Migrating Inventories & GUIs from Bukkit

Creating inventory GUIs (like chest menus, shop interfaces, or custom player windows) is a common task in Minecraft plugin development.

In Bukkit, custom GUIs are created using Bukkit.createInventory() and handled via InventoryClickEvent. In Pumpkin, inventory windows are managed through Window APIs and container click packets.

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Key Differences

Feature	Bukkit / Spigot	Pumpkin
Inventory Creation	Bukkit.createInventory(owner, size, title)	Window container definitions (WindowType)
Opening Windows	player.openInventory(inv)	player.open_window(window)
Click Interception	InventoryClickEvent handling	Window click callback handlers
Item Stacking	ItemStack with ItemMeta	ItemStack with components / NBT

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Code Comparison: Opening a Custom Menu GUI

1. Bukkit Implementation (Java)

public class MenuGUI implements Listener {

    public void openMenu(Player player) {
        Inventory inv = Bukkit.createInventory(null, 9, Component.text("Custom Menu"));

        ItemStack item = new ItemStack(Material.DIAMOND);
        ItemMeta meta = item.getItemMeta();
        meta.displayName(Component.text("Click Me!"));
        item.setItemMeta(meta);

        inv.setItem(4, item);
        player.openInventory(inv);
    }

    @EventHandler
    public void onInventoryClick(InventoryClickEvent event) {
        if (event.getView().getTitle().equals("Custom Menu")) {
            event.setCancelled(true);
            if (event.getSlot() == 4) {
                event.getWhoClicked().sendMessage("Diamond clicked!");
            }
        }
    }
}

2. Pumpkin Implementation (Rust)

use pumpkin_plugin_api::{
    player::Player,
    item::ItemStack,
    window::{Window, WindowType},
    text::TextComponent,
};

pub fn open_custom_menu(player: &Player) {
    // 1. Create a 9-slot chest window
    let mut window = Window::new(WindowType::Generic9x1, TextComponent::text("Custom Menu"));

    // 2. Set item in slot 4
    let item = ItemStack::new("minecraft:diamond", 1);
    window.set_item(4, Some(item));

    // 3. Open window for player
    player.open_window(window);
}