repeated AnvilUpdateEvent

[SViking]

When subscribing to the AnvilUpdateEvent, I seem to be getting multiple events for a single action of filling the left and right slots on the anvil.  This is for Forge 1.9-12.16.0.1811-1.9.  Am I doing something wrong here, is this a bug or other?  Here's my test code and output from one test run:

 

Main class:

 

package com.sviking.practicalanvil;

import com.sviking.practicalanvil.event.PAEventHandler;

import net.minecraftforge.common.MinecraftForge;
import net.minecraftforge.fml.common.FMLCommonHandler;
import net.minecraftforge.fml.common.Mod;
import net.minecraftforge.fml.common.Mod.EventHandler;
import net.minecraftforge.fml.common.Mod.Instance;
import net.minecraftforge.fml.common.event.FMLInitializationEvent;
import net.minecraftforge.fml.common.event.FMLPostInitializationEvent;
import net.minecraftforge.fml.common.event.FMLPreInitializationEvent;

@Mod(modid = Main.MODID, name = Main.MODNAME, version = Main.VERSION)
public class Main {

    public static final String MODID = "practicalanvil";
    public static final String MODNAME = "Practical Anvil Mod";
    public static final String VERSION = "1.0.0";

    @Instance
    public static Main instance = new Main();
   
    @EventHandler
    public void preInit(FMLPreInitializationEvent e) {

    }

    @EventHandler
    public void init(FMLInitializationEvent e) {
       MinecraftForge.EVENT_BUS.register(new PAEventHandler());
    }

    @EventHandler
    public void postInit(FMLPostInitializationEvent e) {

    }
} 

 

 

Event handler:

 

package com.sviking.practicalanvil.event;

import net.minecraftforge.event.AnvilUpdateEvent;
import net.minecraftforge.event.entity.player.AnvilRepairEvent;
import net.minecraftforge.fml.common.eventhandler.EventPriority;
import net.minecraftforge.fml.common.eventhandler.SubscribeEvent;

public class PAEventHandler {
    @SubscribeEvent
    public void onAnvilUpdate(AnvilUpdateEvent e) {
    System.out.println(e);
    e.setCanceled(true);
    }
}

 

Sample output (single action of filling left and right slots):

 

[21:42:28] [Client thread/INFO] [sTDOUT]: [com.sviking.practicalanvil.event.PAEventHandler:onAnvilUpdate:11]: net.minecraftforge.event.AnvilUpdateEvent@384bd992
[21:42:28] [Client thread/INFO] [sTDOUT]: [com.sviking.practicalanvil.event.PAEventHandler:onAnvilUpdate:11]: net.minecraftforge.event.AnvilUpdateEvent@10fae499
[21:42:28] [Client thread/INFO] [sTDOUT]: [com.sviking.practicalanvil.event.PAEventHandler:onAnvilUpdate:11]: net.minecraftforge.event.AnvilUpdateEvent@259a9966
[21:42:28] [server thread/INFO] [sTDOUT]: [com.sviking.practicalanvil.event.PAEventHandler:onAnvilUpdate:11]: net.minecraftforge.event.AnvilUpdateEvent@b0f027e
[21:42:28] [server thread/INFO] [sTDOUT]: [com.sviking.practicalanvil.event.PAEventHandler:onAnvilUpdate:11]: net.minecraftforge.event.AnvilUpdateEvent@3505b6d9
[21:42:28] [server thread/INFO] [sTDOUT]: [com.sviking.practicalanvil.event.PAEventHandler:onAnvilUpdate:11]: net.minecraftforge.event.AnvilUpdateEvent@6eef4800
[21:42:28] [Client thread/INFO] [sTDOUT]: [com.sviking.practicalanvil.event.PAEventHandler:onAnvilUpdate:11]: net.minecraftforge.event.AnvilUpdateEvent@7b7ef483
[21:42:28] [Client thread/INFO] [sTDOUT]: [com.sviking.practicalanvil.event.PAEventHandler:onAnvilUpdate:11]: net.minecraftforge.event.AnvilUpdateEvent@1d9f2537

 

I'll also note that the number of events generated varies from as few as 4 to as many as 10.

 

I've experienced similar behavior with AnvilRepairEvent, though not as extreme.

 

Thanks in advance.

[jeffryfisher]

I noticed the same thing happening when I subscribed to this event in order to repair or apply enchanted books to my ruby shears. I had to remove my status msg because it would fire so many times.

 

I haven't analyzed it, but it smells like a thread or client-server sync issue. Perhaps the condition that fires the event exists every tick until some interprocess communication clears it. The variability of the msg count suggests that lag contributes to it.

 

If so, then it's likely a vanilla minecraft "feature" that we can't fix. However, if there's a fix or workaround, then I'd be interested.

[Draco18s]

Have you checked...?

 

1) To see if

AnvilUpdateEvent

has any sub events?

2) To see where

AnvilUpdateEvent

is fired?

[SViking]

Thanks for the reply.  Of course, some of the repeating in my test due to execution on both client and server.  However, my laziness was fortuitous, as I sometimes saw a different number of events on one side vs the other.  That would further support your notion of the event firing on multiple ticks, with lag as a contributor.

 

I'm digging a little more into the Forge hook that allows the anvil events to see if there's a possible resolution.  At least I know now I'm not chasing my own tail.

 

Applying 30 years coding experience to learning Java/Eclipse via mc-Forge modding.

 

Haha...same here!

[SViking]

Have you checked...?

 

1) To see if

AnvilUpdateEvent

has any sub events?

 

 

It doesn't appear to have any sub events.

 

2) To see where

AnvilUpdateEvent

is fired?

 

The Forge hook is onAnvilChange(...) which is called from within ContainerRepair.updateRepairOutput().  Each event does appear to be a separate call from this same point.  That's as much as I've determined so far.

[jeffryfisher]

Right -- And that means that vanilla Minecraft is calling its own container repair method multiple times, so I don't think its a Forge or mod problem. It's almost certainly some code weakness within Vanilla Minecraft.

 

However, don't even bother reporting a bug to Mojang. They reject all bug-reports based on modder's examinations of their internals. If it doesn't crash the game or produce some other visible effect, then they're not interested.