# Added BuildContext parameter to TextEditingController.buildTextSpan

> A BuildContext parameter is added to TextEditingController.buildTextSpan so inheritors that override buildTextSpan can access inherited widgets.




:::important
These breaking change docs are accurate, as of the release
under which they are published. Over time, the
workarounds described here might become inaccurate.
We don't, in general, keep these breaking change docs up
to date as of each release.

The [breaking change index file](/release/breaking-changes)
lists the docs created for each release.
:::


## 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:

```dart
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)`:

```dart
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:

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

Example error message before migration:

```plaintext
'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:

```dart
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:

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

Error message before migration:

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

Code after migration:

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

## Timeline

Landed in version: 1.26.0<br>
In stable release: 2.0.0

## References

API documentation:

* [`TextEditingController.buildTextSpan`][]

Relevant issues:

* [Issue #72343][]

Relevant PRs:

* [Reland "Add BuildContext parameter to TextEditingController.buildTextSpan" #73510][]
* [Revert "Add BuildContext parameter to TextEditingController.buildTextSpan" #73503][]
* [Add BuildContext parameter to TextEditingController.buildTextSpan #72344][]

[Add BuildContext parameter to TextEditingController.buildTextSpan #72344]: https://github.com/flutter/flutter/pull/72344
[Issue #72343]: https://github.com/flutter/flutter/issues/72343
[Reland "Add BuildContext parameter to TextEditingController.buildTextSpan" #73510]: https://github.com/flutter/flutter/pull/73510
[Revert "Add BuildContext parameter to TextEditingController.buildTextSpan" #73503]: https://github.com/flutter/flutter/pull/73503
[`TextEditingController.buildTextSpan`]: https://api.flutter.dev/flutter/widgets/TextEditingController/buildTextSpan.html