accelerate non-moving carts on `mcl_minecarts:golden_rail_on` (#4097)

accelerate a non-moving minecart away from a solid opaque block the powered rail is facing

Reviewed-on: https://git.minetest.land/MineClone2/MineClone2/pulls/4097
Reviewed-by: the-real-herowl <the-real-herowl@noreply.git.minetest.land>
Co-authored-by: nixnoxus <nixnoxus@web.de>
Co-committed-by: nixnoxus <nixnoxus@web.de>

mods/ENTITIES/mcl_minecarts/functions.lua

@@ -135,3 +135,33 @@ function mcl_minecarts:get_rail_direction(pos_, dir, ctrl, old_switch, railtype)
 	end
 	return {x=0, y=0, z=0}
 end
+
+local plane_adjacents = {
+	vector.new(-1,0,0),
+	vector.new(1,0,0),
+	vector.new(0,0,-1),
+	vector.new(0,0,1),
+}
+
+function mcl_minecarts:get_start_direction(pos)
+	local dir
+	local i = 0
+	while (not dir and i < #plane_adjacents) do
+		i = i+1
+		local node = minetest.get_node_or_nil(vector.add(pos, plane_adjacents[i]))
+		if node ~= nil
+		and minetest.get_item_group(node.name, "rail") == 0
+		and minetest.get_item_group(node.name, "solid") == 1
+		and minetest.get_item_group(node.name, "opaque") == 1
+		then
+			dir = mcl_minecarts:check_front_up_down(pos, vector.multiply(plane_adjacents[i], -1), true)
+		end
+	end
+	return dir
+end
+
+function mcl_minecarts:set_velocity(obj, dir, factor)
+	obj._velocity = vector.multiply(dir, factor or 3)
+	obj._old_pos = nil
+	obj._punched = true
+end

mods/ENTITIES/mcl_minecarts/init.lua

@@ -241,9 +241,7 @@ local function register_entity(entity_id, mesh, textures, drop, on_rightclick, o
 			if vector.equals(cart_dir, {x=0, y=0, z=0}) then
 				return
 			end
-			self._velocity = vector.multiply(cart_dir, 3)
-			self._old_pos = nil
-			self._punched = true
+			mcl_minecarts:set_velocity(self, cart_dir)
 			return
 		end
 
@@ -300,9 +298,7 @@ local function register_entity(entity_id, mesh, textures, drop, on_rightclick, o
 		time_from_last_punch = math.min(time_from_last_punch, tool_capabilities.full_punch_interval)
 		local f = 3 * (time_from_last_punch / tool_capabilities.full_punch_interval)
 
-		self._velocity = vector.multiply(cart_dir, f)
-		self._old_pos = nil
-		self._punched = true
+		mcl_minecarts:set_velocity(self, cart_dir, f)
 	end
 
 	cart.on_activate_by_rail = on_activate_by_rail
@@ -470,7 +466,7 @@ local function register_entity(entity_id, mesh, textures, drop, on_rightclick, o
 			return
 		end
 
-		local dir, last_switch = nil, nil
+		local dir, last_switch, restart_pos = nil, nil, nil
 		if not pos then
 			pos = self.object:get_pos()
 		end
@@ -497,6 +493,9 @@ local function register_entity(entity_id, mesh, textures, drop, on_rightclick, o
 				minetest.swap_node(rou_pos, newnode)
 				mesecon.receptor_on(rou_pos)
 			end
+			if node.name == "mcl_minecarts:golden_rail_on" then
+				restart_pos = rou_pos
+			end
 			if node_old.name == "mcl_minecarts:detector_rail_on" then
 				local newnode = {name="mcl_minecarts:detector_rail", param2 = node_old.param2}
 				minetest.swap_node(rou_old, newnode)
@@ -647,6 +646,14 @@ local function register_entity(entity_id, mesh, textures, drop, on_rightclick, o
 		if update.pos then
 			self.object:set_pos(pos)
 		end
+		
+		-- stopped on "mcl_minecarts:golden_rail_on"
+		if vector.equals(vel, {x=0, y=0, z=0}) and restart_pos then
+			local dir = mcl_minecarts:get_start_direction(restart_pos)
+			if dir then
+				mcl_minecarts:set_velocity(self, dir)
+			end
+		end
 	end
 
 	function cart:get_staticdata()
@@ -687,7 +694,15 @@ function mcl_minecarts.place_minecart(itemstack, pointed_thing, placer)
 	if le then
 		le._railtype = railtype
 	end
-	local cart_dir = mcl_minecarts:get_rail_direction(railpos, {x=1, y=0, z=0}, nil, nil, railtype)
+	local cart_dir
+	if node.name == "mcl_minecarts:golden_rail_on" then
+		cart_dir = mcl_minecarts:get_start_direction(railpos)
+	end
+	if cart_dir then
+		mcl_minecarts:set_velocity(le, cart_dir)
+	else
+		cart_dir = mcl_minecarts:get_rail_direction(railpos, {x=1, y=0, z=0}, nil, nil, railtype)
+	end
 	cart:set_yaw(minetest.dir_to_yaw(cart_dir))
 
 	local pname = ""

mods/ENTITIES/mcl_minecarts/rails.lua

@@ -112,6 +112,22 @@ register_rail("mcl_minecarts:golden_rail_on",
 				onstate = "mcl_minecarts:golden_rail_on",
 				rules = rail_rules_long,
 			},
+			effector = {
+				action_on = function(pos, node)
+					local dir = mcl_minecarts:get_start_direction(pos)
+					if not dir then return end
+					local objs = minetest.get_objects_inside_radius(pos, 1)
+					for _, o in pairs(objs) do
+						local l = o:get_luaentity()
+						local v = o:get_velocity()
+						if l and string.sub(l.name, 1, 14) == "mcl_minecarts:"
+						and v and vector.equals(v, vector.zero())
+						then
+							mcl_minecarts:set_velocity(l, dir)
+						end
+					end
+end,
+			},
 		},
 		drop = "mcl_minecarts:golden_rail",
 	},