Implement sound api and some sounds

- Level crossing bell
- Horns
- Subway train driving and door sounds
...to be continued...

advtrains_train_industrial/init.lua

@@ -39,6 +39,7 @@ advtrains.register_wagon("engine_industrial", {
 	is_locomotive=true,
 	collisionbox = {-1.0,-0.5,-1.0, 1.0,2.5,1.0},
 	drops={"default:steelblock 4"},
+	horn_sound = "advtrains_industrial_horn",
 }, S("Industrial Train Engine"), "advtrains_engine_industrial_inv.png")
 advtrains.register_wagon("wagon_tank", {
 	mesh="advtrains_wagon_tank.b3d",

advtrains_train_japan/init.lua

@@ -72,6 +72,7 @@ advtrains.register_wagon("engine_japan", {
 	is_locomotive=true,
 	collisionbox = {-1.0,-0.5,-1.0, 1.0,2.5,1.0},
 	drops={"default:steelblock 4"},
+	horn_sound = "advtrains_japan_horn",
 }, S("Japanese Train Engine"), "advtrains_engine_japan_inv.png")
 
 advtrains.register_wagon("wagon_japan", {

advtrains_train_steam/init.lua

@@ -71,6 +71,7 @@ advtrains.register_wagon("newlocomotive", {
 		})
 	end,
 	drops={"default:steelblock 4"},
+	horn_sound = "advtrains_steam_whistle",
 }, S("Steam Engine"), "advtrains_engine_steam_inv.png")
 
 advtrains.register_wagon("detailed_steam_engine", {
@@ -139,6 +140,7 @@ advtrains.register_wagon("detailed_steam_engine", {
 		})
 	end,
 	drops={"default:steelblock 4"},
+	horn_sound = "advtrains_steam_whistle",
 }, S("Detailed Steam Engine"), "advtrains_detailed_engine_steam_inv.png")
 
 advtrains.register_wagon("wagon_default", {

advtrains_train_subway/init.lua

@@ -59,11 +59,13 @@ advtrains.register_wagon("subway_wagon", {
 	doors={
 		open={
 			[-1]={frames={x=0, y=20}, time=1},
-			[1]={frames={x=40, y=60}, time=1}
+			[1]={frames={x=40, y=60}, time=1},
+			sound = "advtrains_subway_dopen",
 		},
 		close={
 			[-1]={frames={x=20, y=40}, time=1},
-			[1]={frames={x=60, y=80}, time=1}
+			[1]={frames={x=60, y=80}, time=1},
+			sound = "advtrains_subway_dclose",
 		}
 	},
 	door_entry={-1, 1},
@@ -73,10 +75,26 @@ advtrains.register_wagon("subway_wagon", {
 	collisionbox = {-1.0,-0.5,-1.0, 1.0,2.5,1.0},
 	is_locomotive=true,
 	drops={"default:steelblock 4"},
-	--custom_on_activate = function(self, dtime_s)
-	--	atprint("subway custom_on_activate")
-	--	self.object:set_animation({x=1,y=80}, 15, 0, true)
-	--end,
+	horn_sound = "advtrains_subway_horn",
+	custom_on_velocity_change = function(self, velocity, old_velocity)
+		if old_velocity == 0 and velocity > 0 then
+			minetest.sound_play("advtrains_subway_depart", {object = self.object})
+		end
+		if velocity < 2 and (old_velocity >= 2 or old_velocity == velocity) and not self.sound_arrive_handle then
+			self.sound_arrive_handle = minetest.sound_play("advtrains_subway_arrive", {object = self.object})
+		elseif (velocity > old_velocity) and self.sound_arrive_handle then
+			minetest.sound_stop(self.sound_arrive_handle)
+			self.sound_arrive_handle = nil
+		end
+		if velocity > 0 and not self.sound_loop_handle then
+			self.sound_loop_handle = minetest.sound_play({name="advtrains_subway_loop", gain=0.3}, {object = self.object, loop=true})
+		elseif velocity==0 then
+			if self.sound_loop_handle then
+				minetest.sound_stop(self.sound_loop_handle)
+				self.sound_loop_handle = nil
+			end
+		end
+	end,
 }, S("Subway Passenger Wagon"), "advtrains_subway_wagon_inv.png")
 
 --wagons