private static void OnCurrentCommitChanged(DependencyObject sender, DependencyPropertyChangedEventArgs e)
        {
            PlotCommitElement that = sender as PlotCommitElement;

            if (that != null)
            {
                that.ToolTip = that.CurrentCommit.getAuthorIdent().ToString();
                that.InvalidateVisual();
            }
        }
        private void UpdateLegend()
        {
            PlotCommitElement emt = new PlotCommitElement();

            this.imgLegend.Source = new DrawingImage(emt.GetLegend().Drawing);
        }