fix dual fire handling for banks that cannot use it

code/hud/hudtarget.cpp

@@ -6775,10 +6775,9 @@ void HudGaugeWeapons::render(float /*frametime*/, bool config)
 			renderPrintfWithGauge(x + fl2i(Weapon_sunlinked_offset_x * scale), name_y, EG_NULL, scale, config, "%c", Weapon_link_icon);
 
 			// indicate if this is linked
-			// don't draw the link indicator if the fire can't be fired link.
-			// the link flag is ignored rather than cleared so the player can cycle past a no-doublefire weapon without the setting being cleared
-			if (!config && Player_ship->flags[Ship::Ship_Flags::Secondary_dual_fire] && !wip->wi_flags[Weapon::Info_Flags::No_doublefire] &&
-					!The_mission.ai_profile->flags[AI::Profile_Flags::Disable_player_secondary_doublefire] ) {
+			// don't draw the link indicator if this bank can't actually fire linked.
+			// the link flag is ignored rather than cleared so the player can cycle past an incapable bank or weapon without the setting being cleared
+			if (!config && Player_ship->flags[Ship::Ship_Flags::Secondary_dual_fire] && ship_secondary_bank_can_dual_fire(Player_ship, i)) {
 				renderPrintfWithGauge(x + fl2i(Weapon_slinked_offset_x * scale), name_y, EG_NULL, scale, config, "%c", Weapon_link_icon);
 			}
 
@@ -7732,10 +7731,9 @@ void HudGaugeSecondaryWeapons::render(float /*frametime*/, bool config)
 			renderPrintfWithGauge(position[0] + _sunlinked_offset_x, position[1] + text_y_offset, EG_NULL, 1.0f, config, "%c", Weapon_link_icon);
 
 			// indicate if this is linked
-			// don't draw the link indicator if the fire can't be fired link.
-			// the link flag is ignored rather than cleared so the player can cycle past a no-doublefire weapon without the setting being cleared
-			if ( Player_ship->flags[Ship::Ship_Flags::Secondary_dual_fire] && !wip->wi_flags[Weapon::Info_Flags::No_doublefire] &&
-					!The_mission.ai_profile->flags[AI::Profile_Flags::Disable_player_secondary_doublefire] ) {
+			// don't draw the link indicator if this bank can't actually fire linked.
+			// the link flag is ignored rather than cleared so the player can cycle past an incapable bank or weapon without the setting being cleared
+			if ( Player_ship->flags[Ship::Ship_Flags::Secondary_dual_fire] && ship_secondary_bank_can_dual_fire(Player_ship, i) ) {
 				renderPrintfWithGauge(position[0] + _slinked_offset_x, position[1] + text_y_offset, EG_NULL, 1.0f, config, "%c", Weapon_link_icon);
 			}
 
@@ -7945,7 +7943,7 @@ void HudGaugeHardpoints::render(float /*frametime*/, bool config)
 
 					model_render_params weapon_render_info;
 
-					if ( swp->current_secondary_bank == i && ( swp->secondary_next_slot[i] == k || ( swp->secondary_next_slot[i]+1 == k && sp->flags[Ship::Ship_Flags::Secondary_dual_fire] ) ) ) {
+					if ( swp->current_secondary_bank == i && ( swp->secondary_next_slot[i] == k || ( swp->secondary_next_slot[i]+1 == k && sp->flags[Ship::Ship_Flags::Secondary_dual_fire] && ship_secondary_bank_can_dual_fire(sp, i) ) ) ) {
 						weapon_render_info.set_color(Color_bright_blue);
 					} else {
 						weapon_render_info.set_color(Color_bright_white);

code/io/keycontrol.cpp

@@ -1931,19 +1931,22 @@ int button_function_critical(int n, net_player *p = NULL)
 				break;
 			}
 
-			polymodel *pm = model_get(Ship_info[Ships[objp->instance].ship_info_index].model_num);
-
-			int firepoints = pm->missile_banks[Ships[objp->instance].weapons.current_secondary_bank].num_slots;
-
-            if (Ships[objp->instance].flags[Ship::Ship_Flags::Secondary_dual_fire] || firepoints < 2) {
-                Ships[objp->instance].flags.remove(Ship::Ship_Flags::Secondary_dual_fire);
+			if (!ship_secondary_bank_can_dual_fire(&Ships[objp->instance], Ships[objp->instance].weapons.current_secondary_bank)) {
+				// leave the dual fire preference alone; it is ignored rather than cleared for banks that can't use it
+				if(at_self) {
+					HUD_sourced_printf(HUD_SOURCE_HIDDEN, "%s", XSTR( "This secondary bank cannot fire dual missiles", 1932));
+					gamesnd_play_iface(InterfaceSounds::GENERAL_FAIL);
+					hud_gauge_popup_start(HUD_WEAPONS_GAUGE);
+				}
+			} else if (Ships[objp->instance].flags[Ship::Ship_Flags::Secondary_dual_fire]) {
+				Ships[objp->instance].flags.remove(Ship::Ship_Flags::Secondary_dual_fire);
 				if(at_self) {
 					HUD_sourced_printf(HUD_SOURCE_HIDDEN, "%s", XSTR( "Secondary weapon set to normal fire mode", 34));
 					snd_play( gamesnd_get_game_sound(ship_get_sound(Player_obj, GameSounds::SECONDARY_CYCLE)) );
 					hud_gauge_popup_start(HUD_WEAPONS_GAUGE);
 				}
 			} else {
-                Ships[objp->instance].flags.set(Ship::Ship_Flags::Secondary_dual_fire);
+				Ships[objp->instance].flags.set(Ship::Ship_Flags::Secondary_dual_fire);
 				if(at_self) {
 					HUD_sourced_printf(HUD_SOURCE_HIDDEN, "%s", XSTR( "Secondary weapon set to dual fire mode", 35));
 					snd_play( gamesnd_get_game_sound(ship_get_sound(Player_obj, GameSounds::SECONDARY_CYCLE)) );

