Developing Orange3 Add-ons

Orange add-on is an ordinary python package, installed by running install and distributed via pypi. Widgets, tutorials and help are registered in file using entry points. When Orange Canvas starts, it reads this entry points, registers all the widgets and adds them to the menu. This containts one widget (Hello World), which is contained in a new category (My Category). The widget also displays help when you press F1.

Registering widgets

The My Category category is registered using “orange.widgets” entry point in, which contains category name (My Category) and package that contains the widgets (orangecontrib.example.widgets). The packages contains category metadata, including category ICON, BACKGROUD color and WIDGET_HELP_PATH. The latter can be either a local path or a url to a server which hosts the add-on documentation.

Orange Canvas will automatically discover all widget modules that are placed inside the category package and put found widgets into the category. Widget is a class extending Orange.widgets.widget.OWWidget and has an attribute name. Each widget should be placed in a separate directory.

Providing Help files

When F1 is press on open widget or on a selected widget icon, a help file is shown. Help files are ordinary documentation pages, written in rst and placed into doc/widgets folder.

Help pages can be written in markdown or in rst. The only requirement is that the title of the page is the same as the widget name. To allow automatic discovery of help pages, all widget help pages should be listed on a documentation page inside a section named Widget.

The location of the documentation is set using the “” entrypoint. It usually points to the constant WIDGET_HELP_PATH in the package containing widgets. The constant should list the possible locations of the master page (the one that links to all widgets). This example add-on includes three different locations:

  • Development documentation is available for developers that manually build documentation using sphinx
  • Locally installed documentation, which is available if the add-on was installed using a wheel package. Local installation has to be enabled in by calling function include_documentation.
  • Online documentation points to the hosted documentation such as read the docs or python hosted.

The locations are tried in order they are listed, the first one available will be used.

Beside widgets, add-on can also include tutorial schemas, that are shown in the Welcome dialog. Tutorials are ordinary ows files, but often include annotations that guide the user. Tutorial packages are registered in using “orange.widgets.tutorials” entry point.



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