Tray application and Dolphin integration for Syncthing

Martchus 559fde7c23 Document KDE issues 6 days ago
.github 027f32065f Add CLI to components in issue template 2 months ago
cli bcb2b49b72 Don't use lower-case Qt macros 5 months ago
connector e44a523e3a Update translations 3 months ago
fileitemactionplugin 5b2147a874 Apply scaling in renderSvgImage() similar to QIcon::pixmap() does 3 weeks ago
libsyncthing 1131a2915b Update libsyncthing to v1.7.1 3 weeks ago
model c0e2e0bce1 Apply clang-format 3 weeks ago
plasmoid e62a69a2a9 Enable High-DPI scaling/pixmaps in plasmoid 1 week ago
scripts 0c104f60b8 Wait till all processes finished, ask for killing 2 years ago
testhelper c103174609 Make desktop files for Plasma integration from template 5 months ago
tray ba6ca98ff3 Add missing REQUIRED_ICONS of syncthingtray 3 weeks ago
widgets c0e2e0bce1 Apply clang-format 3 weeks ago
.gitignore 4cabaf0c4b Use Go modules for building libsyncthing 1 year ago
.gitmodules 6ab7662a64 Add experimental 'libsyncthing' 2 years ago
CMakeLists.txt d27a6c5424 Fix version 1 week ago
LICENSE b7609d7d3e Initial import 4 years ago 0369a43b49 Add licensing info for Windows distribution 9 months ago 559fde7c23 Document KDE issues 6 days ago

Syncthing Tray

  • Qt 5-based tray application
  • Dolphin/Plasma integration
  • command-line interface
  • Qt-ish C++ interface to control Syncthing

Checkout the official forum thread for discussions and announcement of new features.

Issues can be created on GitHub but please read the "Known bugs" and "Planned features" sections in this document before.

I provide binaries/repositories for some platforms. There are also binaries/repositories provided by other distributors. For a list with links, checkout the Download section of this document. The release section on GitHub only contains a fraction of the available options.

Supported platforms

  • Designed to work under any desktop environment supported by Qt 5 with tray icon support
  • No desktop environment specific libraries required (only for optional features/integrations)
  • Tested under
    • X Window System
      • Plasma 5 (beside Qt Widgets based version there is a native "Plasmoid")
      • Openbox/lxqt/LXDE
      • Openbox/qt5ct/Tint2
      • Awesome/qt5ct
      • Cinnamon (native look and feel using adwaita-qt)
      • Deepin Desktop Environment
      • Xfce
    • Wayland
      • Plasma 5
        • native "Plasmoid" works well
        • for Qt Widgets based version see note below
      • other desktop environments
        • for Qt Widgets based version see note below
        • besides, the Qt Widgets based version would only work if the platform integration plugin used for Qt 5 applications uses the D-Bus protocol (or whatever is supported by your system tray) to show the tray icon
    • Windows 10
    • macOS 10.14 Mojave
  • Can be shown as regular window if tray icon support is not available

The Qt Widgets based version basically works under Wayland but there are positioning issues (see known bugs section).

If you can confirm it works under other desktop environments, please add it to the list.


