Merge branch 'master' into jgrpp

# Conflicts:
#	cmake/CompileFlags.cmake
#	src/aircraft_cmd.cpp
#	src/blitter/32bpp_anim.cpp
#	src/cargopacket.cpp
#	src/cheat_gui.cpp
#	src/company_cmd.cpp
#	src/company_gui.cpp
#	src/core/pool_func.hpp
#	src/date.cpp
#	src/economy.cpp
#	src/error_gui.cpp
#	src/ground_vehicle.cpp
#	src/ground_vehicle.hpp
#	src/group_gui.cpp
#	src/industry_cmd.cpp
#	src/lang/dutch.txt
#	src/lang/french.txt
#	src/lang/german.txt
#	src/linkgraph/linkgraph_gui.cpp
#	src/linkgraph/mcf.cpp
#	src/network/network_content.cpp
#	src/network/network_server.cpp
#	src/network/network_udp.cpp
#	src/newgrf_engine.cpp
#	src/newgrf_station.cpp
#	src/order_cmd.cpp
#	src/order_gui.cpp
#	src/pathfinder/follow_track.hpp
#	src/pathfinder/yapf/yapf_common.hpp
#	src/saveload/saveload.cpp
#	src/settings_gui.cpp
#	src/station_cmd.cpp
#	src/station_kdtree.h
#	src/string_func.h
#	src/table/settings.ini
#	src/tgp.cpp
#	src/timetable_cmd.cpp
#	src/timetable_gui.cpp
#	src/toolbar_gui.cpp
#	src/town_cmd.cpp
#	src/train_cmd.cpp
#	src/train_gui.cpp
#	src/tree_gui.cpp
#	src/tunnelbridge_cmd.cpp
#	src/vehicle.cpp
#	src/vehicle_gui.cpp
#	src/video/sdl2_v.cpp
#	src/video/sdl_v.cpp
#	src/video/win32_v.cpp
#	src/viewport.cpp
#	src/viewport_sprite_sorter_sse4.cpp
#	src/window.cpp

src/newgrf_roadtype.cpp

@@ -132,6 +132,37 @@ SpriteID GetCustomRoadSprite(const RoadTypeInfo *rti, TileIndex tile, RoadTypeSp
 	return group->GetResult();
 }
 
+/**
+ * Translate an index to the GRF-local road/tramtype-translation table into a RoadType.
+ * @param rtt       Whether to index the road- or tramtype-table.
+ * @param tracktype Index into GRF-local translation table.
+ * @param grffile   Originating GRF file.
+ * @return RoadType or INVALID_ROADTYPE if the roadtype is unknown.
+ */
+RoadType GetRoadTypeTranslation(RoadTramType rtt, uint8 tracktype, const GRFFile *grffile)
+{
+	/* Because OpenTTD mixes RoadTypes and TramTypes into the same type,
+	 * the mapping of the original road- and tramtypes does not match the default GRF-local mapping.
+	 * So, this function cannot provide any similar behavior to GetCargoTranslation() and GetRailTypeTranslation()
+	 * when the GRF defines no translation table.
+	 * But since there is only one default road/tram-type, this makes little sense anyway.
+	 * So for GRF without translation table, we always return INVALID_ROADTYPE.
+	 */
+
+	if (grffile == nullptr) return INVALID_ROADTYPE;
+
+	const auto &list = rtt == RTT_TRAM ? grffile->tramtype_list : grffile->roadtype_list;
+	if (tracktype >= list.size()) return INVALID_ROADTYPE;
+
+	/* Look up roadtype including alternate labels. */
+	RoadType result = GetRoadTypeByLabel(list[tracktype]);
+
+	/* Check whether the result is actually the wanted road/tram-type */
+	if (result != INVALID_ROADTYPE && GetRoadTramType(result) != rtt) return INVALID_ROADTYPE;
+
+	return result;
+}
+
 /**
  * Perform a reverse roadtype lookup to get the GRF internal ID.
  * @param roadtype The global (OpenTTD) roadtype.