Comment 41 for bug 62587

(In reply to comment #20)
> We managed to get around this limitation by using Composite keys that map the
> presentation forms lam-alef ligatures to their "decomposed" codes. See #17228.
>

I believe you refer to the compose sequences at the end of the file,
http://cgit.freedesktop.org/xorg/lib/libX11/tree/nls/en_US.UTF-8/Compose.pre
(warning, big HTML file), which are

6290 XCOMM
6291 XCOMM Arabic Lam-Alef ligatures
6292 XCOMM
6293
6294 <UFEFB> : "لا" # ARABIC LIGATURE LAM WITH ALEF
6295 <UFEF7> : "لأ" # ARABIC LIGATURE LAM WITH ALEF WITH HAMZA ABOVE
6296 <UFEF9> : "لإ" # ARABIC LIGATURE LAM WITH ALEF WITH HAMZA BELOW
6297 <UFEF5> : "لآ" # ARABIC LIGATURE LAM WITH ALEF WITH MADDA ABOVE

I am interested in adding these sequences to GTK+ IM.
Could you please tell me how I can test that these work?

Which Arabic layout/variant shall I activate,
what keys I should press and
what I am expected to get?