Added BuildContext parameter to TextEditingController.buildTextSpan

Contents

Summary

A BuildContext parameter was added to TextEditingController.buildTextSpan.

Classes that extend or implement TextEditingController and override buildTextSpan need to add the BuildContext parameter to the signature to make it a valid override.

Callers of TextEditingController.buildTextSpan need to pass a BuildContext to the call.

Context

TextEditingController.buildTextSpan is called by EditableText on its controller to create the TextSpan that it renders. buildTextSpan can be overridden in custom classes that extend TextEditingController. This allows classes extending TextEditingController override buildTextSpan to change the style of parts of the text, for example, for rich text editing.

Any state that is required by buildTextSpan (other than the TextStyle and withComposing arguments) needed to be passed into the class that extends TextEditingController.

Description of change

With the BuildContext available, users can access InheritedWidgets inside buildTextSpan to retrieve state required to style the text, or otherwise manipulate the created TextSpan.

Consider the example where we have a HighlightTextEditingController that wants to highlight text by setting its color to Theme.accentColor.

Before this change the controller implementation would look like this:

class HighlightTextEditingController extends TextEditingController {
  HighlightTextEditingController(this.highlightColor);

  final Color highlightColor;

  @override
  TextSpan buildTextSpan({TextStyle? style, required bool withComposing}) {
    return super.buildTextSpan(style: TextStyle(color: highlightColor), withComposing: withComposing);
  }

And users of the controller would need to pass the color when creating the controller.

With the BuildContext parameter available, the HighlightTextEditingController can directly access Theme.accentColor using Theme.of(BuildContext):

class HighlightTextEditingController extends TextEditingController {
  @override
  TextSpan buildTextSpan({required BuildContext context, TextStyle? style, required bool withComposing}) {
    final Color color = Theme.of(context).accentColor;
    return super.buildTextSpan(context: context, style: TextStyle(color: color), withComposing: withComposing);
  }
}

Migration guide

Overriding TextEditingController.buildTextSpan

Add a required BuildContext context parameter to the signature of the buildTextSpan override.

Code before migration:

class MyTextEditingController {
  @override
  TextSpan buildTextSpan({TextStyle? style, required bool withComposing}) {
    /* ... */
  }
}

Example error message before migration:

'MyTextEditingController.buildTextSpan' ('TextSpan Function({TextStyle? style, required bool withComposing})') isn't a valid override of 'TextEditingController.buildTextSpan' ('TextSpan Function({required BuildContext context, TextStyle? style, required bool withComposing})').

Code after migration:

class MyTextEditingController {
  @override
  TextSpan buildTextSpan({required BuildContext context, TextStyle? style, required bool withComposing}) {
    /* ... */
  }
}

Calling TextEditingController.buildTextSpan

Pass a named parameter ‘context’ of type BuildContext to the call.

Code before migration:

TextEditingController controller = /* ... */;
TextSpan span = controller.buildTextSpan(withComposing: false);

Error message before migration:

The named parameter 'context' is required, but there's no corresponding argument.
Try adding the required argument.

Code after migration:

BuildContext context = /* ... */;
TextEditingController controller = /* ... */;
TextSpan span = controller.buildTextSpan(context: context, withComposing: false);

Timeline

Landed in version: 1.26.0
In stable release: 2.0.0

References

API documentation:

Relevant issues:

Relevant PRs: