Improved window building

- Removed the "retain" parameter from Windows - all Windows can now be closed and reopened
- Added open handlers to Windows
- Added quick build methods Window.Builder.build(Player) and Window.Builder.show(Player)
- Added some NotNull annotations

invui-kotlin/src/main/kotlin/xyz/xenondevs/invui/adventure/AdventureWindowContexts.kt

@@ -14,4 +14,4 @@ import xyz.xenondevs.invui.window.Window
  * @return This Window Builder
  */
 @Contract("_ -> this")
-fun <B : Window.Builder<*, *, B>> B.setTitle(title: Component): B = setTitle(AdventureComponentWrapper(title))
+fun <B : Window.Builder<*, B>> B.setTitle(title: Component): B = setTitle(AdventureComponentWrapper(title))

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

@@ -24,34 +24,33 @@ public abstract class AbstractDoubleWindow extends AbstractWindow {
     private final Inventory playerInventory;
     private final ItemStack[] playerItems = new ItemStack[36];
     protected Inventory upperInventory;
-    private boolean isCurrentlyOpened;
     
-    public AbstractDoubleWindow(Player player, ComponentWrapper title, int size, Inventory upperInventory, boolean closeable, boolean retain) {
+    public AbstractDoubleWindow(Player player, ComponentWrapper title, int size, Inventory upperInventory, boolean closeable) {
-        super(player.getUniqueId(), title, size, closeable, retain);
+        super(player.getUniqueId(), title, size, closeable);
         this.upperInventory = upperInventory;
         this.playerInventory = player.getInventory();
     }
     
-    protected void initUpperItems() {
+    @Override
+    protected void initItems() {
+        // init upper inventory
         for (int i = 0; i < upperInventory.getSize(); i++) {
             SlotElement element = getSlotElement(i);
             redrawItem(i, element, true);
         }
-    }
+        
-    
+        // store and clear player inventory
-    private void initPlayerItems() {
-        for (int i = upperInventory.getSize(); i < upperInventory.getSize() + 36; i++) {
-            SlotElement element = getSlotElement(i);
-            redrawItem(i, element, true);
-        }
-    }
-    
-    private void clearPlayerInventory() {
         Inventory inventory = getViewer().getInventory();
         for (int i = 0; i < 36; i++) {
             playerItems[i] = inventory.getItem(i);
             inventory.setItem(i, null);
         }
+        
+        // init player inventory
+        for (int i = upperInventory.getSize(); i < upperInventory.getSize() + 36; i++) {
+            SlotElement element = getSlotElement(i);
+            redrawItem(i, element, true);
+        }
     }
     
     private void restorePlayerInventory() {
@@ -71,7 +70,7 @@ public abstract class AbstractDoubleWindow extends AbstractWindow {
     @Override
     protected void setInvItem(int slot, ItemStack itemStack) {
         if (slot >= upperInventory.getSize()) {
-            if (isCurrentlyOpened) {
+            if (isOpen()) {
                 int invSlot = SlotUtils.translateGuiToPlayerInv(slot - upperInventory.getSize());
                 setPlayerInvItem(invSlot, itemStack);
             }
@@ -88,7 +87,7 @@ public abstract class AbstractDoubleWindow extends AbstractWindow {
     
     @Override
     public void handleViewerDeath(PlayerDeathEvent event) {
-        if (isCurrentlyOpened) {
+        if (isOpen()) {
             List<ItemStack> drops = event.getDrops();
             if (!event.getKeepInventory()) {
                 drops.clear();
@@ -103,15 +102,10 @@ public abstract class AbstractDoubleWindow extends AbstractWindow {
     protected void handleOpened() {
         // Prevent players from receiving advancements from UI items
         InventoryAccess.getPlayerUtils().stopAdvancementListening(getViewer());
-        
-        isCurrentlyOpened = true;
-        clearPlayerInventory();
-        initPlayerItems();
     }
     
     @Override
     protected void handleClosed() {
-        isCurrentlyOpened = false;
         restorePlayerInventory();
         
         // Start the advancement listeners again
@@ -136,7 +130,7 @@ public abstract class AbstractDoubleWindow extends AbstractWindow {
     
     @Override
     public Inventory[] getInventories() {
-        return isCurrentlyOpened ? new Inventory[] {upperInventory, playerInventory} : new Inventory[] {upperInventory};
+        return isOpen() ? new Inventory[] {upperInventory, playerInventory} : new Inventory[] {upperInventory};
     }
     
     public Inventory getUpperInventory() {
@@ -147,8 +141,6 @@ public abstract class AbstractDoubleWindow extends AbstractWindow {
         return playerInventory;
     }
     
-    protected abstract SlotElement getSlotElement(int index);
-    
     protected abstract Pair<AbstractGui, Integer> getWhereClicked(InventoryClickEvent event);
     
 }

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

@@ -17,12 +17,11 @@ public abstract class AbstractMergedWindow extends AbstractDoubleWindow {
     
     private final AbstractGui gui;
     
-    public AbstractMergedWindow(Player player, ComponentWrapper title, AbstractGui gui, Inventory upperInventory, boolean closeable, boolean retain) {
+    public AbstractMergedWindow(Player player, ComponentWrapper title, AbstractGui gui, Inventory upperInventory, boolean closeable) {
-        super(player, title, gui.getSize(), upperInventory, closeable, retain);
+        super(player, title, gui.getSize(), upperInventory, closeable);
         this.gui = gui;
         
         gui.addParent(this);
-        initUpperItems();
     }
     
     @Override

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

@@ -25,16 +25,16 @@ public abstract class AbstractSingleWindow extends AbstractWindow {
     private final int size;
     protected Inventory inventory;
     
-    public AbstractSingleWindow(UUID viewerUUID, ComponentWrapper title, AbstractGui gui, Inventory inventory, boolean initItems, boolean closeable, boolean retain) {
+    public AbstractSingleWindow(UUID viewerUUID, ComponentWrapper title, AbstractGui gui, Inventory inventory, boolean closeable) {
-        super(viewerUUID, title, gui.getSize(), closeable, retain);
+        super(viewerUUID, title, gui.getSize(), closeable);
         this.gui = gui;
         this.size = gui.getSize();
         this.inventory = inventory;
         
         gui.addParent(this);
-        if (initItems) initItems();
     }
     
+    @Override
     protected void initItems() {
         for (int i = 0; i < size; i++) {
             SlotElement element = gui.getSlotElement(i);
@@ -109,27 +109,27 @@ public abstract class AbstractSingleWindow extends AbstractWindow {
     }
     
