[1.19.x] Add event for items being stacked or swapped in a GUI. (#9050)

patches/minecraft/net/minecraft/commands/CommandSourceStack.java.patch

@@ -8,4 +8,4 @@
 +public class CommandSourceStack implements SharedSuggestionProvider, net.minecraftforge.common.extensions.IForgeCommandSourceStack {
     public static final SimpleCommandExceptionType f_81286_ = new SimpleCommandExceptionType(Component.m_237115_("permissions.requires.player"));
     public static final SimpleCommandExceptionType f_81287_ = new SimpleCommandExceptionType(Component.m_237115_("permissions.requires.entity"));
-    private final CommandSource f_81288_;
+    public final CommandSource f_81288_;

patches/minecraft/net/minecraft/world/inventory/AbstractContainerMenu.java.patch

@@ -12,6 +12,14 @@
           for(ContainerListener containerlistener : this.f_38848_) {
              containerlistener.m_7934_(this, p_150408_, itemstack1);
           }
+@@ -400,6 +_,7 @@
+             ItemStack itemstack11 = this.m_142621_();
+             p_150434_.m_141945_(itemstack11, slot7.m_7993_(), clickaction);
+             if (!itemstack11.m_150926_(slot7, clickaction, p_150434_) && !itemstack10.m_150932_(itemstack11, slot7, clickaction, p_150434_, this.m_150446_())) {
++            if (!net.minecraftforge.common.ForgeHooks.onItemStackedOn(itemstack11, itemstack10, slot7, clickaction, p_150434_, m_150446_()))
+                if (itemstack10.m_41619_()) {
+                   if (!itemstack11.m_41619_()) {
+                      int l2 = clickaction == ClickAction.PRIMARY ? itemstack11.m_41613_() : 1;
 @@ -601,14 +_,15 @@
              ItemStack itemstack = slot.m_7993_();
              if (!itemstack.m_41619_() && ItemStack.m_150942_(p_38904_, itemstack)) {

src/main/java/net/minecraftforge/common/ForgeHooks.java

@@ -60,7 +60,10 @@ import net.minecraft.world.entity.ai.attributes.AttributeModifier;
 import net.minecraft.world.entity.ai.attributes.AttributeSupplier;
 import net.minecraft.world.entity.ai.attributes.DefaultAttributes;
 import net.minecraft.world.entity.monster.EnderMan;
+import net.minecraft.world.entity.SlotAccess;
+import net.minecraft.world.inventory.ClickAction;
 import net.minecraft.world.inventory.ContainerLevelAccess;
+import net.minecraft.world.inventory.Slot;
 import net.minecraft.world.item.*;
 import net.minecraft.world.item.crafting.Ingredient;
 import net.minecraft.world.item.crafting.RecipeType;
@@ -115,6 +118,7 @@ import net.minecraftforge.event.DifficultyChangeEvent;
 import net.minecraftforge.event.ForgeEventFactory;
 import net.minecraftforge.event.GrindstoneEvent;
 import net.minecraftforge.event.ItemAttributeModifierEvent;
+import net.minecraftforge.event.ItemStackedOnOtherEvent;
 import net.minecraftforge.event.ModMismatchEvent;
 import net.minecraftforge.event.ServerChatEvent;
 import net.minecraftforge.event.RegisterStructureConversionsEvent;
@@ -266,6 +270,11 @@ public class ForgeHooks
         return false;
     }
 
+    public static boolean onItemStackedOn(ItemStack carriedItem, ItemStack stackedOnItem, Slot slot, ClickAction action, Player player, SlotAccess carriedSlotAccess)
+    {
+        return MinecraftForge.EVENT_BUS.post(new ItemStackedOnOtherEvent(carriedItem, stackedOnItem, slot, action, player, carriedSlotAccess));
+    }
+
     public static void onDifficultyChange(Difficulty difficulty, Difficulty oldDifficulty)
     {
         MinecraftForge.EVENT_BUS.post(new DifficultyChangeEvent(difficulty, oldDifficulty));

