SL4: How to expand search area for FindElementsinHostCoordinates()?
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We use this code to get a list of visible TextBox-derived objects:  

    GeneralTransform gt = this.scrollViewer.TransformToVisual(Application.Current.RootVisual as UIElement);  
    Point offset = gt.Transform(new Point(0, 0));

    double x = offset.X + this.scrollViewer.ViewportWidth + 30;  
    double y = offset.Y + this.scrollViewer.ViewportHeight + 30;
    visibleNodeIds = VisualTreeHelper.FindElementsInHostCoordinates(
       new Rect(offset, new Point(x, y)), OurCanvas)
		 .Where(element => element is CustomTextBox    )
		 .Cast<CustomTextBox>().Select(tb => tb.ParentNodeId).ToList();

However, a CustomTextBox that is partially outside the left edge of the viewable area is not included in the visibleTbIds list.  
How can we expand the search to include objects that are only partially visible?  
Thanks for any hints...

