Nov 13

Nov 13 Right Clicky-Click on the RasPad. Twofing and Two-Finger Gestures for the Mouse

A couple of days ago, someone stole my phone on the train. It was awful, and I’m still wondering where my poor OnePlus went. Is it in the trash? Was it sold to a pawn shop?

After thinking for a bit, i decided to use a Nokia 3310 as my daily driver and build a RasPad for most of the other webby-stuff. The biggest issue I was facing was the lack of a right-click. So began the trek…

I tried using Twofing, which is the classic method of getting right click to work on a touchscreen with a Raspberry Pi. The main problem is that the RasPad is a little different compared to the official Pi 7” display. Some tinkering was in order. I present my fork of Twofing. The source code can be found on my Github Page.

Twofing Redux for RasPad

Twofing is originally a package by Plippo that monitors for a two-finger touch on the desktop. Once that is detected, a right-click is emulated. Sjlongland did a ton of work to get this debian package work in place.

This fork is written to add compatibility with the RasPad and its ILITEK touchscreen. By installing this, several things will happen:

new udev rules will be added for this display
new xorg InputClass created for the RasPad display with some default values for calibration. (see calibration below)
the twofing program will be placed into /usr/bin
twofing is set up to be managed by systemd

There are a few other small changes, including a fix for reading input from device ID.

Building

Use the package manager to install Twofing. Either use the .deb release, or compile from the source here.

To do that, you need to follow a few steps first. Install a few prerequisites so that twofing can both be built and function:

sudo apt-get update

sudo apt-get install \
build-essential libx11-dev libxi-dev x11proto-randr-dev \
libxrandr-dev libxtst-dev xserver-xorg-input-evdev \
libinput-tools dh-systemd debhelper xinput-calibrator

Once the dependencies and other things are installed, you can build the package with dpkg-buildpackage. Enter the source directory and use:

dpkg-buildpackage -us -uc -b -tc

This will churn for a bit. a lot of output will be displayed as the program is being built. If all ends well, you should see something like this:

dpkg-buildpackage: info: binary-only upload (no source included)

Check your user's home directory for the completed .deb package.

Installing

Installation is pretty straightforward and with little fanfare.

dpkg -i twofing_0.7.2_armhf.deb

Once again, there will be some output here. Systemd should announce that it is linking the service for startup.

pi@raspberrypi:/home/pi $ sudo dpkg -i /home/pi/twofing_0.7.2_armhf.deb
Selecting previously unselected package twofing.
(Reading database ... 161748 files and directories currently installed.)
Preparing to unpack .../pi/twofing_0.7.2_armhf.deb ...
Unpacking twofing (0.7.2) ...
Setting up twofing (0.7.2) ...
Created symlink /etc/systemd/system/multi-user.target.wants/twofing.service → /etc/systemd/system/twofing.service.

Now systemctl should return the status of twofing.service:

pi@raspberrypi:/etc/udev/rules.d $ systemctl status twofing.service
● twofing.service - Twofing Rightclick service
   Loaded: loaded (/etc/systemd/system/twofing.service; enabled; vendor preset: enabled)
   Active: active (running) since Tue 2019-11-12 23:40:59 PST; 2min 8s ago
 Main PID: 1973 (twofing)
    Tasks: 1 (limit: 4915)
   CGroup: /system.slice/twofing.service
           └─1973 /usr/bin/twofing

This service should be able to start automatically at boot, giving your RasPad a right-click mouse functionality.

Troubleshooting

Problem: I get an error when compiling

Check that all prerequisite packages are installed
Check that the correct permissions are being using (especially if you see an error similar to 'dpkg: error: requested operation requires superuser privilege'

Problem: The touchscreen calibration is horrifically off! What happened?

Calibration. the file used for xorg is calibrated to my screen. naturally, through both wear and the manufacturing process, your screen's accuracy and dimensions will be off. If you find this to be too distracting, new calibration data can be obtained by using x-input-calibrator. The usage of that particular command is fairly simple:
Start the Raspad
From the interface, open a terminal window.
run x-input-calibrator. Your screen will begin a calibration process.
After the calibration process, the terminal window will show a chunk of config for Xorg. The Option axis values should be replaced in /usr/share/X11/xorg.conf.d/70-twofing.conf. Leave the rest alone if you can. If for some reason the defaults are blasted away, refer to this:

Section "InputClass"
        Identifier      "calibration"
        Driver "evdev"
        MatchProduct    "ILITEK ILITEK-TP Mouse"
        MatchDevicePath "/dev/input/event*"
        Option  "MinX"  "-188"
        Option  "MaxX"  "66235"
        Option  "MinY"  "-539"
        Option  "MaxY"  "65378"
        Option  "SwapXY"        "0" # unless it was already set to 1
        Option  "InvertX"       "0"  # unless it was already set
        Option  "InvertY"       "0"  # unless it was already set
EndSection