// MeasureString returns the width and height of the string in s, in terms of
// raster.Fix32 units.
//
// BUG(burntsushi): I don't think negative x-coordinates are handled at all, so
// that the bounding box could be smaller than what it actually is. (i.e., the
// first letter is an italic 'J'.)
func (c *Context) MeasureString(s string) (raster.Fix32, raster.Fix32, error) {
if c.font == nil {
return 0, 0, errors.New("freetype: DrawText called with a nil font")
}
var width, height, heightMax raster.Fix32
oneLine := c.PointToFix32(c.fontSize) & 0xff
height = c.PointToFix32(c.fontSize)
prev, hasPrev := truetype.Index(0), false
for _, rune := range s {
index := c.font.Index(rune)
if hasPrev {
width += raster.Fix32(c.font.Kerning(c.scale, prev, index)) << 2
}
if err := c.glyphBuf.Load(c.font, c.scale, index, truetype.Hinting(c.hinting)); err != nil {
return 0, 0, err
}
ymax := oneLine - raster.Fix32(c.glyphBuf.B.YMin<<2) + 0xff
heightMax = max(heightMax, ymax)
width += raster.Fix32(c.font.HMetric(c.scale, index).AdvanceWidth) << 2
prev, hasPrev = index, true
}
if heightMax > 0 {
height += heightMax
}
return width, height, nil
}
// 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
}