Substitution function
dynamic
Substitution()
Add a substitution to a feature for a given script and language.
@param {string} feature - 4-letter feature name
@param {Object} sub - the substitution to add (an object like { sub: id or ids
, by: id or ids
})
@param {string} script='DFLT'
@param {string} language='dflt'
Implementation
function Substitution(font) {
Layout.call(this, font, 'gsub');
}