     @SuppressWarnings("unchecked")
-    public abstract static class AbstractBuilder<W extends Window, V, S extends Builder.Single<W, V, S>>
+    public abstract static class AbstractBuilder<W extends Window, S extends Builder.Single<W, S>>
-        extends AbstractWindow.AbstractBuilder<W, V, S>
+        extends AbstractWindow.AbstractBuilder<W, S>
-        implements Builder.Single<W, V, S>
+        implements Builder.Single<W, S>
     {
         
         protected Supplier<Gui> guiSupplier;
         
         @Override
-        public S setGui(@NotNull Supplier<Gui> guiSupplier) {
+        public @NotNull S setGui(@NotNull Supplier<Gui> guiSupplier) {
             this.guiSupplier = guiSupplier;
             return (S) this;
         }
         
         @Override
-        public S setGui(@NotNull Gui gui) {
+        public @NotNull S setGui(@NotNull Gui gui) {
             this.guiSupplier = () -> gui;
             return (S) this;
         }
         
         @Override
-        public S setGui(@NotNull Gui.Builder<?, ?> builder) {
+        public @NotNull S setGui(@NotNull Gui.Builder<?, ?> builder) {
             this.guiSupplier = builder::build;
             return (S) this;
         }

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

@@ -21,14 +21,13 @@ public abstract class AbstractSplitWindow extends AbstractDoubleWindow {
     private final AbstractGui upperGui;
     private final AbstractGui lowerGui;
     
-    public AbstractSplitWindow(Player player, ComponentWrapper title, AbstractGui upperGui, AbstractGui lowerGui, Inventory upperInventory, boolean initItems, boolean closeable, boolean retain) {
+    public AbstractSplitWindow(Player player, ComponentWrapper title, AbstractGui upperGui, AbstractGui lowerGui, Inventory upperInventory, boolean closeable) {
-        super(player, title, upperGui.getSize() + lowerGui.getSize(), upperInventory, closeable, retain);
+        super(player, title, upperGui.getSize() + lowerGui.getSize(), upperInventory, closeable);
         this.upperGui = upperGui;
         this.lowerGui = lowerGui;
         
         upperGui.addParent(this);
         lowerGui.addParent(this);
-        if (initItems) initUpperItems();
     }
     
     @Override
@@ -68,46 +67,46 @@ public abstract class AbstractSplitWindow extends AbstractDoubleWindow {
     }
     
     @SuppressWarnings("unchecked")
-    public static abstract class AbstractBuilder<W extends Window, V, S extends Window.Builder.Double<W, V, S>>
+    public static abstract class AbstractBuilder<W extends Window, S extends Window.Builder.Double<W, S>>
-        extends AbstractWindow.AbstractBuilder<W, V, S>
+        extends AbstractWindow.AbstractBuilder<W, S>
-        implements Window.Builder.Double<W, V, S>
+        implements Window.Builder.Double<W, S>
     {
         
         protected Supplier<Gui> upperGuiSupplier;
         protected Supplier<Gui> lowerGuiSupplier;
         
         @Override
-        public S setUpperGui(@NotNull Supplier<Gui> guiSupplier) {
+        public @NotNull S setUpperGui(@NotNull Supplier<Gui> guiSupplier) {
             this.upperGuiSupplier = guiSupplier;
             return (S) this;
         }
         
         @Override
-        public S setUpperGui(@NotNull Gui gui) {
+        public @NotNull S setUpperGui(@NotNull Gui gui) {
             this.upperGuiSupplier = () -> gui;
             return (S) this;
         }
         
         @Override
-        public S setUpperGui(@NotNull Gui.Builder<?, ?> builder) {
+        public @NotNull S setUpperGui(@NotNull Gui.Builder<?, ?> builder) {
             this.upperGuiSupplier = builder::build;
             return (S) this;
         }
         
         @Override
-        public S setLowerGui(@NotNull Supplier<Gui> guiSupplier) {
+        public @NotNull S setLowerGui(@NotNull Supplier<Gui> guiSupplier) {
             this.lowerGuiSupplier = guiSupplier;
             return (S) this;
         }
         
         @Override
-        public S setLowerGui(@NotNull Gui gui) {
+        public @NotNull S setLowerGui(@NotNull Gui gui) {
             this.lowerGuiSupplier = () -> gui;
             return (S) this;
         }
         
         @Override
-        public S setLowerGui(@NotNull Gui.Builder<?, ?> builder) {
+        public @NotNull S setLowerGui(@NotNull Gui.Builder<?, ?> builder) {
             this.lowerGuiSupplier = builder::build;
             return (S) this;
         }

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

@@ -20,6 +20,7 @@ import org.jetbrains.annotations.Nullable;
 import xyz.xenondevs.inventoryaccess.InventoryAccess;
 import xyz.xenondevs.inventoryaccess.component.BaseComponentWrapper;
 import xyz.xenondevs.inventoryaccess.component.ComponentWrapper;
+import xyz.xenondevs.inventoryaccess.component.i18n.Languages;
 import xyz.xenondevs.invui.InvUI;
 import xyz.xenondevs.invui.gui.AbstractGui;
 import xyz.xenondevs.invui.gui.Gui;
@@ -41,25 +42,20 @@ public abstract class AbstractWindow implements Window, GuiParent {
     private static final NamespacedKey SLOT_KEY = new NamespacedKey(InvUI.getInstance().getPlugin(), "slot");
     
     private final UUID viewerUUID;
-    private final boolean retain;
     private final SlotElement[] elementsDisplayed;
+    private List<Runnable> openHandlers;
     private List<Runnable> closeHandlers;
     private ComponentWrapper title;
     private boolean closeable;
-    private boolean removed;
+    private boolean currentlyOpen;
     
-    public AbstractWindow(UUID viewerUUID, ComponentWrapper title, int size, boolean closeable, boolean retain) {
+    public AbstractWindow(UUID viewerUUID, ComponentWrapper title, int size, boolean closeable) {
         this.viewerUUID = viewerUUID;
         this.title = title;
         this.closeable = closeable;
-        this.retain = retain;
         this.elementsDisplayed = new SlotElement[size];
     }
     
-    protected void register() {
-        WindowManager.getInstance().addWindow(this);
-    }
-    
     protected void redrawItem(int index) {
         redrawItem(index, getSlotElement(index), false);
     }
@@ -168,18 +164,29 @@ public abstract class AbstractWindow implements Window, GuiParent {
         event.setCursor(cursorStack);
     }
     
-    public void handleOpen(InventoryOpenEvent event) {
+    public void handleOpenEvent(InventoryOpenEvent event) {
-        if (!event.getPlayer().equals(getViewer()))
+        if (!event.getPlayer().equals(getViewer())) {
             event.setCancelled(true);
-        else handleOpened();
+        } else {
+            if (currentlyOpen)
+                throw new IllegalStateException("Window is already opened!");
+            
+            currentlyOpen = true;
+            handleOpened();
+            
+            if (openHandlers != null) {
+                openHandlers.forEach(Runnable::run);
+            }
+        }
     }
     
