void ClearNotebooks()
 {
     for (int n = notebooks.Count - 1; n >= 0; n--)
     {
         ITabStrip ts = notebooks[n];
         notebooks.RemoveAt(n);
         ts.Clear();
         ts.Unparent();
         ts.Destroy();
     }
 }
        void LayoutWidgets()
        {
            if (!needsRelayout)
            {
                return;
            }
            needsRelayout = false;

            // RemoveNotebooks();

            // Create the needed notebooks and place the widgets in there

            List <DockGroup> tabbedGroups = new List <DockGroup>();

            GetTabbedGroups(layout, tabbedGroups);

            for (int n = 0; n < tabbedGroups.Count; n++)
            {
                DockGroup grp = tabbedGroups[n];
                ITabStrip ts  = null;
                if (n < notebooks.Count)
                {
                    ts = notebooks[n];
                }
                else
                {
                    switch (frame.TabType)
                    {
                    case DockFrame.TabAlgorithm.Proven:
                        ts = new TabStrip();
                        break;

                    case DockFrame.TabAlgorithm.Smooth:
                        ts = new TabSelector(false);
                        break;

                    case DockFrame.TabAlgorithm.Active:
                        ts = new TabSelector(true);
                        break;
                    }

                    ts.Show();
                    notebooks.Add(ts);
                    ts.Parent = this;
                }
                frame.UpdateRegionStyle(grp);
                ts.VisualStyle = grp.VisualStyle;
                grp.UpdateNotebook(ts);
            }

            // Remove spare tab strips
            for (int n = notebooks.Count - 1; n >= tabbedGroups.Count; n--)
            {
                ITabStrip ts = notebooks[n];
                notebooks.RemoveAt(n);
                ts.Clear();
                ts.Unparent();
                ts.Destroy();
            }

            // Create and add the required splitters

            int reqSpliters = CountRequiredSplitters(layout);

            for (int n = 0; n < splitters.Count; n++)
            {
                var s = splitters[n];
                if (s.Parent != null)
                {
                    Remove(s);
                }
            }

            // Hide the splitters that are not required

            for (int n = reqSpliters; n < splitters.Count; n++)
            {
                splitters[n].Hide();
            }

            // Add widgets to the container

            layout.LayoutWidgets();

            // Create and add the required splitters

            for (int n = 0; n < reqSpliters; n++)
            {
                if (n < splitters.Count)
                {
                    var s = splitters[n];
                    if (!s.Visible)
                    {
                        s.Show();
                    }
                    Add(s);
                }
                else
                {
                    var s = new SplitterWidget();
                    splitters.Add(s);
                    s.Show();
                    Add(s);
                }
            }
        }