Thank you, Mr. mekkablue
This debate contributed to the completion of programming Fonts here
http://www.zakdesign.net/index.php?showtopic=1844#entry18518
Thank you
I have a follow up question about breaking the ligatures in case of mark positioning (vocalisation). Specifically with the lam_meem-ar (and lam_meem-ar.init) ligatures. In most fonts, for example Adobe Arabic, this ligature can have vocalisation, but only for the meem, not for the lam. So when there is a vowel placed above or below the lam, the ligature breaks/does not form.
Can I create this exemption within glyphs?
And how do I name the anchors, since there should only be one top and one bottom anchor (belonging to meem)?
This is why Glyphs puts a lookupflag IgnoreMarks RightToLeft; before Arabic ligatures in the code.
What I mean is, I want to excempt lam_meem-ar.init and lam_meem-ar from the Ignore Marks lookup. When there is a mark after lam, it should break.
EDIT: Got it to work with two lookup groups.
So the other case, when you type lam, meem and then a mark belonging to meem, the placement of the marks to the ligatures does not work. How do I name the anchors in the lam-meem ligature (top, top_1, and top_2 don’t work) for the marks to be displayed correctly?
A ligature should not have a top anchor.
Not top, but top_1 and top_2 etc. Cmd-U autocreates them.
Yes, it works now, with top_1 and top_2, although top_1 is essentially a dead anchor. the lam in lam meem would not get an anchor, the ligature breaks in that case.