src/main/java/ftbsc/bscv/patches/BackgroundPatch.java


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package ftbsc.bscv.patches;

import ftbsc.bscv.ICommons;
import ftbsc.lll.processor.annotations.Injector;
import ftbsc.lll.processor.annotations.Patch;
import ftbsc.lll.processor.annotations.Target;
import ftbsc.lll.tools.InsnSequence;
import ftbsc.lll.tools.PatternMatcher;
import ftbsc.lll.tools.debug.BytecodePrinter;
import net.minecraft.client.gui.screen.Screen;
import net.minecraftforge.common.MinecraftForge;
import net.minecraftforge.eventbus.api.Cancelable;
import net.minecraftforge.eventbus.api.Event;

import org.objectweb.asm.Opcodes;
import org.objectweb.asm.tree.*;

import com.mojang.blaze3d.matrix.MatrixStack;

public class BackgroundPatch implements ICommons {

   public static boolean shouldDrawBackground(Screen screen) {
      return MinecraftForge.EVENT_BUS.post(new RenderBackgroundEvent(screen));
   }

   @Cancelable
   public static class RenderBackgroundEvent extends Event {
      public final Screen screen;

      public RenderBackgroundEvent(Screen screen) {
         this.screen = screen;
      }
   }

   @Patch(value = Screen.class, reason = "add hook to cancel background on some screens")
   public abstract static class BackgroundOverride implements Opcodes {
      @Target
      abstract void renderBackground(MatrixStack stack, int x);

      @Injector
      public void inject(ClassNode clazz, MethodNode main) {
         AbstractInsnNode found = PatternMatcher.builder()
            .opcodes(ALOAD, ALOAD, ICONST_0, ICONST_0)
            .ignoreFrames()
            .ignoreLabels()
            .ignoreLineNumbers()
            .build()
            .find(main)
            // .getFirst(); // TODO returns first InsnNode of method instead of match?
            .getLast().getPrevious().getPrevious().getPrevious();

         LabelNode skip = new LabelNode();
         InsnSequence is = new InsnSequence();
         is.add(new VarInsnNode(ALOAD, 0));
         is.add(new MethodInsnNode(
            INVOKESTATIC,
            "ftbsc/bscv/patches/BackgroundPatch$BackgroundHook",
            "shouldDrawBackground",
            "(Lnet/minecraft/client/gui/screen/Screen;)Z"
         ));
         is.add(new JumpInsnNode(IFEQ, skip));
         is.add(new InsnNode(RETURN));
         is.add(skip);

         main.instructions.insertBefore(found, is);
      }
   }
}