Version 1.0, 5 April 2022
Version history:
1.0, 5 April 2022
What are combining double marks?
‘Combining double marks’ or ‘combining double diacritics’ are diacritics that are applied to a sequence of two letters. In the words of The Unicode Standard v. 14.0, Chapter 7, section 7.9, p. 331: “In rendering, these marks of unusual size appear as wide diacritics spanning across the top (or bottom) of the two base characters. The Unicode Standard contains a set of double-diacritic combining marks to represent such forms. Like all other combining nonspacing marks, these marks apply to the previous base character, but they are intended to hang over the following letter as well.”
Example:
COMBINING DOUBLE TILDE U+0360 = ◌͠
n + ◌͠ → n͠
n + ◌͠ + g → n͠g
Limitations in Brill fonts
Note that in the Brill fonts up to and including version 4.0 the correct positioning of combining double diacritics in combination with base characters carrying other diacritics is not guaranteed, except for the combining overline ◌͞◌ (COMBINING DOUBLE MACRON U+035E) and the combining low line ◌͟◌ (COMBINING DOUBLE MACRON BELOW U+035F). The characters affected are:
◌͡◌ COMBINING DOUBLE INVERTED BREVE U+0361
◌͜◌ COMBINING DOUBLE BREVE BELOW U+035C
◌͝◌ COMBINING DOUBLE BREVE U+035D
◌᷼◌ COMBINING DOUBLE INVERTED BREVE BELOW U+1DFC
◌͠◌ COMBINING DOUBLE TILDE U+0360
◌͢◌ COMBINING DOUBLE RIGHTWARDS ARROW BELOW U+0362
◌᷍◌ COMBINING DOUBLE CIRCUMFLEX ABOVE U+1DCD
See the Unicode charts Combining Diacritical Marks and Combining Diacritical Marks Supplement.
So far, no priority was given to the large amount of extra OpenType programming that is necessary to ensure correct positioning of all double diacritics in all circumstances. (Some fonts, such as Times New Roman, provide a solution involving an ‘average’ sizing and positioning of combining double diacritics, but this is not a definitive solution.)
Solution in PDF production
Typesetters using Adobe InDesign (and LuaTeX as well) are able to adjust OpenType diacritic positioning on a case-by-case basis, so that correct positioning of double diacritics can be achieved during PDF production. The PDF attached to this page describes the procedure which is to be followed in Adobe InDesign. Although only U+0361 is treated, this procedure will also work for the other combining double marks.
Please note that a .png image is shown below, and that the link to the PDF file is below that. We chose to display a .png image in Confluence because of weird behavior of some characters in the PDF when viewed inline in the browser.
