Workbench creation

Introduction
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 simply maintained privately), 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 in the Python console):
 * On Linux it is usually.
 * On Windows it is, which is usually.
 * On macOS it is usually.

The Mod directory should look like this:

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


 * In the Init.py 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 InitGui.py 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 Init.py and InitGui.py 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 doing a C++ workbench, you will actually most likely be doing 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:

The Init.py file
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 and  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  files. See Code snippets for more examples.

Python workbenches
This is the InitGui.py file:

Other than that, you can do anything you want: you could put your whole workbench code inside the InitGui.py 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 InitGui.py file. You can organize those files the way you want, a good example is one for each FreeCAD command you add.

Preferences
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 myResources.py myqrc.qrc
 * in InitGui.py, add import myResource(.py)
 * update your repository(git) with myResources.py 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

Distribution
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, 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 external Addons that your Workbench either depends on, is blocked by, or is intended to replace.

Optionally, you can include file called metadata.txt file describing your workbench's external dependencies (on either other Addons, Workbenches, or Python modules). The format of this 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. For example:

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 InitGui.py file becomes very simple: It might contain just one line:

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:

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

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.

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

"Compiling" your resource file
compileA2pResources.py from the A2Plus workbench:

Related

 * Translating an external workbench
 * Namespaced Workbenches - discussion
 * freecad.workbench_starterkit