Improved GUIBuilder & ControlItems

src/main/java/de/studiocode/invui/gui/Controllable.java

@@ -0,0 +1,9 @@
+package de.studiocode.invui.gui;
+
+import de.studiocode.invui.item.impl.controlitem.ControlItem;
+
+public interface Controllable {
+    
+    void addControlItem(int index, ControlItem<?> controlItem);
+    
+}

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

@@ -3,8 +3,6 @@ package de.studiocode.invui.gui;
 import de.studiocode.invui.animation.Animation;
 import de.studiocode.invui.gui.SlotElement.ItemStackHolder;
 import de.studiocode.invui.gui.builder.GUIBuilder;
-import de.studiocode.invui.gui.builder.PagedGUIBuilder;
-import de.studiocode.invui.gui.builder.TabGUIBuilder;
 import de.studiocode.invui.gui.impl.*;
 import de.studiocode.invui.item.Item;
 import de.studiocode.invui.virtualinventory.VirtualInventory;
@@ -38,8 +36,6 @@ import java.util.function.Predicate;
  * @see SimplePagedGUIsGUI
  * @see SimpleTabGUI
  * @see GUIBuilder
- * @see PagedGUIBuilder
- * @see TabGUIBuilder
  */
 public interface GUI extends GUIParent {
     

src/main/java/de/studiocode/invui/gui/builder/GUIBuilder.java

@@ -2,15 +2,19 @@ package de.studiocode.invui.gui.builder;
 
 import de.studiocode.invui.gui.GUI;
 import de.studiocode.invui.gui.SlotElement;
-import de.studiocode.invui.gui.impl.SimpleGUI;
+import de.studiocode.invui.gui.SlotElement.ItemSlotElement;
+import de.studiocode.invui.gui.impl.*;
 import de.studiocode.invui.item.Item;
+import de.studiocode.invui.item.impl.SimpleItem;
+import de.studiocode.invui.item.itembuilder.ItemBuilder;
 import org.bukkit.inventory.ShapedRecipe;
 import org.jetbrains.annotations.NotNull;
 
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
-import java.util.Map;
+
+import static de.studiocode.invui.gui.builder.GUIType.*;
 
 /**
  * A builder class to easily construct {@link GUI}s.<br>
@@ -19,151 +23,138 @@ import java.util.Map;
  */
 public class GUIBuilder {
     
-    protected final int width;
+    private final GUIType guiType;
-    protected final int height;
+    private final int width;
-    private final int size;
+    private final int height;
-    
+    private final HashMap<Character, Ingredient> ingredientMap = new HashMap<>();
-    private final Map<Character, Ingredient> ingredientMap = new HashMap<>();
     
     private String structure;
     
-    public GUIBuilder(int width, int height) {
+    private List<Item> items = new ArrayList<>();
+    private List<GUI> guis = new ArrayList<>();
+    
+    public GUIBuilder(@NotNull GUIType guiType, int width, int height) {
+        this.guiType = guiType;
         this.width = width;
         this.height = height;
-        this.size = width * height;
     }
     
-    /**
+    public GUIBuilder setStructure(@NotNull String structure) {
-     * Builds the {@link GUI}.
+        String trimmedStructure = structure
-     *
+            .replace(" ", "")
-     * @return The built {@link GUI}
+            .replace("\n", "");
-     */
+        
+        if (trimmedStructure.length() != width * height)
+            throw new IllegalArgumentException("Structure size does not match GUI size");
+        
+        this.structure = trimmedStructure;
+        return this;
+    }
+    
+    public GUIBuilder setIngredient(char key, @NotNull ItemBuilder itemBuilder) {
+        return setIngredient(key, new SimpleItem(itemBuilder));
+    }
+    
+    public GUIBuilder setIngredient(char key, @NotNull Item item) {
+        return setIngredient(key, new ItemSlotElement(item));
+    }
+    
+    public GUIBuilder setIngredient(char key, @NotNull SlotElement element) {
+        ingredientMap.put(key, new Ingredient(element));
+        return this;
+    }
+    
+    public GUIBuilder setMarker(char key, @NotNull Marker marker) {
+        ingredientMap.put(key, new Ingredient(marker));
+        return this;
+    }
+    
+    public GUIBuilder setItems(@NotNull List<Item> items) {
+        if (guiType != PAGED_ITEMS && guiType != SCROLL)
+            throw new UnsupportedOperationException("Items cannot be set in this gui type.");
+        this.items = items;
+        return this;
+    }
+    
+    public GUIBuilder addItem(@NotNull Item item) {
+        if (guiType != PAGED_ITEMS && guiType != SCROLL)
+            throw new UnsupportedOperationException("Items cannot be set in this gui type.");
+        items.add(item);
+        return this;
+    }
+    
+    public GUIBuilder setGUIs(@NotNull List<GUI> guis) {
+        if (guiType != PAGED_GUIs)
+            throw new UnsupportedOperationException("GUIs cannot be set in this gui type.");
+        this.guis = guis;
+        return this;
+    }
+    
+    public GUIBuilder addGUI(@NotNull GUI gui) {
+        if (guiType != PAGED_GUIs)
+            throw new UnsupportedOperationException("GUIs cannot be set in this gui type.");
+        guis.add(gui);
+        return this;
+    }
+    
     public GUI build() {
+        IngredientList ingredients = new IngredientList(structure, ingredientMap);
+        
+        switch (guiType) {
+            
+            case NORMAL:
+                return buildSimpleGUI(ingredients);
+            
+            case PAGED_ITEMS:
+                return buildSimplePagedItemsGUI(ingredients);
+            
+            case PAGED_GUIs:
+                return buildSimplePagedGUIsGUI(ingredients);
+            
+            case TAB:
+                return buildSimpleTabGUI(ingredients);
+            
+            case SCROLL:
+                return buildSimpleScrollGUI(ingredients);
+            
+            default:
+                throw new UnsupportedOperationException("Unknown GUI type");
+        }
+    }
+    
+    private SimpleGUI buildSimpleGUI(IngredientList ingredients) {
         SimpleGUI gui = new SimpleGUI(width, height);
-        setSlotElements(gui);
+        ingredients.insertIntoGUI(gui);
+        
         return gui;
     }
     
