Tabs, card panels and showing/hiding widgets (#74)3.0.0

* Add beta API for hiding and showing widget peers, add default implementation for slots

* Add WCardPanel

* Tab thingies

* Improve WPanel.toString

* Fix tabs, add dark mode

* Add box fillers

* Tabs again

* Tab go brrr

* Revert modmenu changes

* Fix card panels not initialising hidden widgets properly

* Fix slots not being hidden when they should be

* Things

* Revert "Add box fillers"

This reverts commit 1ea1bfbb

* foo

* revert more modmenu changes

* Add tab titles and switch to a builder model for adding tabs

* Document tab builders

* Make hidden widgets release their focus

* Replace outdated since tags with TAB_VERSION

* Fix compilation of WTabPanel

* TAB_VERSION => 3.0.0

* Add focusing support to tabs

18 files changed, 732 insertions, 11 deletions

diff --git a/src/main/java/io/github/cottonmc/cotton/gui/ValidatedSlot.java b/src/main/java/io/github/cottonmc/cotton/gui/ValidatedSlot.java
index a45fee6..69acc85 100644
--- a/src/main/java/io/github/cottonmc/cotton/gui/ValidatedSlot.java
+++ b/src/main/java/io/github/cottonmc/cotton/gui/ValidatedSlot.java
@@ -3,6 +3,7 @@ package io.github.cottonmc.cotton.gui;
 import com.google.common.collect.HashMultimap;
 import com.google.common.collect.Multimap;
 import io.github.cottonmc.cotton.gui.widget.WItemSlot;
+import io.github.cottonmc.cotton.gui.impl.access.SlotAccessor;
 import net.minecraft.entity.player.PlayerEntity;
 import net.minecraft.inventory.Inventory;
 import net.minecraft.item.ItemStack;
@@ -16,15 +17,20 @@ import java.util.function.Predicate;
 public class ValidatedSlot extends Slot {
 	private static final Logger LOGGER = LogManager.getLogger();
 	private final int slotNumber;
+	// Original positions that will be restored when this slot is reshown
+	private final int originalX, originalY;
 	private boolean insertingAllowed = true;
 	private boolean takingAllowed = true;
 	private Predicate<ItemStack> filter;
 	protected final Multimap<WItemSlot, WItemSlot.ChangeListener> listeners = HashMultimap.create();
+	private boolean visible = true;
 
 	public ValidatedSlot(Inventory inventory, int index, int x, int y) {
 		super(inventory, index, x, y);
 		if (inventory==null) throw new IllegalArgumentException("Can't make an itemslot from a null inventory!");
 		this.slotNumber = index;
+		this.originalX = x;
+		this.originalY = y;
 	}
 	
 	@Override
@@ -142,4 +148,35 @@ public class ValidatedSlot extends Slot {
 		Objects.requireNonNull(listener, "listener");
 		listeners.put(owner, listener);
 	}
-}
\ No newline at end of file
+
+	/**
+	 * Tests whether this slot is visible.
+	 *
+	 * @return true if this slot is visible, false otherwise
+	 * @since 3.0.0
+	 */
+	public boolean isVisible() {
+		return visible;
+	}
+
+	/**
+	 * Sets whether this slot is visible.
+	 *
+	 * @param visible true if this slot if visible, false otherwise
+	 * @since 3.0.0
+	 */
+	public void setVisible(boolean visible) {
+		if (this.visible != visible) {
+			this.visible = visible;
+
+			SlotAccessor accessor = (SlotAccessor) this;
+			if (visible) {
+				accessor.setX(originalX);
+				accessor.setY(originalY);
+			} else {
+				accessor.setX(-100000);
+				accessor.setY(-100000);
+			}
+		}
+	}
+}
diff --git a/src/main/java/io/github/cottonmc/cotton/gui/client/CottonClientScreen.java b/src/main/java/io/github/cottonmc/cotton/gui/client/CottonClientScreen.java
index 01b0c70..8fc53e1 100644
--- a/src/main/java/io/github/cottonmc/cotton/gui/client/CottonClientScreen.java
+++ b/src/main/java/io/github/cottonmc/cotton/gui/client/CottonClientScreen.java
@@ -52,6 +52,8 @@ public class CottonClientScreen extends Screen implements TextHoverRendererScree
 		super.init(client, screenWidth, screenHeight);
 		client.keyboard.setRepeatEvents(true);
 		
