text/shaper: Add Metrics method to Shaper struct.

Signed-off-by: Werner Laurensse <werner@alman.ax>

text/shaper.go

@@ -3,6 +3,7 @@
 package text
 
 import (
+	"golang.org/x/image/font"
 	"unicode/utf8"
 
 	"gioui.org/op"
@@ -51,6 +52,11 @@ func (s *Shaper) Shape(c unit.Converter, font Font, str String) op.CallOp {
 	return tf.shape(fixed.I(c.Px(font.Size)), str)
 }
 
+func (s *Shaper) Metrics(c unit.Converter, font Font) font.Metrics {
+	tf := s.faceForFont(font)
+	return tf.metrics(fixed.I(c.Px(font.Size)))
+}
+
 func (s *Shaper) faceForStyle(font Font) *face {
 	tf := s.faces[font]
 	if tf == nil {
@@ -115,6 +121,10 @@ func (t *face) shape(ppem fixed.Int26_6, str String) op.CallOp {
 	return clip
 }
 
+func (t *face) metrics(ppem fixed.Int26_6) font.Metrics {
+	return t.face.Metrics(ppem)
+}
+
 func fallbackLayout(str string) *Layout {
 	l := &Layout{
 		Lines: []Line{