#14 Arabic small high footnote marker (U+08E0) should be combining above and not spacing

[Philippe Verdy]

Arabic small high footnote marker ‹◌࣠ › (U+08E0): Quranic annotation sign.

This diacritic is incorrectly rendered in PakType fonts as a spacing mark on the baseline. It should be a mark above a base Arabic letter such as ‹ٮ࣠› (combined above U+066E ‹ٮ࣠› ARABIC LETTER DOTLESS BEH), or above the dotted circle as above (Unicode standard way to refer to the diacritic in text) or above a (non-breaking) space such as ‹ ࣠›.

When combined, it may extend above other surrounding letters or space on the right (e.g. in presence of other diacritics like Tashkil vowel points, or hamza above, or maddah above, or Arabic dots that are inseparable parts of Arabic letters and not encoded separately from them).

But ideally it should be centered above the base character (notably the dotted circle or non-breaking space) if it has no other diacritics above.

You may need to check also other combining Quranic annotation marks encoded in the following Unicode blocks: Arabic (U+0615, U+0617-061A, U+06D6-06D7, U+06D8-06DC, U+06DF-06E4, U+06E7-06E8, U+06EA- 06ED), Arabic Extended-A (U+08D3-08DB, U+08E0-08E1, U+08F0-08F3), Arabic Extended-B (U+0898-089F), and Arabic Extended-C (U+10EFA-10EFF); some of them are combining small ligatures, or are combining below instead of above.

[Philippe Verdy]

Note that when combining it above a space (U+0020 or U+00A0), the combination may need to widened and may be larger than this space; the same is true when combining with the Arabic kashida. Not all Arabic fonts are making this width adjusment (and do not correctly position it above spaces, kashida or dotted circle, however they all display it above the baseline, not on the baseline).

This change of metrics is normally not needed when combining this marker above the dotted circle, where the diacritic should fit in the width without needing an adjustment (but this may not be true for other combining Quranic annotation signs, notably "large" combining small ligatures, where such width adjusment for the combined pair would still be needed with the dotted circle like it is needed with a base space or kashida).

The ideal position of these Quranic diacritic on the base character is that it extends from the left side above Arabic letters, otherwise it is centered above spaces, kashidas or dotted circle. These Quranic diacritic is normally used on the last letter of words (in Nastaliq/Urdu style ir may be accordingly slanted upward in the backward direction to the right, but no complex positioning is normally needed of that case as the last letter of words is on the main horizontal baseline and not elevated like other leading letters or words)

As the Nasthaliq style is slanted, it usually requires a taller line-height (typically 1.6 or a bit higher to fit "long" words) than "standard" horizontal Arabic styles (typically 1.4 for Naskh or Kufic styles used on highway signs). This increased line-height means that these Quranic diacritics occuring above at end of words just need to be positioned at higher position than Tashkil points, to avoid collisions with them, without complex positioning management in Opentype for specific pairs (this contrasts with horizontal Arabic styles, where such position may need to be adapted, or where dots or Tashkil points may need to be "pushed" away a bit leftwards to avoid collisions, if we want to render correctly with a normal 1.4 line-height without collisions with previous lines of text).