add Wings[] slot reassignment utilities for FRED/qtFRED

reassign_wing_slot moves a wing between Wings[] slots, fixing up every
back-reference: Ships[i].wingnum, the Starting/Squadron/TVT_wings caches
(via update_custom_wing_indexes), the FRED-side parallel array
wing_objects, and cur_wing (passed via FredWingSlotConfig so non-FRED
callers can opt out).  swap_wing_slots wraps it as a three-leg swap
through a temporary empty slot.

Also consolidates update_custom_wing_indexes (previously duplicated
verbatim in fred2/management.cpp and qtfred Editor) into common.cpp so
the new utility — and any future caller — has one shared implementation.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: Goober5000

code/missioneditor/common.cpp

@@ -98,6 +98,20 @@ anchor_t target_to_anchor(int target)
 		return anchor_t(target);
 }
 
+void update_custom_wing_indexes()
+{
+	int i;
+
+	for (i = 0; i < MAX_STARTING_WINGS; i++)
+		Starting_wings[i] = wing_name_lookup(Starting_wing_names[i], 1);
+
+	for (i = 0; i < MAX_SQUADRON_WINGS; i++)
+		Squadron_wings[i] = wing_name_lookup(Squadron_wing_names[i], 1);
+
+	for (i = 0; i < MAX_TVT_WINGS; i++)
+		TVT_wings[i] = wing_name_lookup(TVT_wing_names[i], 1);
+}
+
 void generate_weaponry_usage_list_team(int team, int* arr)
 {
 	int i;
@@ -214,14 +228,14 @@ void reassign_ship_slot(int from, int to, const FredShipSlotConfig& cfg)
 	// Wing membership: scan every wing and re-point any reference to the old slot.
 	// (wing.special_ship is wing-relative, NOT a Ships[] index, so it is intentionally
 	// not touched here.)
-	for (int w = 0; w < MAX_WINGS; ++w)
+	for (auto& w : Wings)
 	{
-		if (Wings[w].wave_count == 0)
+		if (w.wave_count == 0)
 			continue;
-		for (int k = 0; k < Wings[w].wave_count; ++k)
+		for (int k = 0; k < w.wave_count; ++k)
 		{
-			if (Wings[w].ship_index[k] == from)
-				Wings[w].ship_index[k] = to;
+			if (w.ship_index[k] == from)
+				w.ship_index[k] = to;
 		}
 	}
 
@@ -268,6 +282,74 @@ void swap_ship_slots(int a, int b, const FredShipSlotConfig& cfg)
 	reassign_ship_slot(tmp, b, cfg);
 }
 
