Hooks for ItemStack NBT update animation

Issue

When an ItemStack’s NBT updates, a quick “reload” animation is played (which involves the item dipping down and then pulling back up). This quickly becomes an issue when you have items that reload NBT quickly, like a tick counter item:

Registry.register(
        Registry.ITEM,
        new Identifier("nbtissue", "testitem"),
        new Item(new Item.Settings()) {
            @Override
            public void inventoryTick(ItemStack stack, World world, Entity entity, int slot, boolean selected) {
                float currentTicks = stack.getOrCreateTag().getFloat("ticks");
                stack.getOrCreateTag().putFloat("ticks", currentTicks + 1);
                super.inventoryTick(stack, world, entity, slot, selected);
            }
        }
);

(result)

Context

HeldItemRenderer#updateHeldItems is where this animation update takes place. Forge has a hook here that allows you to define whether an item should cause said re-equip animation, and I think providing something similar in the API would be a good idea.

Current Solutions

In Inmis, I use an entirely cursed solution for getting around this issue. This will, obviously, fail as soon as 2 people try to do it (I claimed it first!!!). I’m writing this issue up now because several other people are encountering this issue and need a solution.

Potential Solutions

Forge provides a method in their Item class that allows you to define whether the re-equip animation should occur between stack A and stack B. We could do something similar in usage, like:

FabricItemUpdateAnimations.register(Items.MY_ITEM, (originalStack, newStack) -> {
        return [...]
});

An event might also make sense (so multiple people can have a say in whether a diamond sword triggers the reload animation):

ItemUpdateAnimationCallback.event(Items.DIAMOND_SWORD).register((originalStack, newStack) -> {
        return ActionResult.FAIL;
});

[Technici4n]

Implemented in #1790.

[TheBrokenRail]

If you only cancel in your special case, it will fall through to other injections and eventually the default implementation:

@Mixin(ItemStack.class)
public class ItemStackMixin {

    @Inject(at = @At("HEAD"), method = "equals", cancelable = true)
    public void equals(Object obj, CallbackInfoRetrunable<Boolean> info) {
        if (obj instanceof ItemStack) {
            ItemStack thisStack = (ItemStack) (Object) this;
            ItemStack checkStack = (ItemStack) obj;

            Item thisStackItem = thisStack.getItem();
            Item checkStackItem = checkStack.getItem();

            if (thisStackItem instanceof BackpackItem && checkStackItem instanceof BackpackItem) {
                info.setRetunrValue(true);
            }
        }
    }
}