Real-time reactivity

Principle

LastMenu integrates a polling engine that monitors functions declared in your builders. When the returned value changes, a minimal patch is sent to the NUI — no global re-render, no menu close/reopen.

No Citizen.Wait(0) loop is needed in your code.

---

Dynamic label

Pass a function as button label for real-time updates:

local startTime = GetGameTimer()

UI:context(function(menu)
    menu:title("Live information")

    -- Updated every second
    menu:button(function()
        local elapsed = math.floor((GetGameTimer() - startTime) / 1000)
        return string.format("Open for: %ds", elapsed)
    end, { refresh = 1000 })

    -- Shows player's money
    menu:button(function()
        return "Balance: " .. GetPlayerMoney(PlayerId()) .. " €"
    end, { refresh = 500 })
end)

---

Reactive visibility

-- Visible only if player is in a vehicle
menu:button("Set cruise control", {
    icon    = "gauge",
    visible = function()
        return GetVehiclePedIsIn(PlayerPedId(), false) ~= 0
    end,
    refresh = 250,
    cb      = function() end,
})

---

Reactive disabling

-- Disabled during cooldown
local lastUse = 0

menu:button("Use item", {
    icon     = "package",
    disabled = function()
        return (GetGameTimer() - lastUse) < 10000
    end,
    refresh = 250,
    cb      = function()
        lastUse = GetGameTimer()
        -- ...
    end,
})

---

The refresh property

refresh (ms) controls the evaluation frequency of watcher functions.

Field	Default	Minimum recommended
label (function)	500ms	100ms
visible	250ms	100ms
disabled	250ms	100ms
stat.value	500ms	100ms

Going below 100ms is possible but not useful — NUI only displays at ~60 FPS.

---

Reactive stat values

The value and max properties of a stat item accept functions:

menu:stat("Health", {
    value   = function() return GetEntityHealth(PlayerPedId()) - 100 end,
    max     = 100,
    icon    = "heart",
    suffix  = "hp",
    refresh = 500,
})

menu:stat("Engine", {
    value   = function()
        local veh = GetVehiclePedIsIn(PlayerPedId(), false)
        return veh ~= 0 and GetVehicleEngineHealth(veh) / 10 or 0
    end,
    max     = 100,
    icon    = "activity",
    suffix  = "%",
    refresh = 1000,
})

---

Watcher Safe Mode

If a watcher function throws an error 3 times in a row, LastMenu enters Safe Mode for that watcher:

1. The watcher is disabled for 15 seconds.
2. An alert message is printed to console: [LastMenu] Watcher DISABLED ....
3. After 15s, a recovery attempt is made.
4. If the error persists, the watcher is disabled again.

Symptom: a button’s visible/disabled state stops updating, briefly updates, then stops again.

Diagnostic : active Config.debug = true ou exécute /lm_debug pour voir les stats des watchers.

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Anti-pattern : retourner une table

Attention : une fonction watcher qui retourne une table au lieu d’un primitif envoie un patch NUI à chaque tick, car la comparaison de tables utilise l’égalité de référence.

-- MAUVAIS : nouvelle table à chaque tick → patches constants
menu:button('Statut', {
    disabled = function()
        return { locked = isLocked() }  -- table, pas un booléen
    end,
})

-- CORRECT : retourne un primitif
menu:button('Statut', {
    disabled = function() return isLocked() end,
})

LastMenu affiche un avertissement console unique quand ce pattern est détecté.

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Mécanisme interne

1. Le watcher évalue la fonction de label / valeur.
2. Si le résultat diffère de la dernière valeur connue, un patch est construit.
3. Le patch est envoyé via Bridge.send({ type='patch', id, changes={...} }).
4. App.svelte l’applique en O(1) via une Map indexée par item id — pas de re-render global.

Les watchers démarrent à chaque open() d’un menu réutilisable et s’arrêtent à la fermeture.