Zoning: Add mode to show restricted signals.

src/lang/english.txt

@@ -5531,3 +5531,4 @@ STR_ZONING_CAN_BUILD                                            :Where I can't b
 STR_ZONING_STA_CATCH                                            :Station catchment
 STR_ZONING_BUL_UNSER                                            :Unserved buildings
 STR_ZONING_IND_UNSER                                            :Unserved industries
+STR_ZONING_TRACERESTRICT                                        :Restricted signals

src/zoning.h

@@ -25,6 +25,7 @@ enum ZoningEvaluationMode {
 	ZEM_STA_CATCH,     ///< Check catchment area for stations
 	ZEM_BUL_UNSER,     ///< Check for unserved buildings
 	ZEM_IND_UNSER,     ///< Check for unserved industries
+	ZEM_TRACERESTRICT, ///< Check for restricted signals
 };
 
 /**

src/zoning_cmd.cpp

@@ -23,6 +23,7 @@
 #include "station_func.h"
 #include "station_map.h"
 #include "town.h"
+#include "tracerestrict.h"
 #include "zoning.h"
 
 Zoning _zoning;
@@ -286,6 +287,22 @@ SpriteID TileZoneCheckUnservedIndustriesEvaluation(TileIndex tile, Owner owner)
 	return ZONING_INVALID_SPRITE_ID;
 }
 
+/**
+ * Detect whether a tile is a restricted signal tile
+ *
+ * @param TileIndex tile
+ * @param Owner owner
+ * @return red if a restricted signal, nothing otherwise
+ */
+SpriteID TileZoneCheckTraceRestrictEvaluation(TileIndex tile, Owner owner)
+{
+	if (IsTileType(tile, MP_RAILWAY) && HasSignals(tile) && IsRestrictedSignal(tile)) {
+		return SPR_ZONING_INNER_HIGHLIGHT_RED;
+	}
+
+	return ZONING_INVALID_SPRITE_ID;
+}
+
 /**
  * General evaluation function; calls all the other functions depending on
  * evaluation mode.
@@ -306,6 +323,7 @@ SpriteID TileZoningSpriteEvaluation(TileIndex tile, Owner owner, ZoningEvaluatio
 		case ZEM_STA_CATCH:  return TileZoneCheckStationCatchmentEvaluation(tile, owner);
 		case ZEM_BUL_UNSER:  return TileZoneCheckUnservedBuildingsEvaluation(tile, owner);
 		case ZEM_IND_UNSER:  return TileZoneCheckUnservedIndustriesEvaluation(tile, owner);
+		case ZEM_TRACERESTRICT:  return TileZoneCheckTraceRestrictEvaluation(tile, owner);
 		default:             return ZONING_INVALID_SPRITE_ID;
 	}
 }

src/zoning_gui.cpp

@@ -40,6 +40,7 @@ static const StringID _zone_type_strings[] = {
 	STR_ZONING_STA_CATCH,
 	STR_ZONING_BUL_UNSER,
 	STR_ZONING_IND_UNSER,
+	STR_ZONING_TRACERESTRICT,
 	INVALID_STRING_ID
 };
 
@@ -50,6 +51,7 @@ static const ZoningEvaluationMode _zone_type_modes[] = {
 	ZEM_STA_CATCH,
 	ZEM_BUL_UNSER,
 	ZEM_IND_UNSER,
+	ZEM_TRACERESTRICT,
 };
 
 static ZoningEvaluationMode DropDownIndexToZoningEvaluationMode(int index)