WPE Webkit for the RaspberryPi

Project Status: No Longer Under Active Development

This project was an experiment to integrate WPE into the Balena Hub.
It is not currently actively developed or maintained. The current version available from Balena Hub does not reflect the most recent advancements or patches in the WPE ecosystem.

If an up to date Balena block is very important to you, we'd be very interested to hear more. Meanwhile, if you encounter issues or are seeking updates, we recommend exploring alternative solutions or resources that align with your requirements.

Should you have any further questions or inquiries, please feel free to get in touch.

Description

This project uses 3 different balena blocks:

• balena WPE
• balena Weston
• balena Audio

It provides a Web based screen display running on WPE WebKit. Contrary to other solutions, this project runs the browser on the top of a Wayland compositor (Weston).

Weston aims to be a lean, fast and predictable Wayland compositor. It provides a full-featured environment for non-desktop applications what eventually can run a Web browser such as automotive, embedded, in-flight, industrial, kiosks, set-top boxes and TVs.

WPE WebKit allows embedders to create simple and performant systems based on Web platform technologies. It is a WebKit port designed with flexibility and hardware acceleration in mind, leveraging common 3D graphics APIs for best performance.

Pulse Audio provides all the audio support required for the containerized browser.

Table of contents

• Table of contents
• Hardware requirements
• Getting started
  • Fork the balena-wpe Project and create your own Fleet
• Content Load
  • Changing content at runtime
  • Offline content
• Settings
  • RaspberryPi config-txt settings
  • Browser settings
  • Sound settings
  • Useful environment variables for debugging
• Showcases
• Development
  • Semantic commits

Hardware requirements

• Raspberry Pi 3/4
• SD card
• HDMI TV or Monitor
• Keyboard, mouse or a Touchscreen

Getting started

Fork the balena-wpe project and create your own fleet

• Sign up on balena
• Go through the getting started guide and create a new application
• Clone this repository to your local workspace
• Add the balena remote to your local workspace using the useful shortcut in the dashboard UI remoteadd
• git push balena master
• Your device will be updated Over-The-Air

Content Load

The URL displayed by the browser launcher can be set using the WPE_URL environment variable. The default value is wpewebkit.org

Environment variable	Default	Example
WPE_URL	https://wpewebkit.org	https://igalia.com

Changing content at runtime

balena-browser-wpe ships with tohora, which provides a web interface for changing target URLs at runtime on port 8080.

Offline content

If you want your device to display content even without internet, you can add your content in the docker image and point the browser to them. Append a similar Dockerfile fragment to your project:

COPY public_html /var/lib/public_html

ENV WPE_URL="file:///var/lib/public_html/index.html"

Settings

RaspberryPi config-txt settings

A lot of the configuration of this project is about setting up config.txt. The way you do this on balena is by setting some special fleet configuration variables.

How to set the config.txt is pretty well documented in the RaspberryPi official documentation. You can overwrite these settings in the balena dashboard setting variables in your environment using the prefix RESIN_HOST_CONFIG_. Read more.

Probably you will be interested in setting the GPU memory to a more suitable value for hardware accelerated graphics.

Key	Value
RESIN_HOST_CONFIG_gpu_mem_256	128
RESIN_HOST_CONFIG_gpu_mem_512	196
RESIN_HOST_CONFIG_gpu_mem_1024	396

Browser settings

Environment variable	Options	Default	Description
WPE_COG_PLATFORM_FDO_VIEW_FULLSCREEN	0, 1	1	Enables the fullscreen mode in the browser screen
WPE_COG_PLATFORM_FDO_VIEW_HEIGHT	integer	720	Vertical resolution
WPE_COG_PLATFORM_FDO_VIEW_WIDTH	integer	1280	Horizontal resolution
WPE_COG_RELAUNCH	0, 1	unset	Enables forcing relaunch of the browser
WPE_COG_RELAUNCH_DELAY	integer	5	Add delay during forced relaunch

By setting WPE_ENABLE_INSPECTOR_SERVER to on you can connect to the Web browser inspector server in the board by loading the following URL inspector://<raspberrypi IP>:12321 in an Epiphany Browser.

Environment variable	Options	Default	Description
WPE_ENABLE_INSPECTOR_SERVER	0,1	0	Enables the Web Inspector

Alternatively you can use docker-libwebkit2gtk to use the remote Web Inspector.

export URL="inspector://<your raspberrypi IP>:12321"
export XAUTHORITY="/run/user/1000/gdm/Xauthority"  # or "xhost +"

cd docker-libwebkit2gtk
sudo -E ./run.sh
URL: inspector://192.168.1.170:12321
Sending build context to Docker daemon  81.92kB
...
Opening URL: inspector://192.168.1.170:12321

Compositor settings

The browser relies on the Weston compositor to work. While the defaults are fine for most uses, some tweaks are allowed regarding the output resolution.

Environment variable	Options	Default	Description
WPE_WESTON_SHELL	string	desktop	The shell to use (desktop, fullscreen, kiosk etc.)
WPE_WESTON_OUTPUT_USE_CURRENT_MODE	0, 1	0	Inherit the display mode from KMS console
WPE_WESTON_OUTPUT_MAX_WIDTH	integer	0	Maximum horizontal resolution the compositor may set
WPE_WESTON_OUTPUT_MAX_HEIGHT	integer	0	Maximum vertical resolution the compositor may set

The maximum-resolution environment variables rely on the list of modes advertised by the DRM subsystem. That means if you set for example the maximum horizontal resolution to 1920 and the list contains 3840x2160, 2560x1440, 1920x1080 and 1280x800, 1920x1080 will be picked.

The shell used will be ${WPE_WESTON_SHELL}-shell.so. You can use any shell shipped with Weston by default.

Sound settings

balena-browser-wpe relies on balena-audio for the audio processing. Check the specific settings of this block for audio settings.

Alternatively the block can be also configured to route the audio through another Pulser Server by setting the PULSE_SERVER environment variable.

Environment variable	Options	Default
WPE_PULSE_SERVER	unix:/run/pulse/pulseaudio.socket, tcp:audio:4317	unix:/run/pulse/pulseaudio.socket

Useful environment variables for debugging

Environment variable	Example	Description
EGL_LOG_LEVEL	debug	Change the log level of the main library and the drivers in Mesa
GALLIUM_HUD	load+cpu+fps	Activate and set the Gallium3D Heads-Up Display
GST_DEBUG	*:DEBUG	Set the log level output in GStreamer
G_MESSAGES_DEBUG	all	Set the log level output in GLib
LIBGL_DEBUG	verbose	If defined Mesa LibGL debug information will be printed to stderr. If set to verbose additional information will be printed
MESA_DEBUG	1	If set to 1 Mesa error messages are printed to stderr
WAYLAND_DEBUG	1	If set to 1 the Wayland debug output is printed to stderr

Environment variable	Options	Default	Description
CPU_SCALING_GOVERNOR	options	performance	Scaling governors

Showcases

• CSS transformation and animations in WebKit poster circle example
  • 
• Playing an embedded Youtube video
  • 
• Playing Bouncyballs
  • 
• Rendering WebGL Aquarium and Abstract shapes
  • 
  • 

Development

Semantic commits

• Install:

  sudo apt install npm
  sudo -E npm install -g versionist
  sudo -E npm install -g balena-versionist

• Add commits with semantic format:

  Semantic description of the change
  
  ...Details ...
  
  Change-Type: <type>  # major, minor or patch
  

• Update the changelog:

  balena-versionist
  

• Commit the changes in balena.yml, VERSION and CHANGELOG.md to generate a release using the vX.X.X format in the commit message.