Method generateFontAtlas

common/font.go:197–300

generateFontAtlas generates the font atlas for this given font, using the first `c` Unicode characters.

(c int)

// generateFontAtlas generates the font atlas for this given font, using the first `c` Unicode characters.
func (f *Font) generateFontAtlas(c int) FontAtlas {
	atlas := FontAtlas{
		XLocation: make([]float32, c),
		YLocation: make([]float32, c),
		Width:     make([]float32, c),
		Height:    make([]float32, c),
		OffsetX:   make([]float32, c),
		RightSide: make([]float32, c),
		OffsetY:   make([]float32, c),
	}

	currentX := float32(0)
	currentY := float32(0)

	// Default colors
	if f.FG == nil {
		f.FG = color.NRGBA{0, 0, 0, 0}
	}
	if f.BG == nil {
		f.BG = color.NRGBA{0, 0, 0, 0}
	}

	d := &font.Drawer{}
	d.Src = image.NewUniform(f.FG)
	d.Face = truetype.NewFace(f.TTF, &truetype.Options{
		Size:    f.Size,
		DPI:     dpi,
		Hinting: font.HintingNone,
	})

	lineHeight := d.Face.Metrics().Height
	ascent := d.Face.Metrics().Ascent
	prev := 0

	for i := 0; i < c; i++ {
		bounds, adv, ok := d.Face.GlyphBounds(rune(i))
		if !ok {
			continue
		}
		advance := float32(adv.Ceil())

		atlas.Width[i] = float32((bounds.Max.X - bounds.Min.X).Ceil())
		atlas.Height[i] = float32((bounds.Max.Y - bounds.Min.Y).Ceil())
		atlas.OffsetX[i] = float32(bounds.Min.X.Ceil())
		atlas.OffsetY[i] = float32((ascent + bounds.Min.Y).Ceil())
		atlas.RightSide[i] = advance - float32(bounds.Max.X.Ceil())

		if prev > 0 {
			currentX += float32(f.face.Kern(rune(prev), rune(i)).Ceil())
		}

		//overlapping characters
		if atlas.Width[i] > advance {
			if atlas.OffsetX[i] < 0 {
				advance -= atlas.OffsetX[i]
			} else if advance < float32(bounds.Max.X.Ceil()) {
				advance = float32(bounds.Max.X.Ceil())
			}