Zoning: Add modes to show 2x2 and 3x3 town road grids

src/lang/english.txt

@@ -5948,6 +5948,8 @@ STR_ZONING_STA_CATCH_OPEN                                       :Station catchme
 STR_ZONING_BUL_UNSER                                            :Unserved buildings
 STR_ZONING_IND_UNSER                                            :Unserved industries
 STR_ZONING_TRACERESTRICT                                        :Restricted signals
+STR_ZONING_2x2_GRID                                             :2x2 town road grid
+STR_ZONING_3x3_GRID                                             :3x3 town road grid
 
 STR_TMPL_RPL_TITLE                                              :{WHITE}Template Replacement
 STR_TMPL_TEMPLATE_REPLACEMENT                                   :Template Replacement

src/zoning.h

@@ -27,6 +27,8 @@ enum ZoningEvaluationMode {
 	ZEM_BUL_UNSER,     ///< Check for unserved buildings
 	ZEM_IND_UNSER,     ///< Check for unserved industries
 	ZEM_TRACERESTRICT, ///< Check for restricted signals
+	ZEM_2x2_GRID,      ///< Show 2x2 town road grid
+	ZEM_3x3_GRID,      ///< Show 3x3 town road grid
 };
 
 /**

src/zoning_cmd.cpp

@@ -317,6 +317,24 @@ SpriteID TileZoneCheckTraceRestrictEvaluation(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
+ */
+inline SpriteID TileZoneCheckRoadGridEvaluation(TileIndex tile, uint grid_size)
+{
+	const bool x_grid = (TileX(tile) % grid_size == 0);
+	const bool y_grid = (TileY(tile) % grid_size == 0);
+	if (x_grid || y_grid) {
+		return SPR_ZONING_INNER_HIGHLIGHT_LIGHT_BLUE;
+	} else {
+		return ZONING_INVALID_SPRITE_ID;
+	}
+}
+
 /**
  * General evaluation function; calls all the other functions depending on
  * evaluation mode.
@@ -339,6 +357,8 @@ SpriteID TileZoningSpriteEvaluation(TileIndex tile, Owner owner, ZoningEvaluatio
 		case ZEM_BUL_UNSER:     return TileZoneCheckUnservedBuildingsEvaluation(tile, owner);
 		case ZEM_IND_UNSER:     return TileZoneCheckUnservedIndustriesEvaluation(tile, owner);
 		case ZEM_TRACERESTRICT: return TileZoneCheckTraceRestrictEvaluation(tile, owner);
+		case ZEM_2x2_GRID:      return TileZoneCheckRoadGridEvaluation(tile, 3);
+		case ZEM_3x3_GRID:      return TileZoneCheckRoadGridEvaluation(tile, 4);
 		default:                return ZONING_INVALID_SPRITE_ID;
 	}
 }

src/zoning_gui.cpp

@@ -42,6 +42,8 @@ static const StringID _zone_type_strings[] = {
 	STR_ZONING_BUL_UNSER,
 	STR_ZONING_IND_UNSER,
 	STR_ZONING_TRACERESTRICT,
+	STR_ZONING_2x2_GRID,
+	STR_ZONING_3x3_GRID,
 	INVALID_STRING_ID
 };
 
@@ -54,6 +56,8 @@ static const ZoningEvaluationMode _zone_type_modes[] = {
 	ZEM_BUL_UNSER,
 	ZEM_IND_UNSER,
 	ZEM_TRACERESTRICT,
+	ZEM_2x2_GRID,
+	ZEM_3x3_GRID,
 };
 
 static ZoningEvaluationMode DropDownIndexToZoningEvaluationMode(int index)