Fire PlayerDropItemEvent for dropping from inventories

- Fire and handle PlayerDropItemEvent when:
  - Using Q / CTRL-Q to drop an item from an inventory in a Gui
  - Using left / right-click to drop a cursor item
  - Closing a Window with an item on the cursor (Only if there's no space in the player inventory. If the event is fired an cancelled, the item is deleted. This matches existing behavior for e.g. Chests.)

Improved handling of ItemPreUpdateEvent for Q / CTRL-Q: Updated new item stack amount will be reflected in the amount of dropped items

Author: NichtStudioCode

invui/src/main/java/xyz/xenondevs/invui/gui/AbstractGui.java

@@ -286,7 +286,9 @@ private void handleInvNumberKey(Click click, Inventory inventory, int slot) {
         if (link == null)
             return;
 
-        if (link.getHoldingElement() instanceof SlotElement.InventoryLink(var otherInventory, var otherSlot, var unused)) {
+        if (link.getHoldingElement() instanceof SlotElement.InventoryLink(
+            var otherInventory, var otherSlot, var unused
+        )) {
             if (inventory == otherInventory && slot == otherSlot)
                 return;
 
@@ -319,22 +321,27 @@ private void handleInvOffHandKey(Click click, Inventory inventory, int slot) {
     }
 
     private void handleInvDrop(boolean ctrl, Click click, Inventory inventory, int slot) {
-        Player player = click.player();
         ItemStack clicked = inventory.getItem(slot);
-        
-        if (clicked == null)
+        if (ItemUtils.isEmpty(clicked))
             return;
 
+        Player player = click.player();
         UpdateReason updateReason = new PlayerUpdateReason.Click(player, click);
 
-        if (ctrl) {
-            if (inventory.setItem(updateReason, slot, null)) {
-                InventoryUtils.dropItemLikePlayer(player, clicked);
-            }
-        } else if (inventory.addItemAmount(updateReason, slot, -1) == -1) {
-            clicked.setAmount(1);
-            InventoryUtils.dropItemLikePlayer(player, clicked);
-        }
+        int initialDropCount = ctrl ? clicked.getAmount() : 1;
+        var initialNewItem = ItemUtils.cloneWithCount(clicked, clicked.getAmount() - initialDropCount);
+        var event = inventory.callPreUpdateEvent(updateReason, slot, clicked, initialNewItem);
+        if (event.isCancelled())
+            return;
+        
+        var newItem = event.getNewItem();
+        int dropCount = clicked.getAmount() - (newItem != null ? newItem.getAmount() : 0);
+        var toDrop = ItemUtils.cloneWithCount(clicked, dropCount);
+        if (!InventoryUtils.dropItemLikePlayer(player, toDrop))
+            return;
+        
+        inventory.forceSetItem(UpdateReason.SUPPRESSED, slot, newItem);
+        inventory.callPostUpdateEvent(updateReason, slot, clicked, newItem);
     }
 
     private void handleInvDoubleClick(Click click) {
@@ -385,28 +392,7 @@ private void handleInvBundleSelect(Player player, Inventory inventory, int slot,
             inventory.setItem(new PlayerUpdateReason.BundleSelect(player, bundleSlot), slot, bundle);
         }
     }
-    
-    /**
-     * Puts the given {@link ItemStack} into the first inventory that accepts it, starting with the
-     * {@link Inventory#getGuiPriority(OperationCategory)} for {@link OperationCategory#ADD} highest priority inventory.
-     * If one inventory accepts any amount of items, further inventories will not be queried, meaning that an item stack will not be split
-     * across multiple inventories.
-     *
-     * @param updateReason the update reason to use
-     * @param itemStack    the item stack to put
-     * @param ignored      the inventories to ignore
-     * @return the amount of items that are left over
-     */
-    protected int putIntoFirstInventory(UpdateReason updateReason, ItemStack itemStack, Inventory... ignored) {
-        return putIntoFirstInventory(
-            updateReason,
-            itemStack, 
-            getInventories(ignored).stream()
-                .sorted(Comparator.<Inventory>comparingInt(inv -> inv.getGuiPriority(OperationCategory.ADD)).reversed())
-                .toList()
-        );
-    }
-    
+            
     /**
      * Puts the given {@link ItemStack} into the first inventory that accepts it of the given collection of inventories.
      * If one inventory accepts any amount of items, further inventories will not be queried, meaning that an item stack
@@ -1116,7 +1102,7 @@ public S addIngredient(char key, SlotElementSupplier elementSupplier) {
             if (structure == null)
                 throw new IllegalStateException("Structure is not set");
             structure.addIngredient(key, elementSupplier);
-            return (S) this;    
+            return (S) this;
         }
 
