private void RefreshChanges()
                {
                    Region    region       = new Region(Rectangle.Empty);
                    Rectangle rectDockArea = FullPanelEdge ? DockPanel.DockArea : DockPanel.DocumentWindowBounds;

                    rectDockArea = RectangleToClient(DockPanel.RectangleToScreen(rectDockArea));
                    if (ShouldPanelIndicatorVisible(DockState.DockLeft))
                    {
                        PanelLeft.Location = new Point(rectDockArea.X + _PanelIndicatorMargin, rectDockArea.Y + (rectDockArea.Height - PanelRight.Height) / 2);
                        PanelLeft.Visible  = true;
                        region.Union(PanelLeft.Bounds);
                    }
                    else
                    {
                        PanelLeft.Visible = false;
                    }

                    if (ShouldPanelIndicatorVisible(DockState.DockRight))
                    {
                        PanelRight.Location = new Point(rectDockArea.X + rectDockArea.Width - PanelRight.Width - _PanelIndicatorMargin, rectDockArea.Y + (rectDockArea.Height - PanelRight.Height) / 2);
                        PanelRight.Visible  = true;
                        region.Union(PanelRight.Bounds);
                    }
                    else
                    {
                        PanelRight.Visible = false;
                    }

                    if (ShouldPanelIndicatorVisible(DockState.DockTop))
                    {
                        PanelTop.Location = new Point(rectDockArea.X + (rectDockArea.Width - PanelTop.Width) / 2, rectDockArea.Y + _PanelIndicatorMargin);
                        PanelTop.Visible  = true;
                        region.Union(PanelTop.Bounds);
                    }
                    else
                    {
                        PanelTop.Visible = false;
                    }

                    if (ShouldPanelIndicatorVisible(DockState.DockBottom))
                    {
                        PanelBottom.Location = new Point(rectDockArea.X + (rectDockArea.Width - PanelBottom.Width) / 2, rectDockArea.Y + rectDockArea.Height - PanelBottom.Height - _PanelIndicatorMargin);
                        PanelBottom.Visible  = true;
                        region.Union(PanelBottom.Bounds);
                    }
                    else
                    {
                        PanelBottom.Visible = false;
                    }

                    if (ShouldPanelIndicatorVisible(DockState.Document))
                    {
                        Rectangle rectDocumentWindow = RectangleToClient(DockPanel.RectangleToScreen(DockPanel.DocumentWindowBounds));
                        PanelFill.Location = new Point(rectDocumentWindow.X + (rectDocumentWindow.Width - PanelFill.Width) / 2, rectDocumentWindow.Y + (rectDocumentWindow.Height - PanelFill.Height) / 2);
                        PanelFill.Visible  = true;
                        region.Union(PanelFill.Bounds);
                    }
                    else
                    {
                        PanelFill.Visible = false;
                    }

                    if (ShouldPaneDiamondVisible())
                    {
                        Rectangle rect = RectangleToClient(DockPane.RectangleToScreen(DockPane.ClientRectangle));
                        PaneDiamond.Location = new Point(rect.Left + (rect.Width - PaneDiamond.Width) / 2, rect.Top + (rect.Height - PaneDiamond.Height) / 2);
                        PaneDiamond.Visible  = true;
                        using (GraphicsPath graphicsPath = PaneDiamond.DisplayingGraphicsPath.Clone() as GraphicsPath)
                        {
                            Point[] pts =
                            {
                                new Point(PaneDiamond.Left,  PaneDiamond.Top),
                                new Point(PaneDiamond.Right, PaneDiamond.Top),
                                new Point(PaneDiamond.Left,  PaneDiamond.Bottom)
                            };
                            using (Matrix matrix = new Matrix(PaneDiamond.ClientRectangle, pts))
                            {
                                graphicsPath.Transform(matrix);
                            }

                            region.Union(graphicsPath);
                        }
                    }
                    else
                    {
                        PaneDiamond.Visible = false;
                    }

                    Region = region;
                }