Fix vanilla entity update packet handling (fixes #607)

src/main/java/com/replaymod/core/versions/MCVer.java

@@ -13,6 +13,12 @@ import net.minecraft.client.gui.screen.Screen;
 import net.minecraft.client.render.BufferBuilder;
 import net.minecraft.util.Identifier;
 import net.minecraft.util.Util;
+import net.minecraft.util.math.Vec3d;
+
+//#if MC>=11604
+//#else
+//$$ import net.minecraft.entity.Entity;
+//#endif
 
 //#if MC>=11600
 import net.minecraft.resource.ResourcePackSource;
@@ -55,7 +61,6 @@ import org.lwjgl.glfw.GLFW;
 //#if MC>=10904
 import com.replaymod.render.blend.mixin.ParticleAccessor;
 import net.minecraft.client.particle.Particle;
-import net.minecraft.util.math.Vec3d;
 //#endif
 
 //#if MC>=10800
@@ -297,6 +302,12 @@ public class MCVer {
     }
     //#endif
 
+    //#if MC<=11601
+    //$$ public static Vec3d getTrackedPosition(Entity entity) {
+    //$$     return new Vec3d(entity.trackedX, entity.trackedY, entity.trackedZ);
+    //$$ }
+    //#endif
+
     public static void openFile(File file) {
         //#if MC>=11400
         Util.getOperatingSystem().open(file);

src/main/java/com/replaymod/core/versions/Patterns.java

@@ -21,6 +21,7 @@ import net.minecraft.entity.Entity;
 import net.minecraft.entity.player.PlayerEntity;
 import net.minecraft.network.PacketByteBuf;
 import net.minecraft.util.Identifier;
+import net.minecraft.util.math.Vec3d;
 import net.minecraft.world.World;
 import net.minecraft.world.chunk.WorldChunk;
 
@@ -563,4 +564,13 @@ class Patterns {
         return new CrashException(((MinecraftAccessor) mc).getCrashReporter());
         //#endif
     }
+
+    @Pattern
+    private static Vec3d getTrackedPosition(Entity entity) {
+        //#if MC>=11604
+        return entity.getTrackedPosition();
+        //#else
+        //$$ return com.replaymod.core.versions.MCVer.getTrackedPosition(entity);
+        //#endif
+    }
 }

src/main/java/com/replaymod/replay/ext/EntityExt.java

@@ -0,0 +1,9 @@
+package com.replaymod.replay.ext;
+
+public interface EntityExt {
+    float replaymod$getTrackedYaw();
+    void replaymod$setTrackedYaw(float value);
+
+    float replaymod$getTrackedPitch();
+    void replaymod$setTrackedPitch(float value);
+}

src/main/java/com/replaymod/replay/mixin/entity_tracking/Mixin_EntityExt.java

@@ -0,0 +1,36 @@
+package com.replaymod.replay.mixin.entity_tracking;
+
+import com.replaymod.replay.ext.EntityExt;
+import net.minecraft.entity.Entity;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Unique;
+
+@Mixin(Entity.class)
+public abstract class Mixin_EntityExt implements EntityExt {
+
+    @Unique
+    private float trackedYaw;
+
+    @Unique
+    private float trackedPitch;
+
+    @Override
+    public float replaymod$getTrackedYaw() {
+        return this.trackedYaw;
+    }
+
+    @Override
+    public float replaymod$getTrackedPitch() {
+        return this.trackedPitch;
+    }
+
+    @Override
+    public void replaymod$setTrackedYaw(float value) {
+        this.trackedYaw = value;
+    }
+
+    @Override
+    public void replaymod$setTrackedPitch(float value) {
+        this.trackedPitch = value;
+    }
+}

src/main/java/com/replaymod/replay/mixin/entity_tracking/Mixin_FixPartialUpdates.java

