we can have a layer where HasValidTilePriorities is false (tile opacity goes to 0%, etc...). This means that the tile will be skipped during tile iteration (both in assigngpumem and in checking whether we can activate). Specifically, this means that it's required state is not checked.

We could check whether the layer that owns this tiling has valid tile priorities and if not, assume the tile is done. However, that would come at a cost of a virtual function call for every tile here. I'm gonna leave the decision of that to do up to you.

We could also make the UpdateRequiredStatesOnTile make it false when the layer doesn't have valid tile priorities, but it's the same cost basically.