fix entity velocity packet fix

will now decide whether to send shorts or ints

tested on singleplayer and server, works

Author: Nischhelm

src/main/java/fermiummixins/mixin/vanilla/SPacketEntityVelocity_LimitMixin.java

@@ -1,17 +1,30 @@
 package fermiummixins.mixin.vanilla;
 
+import net.minecraft.network.PacketBuffer;
 import net.minecraft.network.play.server.SPacketEntityVelocity;
+import org.objectweb.asm.Opcodes;
 import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Shadow;
+import org.spongepowered.asm.mixin.Unique;
+import org.spongepowered.asm.mixin.injection.At;
 import org.spongepowered.asm.mixin.injection.Constant;
+import org.spongepowered.asm.mixin.injection.Inject;
 import org.spongepowered.asm.mixin.injection.ModifyConstant;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
 
 /**
  * Fix by Nischhelm
  */
+// see https://youtu.be/Q_MkxSD33Vw?si=uDKlxttiKw21lXuW&t=1335
 @Mixin(SPacketEntityVelocity.class)
 public abstract class SPacketEntityVelocity_LimitMixin {
-    
-    // see https://youtu.be/Q_MkxSD33Vw?si=uDKlxttiKw21lXuW&t=1335
+
+    @Shadow private int motionX;
+    @Shadow private int motionY;
+    @Shadow private int motionZ;
+    @Unique private boolean fermiummixins$isOverLimit = false;
+
+    //Don't clamp values to fit short limit
     @ModifyConstant(
             method = "<init>(IDDD)V",
             constant = @Constant(doubleValue = -3.9D)
@@ -27,4 +40,45 @@ private double fermiummixins_vanillaSPacketEntityVelocity_init_negLimit(double c
     private double fermiummixins_vanillaSPacketEntityVelocity_init_posLimit(double constant) {
         return Double.MAX_VALUE;
     }
+
+    //Check if over short limit (~ 8000 x +-3.9)
+    @Inject(
+            method = "<init>(IDDD)V",
+            at = @At("TAIL")
+    )
+    private void fermiummixins_vanillaSPacketEntityVelocity_init(int entityIdIn, double motionXIn, double motionYIn, double motionZIn, CallbackInfo ci) {
+        this.fermiummixins$isOverLimit = Math.abs(motionXIn) > 3.9 || Math.abs(motionYIn) > 3.9 || Math.abs(motionZIn) > 3.9;
+    }
+
+    //read extra boolean and switch to int if over limit
+    @Inject(
+            method = "readPacketData",
+            at = @At(value = "FIELD", target = "Lnet/minecraft/network/play/server/SPacketEntityVelocity;entityID:I", opcode = Opcodes.PUTFIELD, shift = At.Shift.AFTER),
+            cancellable = true
+    )
+    private void fermiummixins_vanillaSPacketEntityVelocity_readPacketData(PacketBuffer buf, CallbackInfo ci){
+        this.fermiummixins$isOverLimit = buf.readBoolean();
+        if(!this.fermiummixins$isOverLimit) return;
+
+        this.motionX = buf.readInt();
+        this.motionY = buf.readInt();
+        this.motionZ = buf.readInt();
+        ci.cancel();
+    }
+
+    //write extra boolean and switch to int if over limit
+    @Inject(
+            method = "writePacketData",
+            at = @At(value = "FIELD", target = "Lnet/minecraft/network/play/server/SPacketEntityVelocity;motionX:I", opcode = Opcodes.GETFIELD),
+            cancellable = true
+    )
+    private void fermiummixins_vanillaSPacketEntityVelocity_writePacketData(PacketBuffer buf, CallbackInfo ci){
+        buf.writeBoolean(this.fermiummixins$isOverLimit);
+        if(!this.fermiummixins$isOverLimit) return;
+
+        buf.writeInt(this.motionX);
+        buf.writeInt(this.motionY);
+        buf.writeInt(this.motionZ);
+        ci.cancel();
+    }
 }