Bitstream Panorama: a global text composition engine

Complex Scripts: English: Alternate Contextual Glyphs
Using contextual alternates involves substituting characters depending on their position in a word or sentence. In the second row of the example below, uppercase swashes are substituted at initial positions, medial designs in the middle positions, and lowercase swashes in the trailing positions.

Note the difference in character designs for the "aa," "bb," and "ff" combinations in the second row.

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