Change: Only resort town directory window on population change if necessary

src/town.h

@@ -161,6 +161,7 @@ enum TownRatingCheckType {
 /** Special values for town list window for the data parameter of #InvalidateWindowData. */
 enum TownDirectoryInvalidateWindowData {
 	TDIWD_FORCE_REBUILD,
+	TDIWD_POPULATION_CHANGE,
 	TDIWD_FORCE_RESORT,
 };
 

src/town_cmd.cpp

@@ -423,7 +423,7 @@ static void ChangePopulation(Town *t, int mod)
 	InvalidateWindowData(WC_TOWN_VIEW, t->index); // Cargo requirements may appear/vanish for small populations
 	if (_settings_client.gui.population_in_label) t->UpdateVirtCoord();
 
-	InvalidateWindowData(WC_TOWN_DIRECTORY, 0, TDIWD_FORCE_RESORT);
+	InvalidateWindowData(WC_TOWN_DIRECTORY, 0, TDIWD_POPULATION_CHANGE);
 }
 
 /**

src/town_gui.cpp

@@ -994,6 +994,10 @@ public:
 				this->towns.ForceRebuild();
 				break;
 
+			case TDIWD_POPULATION_CHANGE:
+				if (this->towns.SortType() == 1) this->towns.ForceResort();
+				break;
+
 			default:
 				this->towns.ForceResort();
 		}