Adds a config for slave teleporting to master (#5095)

* Fixes #5003.
* Adds a battle config to toggle the ability for slaves to teleport back to their master when they are too far away.
* Officially, players can drag slaves away from the master without them teleporting back.
* Determined that slaves don't become completely stuck but rather immobile until a target comes in range again.
Thanks to @poporing and @Daegaladh!

conf/battle/monster.conf

@@ -280,3 +280,7 @@ boss_nopc_move_rate: 100
 // When killing a monster, do AG_BATTLE type achievements trigger for everyone in the same party within the area?
 // Area is limited to area_size battle config.
 achievement_mob_share: no
+
+// Should slaves teleport back to their master if they get too far during chase? (Note 1)
+// Default (Official): no
+slave_stick_with_master: no

src/map/battle.cpp

@@ -8952,6 +8952,7 @@ static const struct _battle_data {
 	{ "ping_time",                          &battle_config.ping_time,                       20,     0,      99999999,       },
 	{ "show_skill_scale",                   &battle_config.show_skill_scale,                1,      0,      1,              },
 	{ "achievement_mob_share",              &battle_config.achievement_mob_share,           0,      0,      1,              },
+	{ "slave_stick_with_master",            &battle_config.slave_stick_with_master,         0,      0,      1,              },
 
 #include "../custom/battle_config_init.inc"
 };

src/map/battle.hpp

@@ -682,6 +682,7 @@ struct Battle_Config
 	int ping_time;
 	int show_skill_scale;
 	int achievement_mob_share;
+	int slave_stick_with_master;
 
 #include "../custom/battle_config_struct.inc"
 };

src/map/mob.cpp

@@ -1437,34 +1437,36 @@ static int mob_ai_sub_hard_slavemob(struct mob_data *md,t_tick tick)
 
 	if(status_has_mode(&md->status,MD_CANMOVE))
 	{	//If the mob can move, follow around. [Check by Skotlex]
-		int old_dist;
+		int old_dist = md->master_dist;
 
 		// Distance with between slave and master is measured.
-		old_dist=md->master_dist;
-		md->master_dist=distance_bl(&md->bl, bl);
-
-		// Since the master was in near immediately before, teleport is carried out and it pursues.
-		if(bl->m != md->bl.m ||
-			(old_dist<10 && md->master_dist>18) ||
-			md->master_dist > MAX_MINCHASE
-		){
-			md->master_dist = 0;
-			unit_warp(&md->bl,bl->m,bl->x,bl->y,CLR_TELEPORT);
-			return 1;
+		md->master_dist = distance_bl(&md->bl, bl);
+
+		if (battle_config.slave_stick_with_master) {
+			// Since the master was in near immediately before, teleport is carried out and it pursues.
+			if (bl->m != md->bl.m || (old_dist < 10 && md->master_dist > 18) || md->master_dist > MAX_MINCHASE) {
+				md->master_dist = 0;
+				unit_warp(&md->bl, bl->m, bl->x, bl->y, CLR_TELEPORT);
+				return 1;
+			}
 		}
 
 		if(md->target_id) //Slave is busy with a target.
 			return 0;
 
 		// Approach master if within view range, chase back to Master's area also if standing on top of the master.
-		if((md->master_dist>MOB_SLAVEDISTANCE || md->master_dist == 0) &&
-			unit_can_move(&md->bl))
-		{
-			short x = bl->x, y = bl->y;
-			mob_stop_attack(md);
-			if(map_search_freecell(&md->bl, bl->m, &x, &y, MOB_SLAVEDISTANCE, MOB_SLAVEDISTANCE, 1)
-				&& unit_walktoxy(&md->bl, x, y, 0))
-				return 1;
+		if ((md->master_dist > MOB_SLAVEDISTANCE || md->master_dist == 0) && unit_can_move(&md->bl)) {
+			int16 x = bl->x, y = bl->y;
+
+			if (map_search_freecell(&md->bl, bl->m, &x, &y, MOB_SLAVEDISTANCE, MOB_SLAVEDISTANCE, 1)) {
+				if (unit_walktoxy(&md->bl, x, y, 0) == 0) { // Slave is too far from master (outside of battle_config.max_walk_path range), stay put
+					mob_stop_walking(md, USW_FIXPOS);
+					return 0; // Fail here so target will be picked back up when in range
+				} else { // Slave will walk back to master if in range
+					mob_stop_attack(md);
+					return 1;
+				}
+			}
 		}
 	} else if (bl->m != md->bl.m && map_flag_gvg2(md->bl.m)) {
 		//Delete the summoned mob if it's in a gvg ground and the master is elsewhere. [Skotlex]
@@ -1803,9 +1805,14 @@ static bool mob_ai_sub_hard(struct mob_data *md, t_tick tick)
 		md->attacked_id = md->norm_attacked_id = 0;
 	}
 
+	bool slave_lost_target = false;
+
 	// Processing of slave monster
-	if (md->master_id > 0 && mob_ai_sub_hard_slavemob(md, tick))
-		return true;
+	if (md->master_id > 0) {
+		if (mob_ai_sub_hard_slavemob(md, tick) == 1)
+			return true;
+		slave_lost_target = true;
+	}
 
 	// Scan area for targets
 	if (!tbl && can_move && mode&MD_LOOTER && md->lootitems && DIFF_TICK(tick, md->ud.canact_tick) > 0 &&
@@ -1814,7 +1821,7 @@ static bool mob_ai_sub_hard(struct mob_data *md, t_tick tick)
 		map_foreachinshootrange (mob_ai_sub_hard_lootsearch, &md->bl, view_range, BL_ITEM, md, &tbl);
 	}
 
-	if ((!tbl && mode&MD_AGGRESSIVE) || md->state.skillstate == MSS_FOLLOW)
+	if ((!tbl && mode&MD_AGGRESSIVE) || md->state.skillstate == MSS_FOLLOW || slave_lost_target)
 	{
 		map_foreachinallrange (mob_ai_sub_hard_activesearch, &md->bl, view_range, DEFAULT_ENEMY_TYPE(md), md, &tbl, mode);
 	}