You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: font.go
    path of file: ./repos/gdlv/vendor/github.com/aarzilli/nucular
    
    the code of the file until where you have to start completion: package nucular

import (
	"image"
	"strings"

	"github.com/aarzilli/nucular/command"
	"github.com/aarzilli/nucular/font"
	"github.com/aarzilli/nucular/rect"

	ifont "golang.org/x/image/font"

    
func measureRunes(f font.Face, runes []rune) int {
	var advance fixed.Int26_6
	prevC := rune(-1)
	fc := f.Face
	for _, c := range runes {
		if prevC >= 0 {
			advance += fc.Kern(prevC, c)
		}
		a, ok := fc.GlyphAdvance(c)
		if !ok {
			// TODO: is falling back on the U+FFFD glyph the responsibility of
			// the Drawer or the Face?
			// TODO: set prevC = '\ufffd'?
			continue
		}
		advance += a
		prevC = c
	}
	return advance.Ceil()
}