PlayMinetestServer/mods/unified_inventory/item_names.lua

-- Based on 4itemnames mod by 4aiman

local item_names = {} -- [player_name] = { hud, dtime, itemname } 
local dlimit = 3  -- HUD element will be hidden after this many seconds
local air_hud_mod = minetest.get_modpath("4air")
local hud_mod = minetest.get_modpath("hud")
local hudbars_mod = minetest.get_modpath("hudbars")

local function set_hud(player)
	local player_name = player:get_player_name()
	local off = {x=0, y=-70}
	if air_hud_mod or hud_mod then
		off.y = off.y - 20
	elseif hudbars_mod then
		off.y = off.y + 13
	end
	item_names[player_name] = {
		hud = player:hud_add({
			hud_elem_type = "text",
			position = {x=0.5, y=1},
			offset = off,
			alignment = {x=0, y=0},
			number = 0xFFFFFF,
			text = "",
		}),
		dtime = dlimit,
		index = 1,
		itemname = ""
	}
end

minetest.register_on_joinplayer(function(player)
	minetest.after(0, set_hud, player)
end)

minetest.register_on_leaveplayer(function(player)
	item_names[player:get_player_name()] = nil
end)

minetest.register_globalstep(function(dtime)
	for _, player in pairs(minetest.get_connected_players()) do
		local data = item_names[player:get_player_name()]
		if not data or not data.hud then
			data = {} -- Update on next step
			set_hud(player)
		end

		local index = player:get_wield_index()
		local stack = player:get_wielded_item()
		local itemname = stack:get_name()

		if data.hud and data.dtime < dlimit then
			data.dtime = data.dtime + dtime
			if data.dtime > dlimit then
				player:hud_change(data.hud, 'text', "")
			end
		end

		if data.hud and (itemname ~= data.itemname or index ~= data.index) then
			data.itemname = itemname
			data.index = index
			data.dtime = 0

			local desc = stack.get_meta
				and stack:get_meta():get_string("description")

			if not desc or desc == "" then
				-- Try to use default description when none is set in the meta
				local def = minetest.registered_items[itemname]
				desc = def and def.description or ""
			end
			player:hud_change(data.hud, 'text', desc)
		end
	end
end)