  • Provides quick access to most frequently used features but does not intend to replace the official web UI
    • Check state of directories and devices
    • Check current traffic statistics
    • Display further details about directories and devices, like last file, last scan, items out of sync, ...
    • Display ongoing downloads
    • Display Syncthing log
    • Trigger re-scan of a specific directory or all directories at once
    • Open a directory with the default file browser
    • Pause/resume a specific device or all devices at once
    • Pause/resume a specific directory
    • View recent history of changes (done locally and remotely)
  • Shows notifications
    • The notification to show is configurable
    • Uses Qt's notification support or a D-Bus notification daemon directly
  • Reads connection parameters from Syncthing config file for quick setup (when just connecting to local instance)
  • Allows monitoring the status of the Syncthing systemd unit and to start and stop it (see section Configuring systemd integration)
  • Provides an option to conveniently add the tray to the applications launched when the desktop environment starts
  • Can launch Syncthing automatically when started and display stdout/stderr (useful under Windows)
  • Provides quick access to the official web UI
    • Utilizes either Qt WebEngine or Qt WebKit
    • Can be built without web view support as well (then the web UI is opened in the regular browser)
  • Allows switching quickly between multiple Syncthing instances
  • Also features a simple command line utility syncthingctl
    • Check status
    • Trigger rescan/pause/resume/restart
    • Wait for idle
    • View and modify raw configuration
    • Supports Bash completion, even for directory and device names
  • Also bundles a KIO plugin which shows the status of a Syncthing directory and allows to trigger Syncthing actions in Dolphin file manager
    • Rescan selected items
    • Rescan entire Syncthing directory
    • Pause/resume Syncthing directory
    • See also screenshots section
  • Also has an implementation as Plasmoid for Plasma 5 desktop
  • Allows building Syncthing as a library to run it in the same process as the tray/GUI (optional build configuration which is not enabled by default)
  • English and German localization

Does this launch or bundle Syncthing itself? What about my existing Syncthing installation?

Syncthing Tray does not launch Syncthing itself by default. There should be no interference with your existing Syncthing installation. You might consider different configurations:

  • If you're happy how Syncthing is started on your system so far just tell Syncthing Tray to connect to your currently running Syncthing instance in the settings. If you're currently starting Syncthing via systemd you might consider enabling the systemd integration in the settings (see section Configuring systemd integration).
  • If you would like Syncthing Tray to take care of starting Syncthing for you, you can use the Syncthing launcher available in the settings.
    • The Windows builds provided in the release section on GitHub come with a built-in version of Syncthing which you can consider to use. Keep in mind that automatic updates of Syncthing are not possible this way.
    • In any case you can simply point the launcher to the binary of Syncthing (which you have to download/install separately).
  • It is also possible to let Syncthing Tray connect to a Syncthing instance running on a different machine.


The screenshots are not up-to-date.

Qt Widgets based GUI under Openbox/Tint2 with dark Breeze theme

Qt Widgets based GUI under Openbox/Tint2

Under Plasma 5

Light theme

Plasmoid (light theme)

Dark theme

Plasmoid (dark theme)

Customized icons

Plasmoid (customized icons)

Settings dialog

Settings dialog

Web view

Web view Web view (dark)

Syncthing actions for Dolphin


Configuring systemd integration

The next section explains what it is good for and how to use it. If it doesn't work on your system please read the subsequent sections as well before filing an issue.

Using the systemd integration

With the system configured correctly and systemd support enabled at build-time the following features are available:

  • Starting and stopping the systemd unit of Syncthing
  • Consider the unit status when connecting to the local instance to prevent connection attempts when Syncthing isn't running anyways
  • Detect when the system has just been resumed from standby to avoid the "Disconnect" notification in that case

However, these features are optional. To use them they must be enabled in the settings dialog first.

Be aware that Syncthing Tray assumes by default that the systemd unit is a user unit. If you are using a regular system-wide unit (including those started with …@username) you need to enable the "System unit" checkbox in the settings. Note that starting and stopping the system-wide Syncthing unit requires authorization (systemd can ask through PolicyKit).

Required system configuration

The communication between Syncthing Tray and systemd is implemented using systemd's D-Bus service. That means systemd's D-Bus service (which is called org.freedesktop.systemd1) must be running on your D-Bus. For user units the session D-Bus is relevant and for regular units (including those started with …@username) the system D-Bus is relevant.

It seems that systemd's D-Bus service is only available when D-Bus itself is started via systemd. That is by default the case under Arch Linux and openSUSE and likely most other modern distributions where it is usually started via "socket activation" (e.g. /usr/lib/systemd/user/dbus.socket for the session D-Bus).

All of this counts for the session D-Bus and for the system D-Bus although the startup of the session D-Bus can be screwed up particularily easy. One easy way to screw it up is to start a second instance of the session D-Bus manually e.g. via dbus-run-session. When starting the session D-Bus this way the systemd integration will not work and you will likely end up with two session D-Bus processes. It is also worth noticing that you do not need to set the DBUS_SESSION_BUS_ADDRESS variable manually because the systemd file dbus.socket should take care of this.

