Latch JEI and blockstate threads until the world finishes loading

These processes are not necessary to get into the game, and so
we want to devote all CPU time to essential tasks like logging in
and loading chunks.

src/main/java/org/embeddedt/modernfix/ModernFix.java

@@ -21,6 +21,10 @@ import org.embeddedt.modernfix.structure.AsyncLocator;
 import org.embeddedt.modernfix.util.KubeUtil;
 
 import java.lang.management.ManagementFactory;
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.Semaphore;
+import java.util.concurrent.TimeUnit;
+import java.util.function.BooleanSupplier;
 
 // The value here should match an entry in the META-INF/mods.toml file
 @Mod(ModernFix.MODID)
@@ -36,6 +40,26 @@ public class ModernFix {
     // Used to skip computing the blockstate caches twice
     public static boolean runningFirstInjection = false;
 
+    public static CountDownLatch worldLoadSemaphore = null;
+
+    /**
+     * Simple mechanism used to delay some background processes until the client is actually in-game, to reduce
+     * launch time.
+     */
+    public static void waitForWorldLoad(BooleanSupplier exitEarly) {
+        CountDownLatch latch = worldLoadSemaphore;
+        if(latch != null) {
+            try {
+                while(!latch.await(100, TimeUnit.MILLISECONDS)) {
+                    if(exitEarly.getAsBoolean())
+                        return;
+                }
+            } catch(InterruptedException e) {
+                Thread.currentThread().interrupt();
+            }
+        }
+    }
+
 
     public ModernFix() {
         INSTANCE = this;

src/main/java/org/embeddedt/modernfix/ModernFixClient.java

@@ -48,6 +48,8 @@ public class ModernFixClient {
             ModernFix.LOGGER.warn("Time from main menu to in-game was " + timeSpentLoading + " seconds");
             ModernFix.LOGGER.warn("Total time to load game and open world was " + (timeSpentLoading + gameStartTimeSeconds) + " seconds");
             resetWorldLoadStateMachine();
+            if(ModernFix.worldLoadSemaphore != null)
+                ModernFix.worldLoadSemaphore.countDown();
         }
     }
 }

src/main/java/org/embeddedt/modernfix/blockstate/BlockStateCacheHandler.java

@@ -85,6 +85,9 @@ public class BlockStateCacheHandler {
 
         @Override
         public void run() {
+            ModernFix.waitForWorldLoad(() -> stopRebuild);
+            if(stopRebuild)
+                return;
             Stopwatch realtimeStopwatch = Stopwatch.createStarted();
             rebuildCache();
             realtimeStopwatch.stop();

src/main/java/org/embeddedt/modernfix/mixin/core/MinecraftMixin.java

@@ -0,0 +1,25 @@
+package org.embeddedt.modernfix.mixin.core;
+
+import com.mojang.datafixers.util.Function4;
+import net.minecraft.client.Minecraft;
+import net.minecraft.core.RegistryAccess;
+import net.minecraft.server.packs.resources.ResourceManager;
+import net.minecraft.world.level.DataPackConfig;
+import net.minecraft.world.level.storage.LevelStorageSource;
+import net.minecraft.world.level.storage.WorldData;
+import org.embeddedt.modernfix.ModernFix;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+
+import java.util.concurrent.CountDownLatch;
+import java.util.function.Function;
+
+@Mixin(Minecraft.class)
+public class MinecraftMixin {
+    @Inject(method = "loadWorld", at = @At("HEAD"))
+    private void setLatch(String string, RegistryAccess.RegistryHolder arg, Function<LevelStorageSource.LevelStorageAccess, DataPackConfig> function, Function4<LevelStorageSource.LevelStorageAccess, RegistryAccess.RegistryHolder, ResourceManager, DataPackConfig, WorldData> function4, boolean bl, Minecraft.ExperimentalDialogType arg2, boolean creating, CallbackInfo ci) {
+        ModernFix.worldLoadSemaphore = new CountDownLatch(1);
+    }
+}

src/main/java/org/embeddedt/modernfix/mixin/perf/async_jei/ClientLifecycleHandlerMixin.java

@@ -80,6 +80,9 @@ public class ClientLifecycleHandlerMixin {
         cancelPreviousStart();
         ModernFix.LOGGER.info("Starting new JEI thread.");
         JEIReloadThread newThread = new JEIReloadThread(() -> {
+            ModernFix.waitForWorldLoad(() -> ((JEIReloadThread)Thread.currentThread()).isStopRequested());
+            if(((JEIReloadThread)Thread.currentThread()).isStopRequested())
+                return;
             try {
                 starter.start(
                         plugins,

src/main/resources/modernfix.mixins.json

@@ -50,6 +50,7 @@
     "perf.kubejs.CustomIngredientMixin"
   ],
   "client": [
+    "core.MinecraftMixin",
     "feature.measure_time.MinecraftMixin",
     "feature.reduce_loading_screen_freezes.ModelBakeryMixin",
     "perf.skip_first_datapack_reload.MinecraftMixin",