-    /**
+    private SimplePagedItemsGUI buildSimplePagedItemsGUI(IngredientList ingredients) {
-     * Sets the structure of the {@link GUI}.
+        SimplePagedItemsGUI gui = new SimplePagedItemsGUI(width, height, items, ingredients.findIndicesOfMarkerAsArray(Marker.ITEM_LIST_SLOT));
-     * The structure is a {@link String} of characters, like used in {@link ShapedRecipe} to
+        ingredients.insertIntoGUI(gui);
-     * define where which {@link Item} should be.
-     *
-     * @param structure The structure {@link String}
-     * @return The {@link GUIBuilder}
-     */
-    public GUIBuilder setStructure(@NotNull String structure) {
-        String cleanedStructure = structure.replace(" ", "").replace("\n", "");
-        if (cleanedStructure.length() != size)
-            throw new IllegalArgumentException("Structure length does not match size");
-        this.structure = cleanedStructure;
         
-        return this;
+        return gui;
     }
     
-    /**
+    private SimplePagedGUIsGUI buildSimplePagedGUIsGUI(IngredientList ingredients) {
-     * Sets an ingredient for the structure String, which will later be
+        SimplePagedGUIsGUI gui = new SimplePagedGUIsGUI(width, height, guis, ingredients.findIndicesOfMarkerAsArray(Marker.ITEM_LIST_SLOT));
-     * used to set up the inventory correctly.
+        ingredients.insertIntoGUI(gui);
-     *
+    
-     * @param key  The ingredient key
+        return gui;
-     * @param item The {@link Item}
-     * @return The {@link GUIBuilder}
-     */
-    public GUIBuilder setIngredient(char key, @NotNull Item item) {
-        ingredientMap.put(key, new Ingredient(item));
-        return this;
     }
     
-    /**
+    private SimpleTabGUI buildSimpleTabGUI(IngredientList ingredients) {
-     * Sets an ingredient for the structure String, which will later be
+        SimpleTabGUI gui = new SimpleTabGUI(width, height, guis, ingredients.findIndicesOfMarkerAsArray(Marker.ITEM_LIST_SLOT));
-     * used to set up the inventory correctly.
+        ingredients.insertIntoGUI(gui);
-     *
+        
-     * @param key         The ingredient key
+        return gui;
-     * @param slotElement The {@link SlotElement}
-     * @return The {@link GUIBuilder}
-     */
-    public GUIBuilder setIngredient(char key, @NotNull SlotElement slotElement) {
-        ingredientMap.put(key, new Ingredient(slotElement));
-        return this;
     }
     
-    protected void setIngredient(char key, int special) {
+    private SimpleScrollGUI buildSimpleScrollGUI(IngredientList ingredients) {
-        ingredientMap.put(key, new Ingredient(special));
+        SimpleScrollGUI gui = new SimpleScrollGUI(width, height, items, ingredients.findIndicesOfMarkerAsArray(Marker.ITEM_LIST_SLOT));
-    }
+        ingredients.insertIntoGUI(gui);
-    
-    private Ingredient[] parseStructure() {
-        if (structure == null) throw new IllegalStateException("Structure has not been set yet.");
-        
-        Ingredient[] ingredients = new Ingredient[size];
-        int i = 0;
-        for (char c : structure.toCharArray()) {
-            if (c != '.') ingredients[i] = this.ingredientMap.get(c);
-            i++;
-        }
-        
-        return ingredients;
-    }
-    
-    protected void setSlotElements(GUI gui) {
-        Ingredient[] ingredients = parseStructure();
-        for (int i = 0; i < gui.getSize(); i++) {
-            Ingredient ingredient = ingredients[i];
-            if (ingredient != null && ingredient.isSlotElement())
-                gui.setSlotElement(i, ingredient.getSlotElement());
-        }
-    }
-    
-    protected int[] findIndicesOf(int special) {
-        List<Integer> indices = new ArrayList<>();
-        
-        Ingredient[] ingredients = parseStructure();
-        for (int i = 0; i < size; i++) {
-            Ingredient ingredient = ingredients[i];
-            if (ingredient != null && ingredient.isSpecial() && ingredient.getSpecial() == special)
-                indices.add(i);
-        }
-        
-        return indices.stream().mapToInt(Integer::intValue).toArray();
-    }
-    
-    static class Ingredient {
-        
-        private final SlotElement slotElement;
-        private final int special;
-        
-        public Ingredient(Item item) {
-            this.slotElement = new SlotElement.ItemSlotElement(item);
-            this.special = -1;
-        }
-        
-        public Ingredient(SlotElement slotElement) {
-            this.slotElement = slotElement;
-            this.special = -1;
-        }
-        
-        public Ingredient(int special) {
-            this.special = special;
-            this.slotElement = null;
-        }
-        
-        public SlotElement getSlotElement() {
-            if (isSpecial()) throw new IllegalStateException("Ingredient is special");
-            return slotElement;
-        }
-        
-        public int getSpecial() {
-            if (isSlotElement()) throw new IllegalStateException("Ingredient is item");
-            return special;
-        }
-        
-        public boolean isSlotElement() {
-            return slotElement != null;
-        }
-        
-        public boolean isSpecial() {
-            return slotElement == null;
-        }
         
