[1.12.2] Locking an item in place inside your inventory

[LoganDark]

Hi, it's me again, back with the Potato Furnace.

 

So, I have the furnace functionality working (just whatever you do, do NOT move/drop/touch the item in creative mode while it has items in it).

 

If you download the mod (diamond2potato-1.0.jar or build it yourself), load it up in a singleplayer (or multiplayer, it works in both) world, run the /pfurnace command (for testing), and open the GUI, you'll find that the item you opened the GUI from is somewhat hard to move. You can't even drop it via Q, you can't pick it up with left or right click. However, there's some issues...

 

Say you have it in hotbar slot 1.

 

• Hovering over that slot and pressing any other hotbar key will duplicate the stack to that slot. I know it's a duplicate because it multiplies the times the furnace capability's update function is called per tick, and dropping one of them makes them all disappear. Rejoining (singleplayer or multiplayer, still doesn't matter) causes all of these items to duplicate, including the items inside them. Here's a gif of that furnace updating thing:
  
  
  
  However, taking, for example, the result items out, result in ghost items in multiplayer that don't actually exist on the server, causing weird behavior.
• Hovering over any slot (doesn't have to be your hotbar) and pressing the key of the furnace slot (let's say slot 1 still) will cause it to disappear. Yep, gone forever. Of course, you can still take the items out of it, but only until you close the GUI.
• Picking up an item (like with your mouse) and then trying to swap it with the furnace causes your picked up item to become another duplicate of the furnace. When you place it in a slot, the furnace moves. The GUI stops updating. When you close it, the original disappears. But, you can use any item to keep duplicating furnaces from the original item, then when you close the GUI only the original will disappear. You can drop both duplicated items separately to prove they really duplicated.
• Shift-clicking it once will move it in your inventory, shift-clicking again will cause it to disappear. (assuming you used /pfurnace to spawn it, which puts it in the right configuration to do something like that)

 

Oh, by the way, all of this item duplication stuff works and was tested in SMP. Sanity checks like dropping the items on the ground or rejoining the server were performed to make sure the item really was/wasn't duplicated.

 

Now, I'd really like to implement server-side guards for this. I've tried to implement an IInventory for the GUI used on the server (and client too naturally), that tries to prevent any of this stuff. I know you can disable slots on the client side, since I had to reimplement ContainerFurnace to allow for any IInventory to be used, but I really want to get the server-side down FIRST before I prevent anything on the client.

 

GitHub

Edited July 8, 2019 by LoganDark