vtkSliderRepresentation2D doesn't scale correctly to window changes
If vtkSliderWidget uses vtkSliderRepresentation2D and is not horizontally aligned, any changes to the aspect ratio of the render-window will lead to wrong scaling of the widget. This doesn't happen if the widget is horizontally aligned in the view. This issue was first found more than 10 years ago, but it still exists in version 8.9: #8270 (closed) #4382 (closed)
I use many vtkSliderWidgets in my application. Hope that this bug can be fixed.