What you are looking for is the vtkLegendScaleActor
class. You can find example (https://examples.vtk.org/site/Cxx/Visualization/LegendScaleActor/) and tests.
What you are looking for is the vtkLegendScaleActor
class. You can find example (https://examples.vtk.org/site/Cxx/Visualization/LegendScaleActor/) and tests.