Methods to find all Windows & Viewers in GUI

src/main/java/de/studiocode/invgui/gui/GUI.java

@@ -14,6 +14,7 @@ import org.bukkit.inventory.ItemStack;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
+import java.util.List;
 import java.util.Set;
 import java.util.function.Predicate;
 
@@ -230,6 +231,20 @@ public interface GUI {
      */
     Set<GUIParent> getParents();
     
+    /**
+     * Finds all {@link Window}s that show this {@link GUI}.
+     * 
+     * @return The list of {@link Window} that show this {@link GUI}
+     */
+    List<Window> findAllWindows();
+    
+    /**
+     * Finds all {@link Player}s that are currently seeing this {@link Window}.
+     * 
+     * @return The list of {@link Player}s that are currently seeing this {@link Window}
+     */
+    List<Player> findAllViewers();
+    
     /**
      * Plays an {@link Animation}.
      *

src/main/java/de/studiocode/invgui/gui/impl/IndexedGUI.java

@@ -201,7 +201,8 @@ abstract class IndexedGUI implements GUI, GUIParent {
         return parents;
     }
     
-    private List<Window> findAllWindows() {
+    @Override
+    public List<Window> findAllWindows() {
         List<Window> windows = new ArrayList<>();
         List<GUIParent> parents = new ArrayList<>(this.parents);
         
@@ -217,6 +218,16 @@ abstract class IndexedGUI implements GUI, GUIParent {
         return windows;
     }
     
+    @Override
+    public List<Player> findAllViewers() {
+        List<Player> players = new ArrayList<>();
+        findAllWindows().stream()
+            .flatMap(window -> window.getInventory().getViewers().stream())
+            .forEach(humanEntity -> players.add((Player) humanEntity));
+        
+        return players;
+    }
+    
     @Override
     public void playAnimation(@NotNull Animation animation, @Nullable Predicate<ItemStackHolder> filter) {
         if (animation != null) cancelAnimation();