SetUIBrightnessPreference does not change the brghtness of InDesign

I want to create an plugin that change and detect the brightness of indesign CC2015 preference.

I have used

               InterfacePtr<IApplication> application(GetExecutionContextSession()->QueryApplication());

               InterfacePtr<IUserInterfacePreferences> ui(application, IID_IUSERINTERFACEPREFERENCES);

Here I get

               PMReal p = ui->GetUIBrightnessPreference();

But the p's value is null or empty. I have printed it with a InformationAlert, But nothing is there.

set the brightness to 0.33

               ui->SetUIBrightnessPreference(0.33);

but it does not change anything. Do I have to call something like ApplyPreference... something.