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https://github.com/balena-io-experimental/browser

A drop-in web browser block
https://github.com/balena-io-experimental/browser

balenablock browser chromium fincm3 generic-aarch64 intel-nuc jetson-nano raspberrypi3 raspberrypi3-64 raspberrypi4-64

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A drop-in web browser block

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# balena-labs-projects/browser



Provides a hardware accelerated web browser to present internal and external URLs on a connected display.

The `browser` block is a docker image that runs a [Chromium](https://www.chromium.org/Home) browser via X11, optimized for balenaOS.

The block provides an API for dynamic configuration, and also exposes the Chromium Remote Debug port.



---

## Features



- Chromium browser optimized for device arch

- Hardware video acceleration (if enabled)

- Optional KIOSK mode

- Remotely configurable launch URL

- Automatically displays local HTTP (port 80 or 8080) or HTTPS (443) service endpoints.

- API for remote configuration and management

- Chromium remote debugging port

---



## Usage



#### docker-compose file

To use this image, create a container in your `docker-compose.yml` file as shown below:



```yaml

version: '2'



volumes:

  settings:                          # Only required if using PERSISTENT flag (see below)



services:



  browser:

    image: bh.cr/balenalabs/browser- # where  is one of aarch64, arm32 or amd64

    privileged: true # required for UDEV to find plugged in peripherals such as a USB mouse

    ports:

        - '5011' # management API (optional)

        - '35173' # Chromium debugging port (optional)

    volumes:

      - 'settings:/data' # Only required if using PERSISTENT flag (see below)

```



To pin to a specific [version](CHANGELOG.md) of this block use:



```yaml

services:

  browser:

    image: bh.cr/balenalabs/browser-/

    privileged: true # required for UDEV to find plugged in peripherals such as a USB mouse

    ports:

        - '5011' # management API (optional)

        - '35173' # Chromium debugging port (optional)

    volumes:

      - 'settings:/data' # Only required if using PERSISTENT flag (see below)

```



See [here](https://github.com/balena-io/open-balena-registry-proxy#usage) for more details about how to use blocks hosted in balenaCloud.



---



## Customization

### Extend image configuration



By default the `browser` block uses the first local display (i.e. `DISPLAY=:0`) which would typically be a connected monitor, TV or a Pi Display. However for custom configurations you can overload the `CMD` directive, as such:



*dockerfile.template*

```Dockerfile

FROM bh.cr/balenalabs/browser-%%BALENA_ARCH%%



CMD ["export DISPLAY=:1"]

```

---



### Environment variables



The following environment variables allow configuration of the `browser` block:



| Environment variable | Options | Default | Description |

| --- | --- | --- | --- |

|`LAUNCH_URL`|`http` or `https` URL|N\A|Web page to display|

|`DISPLAY_NUM`|`n`|0|Display number to use|

|`LOCAL_HTTP_DELAY`|Number (seconds)|0|Number of seconds to wait for a local HTTP service to start before trying to detect it|

|`KIOSK`|`0`, `1`|`0`|Run in kiosk mode with no menus or status bars. 
 `0` = off, `1` = on|

|`SHOW_CURSOR`|`0`, `1`|`0`|Enables/disables the cursor when in kiosk mode
 `0` = off, `1` = on|

|`FLAGS`|[many!](https://peter.sh/experiments/chromium-command-line-switches/)|N/A|**Replaces** the flags chromium is started with. Enter a space (\' \') separated list of flags (e.g. `--noerrdialogs --disable-session-crashed-bubble`) 
 **Use with caution!**|

|`EXTRA_FLAGS`|[many!](https://peter.sh/experiments/chromium-command-line-switches/)|N/A|Adds **additional** flags chromium is started with. Enter a space (\' \') separated list of flags (e.g. `--audio-buffer-size=2048 --audio-output-channels=8`)|

|`PERSISTENT`|`0`, `1`|`0`|Enables/disables user profile data being stored on the device. **Note: you'll need to create a settings volume. See example above** 
 `0` = off, `1` = on|

|`ROTATE_DISPLAY`|`normal`, `left`, `right`, `inverted`|`normal`|Rotates the display|

|`ROTATE_DELAY`|`n`|`3`|Add an artificial delay (in seconds) before applying display rotation|

|`TOUCHSCREEN`|`string`|N\A|Name of Touch Input to rotate|

|`ENABLE_GPU`|`0`, `1`|0|Enables the GPU rendering. Necessary for Pi3B+ to display YouTube videos. 
 `0` = off, `1` = on|

|`WINDOW_SIZE`|`x,y`|Detected screen resolution|Sets the browser window size, such as `800,600`. 
 **Note:** Reverse the dimensions if you also rotate the display to `left` or `right` |

|`WINDOW_POSITION`|`x,y`|`0,0`|Specifies the browser window position on the screen|

|`API_PORT`|port number|5011|Specifies the port number the API runs on|

|`REMOTE_DEBUG_PORT`|port number|35173|Specifies the port number the chrome remote debugger runs on|

|`AUTO_REFRESH`|interval|0 (disabled)|Specifies the number of seconds before the page automatically refreshes|



---



## Choosing what to display

If you want the `browser` to display a website, you can set the `LAUNCH_URL` as noted above. However, you can also drop the `browser` into a multicontainer app, and use it to display the (HTTP, port 80 or 8080, or HTTPS port 443) output of another service, such as a Grafana dashboard. The `browser` will automatically detect that a service is running a HTTP server  and display that. Just make sure that you don't set a `LAUNCH_URL` environment variable, as they take precedence. Example:



*docker-compose.yml*

```yaml

version: '2.1'

volumes:

  settings:

services:

  browser:

    restart: always

    image: bh.cr/balenalabs/browser-

    privileged: true

    volumes:

      - 'settings:/data'

  grafana:

    restart: always

    build: ./grafana

    ports:

      - "80"

```

---



## Choosing audio output device

By default the `browser` block will output audio via HDMI. If you want to route audio through a different interface you can do it with the help of the [`audio` block]((https://github.com/balena-labs-projects/audio)). The `browser` block is pre-configured to use it if present so you only need to add it to your `docker-compose.yml` file and then use `AUDIO_OUTPUT` environment variable to select the desired output. Check out the `audio` block [documentation](https://github.com/balena-labs-projects/audio#environment-variables) to learn more about it.