-    public void handleClose(Player player) {
+    public void handleCloseEvent(Player player) {
         if (closeable) {
-            if (!retain) {
+            if (!currentlyOpen)
-                remove(false);
+                throw new IllegalStateException("Window is already closed!");
-            }
             
+            currentlyOpen = false;
+            remove(false);
             handleClosed();
             
             if (closeHandlers != null) {
@@ -211,15 +218,7 @@ public abstract class AbstractWindow implements Window, GuiParent {
             && ((SlotElement.VISlotElement) element).getVirtualInventory() == virtualInventory);
     }
     
-    public void remove() {
-        remove(true);
-    }
-    
     public void remove(boolean closeForViewer) {
-        if (removed)
-            return;
-        removed = true;
-        
         WindowManager.getInstance().removeWindow(this);
         
         Arrays.stream(elementsDisplayed)
@@ -252,14 +251,20 @@ public abstract class AbstractWindow implements Window, GuiParent {
     
     @Override
     public void show() {
-        if (removed) throw new IllegalStateException("The Window has already been closed.");
-        
         Player viewer = getViewer();
-        if (viewer == null) throw new IllegalStateException("The player is not online.");
+        if (viewer == null)
+            throw new IllegalStateException("The player is not online.");
+        
+        initItems();
+        WindowManager.getInstance().addWindow(this);
+        openInventory(viewer);
+    }
+    
+    protected void openInventory(@NotNull Player viewer) {
         InventoryAccess.getInventoryUtils().openCustomInventory(
             viewer,
             getInventories()[0],
-            title.localized(viewer.getLocale())
+            title.localized(viewer)
         );
     }
     
@@ -270,7 +275,7 @@ public abstract class AbstractWindow implements Window, GuiParent {
         if (currentViewer != null) {
             InventoryAccess.getInventoryUtils().updateOpenInventoryTitle(
                 currentViewer,
-                title.localized(currentViewer.getLocale())
+                title.localized(currentViewer)
             );
         }
     }
@@ -285,6 +290,19 @@ public abstract class AbstractWindow implements Window, GuiParent {
         changeTitle(TextComponent.fromLegacyText(title));
     }
     
+    @Override
+    public void setOpenHandlers(@NotNull List<@NotNull Runnable> openHandlers) {
+        this.openHandlers = openHandlers;
+    }
+    
+    @Override
+    public void addOpenHandler(@NotNull Runnable openHandler) {
+        if (openHandlers == null)
+            openHandlers = new ArrayList<>();
+        
+        openHandlers.add(openHandler);
+    }
+    
     @Override
     public void setCloseHandlers(@NotNull List<@NotNull Runnable> closeHandlers) {
         this.closeHandlers = closeHandlers;
@@ -321,7 +339,7 @@ public abstract class AbstractWindow implements Window, GuiParent {
         if (player == null)
             throw new IllegalStateException("Tried to receive the language from a viewer that is not online.");
         
-        return player.getLocale();
+        return Languages.getInstance().getLanguage(player);
     }
     
     @Override
@@ -340,8 +358,8 @@ public abstract class AbstractWindow implements Window, GuiParent {
     }
     
     @Override
-    public boolean isRemoved() {
+    public boolean isOpen() {
-        return removed;
+        return currentlyOpen;
     }
     
     protected abstract void setInvItem(int slot, ItemStack itemStack);
@@ -354,6 +372,8 @@ public abstract class AbstractWindow implements Window, GuiParent {
     
     protected abstract Inventory[] getInventories();
     
+    protected abstract void initItems();
+    
     protected abstract void handleOpened();
     
     protected abstract void handleClosed();
@@ -367,59 +387,68 @@ public abstract class AbstractWindow implements Window, GuiParent {
     public abstract void handleViewerDeath(PlayerDeathEvent event);
     
     @SuppressWarnings("unchecked")
-    public static abstract class AbstractBuilder<W extends Window, V, S extends Window.Builder<W, V, S>> implements Window.Builder<W, V, S> {
+    public static abstract class AbstractBuilder<W extends Window, S extends Window.Builder<W, S>> implements Window.Builder<W, S> {
         
-        protected V viewer;
+        protected Player viewer;
         protected ComponentWrapper title;
         protected boolean closeable = true;
-        protected boolean retain = false;
+        protected List<Runnable> openHandlers;
         protected List<Runnable> closeHandlers;
         protected List<Consumer<Window>> modifiers;
         
         @Override
-        public S setViewer(@NotNull V viewer) {
+        public @NotNull S setViewer(@NotNull Player viewer) {
             this.viewer = viewer;
             return (S) this;
         }
         
         @Override
-        public S setTitle(@NotNull ComponentWrapper title) {
+        public @NotNull S setTitle(@NotNull ComponentWrapper title) {
             this.title = title;
             return (S) this;
         }
         
         @Override
-        public S setTitle(@NotNull BaseComponent @NotNull [] title) {
+        public @NotNull S setTitle(@NotNull BaseComponent @NotNull [] title) {
             this.title = new BaseComponentWrapper(title);
             return (S) this;
         }
         
         @Override
-        public S setTitle(@NotNull String title) {
+        public @NotNull S setTitle(@NotNull String title) {
             this.title = new BaseComponentWrapper(TextComponent.fromLegacyText(title));
             return (S) this;
         }
         
         @Override
-        public S setCloseable(boolean closeable) {
+        public @NotNull S setCloseable(boolean closeable) {
             this.closeable = closeable;
             return (S) this;
         }
         
         @Override
-        public S setRetain(boolean retain) {
+        public @NotNull S setOpenHandlers(List<Runnable> openHandlers) {
-            this.retain = retain;
+            this.openHandlers = openHandlers;
             return (S) this;
         }
         
         @Override
-        public S setCloseHandlers(List<Runnable> closeHandlers) {
+        public @NotNull S addOpenHandler(Runnable openHandler) {
+            if (openHandlers == null)
+                openHandlers = new ArrayList<>();
+            
+            openHandlers.add(openHandler);
+            return (S) this;
+        }
+        
+        @Override
+        public @NotNull S setCloseHandlers(List<Runnable> closeHandlers) {
             this.closeHandlers = closeHandlers;
             return (S) this;
         }
         
         @Override
-        public S addCloseHandler(Runnable closeHandler) {
+        public @NotNull S addCloseHandler(Runnable closeHandler) {
             if (closeHandlers == null)
                 closeHandlers = new ArrayList<>();
             
