attributed_text 0.2.0

Text with metadata spans for easy text editing and styling.

Easily add metadata to your Strings with the attributed_text package.

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AttributedText forms the basis of all text representation within super_editor.

Get Started

AttributedText combines a String with some number of Attribution spans.

final helloWorld = AttributedText(
  text: "Hello, world!",
  spans: AttributedSpans(
    attributions: [
      const SpanMarker(attribution: bold, offset: 7, markerType: SpanMarkerType.start),
      const SpanMarker(attribution: bold, offset: 12, markerType: SpanMarkerType.end),
    ],
  ),
);

This example associates an Attribution called bold with all the characters from index 7 to index 12. Logically, you can think of this AttributedText as looking like "Hello, world!".

What is an Attribution?

An Attribution is the metadata that's associated with the characters in an AttributedSpans.

A text editor, for example, would probably define Attributions for bold, italics, underline, strikethrough, links, and inline code.

Named Attributions

Attributions that require only a name are easily defined as NamedAttributions.

final bold = NamedAttribution("bold");
final italics = NamedAttribution("italics");
final underline = NamedAttribution("underline");

Two NamedAttributions are considered "equivalent" when they both have the same name.

Custom Attributions

Any object that implements the Attribution interface can be used as an Attribution in an AttributedText.

You may need to define your own custom Attribution classes to represent metadata that includes more information than just a name.

For example, you might implement a LinkAttribution like this:

/// Attribution to be used within [AttributedText] to
/// represent a link.
///
/// Every [LinkAttribution] is considered equivalent, so
/// that [AttributedText] prevents multiple [LinkAttribution]s
/// from overlapping.
class LinkAttribution implements Attribution {
  LinkAttribution({
    required this.url,
  });

  @override
  String get id => 'link';

  final Uri url;

  @override
  bool canMergeWith(Attribution other) {
    return this == other;
  }

  @override
  bool operator ==(Object other) =>
      identical(this, other) || other is LinkAttribution && runtimeType == other.runtimeType && url == other.url;

  @override
  int get hashCode => url.hashCode;
}

Any two instances of an Attribution that have the same id will be prevented from overlapping. If two Attributions with the same id touch each other, then AttributedText will check if one of them canMergeWith the other - if so, they are combined.