Support swap item between main hand and offhand by press key "F" (#4241)

Hi,

I found cuberite don't support to press key "F" to swap items on main hand and offhand, so I implemented this feature.

Best regards
Changyong

CONTRIBUTORS

@@ -13,6 +13,7 @@ beeduck
 bibo38
 birkett (Anthony Birkett)
 Bond_009
+changyongGuo
 Cocosushi6
 derouinw
 Diusrex

Server/Plugins/APIDump/APIDesc.lua

@@ -3317,6 +3317,16 @@ local Hash = cCryptoHash.sha1HexString("DataToHash")
 					},
 					Notes = "Returns the weapon that the entity has equipped. Returns an empty cItem if no weapon equipped or not applicable.",
 				},
+				GetOffHandEquipedItem =
+				{
+					Returns =
+					{
+						{
+							Type = "cItem",
+						},
+					},
+					Notes = "Returns the item that the entity has equipped on off-hand. Returns an empty cItem if no item equipped or not applicable.",
+				},
 				GetGravity =
 				{
 					Returns =

src/ClientHandle.cpp

@@ -1188,7 +1188,14 @@ void cClientHandle::HandleLeftClick(int a_BlockX, int a_BlockY, int a_BlockZ, eB
 
 		case DIG_STATUS_SWAP_ITEM_IN_HAND:
 		{
-			// TODO: Not yet implemented
+
+			cItem EquippedItem = m_Player->GetEquippedItem();
+			cItem OffhandItem = m_Player->GetOffHandEquipedItem();
+
+			cInventory & Intentory = m_Player->GetInventory();
+			Intentory.SetShieldSlot(EquippedItem);
+			Intentory.SetHotbarSlot(Intentory.GetEquippedSlotNum(), OffhandItem);
+
 			return;
 		}
 

src/Entities/Entity.h

@@ -351,6 +351,9 @@ public:
 	/** Returns the currently equipped boots; empty item if none */
 	virtual cItem GetEquippedBoots(void) const { return cItem(); }
 
+	/** Returns the currently offhand equipped item; empty item if none */
+	virtual cItem GetOffHandEquipedItem(void) const { return cItem(); }
+
 	/** Applies damage to the armor after the armor blocked the given amount */
 	virtual void ApplyArmorDamage(int DamageBlocked);
 

src/Entities/Player.h

@@ -71,6 +71,9 @@ public:
 	/** Returns the currently equipped boots; empty item if none */
 	virtual cItem GetEquippedBoots(void) const override { return m_Inventory.GetEquippedBoots(); }
 
+	/** Returns the currently offhand equipped item; empty item if none */
+	virtual cItem GetOffHandEquipedItem(void) const override { return m_Inventory.GetShieldSlot(); }
+
 	virtual void ApplyArmorDamage(int DamageBlocked) override;
 
 	// tolua_begin