@@ -428,13 +457,13 @@ public abstract class AbstractWindow implements Window, GuiParent {
         }
         
         @Override
-        public S setModifiers(List<Consumer<Window>> modifiers) {
+        public @NotNull S setModifiers(List<Consumer<Window>> modifiers) {
             this.modifiers = modifiers;
             return (S) this;
         }
         
         @Override
-        public S addModifier(Consumer<Window> modifier) {
+        public @NotNull S addModifier(Consumer<Window> modifier) {
             if (modifiers == null)
                 modifiers = new ArrayList<>();
             
@@ -450,11 +479,21 @@ public abstract class AbstractWindow implements Window, GuiParent {
                 modifiers.forEach(modifier -> modifier.accept(window));
         }
         
+        @Override
+        public @NotNull W build() {
+            return build(viewer);
+        }
+        
+        @Override
+        public void show(Player viewer) {
+            build(viewer).show();
+        }
+        
         @SuppressWarnings("unchecked")
         @Override
         public @NotNull S clone() {
             try {
-                var clone = (AbstractBuilder<W, V, S>) super.clone();
+                var clone = (AbstractBuilder<W, S>) super.clone();
                 if (title != null)
                     clone.title = title.clone();
                 if (closeHandlers != null)
@@ -469,5 +508,4 @@ public abstract class AbstractWindow implements Window, GuiParent {
         
     }
     
-    
 }

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

@@ -22,15 +22,11 @@ final class AnvilSingleWindowImpl extends AbstractSingleWindow implements AnvilW
         @Nullable ComponentWrapper title,
         @NotNull AbstractGui gui,
         @Nullable List<@NotNull Consumer<@NotNull String>> renameHandlers,
-        boolean closable,
+        boolean closable
-        boolean retain
     ) {
-        super(player.getUniqueId(), title, gui, null, false, closable, retain);
+        super(player.getUniqueId(), title, gui, null, closable);
-        anvilInventory = InventoryAccess.createAnvilInventory(player, title, renameHandlers);
+        anvilInventory = InventoryAccess.createAnvilInventory(player, title.localized(player), renameHandlers);
         inventory = anvilInventory.getBukkitInventory();
-        
-        initItems();
-        register();
     }
     
     @Override
@@ -39,11 +35,7 @@ final class AnvilSingleWindowImpl extends AbstractSingleWindow implements AnvilW
     }
     
     @Override
-    public void show() {
+    protected void openInventory(@NotNull Player viewer) {
-        if (isRemoved()) throw new IllegalStateException("The Window has already been closed.");
-        
-        Player viewer = getViewer();
-        if (viewer == null) throw new IllegalStateException("The player is not online.");
         anvilInventory.open();
     }
     
@@ -53,7 +45,7 @@ final class AnvilSingleWindowImpl extends AbstractSingleWindow implements AnvilW
     }
     
     public static final class BuilderImpl
-        extends AbstractSingleWindow.AbstractBuilder<AnvilWindow, Player, AnvilWindow.Builder.Single>
+        extends AbstractSingleWindow.AbstractBuilder<AnvilWindow, AnvilWindow.Builder.Single>
         implements AnvilWindow.Builder.Single
     {
         
@@ -75,7 +67,7 @@ final class AnvilSingleWindowImpl extends AbstractSingleWindow implements AnvilW
         }
         
         @Override
-        public @NotNull AnvilWindow build() {
+        public @NotNull AnvilWindow build(Player viewer) {
             if (viewer == null)
                 throw new IllegalStateException("Viewer is not defined.");
             if (guiSupplier == null)
@@ -86,8 +78,7 @@ final class AnvilSingleWindowImpl extends AbstractSingleWindow implements AnvilW
                 title,
                 (AbstractGui) guiSupplier.get(),
                 renameHandlers,
-                closeable,
+                closeable
-                retain
             );
             
             applyModifiers(window);

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

@@ -23,16 +23,12 @@ final class AnvilSplitWindowImpl extends AbstractSplitWindow implements AnvilWin
         @NotNull AbstractGui upperGui,
         @NotNull AbstractGui lowerGui,
         @Nullable List<@NotNull Consumer<@NotNull String>> renameHandlers,
-        boolean closeable,
+        boolean closeable
-        boolean retain
     ) {
-        super(player, title, upperGui, lowerGui, null, false, closeable, retain);
+        super(player, title, upperGui, lowerGui, null, closeable);
         
-        anvilInventory = InventoryAccess.createAnvilInventory(player, title, renameHandlers);
+        anvilInventory = InventoryAccess.createAnvilInventory(player, title.localized(player), renameHandlers);
         upperInventory = anvilInventory.getBukkitInventory();
-        
-        initUpperItems();
-        register();
     }
     
     @Override
@@ -41,11 +37,7 @@ final class AnvilSplitWindowImpl extends AbstractSplitWindow implements AnvilWin
     }
     
     @Override
-    public void show() {
+    protected void openInventory(@NotNull Player viewer) {
-        if (isRemoved()) throw new IllegalStateException("The Window has already been closed.");
-        
-        Player viewer = getViewer();
-        if (viewer == null) throw new IllegalStateException("The player is not online.");
         anvilInventory.open();
     }
     
@@ -55,7 +47,7 @@ final class AnvilSplitWindowImpl extends AbstractSplitWindow implements AnvilWin
     }
     
     public static final class BuilderImpl
-        extends AbstractSplitWindow.AbstractBuilder<AnvilWindow, Player, AnvilWindow.Builder.Split>
+        extends AbstractSplitWindow.AbstractBuilder<AnvilWindow, AnvilWindow.Builder.Split>
         implements AnvilWindow.Builder.Split
     {
         
@@ -77,7 +69,7 @@ final class AnvilSplitWindowImpl extends AbstractSplitWindow implements AnvilWin
         }
         
         @Override
-        public @NotNull AnvilWindow build() {
+        public @NotNull AnvilWindow build(Player viewer) {
             if (viewer == null)
                 throw new IllegalStateException("Viewer is not defined.");
             if (upperGuiSupplier == null)
@@ -91,8 +83,7 @@ final class AnvilSplitWindowImpl extends AbstractSplitWindow implements AnvilWin
                 (AbstractGui) upperGuiSupplier.get(),
                 (AbstractGui) lowerGuiSupplier.get(),
                 renameHandlers,
-                closeable,
+                closeable
-                retain
             );
             
             applyModifiers(window);

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

@@ -65,7 +65,7 @@ public interface AnvilWindow extends Window {
      * @see Window.Builder.Normal
      * @see CartographyWindow.Builder
      */
-    interface Builder<S extends Builder<S>> extends Window.Builder<AnvilWindow, Player, S> {
+    interface Builder<S extends Builder<S>> extends Window.Builder<AnvilWindow, S> {
     