+        return gui;
     }
     
 }

src/main/java/de/studiocode/invui/gui/builder/GUIType.java

@@ -0,0 +1,11 @@
+package de.studiocode.invui.gui.builder;
+
+public enum GUIType {
+    
+    NORMAL,
+    PAGED_ITEMS,
+    PAGED_GUIs,
+    TAB,
+    SCROLL
+    
+}

src/main/java/de/studiocode/invui/gui/builder/Ingredient.java

@@ -0,0 +1,57 @@
+package de.studiocode.invui.gui.builder;
+
+import de.studiocode.invui.gui.GUI;
+import de.studiocode.invui.gui.SlotElement;
+import de.studiocode.invui.item.itembuilder.ItemBuilder;
+
+import java.util.function.Function;
+
+class Ingredient {
+    
+    private final SlotElement slotElement;
+    private final Marker marker;
+    private final Function<GUI, ItemBuilder> builderFunction;
+    
+    public Ingredient(SlotElement slotElement) {
+        this.slotElement = slotElement;
+        this.builderFunction = null;
+        this.marker = null;
+    }
+    
+    public Ingredient(Marker marker) {
+        this.marker = marker;
+        this.slotElement = null;
+        this.builderFunction = null;
+    }
+    
+    public Ingredient(Function<GUI, ItemBuilder> builderFunction) {
+        this.builderFunction = builderFunction;
+        this.slotElement = null;
+        this.marker = null;
+    }
+    
+    public SlotElement getSlotElement() {
+        return slotElement;
+    }
+    
+    public Marker getMarker() {
+        return marker;
+    }
+    
+    public Function<GUI, ItemBuilder> getBuilderFunction() {
+        return builderFunction;
+    }
+    
+    public boolean isSlotElement() {
+        return slotElement != null;
+    }
+    
+    public boolean isMarker() {
+        return marker != null;
+    }
+    
+    public boolean isBuilderFunction() {
+        return builderFunction != null;
+    }
+    
+}

src/main/java/de/studiocode/invui/gui/builder/IngredientList.java

@@ -0,0 +1,58 @@
+package de.studiocode.invui.gui.builder;
+
+import de.studiocode.invui.gui.Controllable;
+import de.studiocode.invui.gui.GUI;
+import de.studiocode.invui.gui.SlotElement;
+import de.studiocode.invui.gui.SlotElement.ItemSlotElement;
+import de.studiocode.invui.item.Item;
+import de.studiocode.invui.item.impl.controlitem.ControlItem;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+
+class IngredientList extends ArrayList<Ingredient> {
+    
+    public IngredientList(String structure, HashMap<Character, Ingredient> ingredientMap) {
+        for (char c : structure.toCharArray()) {
+            Ingredient ingredient = null;
+            if (ingredientMap.containsKey(c)) ingredient = ingredientMap.get(c);
+            add(ingredient);
+        }
+    }
+    
+    public void insertIntoGUI(GUI gui) {
+        for (int i = 0; i < size(); i++) {
+            Ingredient ingredient = get(i);
+            if (ingredient != null && ingredient.isSlotElement()) {
+                SlotElement slotElement = ingredient.getSlotElement();
+                
+                if (gui instanceof Controllable && slotElement instanceof ItemSlotElement) {
+                    Item item = ((ItemSlotElement) slotElement).getItem();
+                    if (item instanceof ControlItem) {
+                        ((Controllable) gui).addControlItem(i, (ControlItem<?>) item);
+                        continue;
+                    }
+                }
+                
+                gui.setSlotElement(i, ingredient.getSlotElement());
+            }
+        }
+    }
+    
+    public List<Integer> findIndicesOfMarker(Marker marker) {
+        List<Integer> indices = new ArrayList<>();
+        for (int i = 0; i < size(); i++) {
+            Ingredient ingredient = get(i);
+            if (ingredient != null && ingredient.isMarker() && ingredient.getMarker() == marker)
+                indices.add(i);
+        }
+        
+        return indices;
+    }
+    
+    public int[] findIndicesOfMarkerAsArray(Marker marker) {
+        return findIndicesOfMarker(marker).stream().mapToInt(Integer::intValue).toArray();
+    }
+    
+}

src/main/java/de/studiocode/invui/gui/builder/Marker.java

@@ -0,0 +1,7 @@
+package de.studiocode.invui.gui.builder;
+
+public enum Marker {
+    
+    ITEM_LIST_SLOT
+    
+}

