---
title: Timer
description: Timer element api.
---
import SlintProperty from '@slint/common-files/src/components/SlintProperty.astro';

:::note[Note]
Timer is not an actual element visible in the tree, therefore it doesn't have the common properties such as `x`, `y`, `width`, `height`, etc. It also doesn't take room in a layout and cannot have any children or be inherited from.
:::

This example shows a timer that counts down from 10 to 0 every second:

```slint playground
import { Button } from "std-widgets.slint";
export component Example inherits Window {
    property <int> value: 10;
    timer := Timer {
        interval: 1s;
        running: true;
        triggered() => {
            value -= 1;
            if (value == 0) {
                self.running = false;
            }
        }
    }
    HorizontalLayout {
        Text { text: value; }
        Button {
            text: "Reset";
            clicked() => { value = 10; timer.running = true; }
        }
    }
}
```



Use the Timer pseudo-element to schedule a callback at a given interval.
The timer is only running when the `running` property is set to `true`. To stop or start the timer, set that property to `true` or `false`.
It can be also set to a binding expression.
When already running, the timer will be restarted if the `interval` property is changed.

:::caution[Caution]
By default the `Timer` is always running `running: true`. This can result in constant CPU usage and
power usage so ensure that you set `running` to `false` when you don't want the timer to run.
:::

```slint
property <int> count: 0;
Timer {
    interval: 8s; // every 8 seconds the timer will activate (tick)
    triggered() => { // The triggered callback activates every time the timer ticks
        if count >= 5 {
            self.running = false; // stop the timer after 5 ticks
        }
        count += 1;
    }
}
```

## Properties

### interval
<SlintProperty propName="interval" typeName="duration">
The interval between timer ticks. This property is mandatory.
```slint "interval: 250ms;"
Timer {
    property <int> count: 0;
    interval: 250ms;
    triggered() => {
        debug("count is:", count);
        count += 1;
    }
}
```
</SlintProperty>

### running
<SlintProperty propName="running" typeName="bool" defaultValue="true">
`true` if the timer is running.
```slint "running: false; // timer is not running"
Timer {
    property <int> count: 0;
    interval: 250ms;
    running: false; // timer is not running
    triggered() => {
        debug("count is:", count);
    }
}
```
</SlintProperty>

## Callbacks

### triggered()
Invoked every time the timer ticks (every `interval`).
```slint {4-6}
Timer {
    property <int> count: 0;
    interval: 250ms;
    triggered() => {
        debug("count is:", count);
    }
}
```

## Functions

### start()
Start the timer (equivalent to setting `running` to true).

### stop()
Stop the timer (equivalent to setting `running` to false).

### restart()
Restarts the timer if it was previously started.