minetest_game/mods/binoculars/init.lua

-- binoculars/init.lua

-- Mod global namespace

binoculars = {}

-- Load support for MT game translation.
local S = minetest.get_translator("binoculars")


-- Update player property
-- Global to allow overriding

function binoculars.update_player_property(player)
	local new_zoom_fov = 0

	if player:get_inventory():contains_item(
			"main", "binoculars:binoculars") then
		new_zoom_fov = 10
	elseif minetest.is_creative_enabled(player:get_player_name()) then
		new_zoom_fov = 15
	end

	-- Only set property if necessary to avoid player mesh reload
	if player:get_properties().zoom_fov ~= new_zoom_fov then
		player:set_properties({zoom_fov = new_zoom_fov})
	end
end


-- Set player property 'on joinplayer'

minetest.register_on_joinplayer(function(player)
	binoculars.update_player_property(player)
end)


-- Cyclic update of player property

local function cyclic_update()
	for _, player in ipairs(minetest.get_connected_players()) do
		binoculars.update_player_property(player)
	end
	minetest.after(4.7, cyclic_update)
end

minetest.after(4.7, cyclic_update)


-- Binoculars item

minetest.register_craftitem("binoculars:binoculars", {
	description = S("Binoculars") .. "\n" .. S("Use with 'Zoom' key"),
	inventory_image = "binoculars_binoculars.png",
	stack_max = 1,
	groups = {tool = 1},

	on_use = function(itemstack, user, pointed_thing)
		binoculars.update_player_property(user)
	end,
})


-- Crafting

minetest.register_craft({
	output = "binoculars:binoculars",
	recipe = {
		{"default:obsidian_glass", "", "default:obsidian_glass"},
		{"default:bronze_ingot", "default:bronze_ingot", "default:bronze_ingot"},
		{"default:obsidian_glass", "", "default:obsidian_glass"},
	}
})