+void reassign_wing_slot(int from, int to, const FredWingSlotConfig& cfg)
+{
+	Assertion(from != to, "reassign_wing_slot: from == to (%d)", from);
+	Assertion(from >= 0 && from < MAX_WINGS, "reassign_wing_slot: 'from' slot %d out of range", from);
+	Assertion(to >= 0 && to < MAX_WINGS, "reassign_wing_slot: 'to' slot %d out of range", to);
+	Assertion(Wings[from].wave_count > 0, "reassign_wing_slot: source slot %d is empty", from);
+	Assertion(Wings[to].wave_count == 0, "reassign_wing_slot: destination slot %d is occupied", to);
+
+	// Move the wing struct itself.  wing::clear() is the engine's canonical
+	// empty-slot state (matches ship_level_init); wave_count == 0 is the sentinel.
+	Wings[to] = Wings[from];
+	Wings[from].clear();
+
+	// Move FRED-side parallel array if the caller supplied it.
+	if (cfg.wing_objects != nullptr)
+	{
+		for (int k = 0; k < MAX_SHIPS_PER_WING; ++k)
+		{
+			cfg.wing_objects[to][k] = cfg.wing_objects[from][k];
+			cfg.wing_objects[from][k] = -1;
+		}
+	}
+
+	// Per-ship parent-wing back-reference.
+	for (auto& sh : Ships)
+	{
+		if (sh.objnum < 0)
+			continue;
+		if (sh.wingnum == from)
+			sh.wingnum = to;
+	}
+
+	// FRED's current-wing pointer, if the caller is tracking one.
+	if (cfg.cur_wing != nullptr && *cfg.cur_wing == from)
+		*cfg.cur_wing = to;
+
+	// Rebuild Starting/Squadron/TVT_wings caches from the parallel name arrays.
+	update_custom_wing_indexes();
+}
+
+void swap_wing_slots(int a, int b, const FredWingSlotConfig& cfg)
+{
+	if (a == b)
+		return;
+
+	Assertion(a >= 0 && a < MAX_WINGS, "swap_wing_slots: slot 'a' %d out of range", a);
+	Assertion(b >= 0 && b < MAX_WINGS, "swap_wing_slots: slot 'b' %d out of range", b);
+	Assertion(Wings[a].wave_count > 0 && Wings[b].wave_count > 0,
+		"swap_wing_slots: both slots must be valid (a=%d, b=%d)", a, b);
+
+	// Find a free temporary slot.
+	int tmp = -1;
+	for (int i = 0; i < MAX_WINGS; ++i)
+	{
+		if (Wings[i].wave_count == 0)
+		{
+			tmp = i;
+			break;
+		}
+	}
+	Assertion(tmp >= 0, "swap_wing_slots: no free Wings[] slot available for the temporary leg");
+
+	// Three-leg swap; each call's preconditions hold by construction.
+	reassign_wing_slot(a, tmp, cfg);
+	reassign_wing_slot(b, a, cfg);
+	reassign_wing_slot(tmp, b, cfg);
+}
+
 // Bulk-re-sort one type's subset of obj_used_list while keeping non-matching
 // entries in their original relative positions.  Each callsite supplies a
 // type matcher and a key function; the i-th matching slot (in original list

code/missioneditor/common.h

@@ -45,6 +45,11 @@ int anchor_to_target(anchor_t anchor);
 
 anchor_t target_to_anchor(int target);
 
+// Rebuild Starting_wings[], Squadron_wings[], TVT_wings[] from their parallel
+// name arrays via wing_name_lookup.  Consolidated from FRED's and qtFRED's
+// previously-duplicated copies.
+void update_custom_wing_indexes();
+
 void generate_weaponry_usage_list_team(int team, int* arr);
 
 void generate_weaponry_usage_list_wing(int wing_num, int* arr);
@@ -70,6 +75,25 @@ void reassign_ship_slot(int from, int to, const FredShipSlotConfig& cfg);
 // via a temporary empty slot.
 void swap_ship_slots(int a, int b, const FredShipSlotConfig& cfg);
 
+struct FredWingSlotConfig
+{
+	int (*wing_objects)[MAX_SHIPS_PER_WING] = nullptr;
+	int *cur_wing = nullptr;
+};
+
+// Move the wing currently in Wings[from] into Wings[to], updating every
+// back-reference (Ships[i].wingnum, Starting/Squadron/TVT_wings caches, and
+// editor-side fields supplied via cfg).  Leaves Wings[from] empty.
+// Preconditions: from != to, Wings[from].wave_count > 0, Wings[to].wave_count == 0.
+// No caller may hold a wing* to either slot across this call.
+// Fields in cfg whose pointers are nullptr are skipped.
+void reassign_wing_slot(int from, int to, const FredWingSlotConfig& cfg);
+
+// Swap the contents of two slots.  Both must be valid (Wings[a].wave_count > 0
+// and Wings[b].wave_count > 0).  Implemented as three calls to
+// reassign_wing_slot via a temporary empty slot.
+void swap_wing_slots(int a, int b, const FredWingSlotConfig& cfg);
+
 // Restore the obj_used_list invariant for the OBJ_SHIP/OBJ_START subset:
 // among ship-type entries, list order matches Ships[] index order.
 void resort_ships_in_obj_used_list();

