diff --git a/dependencies.gradle b/dependencies.gradle
index 81c78616..7163bb84 100644
--- a/dependencies.gradle
+++ b/dependencies.gradle
@@ -30,6 +30,7 @@
  */
 dependencies {
     api("org.jetbrains:annotations:24.0.1")
+    api("com.github.GTNewHorizons:GTNHLib:0.2.4:dev")
 
     compileOnly("com.github.GTNewHorizons:NotEnoughItems:2.5.4-GTNH:dev")
     compileOnly("com.github.GTNewHorizons:Hodgepodge:2.4.8:dev") { transitive = false }
diff --git a/gradle.properties b/gradle.properties
index 8c0c9bd7..e1e430e6 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -33,7 +33,7 @@ channel = stable
 mappingsVersion = 12
 
 # Defines other MCP mappings for dependency deobfuscation.
-remoteMappings = https://raw.githubusercontent.com/MinecraftForge/FML/1.7.10/conf/
+remoteMappings = https\://raw.githubusercontent.com/MinecraftForge/FML/1.7.10/conf/
 
 # Select a default username for testing your mod. You can always override this per-run by running
 # `./gradlew runClient --username=AnotherPlayer`, or configuring this command in your IDE.
@@ -117,7 +117,7 @@ includeWellKnownRepositories = true
 usesMavenPublishing = true
 
 # Maven repository to publish the mod to.
-# mavenPublishUrl = https://nexus.gtnewhorizons.com/repository/releases/
+# mavenPublishUrl = https\://nexus.gtnewhorizons.com/repository/releases/
 
 # Publishing to Modrinth requires you to set the MODRINTH_TOKEN environment variable to your current Modrinth API token.
 #
diff --git a/settings.gradle b/settings.gradle
index 3b6c62d0..16a5b4ca 100644
--- a/settings.gradle
+++ b/settings.gradle
@@ -17,7 +17,7 @@ pluginManagement {
 }
 
 plugins {
-    id 'com.gtnewhorizons.gtnhsettingsconvention' version '1.0.9'
+    id 'com.gtnewhorizons.gtnhsettingsconvention' version '1.0.14'
 }
 
 
diff --git a/src/main/java/com/cleanroommc/modularui/GuiErrorHandler.java b/src/main/java/com/cleanroommc/modularui/GuiErrorHandler.java
index 74cbf9b8..c6e46e75 100644
--- a/src/main/java/com/cleanroommc/modularui/GuiErrorHandler.java
+++ b/src/main/java/com/cleanroommc/modularui/GuiErrorHandler.java
@@ -3,9 +3,9 @@
 import com.cleanroommc.modularui.api.widget.IGuiElement;
 import cpw.mods.fml.relauncher.Side;
 import cpw.mods.fml.relauncher.SideOnly;
+import it.unimi.dsi.fastutil.objects.ObjectOpenHashSet;
 
 import java.util.ArrayList;
-import java.util.HashSet;
 import java.util.List;
 import java.util.Set;
 
@@ -14,7 +14,7 @@ public class GuiErrorHandler {
 
     public static final GuiErrorHandler INSTANCE = new GuiErrorHandler();
 
-    private final Set<GuiError> errorSet = new HashSet<>();
+    private final Set<GuiError> errorSet = new ObjectOpenHashSet<>();
     private final List<GuiError> errors = new ArrayList<>();
 
     private GuiErrorHandler() {
diff --git a/src/main/java/com/cleanroommc/modularui/ModularUI.java b/src/main/java/com/cleanroommc/modularui/ModularUI.java
index da295b5f..fbd624d2 100644
--- a/src/main/java/com/cleanroommc/modularui/ModularUI.java
+++ b/src/main/java/com/cleanroommc/modularui/ModularUI.java
@@ -15,6 +15,7 @@
 public class ModularUI {
 
     static final String DEPENDENCIES = "required-after:gtnhmixins@[2.0.1,); "
+        + "required-after:gtnhlib@[0.2.0,);"
         + "after:NotEnoughItems@[2.3.27-GTNH,);"
         + "after:hodgepodge@[2.0.0,);"
         + "before:gregtech";
diff --git a/src/main/java/com/cleanroommc/modularui/config/Config.java b/src/main/java/com/cleanroommc/modularui/config/Config.java
index 4404ff52..270c3ca6 100644
--- a/src/main/java/com/cleanroommc/modularui/config/Config.java
+++ b/src/main/java/com/cleanroommc/modularui/config/Config.java
@@ -7,13 +7,14 @@
 import com.google.gson.JsonElement;
 import com.google.gson.JsonObject;
 import cpw.mods.fml.common.Loader;
+import it.unimi.dsi.fastutil.objects.Object2ObjectLinkedOpenHashMap;
+
 import net.minecraft.network.PacketBuffer;
 import org.jetbrains.annotations.ApiStatus;
 import org.jetbrains.annotations.NotNull;
 
 import java.io.File;
 import java.nio.file.Path;
-import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.NoSuchElementException;
@@ -23,7 +24,7 @@
 @Deprecated
 public class Config {
 
-    private static final Map<String, Config> configs = new HashMap<>();
+    private static final Map<String, Config> configs = new Object2ObjectLinkedOpenHashMap<>();
     private static final Path configPath = Loader.instance().getConfigDir().toPath();
 
     @NotNull
@@ -44,8 +45,8 @@ public static Builder builder(String name) {
 
     private final String name;
     private final String basePath;
-    private final Map<String, Config> categories = new HashMap<>();
-    private final Map<String, Value> values = new HashMap<>();
+    private final Map<String, Config> categories = new Object2ObjectLinkedOpenHashMap<>();
+    private final Map<String, Value> values = new Object2ObjectLinkedOpenHashMap<>();
     private final File filePath;
     private final boolean synced;
 
