depends.txt -> mod.conf

Something like this is in the default mod now.

.gitignore

@@ -0,0 +1,4 @@
+## Generic ignorable patterns and files
+*~
+.*.swp
+debug.txt

.luacheckrc

@@ -0,0 +1,12 @@
+read_globals = {
+	minetest = {
+		fields = {
+			registered_entities = {
+				read_only = false,
+				other_fields = true
+			}
+		},
+		other_fields = true
+	},
+	"vector"
+}

LICENSE.txt

@@ -0,0 +1,2 @@
+MIT for the code
+The original mod was licensed under WTFPL.

README.md

@@ -0,0 +1,2 @@
+For a description of this Minetest mod, see
+https://forum.minetest.net/viewtopic.php?f=9&t=10271.

README.txt

@@ -1,38 +0,0 @@
-=== BUILTIN_ITEM MOD for MINETEST-C55 ===
-by PilzAdam
-
-Features:
-This mod adds some new features to the builtin items:
-- The items are pushed by flowing water
-- The items are destroyed by lava
-- The items are removed after 300 seconds or the time that is specified by
-   remove_items in minetest.conf (0 disables it)
-
-How to install:
-Unzip the archive an place it in minetest-base-directory/mods/minetest/
-if you have a windows client or a linux run-in-place client. If you have
-a linux system-wide instalation place it in ~/.minetest/mods/minetest/.
-If you want to install this mod only in one world create the folder
-worldmods/ in your worlddirectory.
-For further information or help see:
-http://wiki.minetest.com/wiki/Installing_Mods
-
-License:
-WTFPL (see below)
-
-See also:
-http://minetest.net/
-
-         DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
-                    Version 2, December 2004
-
- Copyright (C) 2004 Sam Hocevar <sam@hocevar.net>
-
- Everyone is permitted to copy and distribute verbatim or modified
- copies of this license document, and changing it is allowed as long
- as the name is changed.
-
-            DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
-   TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
-
-  0. You just DO WHAT THE FUCK YOU WANT TO. 

init.lua

@@ -1,216 +1,127 @@
-local time = tonumber(minetest.setting_get("remove_items"))
-if not time then
-	time = 1800 -- set to 30 minutes the time before remove a dropped item
-end
+-- Use the movement gravity for the downwards acceleration.
+-- The setting may change in-game but for simplicity we don't support this.
+local movement_gravity = tonumber(minetest.settings:get("movement_gravity"))
+	or 9.81
 
-unwalkable_nodes = {}
-
-minetest.after(0, function()
-	for itemname, node in pairs(minetest.registered_nodes) do
-		if node.walkable == false then
-			table.insert(unwalkable_nodes, 1, itemname)
-		end
-	end
-end)
-
-local get_flowing_dir = function(self)
-	local pos = self.object:getpos()
+-- get_flow_raw determines the horizontal flow vector for a flowing liquid node,
+-- or returns nothing if the flow is zero
+local neighbour_offsets = {
+	{x=-1, y=0, z=0},
+	{x=1, y=0, z=0},
+	{x=0, y=0, z=-1},
+	{x=0, y=0, z=1}
+}
+local function get_flow_raw(pos)
+	-- FIXME: Do we need to treat nodes with special liquid_range differently?
 	local param2 = minetest.get_node(pos).param2
-	for i,d in ipairs({-1, 1, -1, 1}) do
-		if i<3 then
-			pos.x = pos.x+d
-		else
-			pos.z = pos.z+d
-		end
-
-		local name = minetest.get_node(pos).name
-		local par2 = minetest.get_node(pos).param2
-		if name == "default:water_flowing" and par2 < param2 then
-			return pos
-		end
-
-		if i<3 then
-			pos.x = pos.x-d
-		else
-			pos.z = pos.z-d
-		end
+	if param2 == 15 then
+		-- The liquid has full height and flows downwards
+		return
 	end
-	return nil
+	local flow = {x = 0, y = 0, z = 0}
+	local height = param2 % 8
+	for n = 1, 4 do
+		local node = minetest.get_node(vector.add(pos, neighbour_offsets[n]))
+		local def = minetest.registered_nodes[node.name]
+		local height_other
+		if not def or def.walkable then
+			-- A solid node, so no flow happens
+			height_other = height
+		elseif def.liquidtype == "source" then
+			-- Assume that relevant liquid comes from this source
+			height_other = 8
+		elseif def.liquidtype == "flowing" then
+			-- This neighbour is also a flowing liquid
+			height_other = node.param2 % 8
+		else
+			-- There is a free space, e.g. air or a plant
+			height_other = 0
+		end
+		local fl = vector.multiply(neighbour_offsets[n], height - height_other)
+		flow = vector.add(flow, fl)
+	end
+	if vector.equals(flow, {x = 0, y = 0, z = 0}) then
+		return
+	end
+	return vector.normalize(flow)
 end
 