         @Override

invui/src/main/java/xyz/xenondevs/invui/internal/util/InventoryUtils.java

@@ -4,7 +4,9 @@
 import org.bukkit.Location;
 import org.bukkit.entity.Item;
 import org.bukkit.entity.Player;
+import org.bukkit.event.player.PlayerDropItemEvent;
 import org.bukkit.inventory.ItemStack;
+import org.jspecify.annotations.Nullable;
 import xyz.xenondevs.invui.gui.Gui;
 import xyz.xenondevs.invui.inventory.Inventory;
 import xyz.xenondevs.invui.inventory.OperationCategory;
@@ -134,24 +136,37 @@ public static MenuType<?> getMatchingGenericMenuType(int width, int height) {
     }
 
     /**
-     * Spawns an item entity as if the player dropped it.
+     * Spawns an item entity as if the player dropped it, also firing {@link PlayerDropItemEvent}.
      *
      * @param player    The player
      * @param itemStack The item stack
+     * @return Whether the item was dropped. False if the event was cancelled.
      */
-    public static void dropItemLikePlayer(Player player, ItemStack itemStack) {
+    @SuppressWarnings("UnstableApiUsage")
+    public static boolean dropItemLikePlayer(Player player, @Nullable ItemStack itemStack) {
         if (ItemUtils.isEmpty(itemStack))
-            return;
+            return true;
 
         Location location = player.getLocation();
         location.add(0, 1.5, 0); // not the eye location
-        Item item = location.getWorld().dropItem(location, itemStack);
+        
+        Item item = location.getWorld().createEntity(location, Item.class);
+        item.setItemStack(itemStack.clone());
         item.setPickupDelay(40);
         item.setVelocity(location.getDirection().multiply(0.35));
+        
+        if (new PlayerDropItemEvent(player, item).callEvent()) {
+            location.getWorld().addEntity(item);
+            return true;
+        }
+        
+        return false;
     }
 
     /**
      * Adds an item stack to the player's inventory or drops it if it doesn't fit.
+     * Also fires {@link PlayerDropItemEvent}, effectively deleting the item if the event is cancelled.
+     * 
      * @param player The player
      * @param itemStack The item stack
      */

invui/src/main/java/xyz/xenondevs/invui/util/ItemUtils.java

@@ -79,6 +79,22 @@ public static boolean isEmpty(@Nullable ItemStack itemStack) {
         return itemStack.clone();
     }
 
+    /**
+     * Clones the given {@link ItemStack} and sets its amount to the given count.
+     *
+     * @param itemStack the item stack to clone
+     * @param count     the amount for the cloned item stack
+     * @return the cloned item stack with the given amount, or null if the item stack is empty
+     */
+    public static @Nullable ItemStack cloneWithCount(@Nullable ItemStack itemStack, int count) {
+        if (isEmpty(itemStack))
+            return null;
+        
+        ItemStack clone = itemStack.clone();
+        clone.setAmount(count);
+        return clone;
+    }
+    
     /**
      * Returns a copy of the non-empty placeholder item, which is an invisible non-air item stack.
      *

invui/src/main/java/xyz/xenondevs/invui/window/AbstractWindow.java

@@ -223,15 +223,15 @@ public void handleClick(int slot, Click click) {
             if (!event.isCancelled() && !ItemUtils.isEmpty(cursor)) {
                 switch (click.clickType()) {
                     case LEFT -> {
-                        InventoryUtils.dropItemLikePlayer(viewer, cursor);
-                        viewer.setItemOnCursor(null);
+                        if (InventoryUtils.dropItemLikePlayer(viewer, cursor))
+                            viewer.setItemOnCursor(null);
                     }
 
                     case RIGHT -> {
                         var drop = cursor.clone();
                         drop.setAmount(1);
-                        InventoryUtils.dropItemLikePlayer(viewer, drop);
-                        cursor.setAmount(cursor.getAmount() - 1);
+                        if (InventoryUtils.dropItemLikePlayer(viewer, drop))
+                            cursor.setAmount(cursor.getAmount() - 1);
                     }
 
                     default -> {}