@@ -159,8 +160,8 @@ public static class Builder {
         private final String name;
         private final Builder parent;
         private String basePath = "modularui";
-        private final Map<String, Config> categories = new HashMap<>();
-        private final Map<String, Value> values = new HashMap<>();
+        private final Map<String, Config> categories = new Object2ObjectLinkedOpenHashMap<>();
+        private final Map<String, Value> values = new Object2ObjectLinkedOpenHashMap<>();
         private boolean synced = true;
 
         private Builder(String name, Builder parent) {
diff --git a/src/main/java/com/cleanroommc/modularui/drawable/DrawableSerialization.java b/src/main/java/com/cleanroommc/modularui/drawable/DrawableSerialization.java
index 619b3db6..66df2719 100644
--- a/src/main/java/com/cleanroommc/modularui/drawable/DrawableSerialization.java
+++ b/src/main/java/com/cleanroommc/modularui/drawable/DrawableSerialization.java
@@ -12,20 +12,20 @@
 import com.google.gson.JsonParseException;
 import com.google.gson.JsonSerializationContext;
 import com.google.gson.JsonSerializer;
+import it.unimi.dsi.fastutil.objects.Object2ObjectOpenHashMap;
 import org.jetbrains.annotations.ApiStatus;
 import org.jetbrains.annotations.NotNull;
 
 import java.lang.reflect.Type;
 import java.util.ArrayList;
-import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.function.Function;
 
 public class DrawableSerialization implements JsonSerializer<IDrawable>, JsonDeserializer<IDrawable> {
 
-    private static final Map<String, Function<JsonObject, IDrawable>> DRAWABLE_TYPES = new HashMap<>();
-    private static final Map<String, UITexture> TEXTURES = new HashMap<>();
+    private static final Map<String, Function<JsonObject, IDrawable>> DRAWABLE_TYPES = new Object2ObjectOpenHashMap<>();
+    private static final Map<String, UITexture> TEXTURES = new Object2ObjectOpenHashMap<>();
 
     public static void registerTexture(String s, UITexture texture) {
         TEXTURES.put(s, texture);
diff --git a/src/main/java/com/cleanroommc/modularui/drawable/Stencil.java b/src/main/java/com/cleanroommc/modularui/drawable/Stencil.java
index b0b8b257..a5520e38 100644
--- a/src/main/java/com/cleanroommc/modularui/drawable/Stencil.java
+++ b/src/main/java/com/cleanroommc/modularui/drawable/Stencil.java
@@ -2,8 +2,10 @@
 
 import com.cleanroommc.modularui.api.layout.IViewportStack;
 import com.cleanroommc.modularui.screen.viewport.GuiContext;
-import com.cleanroommc.modularui.utils.ArrayListStack;
 import com.cleanroommc.modularui.widget.sizer.Area;
+
+import it.unimi.dsi.fastutil.objects.ObjectArrayList;
+
 import net.minecraft.client.renderer.Tessellator;
 import org.jetbrains.annotations.Nullable;
 import org.lwjgl.opengl.GL11;
@@ -13,9 +15,9 @@
 public class Stencil {
 
     // Stores a stack of areas that are transformed, so it represents the actual area
-    private final static ArrayListStack<Area> stencils = new ArrayListStack<>();
+    private final static ObjectArrayList<Area> stencils = new ObjectArrayList<>();
     // Stores a stack of stencilShapes which is used to mark and remove the stencil shape area
-    private final static ArrayListStack<Runnable> stencilShapes = new ArrayListStack<>();
+    private final static ObjectArrayList<Runnable> stencilShapes = new ObjectArrayList<>();
     // the current highest stencil value
     private static int stencilValue = 0;
 
diff --git a/src/main/java/com/cleanroommc/modularui/factory/GuiManager.java b/src/main/java/com/cleanroommc/modularui/factory/GuiManager.java
index bedfe7b5..5f838090 100644
--- a/src/main/java/com/cleanroommc/modularui/factory/GuiManager.java
+++ b/src/main/java/com/cleanroommc/modularui/factory/GuiManager.java
@@ -17,6 +17,10 @@
 import cpw.mods.fml.relauncher.Side;
 import cpw.mods.fml.relauncher.SideOnly;
 import io.netty.buffer.Unpooled;
+import it.unimi.dsi.fastutil.objects.Object2ObjectMap;
+
+import it.unimi.dsi.fastutil.objects.Object2ObjectOpenHashMap;
+
 import net.minecraft.client.Minecraft;
 import net.minecraft.client.entity.EntityPlayerSP;
 import net.minecraft.entity.player.EntityPlayer;
@@ -33,7 +37,7 @@
 
 public class GuiManager {
 
-    private static final Map<String, UIFactory<?>> FACTORIES = new HashMap<>(16);
+    private static final Object2ObjectMap<String, UIFactory<?>> FACTORIES = new Object2ObjectOpenHashMap<>(16);
 
     private static GuiScreenWrapper lastMui;
     private static final List<EntityPlayer> openedContainers = new ArrayList<>(4);
diff --git a/src/main/java/com/cleanroommc/modularui/holoui/HoloUI.java b/src/main/java/com/cleanroommc/modularui/holoui/HoloUI.java
index e48138e1..5a789d3e 100644
--- a/src/main/java/com/cleanroommc/modularui/holoui/HoloUI.java
+++ b/src/main/java/com/cleanroommc/modularui/holoui/HoloUI.java
@@ -2,6 +2,9 @@
 
 import com.cleanroommc.modularui.screen.ModularScreen;
 import com.cleanroommc.modularui.screen.NEISettingsImpl;
+
+import it.unimi.dsi.fastutil.objects.Object2ObjectOpenHashMap;
+
 import net.minecraft.client.Minecraft;
 import net.minecraft.entity.player.EntityPlayer;
 import net.minecraft.util.ResourceLocation;
@@ -18,7 +21,7 @@
 @ApiStatus.Experimental
 public class HoloUI {
 
-    private static final Map<ResourceLocation, Supplier<ModularScreen>> syncedHolos = new HashMap<>();
+    private static final Map<ResourceLocation, Supplier<ModularScreen>> syncedHolos = new Object2ObjectOpenHashMap<>();
 
