change world height (client only)

SuperBigWorld2023WorkingVersion.java

    @Override
    public void onPacketSending(PacketEvent event) {
        ClientboundLoginPacket packet = (ClientboundLoginPacket) event.getPacket().getHandle();
        Holder.Reference<DimensionType> dimensionType = (Holder.Reference<DimensionType>) clone((Holder.Reference<?>) packet.dimensionType(), clone(packet.dimensionType().value()));
        event.setPacket(new PacketContainer(
                PacketType.fromClass(packet.getClass()),
                new ClientboundLoginPacket(
                        packet.playerId(),
                        packet.hardcore(),
                        packet.gameType(),
                        packet.previousGameType(),
                        packet.levels(),
                        packet.registryHolder(),
                        dimensionType,
                        packet.dimension(),
                        packet.seed(),
                        packet.maxPlayers(),
                        packet.chunkRadius(),
                        packet.simulationDistance(),
                        packet.reducedDebugInfo(),
                        packet.showDeathScreen(),
                        packet.isDebug(),
                        packet.isFlat()
                )
        ));

        Bukkit.getScheduler().runTaskLater(plugin, () -> {
            Player player = Bukkit.getPlayer("WizardlyBump17");
            Location location = player.getLocation();
            player.sendBlockChange(new Location(player.getWorld(), location.getX(), 330, location.getZ()), Material.STONE.createBlockData());
        }, 100);
    }

    public static DimensionType clone(DimensionType original) {
        System.out.println(original.height() + " " + original.logicalHeight());
        return DimensionType.create(
                getField(DimensionType.class, original, "w"), //fixedTime
                original.hasSkyLight(),
                original.hasCeiling(),
                original.ultraWarm(),
                original.natural(),
                original.coordinateScale(),
                original.createDragonFight(),
                original.piglinSafe(),
                original.bedWorks(),
                original.respawnAnchorWorks(),
                original.hasRaids(),
                -64, //original.minY()
                384 + 16, //original.height() big values the client takes more to pass the "Loading terrain...". I tested it with 512
                384 + 16, //original.logicalHeight()
                original.infiniburn(),
                original.effectsLocation(),
                original.brightness(0)
        );
    }

    public static Holder.Reference<?> clone(Holder.Reference<?> original, Object value) {
        Holder.Reference<?> newHolder = Holder.Reference.createStandAlone(getField(Holder.Reference.class, original, "a"), original.key()); //registry

        setField(Holder.Reference.class, newHolder, "b", getField(Holder.Reference.class, original, "b")); //tags
        setField(Holder.Reference.class, newHolder, "e", value); //value

        return newHolder;
    }

    public static <T> T getField(Class<?> clazz, Object instance, String fieldName) {
        try {
            Field field = clazz.getDeclaredField(fieldName);
            field.setAccessible(true);
            return (T) field.get(instance);
        } catch (NoSuchFieldException | IllegalAccessException e) {
            e.printStackTrace();
        }
        return null;
    }

    public static void setField(Class<?> clazz, Object instance, String fieldName, Object value) {
        try {
            Field field = clazz.getDeclaredField(fieldName);
            field.setAccessible(true);
            field.set(instance, value);
        } catch (NoSuchFieldException | IllegalAccessException e) {
            e.printStackTrace();
        }
    }