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name: widget-development description: "Build, preview, test, and load Orange widgets and Canvas workflows." metadata: disco-role: operating disable-model-invocation: true license: NOASSERTION

Orange3 Widget Development

Use this sub-skill when the task is about Orange's widget framework rather than a specific data-mining method: authoring an OWWidget, wiring GUI controls and settings, previewing or unit-testing widgets, loading .ows Canvas workflows, debugging widget discovery, or generating a widget catalog from the installed Orange package.

Route by task

• New or revised widget class → read references/widget-framework.md, then references/gui-controls.md. Use OWWidget, new-style Inputs/Outputs, Setting/ContextSetting, Msg message classes, and a WidgetPreview fence.
• GUI control binding or settings → read references/gui-controls.md, then the context/settings section in references/widget-framework.md.
• Preview, tests, or headless Qt → read references/canvas-and-workflows.md and references/troubleshooting.md. Prefer WidgetPreview for interactive/manual checks and Orange.widgets.tests.base.WidgetTest for assertions.
• Canvas workflow loading or compatibility → read references/canvas-and-workflows.md. Use WidgetsScheme.load_from(..., registry=reg) or the non-interactive Canvas runner; pause signal propagation while loading test workflows.
• Widget discovery/catalog work → read references/canvas-and-workflows.md, then run the bundled scripts/create_widget_catalog.py against an installed Orange package.
• Failure triage → read references/troubleshooting.md first; it covers discovery, missing metadata/I/O, stored settings, context migrations, GUI binding, Qt platform/offscreen issues, preview exits, background cancellation, SQL credential errors, and workflow-loading failures.

Operating rules

1. Keep widget-development guidance framework-focused. Do not explain package-specific data, model, projection, visualization, or evaluation semantics except when they demonstrate the widget framework.
2. Treat SQL widget bases (OWBaseSql, SQL input decorators, credentials) as optional cross-cutting widget support. Do not require live PostgreSQL/MSSQL services for the minimum GUI/framework workflow.
3. Do not point future agents to source-checkout scripts or docs. Use the bundled references and bundled scripts/create_widget_catalog.py; the references below distill the needed framework behavior.
4. In headless Linux/CI, set QT_QPA_PLATFORM=offscreen before widget previews, widget tests, workflow loads, or catalog icon rendering.
5. For long-running widgets, use cooperative cancellation (ConcurrentWidgetMixin, TaskState.is_interruption_requested()) and call shutdown() from onDeleteWidget().

Evidence snapshot

Distilled and live-checked against Orange3 3.41.0.dev with Qt/PyQt available. Key verified API facts include:

• OWWidget(*args, captionTitle=None, **kwargs)
• Input(name, type, ..., multiple=False, default=False, explicit=False, auto_summary=None, closing_sentinel=None)
• Output(name, type, ..., default=False, explicit=False, dynamic=True, auto_summary=None)
• WidgetPreview(widget_cls).run(input_data=None, *, no_exec=False, no_exit=False, **kwargs)
• DomainContextHandler(*, match_values=0, first_match=True, **kwargs)
• WidgetTest.create_widget(cls, stored_settings=None, reset_default_settings=True, **kwargs)
• ConcurrentWidgetMixin.start(task, *args, **kwargs), cancel(), and shutdown()

Representative source evidence was distilled from Orange widget/canvas framework modules, development docs, GUI/settings/testing helpers, workflow tests, SQL widget helpers, and the repo-maintained widget-catalog script. The runtime guidance here is self-contained and does not require those source files to be present.