Fix client physics being sluggish when opening first world

Author: embeddedt

src/main/java/org/embeddedt/archaicfix/asm/Mixin.java

@@ -64,7 +64,8 @@ public enum Mixin implements IMixins {
                     "core.MixinGuiIngameForge",
                     "core.MixinFMLClientHandler",
                     "core.MixinSplashProgress",
-                    "core.AccessorSplashProgress")),
+                    "core.AccessorSplashProgress",
+                    "core.MixinTimer")),
     RECIPE_CACHING(new ArchaicBuilder()
             .setPhase(Phase.EARLY)
             .setApplyIf(() -> ArchaicConfig.cacheRecipes)

src/main/java/org/embeddedt/archaicfix/mixins/client/core/MixinTimer.java

@@ -0,0 +1,28 @@
+package org.embeddedt.archaicfix.mixins.client.core;
+
+import net.minecraft.util.Timer;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Shadow;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+
+@Mixin(Timer.class)
+public class MixinTimer {
+    @Shadow
+    private double timeSyncAdjustment;
+
+    @Shadow
+    private long field_74285_i;
+
+    /**
+     * @author embeddedt
+     * @reason Disable vanilla's broken mechanism for trying to coordinate two clocks and just use the result of
+     * System.nanoTime() as is. This fixes the client sometimes feeling very sluggish when opening a world.
+     */
+    @Inject(method = "updateTimer", at = @At("HEAD"))
+    private void disableTimeSyncAdjustment(CallbackInfo ci) {
+        this.timeSyncAdjustment = 1.0D;
+        this.field_74285_i = 0L;
+    }
+}