+		WPanel root = description.getRootPanel();
+		if (root != null) root.addPainters();
 		description.addPainters();
 		reposition(screenWidth, screenHeight);
 	}
diff --git a/src/main/java/io/github/cottonmc/cotton/gui/client/CottonInventoryScreen.java b/src/main/java/io/github/cottonmc/cotton/gui/client/CottonInventoryScreen.java
index 210470d..e3a61a8 100644
--- a/src/main/java/io/github/cottonmc/cotton/gui/client/CottonInventoryScreen.java
+++ b/src/main/java/io/github/cottonmc/cotton/gui/client/CottonInventoryScreen.java
@@ -65,6 +65,8 @@ public class CottonInventoryScreen<T extends SyncedGuiDescription> extends Handl
 		super.init(client, screenWidth, screenHeight);
 		client.keyboard.setRepeatEvents(true);
 		
+		WPanel root = description.getRootPanel();
+		if (root != null) root.addPainters();
 		description.addPainters();
 		
 		reposition(screenWidth, screenHeight);
diff --git a/src/main/java/io/github/cottonmc/cotton/gui/client/modmenu/ConfigGui.java b/src/main/java/io/github/cottonmc/cotton/gui/client/modmenu/ConfigGui.java
index ccc9679..cd3fe0a 100644
--- a/src/main/java/io/github/cottonmc/cotton/gui/client/modmenu/ConfigGui.java
+++ b/src/main/java/io/github/cottonmc/cotton/gui/client/modmenu/ConfigGui.java
@@ -17,7 +17,7 @@ public class ConfigGui extends LightweightGuiDescription {
 	public ConfigGui(Screen previous) {
 		WGridPanel root = new WGridPanel();
 		setRootPanel(root);
-		
+
 		WToggleButton darkmodeButton = new WToggleButton(new TranslatableText("option.libgui.darkmode")) {
 			@Override
 			public void onToggle(boolean on) {
diff --git a/src/main/java/io/github/cottonmc/cotton/gui/client/modmenu/ModMenuSupport.java b/src/main/java/io/github/cottonmc/cotton/gui/client/modmenu/ModMenuSupport.java
index 5cec105..29ea6bf 100644
--- a/src/main/java/io/github/cottonmc/cotton/gui/client/modmenu/ModMenuSupport.java
+++ b/src/main/java/io/github/cottonmc/cotton/gui/client/modmenu/ModMenuSupport.java
@@ -21,11 +21,6 @@ public class ModMenuSupport implements ModMenuApi {
 			public void onClose() {
 				this.client.openScreen(screen);
 			}
-			
-			protected void init() {
-				super.init();
-				this.description.getRootPanel().validate(null);
-			};
 		};
 	}
 }
diff --git a/src/main/java/io/github/cottonmc/cotton/gui/impl/access/SlotAccessor.java b/src/main/java/io/github/cottonmc/cotton/gui/impl/access/SlotAccessor.java
new file mode 100644
index 0000000..954b4a8
--- /dev/null
+++ b/src/main/java/io/github/cottonmc/cotton/gui/impl/access/SlotAccessor.java
@@ -0,0 +1,14 @@
+package io.github.cottonmc.cotton.gui.impl.access;
+
+import net.minecraft.screen.slot.Slot;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.gen.Accessor;
+
+@Mixin(Slot.class)
+public interface SlotAccessor {
+	@Accessor("x")
+	void setX(int x);
+
+	@Accessor("y")
+	void setY(int y);
+}
diff --git a/src/main/java/io/github/cottonmc/cotton/gui/widget/WCardPanel.java b/src/main/java/io/github/cottonmc/cotton/gui/widget/WCardPanel.java
new file mode 100644
index 0000000..6c6449a
--- /dev/null
+++ b/src/main/java/io/github/cottonmc/cotton/gui/widget/WCardPanel.java
@@ -0,0 +1,189 @@
+package io.github.cottonmc.cotton.gui.widget;
+
+import io.github.cottonmc.cotton.gui.GuiDescription;
+import net.fabricmc.api.EnvType;
+import net.fabricmc.api.Environment;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.NoSuchElementException;
+
+/**
+ * Similar to the CardLayout in AWT, this panel displays one widget at a time from a list of widgets.
+ *
+ * @since 3.0.0
+ */
+public class WCardPanel extends WPanel {
+	private final List<WWidget> cards = new ArrayList<>();
+	private int selectedIndex = 0;
+
+	/**
+	 * Adds a card to this panel without resizing it.
+	 *
+	 * @param card the added card
+	 */
+	public void add(WWidget card) {
+		add(cards.size(), card);
+	}
+
+	/**
+	 * Adds a card to this panel without resizing it.
+	 *
+	 * @param index the index of the card
+	 * @param card  the added card
+	 */
+	public void add(int index, WWidget card) {
+		cards.add(index, card);
+
+		card.setParent(this);
+		card.setLocation(0, 0);
+		expandToFit(card);
+	}
+
+	/**
+	 * Adds a card to this panel and resizes it.
+	 *
+	 * @param card   the added card
+	 * @param width  the new width
+	 * @param height the new height
+	 */
