MT Inventory Weight Add-on API

MT Inventory Weight exposes a public API for other mods and add-ons.

Use this package:

com.megatrex4.api.v1

Do not depend on classes under:

com.megatrex4.impl

Those classes are internal implementation details.

Entrypoint

Add this to your fabric.mod.json:

{
  "entrypoints": {
    "inventoryweight": [
      "com.example.ExampleInventoryWeightAddon"
    ]
  },
  "depends": {
    "inventoryweight": ">=2.0.0"
  }
}

Then implement:

package com.example;

import com.megatrex4.api.v1.InventoryWeightEntrypoint;
import com.megatrex4.api.v1.InventoryWeightRegistrar;

public final class ExampleInventoryWeightAddon implements InventoryWeightEntrypoint {
    @Override
    public void registerInventoryWeight(InventoryWeightRegistrar registrar) {
        // Register providers here.
    }
}

Max Weight Attribute

MT Inventory Weight also exposes a normal Minecraft attribute for player max weight:

inventoryweight:generic.max_weight

API constant:

InventoryWeightAttributes.GENERIC_MAX_WEIGHT

This lets level systems, RPG mods, equipment mods, or add-ons add normal attribute modifiers to a player's carrying capacity.

Example:

EntityAttributeInstance instance = player.getAttributes().getCustomInstance(
        InventoryWeightAttributes.GENERIC_MAX_WEIGHT
);

if (instance != null) {
    instance.addPersistentModifier(new EntityAttributeModifier(
            UUID.fromString("11111111-2222-3333-4444-555555555555"),
            "example_max_weight_bonus",
            10000.0,
            EntityAttributeModifier.Operation.ADDITION
    ));
}

The final max weight calculation is:

server config maxWeight
+ inventoryweight:generic.max_weight attribute value
+ CCA capacity bonus
+ armor pocket capacity
+ add-on capacity providers
= final max weight

This attribute is an additional max-weight contribution, not the whole final max weight. The mod does not overwrite this attribute during normal config updates. Other mods such as PlayerEx can safely control it with standard attribute modifiers.

Provider Types

The registrar supports:

registerItemWeightProvider(...)
registerPlayerWeightSource(...)
registerCapacityProvider(...)
registerPocketProvider(...)

Item Weight Provider

Use an item weight provider when your mod has items that need custom weight logic.

registrar.registerItemWeightProvider(
        new Identifier("example", "mana_tablet_weight"),
        9000,
        (stack, context, lookup) -> {
            Identifier id = Registries.ITEM.getId(stack.getItem());

            if (!id.equals(new Identifier("example", "mana_tablet"))) {
                return Optional.empty();
            }

            float baseWeight = 250.0f;
            float manaWeight = 0.0f;

            if (stack.hasNbt() && stack.getNbt() != null) {
                manaWeight = stack.getNbt().getInt("Mana") / 100.0f;
            }

            return Optional.of(WeightResult.of(baseWeight + manaWeight, baseWeight));
        }
);

Player Weight Source

Use a player weight source when your mod adds extra equipment or inventory slots.

registrar.registerPlayerWeightSource(
        new Identifier("example", "belt_slots"),
        1000,
        (player, context, lookup) -> {
            WeightResult total = WeightResult.ZERO;

            for (ItemStack stack : getExampleBeltStacks(player)) {
                total = total.add(lookup.getWeight(stack, context).multiply(stack.getCount()));
            }

            return total;
        }
);

Capacity Provider

Use a capacity provider when your mod should increase or multiply max carry weight.

registrar.registerCapacityProvider(
        new Identifier("example", "class_bonus"),
        1000,
        player -> {
            if (isWarrior(player)) {
                return CapacityModifier.additive(10_000.0f);
            }

            return CapacityModifier.none();
        }
);

Pocket Provider

Use a pocket provider when your mod adds armor or equipment that should provide pocket capacity.

registrar.registerPocketProvider(
        new Identifier("example", "custom_armor_pockets"),
        9000,
        (stack, wearer) -> {
            Identifier id = Registries.ITEM.getId(stack.getItem());

            if (id.equals(new Identifier("example", "utility_chestplate"))) {
                return OptionalInt.of(8);
            }

            return OptionalInt.empty();
        }
);

Priority

Higher priority providers run first.

Suggested priority ranges:

10000+ hard overrides
9000   datapack/NBT-like overrides
8000   containers/backpacks
1000   normal compatibility
0      fallback

Events

InventoryWeightEvents allows advanced modification:

InventoryWeightEvents.MODIFY_ITEM_WEIGHT.register((stack, context, current) -> current);
InventoryWeightEvents.MODIFY_PLAYER_INVENTORY_WEIGHT.register((player, current) -> current);
InventoryWeightEvents.MODIFY_MAX_WEIGHT.register((player, currentMax) -> currentMax);
InventoryWeightEvents.OVERLOAD_CHANGED.register((player, overloaded) -> {});