     public static void registerSyncedHoloUI(ResourceLocation loc, Supplier<ModularScreen> screen) {
         syncedHolos.put(loc, screen);
diff --git a/src/main/java/com/cleanroommc/modularui/screen/ModularScreen.java b/src/main/java/com/cleanroommc/modularui/screen/ModularScreen.java
index 373f3e93..2953c315 100644
--- a/src/main/java/com/cleanroommc/modularui/screen/ModularScreen.java
+++ b/src/main/java/com/cleanroommc/modularui/screen/ModularScreen.java
@@ -16,6 +16,11 @@
 import com.cleanroommc.modularui.widgets.Dialog;
 import cpw.mods.fml.relauncher.Side;
 import cpw.mods.fml.relauncher.SideOnly;
+import it.unimi.dsi.fastutil.objects.Object2ObjectArrayMap;
+import it.unimi.dsi.fastutil.objects.Object2ObjectMap;
+import it.unimi.dsi.fastutil.objects.Object2ObjectOpenHashMap;
+import it.unimi.dsi.fastutil.objects.ObjectIterator;
+
 import net.minecraft.client.Minecraft;
 import net.minecraft.client.gui.GuiScreen;
 import net.minecraft.client.renderer.RenderHelper;
@@ -30,8 +35,6 @@
 import javax.annotation.Nonnegative;
 import java.util.ArrayList;
 import java.util.Collections;
-import java.util.HashMap;
-import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
@@ -70,8 +73,8 @@ public static ModularScreen getCurrent() {
     private final PanelManager panelManager;
     private final GuiContext context = new GuiContext(this);
     private final Area screenArea = new Area();
-    private final Map<Class<?>, List<IGuiAction>> guiActionListeners = new HashMap<>();
-    private final Map<IWidget, Runnable> frameUpdates = new HashMap<>();
+    private final Map<Class<?>, List<IGuiAction>> guiActionListeners = new Object2ObjectOpenHashMap<>();
+    private final Object2ObjectArrayMap<IWidget, Runnable> frameUpdates = new Object2ObjectArrayMap<>();
 
     private ITheme currentTheme;
     private GuiScreenWrapper screenWrapper;
@@ -218,8 +221,8 @@ public void onUpdate() {
     @MustBeInvokedByOverriders
     public void onFrameUpdate() {
         this.panelManager.checkDirty();
-        for (Iterator<Map.Entry<IWidget, Runnable>> iterator = this.frameUpdates.entrySet().iterator(); iterator.hasNext();) {
-            Map.Entry<IWidget, Runnable> entry = iterator.next();
+        for (ObjectIterator<Object2ObjectMap.Entry<IWidget, Runnable>> iterator = this.frameUpdates.object2ObjectEntrySet().fastIterator(); iterator.hasNext(); ) {
+            Object2ObjectMap.Entry<IWidget, Runnable> entry = iterator.next();
             if (!entry.getKey().isValid()) {
                 iterator.remove();
                 continue;
diff --git a/src/main/java/com/cleanroommc/modularui/screen/viewport/GuiViewportStack.java b/src/main/java/com/cleanroommc/modularui/screen/viewport/GuiViewportStack.java
index 2bb8f514..eb5f6180 100644
--- a/src/main/java/com/cleanroommc/modularui/screen/viewport/GuiViewportStack.java
+++ b/src/main/java/com/cleanroommc/modularui/screen/viewport/GuiViewportStack.java
@@ -2,9 +2,10 @@
 
 import com.cleanroommc.modularui.api.layout.IViewport;
 import com.cleanroommc.modularui.api.layout.IViewportStack;
-import com.cleanroommc.modularui.utils.ArrayListStack;
 import com.cleanroommc.modularui.utils.GuiUtils;
 import com.cleanroommc.modularui.widget.sizer.Area;
+
+import it.unimi.dsi.fastutil.objects.ObjectArrayList;
 import org.jetbrains.annotations.Nullable;
 import org.lwjgl.util.vector.Matrix4f;
 import org.lwjgl.util.vector.Vector2f;
@@ -24,7 +25,7 @@ public class GuiViewportStack implements IViewportStack {
 
     private static final Vector3f sharedVec = new Vector3f();
 
-    private final ArrayListStack<TransformationMatrix> viewportStack = new ArrayListStack<>();
+    private final ObjectArrayList<TransformationMatrix> viewportStack = new ObjectArrayList<>();
     private final List<Area> viewportAreas = new ArrayList<>();
     private TransformationMatrix top;
     private TransformationMatrix topViewport;
diff --git a/src/main/java/com/cleanroommc/modularui/test/TestGui.java b/src/main/java/com/cleanroommc/modularui/test/TestGui.java
index d5d5cd6d..52d5dfba 100644
--- a/src/main/java/com/cleanroommc/modularui/test/TestGui.java
+++ b/src/main/java/com/cleanroommc/modularui/test/TestGui.java
@@ -13,9 +13,9 @@
 import com.cleanroommc.modularui.widgets.layout.Grid;
 import cpw.mods.fml.relauncher.Side;
 import cpw.mods.fml.relauncher.SideOnly;
+import it.unimi.dsi.fastutil.objects.Object2ObjectOpenHashMap;
 import org.jetbrains.annotations.NotNull;
 
-import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.concurrent.atomic.AtomicReference;
@@ -41,7 +41,7 @@ public void onClose() {
         if (this.lines == null) {
             this.lines = IntStream.range(0, 20).mapToObj(i -> "Option " + (i + 1)).collect(Collectors.toList());
             this.configuredOptions = this.lines;
-            this.availableElements = new HashMap<>();
+            this.availableElements = new Object2ObjectOpenHashMap<>();
         }
         AtomicReference<SortableListWidget<String, SortableListWidget.Item<String>>> ref = new AtomicReference<>(null);
         List<List<AvailableElement>> availableMatrix = Grid.mapToMatrix(2, this.lines, (index, value) -> {
diff --git a/src/main/java/com/cleanroommc/modularui/theme/Theme.java b/src/main/java/com/cleanroommc/modularui/theme/Theme.java
index 8c7b8acb..674274e6 100644
--- a/src/main/java/com/cleanroommc/modularui/theme/Theme.java
+++ b/src/main/java/com/cleanroommc/modularui/theme/Theme.java
@@ -5,7 +5,8 @@
 import com.cleanroommc.modularui.api.IThemeApi;
 import com.cleanroommc.modularui.screen.Tooltip;
 
-import java.util.HashMap;
+import it.unimi.dsi.fastutil.objects.Object2ObjectOpenHashMap;
+
 import java.util.Map;
 
 public class Theme implements ITheme {
@@ -18,7 +19,7 @@ public class Theme implements ITheme {
     public static final String TEXT_FIELD = "textField";
     public static final String TOGGLE_BUTTON = "toggleButton";
 