+	public void add(WWidget card, int width, int height) {
+		add(cards.size(), card, width, height);
+	}
+
+	/**
+	 * Adds a card to this panel and resizes it.
+	 *
+	 * @param index  the index of the card
+	 * @param card   the added card
+	 * @param width  the new width
+	 * @param height the new height
+	 */
+	public void add(int index, WWidget card, int width, int height) {
+		if (card.canResize()) {
+			card.setSize(width, height);
+		}
+
+		add(index, card);
+	}
+
+	/**
+	 * Gets the index of the selected card in this panel.
+	 *
+	 * @return the selected card's index
+	 */
+	public int getSelectedIndex() {
+		return selectedIndex;
+	}
+
+	/**
+	 * Sets the selected index of this panel.
+	 *
+	 * @param selectedIndex the new selected index
+	 * @return this panel
+	 * @throws IndexOutOfBoundsException if this panel does not contain the card index
+	 */
+	public WCardPanel setSelectedIndex(int selectedIndex) {
+		if (selectedIndex < 0 || selectedIndex >= cards.size()) {
+			throw new IndexOutOfBoundsException("Card index " + selectedIndex + " out of bounds: 0 <= index <" + cards.size());
+		}
+
+		if (this.selectedIndex != selectedIndex) {
+			this.selectedIndex = selectedIndex;
+			layout();
+		}
+
+		return this;
+	}
+
+	/**
+	 * Gets the selected card of this panel.
+	 *
+	 * @return the selected card
+	 */
+	public WWidget getSelectedCard() {
+		return cards.get(getSelectedIndex());
+	}
+
+	/**
+	 * Sets the selected card of this panel.
+	 *
+	 * @param selectedCard the new selected card
+	 * @return this panel
+	 * @throws NoSuchElementException if this panel does not contain the card
+	 */
+	public WCardPanel setSelectedCard(WWidget selectedCard) {
+		if (!cards.contains(selectedCard)) {
+			throw new NoSuchElementException("Widget " + selectedCard + " is not a card in this panel!");
+		}
+
+		return setSelectedIndex(cards.indexOf(selectedCard));
+	}
+
+	@Override
+	public void setSize(int x, int y) {
+		super.setSize(x, y);
+		for (WWidget card : cards) {
+			card.setSize(x, y);
+		}
+	}
+
+	@Override
+	public void layout() {
+		children.clear();
+
+		for (WWidget child : cards) {
+			if (child instanceof WPanel) ((WPanel) child).layout();
+			expandToFit(child);
+
+			if (child == getSelectedCard()) {
+				child.onShown();
+			} else {
+				child.onHidden();
+			}
+		}
+
+		for (WWidget child : cards) {
+			child.setSize(getWidth(), getHeight());
+		}
+
+		children.add(getSelectedCard());
+	}
+
+	/**
+	 * {@inheritDoc}
+	 *
+	 * @param c the host GUI description
+	 * @throws IllegalStateException if this panel has no cards
+	 */
+	@Override
+	public void validate(GuiDescription c) {
+		if (cards.isEmpty()) {
+			throw new IllegalStateException("No children in card panel");
+		}
+
+		layout();
+		for (WWidget card : cards) {
+			card.validate(c);
+			if (getSelectedCard() != card) card.onHidden();
+		}
+
+		if (c != null) createPeers(c);
+	}
+
+	@SuppressWarnings("deprecation")
+	@Override
+	public void createPeers(GuiDescription c) {
+		for (WWidget card : cards) {
+			card.createPeers(c);
+		}
+	}
+
+	@Environment(EnvType.CLIENT)
+	@Override
+	public void addPainters() {
+		for (WWidget card : cards) {
+			card.addPainters();
+		}
+	}
+}
diff --git a/src/main/java/io/github/cottonmc/cotton/gui/widget/WItemSlot.java b/src/main/java/io/github/cottonmc/cotton/gui/widget/WItemSlot.java
index 4ef0056..15e6916 100644
--- a/src/main/java/io/github/cottonmc/cotton/gui/widget/WItemSlot.java
+++ b/src/main/java/io/github/cottonmc/cotton/gui/widget/WItemSlot.java
@@ -61,7 +61,6 @@ public class WItemSlot extends WWidget {
 	private final List<ValidatedSlot> peers = new ArrayList<>();
 	@Nullable
 	@Environment(EnvType.CLIENT)
-	// TODO: Set the background painter to SLOT in a new method that sets a widget's default painter.
 	private BackgroundPainter backgroundPainter = null;
 	private Inventory inventory;
 	private int startIndex = 0;
@@ -328,7 +327,9 @@ public class WItemSlot extends WWidget {
 	@Environment(EnvType.CLIENT)
 	@Override
 	public void paint(MatrixStack matrices, int x, int y, int mouseX, int mouseY) {
-		(backgroundPainter != null ? backgroundPainter : BackgroundPainter.SLOT).paintBackground(x, y, this);
+		if (backgroundPainter != null) {
+			backgroundPainter.paintBackground(x, y, this);
+		}
 	}
 
