Workbench creation

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(Redirected from Module Creation)


This page will show you how to add a new workbench to the FreeCAD interface. Workbenches are containers for FreeCAD commands. They can be coded in Python, in C++, or in a mix of both, which has the advantage to ally the speed of C++ to the flexibility of Python. In all cases, though, your workbench will be launched by a set of two Python files. They can be "internal" workbenches, included with FreeCAD's distribution, or "external" workbenches, distributed via the Addon Manager or installed manually by downloading from some online repository. Internal workbenches may be coded in either C++, Python, or a combination of the two, whereas external workbenches must be Python-only.

The workbench structure

You need a folder, with any name you like, placed in the user Mod directory, with an file, and, optionally an file. The Init file is executed when FreeCAD starts, and the file is executed immediately after, but only when FreeCAD starts in GUI mode. That's all it needs for FreeCAD to find your workbench at startup and add it to its interface.

The user Mod directory is a sub-directory of the user application data directory (you can find the latter by typing App.getUserAppDataDir() in the Python console):

  • On Linux it is usually /home/<username>/.local/share/FreeCAD/Mod/ (version 0.20 and above) or /home/<username>/.FreeCAD/Mod/ (version 0.19 and below).
  • On Windows it is %APPDATA%\FreeCAD\Mod\, which is usually C:\Users\<username>\Appdata\Roaming\FreeCAD\Mod\.
  • On macOS it is usually /Users/<username>/Library/Application Support/FreeCAD/Mod/.

The Mod directory should look like this:

 +-- MyWorkbench/

Inside those files you can do whatever you want. Usually they are used like this:

  • In the file you just add a couple of things used even when FreeCAD works in console mode, for example the file importers and exporters
  • In the file you usually define a workbench, which contains a name, an icon, and a series of FreeCAD commands (see below). That python file also defines functions that are executed when FreeCAD loads (you try to do as little as possible there, so you don't slow down the startup), another that gets executed when the workbench is activated (that's where you'll do most of the work), and a third one when the workbench is deactivated (so you can remove things if needed).

The structure and file content for a workbench described here is the classic way of creating a new workbench. One can use a slight variation in the structure of files when making a new Python workbench, that alternative way is best described as a "namespaced workbench", opening up the possibility to use pip to install the workbench. Both structures work, so it is more a question of preference when creating a new workbench. The style and structure for workbenches presented here are available in the global namespace of FreeCAD, whereas for the alternative style and structure the workbench resides in a dedicated namespace. For further readings on the topic see Related.

C++ workbench structure

If you are going to code your workbench in python, you don't need to take special care, and can simply place your other python files together with your and files. When working with C++, however, you should take greater care, and start with respecting one fundamental rule of FreeCAD: The separation of your workbench between an App part (that can run in console mode, without any GUI element), and a Gui part, which will only be loaded when FreeCAD runs with its full GUI environment. So when developing a C++ workbench, you will actually most likely create two modules, an App and a Gui. These two modules must of course be callable from python. Any FreeCAD module (App or Gui) consists, at the very least, of a module init file. This is a typical AppMyModuleGui.cpp file:

extern "C" {
    void MyModuleGuiExport initMyModuleGui()  
         if (!Gui::Application::Instance) {
            PyErr_SetString(PyExc_ImportError, "Cannot load Gui module in console application.");
        try {
            // import other modules this one depends on
            Base::Interpreter().runString("import PartGui");
            // run some python code in the console
            Base::Interpreter().runString("print('welcome to my module!')");
        catch(const Base::Exception& e) {
            PyErr_SetString(PyExc_ImportError, e.what());
        (void) Py_InitModule("MyModuleGui", MyModuleGui_Import_methods);   /* mod name, table ptr */
        Base::Console().Log("Loading GUI of MyModule... done\n");
        // initializes the FreeCAD commands (in another cpp file)
        // initializes workbench and object definitions
         // add resources and reloads the translators

The file

"""FreeCAD init script of XXX module"""

# ***************************************************************************
# *   Copyright (c) 2015 John Doe                              *   
# *                                                                         *
# *   This file is part of the FreeCAD CAx development system.              *
# *                                                                         *
# *   This program is free software; you can redistribute it and/or modify  *
# *   it under the terms of the GNU Lesser General Public License (LGPL)    *
# *   as published by the Free Software Foundation; either version 2 of     *
# *   the License, or (at your option) any later version.                   *
# *   for detail see the LICENCE text file.                                 *
# *                                                                         *
# *   FreeCAD is distributed in the hope that it will be useful,            *
# *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
# *   GNU Lesser General Public License for more details.                   *
# *                                                                         *
# *   You should have received a copy of the GNU Library General Public     *
# *   License along with FreeCAD; if not, write to the Free Software        *
# *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  *
# *   USA                                                                   *
# *                                                                         *
# ***************************************************************************/

FreeCAD.addImportType("My own format (*.own)", "importOwn")
FreeCAD.addExportType("My own format (*.own)", "exportOwn")
print("I am executing some stuff here when FreeCAD starts!")

You can choose any license you like for your workbench, but be aware that if you wish to see your workbench integrated into and distributed with the FreeCAD source code at some point, it needs to be LGPL2+ like the example above. See Licence.

