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Fix dimension reading for some mods that add extra dimensions in 1.7.10 (#1734)

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Rewrite the comment and ternary operation to be clearer

Co-authored-by: xphorror <87706197+xphorror@users.noreply.github.com>
This commit is contained in:
Wouter Gritter
2026-08-02 11:13:25 +02:00
co-authored by xphorror
parent e11584ba35
commit 2676520c6a
1 changed files with 11 additions and 1 deletions
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proxy/src/main/java/com/velocitypowered/proxy/protocol/packet/JoinGamePacket.java
+11 -1
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@@ -245,7 +245,17 @@ public class JoinGamePacket implements MinecraftPacket {
if (version.noLessThan(ProtocolVersion.MINECRAFT_1_9_1)) {
this.dimension = buf.readInt();
} else {
this.dimension = buf.readByte();
// Vanilla 1.7.10 uses a signed byte for dimension (-1 Nether, 0 Overworld, 1 End).
// Modded servers hack this to an unsigned byte to allow dim IDs up to 255.
// We must store the canonical int here because RespawnPacket.fromJoinGame copies this
// value into a packet that encodes dimension as a 4-byte int (RespawnPacket.encode,
// pre-1.16 logic). Sign-extending a modded byte like 0xB4 to int -76 sends an
// illegal dimension ID to the client and crashes it.
//
// The wire byte is ambiguous: 0xFF could be vanilla Nether (-1) or modded dim 255.
// We resolve in Nether's favor since vanilla 1.7.10 only ever uses -1/0/1.
short raw = buf.readUnsignedByte();
this.dimension = raw == 0xFF ? -1 : raw;
}
if (version.noGreaterThan(ProtocolVersion.MINECRAFT_1_13_2)) {
this.difficulty = buf.readUnsignedByte();