-minetest.register_entity(":__builtin:item", {
-	initial_properties = {
-		hp_max = 1,
-		physical = true,
-		collisionbox = {-0.175, -0.175, -0.175, 0.175, 0.175, 0.175},
-		collide_with_objects = false,
-		visual = "sprite",
-		visual_size = {x=0.5, y=0.5},
-		textures = {""},
-		spritediv = {x=1, y=1},
-		initial_sprite_basepos = {x=0, y=0},
-		is_visible = false,
-		timer = 0,
-	},
-
-	itemstring = "",
-	physical_state = true,
-
-	set_item = function(self, itemstring)
-		self.itemstring = itemstring
-		local stack = ItemStack(itemstring)
-		local itemtable = stack:to_table()
-		local itemname = nil
-		if itemtable then
-			itemname = stack:to_table().name
-		end
-		local item_texture = nil
-		local item_type = ""
-		if minetest.registered_items[itemname] then
-			item_texture = minetest.registered_items[itemname].inventory_image
-			item_type = minetest.registered_items[itemname].type
-		end
-		local prop = {
-			is_visible = true,
-			visual = "wielditem",
-			textures = {(itemname or "unknown_item.png")},
-			visual_size = {x=0.175, y=0.175},
-			automatic_rotate = math.pi * 0.5,
-		}
-		self.object:set_properties(prop)
-	end,
-
-	get_staticdata = function(self)
-		--return self.itemstring
-		return minetest.serialize({
-			itemstring = self.itemstring,
-			always_collect = self.always_collect,
-			timer = self.timer,
-		})
-	end,
-
-	on_activate = function(self, staticdata, dtime_s)
-		if string.sub(staticdata, 1, string.len("return")) == "return" then
-			local data = minetest.deserialize(staticdata)
-			if data and type(data) == "table" then
-				self.itemstring = data.itemstring
-				self.always_collect = data.always_collect
-				self.timer = data.timer
-				if not self.timer then
-					self.timer = 0
-				end
-				self.timer = self.timer+dtime_s
-			end
-		else
-			self.itemstring = staticdata
-		end
-		self.object:set_armor_groups({immortal=1})
-		self.object:setvelocity({x=0, y=2, z=0})
-		self.object:setacceleration({x=0, y=-10, z=0})
-		self:set_item(self.itemstring)
-	end,
-
-	on_step = function(self, dtime)
-		if not self.timer then
-			self.timer = 0
-		end
-		self.timer = self.timer + dtime
-		if self.itemstring == "" or (time ~= 0 and (self.timer > time)) then
-			self.object:remove()
-			return
-		end
-
-		local p = self.object:getpos()
-
-		local name = minetest.get_node(p).name
-		if not minetest.registered_nodes[name] then return end
-		if minetest.registered_nodes[name].damage_per_second > 0 or name == "maptools:igniter" then
-			minetest.sound_play("builtin_item_lava", {pos = p, gain = 0.5})
-			self.object:remove()
-			return
-		end
-
-		--[[ if name == "default:water_source" then
-			self.object:setacceleration({x = 0, y = 4, z = 0})
-		else
-			self.object:setacceleration({x = 0, y = -10, z = 0})
-		end
-		--]]
-
-		if minetest.registered_nodes[name].liquidtype == "flowing" then
-			local vec = get_flowing_dir(self)
-			if vec then
-				local v = self.object:getvelocity()
-				if v and vec.x-p.x > 0 then
-					self.object:setacceleration({x = 0, y = 0, z = 0})
-					self.object:setvelocity({x = 1, y = -0.22, z = 0})
-				elseif v and vec.x-p.x < 0 then
-					self.object:setacceleration({x = 0, y = 0, z = 0})
-					self.object:setvelocity({x = -1, y = -0.22, z = 0})
-				elseif v and vec.z-p.z > 0 then
-					self.object:setacceleration({x = 0, y = 0, z = 0})
-					self.object:setvelocity({x = 0, y = -0.22, z = 1})
-				elseif v and vec.z-p.z < 0 then
-					self.object:setacceleration({x = 0, y = 0, z = 0})
-					self.object:setvelocity({x = 0, y = -0.22, z = -1})
-				end
-
-				self.object:setacceleration({x = 0, y = -10, z = 0})
-				self.physical_state = true
-				self.object:set_properties({
-					physical = true
-				})
-				return
-			end
-		end
-
-		p.y = p.y - 0.3
-		local nn = minetest.get_node(p).name
-		-- If node is not registered or node is walkably solid.
