[1.14.2] Containers and GUI's

[desht]

As anyone who's started porting to 1.14.2 is probably aware by now, container and GUI creation has changed... quite a bit.  To summarise what I've gathered so far:

• Containers (more accurately: container types) are now registry objects and must be registered in a RegistryEvent.Register<ContainerType<?>> event handler.
• Container objects themselves must provide a constructor of the form MyContainer(int windowId, PlayerInventory inv, PacketBuffer extraData).  This will be used to instantiate the client-side container.
• Your container's constructor must call the super Container constructor with your registered container type and the windowId parameter (this int parameter is not used in any other way - just pass it along to the superclass constructor and forget about it)
• You can use the extraData parameter to pass... extra data! to your container.  This PacketBuffer parameter is built server-side when you call NetworkHooks.openGui(); see below.
• Typically, your container will have (at least) two constructors; the factory constructor described above which is used for client-side construction, and a constructor taking whatever parameters you need to pass to set up your server-side container object.
• Container-based GUI's are now associated with a container type with the ScreenManager.registerFactory() method, which takes a registered ContainerType and a ScreenManager.IFactory to construct your GUI object. Call that in your client-side init code.
  • ExtensionPoint.GUIFACTORY is gone, no longer needed, as is the old IGuiHandler system.  ScreenManager does all that work now.
  • While there must be a one-to-one mapping from ContainerType to each GUI, also remember that you can happily re-use the same container class for multiple container types if you need to; just pass the container type as a parameter to your constructor and up along to the Container constructor.
• All container-based GUI's must provide a constructor taking(T, PlayerInventory, ITextComponent), where the generic T is the type of your container object.
  • Container-based GUI objects are now generified (is that a word?) on the container's class, e.g. public class MyGui extends ContainerScreen<MyContainer>
• IInteractionObject is gone; instead your tile entity should implement INamedContainerProvider: the createMenu() method is where you create and return your server-side container object. (I believe getDisplayName() is only used to initialize the title field of your GUI object).
  • To open a container-based GUI on the tile entity (server-side), call NetworkHooks.OpenGui(player, myTileEntity, pos) or player.openContainer(myTileEntity)
    • That would typically be called from Block#onBlockActivated()
  • If you want to create a container-based GUI for an item, create a class implementing INamedContainerProvider (a static inner class of the item makes sense, or perhaps an anonymous implementation), implementing createMenu() and getDisplayName() to create and return the container object as above. 
    • That would typically be called as something like NetworkHooks.OpenGui(player, new MyItemContainerProvider(stack), pos)  or player.openContainer(new MyItemContainerProvider(stack)) from Item#onItemRightClick() or Item#onItemUse()
• player.openContainer() can be used if you have no need to pass any extra data to the client, e.g. your GUI is just displaying container slots, like a chest.  But if your client GUI needs access to the client-side tile entity, use NetworkHooks.openGui() and pass at least the tile entity's blockpos so the client container can get the GUI object. 
• Syncing any necessary TE data to the client-side TE needs to be done separately by whatever means you choose.
• Note that NetworkHooks.openGui() has a couple of variants to allow extra data to be passed to the client-side container object: a simple pos argument if you just need to pass the blockpos of your TE, or a more flexible Consumer<PacketBuffer> if you have more complex data to pass to the client.  The simple pos variant just calls the full-blooded Consumer<PacketBuffer> variant in any case.  It's this packet buffer that is received by the client-side container constructor.

 

Edited August 21, 2019 by desht

[desht]

Bit of follow up since I understand a bit more now....

• To get extra data passed across to the client (like a TE blockpos, for example), Forge 26.0.16 adds an extra PacketBuffer parameter to the NetworkHooks.openGui() calls, and a corresponding parameter to the container factory constructor.
• Looks like NetworkHooks.openGui() remains the way to go for modded - I guess player.openContainer() is really for vanilla only?
• Update: player.openContainer() should be fine to use if you're just creating a GUI purely to display some container slots (and don't need direct access to the clientside tile entity), like a chest GUI for example. 
• Typically, you'll have two or more constructors in your container objects - one "factory" constructor which is called by Minecraft client-side when a GUI is opened (and when the container type is registered during init), and one or more constructors of your choosing which create a container with any data you need to initialize them with.
• Those extra constructors would be called server-side from your INamedContainerProvider implementation, and client-side from your "factory" constructor, having extracted information from the extraData PacketBuffer.

 

Edited June 12, 2019 by desht

[wilechaote]

Thx for digging into this and forwarding to all!

[desht]

No worries.  One other thing, regarding my point about one-to-one container->GUI mappings...

 

If you have one container object but you want several different GUIs (my use case: Modular Routers modules nearly all use the same container object - a 9-slot inventory for filtering - but several modules have extra GUI controls for configuring module-specific properties), then:

• A separate container type will need to be registered for each GUI type, but you can use the same subclass of Container each time, just with a different ContainerType parameter.
• Then you can associate each container type with its corresponding GUI using ScreenManager.registerFactory() as normal

 

[KingIceCream]

If I want to open an inventory on a custom mob and access its inventory (like how a horse works) would I need to register the container? I noticed that in the horse’s container class it puts (ContainerType<?>)null where the container class asks for the ContainerType, and that the horse’s container isn’t registered in the ContainerType class.

Edited June 12, 2019 by KingIceCream

[desht]

Yeah, the horse inventory handling does appear to be a bit of a special case.  I'm not sure what the correct modded solution is at this point; that's something that will need some experimentation...

[KingIceCream]

I did some more digging and found that the CreativeContainer class and the PlayerContainer class also put (ContainerType<?>)null where the container class asks for the container type. 

[Draco18s]

17 hours ago, KingIceCream said:

I did some more digging and found that the CreativeContainer class and the PlayerContainer class also put (ContainerType<?>)null where the container class asks for the container type. 

The creative inventory is super magic special (the client gets to dictate inventory changes, overriding the server), so that doesn't really surprise me.