2 files changed, 129 insertions, 0 deletions
diff --git a/gui/text/concurrent_face.go b/gui/text/concurrent_face.go
new file mode 100644
index 0000000..c865251
--- /dev/null
+++ b/gui/text/concurrent_face.go
@@ -0,0 +1,51 @@
+package text
+
+import (
+	"image"
+	"sync"
+
+	"golang.org/x/image/font"
+	"golang.org/x/image/math/fixed"
+)
+
+type concurrentFace struct {
+	mu   sync.Mutex
+	face font.Face
+}
+
+func (cf *concurrentFace) Close() error {
+	cf.mu.Lock()
+	defer cf.mu.Unlock()
+	return cf.face.Close()
+}
+
+func (cf *concurrentFace) Glyph(dot fixed.Point26_6, r rune) (
+	dr image.Rectangle, mask image.Image, maskp image.Point, advance fixed.Int26_6, ok bool) {
+	cf.mu.Lock()
+	defer cf.mu.Unlock()
+	return cf.face.Glyph(dot, r)
+}
+
+func (cf *concurrentFace) GlyphBounds(r rune) (bounds fixed.Rectangle26_6, advance fixed.Int26_6, ok bool) {
+	cf.mu.Lock()
+	defer cf.mu.Unlock()
+	return cf.face.GlyphBounds(r)
+}
+
+func (cf *concurrentFace) GlyphAdvance(r rune) (advance fixed.Int26_6, ok bool) {
+	cf.mu.Lock()
+	defer cf.mu.Unlock()
+	return cf.face.GlyphAdvance(r)
+}
+
+func (cf *concurrentFace) Kern(r0, r1 rune) fixed.Int26_6 {
+	cf.mu.Lock()
+	defer cf.mu.Unlock()
+	return cf.face.Kern(r0, r1)
+}
+
+func (cf *concurrentFace) Metrics() font.Metrics {
+	cf.mu.Lock()
+	defer cf.mu.Unlock()
+	return cf.face.Metrics()
+}
diff --git a/gui/text/text.go b/gui/text/text.go
new file mode 100644
index 0000000..dfe60e1
--- /dev/null
+++ b/gui/text/text.go
@@ -0,0 +1,78 @@
+package text
+
+import (
+	"log"
+	"sync"
+
+	"image"
+	"image/color"
+	"image/draw"
+
+	"golang.org/x/image/font"
+	"golang.org/x/image/font/gofont/goregular"
+	"golang.org/x/image/font/opentype"
+	"golang.org/x/image/math/fixed"
+)
+
+var (
+	FONT      = goregular.TTF
+	FONT_SIZE = 15
+	DPI       = 72
+	PAD       = 3
+)
+
+var face *concurrentFace
+
+func init() {
+	fnt, err := opentype.Parse(FONT)
+	if err != nil {
+		log.Fatal(err)
+	}
+	fce, err := opentype.NewFace(fnt, &opentype.FaceOptions{
+		Size: float64(FONT_SIZE),
+		DPI:  float64(DPI),
+	})
+	if err != nil {
+		log.Fatal(err)
+	}
+	face = &concurrentFace{sync.Mutex{}, fce}
+}
+
+func Size(text string) image.Point {
+	bounds := textBounds([]byte(text), font.Drawer{Face: face})
+	return image.Point{bounds.Max.X - bounds.Min.X + 2*PAD, bounds.Max.Y - bounds.Min.Y + 2*PAD}
+}
+
+func Draw(text []byte, dst draw.Image, r image.Rectangle, fg, bg color.Color) {
+	drawer := font.Drawer{
+		Src:  &image.Uniform{fg},
+		Face: face,
+		Dot:  fixed.P(0, 0),
+	}
+
+	// background
+	draw.Draw(dst, r, &image.Uniform{bg}, image.ZP, draw.Src)
+
+	// text image
+	bounds := textBounds(text, drawer)
+	textImg := image.NewRGBA(bounds)
+	draw.Draw(textImg, bounds, &image.Uniform{bg}, image.ZP, draw.Src)
+	drawer.Dst = textImg
+	drawer.DrawBytes(text)
+
+	// draw text image over background
+	leftCentre := image.Pt(bounds.Min.X, (bounds.Min.Y+bounds.Max.Y)/2)
+	target := image.Pt(r.Max.X-bounds.Max.X-PAD, (r.Min.Y+r.Max.Y)/2)
+	delta := target.Sub(leftCentre)
+	draw.Draw(dst, bounds.Add(delta).Intersect(r), drawer.Dst, bounds.Min, draw.Src)
+}
+
+func textBounds(text []byte, drawer font.Drawer) image.Rectangle {
+	b, _ := drawer.BoundBytes(text)
+	return image.Rect(
+		b.Min.X.Floor(),
+		b.Min.Y.Floor(),
+		b.Max.X.Ceil(),
+		b.Max.Y.Ceil(),
+	)
+}