         /**
          * Sets the rename handlers of the {@link AnvilWindow}.
@@ -90,7 +90,7 @@ public interface AnvilWindow extends Window {
          * @see Window.Builder.Normal.Single
          * @see CartographyWindow.Builder.Single
          */
-        interface Single extends Builder<Single>, Window.Builder.Single<AnvilWindow, Player, Single> {}
+        interface Single extends Builder<Single>, Window.Builder.Single<AnvilWindow, Single> {}
     
         /**
          * A split {@link AnvilWindow} builder. Combines both {@link AnvilWindow.Builder} and {@link Window.Builder.Double}
@@ -100,7 +100,7 @@ public interface AnvilWindow extends Window {
          * @see Window.Builder.Normal.Split
          * @see CartographyWindow.Builder.Split
          */
-        interface Split extends Builder<Split>, Window.Builder.Double<AnvilWindow, Player, Split> {}
+        interface Split extends Builder<Split>, Window.Builder.Double<AnvilWindow, Split> {}
         
     }
     

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

@@ -26,18 +26,15 @@ final class CartographySingleWindowImpl extends AbstractSingleWindow implements
         @NotNull Player player,
         @Nullable ComponentWrapper title,
         @NotNull AbstractGui gui,
-        boolean closeable,
+        boolean closeable
-        boolean retain
     ) {
-        super(player.getUniqueId(), title, gui, null, false, closeable, retain);
+        super(player.getUniqueId(), title, gui, null, closeable);
         if (gui.getWidth() != 2 || gui.getHeight() != 1) throw new IllegalArgumentException("Gui has to be 2x1");
         
-        cartographyInventory = InventoryAccess.createCartographyInventory(player, title);
+        cartographyInventory = InventoryAccess.createCartographyInventory(player, title.localized(player));
         inventory = cartographyInventory.getBukkitInventory();
         
-        initItems();
         resetMap();
-        register();
     }
     
     @Override
@@ -71,23 +68,17 @@ final class CartographySingleWindowImpl extends AbstractSingleWindow implements
     }
     
     @Override
-    public void show() {
+    protected void openInventory(@NotNull Player viewer) {
-        if (isRemoved())
-            throw new IllegalStateException("The Window has already been closed.");
-        
-        Player viewer = getViewer();
-        if (viewer == null)
-            throw new IllegalStateException("The player is not online.");
         cartographyInventory.open();
     }
     
     public static final class BuilderImpl 
-        extends AbstractSingleWindow.AbstractBuilder<CartographyWindow, Player, CartographyWindow.Builder.Single>
+        extends AbstractSingleWindow.AbstractBuilder<CartographyWindow, CartographyWindow.Builder.Single>
         implements CartographyWindow.Builder.Single
     {
         
         @Override
-        public @NotNull CartographyWindow build() {
+        public @NotNull CartographyWindow build(Player viewer) {
             if (viewer == null)
                 throw new IllegalStateException("Viewer is not defined.");
             if (guiSupplier == null)
@@ -97,8 +88,7 @@ final class CartographySingleWindowImpl extends AbstractSingleWindow implements
                 viewer,
                 title,
                 (AbstractGui) guiSupplier.get(),
-                closeable,
+                closeable
-                retain
             );
             
             applyModifiers(window);

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

@@ -27,17 +27,14 @@ final class CartographySplitWindowImpl extends AbstractSplitWindow implements Ca
         @Nullable ComponentWrapper title,
         @NotNull AbstractGui upperGui,
         @NotNull AbstractGui lowerGui,
-        boolean closeable,
+        boolean closeable
-        boolean retain
     ) {
-        super(player, title, createWrappingGui(upperGui), lowerGui, null, false, closeable, retain);
+        super(player, title, createWrappingGui(upperGui), lowerGui, null, closeable);
         
-        cartographyInventory = InventoryAccess.createCartographyInventory(player, title);
+        cartographyInventory = InventoryAccess.createCartographyInventory(player, title.localized(player));
         upperInventory = cartographyInventory.getBukkitInventory();
         
-        initUpperItems();
         resetMap();
-        register();
     }
     
     private static AbstractGui createWrappingGui(Gui upperGui) {
@@ -66,23 +63,17 @@ final class CartographySplitWindowImpl extends AbstractSplitWindow implements Ca
     }
     
     @Override
-    public void show() {
+    protected void openInventory(@NotNull Player viewer) {
-        if (isRemoved())
-            throw new IllegalStateException("The Window has already been closed.");
-        
-        Player viewer = getViewer();
-        if (viewer == null)
-            throw new IllegalStateException("The player is not online.");
         cartographyInventory.open();
     }
     
     public static final class BuilderImpl
-        extends AbstractSplitWindow.AbstractBuilder<CartographyWindow, Player, CartographyWindow.Builder.Split>
+        extends AbstractSplitWindow.AbstractBuilder<CartographyWindow, CartographyWindow.Builder.Split>
         implements CartographyWindow.Builder.Split
     {
         
         @Override
-        public @NotNull CartographyWindow build() {
+        public @NotNull CartographyWindow build(Player viewer) {
             if (viewer == null)
                 throw new IllegalStateException("Viewer is not defined.");
             if (upperGuiSupplier == null)
@@ -93,8 +84,7 @@ final class CartographySplitWindowImpl extends AbstractSplitWindow implements Ca
                 title,
                 (AbstractGui) upperGuiSupplier.get(),
                 (AbstractGui) lowerGuiSupplier.get(),
-                closeable,
+                closeable
-                retain
             );
             
             applyModifiers(window);

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

@@ -95,21 +95,21 @@ public interface CartographyWindow extends Window {
      * @see Window.Builder.Normal
      * @see Window.Builder
      */
-    interface Builder<S extends Builder<S>> extends Window.Builder<CartographyWindow, Player, S> {
+    interface Builder<S extends Builder<S>> extends Window.Builder<CartographyWindow, S> {
         
         /**
          * A single {@link CartographyWindow} builder. Combines both {@link CartographyWindow.Builder} an
          * {@link Window.Builder.Single} for a {@link CartographyWindow} with only one {@link Gui} that does not
          * access the {@link Player Player's} inventory.
          */
-        interface Single extends Builder<Single>, Window.Builder.Single<CartographyWindow, Player, Single> {}
+        interface Single extends Builder<Single>, Window.Builder.Single<CartographyWindow, Single> {}
         
         /**
          * A split {@link CartographyWindow} builder. Combines both {@link CartographyWindow.Builder} an
          * {@link Window.Builder.Double} for a {@link CartographyWindow} with two {@link Gui Guis}, where the lower
          * {@link Gui} is used to fill the {@link Player Player's} inventory.
          */
-        interface Split extends Builder<Split>, Window.Builder.Double<CartographyWindow, Player, Split> {}
+        interface Split extends Builder<Split>, Window.Builder.Double<CartographyWindow, Split> {}
         
