Bitstream Panorama: a global text composition engine

Complex Scripts: Arabic: Alternate Contextual Glyphs
In Arabic, the shape of a character changes depending on whether or not it is isolated or at the beginning, middle, or end of a word. The character shape also depends on the characters surrounding it. For example, the shape of the character Jeem (highlighted in color) changes depending on what character follows it.

Not only the shape but also the position of the character changes (line two below).

Note that in Arabic, the initial position is on the right.

Images courtesy of Sakkal Design

The same theory applies to Indic, as shown on the next page.