WPF Adorner Clipping

Question

I have an ItemsControl in a ScrollViewer. The items in the ItemsControl are expanded to a DataTemplate which basically consis

Answer 1

I've encountered the same problem when subclassing the WPFToolkit DataGrid to draw an adorner around the current cell.

The content of the ScrollViewer is rendered by a ScrollContentPresenter instance. ScrollContentPresenter has its own adorner layer, which is accessible through the ScrollContentPresenter.AdornerLayer property.

I found that my adorner correctly clips if I add it to that layer.

Answer 2

My solution was to push a clip region onto the drawing context, render whatever I needed, and pop the clipping at the end, like this:

drawingContext.PushClip(new RectangleGeometry(new Rect(0, 0, this.AdornedElement.RenderSize.Width, this.AdornedElement.RenderSize.Height)));
// continue drawing
drawingContext.Pop();

You can plug this in into any Adorner, the bounds are already available as part of the element.

Answer 3

Setting ClipToBounds on the containing control is not enough. You must set the adorner's IsClipEnabled property too.