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Contribution Guide

This guide consists of:

Project Structure

The frontend consists of 3 projects:

  • frontend is the playground app itself.
  • frontend/playground_components is the package with common code for Playground and Tour of Beam.
  • frontend/playground_components_dev is common code for tests of Playground and Tour of Beam.

State Management

Playground uses the app_state package for state management. The standalone playground and the embedded playground are two screens within the same app, chosen by the URL at runtime.

The main state object is PlaygroundController, created in both of those screens. It is hung in the widget tree with the provider package for historical reasons, and we aim to remove that if we do further refactoring. New code should pass it directly from widget to widget for compile-time safety.

Example Loading

A URL is parsed into one of the subclasses of PagePath, most of which contain an ExamplesLoadingDescriptor object, which in turn may contain multiple ExampleLoadingDescriptor objects.

This is passed to the ExamplesLoader object. It constructs an ExampleLoader object for each example's descriptor, and that loader performs the actual loading.

To add a new source for examples:

  1. Subclass ExampleLoadingDescriptor with state and a method to parse it from a map of query string parameters.
  2. Add it to ExamplesLoadingDescriptorFactory.
  3. Subclass ExampleLoader and load an example there.
  4. Add it to the ExampleLoaderFactory in ExamplesLoader.

Theming

Playground app supports light and dark themes. Component themes are declared in theme.dart file.

To use specific color inside component you can use helper ThemeColors utility:

ThemeColors.of(context).greyColor

colors.dart contains color declarations.

Adding a New Page

To add a new page, do the following steps:

  1. Read the overview of the app_state package.
  2. Create a new PagePath subclass that parses the new URL.
  3. Create a new ChangeNotifier with PageStateMixin that holds the state of the page.
  4. Create a new StatelessWidget as the main one for the page.
  5. Create a new StatefulMaterialPage subclass that binds the three together.

See the example in lib/pages/standalone_playground.

Accessibility

Please, read the following guides about the accessibility: