Save background option (Layers) question

[Blizna]

In other thread I was told by Yves something I dont understand.

I have 3 layers and each layer has Save background disabled. My questions:

1) Some of game elements are displayed in the uppest layer (player names)-why they never paste?
2) The same with active things in second (middle) layer,e.g. birds-why they dont paste?
3) Why some of background objects do paste if they are in the middle, but only time from time? Yves told me its normal.

Also I realize I probably dont understand what Save background means in connection with layers.

Thank you

[DavidN]

I think (and this is only a guess) that a layer below one with "Save background" disabled will be displayed again when that layer is updated. What's in your lowest layer?

[Blizna]

The lowest layer: game world, characters
The second layer: tree crowns, birds, bridges..just if needed to be above characters
The third: game interface-chat, names...

[Yves]

In layers > 1, backdrop objects can be considered as "inactive active objects". I.e. (if the Save Background option is selected for their layer) their background is saved/restored as normal active objects, but this happens only when they are moved or when an active object or any other object that must be redrawn intersects with them.

If you unselect the Save Background option for their layer, and you move the layer, then the background behind them won't be restored, unless there is an object above them that restores it. That's all... That's why you think the backdrops are pasted randomly if you unselect this option.