Note that the Plasma Wayland session screwed things up in the way I've described. This has been fixed with Only spawn dbus-run-session if there isn't a session already but this change might not be available on older distributions.

Build-time configuration

The systemd integration can be explicitely enabled/disabled add compile time by adding -DSYSTEMD_SUPPORT=ON/OFF to the CMake arguments. If the systemd integration does not work be sure your version of Syncthing Tray has been compiled with systemd support.

Note for distributors: There will be no hard dependency to systemd in any case. Distributions supporting alternative init systems do not need to provide differently configured versions of Syncthing Tray. Disabling the systemd integration is mainly intended for systems which do not use systemd at all (e.g. Windows and MacOS).


Use the same approach as for launching an arbitrary application via a hotkey. Make it invoke

  • syncthingtray --trigger to show the tray menu.
  • syncthingtray --webui to show the web UI.
  • syncthingctl [...] to trigger a particular action. See syncthingctl -h for details.



See the release section on GitHub.

Packages and binaries

Build instructions

The application depends on c++utilities and qtutilities and is built the same way as these libaries. For basic instructions checkout the README file of c++utilities. For building this straight, see the section below. There's also documentation about various build variables which can be passed to CMake to influence the build.

Further dependencies

The following Qt 5 modules are requried (version 5.6 or newer): core network dbus gui widgets svg webenginewidgets/webkitwidgets

It is recommended to use at least Qt 5.14 to avoid limitations in previous versions (see Known bugs section).

The built-in web view and therefore the modules webenginewidgets/webkitwidgets are optional (see section Select Qt module for WebView).

To build the plugin for Dolphin integration KIO is also requried. Additionally, the Dolphin plugin requires Qt 5.8 or newer. To skip building the plugin, add -DNO_FILE_ITEM_ACTION_PLUGIN:BOOL=ON to the CMake arguments.

To build the Plasmoid for the Plasma 5 desktop, the Qt 5 module QML and the KF5 module Plasma are required as well. Additionally, the Plasmoid requires Qt 5.8 or newer. To skip building the Plasmoid, add -DNO_PLASMOID:BOOL=ON to the CMake arguments.

It is also possible to build only the CLI (syncthingctl) by adding -DNO_MODEL:BOOL=ON and -DNO_FILE_ITEM_ACTION_PLUGIN:BOOL=ON to the CMake arguments. Then only the Qt modules core, network and dbus are required.

To get rid of systemd support, add -DENABLE_SYSTEMD_SUPPORT_BY_DEFAULT to the CMake arguments. In this case the Qt module D-Bus is not required anymore. Note that there is no hard dependency to systemd in any case.

Building the testsuite requires CppUnit and Qt 5.8 or higher.

Building this straight

  1. Install (preferably the latest version of) the CGG toolchain or Clang, the required Qt 5 modules and CMake.
  2. Get the sources. For the lastest version from Git clone the following repositories: cd $SOURCES git clone c++utilities git clone git clone git clone
  3. Build and install everything in one step: cd $BUILD_DIR cmake \ -DCMAKE_BUILD_TYPE=Release \ -DCMAKE_INSTALL_PREFIX="/install/prefix" \ $SOURCES/subdirs/syncthingtray make install -j$(nproc)

Select Qt module for web view and JavaScript

  • Add -DWEBVIEW_PROVIDER:STRING=webkit/webengine/none to the CMake arguments to use either Qt WebKit (works with 'revived' version as well), Qt WebEngine or no web view at all. If no web view is used, the Syncthing web UI is opened in the default web browser. Otherwise the user can choose between the built-in web view and the web browser.
  • Add -DJS_PROVIDER:STRING=script/qml/none to the CMake arguments to use either Qt Script, Qt QML or no JavaScript engine at all. If no JavaScript engine is used, the CLI does not support scripting configuration changes.

