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Awesome Open Source


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Linux/X11 application for the Logitech Spotlight device (and similar devices).
See Download section for binary packages.


I saw the Logitech Spotlight device in action at a conference and liked it immediately. Unfortunately as in a lot of cases, software is only provided for Windows and Mac. The device itself works just fine on Linux, but the cool spotlight feature is done by additional software.

So here it is: a Linux application for the Logitech Spotlight.

Table of Contents


  • Configurable desktop spotlight
    • shade color, opacity, cursor, border, center dot and different shapes.
    • Zoom (magnifier) functionality.
  • Multiple screen support
  • Support of devices besides the Logitech Spotlight (see Device Support)


Planned features

  • Support for device button configuration/mapping
  • Vibration (Timer) Support (Logitech Spotlight)

Supported Environments

The application was mostly tested on Ubuntu 18.04 (GNOME) and OpenSuse 15 (GNOME) but should work on almost any Linux/X11 Desktop. In case you are building the application youself, make sure you have the correct udev rules installed (see pre-requisites section).

How it works

With a connection via the USB Dongle Receiver or via Bluetooth, the Logitech Spotlight device will be detected by Linux as a HID device with mouse and keyboard events. As mouse events the device sends relative cursor movements and left button presses. Acting as a keyboard, the device basically just sends left and right arrow key press events when forward or back on the device is pressed.

The mouse events of the detected device is what we are interested in. Since the device is already detected as a mouse input device and able to move the cursor, we simply detect if the Spotlight device is sending mouse move events. If it is sending mouse events, we will 'turn on' the desktop spot.

For more details: Have a look at the source code ;)

Notes about v0.7

This version implemented a virtual device by default (You can still disable it with the --disable-uinput command line option). Projecteur will now grab all device events and forward it to the virtual 'uniput' device. While this does currently not change any behavior or feature from v0.6, this prepares Projecteur for the planned button mapping feature.


The latest binary packages for some Linux distributions are available for download on bintray. Currently binary packages for Ubuntu, Debian, Fedora, OpenSuse, CentOS and Arch Linux are automatically built.

  • Latest develop: Download

  • Latest release: Download



  • C++14 compiler
  • CMake 3.6 or later
  • Qt 5.7 and later

Build Example

Note: You can omit setting the QTDIR variable, CMake will then usually find the Qt version that comes with the distribution's package management.

  > git clone
  > cd projecteur
  > mkdir build && cd build
  > QTDIR=/opt/Qt/5.9.6/gcc_64 cmake ..
  > make



When building Projecteur yourself

The input devices detected from the Spotlight device must be readable to the user running the application. To make this easier there is a udev rule template file in this repository:

  • During the CMake run, the file 55-projecteur.rules will be created from this template in your build directory. Copy that generated file to /lib/udev/rules.d/55-projecteur.rules
  • Most recent systems (using systemd) will automatically pick up the rule. If not, run sudo udevadm control --reload-rules and sudo udevadm trigger to load the rules without a reboot.
  • After that the input devices from the Logitech USB Receiver (but also the Bluetooth device) in /dev/input should be readable/writeable by you. (See also about device detection)
  • When building against the Qt version that comes with your distribution's packages you might need to install some additional QML module packages. For example this is the case for Ubuntu, where you need to install the packages qml-module-qtgraphicaleffects, qml-module-qtquick-window2 and qml-modules-qtquick2 to satisfy the application's runtime dependencies.

Application Menu

The application menu is accessable via the system tray icon. There you will find the preferences and the menu entry to exit the application. If the system tray icon is missing, see the Troubleshooting section.

Command Line Interface

Additional to the standard --help and --version options, there is an option to send commands to a running instance of Projecteur and the ability to set properties.

