this allows chunks locked for population to be modified. If the PopulationTask detects that the chunk was modified during the onCompletion(), the result of the population will be discarded and rescheduled, so that it includes user modifications.
tiles may be deleted in the following circumstances:
1) the target block in the new chunk doesn't expect a tile
2) the target block in the new chunk expects a different type of tile (responsibility of the plugin developer to create the new tile)
3) there's already a tile in the target chunk which conflicts with the old one
In all other cases, the tile will be transferred.
This resolves a large number of unintentional bugs caused by world editors replacing chunks without setting the deleteTilesAndEntities parameter to false (even the core itself does it).
closes#4520
entities exist completely independently from chunks now, so there is no need to interact with them whatsoever.
As I wrote in #4520, there's no sense in deleting entities here, since a chunk replacement is essentially just a mass block update.
On that theme, it might be a good idea to call Entity->onNearbyBlockChange() for all entities in the target and adjacent chunks when replacing a chunk, to ensure that they get the proper movement updates.
This reverts commit a5418a019d.
The more I assessed this, the more I realized that this implementation
doesn't actually offer any value. Since modcounters don't persist after
chunk unload + reload, they can't be reliably used to detect changes in
chunks without additional event subscriptions.
For the purpose I actually intended to use them for (population task
cancellation) there's a) another solution, and b) modcounts are
unreliable for that too, because of the aforementioned potential for
chunks to get unloaded and reloaded.
For the case of detecting dirty chunks within PopulationTask itself,
they are also unnecessary, since the dirty flags are sufficient within
there, since FastChunkSerializer doesn't copy dirty flags.
In conclusion, this was a misbegotten addition with little real value,
but does impact performance in hot paths.
setPopulated() sets dirty flags on the chunk, causing the autosave sweep
to think they've been changed when they haven't. We now pass
terrainPopulated to the constructor to avoid this ambiguity recurring in
the future.
making this nullable was based on the invalid assumption that global sounds have no position, but it turns out they _do_ still use the position to make the sound come from the correct direction.