     }
     

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

@@ -15,11 +15,9 @@ final class NormalMergedWindowImpl extends AbstractMergedWindow {
         @NotNull Player player,
         @Nullable ComponentWrapper title,
         @NotNull AbstractGui gui,
-        boolean closeable,
+        boolean closeable
-        boolean retain
     ) {
-        super(player, title, gui, createInventory(gui), closeable, retain);
+        super(player, title, gui, createInventory(gui), closeable);
-        register();
     }
     
     private static Inventory createInventory(Gui gui) {
@@ -32,12 +30,12 @@ final class NormalMergedWindowImpl extends AbstractMergedWindow {
     }
     
     public static final class BuilderImpl
-        extends AbstractSingleWindow.AbstractBuilder<Window, Player, Window.Builder.Normal.Merged>
+        extends AbstractSingleWindow.AbstractBuilder<Window, Window.Builder.Normal.Merged>
         implements Window.Builder.Normal.Merged
     {
         
         @Override
-        public @NotNull Window build() {
+        public @NotNull Window build(Player viewer) {
             if (viewer == null)
                 throw new IllegalStateException("Viewer is not defined.");
             if (guiSupplier == null)
@@ -47,8 +45,7 @@ final class NormalMergedWindowImpl extends AbstractMergedWindow {
                 viewer,
                 title,
                 (AbstractGui) guiSupplier.get(),
-                closeable,
+                closeable
-                retain
             );
             
             applyModifiers(window);

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

@@ -1,41 +1,30 @@
 package xyz.xenondevs.invui.window;
 
-import org.bukkit.OfflinePlayer;
+import org.bukkit.entity.Player;
-import org.jetbrains.annotations.Contract;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import xyz.xenondevs.inventoryaccess.component.ComponentWrapper;
 import xyz.xenondevs.invui.gui.AbstractGui;
 import xyz.xenondevs.invui.util.InventoryUtils;
 
-import java.util.UUID;
-
 final class NormalSingleWindowImpl extends AbstractSingleWindow {
     
     public NormalSingleWindowImpl(
-        @NotNull UUID viewerUUID,
+        @NotNull Player player,
         @Nullable ComponentWrapper title,
         @NotNull AbstractGui gui,
-        boolean closeable,
+        boolean closeable
-        boolean retain
     ) {
-        super(viewerUUID, title, gui, InventoryUtils.createMatchingInventory(gui, ""), true, closeable, retain);
+        super(player.getUniqueId(), title, gui, InventoryUtils.createMatchingInventory(gui, ""), closeable);
-        register();
     }
     
     public static final class BuilderImpl 
-        extends AbstractSingleWindow.AbstractBuilder<Window, UUID, Window.Builder.Normal.Single> 
+        extends AbstractSingleWindow.AbstractBuilder<Window, Window.Builder.Normal.Single> 
         implements Window.Builder.Normal.Single
     {
         
-        @Contract("_ -> this")
-        public BuilderImpl setViewer(@NotNull OfflinePlayer player) {
-            setViewer(player.getUniqueId());
-            return this;
-        }
-        
         @Override
-        public @NotNull Window build() {
+        public @NotNull Window build(Player viewer) {
             if (viewer == null)
                 throw new IllegalStateException("Viewer is not defined.");
             if (guiSupplier == null)
@@ -45,8 +34,7 @@ final class NormalSingleWindowImpl extends AbstractSingleWindow {
                 viewer,
                 title,
                 (AbstractGui) guiSupplier.get(),
-                closeable,
+                closeable
-                retain
             );
             
             applyModifiers(window);

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

@@ -14,20 +14,18 @@ final class NormalSplitWindowImpl extends AbstractSplitWindow {
         @Nullable ComponentWrapper title,
         @NotNull AbstractGui upperGui,
         @NotNull AbstractGui lowerGui,
-        boolean closeable,
+        boolean closeable
-        boolean retain
     ) {
-        super(player, title, upperGui, lowerGui, InventoryUtils.createMatchingInventory(upperGui, ""), true, closeable, retain);
+        super(player, title, upperGui, lowerGui, InventoryUtils.createMatchingInventory(upperGui, ""), closeable);
-        register();
     }
     
     public static final class BuilderImpl
-        extends AbstractSplitWindow.AbstractBuilder<Window, Player, Window.Builder.Normal.Split>
+        extends AbstractSplitWindow.AbstractBuilder<Window, Window.Builder.Normal.Split>
         implements Window.Builder.Normal.Split
     {
         
         @Override
-        public @NotNull Window build() {
+        public @NotNull Window build(Player viewer) {
             if (viewer == null)
                 throw new IllegalStateException("Viewer is not defined.");
             if (upperGuiSupplier == null)
@@ -40,8 +38,7 @@ final class NormalSplitWindowImpl extends AbstractSplitWindow {
                 title,
                 (AbstractGui) upperGuiSupplier.get(),
                 (AbstractGui) lowerGuiSupplier.get(),
-                closeable,
+                closeable
-                retain
             );
             
             applyModifiers(window);

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

@@ -1,7 +1,6 @@
 package xyz.xenondevs.invui.window;
 
 import net.md_5.bungee.api.chat.BaseComponent;
-import org.bukkit.OfflinePlayer;
 import org.bukkit.entity.Player;
 import org.bukkit.inventory.Inventory;
 import org.jetbrains.annotations.Contract;
@@ -113,17 +112,11 @@ public interface Window {
     void close();
     
     /**
-     * Gets if the {@link Window} is closed and can't be shown again.
+     * Gets if the viewer is currently viewing this {@link Window}.
      *
-     * @return If the {@link Window} is closed.
+     * @return If the {@link Window} is currently open.
      */
-    boolean isRemoved();
+    boolean isOpen();
-    
-    /**
-     * Removes the {@link Window} from the {@link WindowManager} list.
-     * If this method is called, the {@link Window} can't be shown again.
-     */
-    void remove();
     
     /**
      * Changes the title of the {@link Inventory}.
@@ -168,6 +161,20 @@ public interface Window {
      */
     @NotNull UUID getViewerUUID();
     