-    private final Map<String, WidgetTheme> widgetThemes = new HashMap<>();
+    private final Map<String, WidgetTheme> widgetThemes = new Object2ObjectOpenHashMap<>();
 
     private final String id;
     private final ITheme parentTheme;
diff --git a/src/main/java/com/cleanroommc/modularui/theme/ThemeAPI.java b/src/main/java/com/cleanroommc/modularui/theme/ThemeAPI.java
index 5d275d04..3b1600d0 100644
--- a/src/main/java/com/cleanroommc/modularui/theme/ThemeAPI.java
+++ b/src/main/java/com/cleanroommc/modularui/theme/ThemeAPI.java
@@ -7,13 +7,14 @@
 import com.cleanroommc.modularui.drawable.GuiTextures;
 import com.cleanroommc.modularui.utils.Color;
 import com.cleanroommc.modularui.utils.JsonBuilder;
+
+import it.unimi.dsi.fastutil.objects.Object2ObjectMap;
+import it.unimi.dsi.fastutil.objects.Object2ObjectOpenHashMap;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
 import java.util.ArrayList;
-import java.util.HashMap;
 import java.util.List;
-import java.util.Map;
 import java.util.Objects;
 
 public class ThemeAPI implements IThemeApi {
@@ -22,12 +23,12 @@ public class ThemeAPI implements IThemeApi {
     public static final String DEFAULT = "DEFAULT";
     public static final ITheme DEFAULT_DEFAULT = new DefaultTheme();
 
-    private final Map<String, ITheme> THEMES = new HashMap<>();
-    protected final Map<String, List<JsonBuilder>> defaultThemes = new HashMap<>();
-    protected final Map<String, WidgetTheme> defaultWidgetThemes = new HashMap<>();
-    protected final Map<String, WidgetThemeParser> widgetThemeFunctions = new HashMap<>();
-    protected final Map<String, String> jsonScreenThemes = new HashMap<>();
-    private final Map<String, String> screenThemes = new HashMap<>();
+    private final Object2ObjectMap<String, ITheme> THEMES = new Object2ObjectOpenHashMap<>();
+    protected final Object2ObjectMap<String, List<JsonBuilder>> defaultThemes = new Object2ObjectOpenHashMap<>();
+    protected final Object2ObjectMap<String, WidgetTheme> defaultWidgetThemes = new Object2ObjectOpenHashMap<>();
+    protected final Object2ObjectMap<String, WidgetThemeParser> widgetThemeFunctions = new Object2ObjectOpenHashMap<>();
+    protected final Object2ObjectOpenHashMap<String, String> jsonScreenThemes = new Object2ObjectOpenHashMap<>();
+    private final Object2ObjectMap<String, String> screenThemes = new Object2ObjectOpenHashMap<>();
 
     private ThemeAPI() {
         registerWidgetTheme(Theme.PANEL, new WidgetTheme(GuiTextures.MC_BACKGROUND, null, Color.WHITE.main, 0xFF404040, false), WidgetTheme::new);
diff --git a/src/main/java/com/cleanroommc/modularui/theme/ThemeManager.java b/src/main/java/com/cleanroommc/modularui/theme/ThemeManager.java
index 7fc9e855..df82dcf6 100644
--- a/src/main/java/com/cleanroommc/modularui/theme/ThemeManager.java
+++ b/src/main/java/com/cleanroommc/modularui/theme/ThemeManager.java
@@ -15,6 +15,8 @@
 import com.google.gson.JsonParseException;
 import cpw.mods.fml.relauncher.Side;
 import cpw.mods.fml.relauncher.SideOnly;
+import it.unimi.dsi.fastutil.objects.*;
+
 import net.minecraft.client.resources.IResource;
 import net.minecraft.client.resources.IResourceManager;
 import net.minecraft.client.resources.IResourceManagerReloadListener;
@@ -24,8 +26,6 @@
 import org.jetbrains.annotations.ApiStatus;
 
 import java.util.ArrayList;
-import java.util.HashMap;
-import java.util.HashSet;
 import java.util.Iterator;
 import java.util.List;
 import java.util.ListIterator;
@@ -50,7 +50,7 @@ public static void reload() {
     }
 
     private static void loadThemesJsons() {
-        Map<String, List<String>> themes = new HashMap<>();
+        Map<String, List<String>> themes = new Object2ObjectOpenHashMap<>();
         // find any theme.json files under any domain
         // works with mods like resource loader
         ObjectList<String> themesJsons = ObjectList.create();
@@ -91,7 +91,7 @@ private static void loadThemesJsons() {
     }
 
     public static void loadThemes(Map<String, List<String>> themesPaths) {
-        Map<String, ThemeJson> themeMap = new HashMap<>();
+        Map<String, ThemeJson> themeMap = new Object2ObjectOpenHashMap<>();
 
         // load json files from the path and parse their parent
         for (Map.Entry<String, List<String>> entry : themesPaths.entrySet()) {
@@ -112,7 +112,7 @@ public static void loadThemes(Map<String, List<String>> themesPaths) {
         if (themeMap.isEmpty()) return;
         // create a sorted list of themes
 
-        Map<String, ThemeJson> sortedThemes = new HashMap<>();
+        Map<String, ThemeJson> sortedThemes = new Object2ObjectLinkedOpenHashMap<>();
         Iterator<Map.Entry<String, ThemeJson>> iterator;
         boolean changed;
         do {
@@ -137,12 +137,12 @@ public static void loadThemes(Map<String, List<String>> themesPaths) {
     }
 
     private static void validateAncestorTree(Map<String, ThemeJson> themeMap) {
-        Set<ThemeJson> invalidThemes = new HashSet<>();
+        Set<ThemeJson> invalidThemes = new ObjectOpenHashSet<>();
         for (ThemeJson theme : themeMap.values()) {
             if (invalidThemes.contains(theme)) {
                 continue;
             }
-            Set<ThemeJson> parents = new HashSet<>();
+            Set<ThemeJson> parents = new ObjectOpenHashSet<>();
             parents.add(theme);
             ThemeJson parent = theme;
             do {
@@ -216,7 +216,7 @@ private static void loadScreenThemes(JsonObject json) {
     }
 
     private static void validateJsonScreenThemes() {
-        for (Iterator<Map.Entry<String, String>> iterator = ThemeAPI.INSTANCE.jsonScreenThemes.entrySet().iterator(); iterator.hasNext(); ) {
+        for (ObjectIterator<Object2ObjectMap.Entry<String, String>> iterator = ThemeAPI.INSTANCE.jsonScreenThemes.object2ObjectEntrySet().fastIterator(); iterator.hasNext(); ) {
             Map.Entry<String, String> entry = iterator.next();
             if (!ThemeAPI.INSTANCE.hasTheme(entry.getValue())) {
                 ModularUI.LOGGER.error("Tried to register theme '{}' for screen '{}', but theme does not exist", entry.getValue(), entry.getKey());
@@ -269,7 +269,7 @@ private Theme deserialize() {
             }
 
