feat: Added a Clear button to the Arcane Workbench. Clicking it removes all spell bindings of the item in the center slot

src/main/java/electroblob/wizardry/client/gui/GuiArcaneWorkbench.java

@@ -93,6 +93,7 @@ public class GuiArcaneWorkbench extends GuiContainer {
 	private ContainerArcaneWorkbench arcaneWorkbenchContainer;
 
 	private GuiButton applyBtn;
+	private GuiButton clearBtn;
 	private GuiButton[] sortButtons = new GuiButton[3];
 
 	private GuiTextField searchField;
@@ -126,6 +127,7 @@ public class GuiArcaneWorkbench extends GuiContainer {
 
 		this.buttonList.clear();
 		this.buttonList.add(this.applyBtn = new GuiButtonApply(0, this.width / 2 + 64, this.height / 2 + 3));
+		this.buttonList.add(this.clearBtn = new GuiButtonClear(0, this.width / 2 + 64, this.height / 2 - 16));
 		this.buttonList.add(sortButtons[0] = new GuiButtonSpellSort(1, this.guiLeft - 44, this.guiTop + 8, ISpellSortable.SortType.TIER, arcaneWorkbenchContainer, this));
 		this.buttonList.add(sortButtons[1] = new GuiButtonSpellSort(2, this.guiLeft - 31, this.guiTop + 8, ISpellSortable.SortType.ELEMENT, arcaneWorkbenchContainer, this));
 		this.buttonList.add(sortButtons[2] = new GuiButtonSpellSort(3, this.guiLeft - 18, this.guiTop + 8, ISpellSortable.SortType.ALPHABETICAL, arcaneWorkbenchContainer, this));
@@ -205,6 +207,7 @@ public class GuiArcaneWorkbench extends GuiContainer {
 
 		// Show/hide the relevant gui elements
 		this.applyBtn.enabled = centreSlot.getHasStack();
+		this.clearBtn.enabled = centreSlot.getHasStack() && centreSlot.getStack().getItem() instanceof IWorkbenchItem && ((IWorkbenchItem) centreSlot.getStack().getItem()).isClearable();
 		for(GuiButton button : this.sortButtons) button.visible = arcaneWorkbenchContainer.hasBookshelves();
 		this.searchField.setVisible(arcaneWorkbenchContainer.hasBookshelves());
 
@@ -444,6 +447,17 @@ public class GuiArcaneWorkbench extends GuiContainer {
 				animationTimer = 20;
 			}
 
+			if(button == clearBtn){
+				// Packet building
+				IMessage msg = new PacketControlInput.Message(PacketControlInput.ControlType.CLEAR_BUTTON);
+				WizardryPacketHandler.net.sendToServer(msg);
+				// Sound
+				Minecraft.getMinecraft().getSoundHandler().playSound(PositionedSoundRecord.getMasterRecord(
+						WizardrySounds.BLOCK_ARCANE_WORKBENCH_SPELLBIND, 0.8f));
+				// Animation
+				animationTimer = 20;
+			}
+
 			if(button instanceof GuiButtonSpellSort) this.arcaneWorkbenchContainer.setSortType(((GuiButtonSpellSort)button).sortType);
 		}
 	}
@@ -1006,4 +1020,36 @@ public class GuiArcaneWorkbench extends GuiContainer {
 		}
 	}
 
+	private static class GuiButtonClear extends GuiButton {
+
+		public GuiButtonClear(int id, int x, int y){
+			super(id, x, y, 16, 16, I18n.format("container." + Wizardry.MODID + ":arcane_workbench.clear"));
+		}
+
+		@Override
+		public void drawButton(Minecraft minecraft, int mouseX, int mouseY, float partialTicks){
+
+			// Whether the button is highlighted
+			this.hovered = mouseX >= this.x && mouseY >= this.y && mouseX < this.x + this.width && mouseY < this.y + this.height;
+
+			int k = 72;
+			int l = 236;
+			//int colour = 14737632;
+
+			if(this.enabled){
+				if(this.hovered){
+					k += this.width * 2;
+					//colour = 16777120;
+				}
+			}else{
+				k += this.width;
+				//colour = 10526880;
+			}
+
+			DrawingUtils.drawTexturedRect(this.x, this.y, k, l, this.width, this.height, TEXTURE_WIDTH, TEXTURE_HEIGHT);
+			//this.drawCenteredString(minecraft.fontRenderer, this.displayString, this.x + this.width / 2,
+			//		this.y + (this.height - 8) / 2, colour);
+		}
+	}
+
 }

src/main/java/electroblob/wizardry/inventory/ContainerArcaneWorkbench.java

@@ -452,6 +452,24 @@ public class ContainerArcaneWorkbench extends Container implements ISpellSortabl
 		}
 	}
 
