how to properly change the world from a client event?

[JoeStrout 1]

(I apologize for all the questions this week... I'm sure things will "click" for me soon, and later when I know what I'm doing, I promise to repay my karma by helping newbies whenever I can!)

 

I have a ClientChatEvent handler from which I wish to change the world — for starters, just clear a block to air.  I have no trouble telling what block the user is looking at, and I can call world.setBlockToAir and it clears the block locally... but it fails to do an update (so water doesn't flow into the new hole, for example), and of course this is a blatant siding violation.

 

 

But though I think I understand the concept of sides — and the rule that any world changes need to happen on the logical server — I'm still clueless as to how to actually do that.  One post I found here recommended wrapping any state changes in if (!world.isRemote), but when I do that, then world.setBlockToAir simply doesn't get called at all.   Current, non-working code looks like this:

 	@SubscribeEvent
 	public static void onChat(ClientChatEvent event) {
 		String msg = event.getMessage();
 		if (msg.equals("/evanesco")) {
 			// Vanish whatever we're pointed at
 			RayTraceResult trace = PointingAt();   // (helper method, don't worry about it)
 			if (trace == null || trace.typeOfHit == RayTraceResult.Type.MISS) {
 	 			SendStatus("§6Whiff!§r");	 				
 			} else {
 				BlockPos pos = trace.getBlockPos();
                // sort-of works, but is a siding violation, and doesn't update water etc:
				//Minecraft.getMinecraft().world.setBlockToAir(pos);
                // attempt to do it more properly:
 				WorldClient world = Minecraft.getMinecraft().world; 
                if (!world.isRemote) {
                		world.setBlockToAir(pos);
                		System.out.println("Set block to air on the server");
                } else {
                		// (this is what actually happens in my tests)
                		System.out.println("Not on the server, so doing nothing");
                }
                world.playSound(Minecraft.getMinecraft().player, pos, SoundEvents.ENTITY_ENDERMEN_TELEPORT, SoundCategory.PLAYERS, 1.0F, 1.0F);
 				SendStatus("§5Shoop!§r");
 			}
 			event.setCanceled(true);
 		}
 	}

 

Can anyone point me in the right direction for going from my client-side event detection, to changing block states on the server?

[diesieben07 7203]

ClientChatEvent is just that, client-sided. That means, it fires when the client thread receives a new chat message. To detect a message on the server thread, you need to use ServerChatEvent.

However in this case it looks like you are actually trying to make a command, which would be better achieved by making an actual command class. Extend CommandBase and register it in the FML lifecycle event FMLServerStartingEvent, which has a registerCommand method.

 

Another note about World::isRemote: it checks whether the world is a client-side world. But this is only useful  if you don't know the side. But since you just obtained the client world one line earlier, this check is pointless, the world is always going to be client-side (i.e. isRemote is always going to be true).

Edited December 28, 2017 by diesieben07

[Draco18s 2280]

39 minutes ago, diesieben07 said:

But since you just obtained the client world one line earlier

The key bit there being WorldClient world

[JoeStrout 1]

That all makes great sense.  And it's good to know about registering commands — while I'm currently just doing quick hacks to explore various bits of the API, I may as well do them properly!

 

[Differentiation 28]

13 hours ago, JoeStrout said:

(I apologize for all the questions this week... I'm sure things will "click" for me soon, and later when I know what I'm doing, I promise to repay my karma by helping newbies whenever I can!)

 

I have a ClientChatEvent handler from which I wish to change the world — for starters, just clear a block to air.  I have no trouble telling what block the user is looking at, and I can call world.setBlockToAir and it clears the block locally... but it fails to do an update (so water doesn't flow into the new hole, for example), and of course this is a blatant siding violation.