             // parse fallback theme for widget themes
-            Map<String, WidgetTheme> widgetThemes = new HashMap<>();
+            Map<String, WidgetTheme> widgetThemes = new Object2ObjectOpenHashMap<>();
             WidgetTheme parentWidgetTheme = parent.getFallback();
             WidgetTheme fallback = new WidgetTheme(parentWidgetTheme, jsonBuilder.getJson(), jsonBuilder.getJson());
             widgetThemes.put(Theme.FALLBACK, fallback);
diff --git a/src/main/java/com/cleanroommc/modularui/utils/Alignment.java b/src/main/java/com/cleanroommc/modularui/utils/Alignment.java
index a81c9c20..c77fe168 100644
--- a/src/main/java/com/cleanroommc/modularui/utils/Alignment.java
+++ b/src/main/java/com/cleanroommc/modularui/utils/Alignment.java
@@ -5,14 +5,14 @@
 import com.google.gson.JsonDeserializer;
 import com.google.gson.JsonElement;
 import com.google.gson.JsonParseException;
+import it.unimi.dsi.fastutil.objects.Object2ObjectOpenHashMap;
 
 import java.lang.reflect.Type;
-import java.util.HashMap;
 import java.util.Map;
 
 public class Alignment {
 
-    private static final Map<String, Alignment> ALIGNMENT_MAP = new HashMap<>();
+    private static final Map<String, Alignment> ALIGNMENT_MAP = new Object2ObjectOpenHashMap<>();
 
     public final float x, y;
 
diff --git a/src/main/java/com/cleanroommc/modularui/utils/ArrayListStack.java b/src/main/java/com/cleanroommc/modularui/utils/ArrayListStack.java
deleted file mode 100644
index 986deaee..00000000
--- a/src/main/java/com/cleanroommc/modularui/utils/ArrayListStack.java
+++ /dev/null
@@ -1,24 +0,0 @@
-package com.cleanroommc.modularui.utils;
-
-import java.util.ArrayList;
-import java.util.NoSuchElementException;
-
-/**
- * Extension of ArrayList, inspired by it.unimi.dsi.fastutil.Stack
- */
-public class ArrayListStack<E> extends ArrayList<E> {
-
-    public void push(E o) {
-        add(o);
-    }
-
-    public E pop() {
-        if (isEmpty()) throw new NoSuchElementException();
-        return remove(size() - 1);
-    }
-
-    public E top() {
-        if (isEmpty()) throw new NoSuchElementException();
-        return get(size() - 1);
-    }
-}
diff --git a/src/main/java/com/cleanroommc/modularui/utils/ColorShade.java b/src/main/java/com/cleanroommc/modularui/utils/ColorShade.java
index c9ff8eb7..65767096 100644
--- a/src/main/java/com/cleanroommc/modularui/utils/ColorShade.java
+++ b/src/main/java/com/cleanroommc/modularui/utils/ColorShade.java
@@ -1,13 +1,12 @@
 package com.cleanroommc.modularui.utils;
 
+import it.unimi.dsi.fastutil.ints.IntArrayList;
+import it.unimi.dsi.fastutil.ints.IntIterable;
+import it.unimi.dsi.fastutil.ints.IntIterator;
+import it.unimi.dsi.fastutil.ints.IntIterators;
 import org.jetbrains.annotations.NotNull;
 
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.Iterator;
-import java.util.List;
-
-public class ColorShade implements Iterable<Integer> {
+public class ColorShade implements IntIterable {
 
     public static Builder builder(int main) {
         return new Builder(main);
@@ -43,32 +42,34 @@ public int brighter(int index) {
 
     @NotNull
     @Override
-    public Iterator<Integer> iterator() {
-        return Arrays.stream(this.all).iterator();
+    public IntIterator iterator() {
+        return IntIterators.wrap(this.all);
     }
 
     public static class Builder {
 
         private final int main;
-        private final List<Integer> darker = new ArrayList<>();
-        private final List<Integer> brighter = new ArrayList<>();
+        private final IntArrayList darker = new IntArrayList();
+        private final IntArrayList brighter = new IntArrayList();
 
         public Builder(int main) {
             this.main = main;
         }
 
         public Builder addDarker(int... darker) {
-            Arrays.stream(darker).forEach(this.darker::add);
+            this.darker.addElements(this.darker.size(), darker, 0, darker.length);
             return this;
         }
 
         public Builder addBrighter(int... brighter) {
-            Arrays.stream(brighter).forEach(this.brighter::add);
+            this.brighter.addElements(this.brighter.size(), brighter, 0, brighter.length);
             return this;
         }
 
         public ColorShade build() {
-            return new ColorShade(this.main, this.brighter.stream().mapToInt(Integer::intValue).toArray(), this.darker.stream().mapToInt(Integer::intValue).toArray());
+            this.darker.trim();
+            this.brighter.trim();
+            return new ColorShade(this.main, this.brighter.elements(), this.darker.elements());
         }
     }
 }
diff --git a/src/main/java/com/cleanroommc/modularui/utils/ObjectList.java b/src/main/java/com/cleanroommc/modularui/utils/ObjectList.java
index 8bb4a76e..09f3a342 100644
--- a/src/main/java/com/cleanroommc/modularui/utils/ObjectList.java
+++ b/src/main/java/com/cleanroommc/modularui/utils/ObjectList.java
@@ -1,17 +1,14 @@
 package com.cleanroommc.modularui.utils;
 
-import com.google.common.collect.ForwardingList;
-import com.google.common.collect.Lists;
+import it.unimi.dsi.fastutil.objects.ObjectCollection;
+import it.unimi.dsi.fastutil.objects.ObjectIterator;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
-import java.util.ArrayList;
-import java.util.Arrays;
 import java.util.Collection;
 import java.util.Iterator;
-import java.util.List;
 
-public interface ObjectList<V> extends List<V>, Comparable<List<? extends V>> {
+public interface ObjectList<V> extends it.unimi.dsi.fastutil.objects.ObjectList<V> {
 
     static <V> ObjectArrayList<V> create() {
         return new ObjectArrayList<>();
@@ -25,6 +22,14 @@ static <V> ObjectArrayList<V> of(Collection<? extends V> c) {
         return new ObjectArrayList<>(c);
     }
 