In this example we add the `audio` block and route the `browser` audio to the Raspberry Pi headphone jack:



```yaml

services:

  browser:

    image: bh.cr/balenalabs/browser-

  audio:

    image: bh.cr/balenalabs/audio-

    privileged: true

    ports:

      - 4317:4317

    environment:

      AUDIO_OUTPUT: RPI_HEADPHONES

```



**Note**: The `browser` block expects the `audio` block to be named as such. If you change it's service name you'll need to override the `PULSE_SERVER` environment variable value to match it in the `browser` dockerfile. For example add `ENV PULSE_SERVER=tcp:not-audio:4317`.



---



## API

The `browser` block exposes an HTTP API running on port 5011. The following endpoints are available:



#### **GET** /ping

Returns HTTP 200 if the `browser` block is ready



#### **POST** /refresh

Refreshes the currently displayed page



#### **POST** /autorefresh/{interval}

Automatically refreshes the browser window



| Value | Description |

|--------------|-------------|

| 0 | disable |

| 1-60 | refresh every `interval` seconds |



#### **POST** /scan

Re-scans the device to find local HTTP or HTTPS services to display. This can be used by the HTTP/S service to notify the `browser` block that it is ready to be displayed, should there be a startup race.



note: *the* `LAUNCH_URL` *must not be set for local services to be detected.*



#### **GET** /url

Returns the URL currently being displayed



#### **PUT** /url

Sets the URL to be displayed. The URL is set in the request body. Example:



```bash

curl --data "url=www.balena.io" http://localhost:5011/url

```



You can also pre-set the kiosk and GPU settings as part of a URL put request. Example:



```bash

curl --data "url=www.balena.io&gpu=0&kiosk=1" http://localhost:5011/url

```



#### **GET** /gpu

Returns the status of the GPU:



| Return Value | Description |

|--------------|-------------|

| 0 | disabled |

| 1 | enabled |



#### **PUT** /gpu/{value}

Enables or disables the GPU



| Value | Description |

|--------------|-------------|

| 0 | disable |

| 1 | enable |



#### **GET** /kiosk

Returns whether the device is running kiosk mode or not:



| Return Value | Description |

|--------------|-------------|

| 0 | disabled |

| 1 | enabled |



#### **PUT** /kiosk/{value}

Enables or disables kiosk mode



| Value | Description |

|--------------|-------------|

| 0 | disable |

| 1 | enable |



#### **GET** /flags

Returns the flags Chromium was started with



#### **GET** /version

Returns the version of Chromium that `browser` is running



#### **GET** /screenshot

Uses [scrot](https://opensource.com/article/17/11/taking-screen-captures-linux-command-line-scrot) to take a screenshot of the chromium window. 

The screenshot will be saved as a temporary file in the container.



---



## Supported devices

The `browser` block has been tested to work on the following devices:



| Device Type  | Status |

| ------------- | ------------- |

| Raspberry Pi 3b+ | ✔ |

| Raspberry Pi 3b+ (64-bit OS) | ✔ |

| balena Fin | ✔ |

| Raspberry Pi 4 | ✔ |

| Intel NUC | ✔ |

| Generic AMD64 | ✔ |



---



## Troubleshooting

This section provides some guidance for common issues encountered:



#### Black border on HDMI display

Thanks to 1980's CRT televisions, manufacturers had to invent a method for cutting off the edges of a picture to ensure the "important" bits were displayed nicely on the screen. This is called `overscan` and there's a good article on it [here](https://www.howtogeek.com/252193/hdtv-overscan-what-it-is-and-why-you-should-probably-turn-it-off/).

If, when you plug one of the supported devices into your HDMI screen, you find black borders around the picture, you need to disable overscan. For the device this can be achieved by setting a [Device Configuration variable](https://www.balena.io/docs/learn/manage/configuration/#:~:text=Define%20fleet%2Dwide%3A-,Managing%20device%20configuration%20variables,of%20the%20device%20configuration%20variable.) called `BALENA_HOST_CONFIG_disable_overscan` and setting the value to `1`:



![overscan-setting](https://i.ibb.co/sCQ8Dwy/Capture.jpg)



You may also need to turn it off on the screen itself (check your device instructions for details).



#### Partial/strange display output

Occasionally users report weird things are happening with their display output like:

* Only a portion of the browser screen appears on their display

* The screen is displaying skewed or fragmented

* Colors have changed dramatically



Here are some things to try:

* Setting the WINDOW_SIZE manually to your display's resolution (e.g. `1980,1080`) - the display may be mis-reporting it's resolution to the device

* Increase the memory being allocated to the GPU with the Device Configuration tab on the dashboard, or via [configuration variable](https://www.balena.io/docs/learn/manage/configuration/) - for large displays the device may need to allocate more memory to displaying the output