src/main/java/de/studiocode/invui/gui/builder/PagedGUIBuilder.java

@@ -1,119 +0,0 @@
-package de.studiocode.invui.gui.builder;
-
-import de.studiocode.invui.gui.GUI;
-import de.studiocode.invui.gui.SlotElement;
-import de.studiocode.invui.gui.impl.PagedGUI;
-import de.studiocode.invui.gui.impl.SimplePagedGUIsGUI;
-import de.studiocode.invui.gui.impl.SimplePagedItemsGUI;
-import de.studiocode.invui.item.Item;
-import de.studiocode.invui.item.itembuilder.ItemBuilder;
-import org.jetbrains.annotations.NotNull;
-
-import java.util.List;
-import java.util.function.Function;
-
-public class PagedGUIBuilder extends GUIBuilder {
-    
-    private final ContentType contentType;
-    
-    private Function<PagedGUI, ItemBuilder> backFunction;
-    private Function<PagedGUI, ItemBuilder> forwardFunction;
-    private int[] listSlots;
-    private List<?> content;
-    
-    public PagedGUIBuilder(ContentType contentType, int width, int height) {
-        super(width, height);
-        this.contentType = contentType;
-    }
-    
-    @SuppressWarnings("unchecked")
-    @Override
-    public PagedGUI build() {
-        int[] listSlots = this.listSlots != null ? this.listSlots : findIndicesOf(2);
-        int[] backSlots = findIndicesOf(0);
-        int[] forwardSlots = findIndicesOf(1);
-        
-        if (listSlots.length == 0) throw new IllegalStateException("No list slots have been set.");
-        if (backSlots.length == 0) throw new IllegalStateException("Not back slot has been set.");
-        if (forwardSlots.length == 0) throw new IllegalStateException("No forward slot has been set.");
-        if (content == null) throw new IllegalStateException("Content has not been set.");
-        if (forwardFunction == null) throw new IllegalStateException("Forward function has not been set.");
-        if (backFunction == null) throw new IllegalStateException("Back function has not been set");
-        
-        int backSlot = backSlots[0];
-        int forwardSlot = forwardSlots[0];
-        
-        PagedGUI gui;
-        if (contentType == ContentType.GUI) {
-            gui = new SimplePagedGUIsGUI(width, height, backSlot, backFunction,
-                forwardSlot, forwardFunction, (List<GUI>) content, listSlots);
-        } else {
-            gui = new SimplePagedItemsGUI(width, height, backSlot, backFunction,
-                forwardSlot, forwardFunction, (List<Item>) content, listSlots);
-        }
-        
-        setSlotElements(gui);
-        return gui;
-    }
-    
-    public PagedGUIBuilder setGUIs(List<GUI> guis) {
-        if (contentType != ContentType.GUI)
-            throw new IllegalStateException("Can't set guis if ContentType is not GUI");
-        content = guis;
-        
-        return this;
-    }
-    
-    public PagedGUIBuilder setItems(List<Item> items) {
-        if (contentType != ContentType.SINGLE_ITEMS)
-            throw new IllegalStateException("Can't set items if ContentType is not SINGLE_ITEMS");
-        content = items;
-        
-        return this;
-    }
-    
-    public PagedGUIBuilder setListSlots(int[] listSlots) {
-        this.listSlots = listSlots;
-        return this;
-    }
-    
-    public PagedGUIBuilder setListSlotIngredient(char key) {
-        setIngredient(key, 2);
-        return this;
-    }
-    
-    public PagedGUIBuilder setBackItem(char key, Function<PagedGUI, ItemBuilder> backFunction) {
-        setIngredient(key, 0);
-        this.backFunction = backFunction;
-        return this;
-    }
-    
-    public PagedGUIBuilder setForwardItem(char key, Function<PagedGUI, ItemBuilder> forwardFunction) {
-        setIngredient(key, 1);
-        this.forwardFunction = forwardFunction;
-        return this;
-    }
-    
-    @Override
-    public PagedGUIBuilder setStructure(@NotNull String structure) {
-        return (PagedGUIBuilder) super.setStructure(structure);
-    }
-    
-    @Override
-    public PagedGUIBuilder setIngredient(char key, @NotNull Item item) {
-        return (PagedGUIBuilder) super.setIngredient(key, item);
-    }
-    
-    @Override
-    public PagedGUIBuilder setIngredient(char key, @NotNull SlotElement slotElement) {
-        return (PagedGUIBuilder) super.setIngredient(key, slotElement);
-    }
-    
-    public enum ContentType {
-        
-        SINGLE_ITEMS,
-        GUI
-        
-    }
-    
-}

src/main/java/de/studiocode/invui/gui/builder/TabGUIBuilder.java

@@ -1,80 +0,0 @@
-package de.studiocode.invui.gui.builder;
-
-import de.studiocode.invui.gui.GUI;
-import de.studiocode.invui.gui.SlotElement;
-import de.studiocode.invui.gui.impl.SimpleTabGUI;
-import de.studiocode.invui.gui.impl.TabGUI;
-import de.studiocode.invui.item.Item;
-import de.studiocode.invui.item.itembuilder.ItemBuilder;
-import org.jetbrains.annotations.NotNull;
-
-import java.util.LinkedHashMap;
-import java.util.function.Function;
-
-public class TabGUIBuilder extends GUIBuilder {
-    
-    private final LinkedHashMap<GUI, Function<TabGUI, ItemBuilder>> tabs = new LinkedHashMap<>();
-    
-    private int[] listSlots;
-    private int[] tabItemSlots;
-    
-    public TabGUIBuilder(int width, int height) {
-        super(width, height);
-    }
-    
-    @Override
-    public TabGUI build() {
-        int[] listSlots = this.listSlots != null ? this.listSlots : findIndicesOf(0);
-        int[] tabItemSlots = this.tabItemSlots != null ? this.tabItemSlots : findIndicesOf(1);
-        
-        if (listSlots.length == 0) throw new IllegalStateException("No list slots have been set.");
-        if (tabItemSlots.length != tabs.size())
-            throw new IllegalStateException("TabItemSlots length has to be the same as tabs size");
-        
-        SimpleTabGUI tabGUI = new SimpleTabGUI(width, height, tabs, listSlots, tabItemSlots);
-        setSlotElements(tabGUI);
-        
-        return tabGUI;
-    }
-    
-    public TabGUIBuilder addTab(GUI gui, Function<TabGUI, ItemBuilder> builderFunction) {
-        tabs.put(gui, builderFunction);
-        return this;
-    }
-    
-    public TabGUIBuilder setListSlotIngredient(char key) {
-        setIngredient(key, 0);
-        return this;
-    }
-    
-    public TabGUIBuilder setTabSlotIngredient(char key) {
-        setIngredient(key, 1);
-        return this;
-    }
-    
-    public TabGUIBuilder setListSlots(int[] listSlots) {
-        this.listSlots = listSlots;
-        return this;
-    }
-    
-    public TabGUIBuilder setTabItemSlots(int[] tabItemSlots) {
-        this.tabItemSlots = tabItemSlots;
-        return this;
-    }
-    
-    @Override
-    public TabGUIBuilder setStructure(@NotNull String structure) {
-        return (TabGUIBuilder) super.setStructure(structure);
-    }
-    
-    @Override
-    public TabGUIBuilder setIngredient(char key, @NotNull Item item) {
-        return (TabGUIBuilder) super.setIngredient(key, item);
-    }
-    
-    @Override
-    public TabGUIBuilder setIngredient(char key, @NotNull SlotElement slotElement) {
-        return (TabGUIBuilder) super.setIngredient(key, slotElement);
-    }
-    
-}

src/main/java/de/studiocode/invui/gui/impl/PagedGUI.java

@@ -1,28 +1,29 @@
 package de.studiocode.invui.gui.impl;
 
