balenaBlocks electron

This is work in progress

What

Provides stuff that may be missing when running electron apps in kiosk mode (with no desktop environment):

• a wifi configuration dialog
• a file picker
• an on-screen keyboard (onboard)
• a dialog for mounting / umounting removable drives

Building

Build and upload this project's docker images ./image-builder.sh;

Using

• In your electron app project create a Dockerfile that uses this project: FROM balenablocks/aarch64-balena-electron-env, replace aarch64 with the architecture you need (aarch64, armv7hf or amd64);
• Put your electron app in /usr/src/app in this Dockerfile.

This works by running a window manager (metacity for now), dbus, an on-screen keyboard (onboard) and requiring some js code before your application.

The required js code replaces the file picker, adds buttons for opening the additional dialogs and injects some javascript in each window to summon the on-screen keyboard when an input is focused.

Components

Wifi configuration

Works by communicating with NetworkManager via DBus.

File picker

Replaces the default electron gtk file picker, can be constrained with BALENAELECTRONJS_CONSTRAINT_PATH.

On-screen keyboard

onboard is summoned via the session dbus each time an input is focused.

Mounting / umounting of removable drives

Watches and allows to mount / umount removable drives in BALENAELECTRONJS_MOUNTS_ROOT.

Environment variables:

Name	Description	Default Value
BALENAELECTRONJS_MOUNTS_ROOT	Where the removable drives should be mounted	/tmp/media
BALENAELECTRONJS_CONSTRAINT_PATH	Only files in this path will be accessible through the file picker
BALENAELECTRONJS_OVERLAY_DELAY	Delay before showing the overlay icons	200
BALENAELECTRONJS_REMOTE_DEBUGGING_PORT	Enable electron remote debugging on this port
BALENAELECTRONJS_SLEEP_BUTTON_POSITION	Sleep button position: x,y
BALENAELECTRONJS_WIFI_BUTTON_POSITION	Wifi button position: x,y
BALENAELECTRONJS_SETTINGS_BUTTON_POSITION	Settings button position: x,y
BALENAELECTRONJS_MOUNTS_BUTTON_POSITION	Mounts button position: x,y
BALENAELECTRONJS_SCREENSAVER_ON_COMMAND	Shell command to run when the screensaver is turned on
BALENAELECTRONJS_SCREENSAVER_OFF_COMMAND	Shell command to run when the screensaver is turned off
BALENAELECTRONJS_UPDATES_ONLY_DURING_SCREENSAVER	Only allows application updates to happen while the screensaver is on if set
BALENAELECTRONJS_SCREENSAVER_DELAY_OVERRIDE	Overrides the screensaver delay from the settings: number in minutes or 'never'
BALENAELECTRONJS_ZOOM_FACTOR	Zoom factor for overlay windows size and position	1
DBUS_SYSTEM_BUS_ADDRESS	DBus address for communicating with NetworkManager	unix:path=/host/run/dbus/system_bus_socket
XRANDR_ARGS	Rotate the screen with xrandr $XRANDR_ARGS, example: "-o inverted -x"

Remote methods:

Call them with electron.ipcRenderer.invoke(methodName, ...parameters) from any renderer process.

Name	Parameters	Description
mount-drive	drivePath: string	Mounts all partitions of the drive, drivePath is the name of the drive in /dev/disk/by-path/
disable-screensaver		Disables the screensaver, does not change the sleepDelay setting
enable-screensaver		Enables the screensaver, does not change the sleepDelay setting

Utilities

• clicklock is available in /usr/bin/clicklock and will be run when the screensaver goes on