Function GetTownRoadGridElement

src/town_cmd.cpp:1154–1201

* Generate the RoadBits of a grid tile. * * @param t The current town. * @param tile The tile in reference to the town. * @param dir The direction to which we are growing. * @return The RoadBit of the current tile regarding the selected town layout. */

 * @return The RoadBit of the current tile regarding the selected town layout.
 */
static RoadBits GetTownRoadGridElement(Town *t, TileIndex tile, DiagDirection dir)
{
	/* align the grid to the downtown */
	TileIndexDiffC grid_pos = TileIndexToTileIndexDiffC(t->xy, tile); // Vector from downtown to the tile
	RoadBits rcmd = ROAD_NONE;

	switch (t->layout) {
		default: NOT_REACHED();

		case TL_2X2_GRID:
			if ((grid_pos.x % 3) == 0) rcmd |= ROAD_Y;
			if ((grid_pos.y % 3) == 0) rcmd |= ROAD_X;
			break;

		case TL_3X3_GRID:
			if ((grid_pos.x % 4) == 0) rcmd |= ROAD_Y;
			if ((grid_pos.y % 4) == 0) rcmd |= ROAD_X;
			break;
	}

	/* Optimise only X-junctions */
	if (rcmd != ROAD_ALL) return rcmd;

	RoadBits rb_template;

	switch (GetTileSlope(tile)) {
		default:       rb_template = ROAD_ALL; break;
		case SLOPE_W:  rb_template = ROAD_NW | ROAD_SW; break;
		case SLOPE_SW: rb_template = ROAD_Y  | ROAD_SW; break;
		case SLOPE_S:  rb_template = ROAD_SW | ROAD_SE; break;
		case SLOPE_SE: rb_template = ROAD_X  | ROAD_SE; break;
		case SLOPE_E:  rb_template = ROAD_SE | ROAD_NE; break;
		case SLOPE_NE: rb_template = ROAD_Y  | ROAD_NE; break;
		case SLOPE_N:  rb_template = ROAD_NE | ROAD_NW; break;
		case SLOPE_NW: rb_template = ROAD_X  | ROAD_NW; break;
		case SLOPE_STEEP_W:
		case SLOPE_STEEP_S:
		case SLOPE_STEEP_E:
		case SLOPE_STEEP_N:
			rb_template = ROAD_NONE;
			break;
	}

	/* Stop if the template is compatible to the growth dir */
	if (DiagDirToRoadBits(ReverseDiagDir(dir)) & rb_template) return rb_template;
	/* If not generate a straight road in the direction of the growth */
	return DiagDirToRoadBits(dir) | DiagDirToRoadBits(ReverseDiagDir(dir));
}

/**
 * Grows the town with an extra house.