shiny/font: add per-glyph metrics.

Change-Id: Ie5c7e29b4eb7bd87b8e99de941f2f94b042e268f
Reviewed-on: https://go-review.googlesource.com/13827
Reviewed-by: Rob Pike <r@golang.org>
This commit is contained in:
Nigel Tao 2015-08-24 14:01:27 +10:00
parent ab08d42a8a
commit 627898392a
2 changed files with 88 additions and 5 deletions

View File

@ -37,8 +37,9 @@ type Face interface {
// Glyph returns the draw.DrawMask parameters (dr, mask, maskp) to draw r's // Glyph returns the draw.DrawMask parameters (dr, mask, maskp) to draw r's
// glyph at the sub-pixel destination location dot. It also returns the new // glyph at the sub-pixel destination location dot. It also returns the new
// dot after adding the glyph's advance width. It returns !ok if the face // dot after adding the glyph's advance width.
// does not contain a glyph for r. //
// It returns !ok if the face does not contain a glyph for r.
// //
// The contents of the mask image returned by one Glyph call may change // The contents of the mask image returned by one Glyph call may change
// after the next Glyph call. Callers that want to cache the mask must make // after the next Glyph call. Callers that want to cache the mask must make
@ -46,11 +47,26 @@ type Face interface {
Glyph(dot fixed.Point26_6, r rune) ( Glyph(dot fixed.Point26_6, r rune) (
newDot fixed.Point26_6, dr image.Rectangle, mask image.Image, maskp image.Point, ok bool) newDot fixed.Point26_6, dr image.Rectangle, mask image.Image, maskp image.Point, ok bool)
// GlyphBounds returns the bounding box of r's glyph, drawn at a dot equal
// to the origin, and that glyph's advance width.
//
// It returns !ok if the face does not contain a glyph for r.
//
// The glyph's ascent and descent equal -bounds.Min.Y and +bounds.Max.Y. A
// visual depiction of what these metrics are is at
// https://developer.apple.com/library/mac/documentation/TextFonts/Conceptual/CocoaTextArchitecture/Art/glyph_metrics_2x.png
GlyphBounds(r rune) (bounds fixed.Rectangle26_6, advance fixed.Int26_6, ok bool)
// GlyphAdvance returns the advance width of r's glyph.
//
// It returns !ok if the face does not contain a glyph for r.
GlyphAdvance(r rune) (advance fixed.Int26_6, ok bool)
// Kern returns the horizontal adjustment for the kerning pair (r0, r1). A // Kern returns the horizontal adjustment for the kerning pair (r0, r1). A
// positive kern means to move the glyphs further apart. // positive kern means to move the glyphs further apart.
Kern(r0, r1 rune) fixed.Int26_6 Kern(r0, r1 rune) fixed.Int26_6
// TODO: per-font and per-glyph Metrics. // TODO: per-font Metrics.
// TODO: ColoredGlyph for various emoji? // TODO: ColoredGlyph for various emoji?
// TODO: Ligatures? Shaping? // TODO: Ligatures? Shaping?
} }
@ -102,6 +118,7 @@ func (d *Drawer) DrawString(s string) {
if !ok { if !ok {
// TODO: is falling back on the U+FFFD glyph the responsibility of // TODO: is falling back on the U+FFFD glyph the responsibility of
// the Drawer or the Face? // the Drawer or the Face?
// TODO: set prevC = '\ufffd'?
continue continue
} }
draw.DrawMask(d.Dst, dr, d.Src, image.Point{}, mask, maskp, draw.Over) draw.DrawMask(d.Dst, dr, d.Src, image.Point{}, mask, maskp, draw.Over)
@ -109,6 +126,26 @@ func (d *Drawer) DrawString(s string) {
} }
} }
// MeasureString returns how far dot would advance by drawing s.
func (d *Drawer) MeasureString(s string) (advance fixed.Int26_6) {
var prevC rune
for i, c := range s {
if i != 0 {
advance += d.Face.Kern(prevC, c)
}
a, ok := d.Face.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
}
// Hinting selects how to quantize a vector font's glyph nodes. // Hinting selects how to quantize a vector font's glyph nodes.
// //
// Not all fonts support hinting. // Not all fonts support hinting.

View File

@ -94,6 +94,31 @@ func (f *subface) Glyph(dot fixed.Point26_6, r rune) (
return newDot, dr, f.img, image.Point{int(i.x), int(i.top)}, true return newDot, dr, f.img, image.Point{int(i.x), int(i.top)}, true
} }
func (f *subface) GlyphBounds(r rune) (bounds fixed.Rectangle26_6, advance fixed.Int26_6, ok bool) {
r -= f.firstRune
if r < 0 || f.n <= int(r) {
return fixed.Rectangle26_6{}, 0, false
}
i := &f.fontchars[r+0]
j := &f.fontchars[r+1]
bounds = fixed.R(
int(i.left),
int(i.top)-f.ascent,
int(i.left)+int(j.x-i.x),
int(i.bottom)-f.ascent,
)
return bounds, fixed.Int26_6(i.width) << 6, true
}
func (f *subface) GlyphAdvance(r rune) (advance fixed.Int26_6, ok bool) {
r -= f.firstRune
if r < 0 || f.n <= int(r) {
return 0, false
}
return fixed.Int26_6(f.fontchars[r].width) << 6, true
}
// runeRange maps a single rune range [lo, hi] to a lazily loaded subface. Both // runeRange maps a single rune range [lo, hi] to a lazily loaded subface. Both
// ends of the range are inclusive. // ends of the range are inclusive.
type runeRange struct { type runeRange struct {
@ -121,6 +146,27 @@ func (f *face) Kern(r0, r1 rune) fixed.Int26_6 { return 0 }
func (f *face) Glyph(dot fixed.Point26_6, r rune) ( func (f *face) Glyph(dot fixed.Point26_6, r rune) (
newDot fixed.Point26_6, dr image.Rectangle, mask image.Image, maskp image.Point, ok bool) { newDot fixed.Point26_6, dr image.Rectangle, mask image.Image, maskp image.Point, ok bool) {
if s, rr := f.subface(r); s != nil {
return s.Glyph(dot, rr)
}
return fixed.Point26_6{}, image.Rectangle{}, nil, image.Point{}, false
}
func (f *face) GlyphBounds(r rune) (bounds fixed.Rectangle26_6, advance fixed.Int26_6, ok bool) {
if s, rr := f.subface(r); s != nil {
return s.GlyphBounds(rr)
}
return fixed.Rectangle26_6{}, 0, false
}
func (f *face) GlyphAdvance(r rune) (advance fixed.Int26_6, ok bool) {
if s, rr := f.subface(r); s != nil {
return s.GlyphAdvance(rr)
}
return 0, false
}
func (f *face) subface(r rune) (*subface, rune) {
// Fall back on U+FFFD if we can't find r. // Fall back on U+FFFD if we can't find r.
for _, rr := range [2]rune{r, '\ufffd'} { for _, rr := range [2]rune{r, '\ufffd'} {
// We have to do linear, not binary search. plan9port's // We have to do linear, not binary search. plan9port's
@ -148,10 +194,10 @@ func (f *face) Glyph(dot fixed.Point26_6, r rune) (
} }
x.subface = sub.(*subface) x.subface = sub.(*subface)
} }
return x.subface.Glyph(dot, rr) return x.subface, rr
} }
} }
return fixed.Point26_6{}, image.Rectangle{}, nil, image.Point{}, false return nil, 0
} }
// ParseFont parses a Plan 9 font file. data is the contents of that font file, // ParseFont parses a Plan 9 font file. data is the contents of that font file,