@FXML
 void onColorButtonAction(ActionEvent event) {
   final ToggleButton tb = (ToggleButton) event.getTarget();
   assert tb == colorToggleButton;
   final Color value = colorPicker.getValue();
   // Update UI
   setMode(value);
   // Update model
   setPaintProperty(value);
   event.consume();
 }
 @FXML
 void onRadialButtonAction(ActionEvent event) {
   final ToggleButton tb = (ToggleButton) event.getTarget();
   assert tb == radialToggleButton;
   final Paint value = gradientPicker.getValue(Mode.RADIAL);
   assert value instanceof RadialGradient;
   // Update UI
   setMode(value);
   gradientPicker.setMode(value);
   gradientPicker.updatePreview(value);
   // Update model
   setPaintProperty(value);
   event.consume();
 }