The FreeCAD.addImportType() and addEXportType() functions allow you to give the name and extension of a file type, and a Python module responsible for its import. In the example above, an module will handle .own files. See Code snippets for more examples.

Python workbenches

This is the file:

class MyWorkbench (Workbench):

    MenuText = "My Workbench"
    ToolTip = "A description of my workbench"
    Icon = """paste here the contents of a 16x16 xpm icon"""

    def Initialize(self):
        """This function is executed when the workbench is first activated.
        It is executed once in a FreeCAD session followed by the Activated function.
        import MyModuleA, MyModuleB # import here all the needed files that create your FreeCAD commands
        self.list = ["MyCommand1", "MyCommand2"] # a list of command names created in the line above
        self.appendToolbar("My Commands", self.list) # creates a new toolbar with your commands
        self.appendMenu("My New Menu", self.list) # creates a new menu
        self.appendMenu(["An existing Menu", "My submenu"], self.list) # appends a submenu to an existing menu

    def Activated(self):
        """This function is executed whenever the workbench is activated"""

    def Deactivated(self):
        """This function is executed whenever the workbench is deactivated"""

    def ContextMenu(self, recipient):
        """This function is executed whenever the user right-clicks on screen"""
        # "recipient" will be either "view" or "tree"
        self.appendContextMenu("My commands", self.list) # add commands to the context menu

    def GetClassName(self): 
        # This function is mandatory if this is a full Python workbench
        # This is not a template, the returned string should be exactly "Gui::PythonWorkbench"
        return "Gui::PythonWorkbench"

Other than that, you can do anything you want: you could put your whole workbench code inside the if you want, but it is usually more convenient to place the different functions of your workbench in separate files. So those files are smaller and easier to read. Then you import those files into your file. You can organize those files the way you want, a good example is one for each FreeCAD command you add.


You can add a Preferences page for your Python workbench. The Preferences pages look for a preference icon with a specific name in the Qt Resource system. If your icon isn't in the resource system or doesn't have the correct name, your icon won't appear on the Preferences page.

Adding your workbench icon:

  • the preferences icon needs to be named "preferences-" + "modulename" + ".svg" (all lowercase)
  • make a qrc file containing all icon names
  • in the main *.py directory, run pyside-rcc -o myqrc.qrc
  • in, add import myResource(.py)
  • update your repository(git) with and myqrc.qrc

You'll need to redo the steps if you add/change icons.

@kbwbe has created a nice script to compile resources for the A2Plus workbench. See below.

Adding your preference page(s):

  • You need to compile the Qt designer plugin that allows you to add preference settings with Qt Designer
  • Create a blank widget in Qt Designer (no buttons or anything)
  • Design your preference page, any setting that must be saved (preferences) must be one of the Gui::Pref* widgets that were added by the plugin)
  • In any of those, make sure you fill the PrefName (the name of your preference value) and PrefPath (ex: Mod/MyWorkbenchName), which will save your value under BaseApp/Preferences/Mod/MyWorkbenchName
  • Save the ui file in your workbench, make sure it's handled by cmake
  • In your workbench, for ex. inside the InitGui file, inside the Initialize method (but any other place works too), add: FreeCADGui.addPreferencePage("/path/to/myUiFile.ui","MyGroup"), "MyGroup" being one of the preferences groups on the left. FreeCAD will automatically look for a "preferences-mygroup.svg" file in its known locations (which you can extend with FreeCADGui.addIconPath())
  • Make sure the addPreferencePage() method is called only once, otherwise your pref page will be added several times


To distribute your Python workbench, you may either simply host the files in some location and instruct your users to download them and place them in their Mod directory manually, or you may host them in an online git repository (GitHub, GitLab, Framagit, and Debian Salsa are currently supported locations) and configure them for the Addon Manager to install. Instructions for inclusion on FreeCAD's official Addons list can be found on the FreeCAD Addons GitHub repository. To use the Addon Manager, a package.xml metadata file should be included, which instructs the Addon Manager how to find your workbench's icon, and allows display of a description, version number, etc. It can also be used to specify other workbenches or Python packages that your Workbench either depends on, is blocked by, or is intended to replace.

For a quick guide on how to create a basic package.xml file and add a workbench to the Addon Manager see: Add Workbench to Addon Manager.

Optionally, you can include a separate metadata file describing your Python dependencies. This may be either a file called metadata.txt describing your workbench's external dependencies (on either other Addons, Workbenches, or Python modules), or a requirements.txt describing your Python dependencies. Note that if using a requirements.txt file, only the names of the specified packages are used for dependency resolution: pip command options, include options and version information are not supported by the Addon Manager. Users may manually run the requirements file using pip if those features are required.

The format of the metadata.txt file is plain text, with three optional lines:


Each line should consist of a comma-separated list of items your Workbench depends on. Workbenches may be either an internal FreeCAD Workbench, e.g. "FEM", or an external Addon, for example "Curves". The required and optional Python libraries should be specified with their canonical Python names, such as you would use with pip install. For example:


You may also include a script that is run when your package is uninstalled. This is a file called "" located at the top level of your Addon. It is executed when a user uninstalls your Addon using the Addon Manager. Use it to clean up anything your Addon may have done to the users system that should not persist when the Addon is gone (e.g. removing cache files, etc.).