+import de.studiocode.invui.gui.Controllable;
 import de.studiocode.invui.gui.GUI;
 import de.studiocode.invui.gui.SlotElement;
-import de.studiocode.invui.gui.builder.PagedGUIBuilder;
+import de.studiocode.invui.gui.builder.GUIBuilder;
 import de.studiocode.invui.item.Item;
-import de.studiocode.invui.item.impl.pagedgui.BackItem;
+import de.studiocode.invui.item.impl.controlitem.ControlItem;
-import de.studiocode.invui.item.impl.pagedgui.ForwardItem;
+import de.studiocode.invui.item.impl.controlitem.PageItem;
 
+import java.util.ArrayList;
 import java.util.List;
 
 /**
  * A {@link GUI} with pages.
  *
- * @see PagedGUIBuilder
+ * @see GUIBuilder
  * @see SimplePagedItemsGUI
  * @see SimplePagedGUIsGUI
  */
-public abstract class PagedGUI extends BaseGUI {
+public abstract class PagedGUI extends BaseGUI implements Controllable {
     
+    private final List<Item> controlItems = new ArrayList<>();
     private final boolean infinitePages;
     private final int[] itemListSlots;
     protected int currentPage;
-    private Item forwardItem;
-    private Item backItem;
     
     public PagedGUI(int width, int height, boolean infinitePages, int... itemListSlots) {
         super(width, height);
@@ -30,9 +31,14 @@ public abstract class PagedGUI extends BaseGUI {
         this.itemListSlots = itemListSlots;
     }
     
-    public void setControlItems(int backItemSlot, BackItem backItem, int forwardItemSlot, ForwardItem forwardItem) {
+    @Override
-        setItem(backItemSlot, this.backItem = backItem);
+    public void addControlItem(int index, ControlItem<?> controlItem) {
-        setItem(forwardItemSlot, this.forwardItem = forwardItem);
+        if (!(controlItem instanceof PageItem))
+            throw new IllegalArgumentException("controlItem is not an instance of PageItem");
+        
+        ((PageItem) controlItem).setGui(this);
+        setItem(index, controlItem);
+        controlItems.add(controlItem);
     }
     
     public void goForward() {
@@ -72,8 +78,7 @@ public abstract class PagedGUI extends BaseGUI {
     }
     
     private void updateControlItems() {
-        backItem.notifyWindows();
+        controlItems.forEach(Item::notifyWindows);
-        forwardItem.notifyWindows();
     }
     
     private void updatePageContent() {
@@ -89,14 +94,6 @@ public abstract class PagedGUI extends BaseGUI {
         return currentPage;
     }
     
-    public Item getForwardItem() {
-        return forwardItem;
-    }
-    
-    public Item getBackItem() {
-        return backItem;
-    }
-    
     public boolean hasInfinitePages() {
         return infinitePages;
     }

src/main/java/de/studiocode/invui/gui/impl/ScrollGUI.java

@@ -1,8 +1,12 @@
 package de.studiocode.invui.gui.impl;
 
+import de.studiocode.invui.gui.Controllable;
 import de.studiocode.invui.gui.GUI;
 import de.studiocode.invui.gui.SlotElement;
 import de.studiocode.invui.item.Item;
+import de.studiocode.invui.item.impl.controlitem.ControlItem;
+import de.studiocode.invui.item.impl.controlitem.ScrollItem;
+import de.studiocode.invui.util.SlotUtils;
 
 import java.util.ArrayList;
 import java.util.List;
@@ -12,7 +16,7 @@ import java.util.List;
  *
  * @see SimpleScrollGUI
  */
-public abstract class ScrollGUI extends BaseGUI {
+public abstract class ScrollGUI extends BaseGUI implements Controllable {
     
     private final List<Item> controlItems = new ArrayList<>();
     private final boolean infiniteLines;
@@ -21,12 +25,11 @@ public abstract class ScrollGUI extends BaseGUI {
     
     protected int offset;
     
-    
+    public ScrollGUI(int width, int height, boolean infiniteLines, int... itemListSlots) {
-    public ScrollGUI(int width, int height, boolean infiniteLines, int lineLength, int... itemListSlots) {
         super(width, height);
         this.infiniteLines = infiniteLines;
         this.itemListSlots = itemListSlots;
-        this.lineLength = lineLength;
+        this.lineLength = SlotUtils.getLongestLineLength(itemListSlots, width);
         
         if (lineLength == 0)
             throw new IllegalArgumentException("Line length can't be 0");
@@ -36,9 +39,14 @@ public abstract class ScrollGUI extends BaseGUI {
             throw new IllegalArgumentException("itemListSlots has to be a multiple of lineLength");
     }
     
-    public void addControlItem(int index, Item item) {
+    @Override
-        controlItems.add(item);
+    public void addControlItem(int index, ControlItem<?> controlItem) {
-        setItem(index, item);
+        if (!(controlItem instanceof ScrollItem))
+            throw new IllegalArgumentException("controlItem is not an instance of ScrollItem");
+    
+        ((ScrollItem) controlItem).setGui(this);
+        setItem(index, controlItem);
+        controlItems.add(controlItem);
     }
     
     public void setCurrentLine(int line) {

src/main/java/de/studiocode/invui/gui/impl/SimplePagedGUIsGUI.java

@@ -2,36 +2,30 @@ package de.studiocode.invui.gui.impl;
 
 import de.studiocode.invui.gui.GUI;
 import de.studiocode.invui.gui.SlotElement;
-import de.studiocode.invui.gui.builder.PagedGUIBuilder;
+import de.studiocode.invui.gui.builder.GUIBuilder;
-import de.studiocode.invui.item.impl.pagedgui.BackItem;
-import de.studiocode.invui.item.impl.pagedgui.ForwardItem;
-import de.studiocode.invui.item.itembuilder.ItemBuilder;
 
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
-import java.util.function.Function;
 
 /**
  * A {@link PagedGUI} where every page is it's own {@link GUI}.
  *
- * @see PagedGUIBuilder
+ * @see GUIBuilder
  * @see SimplePagedItemsGUI
  */
 public class SimplePagedGUIsGUI extends PagedGUI {
     
     private List<GUI> guis;
     
