Use up to 255 worker threads (matches 1.18)

src/main/java/org/embeddedt/modernfix/mixin/UtilMixin.java

@@ -0,0 +1,25 @@
+package org.embeddedt.modernfix.mixin;
+
+import net.minecraft.util.Util;
+import org.embeddedt.modernfix.ModernFix;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.Constant;
+import org.spongepowered.asm.mixin.injection.ModifyConstant;
+
+@Mixin(Util.class)
+public class UtilMixin {
+    @ModifyConstant(method = "makeExecutor", constant = @Constant(intValue = 7))
+    private static int useHigherThreadCount(int old) {
+        String requestedMax = System.getProperty("max.bg.threads");
+        if(requestedMax != null) {
+            try {
+                int newMax = Integer.parseInt(requestedMax);
+                if(newMax >= 1 && newMax <= 255)
+                    return newMax;
+            } catch(NumberFormatException e) {
+                ModernFix.LOGGER.error("max.bg.threads is not a number");
+            }
+        }
+        return 255;
+    }
+}

src/main/resources/modernfix.mixins.json

@@ -12,7 +12,8 @@
     "SaveFormatAccessor",
     "AbstractBlockStateMixin",
     "GameDataMixin",
-    "BlockCallbacksMixin"
+    "BlockCallbacksMixin",
+    "UtilMixin"
   ],
   "client": [
     "MinecraftMixin",