void DrawConnectingLine(IRenderEngine engine, Task task, Task parent)
{
var rc1 = GetTaskRect(parent); // parent rect
var rc2 = GetTaskRect(task); // task rect
var x1 = rc1.Left + rc1.Width / 2; // parent x center
var x2 = rc2.Left; // task left
var y1 = rc1.Bottom; // parent bottom
var y2 = rc2.Top + rc2.Height / 2; // task y center
// draw connecting line
var xs = new double[] { x1, x1, x2 };
var ys = new double[] { y1, y2, y2 };
engine.SetStroke(new SolidColorBrush(Color.FromRgb(0, 0, 0)));
engine.DrawLines(xs, ys);
// draw arrow at the end
var sz = 5;
xs = new double[] { x2 - 2 * sz, x2, x2 - 2 * sz };
ys = new double[] { y2 - sz, y2, y2 + sz };
engine.SetFill(new SolidColorBrush(Color.FromRgb(0, 0, 0)));
engine.DrawPolygon(xs, ys);
}
