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Enable right-click for the Raspberry Pi touchscreen

(Yes, even under Raspbian 10 Buster)

tl;dr

  1. Install evdev-right-click-emulation

  2. Load the uinput kernel module

  3. Make sure that you have access to /dev/uinput and /dev/input

  4. Run evdev-right-click-emulation

Finally I got my hands on a new Raspberry Pi 4, and I wanted to use the official 7" touchscreen with it. There was only one problem: The right click didn't work.

There are multiple ways floating around the web to enable it (e.g. in the official forums), but none of them worked for me under Raspbian 10. Even the config files in /usr/share/X11/xorg.conf.d look like it should work out of the box.

After a long frustrating search I found a solution: A small program called evdev-right-click-emulation.

Installation of evdev-rce

Installation is pretty straight forward:

sudo apt install build-essential libevdev2 libevdev-dev
git clone 'https://github.com/PeterCxy/evdev-right-click-emulation.git'
cd 'evdev-right-click-emulation'
make all
sudo cp 'out/evdev-rce' '/usr/local/bin/'
sudo chmod +x '/usr/local/bin/evdev-rce'

You enable right-clicking by running it via sudo evdev-rce from a graphical terminal.

Now there is the next problem: How do you enable autostart for normal users without entering a password? Of course there are different ways like setting the setuid bit, or using the NOPASSWD directive in /etc/sudoers.

But why run it as root when you can run it as normal user?

Run evdev-rce as normal user

First of all your user (usually pi) needs access to the input devices in /dev/input:

sudo usermod -G 'input' -a pi

evdev-rce uses the kernel module uinput, which is used to create virtual input devices. It has to be automatically loaded at boot:

echo 'uinput' | sudo tee -a /etc/modules

The uinput device can be found under /dev/uinput. By default only root is allowed to access it. We are going to change that with a custom udev rule:

sudo <EDITOR> /etc/udev/rules.d/99-uinput.rules

KERNEL=="uinput", MODE="0660", GROUP="input"

sudo udevadm control --reload-rules
sudo udevadm trigger

After a re-login, you should be able to run evdev-rce as normal user.

Startup evdev-rce on login

Almost done. To start evdev-rce on login just create the following autostart file:

mkdir -p "$HOME/.config/autostart"
<EDITOR> "$HOME/.config/autostart/evdev-rce.desktop"

[Desktop Entry]
Version=1.0
Type=Application
Name=evdev-rce
GenericName=Enable long-press-to-right-click gesture
Exec=env LONG_CLICK_INTERVAL=500 LONG_CLICK_FUZZ=50 /usr/local/bin/evdev-rce
Terminal=true
StartupNotify=false