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KDStateMachineEditor - Library for visualizing and editing state charts


The KDAB State Machine Editor Library is a framework that can be used to help develop full-featured State Machine Editing graphical user interfaces and tools. Output from such applications is in metacode or QML that can then be used in larger Qt or QtQuick projects.

For a full description of the KDAB State Machine Editor Library, read our wiki on GitHub,


The main feature of KDStateMachineEditor is visualizing and editing state charts.

Note: A proof-of-concept application called kdstatemachineditor executable is part of this repository and will be built automatically. It can be run from the bin/ directory once the project built.

KDSME visualizing microwave_parallel.scxml

KDSME visualizing microwave_parallel.scxml

KDSME visualizing stickman.scxml

KDSME visualizing stickman.scxml

KDSME visualizing trafficreport.scxml (using a different theme)

KDSME visualizing trafficreport.scxml (using a different theme)

KDSME visualizing a live-running QScxmlStateMachine

KDSME visualizing a live-running QScxmlStateMachine

KDSME embedded in another application (here: GammaRay)

KDSME embedded in another application (here: GammaRay)


  • Internal API to create state charts

    • Consisting of states and transitions
    • Also supports history/initial states (in short: everything the SCXML spec provides)
  • QML scene which shows the state charts

    • Custom items for drawing transitions using bezier curves
    • Editing: Drag & drop support, move support, etc.
    • Editing: Undo stack implementation, redo/undo actions for all operations
  • Abstract interface to layout state charts

    • GraphViz's cgraph is one of the implemented layouting backends (part of this repository)
  • Import/Export capabilities

    • Allows to import/export .scxml files
    • Allows to export .svg files
    • Allows to export .qml files (in QtQml.StateMachine syntax)
  • Allows to inspect running state machine instances

    • Both supports visualizing QStateMachine or QScxmlStateMachine
    • Can inspect remote applications (i.e. processes living on another machine)
    • Using QtRemoteObjects for communication
      • Requires the target application to be "instrumented", cf. the [qsmdebugger](examples/qsmdebugger/] example
  • Theming support (cf. screenshots above) -- currently available are:

    • DarkTheme
    • SystemTheme


KDStateMachineEditor's main user is KDAB's GammaRay, a tool for introspecting Qt application. GammaRay has the capability to display the state chart of a QStateMachine embedded in the application, making it possible to inspect the live configuration changes of the state machine, as well as zooming into child state (machines).

Building and running

We strongly recommend installing Graphviz:

    (Ubuntu) sudo apt install graphviz graphviz-dev
    (Fedora) dnf install graphviz graphviz-devel
    (Mac) brew install graphviz
    (Windows) choco install graphviz

of course you need a Qt5 or Qt6 installation and CMake too.


Make sure you have cmake, ninja, compiler, Qt, etc in PATH.

    mkdir build
    cd build
    cmake -G Ninja -DCMAKE_INSTALL_PREFIX=/path/where/to/install ..
    cmake --build
    cmake --build . --target install

Start the test app


See INSTALL.txt for more information.

Known Issues

The editor part of the library still is somewhat "rough"; not a lot of development time has been spent on streamlining this feature.


KDAB will happily accept external contributions, but substantial contributions require a signed Copyright Assignment Agreement.

Contact for more information about the Copyright Assignment Agreement.

Please submit your contributions or issue reports from our GitHub space at


The KDAB State Machine Editor Library is (C) 2014-2023 Klarälvdalens Datakonsult AB (KDAB), and is licensed according to the terms of the LGPL 2.1.

Commercial licensing terms are available in the included file LicenseRef-KDAB-KDStateMachineEditor.txt.

For terms of redistribution, refer to the corresponding license agreement.

About KDAB

This State Machine Editor Library is supported and maintained by Klarälvdalens Datakonsult AB (KDAB).

The KDAB Group is the global No.1 software consultancy for Qt, C++ and OpenGL applications across desktop, embedded and mobile platforms.

The KDAB Group provides consulting and mentoring for developing Qt applications from scratch and in porting from all popular and legacy frameworks to Qt. We continue to help develop parts of Qt and are one of the major contributors to the Qt Project. We can give advanced or standard trainings anywhere around the globe on Qt as well as C++, OpenGL, 3D and more.

Please visit to meet the people who write code like this.

Stay up-to-date with KDAB product announcements: