I am not sure why masks are so special over color, visibility. It also sounds as if there is a missing request of mask information somewhere.

To me it seems either of those is a more correct approach:

• Tag all updates on rebuild (mask, color, visibility). This way is only appropriate if it doesn't increase memory footprint and doesn't have performance impact when mask is not needed.
• Tag updates of all "data layers" when PBVH is rebuilt. For example, if PBVH had mask, tag mask update after the builds. This can be done for all "data layers" as a generic solution.

Makes sense to me to update everything. For color update actually doesn't do anything, and for visibility there is the test to check if nodes are fully hidden, which is probably needed after a rebuild too?

Probably the best option would be to combine this fix with D8225 so after the visibility state is copied from the face sets, both mask and visibility flags are updated after the PBVH creation.

EDIT: After the last update to D8225, merging both patches should make all flags update correctly

I think this patch is still relevant, is it ok to commit?

I think this patch is still relevant, is it ok to commit?

My previous comment is still relevant, and seems unaswred (unless I've missed something).