To ensure that your addon is being read correctly by the Addon Manager, you can enable a "developer mode" in which the Addon Manager examines all available addons and ensures their metadata contains the required elements. To enable this mode select: Edit → Preferences... → Addon Manager → Addon manager options → Addon developer mode, see Preferences Editor.

C++ workbenches

If you are going to code your workbench in C++, you will probably want to code the workbench definition itself in C++ too (although it is not necessary: you could also code only the tools in C++, and leave the workbench definition in Python). In that case, the file becomes very simple: It might contain just one line:

import MyModuleGui

where MyModule is your complete C++ workbench, including the commands and workbench definition.

Coding C++ workbenches works in a pretty similar way. This is a typical Workbench.cpp file to include in the Gui part of your module:

namespace MyModuleGui {
    class MyModuleGuiExport Workbench : public Gui::StdWorkbench

        virtual ~Workbench();

        virtual void activated();
        virtual void deactivated();

        Gui::ToolBarItem* setupToolBars() const;
        Gui::MenuItem*    setupMenuBar() const;


You can add a Preferences page for C++ workbenches too. The steps are similar to those for Python.


There are two options to distribute a C++ workbench, you can either host precompiled versions for the different operating systems yourself, or you can request for your code to be merged into the FreeCAD source code. As mentioned above this requires a LGPL2+ license, and you must first present your workbench to the community in the FreeCAD forum for review.

FreeCAD commands

FreeCAD commands are the basic building block of the FreeCAD interface. They can appear as a button on toolbars, and as a menu entry in menus. But it is the same command. A command is a simple Python class, that must contain a couple of predefined attributes and functions, that define the name of the command, its icon, and what to do when the command is activated.

Python command definition

class My_Command_Class():
    """My new command"""

    def GetResources(self):
        return {"Pixmap"  : "My_Command_Icon", # the name of a svg file available in the resources
                "Accel"   : "Shift+S", # a default shortcut (optional)
                "MenuText": "My New Command",
                "ToolTip" : "What my new command does"}

    def Activated(self):
        """Do something here"""

    def IsActive(self):
        """Here you can define if the command must be active or not (greyed) if certain conditions
        are met or not. This function is optional."""
        return True

FreeCADGui.addCommand("My_Command", My_Command_Class())

C++ command definition

Similarly, you can code your commands in C++, typically in a Commands.cpp file in your Gui module. This is a typical Commands.cpp file:


  sAppModule    = "MyModule";
  sGroup        = QT_TR_NOOP("MyModule");
  sMenuText     = QT_TR_NOOP("Runs my command...");
  sToolTipText  = QT_TR_NOOP("Describes what my command does");
  sWhatsThis    = QT_TR_NOOP("Describes what my command does");
  sStatusTip    = QT_TR_NOOP("Describes what my command does");
  sPixmap       = "some_svg_icon_from_my_resource";

void CmdMyCommand::activated(int iMsg)
    openCommand("My Command");
    doCommand(Doc,"print('Hello, world!')");

bool CmdMyCommand::isActive(void)
  if( getActiveGuiDocument() )
    return true;
    return false;

void CreateMyModuleCommands(void)
    Gui::CommandManager &rcCmdMgr = Gui::Application::Instance->commandManager();
    rcCmdMgr.addCommand(new CmdMyCommand());

"Compiling" your resource file from the A2Plus workbench:

#!/usr/bin/env python
# -*- coding: utf-8 -*-
#*                                                                         *
#*   Copyright (c) 2019 kbwbe                                              *
#*                                                                         *
#*   Portions of code based on hamish's assembly 2                         *
#*                                                                         *
#*   This program is free software; you can redistribute it and/or modify  *
#*   it under the terms of the GNU Lesser General Public License (LGPL)    *
#*   as published by the Free Software Foundation; either version 2 of     *
#*   the License, or (at your option) any later version.                   *
#*   for detail see the LICENCE text file.                                 *
#*                                                                         *
#*   This program is distributed in the hope that it will be useful,       *
#*   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
#*   GNU Library General Public License for more details.                  *
#*                                                                         *
#*   You should have received a copy of the GNU Library General Public     *
#*   License along with this program; if not, write to the Free Software   *
#*   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  *
#*   USA                                                                   *
#*                                                                         *

# This script compiles the A2plus icons for py2 and py3
# For Linux only
# Start this file in A2plus main directory
# Make sure pyside-rcc is installed

import os, glob

qrc_filename = 'temp.qrc'
if os.path.exists(qrc_filename):

qrc = '''<RCC>
\t<qresource prefix="/">'''
for fn in glob.glob('./icons/*.svg'):
    qrc = qrc + '\n\t\t<file>%s</file>' % fn
qrc = qrc + '''\n\t</qresource>


f = open(qrc_filename,'w')

    'pyside-rcc -o {}'.format(qrc_filename))
    'pyside-rcc -py3 -o {}'.format(qrc_filename))