+	/**
+	 * Called (via {@link electroblob.wizardry.packet.PacketControlInput PacketControlInput}) when the clear button in
+	 * the arcane workbench GUI is pressed.
+	 */
+	// As of 2.1, for the sake of events and neatness of code, this was moved here from TileEntityArcaneWorkbench.
+	// As of 4.2, the spell binding/charging/upgrading code was delegated (via IWorkbenchItem) to the items themselves.
+	public void onClearButtonPressed(EntityPlayer player){
+
+		Slot centre = this.getSlot(CENTRE_SLOT);
+
+		if(centre.getStack().getItem() instanceof IWorkbenchItem){ // Should always be true, but no harm in checking.
+
+			Slot[] spellBooks = this.inventorySlots.subList(0, 8).toArray(new Slot[8]);
+
+			((IWorkbenchItem) centre.getStack().getItem()).onClearButtonPressed(player, centre, this.getSlot(CRYSTAL_SLOT), this.getSlot(UPGRADE_SLOT), spellBooks);
+		}
+	}
+
 	/** Scrolls to the given row number. */
 	public void scrollTo(int row){
 		this.scroll = row;

src/main/java/electroblob/wizardry/item/IWorkbenchItem.java

@@ -55,6 +55,26 @@ public interface IWorkbenchItem {
 	 */
 	boolean onApplyButtonPressed(EntityPlayer player, Slot centre, Slot crystals, Slot upgrade, Slot[] spellBooks);
 
+	/**
+	 * Called when this item is in the central slot of an arcane workbench and the apply clear is pressed. Items must
+	 * implement this method to define what happens when the apply button is pressed.
+	 * @param player The player that pressed the apply button.
+	 * @param centre The central slot in the arcane workbench. This slot will always contain a stack of the implementing
+	 * item, or in other words, <i>it is guaranteed that</i> {@code this == centre.getStack().getItem()}.
+	 * @param crystals The magic crystal slot of the arcane workbench.
+	 * @param upgrade The upgrade slot of the arcane workbench.
+	 * @param spellBooks An array of the <i>active</i> (visible) spell book slots in the arcane workbench. The length of
+	 * the array will be equal to the value returned by {@link IWorkbenchItem#getSpellSlotCount(ItemStack)}.
+	 * */
+	default void onClearButtonPressed(EntityPlayer player, Slot centre, Slot crystals, Slot upgrade, Slot[] spellBooks){};
+
+	/**
+	 * Must be overridden in the item class to make the clear button in the Arcane Workbench clickable.
+	 * */
+	default boolean isClearable() {
+		return false;
+	}
+
 	/**
 	 * Returns whether the tooltip (dark grey box) should be drawn when this item is in an arcane workbench. Only
 	 * called client-side.

src/main/java/electroblob/wizardry/item/ItemWand.java

@@ -28,6 +28,7 @@ import net.minecraft.inventory.Slot;
 import net.minecraft.item.EnumAction;
 import net.minecraft.item.Item;
 import net.minecraft.item.ItemStack;
+import net.minecraft.nbt.NBTTagCompound;
 import net.minecraft.util.*;
 import net.minecraft.util.math.BlockPos;
 import net.minecraft.util.math.RayTraceResult;
@@ -881,6 +882,19 @@ public class ItemWand extends Item implements IWorkbenchItem, ISpellCastingItem,
 		return changed;
 	}
 
+	@Override
+	public void onClearButtonPressed(EntityPlayer player, Slot centre, Slot crystals, Slot upgrade, Slot[] spellBooks){
+		ItemStack stack = centre.getStack();
+		if (stack.hasTagCompound() && stack.getTagCompound().hasKey(WandHelper.SPELL_ARRAY_KEY)) {
+			NBTTagCompound nbt = stack.getTagCompound();
+			nbt.removeTag(WandHelper.SPELL_ARRAY_KEY);
+			stack.setTagCompound(nbt);
+		}
+	}
+
+	@Override
+	public boolean isClearable() { return true; }
+
 	// hitEntity is only called server-side, so we'll have to use events
 	@SubscribeEvent
 	public static void onAttackEntityEvent(AttackEntityEvent event){

src/main/java/electroblob/wizardry/packet/PacketControlInput.java

@@ -51,6 +51,17 @@ public class PacketControlInput implements IMessageHandler<Message, IMessage> {
 
 					break;
 
+				case CLEAR_BUTTON:
+
+					if(!(player.openContainer instanceof ContainerArcaneWorkbench)){
+						Wizardry.logger.warn("Received a PacketControlInput, but the player that sent it was not " +
+								"currently using an arcane workbench. This should not happen!");
+					}else{
+						((ContainerArcaneWorkbench)player.openContainer).onClearButtonPressed(player);
+					}
+
+					break;
+
 				case NEXT_SPELL_KEY:
 
 					if(wand.getItem() instanceof ISpellCastingItem){
@@ -133,7 +144,7 @@ public class PacketControlInput implements IMessageHandler<Message, IMessage> {
 	}
 
 	public enum ControlType {
-		APPLY_BUTTON, NEXT_SPELL_KEY, PREVIOUS_SPELL_KEY, RESURRECT_BUTTON, CANCEL_RESURRECT, POSSESSION_PROJECTILE
+		APPLY_BUTTON, NEXT_SPELL_KEY, PREVIOUS_SPELL_KEY, RESURRECT_BUTTON, CANCEL_RESURRECT, POSSESSION_PROJECTILE, CLEAR_BUTTON
 	}
 
 	public static class Message implements IMessage {