// DrawString draws s at p and returns p advanced by the text extent. The text
// is placed so that the left edge of the em square of the first character of s
// and the baseline intersect at p. The majority of the affected pixels will be
// above and to the right of the point, but some may be below or to the left.
// For example, drawing a string that starts with a 'J' in an italic font may
// affect pixels below and left of the point.
// p is a raster.Point and can therefore represent sub-pixel positions.
func (c *Context) DrawString(s string, p raster.Point) (raster.Point, error) {
if c.font == nil {
return raster.Point{}, errors.New("freetype: DrawText called with a nil font")
}
prev, hasPrev := truetype.Index(0), false
for _, rune := range s {
index := c.font.Index(rune)
if hasPrev {
kern := raster.Fix32(c.font.Kerning(c.scale, prev, index)) << 2
if c.hinting != NoHinting {
kern = (kern + 128) &^ 255
}
p.X += kern
}
advanceWidth, mask, offset, err := c.glyph(index, p)
if err != nil {
return raster.Point{}, err
}
p.X += advanceWidth
glyphRect := mask.Bounds().Add(offset)
dr := c.clip.Intersect(glyphRect)
if !dr.Empty() {
mp := image.Point{0, dr.Min.Y - glyphRect.Min.Y}
draw.DrawMask(c.dst, dr, c.src, image.ZP, mask, mp, draw.Over)
}
prev, hasPrev = index, true
}
return p, nil
}
func (ig *ImageGraphics) TextLen(s string, font chart.Font) int {
c := freetype.NewContext()
c.SetDPI(dpi)
c.SetFont(ig.font)
fontsize := ig.relFontsizeToPixel(font.Size)
c.SetFontSize(fontsize)
scale := int32(fontsize * dpi * (64.0 / 72.0))
var p raster.Point
prev, hasPrev := truetype.Index(0), false
for _, rune := range s {
index := ig.font.Index(rune)
if hasPrev {
p.X += raster.Fix32(ig.font.Kerning(scale, prev, index)) << 2
}
p.X += raster.Fix32(ig.font.HMetric(scale, index).AdvanceWidth) << 2
prev, hasPrev = index, true
}
return int((p.X + 127) / 256)
}
