function _distanceToNextBreak( inlines, currentIdx, options, accu ) {

	accu = accu || 0;

	// end of the text
	if ( !inlines[ currentIdx ] ) return accu;

	const inline = inlines[ currentIdx ];

	// const kerning = inline.kerning ? inline.kerning : 0;
	// const xoffset = inline.xoffset ? inline.xoffset : 0;
	// const xadvance = inline.xadvance ? inline.xadvance : inline.width;

	// if inline.lineBreak is set, it is 'mandatory' or 'possible'
	if ( inline.lineBreak ) return accu + inline.xadvance;

	// no line break is possible on this character
	return _distanceToNextBreak(
		inlines,
		currentIdx + 1,
		options,
		accu + inline.xadvance + inline.xoffset + inline.kerning + options.LETTERSPACING
	);

}
get the distance in world coord to the next glyph defined
as break-line-safe ( like whitespace for instance )
@private