protected override void OnRender(D2DGraphics g)
{
base.OnRender(g);
// set the transform before draw rect
g.SetTransform(mat.toD2DMatrix3x2());
g.FillRectangle(rect, isHitted ? D2DColor.LightYellow : D2DColor.LightGray);
g.DrawRectangle(rect, isHitted ? D2DColor.Red : D2DColor.Blue, 2);
g.DrawText("Drag to move / Click to rotate / Scroll to scale", D2DColor.Black, this.Font.Name, 14, rect,
DWriteTextAlignment.Center, DWriteParagraphAlignment.Center);
g.ResetTransform();
}