 

 

But though I think I understand the concept of sides — and the rule that any world changes need to happen on the logical server — I'm still clueless as to how to actually do that.  One post I found here recommended wrapping any state changes in if (!world.isRemote), but when I do that, then world.setBlockToAir simply doesn't get called at all.   Current, non-working code looks like this:

 	@SubscribeEvent
 	public static void onChat(ClientChatEvent event) {
 		String msg = event.getMessage();
 		if (msg.equals("/evanesco")) {
 			// Vanish whatever we're pointed at
 			RayTraceResult trace = PointingAt();   // (helper method, don't worry about it)
 			if (trace == null || trace.typeOfHit == RayTraceResult.Type.MISS) {
 	 			SendStatus("§6Whiff!§r");	 				
 			} else {
 				BlockPos pos = trace.getBlockPos();
                // sort-of works, but is a siding violation, and doesn't update water etc:
				//Minecraft.getMinecraft().world.setBlockToAir(pos);
                // attempt to do it more properly:
 				WorldClient world = Minecraft.getMinecraft().world; 
                if (!world.isRemote) {
                		world.setBlockToAir(pos);
                		System.out.println("Set block to air on the server");
                } else {
                		// (this is what actually happens in my tests)
                		System.out.println("Not on the server, so doing nothing");
                }
                world.playSound(Minecraft.getMinecraft().player, pos, SoundEvents.ENTITY_ENDERMEN_TELEPORT, SoundCategory.PLAYERS, 1.0F, 1.0F);
 				SendStatus("§5Shoop!§r");
 			}
 			event.setCanceled(true);
 		}
 	}

 

Can anyone point me in the right direction for going from my client-side event detection, to changing block states on the server?

Comments for feedback:

1. Since you are handling block replacements, you need to use ServerChatEvent instead of ClientChatEvent.

2. You can just make a new command and register it. execute(MinecraftServer server, ICommandSender sender, String[] args) throws CommandException method is executed in server-side.

3. Don't use Minecraft.getMinecraft() in server-side once you get the server to run the code, this might crash you or cause errors if on a server.

4. Don't use WorldClient, simply use playerIn.world once you have EntityPlayerMP through CommandBase in execute(...) method.

 

Follow these tips and you'll be set!

...
        @Override
        public String getCommandName()
        {
            return "evanesco";
        }

	@Override
 	public void execute(MinecraftServer serverIn, ICommandSender senderIn, String[] args) throws CommandException
    	{
      	    EntityPlayer playerIn = CommandBase.getCommandSenderAsPlayer(senderIn);
 	    RayTraceResult trace = PointingAt();
 			
 	    if (trace == null || trace.typeOfHit == RayTraceResult.Type.MISS) 
 	    {
 	 	SendStatus("§6Whiff!§r");	 				
 	    } 
 	    else 
 	    {
 		BlockPos pos = trace.getBlockPos();
 			
 		World worldIn = playerIn.world;
            	worldIn.setBlockToAir(pos);
            	worldIn.playSound(/* if you want sound to play for all players */ null /* else if only for this player, playerIn */, pos, SoundEvents.ENTITY_ENDERMEN_TELEPORT, SoundCategory.PLAYERS, 1.0F, 1.0F);
 			
 		SendStatus("§5Shoop!§r");
		CommandBase.notifyCommandListener("commands.evanesco.success", new Object[0]);
            }
    	}
...

I stripped the code for you, if you wish to use it, you may.

 

I hope I helped. Happy modding!

Edited December 29, 2017 by Differentiation

[Differentiation 28]

18 hours ago, JoeStrout said:

PointingAt()

What is in this method? Please show the contents.

Thanks!

[JoeStrout 1]

9 hours ago, Differentiation said:

What is in this method? Please show the contents.

Thanks!

Sure, I'd be delighted to actually be on the helpful end around here for a change. 

	// Get a RayTraceResult describing whatever the player's looking at (within 32 blocks).
	private static RayTraceResult PointingAt(boolean stopOnLiquid) {
		WorldClient world = Minecraft.getMinecraft().world;
		EntityPlayerSP player = Minecraft.getMinecraft().player;
		Vec3d posVec = new Vec3d(player.posX, player.posY + player.getEyeHeight(), player.posZ);
		Vec3d lookVec = player.getLookVec();
		return world.rayTraceBlocks(posVec, posVec.add(lookVec.scale(32)), stopOnLiquid);
	}