shiny/font: add per-glyph metrics.
Change-Id: Ie5c7e29b4eb7bd87b8e99de941f2f94b042e268f
Reviewed-on: https://go-review.googlesource.com/13827
Reviewed-by: Rob Pike <r@golang.org>
diff --git a/shiny/font/font.go b/shiny/font/font.go
index c370986..8f8f4c1 100644
--- a/shiny/font/font.go
+++ b/shiny/font/font.go
@@ -37,8 +37,9 @@
// 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
- // dot after adding the glyph's advance width. It returns !ok if the face
- // does not contain a glyph for r.
+ // dot after adding the glyph's advance width.
+ //
+ // 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
// after the next Glyph call. Callers that want to cache the mask must make
@@ -46,11 +47,26 @@
Glyph(dot fixed.Point26_6, r rune) (
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
// positive kern means to move the glyphs further apart.
Kern(r0, r1 rune) fixed.Int26_6
- // TODO: per-font and per-glyph Metrics.
+ // TODO: per-font Metrics.
// TODO: ColoredGlyph for various emoji?
// TODO: Ligatures? Shaping?
}
@@ -102,6 +118,7 @@
if !ok {
// TODO: is falling back on the U+FFFD glyph the responsibility of
// the Drawer or the Face?
+ // TODO: set prevC = '\ufffd'?
continue
}
draw.DrawMask(d.Dst, dr, d.Src, image.Point{}, mask, maskp, draw.Over)
@@ -109,6 +126,26 @@
}
}
+// 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.
//
// Not all fonts support hinting.
diff --git a/shiny/font/plan9font/plan9font.go b/shiny/font/plan9font/plan9font.go
index 35d6ee8..abcc655 100644
--- a/shiny/font/plan9font/plan9font.go
+++ b/shiny/font/plan9font/plan9font.go
@@ -94,6 +94,31 @@
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
// ends of the range are inclusive.
type runeRange struct {
@@ -121,6 +146,27 @@
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) {
+ 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.
for _, rr := range [2]rune{r, '\ufffd'} {
// We have to do linear, not binary search. plan9port's
@@ -148,10 +194,10 @@
}
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,