 	@Nullable
@@ -370,6 +371,28 @@ public class WItemSlot extends WWidget {
 		}
 	}
 
+	@Override
+	public void onShown() {
+		for (ValidatedSlot peer : peers) {
+			peer.setVisible(true);
+		}
+	}
+
+	@Override
+	public void onHidden() {
+		super.onHidden();
+
+		for (ValidatedSlot peer : peers) {
+			peer.setVisible(false);
+		}
+	}
+
+	@Environment(EnvType.CLIENT)
+	@Override
+	public void addPainters() {
+		backgroundPainter = BackgroundPainter.SLOT;
+	}
+
 	/**
 	 * A listener for changes in an item slot.
 	 *
diff --git a/src/main/java/io/github/cottonmc/cotton/gui/widget/WPanel.java b/src/main/java/io/github/cottonmc/cotton/gui/widget/WPanel.java
index 10725ee..7265e8d 100644
--- a/src/main/java/io/github/cottonmc/cotton/gui/widget/WPanel.java
+++ b/src/main/java/io/github/cottonmc/cotton/gui/widget/WPanel.java
@@ -279,7 +279,38 @@ public abstract class WPanel extends WWidget {
 	}
 
 	@Override
+	public void onShown() {
+		for (WWidget child : children) {
+			child.onShown();
+		}
+	}
+
+	@Override
+	public void onHidden() {
+		super.onHidden();
+
+		for (WWidget child : children) {
+			child.onHidden();
+		}
+	}
+
+	/**
+	 * {@inheritDoc}
+	 *
+	 * <p>Subclasses should call {@code super.addPainters()} to ensure that children have proper default painters.
+	 *
+	 * @since 3.0.0
+	 */
+	@Environment(EnvType.CLIENT)
+	@Override
+	public void addPainters() {
+		for (WWidget child : children) {
+			child.addPainters();
+		}
+	}
+
+	@Override
 	public String toString() {
-		return "WPanel{ children: [\n" + children.stream().map(Objects::toString).flatMap(x -> Stream.of(x.split("\n")).map(y -> "\t" + y)).collect(Collectors.joining(",\n")) + "] }";
+		return getClass().getSimpleName() + " {\n" + children.stream().map(Object::toString).map(x -> x + ",").flatMap(x -> Stream.of(x.split("\n")).filter(y -> !y.isEmpty()).map(y -> "\t" + y)).collect(Collectors.joining("\n")) + "\n}";
 	}
 }
diff --git a/src/main/java/io/github/cottonmc/cotton/gui/widget/WTabPanel.java b/src/main/java/io/github/cottonmc/cotton/gui/widget/WTabPanel.java
new file mode 100644
index 0000000..039f2bd
--- /dev/null
+++ b/src/main/java/io/github/cottonmc/cotton/gui/widget/WTabPanel.java
@@ -0,0 +1,370 @@
+package io.github.cottonmc.cotton.gui.widget;
+
+import io.github.cottonmc.cotton.gui.client.BackgroundPainter;
+import io.github.cottonmc.cotton.gui.client.LibGuiClient;
+import io.github.cottonmc.cotton.gui.client.ScreenDrawing;
+import io.github.cottonmc.cotton.gui.widget.data.Axis;
+import io.github.cottonmc.cotton.gui.widget.data.HorizontalAlignment;
+import io.github.cottonmc.cotton.gui.widget.icon.Icon;
+import net.fabricmc.api.EnvType;
+import net.fabricmc.api.Environment;
+import net.minecraft.client.MinecraftClient;
+import net.minecraft.client.font.TextRenderer;
+import net.minecraft.client.sound.PositionedSoundInstance;
+import net.minecraft.client.util.math.MatrixStack;
+import net.minecraft.sound.SoundEvents;
+import net.minecraft.text.Text;
+import net.minecraft.util.Identifier;
+
+import javax.annotation.Nullable;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+import java.util.Objects;
+import java.util.function.Consumer;
+
+// TODO: Different tab positions
+
+/**
+ * A panel that contains creative inventory-style tabs on the top.
+ *
+ * @since 3.0.0
+ */
+public class WTabPanel extends WPanel {
