Highlight Alternate Glyphs (8689863f) flagged any glyph that isn't its
character's cmap glyph, so the joining forms Arabic and other complex
scripts always take (init, medi, fina, isol, rlig, ccmp and the Indic
required set) covered ordinary text in pink. A glyph is now an
alternate only when required shaping alone doesn't give it: the text is
laid out again with every optional feature off (liga, clig, calt and
the features its characters turn on) and each candidate glyph compared
by cluster. The pink boxes are measured once per text geometry, only
when the preference shows them.
ham9zah