vtkCellPicker can not pick vtkScalarBarActor

I want to pick the vtkScalarBarActor using vtkCellPicker, but it failed.

The code to reproduce my problem is:

import vtkmodules.all as vtk

actor = vtk.vtkScalarBarActor()
actor.SetNumberOfLabels(4)

actor.SetDrawFrame(False)
actor.SetDrawBackground(False)
actor.UnconstrainedFontSizeOn()
actor.DrawAnnotationsOn()
actor.DrawTickLabelsOn()
actor.AnnotationTextScalingOff()
actor.GetLabelTextProperty().SetFontSize(10)

lut = vtk.vtkLookupTable()
actor.SetLookupTable(lut)

render = vtk.vtkRenderer()
render.AddActor(actor)
render.SetBackground(1, 1, 1)

renWin = vtk.vtkRenderWindow()
renWin.AddRenderer(render)
iren = vtk.vtkRenderWindowInteractor()
iren.SetRenderWindow(renWin)

def mouseMoveEvent(iren, event):
    x, y = iren.GetEventPosition()
    picker = vtk.vtkCellPicker()
    # picker = vtk.vtkPropPicker()
    picker.Pick(x, y, 0, render)
    actor = picker.GetViewProp()
    print(actor)


iren.AddObserver('MouseMoveEvent', mouseMoveEvent)

iren.Initialize()
iren.Start()

I found that the printed actor is always None when the mouse is moved on the vtkScalarBarActor.

How to pick the vtkScalarBarActor using vtkCellPicker?

Also, I found vtkPropPicker can pick vtkScalarBarActor, but it don’t implement the SetTolerance method. And it is the reason why I perfer the vtkCellPicker.

Any suggestion is appreciated~~~