public override void CustomDrawToThisCanvas(DrawBoard canvas, Rectangle updateArea)
{
//
//TODO: review here again
//in pure agg, we could bypass the cache/resolve process
//and render directly to the target canvas
//
//if img changed then clear cache and render again
MemBitmap.ClearCache(_memBmp);
MemBitmap.SetCacheInnerImage(_memBmp, _nativeWin32DC, false);//** set to false because the (life-time) owner of the dc is this class (not the memBmp)
_demo.Draw(_painter);
//copy from actual image and paint to canvas
canvas.DrawImage(_memBmp, 0, 0);
}