Limitations of Qt WebEngine compared to Qt WebKit

  • When using a version of Qt older than 5.14 there is no way to allow only a particular self-signed certificate in Qt WebEngine. That means any self-signed certificate is accepted! See:
  • Qt WebEngine can not be built with GCC/mingw-w64 for Windows.
  • QWebEngineView seems to eat keyPressEvent.
  • Security issues are not a concern because no other website than the Syncthing web UI is shown. Any external links will be opened in the regular web browser anyways.

Troubleshooting KDE integration

If the Dolphin integration or the Plasmoid don't work, check whether the files for those components have been installed in the right directories.

For instance, under Tumbleweed it looks like this for the Plasmoid:


The files for the Dolphin integration look like this under Tumbleweed:


The directory the *.so file needs to be installed to seems to differ from distribution to distribution. The right directory for your distribution can be queried from qmake using qmake-qt5 -query QT_INSTALL_PLUGINS. In doubt, just look where other Qt 5 plugins are stored.

Actually the build system should be able to do that query automatically. It is also possible to specify the directory manually, e.g. for Tumbleweed one would add -DQT_PLUGIN_DIR=/usr/lib64/qt5/plugins to the CMake arguments.

Also be sure that the version of the plasma framework the plasmoid was built against is not newer than the version actually installed on the system. That can for instance easily happen when using tumbleweed-cli for sticking to a previous snapshot but having the lastest version of the plasmoid from my home repository installed.

If the Plasmoid still won't load, checkout the log of plasmashell/plasmoidviewer/plasmawindowed. Also consider using strace to find out at which paths the shell is looking for *.desktop and *.so files.

For a development setup of the KDE integration, continue reading the subsequent section.


Adding translations

Currently translations for English and German are available. Further translations can be added quite easily:

  1. Append a new translation file for the desired locale to the TS_FILES list in connector/CMakeLists.txt, model/CMakeLists.txt, widgets/CMakeLists.txt, fileitemactionplugin/CMakeLists.txt, plasmoid/CMakeLists.txt and tray/CMakeLists.txt.
  2. Trigger a new build, eg. follow steps under Building this straight.
  3. New translation files should have been created by the build system under connector/translations, model/translations, widgets/translations, fileitemactionplugin/translations, plasmoid/translations and tray/translations.
  4. Open the files with Qt Linguist to add translations. Qt Linguist is part of the Qt Tools repository and its usage is well documented.


  • Syncthing Tray displays also text from qtutilities. Hence it makes sense adding translations there as well (following the same procedure).
  • The CLI syncthingctl currently does not support translations.

Using backend libraries

The contained backend libraries (which provide connecting to Syncthing, data models and more) are written for internal use whithin the components contained by this repository.

Hence those libraries do not provide a stable ABI/API. If you like to use them to develop Syncthing integration or tooling with Qt and C++, it makes most sense to contribute it as an additional component directly to this repository. Then I will be able to take it into account when changeing the API.

KDE integration

Since the Dolphin integration and the Plasmoid are plugins, testing and debugging requires a few extra steps. See Testing and debugging Dolphin/KIO plugin with Qt Creator and Testing and debugging Plasma 5 plasmoid with Qt Creator.

Planned features

The tray is still under development; the following features are under construction or planned:

Known bugs

The following bugs are caused by dependencies and hence tracked externally. For bugs of Syncthing Tray itself, checkout the issues on GitHub.

  • Wayland limitations
    • The tray menu can not be positioned correctly under Wayland because the protocol does not allow setting window positions from the client-side (at least I don't know a way to do it). This issue can not be fixed unless Wayland provides an API to set the window position to specific coordinates or a system tray icon. See discussion on Note that the Plasmoid is not affected by this limitation.
    • While the tray menu is shown its entry is shown in the taskbar. Not sure whether there is a way to avoid this.
  • Qt bugs
  • KDE limitations
  • Systemd integration
    • This feature relies especially on the system being correctly configured. Checkout the Required system configuration section for details.

Attribution for 3rd party content

  • Some icons are taken from the Syncthing project.
  • Some icons are taken from Font Awesome (see their license).
  • Fallback icons are taken from KDE/Breeze project.