This is SheenFigure
An open source library to render arabic/urdu fonts on smartphones

Introduction
============

Sheen Figure is a library written in pure C language that allows rendering
of beautiful Nastaliq/Naskh script on mobile operating systems. With this
library, it is possible to use any Nastaliq or Naskh font. The fonts of
other scripts can also be used with a little addition of code in the library.

Technical Discussion
====================

As now you have read the basic purpose of this library, let's talk on it
in depth. First of all, let's see what it supports and what it does not.

Mobile OS
=========

Sheen Figure can be used in any mobile operating system that supports C
language. As of now, it has been ported to two popular mobile platforms
which are iOS from Apple inc. and android from Google inc. As android's
primary language is JAVA , therefore a wrapper is written in JNI to use
the functionality of the library.

Kinds
=====

For iOS, Sheen Figure consist of two kinds. One of them uses external
Freetype library to render glyphs while the other uses Apples' internal
CoreGraphics Framework.

For android, only Freetype can be used.

Compiling FreeType
==================

To compile FreeType, download its latest version from official website.
Then copy all the files in FreeType folder, open
FreeType/include/freetype/config/ftmodule.h and comment the lines containing
the following:
    1. autofit_module_class
    2. t1_driver_class
    3. t1cid_driver_class
    4. pfr_driver_class
    5. t42_driver_class
    6. winfnt_driver_class
    7. pcf_driver_class
    8. psaux_module_class
    9. bdf_driver_class

After making the given changes you can run either android or iOS sample app
and FreeType will be automatically compiled.

Font Limitations
================

If you read documentation of open type fonts, you will see that they provide
eight tables for substitution and nine tables for positioning of glyphs.
Some of the tables are common in substitution and positioning and some of
the tables further consist of more than one formats (or forms).

Eight substitution tables provided by open type fonts are:
    1. Single substitution table
    2. Multiple substitution table
    3. Alternate substitution table
    4. Ligature substitution table
    5. Context substitution table
    6. Chaining context substitution table
    7. Extension substitution table
    8. Reverse chaining context substitution table

Nine positioning table provided by open type fonts are:
    1. Single positioning table
    2. Pair positioning table
    3. Mark-to-base positioning table
    4. Mark-to-ligature positioning table
    5. Mark-to-mark positioning table
    6. Context positioning table
    7. Chaining context positioning table
    8. Extension positioning table
    9. Reverse chaining context positioning table

Among from all these tables Sheen Figure does not support just two tables
which are Context tables, and Reverse chaining context tables.

Moreover only 1st format is supported from chaining context tables. These
are not supported because I could not find a font using them. I could write
the code on theoretical basis for them as well but it would lead to crashing
of application while reading them.

BiDi (Bidirectional Algorithm)
==============================

Bidi is an algorithm used to correct the position of characters when words
from right-to- left and left-to-right languages are written together. Sheen
Figure make use of BiDi algorithm v4.0 so that RTL and LTR scripts can be
written together. But till now it supports only right-to-left direction.

Conclusion
==========

Sheen Figure is powerful enough to display any Nastaliq or Naskh font and
with a little addition, other scripts can also be used.