+    static <V> ObjectArrayList<V> of(ObjectCollection<? extends V> c) {
+        return new ObjectArrayList<>(c);
+    }
+
+    static <V> ObjectArrayList<V> of(it.unimi.dsi.fastutil.objects.ObjectList<? extends V> l) {
+        return new ObjectArrayList<>(l);
+    }
+
     static <V> ObjectArrayList<V> of(V[] a) {
         return new ObjectArrayList<>(a);
     }
@@ -37,6 +42,10 @@ static <V> ObjectArrayList<V> of(Iterator<? extends V> i) {
         return new ObjectArrayList<>(i);
     }
 
+    static <V> ObjectArrayList<V> of(ObjectIterator<? extends V> i) {
+        return new ObjectArrayList<>(i);
+    }
+
     void addFirst(V v);
 
     void addLast(V v);
@@ -70,37 +79,41 @@ static <V> ObjectArrayList<V> of(Iterator<? extends V> i) {
     @NotNull
     V[] elements();
 
-    class ObjectArrayList<V> extends ForwardingList<V> implements ObjectList<V> {
-
-        final List<V> delegate;
+    class ObjectArrayList<V> extends it.unimi.dsi.fastutil.objects.ObjectArrayList<V> implements ObjectList<V> {
 
         public ObjectArrayList(int capacity) {
-            this.delegate = new ArrayList<>(capacity);
+            super(capacity);
         }
 
         public ObjectArrayList() {
-            this.delegate = new ArrayList<>();
         }
 
         public ObjectArrayList(Collection<? extends V> c) {
-            this.delegate = new ArrayList<>(c);
+            super(c);
+        }
+
+        public ObjectArrayList(ObjectCollection<? extends V> c) {
+            super(c);
+        }
+
+        public ObjectArrayList(it.unimi.dsi.fastutil.objects.ObjectList<? extends V> l) {
+            super(l);
         }
 
         public ObjectArrayList(V[] a) {
-            this.delegate = new ArrayList<>(Arrays.asList(a));
+            super(a);
         }
 
         public ObjectArrayList(V[] a, int offset, int length) {
-            this(Arrays.copyOfRange(a, offset, offset + length));
+            super(a, offset, length);
         }
 
         public ObjectArrayList(Iterator<? extends V> i) {
-            this.delegate = Lists.newArrayList(i);
+            super(i);
         }
 
-        @Override
-        protected List<V> delegate() {
-            return this.delegate;
+        public ObjectArrayList(ObjectIterator<? extends V> i) {
+            super(i);
         }
 
         @Override
@@ -152,21 +165,5 @@ public V peekLast() {
         public V pollLast() {
             return isEmpty() ? null : removeLast();
         }
-
-        @Override
-        public int compareTo(@NotNull List<? extends V> o) {
-            // I don't think this will be used
-            throw new UnsupportedOperationException();
-        }
-
-        @Override
-        public void trim() {
-            // Kept just for preserving consistency with 1.12.2 code. It looks to be not that important anyway.
-        }
-
-        @Override
-        public V[] elements() {
-            return (V[]) delegate.toArray();
-        }
     }
 }
diff --git a/src/main/java/com/cleanroommc/modularui/utils/math/MathBuilder.java b/src/main/java/com/cleanroommc/modularui/utils/math/MathBuilder.java
index 21aef77a..2e8b6de3 100644
--- a/src/main/java/com/cleanroommc/modularui/utils/math/MathBuilder.java
+++ b/src/main/java/com/cleanroommc/modularui/utils/math/MathBuilder.java
@@ -33,10 +33,11 @@
 import com.cleanroommc.modularui.utils.math.functions.utility.RandomInteger;
 import com.cleanroommc.modularui.widgets.textfield.BaseTextFieldWidget;
 
+import it.unimi.dsi.fastutil.objects.Object2ObjectOpenHashMap;
+
 import java.lang.reflect.Constructor;
 import java.text.ParsePosition;
 import java.util.ArrayList;
-import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 
@@ -62,12 +63,12 @@ public class MathBuilder {
      * Named variables that can be used in math expression by this
      * builder
      */
-    public final Map<String, Variable> variables = new HashMap<>();
+    public final Map<String, Variable> variables = new Object2ObjectOpenHashMap<>();
 
     /**
      * Map of functions which can be used in the math expressions
      */
-    public final Map<String, Class<? extends Function>> functions = new HashMap<>();
+    public final Map<String, Class<? extends Function>> functions = new Object2ObjectOpenHashMap<>();
 
     /**
      * Whether math expression parser should be strict about which characters
diff --git a/src/main/java/com/cleanroommc/modularui/utils/math/Operation.java b/src/main/java/com/cleanroommc/modularui/utils/math/Operation.java
index 0b2bd8a1..5a94aef4 100644
--- a/src/main/java/com/cleanroommc/modularui/utils/math/Operation.java
+++ b/src/main/java/com/cleanroommc/modularui/utils/math/Operation.java
@@ -1,5 +1,7 @@
 package com.cleanroommc.modularui.utils.math;
 
+import it.unimi.dsi.fastutil.objects.ObjectOpenHashSet;
+
 import java.util.HashSet;
 import java.util.Set;
 
@@ -130,7 +132,7 @@ public double calculate(double a, double b) {
         }
     };
 
-    public final static Set<String> OPERATORS = new HashSet<>();
+    public final static Set<String> OPERATORS = new ObjectOpenHashSet<>();
 
