Temporarily shift splash screen control to background thread during registry events

forge/src/main/java/org/embeddedt/modernfix/forge/mixin/bugfix/loading_screen_freeze/GameDataMixin.java

@@ -0,0 +1,20 @@
+package org.embeddedt.modernfix.forge.mixin.bugfix.loading_screen_freeze;
+
+import com.llamalad7.mixinextras.injector.wrapoperation.Operation;
+import com.llamalad7.mixinextras.injector.wrapoperation.WrapOperation;
+import net.minecraftforge.eventbus.api.Event;
+import net.minecraftforge.fml.ModLoader;
+import net.minecraftforge.registries.GameData;
+import org.embeddedt.modernfix.forge.util.AsyncLoadingScreen;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+
+@Mixin(value = GameData.class, remap = false)
+public class GameDataMixin {
+    @WrapOperation(method = "postRegisterEvents", at = @At(value = "INVOKE", target = "Lnet/minecraftforge/fml/ModLoader;postEventWrapContainerInModOrder(Lnet/minecraftforge/eventbus/api/Event;)V"))
+    private static void swapThreadAndPost(ModLoader loader, Event event, Operation<Void> operation) {
+        try(AsyncLoadingScreen ignored = new AsyncLoadingScreen()) {
+            operation.call(loader, event);
+        }
+    }
+}

forge/src/main/java/org/embeddedt/modernfix/forge/util/AsyncLoadingScreen.java

@@ -0,0 +1,53 @@
+package org.embeddedt.modernfix.forge.util;
+
+import net.minecraftforge.fml.loading.ImmediateWindowHandler;
+import org.lwjgl.glfw.GLFW;
+import org.lwjgl.opengl.GL;
+
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.locks.LockSupport;
+
+public class AsyncLoadingScreen extends Thread implements AutoCloseable {
+    private final long theWindow;
+    private final AtomicBoolean keepRunning;
+
+    private static int splashThreadNum = 1;
+
+    public AsyncLoadingScreen() {
+        this.setName("ModernFix splash thread " + splashThreadNum++);
+        this.theWindow = GLFW.glfwGetCurrentContext();
+        if(this.theWindow == 0)
+            throw new IllegalStateException("No context found but async loading screen was requested");
+        this.keepRunning = new AtomicBoolean(true);
+        this.start();
+    }
+
+    @Override
+    public synchronized void start() {
+        GLFW.glfwMakeContextCurrent(0);
+        super.start();
+    }
+
+    @Override
+    public void run() {
+        GLFW.glfwMakeContextCurrent(theWindow);
+        GL.createCapabilities(); // seems to be needed, otherwise we get a "function not valid for context" error
+        while(keepRunning.get()) {
+            LockSupport.parkNanos(TimeUnit.MILLISECONDS.toNanos(50));
+            ImmediateWindowHandler.renderTick();
+        }
+        GLFW.glfwMakeContextCurrent(0);
+    }
+
+    @Override
+    public void close() {
+        keepRunning.set(false);
+        try {
+            this.join();
+        } catch(InterruptedException e) {
+            Thread.currentThread().interrupt();
+        }
+        GLFW.glfwMakeContextCurrent(theWindow);
+    }
+}