xclud/dart_bidi

Implementation of the Unicode Bidirectional Algorithm (UBA) as described in https://unicode.org/reports/tr9/.

Implementation of the Unicode Bidirectional Algorithm (UBA).

Reference: https://unicode.org/reports/tr9/.

Converts logical strings to their equivalent visual representation. Persian, Hebrew and Arabic languages (and any other RTL language) are supported.

Web Demo

Web Demo

Getting Started

In your pubspec.yaml file add:

dependencies:
  bidi: any

Then, in your code import and use the package:

import 'package:bidi/bidi.dart' as bidi;

final visual = bidi.logicalToVisual('نوشته پارسی اینجا گذارده شود.');
print(visual);

Other Implementations

This package is also written in Rust (apart from this package, which is written in Dart). If you are looking for a pure Rust implementation of this package, look at https://crates.io/crates/bidi/.

dart_bidi's Issues

re-expose paragraph.paragraphSeparator

Hello @xclud in your latest refractor you made paragraph.paragraphSeparator private, and I'm using it in some package, can you please make it public again?

Using Arabic letters basic from in favor of isolated form

Hey, @xclud
context: There are two letter forms in Arabic that render exactly the same, the basic form and the isolated form.

Notices how the following Arabic letter LAM has the same glyph for both basic and isolated form.

currently, the algorithm maps to the isolated form which might be the right thing to do but unfortunately Arabic Google fonts seem to have a problem with this, this issue can be fixed by always mapping to the basic form when an isolated form is required.

even dart seems to work with the basic form in such cases

 final letter = 'ل';
 print(letter.codeUnits); // prints [1604]
 print(bidi.logicalToVisual(letter)); // prints [65245]

I'm willing the make a PR, but do you think we should introduce this change as an optional change or just hard-code it?

P.s I'll be changing the mappings inside of shapping_resolver._charForms

RangeError (index): Invalid value: Valid value range is empty

Hi
A bug has appeared on line 95 of src/paragraph.dart (_removeBidiMarkers method):
RangeError (index): Invalid value: Valid value range is empty

To Reproduce:

print(bidi.logicalToVisual('\u200E+'));

DavBfr/dart_pdf#1524

Null safety

Hi, any plans to convert this code to null-safe?

[Bug] When Arabic letter has a HAMZA-form reshaping throws an error

first of all, thank you for this great package.
I've noticed that when a letter of the sentence has a HAMZA an error occurs.
I think the problem is letters with Hamza should be reshaped not decomposed into a base letter and a diacritic.

All of these throw an out of range error

  bidi.logicalToVisual('أ');
  bidi.logicalToVisual('إ');
  bidi.logicalToVisual('ؤ');
  bidi.logicalToVisual('ئ');

stacktrace

RangeError (index): Invalid value: Only valid value is 0: 1
dart:core                               List.[]
package:bidi/src/paragraph.dart 752:24  Paragraph.internalCompose
package:bidi/src/paragraph.dart 113:5   Paragraph.normalizeText
package:bidi/src/paragraph.dart 42:5    Paragraph.text=
package:bidi/src/paragraph.dart 13:10   new Paragraph
package:bidi/src/bidi.dart 73:13        splitStringToParagraphs
package:bidi/src/bidi.dart 9:16         logicalToVisual
test/arabic_test.dart 40:8              main

these don't throw an error but the result is incorrect

  bidi.logicalToVisual('خطأ');
  bidi.logicalToVisual('كؤ');
  bidi.logicalToVisual('مئ');