     public static boolean equals(double a, double b) {
         return Math.abs(a - b) < 0.00001;
diff --git a/src/main/java/com/cleanroommc/modularui/value/sync/GuiSyncManager.java b/src/main/java/com/cleanroommc/modularui/value/sync/GuiSyncManager.java
index 6184d19f..c29ab0b2 100644
--- a/src/main/java/com/cleanroommc/modularui/value/sync/GuiSyncManager.java
+++ b/src/main/java/com/cleanroommc/modularui/value/sync/GuiSyncManager.java
@@ -5,6 +5,10 @@
 import com.cleanroommc.modularui.screen.ModularContainer;
 import com.cleanroommc.modularui.widgets.slot.ModularSlot;
 import com.cleanroommc.modularui.widgets.slot.SlotGroup;
+
+import it.unimi.dsi.fastutil.objects.Object2ObjectLinkedOpenHashMap;
+import it.unimi.dsi.fastutil.objects.Object2ObjectOpenHashMap;
+
 import net.minecraft.entity.player.EntityPlayer;
 import net.minecraft.item.ItemStack;
 import net.minecraft.network.PacketBuffer;
@@ -23,9 +27,9 @@ public class GuiSyncManager {
     private final CursorSlotSyncHandler cursorSlotSyncHandler = new CursorSlotSyncHandler();
     private final EntityPlayer player;
     private final PlayerMainInvWrapper playerInventory;
-    private final Map<String, SyncHandler> syncHandlers = new LinkedHashMap<>();
-    private final Map<String, SlotGroup> slotGroups = new HashMap<>();
-    private final Map<SyncHandler, String> reverseSyncHandlers = new HashMap<>();
+    private final Map<String, SyncHandler> syncHandlers = new Object2ObjectLinkedOpenHashMap<>();
+    private final Map<String, SlotGroup> slotGroups = new Object2ObjectOpenHashMap<>();
+    private final Map<SyncHandler, String> reverseSyncHandlers = new Object2ObjectOpenHashMap<>();
     private ModularContainer container;
 
     private final List<Consumer<EntityPlayer>> openListener = new ArrayList<>();
diff --git a/src/main/java/com/cleanroommc/modularui/widgets/ListWidget.java b/src/main/java/com/cleanroommc/modularui/widgets/ListWidget.java
index 6cb95ccb..551f4eca 100644
--- a/src/main/java/com/cleanroommc/modularui/widgets/ListWidget.java
+++ b/src/main/java/com/cleanroommc/modularui/widgets/ListWidget.java
@@ -8,10 +8,11 @@
 import com.cleanroommc.modularui.widget.WidgetTree;
 import com.cleanroommc.modularui.widget.scroll.ScrollData;
 import com.cleanroommc.modularui.widget.scroll.VerticalScrollData;
+
+import it.unimi.dsi.fastutil.objects.Object2ObjectOpenHashMap;
 import org.jetbrains.annotations.Nullable;
 
 import java.util.Collection;
-import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
@@ -49,8 +50,8 @@ public static <T, V extends IValueWidget<T> & IWidget, W extends ListWidget<T, V
     }
 
     public static <T, I extends IWidget, W extends ListWidget<T, I, W>> ListWidget<T, I, W> builder(List<T> list, Function<T, I> creator) {
-        Map<T, I> map = new HashMap<>();
-        Map<I, T> map_reverse = new HashMap<>();
+        Map<T, I> map = new Object2ObjectOpenHashMap<>();
+        Map<I, T> map_reverse = new Object2ObjectOpenHashMap<>();
         ListWidget<T, I, W> listWidget = new ListWidget<>(map::get, map_reverse::get);
         for (T t : list) {
             I widget = creator.apply(t);
diff --git a/src/main/java/com/cleanroommc/modularui/widgets/SliderWidget.java b/src/main/java/com/cleanroommc/modularui/widgets/SliderWidget.java
index 3bb82a86..c7f82884 100644
--- a/src/main/java/com/cleanroommc/modularui/widgets/SliderWidget.java
+++ b/src/main/java/com/cleanroommc/modularui/widgets/SliderWidget.java
@@ -1,7 +1,6 @@
 package com.cleanroommc.modularui.widgets;
 
 import com.cleanroommc.modularui.api.GuiAxis;
-import com.cleanroommc.modularui.api.ITheme;
 import com.cleanroommc.modularui.api.drawable.IDrawable;
 import com.cleanroommc.modularui.api.value.IDoubleValue;
 import com.cleanroommc.modularui.api.widget.IGuiAction;
@@ -16,9 +15,10 @@
 import com.cleanroommc.modularui.widget.Widget;
 import com.cleanroommc.modularui.widget.sizer.Area;
 import com.cleanroommc.modularui.widget.sizer.Unit;
-import gnu.trove.iterator.TDoubleIterator;
-import gnu.trove.list.TDoubleList;
-import gnu.trove.list.array.TDoubleArrayList;
+import it.unimi.dsi.fastutil.doubles.DoubleArrayList;
+
+import it.unimi.dsi.fastutil.doubles.DoubleList;
+
 import net.minecraft.util.MathHelper;
 import org.jetbrains.annotations.NotNull;
 
@@ -28,7 +28,7 @@ public class SliderWidget extends Widget<SliderWidget> implements Interactable {
     private IDrawable stopperDrawable = new Rectangle().setColor(Color.withAlpha(Color.WHITE.main, 0.4f));
     private IDrawable handleDrawable = GuiTextures.BUTTON_CLEAN;
     private GuiAxis axis = GuiAxis.X;
-    private TDoubleList stopper;
+    private DoubleList stopper;
     private int stopperWidth = 2, stopperHeight = 4;
     private final Unit sliderWidth = new Unit(), sliderHeight = new Unit();
     private final Area sliderArea = new Area();
@@ -53,7 +53,7 @@ public void onInit() {
             this.doubleValue = new DoubleValue((this.max - this.min) * 0.5 + this.min);
         }
         if (this.each > 0 && this.stopper == null) {
-            this.stopper = new TDoubleArrayList();
+            this.stopper = new DoubleArrayList();
             for (double d = this.min; d < this.max; d += this.each) {
                 this.stopper.add(d);
             }
@@ -74,9 +74,7 @@ public boolean isValidSyncHandler(SyncHandler syncHandler) {
     public void drawBackground(GuiContext context, WidgetTheme widgetTheme) {
         super.drawBackground(context, widgetTheme);
         if (this.stopper != null && this.stopperDrawable != null && this.stopperWidth > 0 && this.stopperHeight > 0) {
-            TDoubleIterator it = this.stopper.iterator();
-            while (it.hasNext()) {
-                double stop = it.next();
+            for (double stop : this.stopper) {
                 int pos = valueToPos(stop) + this.sliderArea.getSize(this.axis) / 2;
                 if (this.axis.isHorizontal()) {
                     pos -= this.stopperWidth / 2;
@@ -209,19 +207,19 @@ public SliderWidget bounds(double min, double max) {
         return this;
     }
 
