WPE Webkit for the RaspberryPi

This project provides an easy way of running WPE Webkit for the RaspberryPi. WPEWebkit is a full featured browser that takes advantage of the GPU to provide hardware accelerated CSS, WebGL, and HTML5 video.

Showcase

• Rendering WebGL abstract shapes
  • 
• Playing html5 flappy bird
  • 
• Playing HD video on YoutubeTV
  • 

Table of contents

• Table of contents
• Getting started
• Configuration
  • Displaying on an HDMI screen
  • Displaying on a PiTFT 2.8"
    • Capacitive touchscreen
    • Resistive touchscreen
  • Sound configuration
• Controlling content
  • Loading a URL
  • Offline content
  • Enabling mouse

Getting started

• 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
• git push balena master
• See the magic happening, your device is getting updated Over-The-Air!

Configuration

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. If you don't know how to do this, you can find more info here.

First, we need to set the GPU memory to something suitable for hardware accelerated graphics. You can set only one of the following if you know how much RAM your Pi has or you can set all of them and your Pi will autoselect based on its memory. If you don't set any of these, WPE won't work.

Key	Value
RESIN_HOST_CONFIG_gpu_mem_256	128
RESIN_HOST_CONFIG_gpu_mem_512	196
RESIN_HOST_CONFIG_gpu_mem_1024	396

Displaying on an HDMI screen

WPE will display to the primary framebuffer (HDMI output) by default. If you don't set the resolution, it will be autodetected on boot up. Depending on what you want to do, you might find the performance at FullHD resolution isn't enough. In that case you can force the HDMI to 720p by adding the following fleet configuration variables:

Key	Value
RESIN_HOST_CONFIG_hdmi_group	1
RESIN_HOST_CONFIG_hdmi_mode	4

Displaying on a PiTFT 2.8"

Displaying to a secondary framebuffer is accomplished by rendering on the primary and continuously copying the resulting image to the secondary. The reason for this is that the Pi can only render hardware accelerated graphics to the primary framebuffer. A side effect of this is that you can't display different content or have different resolutions between the HDMI and your PiTFT screen.

Since the rendering will happen to the primary framebuffer, we need to force the HDMI output to be 320x240, our native resolution. You can do this with the following variables. If don't set those, the Pi will render on a higher resolution and then scale down the image to fit the Pi screen.

Key	Value
RESIN_HOST_CONFIG_hdmi_force_hotplug	1
RESIN_HOST_CONFIG_hdmi_group	2
RESIN_HOST_CONFIG_hdmi_mode	87
RESIN_HOST_CONFIG_hdmi_cvt	320 240 60 1 0 0 0

Capacitive touchscreen

Warning: The PiTFT based on the ft6x06_ts kernel module is not currently supported out of the box on balena. If your screen says "FT6206" at the back, it's probably one of those.

Key	Value
RESIN_HOST_CONFIG_dtoverlay	pitft28-capacitive,rotate=90,speed=62000000,fps=60

Resistive touchscreen

Key	Value
RESIN_HOST_CONFIG_dtoverlay	pitft28-resistive,rotate=90,speed=62000000,fps=60

Controlling backlight brightness

If you have a Raspberry touchscreen, you can control the backlight brightness by setting the environment variable RPI_BACKLIGHT to a value in the range 0-255. The default value is 255 (maximum brightness).

Sound configuration

WPE will normally try to select an appropriate audio sink to output to. However, if you want to force a specific output to be used you can set the WPE_GSTREAMER_AUDIO_SINK environment variable according to the following table:

Value	Notes
autoaudiosink	Automatically select output (default)
omxhdmiaudiosink	Outputs sound over HDMI
omxanalogaudiosink	Outputs to the 3.5mm jack
alsasink	Outputs using alsa (EXPERIMENTAL)

Controlling content

Loading a URL

To configure the URL displayed by webkit, set the WPE_URL environment variable. The default value is Youtube TV

Offline content

If you want your device to display content even without internet, you can add your content in the docker image and point WPE 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"

Changing content at runtime

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

Enabling mouse

To enable the mouse cursor you have to set the following environment variable. Keep in mind that there are some known issues with mouse support when the webpage includes iframes.

Key	Value
WPE_BCMRPI_CURSOR	1