ThicknessRadioButton
button = new ThicknessRadioButton("Thin bar", 1.0);
button = new ThicknessRadioButton("Normal bar", fSlider->BarThickness());
button = new ThicknessRadioButton("Thick bar", 25.0);
ThicknessRadioButton* button
= dynamic_cast<ThicknessRadioButton*>(parent);
ThicknessRadioButton(const char* label, float thickness)
class ThicknessRadioButton;