In order to make individual render windows unusable for specific user interaction a concept hast to be defined. The goal is to

• block user interaction with individual render windows that do not fulfill specific conditions
• allow to retrieve / report the "blocked" state of each render window

This is e.g. relevant for T29335: [Segmentation] Show interactive warning for uninitialized render window geometry, where the render windows should be blocker for mask drawing.
More relevant scenarios can be collected here.