-    public SliderWidget stopper(TDoubleList stopper) {
-        if (this.stopper == null) this.stopper = new TDoubleArrayList();
+    public SliderWidget stopper(DoubleList stopper) {
+        if (this.stopper == null) this.stopper = new DoubleArrayList();
         this.stopper.addAll(stopper);
-        this.stopper.sort();
+        this.stopper.sort(Double::compare);
         return this;
     }
 
     public SliderWidget stopper(double... stopper) {
-        if (this.stopper == null) this.stopper = new TDoubleArrayList();
+        if (this.stopper == null) this.stopper = new DoubleArrayList();
         for (double stop : stopper) {
             this.stopper.add(stop);
         }
-        this.stopper.sort();
+        this.stopper.sort(Double::compare);
         return this;
     }
 
diff --git a/src/main/java/com/cleanroommc/modularui/widgets/SlotGroupWidget.java b/src/main/java/com/cleanroommc/modularui/widgets/SlotGroupWidget.java
index 1e445bad..f6fe1e60 100644
--- a/src/main/java/com/cleanroommc/modularui/widgets/SlotGroupWidget.java
+++ b/src/main/java/com/cleanroommc/modularui/widgets/SlotGroupWidget.java
@@ -3,10 +3,10 @@
 import com.cleanroommc.modularui.api.widget.ISynced;
 import com.cleanroommc.modularui.api.widget.IWidget;
 import com.cleanroommc.modularui.widget.ParentWidget;
-import gnu.trove.map.TCharIntMap;
-import gnu.trove.map.TCharObjectMap;
-import gnu.trove.map.hash.TCharIntHashMap;
-import gnu.trove.map.hash.TCharObjectHashMap;
+import it.unimi.dsi.fastutil.chars.Char2IntMap;
+import it.unimi.dsi.fastutil.chars.Char2IntOpenHashMap;
+import it.unimi.dsi.fastutil.chars.Char2ObjectMap;
+import it.unimi.dsi.fastutil.chars.Char2ObjectOpenHashMap;
 
 import java.util.ArrayList;
 import java.util.Collections;
@@ -71,7 +71,7 @@ public static class Builder {
 
         private String syncKey;
         private final List<String> matrix = new ArrayList<>();
-        private final TCharObjectMap<Object> keys = new TCharObjectHashMap<>();
+        private final Char2ObjectMap<Object> keys = new Char2ObjectOpenHashMap<>();
 
         private Builder() {
             this.keys.put(' ', null);
@@ -105,7 +105,7 @@ public Builder key(char c, IntFunction<IWidget> widget) {
 
         public SlotGroupWidget build() {
             SlotGroupWidget slotGroupWidget = new SlotGroupWidget();
-            TCharIntMap charCount = new TCharIntHashMap();
+            Char2IntMap charCount = new Char2IntOpenHashMap();
             int x = 0, y = 0, maxWidth = 0;
             int syncId = 0;
             for (String row : this.matrix) {
diff --git a/src/main/java/com/cleanroommc/modularui/widgets/SortableListWidget.java b/src/main/java/com/cleanroommc/modularui/widgets/SortableListWidget.java
index d95da21a..a65ded9b 100644
--- a/src/main/java/com/cleanroommc/modularui/widgets/SortableListWidget.java
+++ b/src/main/java/com/cleanroommc/modularui/widgets/SortableListWidget.java
@@ -7,12 +7,13 @@
 import com.cleanroommc.modularui.drawable.GuiTextures;
 import com.cleanroommc.modularui.widget.DraggableWidget;
 import com.cleanroommc.modularui.widget.WidgetTree;
+
+import it.unimi.dsi.fastutil.objects.Object2ObjectOpenHashMap;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
 import java.util.ArrayList;
 import java.util.Collection;
-import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
@@ -25,7 +26,7 @@ public class SortableListWidget<T, I extends SortableListWidget.Item<T>> extends
     public static <T, I extends SortableListWidget.Item<T>> SortableListWidget<T, I> sortableBuilder(Collection<T> fullList, List<T> list, Function<T, I> builder) {
         Objects.requireNonNull(list);
         Objects.requireNonNull(builder);
-        Map<T, I> map = new HashMap<>();
+        Map<T, I> map = new Object2ObjectOpenHashMap<>();
         SortableListWidget<T, I> sortableListWidget = new SortableListWidget<>(map::get);
         for (T t : fullList) {
             I item = builder.apply(t);
diff --git a/src/main/java/com/cleanroommc/modularui/widgets/layout/Grid.java b/src/main/java/com/cleanroommc/modularui/widgets/layout/Grid.java
index ccf4c6ec..5d708daf 100644
--- a/src/main/java/com/cleanroommc/modularui/widgets/layout/Grid.java
+++ b/src/main/java/com/cleanroommc/modularui/widgets/layout/Grid.java
@@ -8,8 +8,8 @@
 import com.cleanroommc.modularui.widget.ScrollWidget;
 import com.cleanroommc.modularui.widget.sizer.Area;
 import com.cleanroommc.modularui.widget.sizer.Box;
-import gnu.trove.list.TIntList;
-import gnu.trove.list.array.TIntArrayList;
+import it.unimi.dsi.fastutil.ints.IntArrayList;
+import it.unimi.dsi.fastutil.ints.IntList;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
@@ -54,8 +54,8 @@ private int getElementHeight(Area area) {
 
     @Override
     public void layoutWidgets() {
-        TIntList rowSizes = new TIntArrayList();
-        TIntList colSizes = new TIntArrayList();
+        IntList rowSizes = new IntArrayList();
+        IntList colSizes = new IntArrayList();
 
         int i = 0, j;
         for (List<IWidget> row : this.matrix) {
@@ -129,7 +129,7 @@ public int getDefaultHeight() {
 
     @Override
     public int getDefaultWidth() {
-        TIntList colSizes = new TIntArrayList();
+        IntList colSizes = new IntArrayList();
         int i = 0, j;
         for (List<? extends IWidget> row : this.matrix) {
             j = 0;
@@ -138,13 +138,17 @@ public int getDefaultWidth() {
                     colSizes.add(this.minColWidth);
                 }
                 if (child != null) {
-                    colSizes.set(j, Math.max(colSizes.get(j), getElementWidth(child.getArea())));
+                    colSizes.set(j, Math.max(colSizes.getInt(j), getElementWidth(child.getArea())));
                 }
                 j++;
             }
             i++;
         }
-        return colSizes.sum();
+        int w = 0;
+        for (int colWidth : colSizes) {
+            w += colWidth;
+        }
+        return w;
     }
 
     public <I extends IWidget> Grid matrix(List<List<I>> matrix) {