luanti/builtin/game/item_entity.lua

-- Minetest: builtin/item_entity.lua

function core.spawn_item(pos, item)
	-- Take item in any format
	local stack = ItemStack(item)
	local obj = core.add_entity(pos, "__builtin:item")
	obj:get_luaentity():set_item(stack:to_string())
	return obj
end

core.register_entity(":__builtin:item", {
	initial_properties = {
		hp_max = 1,
		physical = true,
		collide_with_objects = false,
		collisionbox = {-0.17,-0.17,-0.17, 0.17,0.17,0.17},
		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,
	},
	
	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 core.registered_items[itemname] then
			item_texture = core.registered_items[itemname].inventory_image
			item_type = core.registered_items[itemname].type
		end
		prop = {
			is_visible = true,
			visual = "sprite",
			textures = {"unknown_item.png"}
		}
		if item_texture and item_texture ~= "" then
			prop.visual = "sprite"
			prop.textures = {item_texture}
			prop.visual_size = {x=0.50, y=0.50}
		else
			prop.visual = "wielditem"
			prop.textures = {itemname}
			prop.visual_size = {x=0.20, y=0.20}
			prop.automatic_rotate = math.pi * 0.25
		end
		self.object:set_properties(prop)
	end,

	get_staticdata = function(self)
		--return self.itemstring
		return core.serialize({
			itemstring = self.itemstring,
			always_collect = self.always_collect,
		})
	end,

	on_activate = function(self, staticdata)
		if string.sub(staticdata, 1, string.len("return")) == "return" then
			local data = core.deserialize(staticdata)
			if data and type(data) == "table" then
				self.itemstring = data.itemstring
				self.always_collect = data.always_collect
			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)
		local p = self.object:getpos()
		p.y = p.y - 0.3
		local nn = core.get_node(p).name
		-- If node is not registered or node is walkably solid and resting on nodebox
		local v = self.object:getvelocity()
		if not core.registered_nodes[nn] or core.registered_nodes[nn].walkable and v.y == 0 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
	end,

	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.itemstring = ''
		self.object:remove()
	end,
})