-		if not minetest.registered_nodes[nn] or minetest.registered_nodes[nn].walkable then
-			if self.physical_state then
-				self.object:setvelocity({x=0,y=0,z=0})
-				self.object:setacceleration({x=0, y=0, z=0})
-				self.physical_state = false
-				self.object:set_properties({
-					physical = false
-				})
-			end
-		else
-			if not self.physical_state then
-				self.object:setvelocity({x=0,y=0,z=0})
-				self.object:setacceleration({x=0, y=-10, z=0})
-				self.physical_state = true
-				self.object:set_properties({
-					physical = true
-				})
-			end
-		end
-
-		-- Eject if not walkable
-		local upnode = minetest.get_node({x = p.x, y = math.ceil(p.y), z = p.z}).name
-		if minetest.registered_nodes[upnode] and minetest.registered_nodes[upnode].walkable then
-			local minp, maxp = {x=p.x-1, y=math.ceil(p.y), z=p.z-1}, {x=p.x+1, y=math.ceil(p.y)+1, z=p.z+1}
-			local nodes = minetest.find_nodes_in_area(minp, maxp, unwalkable_nodes)
-			if table.getn(nodes) > 0 then
-				self.object:setpos(nodes[math.random(1,#nodes)])
-			end
-		end
-	end,
-	--[[ This causes a duplication glitch if a player walks upon an item and clicks on it at the same time.
-	on_punch = function(self, hitter)
-		if self.itemstring ~= "" then
-			local left = hitter:get_inventory():add_item("main", self.itemstring)
-			if not left:is_empty() then
-				self.itemstring = left:to_string()
-				return
-			end
-		end
-		self.object:remove()
-	end,
-	--]]
-})
-
-if minetest.setting_get("log_mods") then
-	minetest.log("action", "[builtin_item] loaded.")
+-- get_flow caches the results from get_flow_raw for 10 s
+local flow_cache = {}
+setmetatable(flow_cache, {__mode = "kv"})
+local function get_flow(pos)
+	local vi = minetest.hash_node_position(pos)
+	local t = minetest.get_us_time()
+	if flow_cache[vi]
+	and t - flow_cache[vi][1] < 10 * 1000000 then
+		return flow_cache[vi][2]
+	end
+	local flow = get_flow_raw(pos)
+	flow_cache[vi] = {t, flow}
+	return flow
 end
+
+local item_entity = minetest.registered_entities["__builtin:item"]
+local old_on_step = item_entity.on_step
+
+item_entity.makes_footstep_sound = true
+-- The "bt_" prefix shows that the value comes from builtin_item
+item_entity.bt_timer = 0
+item_entity.on_step = function(self, dtime, ...)
+	-- Remember the velocity before an original on_step can change it
+	local vel_desired
+	if self.bt_reset_velocity then
+		vel_desired = self.object:get_velocity()
+	end
+
+	old_on_step(self, dtime, ...)
+
+	-- Ignore the item if it should not interact with physics
+	if not self.physical_state then
+		return
+	end
+
+	-- Reset the velocity if needed
+	if vel_desired
+	and not vector.equals(self.object:get_velocity(), vel_desired) then
+		self.object:set_velocity(vel_desired)
+	end
+
+	-- For performance reasons, skip the remaining code in frequent steps
+	self.bt_timer = self.bt_timer + dtime
+	if self.bt_timer < 0.1 then
+		return
+	end
+	self.bt_timer = 0
+
+	local p = self.object:get_pos()
+	local pos = vector.round(p)
+	local nodename = minetest.get_node(pos).name
+
+	if self.bt_reset_velocity then
+		-- Set the item acceleration to its default (changed again below)
+		self.object:set_acceleration({x=0, y=-movement_gravity, z=0})
+		self.bt_reset_velocity = nil
+	end
+	local def = minetest.registered_nodes[nodename]
+	if not def or not def.liquidtype or def.liquidtype ~= "flowing" then
+		return
+	end
+	local flow = get_flow(pos)
+	if not flow then
+		return
+	end
+	local vel_current = vel_desired or self.object:get_velocity()
+	local acc
+	if vector.dot(vel_current, flow) < 1.0 then
+		acc = vector.multiply(flow, 2.0)
+	else
+		-- The item is already accelerated by the fluids
+		acc = {x = 0, y = 0, z = 0}
+	end
+	acc.y = -movement_gravity
+	self.object:set_acceleration(acc)
+	self.bt_reset_velocity = true
+end
+
+minetest.register_entity(":__builtin:item", item_entity)

mod.conf

@@ -0,0 +1 @@
+name = builtin_item