Arabic - Lam-Alef ligatures
The lam-alef ligature is considered an obligatory ligature in most styles of Arabic writing. In the common hafs style of writing, the lam is the right part of the ligature, and the alef is the left side. There are eight lam characters and 30 alef characters encoded in Unicode. The potential for forming ligatures is quite large. Whatever that number is, it must be doubled, since lam-alef can be either in isolate or final position.
There are a few different styles for how a lam-alef ligature appears. The image below show some of the styles used in SIL fonts.
In most of the SIL Arabic fonts, the only lam-alef ligatures implemented are all of the lam characters (U+0644, U+06B5..U+06B8, U+076A, U+08A6, U+08C7) in conjunction with U+0622..U+0625, U+0627, U+0671..U+0673, and U+0773..U+0774. Ligatures were not implemented for U+0675 or U+0870..U+0882. The ones which are not included are not recommended for use (U+0675) or are not attested in actual practice (U+0870..U+0882).
The graphic below demonstrates lam-alef ligatures with ل and with all of the standard alef characters that are supported. It also shows ࢦ with the same alef characters. U+08A6 is shown because the position of the bars must be slightly altered in the ligature.
In Scheherazade New, lam-alef ligatures were also implemented with ل and with (U+0870..U+0882). Without examples, it was difficult to decide where to put some of the attached marks. Nevertheless, the image below demonstrates how these Quranic alef characters were implemented.
See Lam-Alef and Kashida
for implementation strategies.