The app doesn't need to be aware of the content under the widget it wants to have an alpha value < 1.0. Its the job of the compositor to render the app's conte

The app doesn't need to be aware of the content under the widget it wants to have an alpha value < 1.0. Its the job of the compositor to render the app's content as provided, regardless of what is over or under it, that is what it exists to do.