+	private static final int TAB_PADDING = 4;
+	private static final int TAB_WIDTH = 28;
+	private static final int TAB_HEIGHT = 30;
+	private static final int PANEL_PADDING = 8; // The padding of BackgroundPainter.VANILLA
+	private static final int ICON_SIZE = 16;
+	private final WBox tabRibbon = new WBox(Axis.HORIZONTAL).setSpacing(1);
+	private final List<WTab> tabWidgets = new ArrayList<>();
+	private final WCardPanel mainPanel = new WCardPanel();
+
+	/**
+	 * Constructs a new tab panel.
+	 */
+	public WTabPanel() {
+		add(tabRibbon, 0, 0);
+		add(mainPanel, PANEL_PADDING, TAB_HEIGHT + PANEL_PADDING);
+	}
+
+	private void add(WWidget widget, int x, int y) {
+		children.add(widget);
+		widget.setParent(this);
+		widget.setLocation(x, y);
+		expandToFit(widget);
+	}
+
+	/**
+	 * Adds a tab to this panel.
+	 *
+	 * @param tab the added tab
+	 */
+	public void add(Tab tab) {
+		WTab tabWidget = new WTab(tab);
+
+		if (tabWidgets.isEmpty()) {
+			tabWidget.selected = true;
+		}
+
+		tabWidgets.add(tabWidget);
+		tabRibbon.add(tabWidget, TAB_WIDTH, TAB_HEIGHT + TAB_PADDING);
+		mainPanel.add(tab.getWidget());
+	}
+
+	/**
+	 * Configures and adds a tab to this panel.
+	 *
+	 * @param widget       the contained widget
+	 * @param configurator the tab configurator
+	 */
+	public void add(WWidget widget, Consumer<Tab.Builder> configurator) {
+		Tab.Builder builder = new Tab.Builder(widget);
+		configurator.accept(builder);
+		add(builder.build());
+	}
+
+	@Override
+	public void setSize(int x, int y) {
+		super.setSize(x, y);
+		tabRibbon.setSize(x, TAB_HEIGHT);
+	}
+
+	@Environment(EnvType.CLIENT)
+	@Override
+	public void addPainters() {
+		super.addPainters();
+		mainPanel.setBackgroundPainter(BackgroundPainter.VANILLA);
+	}
+
+	/**
+	 * The data of a tab.
+	 */
+	public static class Tab {
+		@Nullable
+		private final Text title;
+		@Nullable
+		private final Icon icon;
+		private final WWidget widget;
+		private final Consumer<TooltipBuilder> tooltip;
+
+		/**
+		 * Constructs a tab.
+		 *
+		 * @param title   the tab title
+		 * @param icon    the tab icon
+		 * @param widget  the widget contained in the tab
+		 * @param tooltip the tab tooltip
+		 * @throws IllegalArgumentException if both the title and the icon are null
+		 * @throws NullPointerException     if either the widget or the tooltip is null
+		 */
+		public Tab(@Nullable Text title, @Nullable Icon icon, WWidget widget, Consumer<TooltipBuilder> tooltip) {
+			if (title == null && icon == null) {
+				throw new IllegalArgumentException("A tab must have a title or an icon");
+			}
+
+			this.title = title;
+			this.icon = icon;
+			this.widget = Objects.requireNonNull(widget, "widget");
+			this.tooltip = Objects.requireNonNull(tooltip, "tooltip");
+		}
+
+		/**
+		 * Gets the title of this tab.
+		 *
+		 * @return the title, or null if there's no title
+		 */
+		@Nullable
+		public Text getTitle() {
+			return title;
+		}
+
+		/**
+		 * Gets the icon of this tab.
+		 *
+		 * @return the icon, or null if there's no title
+		 */
+		@Nullable
+		public Icon getIcon() {
+			return icon;
+		}
+
+		/**
+		 * Gets the contained widget of this tab.
+		 *
+		 * @return the contained widget
+		 */
+		public WWidget getWidget() {
+			return widget;
+		}
+
+		/**
+		 * Adds this widget's tooltip to the {@code tooltip} builder.
