Philippe Verdy: "And what about applying separate styles on components of a cluster (e.g. different color to an acute accent) : the difficulty is even worse due to selection of fonts and the way text renderers are selecting glyphs in fonts and positioning/substituting them (it does not work if glyphs are in distinct fonts or if sequences are only rendered correctly by fonts performing substitutions)."
Usual realization of ligature feature is sub f i by f_i; while more usable for editing, for caret positioning, for the components of cluster stupid styling is sub f before i by f.ligaleft; sub i after f by i.ligaright; pos f.ligaleft i.ligaright…; i. e. never use ligature substitution and to use decompositions wherever the user wish. Different fonts — different possibilities :(
