static void OnPdfPathChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
TikzDisplay td = d as TikzDisplay;
td.TheModel.Refresh();
}
static void OnResolutionChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
TikzDisplay td = d as TikzDisplay;
td.TheModel.RedrawBMP(false);
}