Usage: projecteur [option]

  -h, --help             Show command line usage.
  --help-all             Show complete command line usage with all properties.
  -v, --version          Print application version.
  --cfg FILE             Set custom config file.
  -d, --device-scan      Print device-scan results.
  -l, --log-level LEVEL  Set log level (dbg,inf,wrn,err), default is 'inf'.
  -D DEVICE              Additional accepted device; DEVICE=vendorId:productId
  -c COMMAND|PROPERTY    Send command/property to a running instance.

  spot=[on|off]          Turn spotlight on/off.
  settings=[show|hide]   Show/hide preferences dialog.
  quit                   Quit the running instance.

All the properties that can be set via the command line, are listed with the --help-all option.

Device Support

Compile Time

Besides the Logitech Spotlight, similar devices can be used and are supported. Additional devices can be added to devices.conf. At CMake configuration time the project will be configured to support these devices and also create entries for them in the generated udev-rule file.


Projecteur will also accept devices as supported when added via the -D command line option.

Example: projecteur -D 04b3:310c

This will enable devices for Projecteur, but it is up to the user to make sure the device is accessible (via udev rules).


Opaque Spotlight / No Transparency

To be able to show transparent windows a compositing manager is necessary. If there is no compositing manager running you will see the spotlight overlay as an opaque window.

  • On KDE it might be necessary to turn on Desktop effects to allow transparent windows.
  • Depending on your Linux Desktop and configuration there might not be a compositing manager running by default. You can run xcompmgr, compton or others manually.
    • Examples: xcompmgr -c -t-6 -l-6 -o.1 or xcompmgr -c

Missing System Tray

Projecteur was developed and tested on GNOME and KDE Desktop environments, but should work on most other desktop environments. If the system tray with the Application Menu is not showing, commands can be send to the application to bring up the preferences dialog, to test the spotlight, quit the application or set spotlight properties. See Command Line Interface.

On some distributions that have a GNOME Desktop by default there is no system tray extensions installed (Fedora for example). You can install the KStatusNotifierItem/AppIndicator Support or the TopIcons Plus GNOME extension to have a system tray that can show the Projecteur tray icon (and also from other applications like Dropbox or Skype).

Zoom is not updated while spotlight is shown

That is due to the fact how the zoom currently works. A screenshot is taken shortly before the overlay window is shown, and then a magnified section is shown wherever the mouse/spotlight is. If the zoom would be updated while the overlay window is shown, the overlay window it self would show up in the magnified section. That is a general problem, that also other magnifier tools face, although they can get around the problem by showing the magnified content rectangle always in the same position on the screen.


While not developed with Wayland in mind, users reported Projecteur works with Wayland. If you experience problems, you can try to set the QT_QPA_PLATFORM environment variable to wayland, example:

[email protected]:~/Projecteur/build$ QT_QPA_PLATFORM=wayland ./projecteur
Using Wayland-EGL

Wayland Zoom

On Wayland the Zoom feature is currently only implemented on KDE and GNOME. This is done with the help of their respective DBus interfaces for screen capturing. On other environemnts with Wayland, the zoom feature is currently not supported.

Device shows as not connected

If the device shows as not connected, there are some things you can do:

  • Check for devices with Projecteur's command line option -d or --device-scan option. This will show you a list of all supported and detected devices and also if they are readable/writable. If a detected device is not readable/writable it is an indicator, that there is something wrong with the installed udev rules.
  • Manually on the shell: Check if the device is detected by the Linux system: Run cat /proc/bus/input/devices | grep -A 5 "Vendor=046d"
    This should show one or multiple spotlight devices (among other Logitech devices)
    • Check you the corresponding /dev/input/event?? device file is readable by you.
      Example: test -r /dev/input/event19 && echo "SUCCESS" || echo "NOT readable"
  • Make sure you don't have conflicting udev rules installed, e.g. first you installed the udev rule yourself and later you used the automatically built Linux packages to install Projecteur.


Copyright 2018-2020 Jahn Fuchs

This project is distributed under the MIT License, see for more information.

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