@@ -0,0 +1,109 @@
+package com.replaymod.replay.mixin.entity_tracking;
+
+import com.replaymod.replay.ext.EntityExt;
+import net.minecraft.client.network.ClientPlayNetworkHandler;
+import net.minecraft.entity.Entity;
+import org.objectweb.asm.Opcodes;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Unique;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.ModifyArg;
+import org.spongepowered.asm.mixin.injection.ModifyVariable;
+import org.spongepowered.asm.mixin.injection.Redirect;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+
+/**
+ * Every Entity on the client has at least two position/rotation states: The local one and the server ("tracked") one.
+ * When receiving an update from the server, the server one needs to be updated and the local one will then usually be
+ * interpolated to the server one within a few ticks.
+ *
+ * Minecraft however incorrectly implements the server rotation update for position-only update packets by
+ * interpolating to the local rotation, which might not yet match the server rotation, rather than to the previously
+ * received server rotation.
+ * Similarly, with 1.15 and later, it incorrectly implements the server position update for rotation-only update packets
+ * by interpolating to the local position rather than the server one.
+ *
+ * Each of these will cause the client position to be in an incorrect state until the next update packed for the
+ * respective rotation/position of that entity.
+ *
+ * This mixin fixes those two issues by redirecting to the server rotation/position respectively.
+ * Minecraft does not currently even track the server rotation, so we need to do that as well.
+ */
+@Mixin(ClientPlayNetworkHandler.class)
+public class Mixin_FixPartialUpdates {
+
+    //
+    // Use correct rotation for position-only updates
+    //
+
+    //#if MC>=11700
+    //$$ @Redirect(method = "onEntityUpdate", at = @At(value = "INVOKE", target = "Lnet/minecraft/entity/Entity;getYaw()F"))
+    //#else
+    @Redirect(method = "onEntityUpdate", at = @At(value = "FIELD", target = "Lnet/minecraft/entity/Entity;yaw:F", opcode = Opcodes.GETFIELD))
+    //#endif
+    private float getTrackedYaw(Entity instance) {
+        return ((EntityExt) instance).replaymod$getTrackedYaw();
+    }
+
+    //#if MC>=11700
+    //$$ @Redirect(method = "onEntityUpdate", at = @At(value = "INVOKE", target = "Lnet/minecraft/entity/Entity;getPitch()F"))
+    //#else
+    @Redirect(method = "onEntityUpdate", at = @At(value = "FIELD", target = "Lnet/minecraft/entity/Entity;pitch:F", opcode = Opcodes.GETFIELD))
+    //#endif
+    private float getTrackedPitch(Entity instance) {
+        return ((EntityExt) instance).replaymod$getTrackedPitch();
+    }
+
+    //#if MC>=11500
+    //
+    // Use correct position for rotation-only updates
+    //
+
+    @Redirect(method = "onEntityUpdate", at = @At(value = "INVOKE", target = "Lnet/minecraft/entity/Entity;getX()D"))
+    private double getTrackedX(Entity instance) {
+        return instance.getTrackedPosition().getX();
+    }
+
+    @Redirect(method = "onEntityUpdate", at = @At(value = "INVOKE", target = "Lnet/minecraft/entity/Entity;getY()D"))
+    private double getTrackedY(Entity instance) {
+        return instance.getTrackedPosition().getY();
+    }
+
+    @Redirect(method = "onEntityUpdate", at = @At(value = "INVOKE", target = "Lnet/minecraft/entity/Entity;getZ()D"))
+    private double getTrackedZ(Entity instance) {
+        return instance.getTrackedPosition().getZ();
+    }
+    //#endif
+
+    //
+    // Track server rotation
+    //
+
+    private static final String ENTITY_UPDATE = "Lnet/minecraft/entity/Entity;updateTrackedPositionAndAngles(DDDFFIZ)V";
+
+    @Unique
+    private Entity entity;
+
+    @ModifyVariable(method = "onEntityUpdate", at = @At(value = "INVOKE", target = ENTITY_UPDATE), ordinal = 0)
+    private Entity captureEntity(Entity entity) {
+        return this.entity = entity;
+    }
+
+    @Inject(method = "onEntityUpdate", at = @At("RETURN"))
+    private void resetEntityField(CallbackInfo ci) {
+        this.entity = null;
+    }
+
+    @ModifyArg(method = "onEntityUpdate", at = @At(value = "INVOKE", target = ENTITY_UPDATE), index = 3)
+    private float captureTrackedYaw(float value) {
+        ((EntityExt) this.entity).replaymod$setTrackedYaw(value);
+        return value;
+    }
+
+    @ModifyArg(method = "onEntityUpdate", at = @At(value = "INVOKE", target = ENTITY_UPDATE), index = 4)
+    private float captureTrackedPitch(float value) {
+        ((EntityExt) this.entity).replaymod$setTrackedPitch(value);
+        return value;
+    }
+}