text

The package 'text' allows to get detailed information about the text such as the number of lines, lines at positions, characters at locations, locations at positions, positions at locations, and vice versa.

It is much faster than you could possibly imagine, thanks to the sparse lists.

import "package:text/text.dart";

void main() {
  var text = new Text(string);
  var position = text.length ~/ 2;
  // Get the line by the character position
  var line = text.lineAt(position);
  print("#${line.number}: ${toStr(line.characters)}");

  // Get the location by the character position
  var location = text.locationAt(position);
  print("pos: $position => loc: ${location.line}:${location.column}");

  // Get the character position by the location
  position = text.position(location);
  print("loc: ${location.line}:${location.column} => pos: $position");

  // Get the line by index (line.number - 1)
  var line2 = text.line(line.number - 1);
  print("#${line.number} = #${line2.number}");

  // Search the Unicode character and display it location and string
  var char = 65504; // ￠
  position = text.characters.indexOf(char);
  location = text.locationAt(position);
  line = text.lineAt(position);
  print("${toStr([char])} found at pos: $position");
  print("${toStr([char])} found at loc: ${location.line}:${location.column}");
  print("${toStr([char])} found in line: ${toStr(line.characters)}");
}

String toStr(List<int> characters) => new String.fromCharCodes(characters);

String string = '''
1. Line 1
2. Line 2
3. Line 3
4. Line 4
5. Line 5 ￠
''';

Output:

#3: 3. Line 3

pos: 26 => loc: 3:7
loc: 3:7 => pos: 26
#3 = #3
￠ found at pos: 50
￠ found at loc: 5:11
￠ found in line: 5. Line 5 ￠