[NTG-context] ligatures/substituation at word boundaries

27 Jul 2017

      Is it possible to refer in fonts.handlers.otf.addfeature to the word
boundary? The luatex manual speaks of a virtual "left_boundary"
char, but I couldn't find a way to use it. 

\startluacode
    fonts.handlers.otf.addfeature {
        name = "ltest",
        type = "ligature",
        data = {
            ['1'] = { "a", "b" },
            ['2'] = { "d", "a" },
        }
    }
\stopluacode

%how to replace only the start a????

\startluacode
    fonts.handlers.otf.addfeature {
        name = "wtest",
        type = "ligature",
        data = {
            ['1'] = { "left_boundary", "a" },
        }
    }
\stopluacode

\definefontfeature[wtest][wtest=yes]
\definefontfeature[ltest][ltest=yes]
\starttext

    \definedfont[file:dejavu-serif.ttf*default]%

    {\addff{ltest} ababa\par}

    {\addff{wtest} ababa\par}

\stoptext

-- 
Ulrike Fischer 
http://www.troubleshooting-tex.de/