-    public SimplePagedGUIsGUI(int width, int height,
+    public SimplePagedGUIsGUI(int width, int height, int... itemListSlots) {
-                              int backItemSlot, Function<PagedGUI, ItemBuilder> backFunction,
+        this(width, height, new ArrayList<>(), itemListSlots);
-                              int forwardItemSlot, Function<PagedGUI, ItemBuilder> forwardFunction,
+    }
-                              List<GUI> guis, int... itemListSlots) {
     
+    public SimplePagedGUIsGUI(int width, int height, List<GUI> guis, int... itemListSlots) {
         super(width, height, false, itemListSlots);
         this.guis = guis;
         
-        setControlItems(backItemSlot, new BackItem(this, backFunction),
-            forwardItemSlot, new ForwardItem(this, forwardFunction));
-        
         update();
     }
     

src/main/java/de/studiocode/invui/gui/impl/SimplePagedItemsGUI.java

@@ -2,36 +2,31 @@ package de.studiocode.invui.gui.impl;
 
 import de.studiocode.invui.gui.SlotElement;
 import de.studiocode.invui.gui.SlotElement.ItemSlotElement;
-import de.studiocode.invui.gui.builder.PagedGUIBuilder;
+import de.studiocode.invui.gui.builder.GUIBuilder;
 import de.studiocode.invui.item.Item;
-import de.studiocode.invui.item.impl.pagedgui.BackItem;
-import de.studiocode.invui.item.impl.pagedgui.ForwardItem;
-import de.studiocode.invui.item.itembuilder.ItemBuilder;
 
+import java.util.ArrayList;
 import java.util.List;
-import java.util.function.Function;
 import java.util.stream.Collectors;
 
 /**
  * A {@link PagedGUI} that is filled with {@link Item}s.
  *
- * @see PagedGUIBuilder
+ * @see GUIBuilder
  * @see SimplePagedGUIsGUI
  */
 public class SimplePagedItemsGUI extends PagedGUI {
     
     private List<Item> items;
     
-    public SimplePagedItemsGUI(int width, int height,
+    public SimplePagedItemsGUI(int width, int height, int... itemListSlots) {
-                               int backItemSlot, Function<PagedGUI, ItemBuilder> backFunction,
+        this(width, height, new ArrayList<>(), itemListSlots);
-                               int forwardItemSlot, Function<PagedGUI, ItemBuilder> forwardFunction,
+    }
-                               List<Item> items, int... itemListSlots) {
     
+    public SimplePagedItemsGUI(int width, int height, List<Item> items, int... itemListSlots) {
         super(width, height, false, itemListSlots);
         this.items = items;
         
-        setControlItems(backItemSlot, new BackItem(this, backFunction),
-            forwardItemSlot, new ForwardItem(this, forwardFunction));
         update();
     }
     
@@ -53,4 +48,5 @@ public class SimplePagedItemsGUI extends PagedGUI {
         this.items = items;
         update();
     }
+    
 }

src/main/java/de/studiocode/invui/gui/impl/SimpleScrollGUI.java

@@ -10,8 +10,8 @@ public class SimpleScrollGUI extends ScrollGUI {
     
     private List<Item> items;
     
-    public SimpleScrollGUI(int width, int height, List<Item> items, int lineLength, int... itemListSlots) {
+    public SimpleScrollGUI(int width, int height, List<Item> items, int... itemListSlots) {
-        super(width, height, false, lineLength, itemListSlots);
+        super(width, height, false, itemListSlots);
         this.items = items;
         
         update();

src/main/java/de/studiocode/invui/gui/impl/SimpleTabGUI.java

@@ -2,36 +2,23 @@ package de.studiocode.invui.gui.impl;
 
 import de.studiocode.invui.gui.GUI;
 import de.studiocode.invui.gui.SlotElement;
-import de.studiocode.invui.gui.builder.TabGUIBuilder;
+import de.studiocode.invui.gui.builder.GUIBuilder;
-import de.studiocode.invui.item.impl.tabgui.TabItem;
-import de.studiocode.invui.item.itembuilder.ItemBuilder;
 
-import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.LinkedHashMap;
 import java.util.List;
-import java.util.function.Function;
 
 /**
  * A {@link GUI} that has multiple tabs with which users can switch between {@link GUI}s.
  *
- * @see TabGUIBuilder
+ * @see GUIBuilder
  */
 public class SimpleTabGUI extends TabGUI {
     
     private final List<GUI> tabs;
     
-    public SimpleTabGUI(int width, int height, LinkedHashMap<GUI, Function<TabGUI, ItemBuilder>> tabs,
+    public SimpleTabGUI(int width, int height, List<GUI> tabs, int[] listSlots) {
-                        int[] listSlots, int[] tabItemSlots) {
-        
         super(width, height, tabs.size(), listSlots);
-        this.tabs = new ArrayList<>(tabs.keySet());
+        this.tabs = tabs;
-        
-        List<Function<TabGUI, ItemBuilder>> builderFunctions = new ArrayList<>(tabs.values());
-        for (int i = 0; i < tabs.size(); i++) {
-            TabItem tabItem = new TabItem(this, i, builderFunctions.get(i));
-            setTabItem(i, tabItemSlots[i], tabItem);
-        }
         
         update();
     }

src/main/java/de/studiocode/invui/gui/impl/TabGUI.java

@@ -1,17 +1,19 @@
 package de.studiocode.invui.gui.impl;
 
+import de.studiocode.invui.gui.Controllable;
 import de.studiocode.invui.gui.SlotElement;
 import de.studiocode.invui.item.Item;
-import de.studiocode.invui.item.impl.tabgui.TabItem;
+import de.studiocode.invui.item.impl.controlitem.ControlItem;
+import de.studiocode.invui.item.impl.controlitem.TabItem;
 
