Added GUI Detection system with DeluxeMenus support

eco-api/src/main/java/com/willfp/eco/core/display/Display.java

@@ -1,6 +1,7 @@
 package com.willfp.eco.core.display;
 
 import com.willfp.eco.core.fast.FastItemStack;
+import com.willfp.eco.core.integrations.guidetection.GUIDetectionManager;
 import com.willfp.eco.util.NamespacedKeyUtils;
 import org.bukkit.NamespacedKey;
 import org.bukkit.entity.Player;
@@ -71,7 +72,7 @@ public final class Display {
         ItemStack original = itemStack.clone();
         Inventory inventory = player == null ? null : player.getOpenInventory().getTopInventory();
         boolean inInventory = inventory != null && inventory.contains(original);
-        boolean inGui = inventory != null && inventory.getHolder() == null;
+        boolean inGui = player != null && GUIDetectionManager.hasGUIOpen(player);
 
         DisplayProperties properties = new DisplayProperties(
                 inInventory,

eco-api/src/main/java/com/willfp/eco/core/integrations/guidetection/GUIDetectionIntegration.java

@@ -0,0 +1,18 @@
+package com.willfp.eco.core.integrations.guidetection;
+
+import com.willfp.eco.core.integrations.Integration;
+import org.bukkit.entity.Player;
+import org.jetbrains.annotations.NotNull;
+
+/**
+ * Wrapper class for GUI integrations.
+ */
+public interface GUIDetectionIntegration extends Integration {
+    /**
+     * Determine if a player is in a GUI.
+     *
+     * @param player The player.
+     * @return If the player is in a GUI.
+     */
+    boolean hasGUIOpen(@NotNull final Player player);
+}

eco-api/src/main/java/com/willfp/eco/core/integrations/guidetection/GUIDetectionManager.java

@@ -0,0 +1,52 @@
+package com.willfp.eco.core.integrations.guidetection;
+
+import com.willfp.eco.util.MenuUtils;
+import org.bukkit.entity.Player;
+import org.jetbrains.annotations.NotNull;
+
+import java.util.HashSet;
+import java.util.Set;
+
+/**
+ * Class to handle GUI detection.
+ */
+public final class GUIDetectionManager {
+    /**
+     * A set of all registered integrations.
+     */
+    private static final Set<GUIDetectionIntegration> REGISTERED = new HashSet<>();
+
+    /**
+     * Register a new integration.
+     *
+     * @param integration The integration to register.
+     */
+    public static void register(@NotNull final GUIDetectionIntegration integration) {
+        REGISTERED.removeIf(it -> it.getPluginName().equalsIgnoreCase(integration.getPluginName()));
+        REGISTERED.add(integration);
+    }
+
+    /**
+     * Get if a player is in a GUI.
+     *
+     * @param player The player.
+     * @return If the player has a GUI open.
+     */
+    public static boolean hasGUIOpen(@NotNull final Player player) {
+        if (MenuUtils.getOpenMenu(player) != null) {
+            return true;
+        }
+
+        for (GUIDetectionIntegration integration : REGISTERED) {
+            if (integration.hasGUIOpen(player)) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
+    private GUIDetectionManager() {
+        throw new UnsupportedOperationException("This is a utility class and cannot be instantiated");
+    }
+}

eco-core/core-plugin/src/main/kotlin/com/willfp/eco/internal/spigot/integrations/guidetection/GUIDetectionDeluxeMenus.kt

@@ -0,0 +1,15 @@
+package com.willfp.eco.internal.spigot.integrations.guidetection
+
+import com.extendedclip.deluxemenus.menu.Menu
+import com.willfp.eco.core.integrations.guidetection.GUIDetectionIntegration
+import org.bukkit.entity.Player
+
+class GUIDetectionDeluxeMenus: GUIDetectionIntegration {
+    override fun hasGUIOpen(player: Player): Boolean {
+        return Menu.inMenu(player)
+    }
+
+    override fun getPluginName(): String {
+        return "DeluxeMenus"
+    }
+}

eco-core/core-plugin/src/main/resources/plugin.yml

@@ -51,3 +51,4 @@ softdepend:
   - Scyther
   - ModelEngine
   - PvPManager
+  - DeluxeMenus