# Progress Bar in Taskbar (Windows, macOS, Unity)

## Overview

A progress bar enables a window to provide progress information to the user
without the need of switching to the window itself.

On Windows, you can use a taskbar button to display a progress bar.

![Windows Progress Bar][windows-progress-bar]

On macOS, the progress bar will be displayed as a part of the dock icon.

![macOS Progress Bar][macos-progress-bar]

On Linux, the Unity graphical interface also has a similar feature that allows
you to specify the progress bar in the launcher.

![Linux Progress Bar][linux-progress-bar]

> NOTE: on Windows, each window can have its own progress bar, whereas on macOS
and Linux (Unity) there can be only one progress bar for the application.

----

All three cases are covered by the same API - the
[`setProgressBar()`][setprogressbar] method available on an instance of
`BrowserWindow`. To indicate your progress, call this method with a number
between `0` and `1`. For example, if you have a long-running task that is
currently at 63% towards completion, you would call it as
`setProgressBar(0.63)`.

Setting the parameter to negative values (e.g. `-1`) will remove the progress
bar, whereas setting it to values greater than `1` (e.g. `2`) will switch the
progress bar to indeterminate mode (Windows-only -- it will clamp to 100%
otherwise). In this mode, a progress bar remains active but does not show an
actual percentage. Use this mode for situations when you do not know how long
an operation will take to complete.

See the [API documentation for more options and modes][setprogressbar].

## Example

Starting with a working application from the
[Quick Start Guide](quick-start.md), add the following lines to the
`main.js` file:

```javascript
const { BrowserWindow } = require('electron')
const win = new BrowserWindow()

win.setProgressBar(0.5)
```

After launching the Electron application, you should see the bar in
the dock (macOS) or taskbar (Windows, Unity), indicating the progress
percentage you just defined.

![macOS dock progress bar](../images/dock-progress-bar.png)

For macOS, the progress bar will also be indicated for your application
when using [Mission Control](https://support.apple.com/en-us/HT204100):

![Mission Control Progress Bar](../images/mission-control-progress-bar.png)

[windows-progress-bar]: https://cloud.githubusercontent.com/assets/639601/5081682/16691fda-6f0e-11e4-9676-49b6418f1264.png
[macos-progress-bar]: ../images/macos-progress-bar.png
[linux-progress-bar]: ../images/linux-progress-bar.png
[setprogressbar]: ../api/browser-window.md#winsetprogressbarprogress-options
