Make it works in the Prefab Mode

[5argon]

Increasingly it is very useful to design a UI in the prefab mode, when you planning to assemble multiple UI to a single scene instead of doing multi scene like before.

If those pieces are full screen panel, likely that they will be with SafeAreaPadding. So, I would like to make this work in the prefab mode. What's the problem ?

• The overlay is added as a hidden + not saved prefab to the hierarchy tree. How to make that appears in the prefab mode hierarchy tree cleanly?
• The problem is the overlay is a new canvas which is possible to spawn independenly as a sibling when outside of prefab mode. In the prefab mode however it is only possible to have 1 top level canvas (the editing object). Then we need a new code path that sandwich our overlay Canvas in the top level Canvas in the case of prefab mode overlay.
• What will happen to the overlay when we drill down and come back? Ideally I want it destroy and recreated on the next layer/previous layer in the case of coming back. So the state will still be synched with the Notch Simulator check box.
• Exiting the prefab mode should resume the overlay behaviour in the outside mode accordingly, the overlay that was inside the prefab must be destroyed.