code/localization/localize.cpp

@@ -64,7 +64,7 @@ bool *Lcl_unexpected_tstring_check = nullptr;
 // NOTE: with map storage of XSTR strings, the indexes no longer need to be contiguous,
 // but internal strings should still increment XSTR_SIZE to avoid collisions.
 // retail XSTR_SIZE = 1570
-// #define XSTR_SIZE	1932 // This is the next available ID
+// #define XSTR_SIZE	1933 // This is the next available ID
 
 // struct to allow for strings.tbl-determined x offset
 // offset is 0 for english, by default

code/playerman/playercontrol.cpp

@@ -1420,7 +1420,6 @@ void player_restore_target_and_weapon_link_prefs()
 {
 	ship_info *player_sip;
 	player_sip = &Ship_info[Player_ship->ship_info_index];
-	polymodel *pm = model_get(player_sip->model_num);
 
 	//	Don't restores the save flags in training, as we must ensure certain things are off, such as speed matching.
 	if ( !(The_mission.game_type & MISSION_TYPE_TRAINING )) {
@@ -1433,7 +1432,9 @@ void player_restore_target_and_weapon_link_prefs()
 		}
 	}
 
-	if ( Player->flags & PLAYER_FLAGS_LINK_SECONDARY && (pm->n_missiles > 0 && pm->missile_banks[0].num_slots > 1) ) {
+	// restore the dual fire preference regardless of whether the current bank can use it;
+	// the flag is ignored rather than cleared for banks that can't
+	if ( Player->flags & PLAYER_FLAGS_LINK_SECONDARY ) {
 		Player_ship->flags.set(Ship::Ship_Flags::Secondary_dual_fire);
 	}
 }

code/ship/ship.cpp

@@ -14259,6 +14259,37 @@ static bool ship_fire_secondary_detonate(object *obj, ship_weapon *swp)
 
 extern void ai_maybe_announce_shockwave_weapon(object *firing_objp, int weapon_index);
 
+// Determines whether this secondary bank is currently capable of dual fire.  Note that the
+// Secondary_dual_fire flag can legitimately be set even when this returns false: the flag is
+// ignored rather than cleared so that the player's dual fire preference isn't lost when
+// cycling through banks or weapons.  All code that acts on the flag should check this too.
+bool ship_secondary_bank_can_dual_fire(const ship *shipp, int bank)
+{
+	if (bank < 0 || bank >= shipp->weapons.num_secondary_banks)
+		return false;
+
+	int weapon_class = shipp->weapons.secondary_bank_weapons[bank];
+	if (weapon_class < 0)
+		return false;
+
+	if (Weapon_info[weapon_class].wi_flags[Weapon::Info_Flags::No_doublefire])
+		return false;
+
+	if (shipp->objnum == OBJ_INDEX(Player_obj))
+	{
+		if (The_mission.ai_profile->flags[AI::Profile_Flags::Disable_player_secondary_doublefire])
+			return false;
+	}
+	else
+	{
+		if (The_mission.ai_profile->flags[AI::Profile_Flags::Disable_ai_secondary_doublefire])
+			return false;
+	}
+
+	polymodel *pm = model_get(Ship_info[shipp->ship_info_index].model_num);
+	return pm->missile_banks[bank].num_slots > 1;
+}
+
 //	Object *obj fires its secondary weapon, if it can.
 //	If its most recently fired weapon is a remotely detonatable weapon, detonate it.
 //	Returns number of weapons fired.  Note, for swarmers, returns 1 if it is allowed
@@ -14621,25 +14652,14 @@ int ship_fire_secondary( object *obj, int allow_swarm, bool rollback_shot )
 			goto done_secondary;
 		}
 
