fix(mechanics): Improve handling of orders when the selected escort i…

…s destroyed (endless-sky#10459)

- After a player ship has finished exploding, it is no longer considered "selected" and so will no longer block orders to the wider fleet.
- If orders are issued while all selected ships are exploding, a new message indicating that they cannot follow orders will be used, instead of the normal message indicating that orders have been issued.

source/AI.cpp

@@ -4832,25 +4832,42 @@ void AI::IssueOrders(const Orders &newOrders, const string &description)
 
 	// Figure out what ships we are giving orders to.
 	vector<const Ship *> ships;
+	size_t destroyedCount = 0;
 	if(player.SelectedShips().empty())
 	{
 		for(const shared_ptr<Ship> &it : player.Ships())
 			if(it.get() != player.Flagship() && !it->IsParked())
-				ships.push_back(it.get());
-		who = ships.size() > 1 ? "Your fleet is " : "Your escort is ";
+			{
+				if(it->IsDestroyed())
+					++destroyedCount;
+				else
+					ships.push_back(it.get());
+			}
+		who = (ships.empty() ? destroyedCount : ships.size()) > 1
+			? "Your fleet is " : "Your escort is ";
 	}
 	else
 	{
 		for(const weak_ptr<Ship> &it : player.SelectedShips())
 		{
 			shared_ptr<Ship> ship = it.lock();
-			if(ship)
+			if(!ship)
+				continue;
+			if(ship->IsDestroyed())
+				++destroyedCount;
+			else
 				ships.push_back(ship.get());
 		}
-		who = ships.size() > 1 ? "The selected escorts are " : "The selected escort is ";
+		who = (ships.empty() ? destroyedCount : ships.size()) > 1
+			? "The selected escorts are " : "The selected escort is ";
 	}
 	if(ships.empty())
+	{
+		if(destroyedCount)
+			Messages::Add(who + "destroyed and unable to execute your orders.",
+				Messages::Importance::High);
 		return;
+	}
 
 	Point centerOfGravity;
 	bool isMoveOrder = (newOrders.HasMoveTo());

source/Engine.cpp

@@ -1700,6 +1700,9 @@ void Engine::MoveShip(const shared_ptr<Ship> &ship)
 			for(const auto &bay : ship->Bays())
 				if(bay.ship)
 					eventQueue.emplace_back(nullptr, bay.ship, ShipEvent::DESTROY);
+			// If this is a player ship, make sure it's no longer selected.
+			if(ship->IsYours())
+				player.DeselectShip(ship.get());
 		}
 		return;
 	}

source/PlayerInfo.cpp

@@ -2777,6 +2777,18 @@ void PlayerInfo::SelectShip(const Ship *ship, bool hasShift)
 
 
 
+void PlayerInfo::DeselectShip(const Ship *ship)
+{
+	for(auto it = selectedShips.begin(); it != selectedShips.end(); ++it)
+		if(it->lock().get() == ship)
+		{
+			selectedShips.erase(it);
+			return;
+		}
+}
+
+
+
 void PlayerInfo::SelectGroup(int group, bool hasShift)
 {
 	int bit = (1 << group);

source/PlayerInfo.h

@@ -307,6 +307,7 @@ class PlayerInfo {
 	bool SelectShips(const Rectangle &box, bool hasShift);
 	bool SelectShips(const std::vector<const Ship *> &stack, bool hasShift);
 	void SelectShip(const Ship *ship, bool hasShift);
+	void DeselectShip(const Ship *ship);
 	void SelectGroup(int group, bool hasShift);
 	void SetGroup(int group, const std::set<Ship *> *newShips = nullptr);
 	std::set<Ship *> GetGroup(int group);