+    /**
+     * Replaces the currently registered open handlers with the given list.
+     *
+     * @param openHandlers The new open handlers
+     */
+    void setOpenHandlers(@NotNull List<@NotNull Runnable> openHandlers);
+    
+    /**
+     * Adds an open handler that will be called when this window gets opened.
+     *
+     * @param openHandler The close handler to add
+     */
+    void addOpenHandler(@NotNull Runnable openHandler);
+    
     /**
      * Replaces the currently registered close handlers with the given list.
      *
@@ -193,10 +200,9 @@ public interface Window {
      * A {@link Window} builder.
      *
      * @param <W> The window type
-     * @param <V> The viewer type
      * @param <S> The builder type
      */
-    interface Builder<W extends Window, V, S extends Builder<W, V, S>> extends Cloneable {
+    interface Builder<W extends Window, S extends Builder<W, S>> extends Cloneable {
         
         /**
          * Sets the viewer of the {@link Window}.
@@ -205,7 +211,7 @@ public interface Window {
          * @return This {@link Builder Window Builder}
          */
         @Contract("_ -> this")
-        S setViewer(@NotNull V viewer);
+        @NotNull S setViewer(@NotNull Player viewer);
         
         /**
          * Sets the title of the {@link Window}.
@@ -214,7 +220,7 @@ public interface Window {
          * @return This {@link Builder Window Builder}
          */
         @Contract("_ -> this")
-        S setTitle(@NotNull ComponentWrapper title);
+        @NotNull S setTitle(@NotNull ComponentWrapper title);
         
         /**
          * Sets the title of the {@link Window}.
@@ -223,7 +229,7 @@ public interface Window {
          * @return This {@link Builder Window Builder}
          */
         @Contract("_ -> this")
-        S setTitle(@NotNull BaseComponent @NotNull [] title);
+        @NotNull S setTitle(@NotNull BaseComponent @NotNull [] title);
         
         /**
          * Sets the title of the {@link Window}.
@@ -232,7 +238,7 @@ public interface Window {
          * @return This {@link Builder Window Builder}
          */
         @Contract("_ -> this")
-        S setTitle(@NotNull String title);
+        @NotNull S setTitle(@NotNull String title);
         
         /**
          * Configures if the {@link Window} is closeable.
@@ -241,16 +247,25 @@ public interface Window {
          * @return This {@link Builder Window Builder}
          */
         @Contract("_ -> this")
-        S setCloseable(boolean closeable);
+        @NotNull S setCloseable(boolean closeable);
         
         /**
-         * Configures if the {@link Window} should be retained after it has been closed.
+         * Sets the open handlers of the {@link Window}.
          *
-         * @param retain If the {@link Window} should be retained
+         * @param openHandlers The open handlers of the {@link Window}
          * @return This {@link Builder Window Builder}
          */
         @Contract("_ -> this")
-        S setRetain(boolean retain);
+        @NotNull S setOpenHandlers(List<Runnable> openHandlers);
+        
+        /**
+         * Adds an open handler to the {@link Window}.
+         *
+         * @param openHandler The open handler to add
+         * @return This {@link Builder Window Builder}
+         */
+        @Contract("_ -> this")
+        @NotNull S addOpenHandler(Runnable openHandler);
         
         /**
          * Sets the close handlers of the {@link Window}.
@@ -259,7 +274,7 @@ public interface Window {
          * @return This {@link Builder Window Builder}
          */
         @Contract("_ -> this")
-        S setCloseHandlers(List<Runnable> closeHandlers);
+        @NotNull S setCloseHandlers(List<Runnable> closeHandlers);
         
         /**
          * Adds a close handler to the {@link Window}.
@@ -268,7 +283,7 @@ public interface Window {
          * @return This {@link Builder Window Builder}
          */
         @Contract("_ -> this")
-        S addCloseHandler(Runnable closeHandler);
+        @NotNull S addCloseHandler(Runnable closeHandler);
         
         /**
          * Sets the modifiers of the {@link Window}.
@@ -277,7 +292,7 @@ public interface Window {
          * @return This {@link Builder Window Builder}
          */
         @Contract("_ -> this")
-        S setModifiers(List<Consumer<Window>> modifiers);
+        @NotNull S setModifiers(List<Consumer<Window>> modifiers);
         
         /**
          * Adds a modifier to the {@link Window}.
@@ -286,7 +301,7 @@ public interface Window {
          * @return This {@link Builder Window Builder}
          */
         @Contract("_ -> this")
-        S addModifier(Consumer<Window> modifier);
+        @NotNull S addModifier(Consumer<Window> modifier);
         
         /**
          * Builds the {@link Window}.
@@ -296,6 +311,23 @@ public interface Window {
         @Contract("-> new")
         @NotNull W build();
         
+        /**
+         * Builds the {@link Window} with the specified viewer.
+         * If this method is used, the viewer does not need to be set using {@link #setViewer(Player)}.
+         *
+         * @param viewer The {@link Player} to build the {@link Window} for.
+         */
+        @Contract("_ -> new")
+        @NotNull W build(Player viewer);
+        
+        /**
+         * Builds and shows the {@link Window} to the specified viewer.
+         * If this method is used, the viewer does not need to be set using {@link #setViewer(Player)}.
+         *
+         * @param viewer The {@link Player} to show the {@link Window} to.
+         */
+        void show(Player viewer);
+        
         /**
          * Clones the {@link Builder Window Builder}.
          *
@@ -308,15 +340,13 @@ public interface Window {
          * A single {@link Window} builder. Single Windows only have on {@link Gui}.
          *
          * @param <W> The window type
-         * @param <V> The viewer type
          * @param <S> The builder type
-         *           
          * @see Window.Builder.Normal.Single
          * @see Window.Builder.Normal.Merged
          * @see AnvilWindow.Builder.Single
          * @see CartographyWindow.Builder.Single
          */
-        interface Single<W extends Window, V, S extends Single<W, V, S>> extends Builder<W, V, S> {
+        interface Single<W extends Window, S extends Single<W, S>> extends Builder<W, S> {
             
             /**
              * Sets the {@link Gui} of the {@link Window}.
@@ -325,7 +355,7 @@ public interface Window {
              * @return This {@link Single Window Builder}
              */
             @Contract("_ -> this")
-            S setGui(@NotNull Gui gui);
+            @NotNull S setGui(@NotNull Gui gui);
             
             /**
              * Sets the {@link Gui.Builder} for this {@link Single Window Builder}.
@@ -335,7 +365,7 @@ public interface Window {
              * @return This {@link Single Window Builder}
              */
             @Contract("_ -> this")
-            S setGui(@NotNull Gui.Builder<?, ?> builder);
+            @NotNull S setGui(@NotNull Gui.Builder<?, ?> builder);
             
             /**
              * Sets the {@link Gui} {@link Supplier} for this {@link Single Window Builder}.
@@ -345,7 +375,7 @@ public interface Window {
              * @return This {@link Single Window Builder}
              */
             @Contract("_ -> this")
-            S setGui(@NotNull Supplier<Gui> guiSupplier);
+            @NotNull S setGui(@NotNull Supplier<Gui> guiSupplier);
             
