Custom TextEditingController to style multi color icon font

flutter_custom_texteditingcontroller.dart

class AppTextEditingController extends TextEditingController {
  @override
  TextSpan buildTextSpan({TextStyle style, bool withComposing}) {
    final TextSpan textSpan =
        super.buildTextSpan(style: style, withComposing: withComposing);

    if (text != null) {
      return _buildEmojiTextSpan(text);
    }
    return textSpan;
  }

  // Get emoji color from code
  Color _getEmojiColor(int emojiCode) {
    switch (emojiCode) {
      case 0xe900:
        return const Color(0xFFFFD243);
      case 0xe901:
        return const Color(0xFFFF39AF);
      case 0xe902:
        return const Color(0xFF2CD7FF);
    }
    return null;
  }

  // Build text span
  TextSpan _buildEmojiTextSpan(String text) {
    if (text == null) {
      return const TextSpan();
    }
    final List<TextSpan> children = <TextSpan>[];
    // integer Unicode code points
    final Runes runes = text.runes;

    final List<int> chunk = <int>[];
    for (int i = 0; i < runes.length; i++) {
      final int code = runes.elementAt(i);
      // print('code ${code.toRadixString(16)}');

      // we assume that everything that is not
      // in Extended-ASCII set is an emoji...
      final bool isEmoji = code > 255;
      if (!isEmoji) {
        chunk.add(code);
      }
      if (isEmoji || i == runes.length - 1) {
        children.add(
          TextSpan(
            text: String.fromCharCodes(chunk),
            style: const TextStyle(),
          ),
        );
        chunk.clear();
        if (isEmoji) {
          children.add(
            TextSpan(
              text: String.fromCharCode(code),
              style: TextStyle(
                fontFamily: 'nft',
                color: _getEmojiColor(code),
              ),
            ),
          );
        }
      }
    }
    return TextSpan(children: children);
  }
}