Hello there. I'm writing a mod, and I need to modify minecraft's code so I can see barrier blocks depending on my method's result. So there's a singleton with one method specifically for this, called like this (returns bool):
 

AlwaysShowBarriersManager.instance().isEnabled()

 

Minecraft code, responsible for displaying barrier particles is in the "net.minecraft.client.multiplayer.WorldClient" class:

public void doVoidFogParticles(int p_doVoidFogParticles_1_, int p_doVoidFogParticles_2_, int p_doVoidFogParticles_3_) {
        int i = 16;
        Random random = new Random();
        ItemStack itemstack = this.mc.thePlayer.getHeldItem();
        boolean flag = this.mc.playerController.getCurrentGameType() == GameType.CREATIVE && itemstack != null && Block.getBlockFromItem(itemstack.getItem()) == Blocks.barrier;
        MutableBlockPos blockpos$mutableblockpos = new MutableBlockPos();

        for(int j = 0; j < 1000; ++j) {
            int k = p_doVoidFogParticles_1_ + this.rand.nextInt(i) - this.rand.nextInt(i);
            int l = p_doVoidFogParticles_2_ + this.rand.nextInt(i) - this.rand.nextInt(i);
            int i1 = p_doVoidFogParticles_3_ + this.rand.nextInt(i) - this.rand.nextInt(i);
            blockpos$mutableblockpos.set(k, l, i1);
            IBlockState iblockstate = this.getBlockState(blockpos$mutableblockpos);
            iblockstate.getBlock().randomDisplayTick(this, blockpos$mutableblockpos, iblockstate, random);
            if (flag && iblockstate.getBlock() == Blocks.barrier) {
                this.spawnParticle(EnumParticleTypes.BARRIER, (double)((float)k + 0.5F), (double)((float)l + 0.5F), (double)((float)i1 + 0.5F), 0.0D, 0.0D, 0.0D, new int[0]);
            }
        }

    }

 

So what I want to do is alter "flag" variable, like this:

 

boolean flag =
                (this.mc.playerController.getCurrentGameType() == GameType.CREATIVE && itemstack != null && Block.getBlockFromItem(itemstack.getItem()) == Blocks.barrier) ||
                        my.mod.package.AlwaysShowBarriersManager.instance().isEnabled();

or

if(!flag) {
	flag = my.mod.package.AlwaysShowBarriersManager.instance().isEnabled();
}

 

Both solutions would work. What I usually do with coremod's ClassTransformers is I copy the whole class into same package in my mod's src folder, then modify what I need and ASMify it using IDEA plugin. I receive such code in result:

mv = cw.visitMethod(ACC_PUBLIC, "doVoidFogParticles", "(III)V", null, null);
mv.visitCode();
// blablabla
mv.visitEnd();

My ClassTransformer's transform method looks like this (simplified):

ClassNode classNode = new ClassNode();
ClassReader classReader = new ClassReader(bytes);
ClassWriter classWriter = new ClassWriter(ClassWriter.COMPUTE_FRAMES | ClassWriter.COMPUTE_MAXS);

classReader.accept(classNode, ClassReader.EXPAND_FRAMES);

// find needed method

MethodVisitor mv = classWriter.visitMethod(); // arguments blablabla

// visit code

classReader.accept(methodReplacer, ClassReader.EXPAND_FRAMES);

return classWriter.toByteArray();

 

If I try to run this, the game crashes: https://pastebin.com/0hp3EsqU

Auto-generated "visit code": https://pastebin.com/ivuabcZv

 

What am I missing here? I know that I shouldn't use coremods, but there's no way around it, so I'm forced to use them.

Don't make coremods.

5 minutes ago, Alex_Wells said:

What am I missing here? I know that I shouldn't use coremods, but there's no way around it, so I'm forced to use them.

Coremods are not supported on this forum, a moderator will most likely close this thread.

Just now, Animefan8888 said:

Coremods are not supported on this forum, a moderator will most likely close this thread.

Is there any other way I can get help with coremods?

Just now, diesieben07 said:

Especially not if you don't know what you are doing.

And yes, your approach to this shows that you absolutely do not know what you are doing. Don't go around replacing entire methods.

At first I just wanted to replace couple instructions with my own, but I'm kind of lazy to rewrite my whole "method transformer" system in order to achieve that. And I feel like this won't fix the problem =/