          previewImage);
     }
 
+    gtk_file_chooser_set_show_hidden(file_chooser,
+                                     style & wxFD_SHOW_HIDDEN ? TRUE : FALSE);
+
     return true;
 }