When I place a TextBlock inside of a Horizontally Aligned StackPanel it does not wrap. I realize that this is because the available width of the StackPanel is PositiveInfini
You could use a grid instead of the StackPanel (which as explained does not restrict its content.). A grid allows much more control over layout of items than a StackPanel does and if your image is collapsed then the 'auto' column will have a 0 width.