Modular Items

IModularItem

IModularItem is a capability that can be attached to item stacks. Its recommended implementation is ModularItemStack, which can be attached to a stack in an AttachCapabilitiesEvent<ItemStack> listener, or attached as an item component to a ComponentItem using ModularItemComponent. Note that if it is attached not as a component, module-related tooltips won't be displayed, and onUse and related methods won't work.

Attaching a ModularItemStack using an event

@Mod.EventBusSubscriber(modid = "your_mod_id", bus = Mod.EventBusSubscriber.Bus.FORGE)
public static class ExampleEventListener {
    @SubscribeEvent
    public static void onAttachCapabilities(AttachCapabilitiesEvent<ItemStack> event) {
        ItemStack stack = event.getObject();
        if (stack.is(Items.DIAMOND_CHESTPLATE)) {
            int slots = 5, maxTier = GTValues.HV;
            List<ItemModuleSlot> defaultSlots = new ArrayList<>();
            for (int i = 0; i < slots; i++) defaultSlots.add(GTItemModules.TIERED_SLOTS[maxTier]);
            // ModularItemStack accepts a Function<ItemStack, List<ItemModuleSlot>> in the constructor
            // The stack provided to that function is the same stack as here, so we can ignore it
            event.addCapability(GTCEu.id("modular"), new ModularItemStack(stack, ignored -> defaultSlots));
        }
    }
}

Attaching a ModularItemComponent to a ComponentItem

public void attachModularComponent() {
    // fertilizer will now have 3 MV module slots
    GTItems.FERTILIZER.get().attachComponents(new ModularItemComponent(3, GTValues.MV));
}

ItemModuleSlot

An ItemModuleSlot is basically a Predicate<ItemModule> (a function that accepts an ItemModule and returns a boolean) with some other methods. It has 3 abstract methods for your subclasses to implement:

• acceptsModule(ItemModule) -> boolean returns whether the provided module can be put into this slot
• getDisplayName() -> Component returns the text to be displayed as part of the tooltip
• getSlotTexture() -> IDrawable (returns null by default) returns the texture to use for this slot in the equipment foundry UI, null means to use the default

Tiered slot implementation

public class TieredItemModuleSlot extends ItemModuleSlot {

    @Getter
    private final int tier;

    public TieredItemModuleSlot(ResourceLocation id, int tier) {
        super(id);
        this.tier = tier;
    }

    @Override
    public boolean acceptsModule(ItemModule module) {
        return !(module instanceof ITieredItemModule tieredModule) || tieredModule.getTier() <= getTier();
    }

    @Override
    public Component getDisplayName() {
        return Component.translatable("gui.gtceu.module_slot.tiered", GTValues.VNF[getTier()]);
    }
}

ItemModule

ItemModule is an NBT-serializable object that can be attached to modular items.
AppliedItemModule is an object that contains info about the module itself, the item it is applied to, and the module's NBT.

List of all overridable methods in ItemModule

• getInfo() -> Component (override required)
  returns the info about this module to display in XEI
• onAttach(AppliedItemModule) -> void
  called when this module is attached to a modular item
• onRemove(AppliedItemModule) -> void
  called when this module is removed from a modular item
• onEquip(LivingEntity, AppliedItemModule) -> void
  called when the armor piece this module is attached to is equipped
• onUnequip(LivingEntity, AppliedItemModule) -> void
  called when the armor piece this module is attached to is unequipped
• onArmorTick(LivingEntity, AppliedItemModule) -> void
  called each tick while the armor piece this module is attached to is equipped
• onInventoryTick(Player, AppliedItemModule) -> void
  called each tick while the item this module is attached to is in a player's inventory
• appendHoverText(Level, TooltipFlag, List<Component>, AppliedItemModule) -> void
  called to insert lines into the modular item's tooltip
• useEnergyInInventory(LivingEntity, AppliedItemModule) -> boolean (default true)
  returns whether to consume energy while the item is in a player's inventory, if false, the item consumes energy only in armor slots
• energyUsagePerTick(LivingEntity, AppliedItemModule) -> long (default 0)
  returns the amount of energy to consume this tick (called every tick)
• changeDamage(LivingEntity, AppliedItemModule, float damage, DamageSource)-> float (returns damage by default)
  returns the amount of damage to actually inflict, called each time the entity wearing the armor piece is damaged
• canRemove(AppliedItemModule) -> boolean (default true)
  returns whether this module can be removed from the item in an equipment foundry
• isPPE(AppliedItemModule) -> boolean (default false)
  returns whether armor pieces with this module should be considered personal protection equipment (hazmat)
• canApplyTo(ItemStack) -> boolean
  returns whether this module can be attached to the provided stack, by default returns whether a module of this type is already attached to the stack (blocking more than one module of the same type)
• isEnabled(AppliedItemModule) -> boolean (default true)
  returns whether this module is enabled (all other methods, such as onInventoryTick won't be calld if it's disabled)
• setEnabled(AppliedItemModule, boolean) -> void
  by default, sets the return value of isEnabled by modifying this module's NBT; this method is not required to actually enable/disable this module
• use(AppliedItemModule, Level, Player, InteractionHand) -> InteractionResultHolder<ItemStack>
  called when the item this module is attached to is used
• useOn(AppliedItemModule, UseOnContext) -> InteractionResult
  called when the item this module is attached to is used on a block

Example of an energy shield module

public class EnergyShieldItemModule extends TieredItemModule {

    public EnergyShieldItemModule(ResourceLocation id, int tier) {
        super(id, tier);
    }

    @Override
    public Component getInfo() {
        return Component.literal("Makes you invulnerable and consumes 1A " + GTValues.VNF[getTier()]);
    }

    @Override
    public long energyUsagePerTick(LivingEntity entity, AppliedItemModule module) {
        return GTValues.V[getTier()];
    }

    @Override
    public float changeDamage(LivingEntity entity, AppliedItemModule module, float amount, DamageSource source) {
        return 0;
    }

    @Override
    public void appendHoverText(Level level, TooltipFlag isAdvanced, List<Component> tooltips,
                                AppliedItemModule module) {
        super.appendHoverText(level, isAdvanced, tooltips, module);
        tooltips.add(Component.literal("Energy shield (" + GTValues.VNF[getTier()] + ")"));
    }
}