+		 *
+		 * @param tooltip the tooltip builder
+		 */
+		public void addTooltip(TooltipBuilder tooltip) {
+			this.tooltip.accept(tooltip);
+		}
+
+		/**
+		 * A builder for tab data.
+		 */
+		public static final class Builder {
+			@Nullable
+			private Text title;
+			@Nullable
+			private Icon icon;
+			private final WWidget widget;
+			private final List<Consumer<TooltipBuilder>> tooltip = new ArrayList<>();
+			private static final Consumer<TooltipBuilder> DEFAULT_TOOLTIP = builder -> {};
+
+			/**
+			 * Constructs a new tab data builder.
+			 *
+			 * @param widget the contained widget
+			 * @throws NullPointerException if the widget is null
+			 */
+			public Builder(WWidget widget) {
+				this.widget = Objects.requireNonNull(widget, "widget");
+			}
+
+			/**
+			 * Sets the tab title.
+			 *
+			 * @param title the new title
+			 * @return this builder
+			 * @throws NullPointerException if the title is null
+			 */
+			public Builder title(Text title) {
+				this.title = Objects.requireNonNull(title, "title");
+				return this;
+			}
+
+			/**
+			 * Sets the tab icon.
+			 *
+			 * @param icon the new icon
+			 * @return this builder
+			 * @throws NullPointerException if the icon is null
+			 */
+			public Builder icon(Icon icon) {
+				this.icon = Objects.requireNonNull(icon, "icon");
+				return this;
+			}
+
+			/**
+			 * Adds lines to the tab's tooltip.
+			 *
+			 * @param lines the added lines
+			 * @return this builder
+			 * @throws NullPointerException if the line array is null
+			 */
+			public Builder tooltip(Text... lines) {
+				Objects.requireNonNull(lines, "lines");
+				tooltip.add(builder -> builder.add(lines));
+
+				return this;
+			}
+
+			/**
+			 * Adds lines to the tab's tooltip.
+			 *
+			 * @param lines the added lines
+			 * @return this builder
+			 * @throws NullPointerException if the line collection is null
+			 */
+			public Builder tooltip(Collection<? extends Text> lines) {
+				Objects.requireNonNull(lines, "lines");
+				tooltip.add(builder -> builder.add(lines.toArray(new Text[0])));
+				return this;
+			}
+
+			/**
+			 * Builds a tab from this builder.
+			 *
+			 * @return the built tab
+			 * @see Tab#Tab(Text, Icon, WWidget, Consumer)
+			 */
+			public Tab build() {
+				Consumer<TooltipBuilder> tooltip = DEFAULT_TOOLTIP;
+
+				if (!this.tooltip.isEmpty()) {
+					tooltip = builder -> {
+						for (Consumer<TooltipBuilder> entry : this.tooltip) {
+							entry.accept(builder);
+						}
+					};
+				}
+
+				return new Tab(title, icon, widget, tooltip);
+			}
+		}
+	}
+
+	private final class WTab extends WWidget {
+		private final Tab data;
+		boolean selected = false;
+
+		WTab(Tab data) {
+			this.data = data;
+		}
+
+		@Override
+		public boolean canFocus() {
+			return true;
+		}
+
+		@Environment(EnvType.CLIENT)
+		@Override
+		public void onClick(int x, int y, int button) {
+			super.onClick(x, y, button);
+
+			MinecraftClient.getInstance().getSoundManager().play(PositionedSoundInstance.master(SoundEvents.UI_BUTTON_CLICK, 1.0F));
+
+			for (WTab tab : tabWidgets) {
+				tab.selected = (tab == this);
+			}
+
+			mainPanel.setSelectedCard(data.getWidget());
+			WTabPanel.this.layout();
+		}
+
+		@Environment(EnvType.CLIENT)
+		@Override
+		public void onKeyPressed(int ch, int key, int modifiers) {