-import java.util.Arrays;
+import java.util.ArrayList;
 import java.util.List;
 
-public abstract class TabGUI extends BaseGUI {
+public abstract class TabGUI extends BaseGUI implements Controllable {
     
+    private final List<Item> controlItems = new ArrayList<>();
     private final int tabAmount;
     private final int[] listSlots;
-    private final Item[] tabItems;
     
     private int currentTab;
     
@@ -19,7 +21,6 @@ public abstract class TabGUI extends BaseGUI {
         super(width, height);
         this.tabAmount = tabAmount;
         this.listSlots = listSlots;
-        this.tabItems = new Item[tabAmount];
     }
     
     public void showTab(int tab) {
@@ -30,14 +31,26 @@ public abstract class TabGUI extends BaseGUI {
         update();
     }
     
-    public void setTabItem(int tab, int index, TabItem tabItem) {
+    @Override
-        tabItems[tab] = tabItem;
+    public void addControlItem(int index, ControlItem<?> controlItem) {
-        setItem(index, tabItem);
+        if (!(controlItem instanceof TabItem))
+            throw new IllegalArgumentException("controlItem is not an instance of TabItem");
+        
+        ((TabItem) controlItem).setGui(this);
+        setItem(index, controlItem);
+        controlItems.add(controlItem);
     }
     
     protected void update() {
-        Arrays.stream(tabItems).forEach(Item::notifyWindows);
+        updateControlItems();
+        updateContent();
+    }
     
+    private void updateControlItems() {
+        controlItems.forEach(Item::notifyWindows);
+    }
+    
+    private void updateContent() {
         List<SlotElement> slotElements = getSlotElements(currentTab);
         for (int i = 0; i < listSlots.length; i++) {
             int slot = listSlots[i];

src/main/java/de/studiocode/invui/item/impl/FunctionItem.java

@@ -1,34 +0,0 @@
-package de.studiocode.invui.item.impl;
-
-import de.studiocode.invui.item.itembuilder.ItemBuilder;
-import org.bukkit.entity.Player;
-import org.bukkit.event.inventory.ClickType;
-import org.bukkit.event.inventory.InventoryClickEvent;
-
-import java.util.function.Function;
-
-public class FunctionItem<T> extends BaseItem {
-    
-    private final T t;
-    private final Function<T, ItemBuilder> builderFunction;
-    
-    public FunctionItem(T t, Function<T, ItemBuilder> builderFunction) {
-        this.t = t;
-        this.builderFunction = builderFunction;
-    }
-    
-    @Override
-    public ItemBuilder getItemBuilder() {
-        return builderFunction.apply(t);
-    }
-    
-    public T getT() {
-        return t;
-    }
-    
-    @Override
-    public void handleClick(ClickType clickType, Player player, InventoryClickEvent event) {
-        // empty
-    }
-    
-}

src/main/java/de/studiocode/invui/item/impl/controlitem/ControlItem.java

@@ -0,0 +1,31 @@
+package de.studiocode.invui.item.impl.controlitem;
+
+import de.studiocode.invui.gui.GUI;
+import de.studiocode.invui.item.impl.BaseItem;
+import de.studiocode.invui.item.itembuilder.ItemBuilder;
+
+import java.util.function.Function;
+
+public abstract class ControlItem<G extends GUI> extends BaseItem {
+    
+    private G gui;
+    private final Function<G, ItemBuilder> builderFunction;
+    
+    public ControlItem(Function<G, ItemBuilder> builderFunction) {
+        this.builderFunction = builderFunction;
+    }
+    
+    @Override
+    public ItemBuilder getItemBuilder() {
+        return builderFunction.apply(gui);
+    }
+    
+    public G getGui() {
+        return gui;
+    }
+    
+    public void setGui(G gui) {
+        this.gui = gui;
+    }
+    
+}

src/main/java/de/studiocode/invui/item/impl/controlitem/PageItem.java

@@ -0,0 +1,31 @@
+package de.studiocode.invui.item.impl.controlitem;
+
+import de.studiocode.invui.gui.impl.PagedGUI;
+import de.studiocode.invui.item.itembuilder.ItemBuilder;
+import org.bukkit.entity.Player;
+import org.bukkit.event.inventory.ClickType;
+import org.bukkit.event.inventory.InventoryClickEvent;
+
+import java.util.function.Function;
+
+/**
+ * Switches between pages in a {@link PagedGUI}
+ */
+public class PageItem extends ControlItem<PagedGUI> {
+    
+    private final boolean forward;
+    
+    public PageItem(boolean forward, Function<PagedGUI, ItemBuilder> builderFunction) {
+        super(builderFunction);
+        this.forward = forward;
+    }
+    
+    @Override
+    public void handleClick(ClickType clickType, Player player, InventoryClickEvent event) {
+        if (clickType == ClickType.LEFT) {
+            if (forward) getGui().goForward();
+            else getGui().goBack();
+        } 
+    }
+    
+}

src/main/java/de/studiocode/invui/item/impl/controlitem/ScrollItem.java

@@ -1,7 +1,6 @@
-package de.studiocode.invui.item.impl.scrollgui;
+package de.studiocode.invui.item.impl.controlitem;
 
 import de.studiocode.invui.gui.impl.ScrollGUI;
-import de.studiocode.invui.item.impl.FunctionItem;
 import de.studiocode.invui.item.itembuilder.ItemBuilder;
 import org.bukkit.entity.Player;
 import org.bukkit.event.inventory.ClickType;
@@ -10,25 +9,27 @@ import org.bukkit.event.inventory.InventoryClickEvent;
 import java.util.HashMap;
 import java.util.function.Function;
 
-public class ScrollItem extends FunctionItem<ScrollGUI> {
+/**
+ * Scrolls in a {@link ScrollGUI}
+ */
+public class ScrollItem extends ControlItem<ScrollGUI> {
     
     private final HashMap<ClickType, Integer> scroll;
     
