non-populated chunks shouldn't be light-populated anyway, but in some cases they are (bug or plugin interference).
chunks which were already populated might get modified by adjacent chunk populations, which should invalidate their lighting because generation doesn't track which blocks were changed, so the whole chunk should be recalculated.
when setBlockSkyLightArray/setBlockLightArray was used, currentLightArray would retain a reference to the old light array, which would cause false readings if SubChunkExplorer didn't move away from that subchunk and back.
This causes a small degradation of performance, but I think it can be implemented differently anyway.
This also fixes#3816.
previously a file with a 4-letter name ending in 'mca' in the region folder of a PMAnvil world would cause the world format to be unrecognized. This happens because strrpos() returns false when the substring isn't found, which gets coerced to 0 when used in addition.
this has a couple of side effects which need to be explored.
- first of all, this bug prevented generateLevel() from filling in the preset from server.properties. With this fix, worlds which don't have any extra generator settings will start to be generated using server.properties settings, which is almost certainly not expected behaviour.
- preset can now be specified separately from generator in pocketmine.yml, which is nicer for users.
this uses the unused bits on the Y component to expand the X/Z axes to 2^27 blocks long instead of 2^21 permitted by a regular morton3d code. It does require the sacrifice of an additional bit on the Y axis, but the performance advantages are more than worth it.
I'm exploring how realistic it would be to just eliminate blockHash global usage (currently in lighting updates and explosions). This would allow scaling up to 2^32 without larger hashes (morton2d for chunks).
this allows plugins (and maybe later on the core) to detect async worker overload and warn the user about potential performance issues.
I planned to implement such detection in the core directly, but it turned out to be a bit more complex than I anticipated. At the least, this API might be useful to someone else.
literally nobody uses this. I don't think anyone even knows it exists.
It's also an obstacle to separating event handler registration from PluginManager.
