Affects:
Superflat Void Preset
In order to create the icon there should be 11 close cubic chunks with blocks on the screen (Found via experiments). So, if there are less nonempty chunks in the world (e.g. Void preset has only 9 chunks by default), it will never get the icon automatically. Even if there are 11 and more those chunks there, the icon won't be created unless you look at least at 11 of them at the same time, which is sometimes impossible (e.g. they are too far from each other) or rarely achieved (e.g. you need to fly higher and then look down)
Linked issues
is duplicated by 3
Attachments
Comments 6
Can confirm for 19w42a.
Steps of reproduction:
Create a superflat save with the void preset.
Enter the save and stay in game for a while. (a day-night cycle should be enough)
Leave the game and observe that no world icon has been generated.
Join the save and quit; notice no world icon has been generated in a revisit.
Join the save again; turn on chunk borders, place or set any block in chunks (2 is enough) immediately around the chunks the starting platform is in
Move to a position where you can see both the platform and the two chunks where you've placed the blocks. Wait a while for the game to render all blocks, and then quit the game. Observe that the world icon has been generated.
If the world icon has been generated, clear world icon. Join the game again and wait for the game to render all blocks and the platform.
Quit the game again. The world icon would have been generated again.
So the bug is that when there is no block in a chunk, the game assumes that the chunk is "not rendered" while it should be considered as "rendered".
See countRenderedChunks method in LevelRenderer (name from mojang client obfuscation map for 19w42a); apparently this logic does not count a chunk that is naturally empty.
Note: the icon uploaded shows a proper setup of blocks as described in step 5 and is a correctly generated world icon as a result of this placing blocks in empty chunks around to trick the game.
Can confirm.