-		// Handle the optional disabling of dual fire
-		// dual fire/doublefire can be disabled for individual weapons, for players, or for AIs
-		// if any of these apply to the current weapon, unset the dual fire flag on the ship 
-		// then proceed as normal.
-		// This is only handled at firing time so dualfire isn't lost when cycling through weapons
-		if (shipp->flags[Ship_Flags::Secondary_dual_fire] &&
-			( wip->wi_flags[Weapon::Info_Flags::No_doublefire] || 
-			( The_mission.ai_profile->flags[AI::Profile_Flags::Disable_ai_secondary_doublefire] && 
-				shipp->objnum != OBJ_INDEX(Player_obj) ) ||
-			( The_mission.ai_profile->flags[AI::Profile_Flags::Disable_player_secondary_doublefire] &&
-				shipp->objnum == OBJ_INDEX(Player_obj) ))
-			) {
-			shipp->flags.remove(Ship_Flags::Secondary_dual_fire);
-		}
-
 		int start_slot, end_slot;
 		no_energy = shipp->weapon_energy < 2 * wip->energy_consumed; // whether there's enough energy for at least 1 shot was checked above
 
-		if ( shipp->flags[Ship_Flags::Secondary_dual_fire] && num_slots > 1) {
+		// Dual fire can be unavailable for this bank because it has only one firepoint, because
+		// the weapon disallows it, or because of an ai_profiles restriction.  In any of these
+		// cases the flag is ignored rather than cleared so the dual fire preference isn't lost
+		// when cycling through banks or weapons.
+		if ( shipp->flags[Ship_Flags::Secondary_dual_fire] && ship_secondary_bank_can_dual_fire(shipp, bank) ) {
 			start_slot = swp->secondary_next_slot[bank];
 			// AL 11-19-97: Ensure enough ammo remains when firing linked secondary weapons
 			if ( check_ammo && ((swp->secondary_bank_ammo[bank] < 2 && !no_ammo_needed) || no_energy) ) {
@@ -14648,9 +14668,6 @@ int ship_fire_secondary( object *obj, int allow_swarm, bool rollback_shot )
 				end_slot = start_slot+1;
 			}
 		} else {
-			// de-set the flag just in case dual-fire was set but couldn't be used
-			// because there's less than two firepoints
-			shipp->flags.remove(Ship_Flags::Secondary_dual_fire);
 			start_slot = swp->secondary_next_slot[bank];
 			end_slot = start_slot;
 		}
@@ -14779,7 +14796,7 @@ int ship_fire_secondary( object *obj, int allow_swarm, bool rollback_shot )
 		swp = &Player_ship->weapons;
 		if (bank >= 0) {
 			wip = &Weapon_info[swp->secondary_bank_weapons[bank]];
-			if (Player_ship->flags[Ship_Flags::Secondary_dual_fire]){
+			if (Player_ship->flags[Ship_Flags::Secondary_dual_fire] && ship_secondary_bank_can_dual_fire(Player_ship, bank)){
 				joy_ff_play_secondary_shoot((int) (wip->cargo_size * 2.0f));
 			} else {
 				joy_ff_play_secondary_shoot((int) wip->cargo_size);

code/ship/ship.h

@@ -1734,6 +1734,7 @@ extern bool in_autoaim_fov(ship *shipp, int bank_to_fire, object *obj);
 extern int ship_stop_fire_primary(object * obj);
 extern int ship_fire_primary(object * objp, int force = 0, bool rollback_shot = false);
 extern int ship_fire_secondary(object * objp, int allow_swarm = 0, bool rollback_shot = false );
+extern bool ship_secondary_bank_can_dual_fire(const ship *shipp, int bank);
 bool ship_start_secondary_fire(object* objp);
 bool ship_stop_secondary_fire(object* objp);
 extern int ship_launch_countermeasure(object *objp, int rand_val = -1);

code/weapon/weapons.cpp

@@ -7148,9 +7148,15 @@ int weapon_create( const vec3d *pos, const matrix *porient, int weapon_type, int
 		Assertion( position != NULL, "'%s' is trying to fire a weapon that is not selected", Ships[parent_objp->instance].ship_name );
 
 		size_t curr_pos = *position;
-		if (((Weapon_info[weapon_type].subtype == WP_LASER && parent_shipp->flags[Ship::Ship_Flags::Primary_linked]) ||
-			 (Weapon_info[weapon_type].subtype == WP_MISSILE && parent_shipp->flags[Ship::Ship_Flags::Secondary_dual_fire])) &&
-			 (curr_pos > 0)) {
+		// only advance the pattern once per linked/paired shot rather than once per projectile
+		bool paired_shot = false;
+		if (Weapon_info[weapon_type].subtype == WP_LASER) {
+			paired_shot = parent_shipp->flags[Ship::Ship_Flags::Primary_linked];
+		} else if (Weapon_info[weapon_type].subtype == WP_MISSILE && !src_turret && parent_shipp->flags[Ship::Ship_Flags::Secondary_dual_fire]) {
+			// for dual fire, also check whether the armed bank can actually use it, since the flag is ignored rather than cleared for banks that can't
+			paired_shot = ship_secondary_bank_can_dual_fire(parent_shipp, parent_shipp->weapons.current_secondary_bank);
+		}
+		if (paired_shot && (curr_pos > 0)) {
 			curr_pos--;
 		}
 		++(*position);