+			if (isActivationKey(ch)) {
+				onClick(0, 0, 0);
+			}
+		}
+
+		@Environment(EnvType.CLIENT)
+		@Override
+		public void paint(MatrixStack matrices, int x, int y, int mouseX, int mouseY) {
+			TextRenderer renderer = MinecraftClient.getInstance().textRenderer;
+			Text title = data.getTitle();
+			Icon icon = data.getIcon();
+
+			if (title != null) {
+				int width = TAB_WIDTH + renderer.getWidth(title);
+				if (icon == null) width = Math.max(TAB_WIDTH, width - ICON_SIZE);
+
+				if (this.width != width) {
+					setSize(width, this.height);
+					getParent().layout();
+				}
+			}
+
+			(selected ? Painters.SELECTED_TAB : Painters.UNSELECTED_TAB).paintBackground(x, y, this);
+			if (isFocused()) {
+				(selected ? Painters.SELECTED_TAB_FOCUS_BORDER : Painters.UNSELECTED_TAB_FOCUS_BORDER).paintBackground(x, y, this);
+			}
+
+			int iconX = 6;
+
+			if (title != null) {
+				int titleX = (icon != null) ? iconX + ICON_SIZE + 1 : 0;
+				int titleY = (height - TAB_PADDING - renderer.fontHeight) / 2 + 1;
+				int width = (icon != null) ? this.width - iconX - ICON_SIZE : this.width;
+				HorizontalAlignment align = (icon != null) ? HorizontalAlignment.LEFT : HorizontalAlignment.CENTER;
+
+				int color;
+				if (LibGuiClient.config.darkMode) {
+					color = WLabel.DEFAULT_DARKMODE_TEXT_COLOR;
+				} else {
+					color = selected ? WLabel.DEFAULT_TEXT_COLOR : 0xEEEEEE;
+				}
+
+				ScreenDrawing.drawString(matrices, title.asOrderedText(), align, x + titleX, y + titleY, width, color);
+			}
+
+			if (icon != null) {
+				icon.paint(matrices, x + iconX, y + (height - TAB_PADDING - ICON_SIZE) / 2, ICON_SIZE);
+			}
+		}
+
+		@Override
+		public void addTooltip(TooltipBuilder tooltip) {
+			data.addTooltip(tooltip);
+		}
+	}
+
+	/**
+	 * Internal background painter instances for tabs.
+	 */
+	@Environment(EnvType.CLIENT)
+	final static class Painters {
+		static final BackgroundPainter SELECTED_TAB = BackgroundPainter.createLightDarkVariants(
+				BackgroundPainter.createNinePatch(new Identifier("libgui", "textures/widget/tab/selected_light.png")).setTopPadding(2),
+				BackgroundPainter.createNinePatch(new Identifier("libgui", "textures/widget/tab/selected_dark.png")).setTopPadding(2)
+		);
+
+		static final BackgroundPainter UNSELECTED_TAB = BackgroundPainter.createLightDarkVariants(
+				BackgroundPainter.createNinePatch(new Identifier("libgui", "textures/widget/tab/unselected_light.png")),
+				BackgroundPainter.createNinePatch(new Identifier("libgui", "textures/widget/tab/unselected_dark.png"))
+		);
+
+		static final BackgroundPainter SELECTED_TAB_FOCUS_BORDER = BackgroundPainter.createNinePatch(new Identifier("libgui", "textures/widget/tab/focus.png")).setTopPadding(2);
+		static final BackgroundPainter UNSELECTED_TAB_FOCUS_BORDER = BackgroundPainter.createNinePatch(new Identifier("libgui", "textures/widget/tab/focus.png"));
+	}
+}
diff --git a/src/main/java/io/github/cottonmc/cotton/gui/widget/WWidget.java b/src/main/java/io/github/cottonmc/cotton/gui/widget/WWidget.java
index 789560a..ee9c1e7 100644
--- a/src/main/java/io/github/cottonmc/cotton/gui/widget/WWidget.java
+++ b/src/main/java/io/github/cottonmc/cotton/gui/widget/WWidget.java
@@ -3,6 +3,7 @@ package io.github.cottonmc.cotton.gui.widget;
 import java.util.ArrayList;
 import java.util.List;
 
