Add ghost item icons

Closes #228.

src/main/java/io/github/cottonmc/cotton/gui/widget/icon/ItemIcon.java

@@ -3,6 +3,7 @@
 import net.fabricmc.api.EnvType;
 import net.fabricmc.api.Environment;
 import net.minecraft.client.gui.DrawContext;
+import net.minecraft.client.render.RenderLayer;
 import net.minecraft.client.util.math.MatrixStack;
 import net.minecraft.item.Item;
 import net.minecraft.item.ItemStack;
@@ -15,7 +16,11 @@
  * @since 2.2.0
  */
 public class ItemIcon implements Icon {
+	// Matches the vanilla RecipeBookGhostSlots class (1.20.2).
+	private static final int GHOST_OVERLAY_COLOR = 0x30_FFFFFF;
+
 	private final ItemStack stack;
+	private boolean ghost = false;
 
 	/**
 	 * Constructs an item icon.
@@ -47,6 +52,34 @@ public void paint(DrawContext context, int x, int y, int size) {
 		matrices.translate(x, y, 0);
 		matrices.scale(scale, scale, 1);
 		context.drawItemWithoutEntity(stack, 0, 0);
+
+		if (isGhost()) {
+			context.fill(RenderLayer.getGuiGhostRecipeOverlay(), 0, 0, 16, 16, GHOST_OVERLAY_COLOR);
+		}
+
 		matrices.pop();
 	}
+
+	/**
+	 * Checks whether this icon is a ghost item.
+	 * Ghost items are rendered with a pale overlay.
+	 *
+	 * @return {@code true} if this icon is a ghost item, {@code false} otherwise
+	 * @since 9.2.0
+	 */
+	public boolean isGhost() {
+		return ghost;
+	}
+
+	/**
+	 * Marks this icon as a ghost or non-ghost icon.
+	 *
+	 * @param ghost {@code true} if this icon is a ghost item, {@code false} otherwise
+	 * @return this icon
+	 * @since 9.2.0
+	 */
+	public ItemIcon setGhost(boolean ghost) {
+		this.ghost = ghost;
+		return this;
+	}
 }

src/testMod/java/io/github/cottonmc/test/client/GhostIconTestGui.java

@@ -0,0 +1,26 @@
+package io.github.cottonmc.test.client;
+
+import net.minecraft.item.Items;
+import net.minecraft.text.Text;
+
+import io.github.cottonmc.cotton.gui.client.LightweightGuiDescription;
+import io.github.cottonmc.cotton.gui.widget.WButton;
+import io.github.cottonmc.cotton.gui.widget.WGridPanel;
+import io.github.cottonmc.cotton.gui.widget.WToggleButton;
+import io.github.cottonmc.cotton.gui.widget.icon.ItemIcon;
+
+public class GhostIconTestGui extends LightweightGuiDescription {
+	public GhostIconTestGui() {
+		WGridPanel root = (WGridPanel) rootPanel;
+		root.setGaps(2, 2);
+
+		ItemIcon icon = new ItemIcon(Items.CACTUS);
+		WButton button = new WButton(icon, Text.literal("Hello world"));
+		WToggleButton ghostToggle = new WToggleButton(Text.literal("Ghost"));
+		ghostToggle.setOnToggle(icon::setGhost);
+
+		root.add(button, 0, 0, 5, 1);
+		root.add(ghostToggle, 0, 1, 5, 1);
+		root.validate(this);
+	}
+}

src/testMod/java/io/github/cottonmc/test/client/LibGuiTestClient.java

@@ -71,6 +71,7 @@ public void onInitializeClient() {
 						.then(literal("texture").executes(openScreen(client -> new TextureTestGui())))
 						.then(literal("textalignment").executes(openScreen(client -> new TextAlignmentTestGui())))
 						.then(literal("list").executes(openScreen(client -> new ListTestGui())))
+						.then(literal("ghosticon").executes(openScreen(client -> new GhostIconTestGui())))
 		));
 	}