-    public ScrollItem(ScrollGUI scrollGUI, int scrollLeftClick, Function<ScrollGUI, ItemBuilder> builderFunction) {
+    public ScrollItem(int scrollLeftClick, Function<ScrollGUI, ItemBuilder> builderFunction) {
-        super(scrollGUI, builderFunction);
+        super(builderFunction);
-        
         scroll = new HashMap<>();
         scroll.put(ClickType.LEFT, scrollLeftClick);
     }
     
-    public ScrollItem(ScrollGUI scrollGUI, HashMap<ClickType, Integer> scroll, Function<ScrollGUI, ItemBuilder> builderFunction) {
+    public ScrollItem(HashMap<ClickType, Integer> scroll, Function<ScrollGUI, ItemBuilder> builderFunction) {
-        super(scrollGUI, builderFunction);
+        super(builderFunction);
         this.scroll = scroll;
     }
     
     @Override
     public void handleClick(ClickType clickType, Player player, InventoryClickEvent event) {
-        if (scroll.containsKey(clickType)) getT().scroll(scroll.get(clickType));
+        if (scroll.containsKey(clickType)) getGui().scroll(scroll.get(clickType));
     }
     
 }

src/main/java/de/studiocode/invui/item/impl/controlitem/TabItem.java

@@ -1,7 +1,6 @@
-package de.studiocode.invui.item.impl.tabgui;
+package de.studiocode.invui.item.impl.controlitem;
 
 import de.studiocode.invui.gui.impl.TabGUI;
-import de.studiocode.invui.item.impl.FunctionItem;
 import de.studiocode.invui.item.itembuilder.ItemBuilder;
 import org.bukkit.entity.Player;
 import org.bukkit.event.inventory.ClickType;
@@ -9,18 +8,21 @@ import org.bukkit.event.inventory.InventoryClickEvent;
 
 import java.util.function.Function;
 
-public class TabItem extends FunctionItem<TabGUI> {
+/**
+ * Switches between tabs in a {@link TabGUI}
+ */
+public class TabItem extends ControlItem<TabGUI> {
     
     private final int tab;
     
-    public TabItem(TabGUI tabGUI, int tab, Function<TabGUI, ItemBuilder> builderFunction) {
+    public TabItem(int tab, Function<TabGUI, ItemBuilder> builderFunction) {
-        super(tabGUI, builderFunction);
+        super(builderFunction);
         this.tab = tab;
     }
     
     @Override
     public void handleClick(ClickType clickType, Player player, InventoryClickEvent event) {
-        if (clickType == ClickType.LEFT) getT().showTab(tab);
+        if (clickType == ClickType.LEFT) getGui().showTab(tab);
     }
     
 }

src/main/java/de/studiocode/invui/item/impl/pagedgui/BackItem.java

@@ -1,23 +0,0 @@
-package de.studiocode.invui.item.impl.pagedgui;
-
-import de.studiocode.invui.gui.impl.PagedGUI;
-import de.studiocode.invui.item.impl.FunctionItem;
-import de.studiocode.invui.item.itembuilder.ItemBuilder;
-import org.bukkit.entity.Player;
-import org.bukkit.event.inventory.ClickType;
-import org.bukkit.event.inventory.InventoryClickEvent;
-
-import java.util.function.Function;
-
-public class BackItem extends FunctionItem<PagedGUI> {
-    
-    public BackItem(PagedGUI pagedGUI, Function<PagedGUI, ItemBuilder> builderFunction) {
-        super(pagedGUI, builderFunction);
-    }
-    
-    @Override
-    public void handleClick(ClickType clickType, Player player, InventoryClickEvent event) {
-        if (clickType == ClickType.LEFT) getT().goBack();
-    }
-    
-}

src/main/java/de/studiocode/invui/item/impl/pagedgui/ForwardItem.java

@@ -1,23 +0,0 @@
-package de.studiocode.invui.item.impl.pagedgui;
-
-import de.studiocode.invui.gui.impl.PagedGUI;
-import de.studiocode.invui.item.impl.FunctionItem;
-import de.studiocode.invui.item.itembuilder.ItemBuilder;
-import org.bukkit.entity.Player;
-import org.bukkit.event.inventory.ClickType;
-import org.bukkit.event.inventory.InventoryClickEvent;
-
-import java.util.function.Function;
-
-public class ForwardItem extends FunctionItem<PagedGUI> {
-    
-    public ForwardItem(PagedGUI pagedGUI, Function<PagedGUI, ItemBuilder> builderFunction) {
-        super(pagedGUI, builderFunction);
-    }
-    
-    @Override
-    public void handleClick(ClickType clickType, Player player, InventoryClickEvent event) {
-        if (clickType == ClickType.LEFT) getT().goForward();
-    }
-    
-}

src/main/java/de/studiocode/invui/util/SlotUtils.java

@@ -1,7 +1,9 @@
 package de.studiocode.invui.util;
 
+import java.util.Arrays;
 import java.util.LinkedHashSet;
 import java.util.Set;
+import java.util.stream.Collectors;
 
 public class SlotUtils {
     
@@ -75,6 +77,30 @@ public class SlotUtils {
         else return slot + 9;
     }
     
+    public static int getLongestLineLength(int[] slots, int frameWidth) {
+        int longestLength = 0;
+        int currentLength = 1;
+        Point2D previous = null;
+        
+        for (Point2D point : Arrays.stream(slots)
+            .mapToObj(index -> convertFromIndex(index, frameWidth))
+            .collect(Collectors.toList())) {
+            if (previous != null) {
+                if (isNeighbor(previous, point)) currentLength++;
+                else currentLength = 1;
+            }
+            
+            previous = point;
+            longestLength = Math.max(longestLength, currentLength);
+        }
+        
+        return longestLength;
+    }
+    
+    public static boolean isNeighbor(Point2D point1, Point2D point2) {
+        return Math.abs(point1.getX() - point2.getX()) + Math.abs(point1.getY() - point2.getY()) == 1;
+    }
+    
     public enum Order {
         
         HORIZONTAL,