Combining cedilla is poorly placed on Windows fonts

[moyogo]

Several accented letters with cedilla are used in some languages in Cameroon, because the General Alphabet for Cameroon languages use the cedilla for nasality and top marks for tones.

Arial, Times New Roman, Tahoma, Segoe UI and Ebrima fail to position the combining cedilla appropriately on accented letters like Á̧á̧Í̧í̧Ó̧ó̧Ú̧ú̧ or Ā̧ā̧Ī̧ī̧Ō̧ō̧Ū̧ū̧. Other Windows fonts may have the same issue, but there’s a limited number of fonts that have the characters.

Even Calibri has the issue to a certain degree as it places the cedilla differently whether ther are other accents or not.

For reference, Cambria has some minor positioning issues but is useable, Segoe UI Variable Display and Bahnschrift seem good (although the positioning the cedilla on A could be on the right stem but that may be a stylistic choice).

[moyogo]

The situation is also dire for other vowel letters of the GACL, and that is in all those fonts. Additionaly other marks aren’t positionned properly either. For example Ɑ̧̂ɑ̧̂Æ̧̂æ̧̂Œ̧̂œ̧̂Ə̧̂ə̧̂Ɛ̧̂ɛ̧̂Ɔ̧̂ɔ̧̂Ɨ̧̂ɨ̧̂Ø̧̂ø̧̂Ʉ̧̂ʉ̧̂ɤ̧̂.

[tiroj]

Do you get better/different results depending on the order of the marks? In some of these cases the problem may be failure of mark filtering in the GPOS lookups.

[moyogo]

Do you get better/different results depending on the order of the marks? In some of these cases the problem may be failure of mark filtering in the GPOS lookups.

@tiroj Definitely different:	NFC	NFD

[alib-ms]

The NFD column gives you desired results?

[moyogo]

@alib-ms Yes and no.

Yes as NFD generally looks better for those characters that have different normalizations.

No, as í̧ī̧ are still problematic with NFD, or Cambrian and Segoe VF look better with NFC. Ɑ̧̂ɑ̧̂Æ̧̂æ̧̂Œ̧̂œ̧̂Ə̧̂ə̧̂Ɛ̧̂ɛ̧̂Ɔ̧̂ɔ̧̂Ɨ̧̂ɨ̧̂Ø̧̂ø̧̂Ʉ̧̂ʉ̧̂ɤ̧̂ don’t work in either NFD and NFC as the normalization gives the same sequences.