// detaches the projection from the given target element
private void _dettach(FrameworkElement target) {
if (_target != target) {
throw new InvalidOperationException();
}
_target.SizeChanged -= _onTargetSizeChanged;
_target.Effect = null;
_target = null;
_effect = null;
}
// attaches the projection to the given target element
private void _attach(FrameworkElement target) {
_target = target;
_effect = new PlaneProjectionEffect() { RecenterViewport = true };
_target.Effect = _effect;
_scaleTransform = new ScaleTransform();
_translateTransform = new TranslateTransform();
_target.RenderTransformOrigin = new Point(0.5, 0.5);
_target.RenderTransform = new TransformGroup { Children = { _scaleTransform, _translateTransform } };
_target.SizeChanged += _onTargetSizeChanged;
_updateRenderSize();
}