Fix vending list packet for 2016 clients. Based on rathena commit:

commit 9716233c842f731df3fed5281370e324b5f5f024
Author: Lemongrass3110 <lemongrass@kstp.at>
Date:   Mon May 8 23:40:05 2017 +0200

    Introducing the equip preview window

    Fixes some bugs for 2016-09-21 onward, where you can preview how a item would like if you put it on.
    This works on other people's vending and on your own inventory.

    Thanks to @Rytech2 and @hazimjauhari90

3 files changed, 40 insertions, 2 deletions

diff --git a/src/map/clif.c b/src/map/clif.c
index 7721c4644..ca2a80693 100644
--- a/src/map/clif.c
+++ b/src/map/clif.c
@@ -6351,10 +6351,13 @@ void clif_vendinglist(struct map_session_data* sd, unsigned int id, struct s_ven
 	const int offset = 12;
 #endif
 
-#if PACKETVER >= 20150226
+#if PACKETVER < 20150226
+	const int item_length = 22;
+// [4144] date 20160921 not confirmend. Can be bigger or smaller
+#elif PACKETVER < 20160921
 	const int item_length = 47;
 #else
-	const int item_length = 22;
+	const int item_length = 53;
 #endif
 
 	nullpo_retv(sd);
@@ -6387,6 +6390,11 @@ void clif_vendinglist(struct map_session_data* sd, unsigned int id, struct s_ven
 #if PACKETVER >= 20150226
 		clif->add_item_options(WFIFOP(fd, offset + 22 + i * item_length), &vsd->status.cart[index]);
 #endif
+// [4144] date 20160921 not confirmend. Can be bigger or smaller
+#if PACKETVER >= 20160921
+		WFIFOL(fd, offset + 47 + i * item_length) = pc->item_equippoint(sd, data);
+		WFIFOW(fd, offset + 51 + i * item_length) = data->look;
+#endif
 	}
 	WFIFOSET(fd,WFIFOW(fd,2));
 }
diff --git a/src/map/pc.c b/src/map/pc.c
index 2303a83ca..c52da3c14 100644
--- a/src/map/pc.c
+++ b/src/map/pc.c
@@ -750,6 +750,7 @@ int pc_setnewpc(struct map_session_data *sd, int account_id, int char_id, int lo
 	return 0;
 }
 
+// [4144] probably pc_equippoint should be replaced to pc_item_equippoint
 int pc_equippoint(struct map_session_data *sd,int n)
 {
 	int ep = 0;
@@ -782,6 +783,33 @@ int pc_equippoint(struct map_session_data *sd,int n)
 	return ep;
 }
 
+int pc_item_equippoint(struct map_session_data *sd, struct item_data* id)
+{
+	int ep = 0;
+
+	nullpo_ret(sd);
+	nullpo_ret(id);
+
+	if (!itemdb->isequip2(id))
+		return 0; //Not equippable by players.
+
+	ep = id->equip;
+	if (id->look == W_DAGGER ||
+	    id->look == W_1HSWORD ||
+	    id->look == W_1HAXE) {
+		if (pc->checkskill(sd, AS_LEFT) > 0 ||
+		    (sd->job & MAPID_UPPERMASK) == MAPID_ASSASSIN ||
+		    (sd->job & MAPID_UPPERMASK) == MAPID_KAGEROUOBORO) {
+			// Kagerou and Oboro can dual wield daggers. [Rytech]
+			if (ep == EQP_HAND_R)
+				return EQP_ARMS;
+			if (ep == EQP_SHADOW_WEAPON)
+				return EQP_SHADOW_ARMS;
+		}
+	}
+	return ep;
+}
+
 int pc_setinventorydata(struct map_session_data *sd)
 {
 	int i;
@@ -12044,6 +12072,7 @@ void pc_defaults(void) {
 
 	pc->isequip = pc_isequip;
 	pc->equippoint = pc_equippoint;
+	pc->item_equippoint = pc_item_equippoint;
 	pc->setinventorydata = pc_setinventorydata;
 
 	pc->checkskill = pc_checkskill;
diff --git a/src/map/pc.h b/src/map/pc.h
index af52f8946..634814f07 100644
--- a/src/map/pc.h
+++ b/src/map/pc.h
@@ -859,6 +859,7 @@ END_ZEROED_BLOCK; /* End */
 
 	int (*isequip) (struct map_session_data *sd,int n);
 	int (*equippoint) (struct map_session_data *sd,int n);
+	int (*item_equippoint) (struct map_session_data *sd, struct item_data* id);
 	int (*setinventorydata) (struct map_session_data *sd);
 
 	int (*checkskill) (struct map_session_data *sd,uint16 skill_id);