The Free Implementation of the Unicode Bidirectional Algorithm.
One of the missing links stopping the penetration of free software in Middle East is the lack of support for the Arabic and Hebrew alphabets. In order to have proper Arabic and Hebrew support, the bidi algorithm needs to be implemented. It is our hope that this library will stimulate more free software in the Middle Eastern countries.
HISTORY on how the project started and evolved.
It is our hope that this library will stimulate the implementation of Hebrew and Arabic support in lots of Free Software. Here is a small list of projects that would benefit from the use of the GNU FriBidi library, but of course there are many more: Wine, Mozilla, Qt, KDE, lynx, OpenOffice.
USERS for a list of projects using GNU FriBidi.
Currently GNU FriBidi does not depend on any other library, but uses Glib if available. It uses GNU Build System for build and installation on POSIX systems.
The latest version of GNU FriBidi may be found at: https://github.com/fribidi/fribidi
Start with running the
bootstrap script and follow the
GNU FriBidi is Free Software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version.
GNU FriBidi is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License along with GNU FriBidi, in a file named COPYING; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
For licensing issues, contact email@example.com.
The library implements the algorithm described in the "Unicode Standard Annex #9, The Bidirectional Algorithm", available at http://www.unicode.org/unicode/reports/tr9/.
The library uses Unicode (UTF-32) entirely. The character properties are automatically extracted from the Unicode data files, available from http://www.unicode.org/Public/UNIDATA/. This means that every Unicode character is treated in strict accordance with the Unicode specification.
There is a limited support for character set conversion from/to the UTF-32 encoding. Data in these character sets must be converted into UTF-32 before the library may be used. iconv(3) can always do a better job on that, so you may find that the character sets conversion code is typically turned off on POSIX machines.
GNU Fribidi has been tested exhaustively against the Unicode Reference Code, and to the best of our knowledge, it completely conforms to the specification, always producing the same result as the Reference Code, except for Mirroring additions, introduced in Unicode 6.3.0 of the specification.
The reordering of characters is typically done through the function:
fribidi_boolean fribidi_log2vis( /* input */ FriBidiChar *str, FriBidiStrIndex len, FriBidiCharType *pbase_dir, /* output */ FriBidiChar *visual_str, FriBidiStrIndex *position_L_to_V_list, FriBidiStrIndex *position_V_to_L_list, FriBidiLevel *embedding_level_list )
stris the Unicode input string.
lenis the length of the Unicode string (
pbase_diris the input and output base direction. If
pbase_dir == FRIBIDI_TYPE_ONthen
fribidi_log2vis()calculates the base direction on its own, according to the bidi algorithm.
visual_stris the reordered output unicode string.
position_L_to_V_listmaps the positions in the logical string to positions in the visual string.
position_V_to_L_listmaps the positions in the visual string to the positions in the logical string.
embedding_level_listreturns the classification of each character. Here, even numerical levels indicate LTR characters, and odd levels indicate RTL characters. The main use of this list is in interactive applications where, for example, the embedding level determines cursor display.
If any of the output pointers is equal to
NULL, then that information is not
How it looks like
Have a look at
test/ directory, to see some input and outputs.
CapRTL charset means that CAPITAL letters are right to left, and digits
6, 7, 8, 9 are Arabic digits, try 'fribidi --charsetdesc CapRTL' for the full
There is also a command-line utilitity called
fribidi that loops over the text
of a file and performs the bidi algorithm on each line, also used for testing
fribidi --help to learn about usage.
The command-line utility is known to have problems with line-breaking and logical-to-vertical/vertical-to-logical lists.
Bug Reports and Feedback
Report bugs and general feedback at: https://github.com/fribidi/fribidi/issues
The mailing list is the place for additional technical discussions and user questions: https://lists.freedesktop.org/mailman/listinfo/fribidi