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Gtk+/Gnome Application Development
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Other GtkBinFunctionality

GtkBin also provides default implementations of expose, map, unmap, and draw from GtkWidgetClass. Most GtkBin subclasses will override these methods to handle the unique features of the subclass, but chain up to the GtkBin method to deal with their child widget.

The GtkBin map and unmap implementations are mostly the usual boilerplate (set GTK_MAPPED, show widget->window) but they add an important step unique to containers: mapping the child if it has been shown (remember that GTK_VISIBLE signals a widget has been shown), and unmapping the child when the bin is unmapped. Here's the code:


static void
gtk_bin_map (GtkWidget *widget)
{
  GtkBin *bin;

  g_return_if_fail (widget != NULL);
  g_return_if_fail (GTK_IS_BIN (widget));

  GTK_WIDGET_SET_FLAGS (widget, GTK_MAPPED);
  bin = GTK_BIN (widget);

  if (bin->child &&
      GTK_WIDGET_VISIBLE (bin->child) &&
      !GTK_WIDGET_MAPPED (bin->child))
    gtk_widget_map (bin->child);

  if (!GTK_WIDGET_NO_WINDOW (widget))
    gdk_window_show (widget->window);
}

static void
gtk_bin_unmap (GtkWidget *widget)
{
  GtkBin *bin;

  g_return_if_fail (widget != NULL);
  g_return_if_fail (GTK_IS_BIN (widget));

  GTK_WIDGET_UNSET_FLAGS (widget, GTK_MAPPED);
  bin = GTK_BIN (widget);

  if (GTK_WIDGET_NO_WINDOW (widget))
     gtk_widget_queue_clear (widget);
  else
    gdk_window_hide (widget->window);

  if (bin->child && GTK_WIDGET_MAPPED (bin->child))
    gtk_widget_unmap (bin->child);
}
    

GtkBin's draw and expose implementations simply redraw the child widget; most subclasses will need to override these methods in order to draw themselves, then chain up to draw the child. The code:


static void
gtk_bin_draw (GtkWidget    *widget,
              GdkRectangle *area)
{
  GtkBin *bin;
  GdkRectangle child_area;

  g_return_if_fail (widget != NULL);
  g_return_if_fail (GTK_IS_BIN (widget));

  bin = GTK_BIN (widget);

  if (GTK_WIDGET_DRAWABLE (bin))
    {
      if (bin->child && GTK_WIDGET_DRAWABLE (bin->child) &&
          gtk_widget_intersect (bin->child, area, &child_area))
        gtk_widget_draw (bin->child, &child_area);
    }
}

static gint
gtk_bin_expose (GtkWidget      *widget,
                GdkEventExpose *event)
{
  GtkBin *bin;
  GdkEventExpose child_event;

  g_return_val_if_fail (widget != NULL, FALSE);
  g_return_val_if_fail (GTK_IS_BIN (widget), FALSE);
  g_return_val_if_fail (event != NULL, FALSE);

  if (GTK_WIDGET_DRAWABLE (widget))
    {
      bin = GTK_BIN (widget);

      child_event = *event;
      if (bin->child && GTK_WIDGET_DRAWABLE (bin->child) &&
          GTK_WIDGET_NO_WINDOW (bin->child) &&
          gtk_widget_intersect (bin->child, &event->area, &child_event.area))
        gtk_widget_event (bin->child, (GdkEvent*) &child_event);
    }

  return FALSE;
}
    

Notice that expose events are only generated for windowless widgets; widgets with windows will receive their own expose events. Containers are required to generate expose events for windowless children.

You can probably guess that gtk_widget_intersect() determines the intersection of a rectangle and a child widget.

Gtk+/Gnome Application Development
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