fred2/management.cpp

@@ -2625,29 +2625,6 @@ int wing_is_player_wing(int wing)
 	return 0;
 }
 
-// Goober5000
-// This must be done when either the wing name or the custom name is changed.
-// (It's also duplicated in FS2, in post_process_mission, for setting the indexes at mission load.)
-void update_custom_wing_indexes()
-{
-	int i;
-
-	for (i = 0; i < MAX_STARTING_WINGS; i++)
-	{
-		Starting_wings[i] = wing_name_lookup(Starting_wing_names[i], 1);
-	}
-
-	for (i = 0; i < MAX_SQUADRON_WINGS; i++)
-	{
-		Squadron_wings[i] = wing_name_lookup(Squadron_wing_names[i], 1);
-	}
-
-	for (i = 0; i < MAX_TVT_WINGS; i++)
-	{
-		TVT_wings[i] = wing_name_lookup(TVT_wing_names[i], 1);
-	}
-}
-
 // Goober5000
 void update_texture_replacements(const char *old_name, const char *new_name)
 {

fred2/management.h

@@ -131,7 +131,6 @@ extern void management_add_ships_to_combo(CComboBox* box, int flags);
 
 // Goober5000
 extern int wing_is_player_wing(int wing);
-extern void update_custom_wing_indexes();
 extern void update_texture_replacements(const char* old_name, const char* new_name);
 
 #endif

qtfred/src/mission/Editor.h

@@ -188,11 +188,6 @@ class Editor : public QObject {
 
 	subsys_to_render Render_subsys;
 
-	// Goober5000
-	// This must be done when either the wing name or the custom name is changed.
-	// (It's also duplicated in FS2, in post_process_mission, for setting the indexes at mission load.)
-	static void update_custom_wing_indexes();
-
 	void ai_update_goal_references(sexp_ref_type type, const char* old_name, const char* new_name);
 
 	// Goober5000

qtfred/src/mission/EditorWing.cpp

@@ -5,6 +5,7 @@
 
 #include <globalincs/linklist.h>
 #include <globalincs/utility.h>
+#include <missioneditor/common.h>
 #include <ship/ship.h>
 
 namespace {
@@ -69,22 +70,6 @@ void Editor::set_cur_wing(int wing)
 	updateAllViewports();
 	// TODO: Add notification for a changed selection
 }
-void Editor::update_custom_wing_indexes()
-{
-	int i;
-
-	for (i = 0; i < MAX_STARTING_WINGS; i++) {
-		Starting_wings[i] = wing_name_lookup(Starting_wing_names[i], 1);
-	}
-
-	for (i = 0; i < MAX_SQUADRON_WINGS; i++) {
-		Squadron_wings[i] = wing_name_lookup(Squadron_wing_names[i], 1);
-	}
-
-	for (i = 0; i < MAX_TVT_WINGS; i++) {
-		TVT_wings[i] = wing_name_lookup(TVT_wing_names[i], 1);
-	}
-}
 
 int Editor::create_wing()
 {

qtfred/src/mission/dialogs/MissionSpecDialogModel.cpp

@@ -12,6 +12,7 @@
 
 #include "cfile/cfile.h"
 #include "localization/localize.h"
+#include "missioneditor/common.h"
 #include "mission/missionmessage.h"
 #include "mission/mission_flags.h"
 #include "scripting/global_hooks.h"
@@ -227,7 +228,7 @@ bool MissionSpecDialogModel::apply() {
 		strcpy_s(TVT_wing_names[i], _m_custom_tvt_wings[i].c_str());
 	}
 
-	Editor::update_custom_wing_indexes();
+	update_custom_wing_indexes();
 
 	// scripts may rebuild LuaEnums when custom data/strings change.
 	if (scripting::hooks::FredOnMissionSpecsSave->isActive()) {