+import com.google.common.annotations.Beta;
 import io.github.cottonmc.cotton.gui.GuiDescription;
 import net.fabricmc.api.EnvType;
 import net.fabricmc.api.Environment;
@@ -372,7 +373,11 @@ public class WWidget {
 	 * @param host the host GUI description
 	 */
 	public void validate(GuiDescription host) {
-		this.host = host;
+		if (host != null) {
+			this.host = host;
+		} else {
+			LOGGER.warn("Validating {} with a null host", this);
+		}
 	}
 
 	/**
@@ -435,6 +440,42 @@ public class WWidget {
 	}
 
 	/**
+	 * Notifies this widget that it is visible and
+	 * shows any hidden peers of itself and its children.
+	 *
+	 * @since 3.0.0
+	 */
+	@Beta
+	public void onShown() {
+	}
+
+	/**
+	 * Notifies this widget that it won't be drawn and
+	 * hides any visible peers of itself and its children.
+	 *
+	 * <p>The default implementation releases this widget's
+	 * focus if it is focused. Overriding implementations
+	 * might want to do this as well.
+	 *
+	 * @since 3.0.0
+	 */
+	@Beta
+	public void onHidden() {
+		releaseFocus();
+	}
+
+	/**
+	 * Adds the default background painters to this widget and all children.
+	 *
+	 * <p>Always called before {@link GuiDescription#addPainters()} to allow users to modify painters.
+	 *
+	 * @since 3.0.0
+	 */
+	@Environment(EnvType.CLIENT)
+	public void addPainters() {
+	}
+
+	/**
 	 * Tests if the provided key code is an activation key for widgets.
 	 *
 	 * <p>The activation keys are Enter, keypad Enter, and Space.
diff --git a/src/main/resources/assets/libgui/textures/widget/tab/focus.png b/src/main/resources/assets/libgui/textures/widget/tab/focus.png
new file mode 100644
index 0000000..6d25685
--- /dev/null
+++ b/src/main/resources/assets/libgui/textures/widget/tab/focus.png
diff --git a/src/main/resources/assets/libgui/textures/widget/tab/selected_dark.png b/src/main/resources/assets/libgui/textures/widget/tab/selected_dark.png
new file mode 100644
index 0000000..24ba766
--- /dev/null
+++ b/src/main/resources/assets/libgui/textures/widget/tab/selected_dark.png
diff --git a/src/main/resources/assets/libgui/textures/widget/tab/selected_light.png b/src/main/resources/assets/libgui/textures/widget/tab/selected_light.png
new file mode 100644
index 0000000..ce7cbf2
--- /dev/null
+++ b/src/main/resources/assets/libgui/textures/widget/tab/selected_light.png
diff --git a/src/main/resources/assets/libgui/textures/widget/tab/unselected_dark.png b/src/main/resources/assets/libgui/textures/widget/tab/unselected_dark.png
new file mode 100644
index 0000000..ae1d16e
--- /dev/null
+++ b/src/main/resources/assets/libgui/textures/widget/tab/unselected_dark.png
diff --git a/src/main/resources/assets/libgui/textures/widget/tab/unselected_light.png b/src/main/resources/assets/libgui/textures/widget/tab/unselected_light.png
new file mode 100644
index 0000000..21ab044
--- /dev/null
+++ b/src/main/resources/assets/libgui/textures/widget/tab/unselected_light.png
diff --git a/src/main/resources/fabric.mod.json b/src/main/resources/fabric.mod.json
index 22d9990..df75753 100644
--- a/src/main/resources/fabric.mod.json
+++ b/src/main/resources/fabric.mod.json
@@ -21,6 +21,9 @@
 		"client": ["io.github.cottonmc.cotton.gui.client.LibGuiClient"],
 		"modmenu": ["io.github.cottonmc.cotton.gui.client.modmenu.ModMenuSupport"]
 	},
+	"mixins": [
+		"mixins.libgui.accessors.json"
+	],
 	"depends": {
 		"fabricloader": ">=0.8.8",
 		"fabric": "*",
diff --git a/src/main/resources/mixins.libgui.accessors.json b/src/main/resources/mixins.libgui.accessors.json
new file mode 100644
index 0000000..9ec55f2
--- /dev/null
+++ b/src/main/resources/mixins.libgui.accessors.json
@@ -0,0 +1,14 @@
+{
+	"compatibilityLevel": "JAVA_8",
+	"minVersion": "0.7.11",
+	"package": "io.github.cottonmc.cotton.gui.impl.access",
+	"required": true,
+
+	"mixins": [
+		"SlotAccessor"
+	],
+
+	"injectors": {
+		"defaultRequire": 1
+	}
+}