src/main/java/net/minecraftforge/event/ItemStackedOnOtherEvent.java

@@ -0,0 +1,104 @@
+/*
+ * Copyright (c) Forge Development LLC and contributors
+ * SPDX-License-Identifier: LGPL-2.1-only
+ */
+
+package net.minecraftforge.event;
+
+import net.minecraft.world.entity.SlotAccess;
+import net.minecraft.world.entity.player.Player;
+import net.minecraft.world.inventory.ClickAction;
+import net.minecraft.world.inventory.Slot;
+import net.minecraft.world.item.Item;
+import net.minecraft.world.item.ItemStack;
+
+import net.minecraftforge.eventbus.api.Cancelable;
+import net.minecraftforge.eventbus.api.Event;
+import net.minecraftforge.fml.LogicalSide;
+
+import org.jetbrains.annotations.ApiStatus;
+
+/**
+ * This event provides the functionality of the pair of functions used for the Bundle, in one event:
+ * <ul>
+ *     <li>{@link Item#overrideOtherStackedOnMe(ItemStack, ItemStack, Slot, ClickAction, Player, SlotAccess)}</li>
+ *     <li>{@link Item#overrideStackedOnOther(ItemStack, Slot, ClickAction, Player)}</li>
+ * </ul>
+ *
+ *  This event is fired before either of the above are called, when a carried item is clicked on top of another in a GUI slot.
+ *  This event (and items stacking on others in general) is fired on both {@linkplain LogicalSide sides}, but only on {@linkplain LogicalSide#CLIENT the client} in the creative menu.
+ *  Practically, that means that listeners of this event should require the player to be in survival mode if using capabilities that are not synced.
+ *  <p>
+ *  This event is {@linkplain Cancelable cancellable}, and does not {@linkplain HasResult have a result}.
+ *  If the event is cancelled, the container's logic halts, the carried item and the slot will not be swapped, and handling is assumed to have been done by the mod.
+ *  This also means that the two vanilla checks described above will not be called.
+ */
+@Cancelable
+public class ItemStackedOnOtherEvent extends Event
+{
+    private final ItemStack carriedItem;
+    private final ItemStack stackedOnItem;
+    private final Slot slot;
+    private final ClickAction action;
+    private final Player player;
+    private final SlotAccess carriedSlotAccess;
+
+    @ApiStatus.Internal
+    public ItemStackedOnOtherEvent(ItemStack carriedItem, ItemStack stackedOnItem, Slot slot, ClickAction action, Player player, SlotAccess carriedSlotAccess)
+    {
+        this.carriedItem = carriedItem;
+        this.stackedOnItem = stackedOnItem;
+        this.slot = slot;
+        this.action = action;
+        this.player = player;
+        this.carriedSlotAccess = carriedSlotAccess;
+    }
+
+    /**
+     * {@return the stack being carried by the mouse} This may be empty!
+     */
+    public ItemStack getCarriedItem()
+    {
+        return carriedItem;
+    }
+
+    /**
+     * {@return the stack currently in the slot being clicked on} This may be empty!
+     */
+    public ItemStack getStackedOnItem()
+    {
+        return stackedOnItem;
+    }
+
+    /**
+     * {@return the slot being clicked on}
+     */
+    public Slot getSlot()
+    {
+        return slot;
+    }
+
+    /**
+     * {@return the click action being used} By default {@linkplain ClickAction#PRIMARY} corresponds to left-click, and {@linkplain ClickAction#SECONDARY} is right-click.
+     */
+    public ClickAction getClickAction()
+    {
+        return action;
+    }
+
+    /**
+     * {@return the player doing the item swap attempt}
+     */
+    public Player getPlayer()
+    {
+        return player;
+    }
+
+    /**
+     * {@return a fake slot allowing the listener to see and change what item is being carried}
+     */
+    public SlotAccess getCarriedSlotAccess()
+    {
+        return carriedSlotAccess;
+    }
+}

src/test/java/net/minecraftforge/debug/item/ItemStackedOnOtherTest.java

@@ -0,0 +1,48 @@
+/*
+ * Copyright (c) Forge Development LLC and contributors
+ * SPDX-License-Identifier: LGPL-2.1-only
+ */
+
+package net.minecraftforge.debug.item;
+
+import net.minecraft.world.entity.player.Player;
+import net.minecraft.world.inventory.ClickAction;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.item.Items;
+import net.minecraftforge.common.MinecraftForge;
+import net.minecraftforge.event.ItemStackedOnOtherEvent;
+import net.minecraftforge.fml.common.Mod;
+
+@Mod(ItemStackedOnOtherTest.MODID)
+public class ItemStackedOnOtherTest
+{
+    public static final String MODID = "item_stacked_on_other_test";
+
+    private static final boolean ENABLED = true;
+
+    public ItemStackedOnOtherTest()
+    {
+        if (ENABLED)
+        {
+            MinecraftForge.EVENT_BUS.addListener(this::onStackedOn);
+        }
+    }
+
+    /**
+     * When right clicking on a damageable item with a diamond sword
+     */
+    private void onStackedOn(ItemStackedOnOtherEvent event)
+    {
+        Player player = event.getPlayer();
+        if (!player.isCreative() && event.getClickAction() == ClickAction.SECONDARY)
+        {
+            ItemStack carried = event.getCarriedItem();
+            ItemStack current = event.getStackedOnItem();
+            if (carried.is(Items.DIAMOND_SWORD) && current.isDamageableItem())
+            {
+                current.hurtAndBreak(1, player, p -> {});
+                event.setCanceled(true);
+            }
+        }
+    }
+}

src/test/resources/META-INF/mods.toml

@@ -263,6 +263,8 @@ modId="custom_color_resolver_test"
 [[mods]]
 modId="custom_item_decorations_test"
 [[mods]]
+modId="item_stacked_on_other_test"
+[[mods]]
 modId="ambient_occlusion_elements_test"