         }
         
@@ -353,14 +383,12 @@ public interface Window {
          * A double {@link Window} builder. Double Windows have two {@link Gui Guis}.
          *
          * @param <W> The window type
-         * @param <V> The viewer type
          * @param <S> The builder type
-         *           
          * @see Window.Builder.Normal.Split
          * @see AnvilWindow.Builder.Split
          * @see CartographyWindow.Builder.Split
          */
-        interface Double<W extends Window, V, S extends Builder.Double<W, V, S>> extends Builder<W, V, S> {
+        interface Double<W extends Window, S extends Builder.Double<W, S>> extends Builder<W, S> {
             
             /**
              * Sets the upper {@link Gui} of the {@link Window}.
@@ -369,7 +397,7 @@ public interface Window {
              * @return This {@link Double Window Builder}
              */
             @Contract("_ -> this")
-            S setUpperGui(@NotNull Gui gui);
+            @NotNull S setUpperGui(@NotNull Gui gui);
             
             /**
              * Sets the {@link Gui.Builder} for the upper {@link Gui} of this {@link Double Window Builder}.
@@ -379,7 +407,7 @@ public interface Window {
              * @return This {@link Double Window Builder}
              */
             @Contract("_ -> this")
-            S setUpperGui(@NotNull Gui.Builder<?, ?> builder);
+            @NotNull S setUpperGui(@NotNull Gui.Builder<?, ?> builder);
             
             /**
              * Sets the {@link Gui} {@link Supplier} for the upper {@link Gui} of this {@link Double Window Builder}.
@@ -389,7 +417,7 @@ public interface Window {
              * @return This {@link Double Window Builder}
              */
             @Contract("_ -> this")
-            S setUpperGui(@NotNull Supplier<Gui> guiSupplier);
+            @NotNull S setUpperGui(@NotNull Supplier<Gui> guiSupplier);
             
             /**
              * Sets the lower {@link Gui} of the {@link Window}.
@@ -398,7 +426,7 @@ public interface Window {
              * @return This {@link Double Window Builder}
              */
             @Contract("_ -> this")
-            S setLowerGui(@NotNull Gui gui);
+            @NotNull S setLowerGui(@NotNull Gui gui);
             
             /**
              * Sets the {@link Gui.Builder} for the lower {@link Gui} of this {@link Double Window Builder}.
@@ -408,7 +436,7 @@ public interface Window {
              * @return This {@link Double Window Builder}
              */
             @Contract("_ -> this")
-            S setLowerGui(@NotNull Gui.Builder<?, ?> builder);
+            @NotNull S setLowerGui(@NotNull Gui.Builder<?, ?> builder);
             
             /**
              * Sets the {@link Gui} {@link Supplier} for the lower {@link Gui} of this {@link Double Window Builder}.
@@ -418,7 +446,7 @@ public interface Window {
              * @return This {@link Double Window Builder}
              */
             @Contract("_ -> this")
-            S setLowerGui(@NotNull Supplier<Gui> guiSupplier);
+            @NotNull S setLowerGui(@NotNull Supplier<Gui> guiSupplier);
             
         }
         
@@ -426,50 +454,37 @@ public interface Window {
          * A normal {@link Window} builder for {@link Window Windows} of inventories with no special functionality, such
          * as chests, hoppers and droppers.
          *
-         * @param <V> The viewer type
          * @param <S> The builder type
-         *           
          * @see AnvilWindow.Builder
          * @see CartographyWindow.Builder
          */
-        interface Normal<V, S extends Normal<V, S>> extends Builder<Window, V, S> {
+        interface Normal<V, S extends Normal<V, S>> extends Builder<Window, S> {
             
             /**
              * A normal single {@link Window} builder. Combines both {@link Builder.Single} and {@link Builder.Normal}
              * for a normal {@link Window} with only one {@link Gui} that does not access the {@link Player Player's} inventory.
-             * 
+             *
              * @see AnvilWindow.Builder.Single
              * @see CartographyWindow.Builder.Single
              */
-            interface Single extends Builder.Normal<UUID, Single>, Builder.Single<Window, UUID, Single> {
+            interface Single extends Builder.Normal<UUID, Single>, Builder.Single<Window, Single> {}
-                
-                /**
-                 * Sets the viewer of the {@link Window}.
-                 *
-                 * @param viewer The viewer of the {@link Window}
-                 * @return This {@link Normal.Single Window Builder}
-                 */
-                @Contract("_ -> this")
-                Normal.Single setViewer(@NotNull OfflinePlayer viewer);
-                
-            }
             
             /**
              * A normal split {@link Window} builder. Combines both {@link Builder.Double} and {@link Builder.Normal}
              * for a normal {@link Window} with two {@link Gui Guis}, where the lower {@link Gui} is used to fill the
              * {@link Player Player's} inventory.
-             * 
+             *
              * @see AnvilWindow.Builder.Split
              * @see CartographyWindow.Builder.Split
              */
-            interface Split extends Builder.Normal<Player, Split>, Builder.Double<Window, Player, Split> {}
+            interface Split extends Builder.Normal<Player, Split>, Builder.Double<Window, Split> {}
             
             /**
              * A normal merged {@link Window} builder. Combines both {@link Builder.Single} and {@link Builder.Normal}
              * for a normal {@link Window} with one {@link Gui}, which fills both the upper inventory and the
              * {@link Player Player's} inventory.
              */
-            interface Merged extends Builder.Normal<Player, Merged>, Builder.Single<Window, Player, Merged> {}
+            interface Merged extends Builder.Normal<Player, Merged>, Builder.Single<Window, Merged> {}
             
         }
         

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

@@ -152,7 +152,7 @@ public class WindowManager implements Listener {
         
         AbstractWindow window = (AbstractWindow) getWindow(event.getInventory());
         if (window != null)
-            window.handleClose(player);
+            window.handleCloseEvent(player);
         
         openWindows.remove(player);
     }
@@ -161,7 +161,7 @@ public class WindowManager implements Listener {
     private void handleInventoryOpen(InventoryOpenEvent event) {
         AbstractWindow window = (AbstractWindow) getWindow(event.getInventory());
         if (window != null) {
-            window.handleOpen(event);
+            window.handleOpenEvent(event);
             openWindows.put((Player) event.getPlayer(), window);
         }
     }
@@ -171,7 +171,7 @@ public class WindowManager implements Listener {
         Player player = event.getPlayer();
         AbstractWindow window = (AbstractWindow) getOpenWindow(player);
         if (window != null) {
-            window.handleClose(player);
+            window.handleCloseEvent(player);
             openWindows.remove(player);
         }
     }