The following code example shows how to use the TransformToVisual method to retrieve the offset of the StackPanel relative to its child TextBlock. The offset values are contained within the returned GeneralTransform value.
// Return the general transform for the specified visual object.
GeneralTransform generalTransform1 = myStackPanel.TransformToVisual(myTextBlock);
// Retrieve the point value relative to the child.
Point currentPoint = generalTransform1.Transform(new Point(0, 0));
The offset takes into account the Margin values for all objects. In this case, X is -4, and Y is -4. The offset values are negative values because the parent object is negatively offset relative to its child object.