text: consume io.Reader in shaper

io.Reader is actually a more efficient interface than io.RuneReader,
as we can pull bytes out and check for cache hits without doing
redundant rune<->string conversions. This isn't implemented yet,
however.

Signed-off-by: Chris Waldon <christopher.waldon.dev@gmail.com>

text/shaper.go

@@ -3,6 +3,7 @@
 package text
 
 import (
+	"bufio"
 	"fmt"
 	"io"
 	"strings"
@@ -182,6 +183,12 @@ func (l *Shaper) Layout(params Parameters, minWidth, maxWidth int, lc system.Loc
 	l.layoutText(params, minWidth, maxWidth, lc, txt, "")
 }
 
+// Layout text from an io.Reader according to a set of options. Results can be retrieved by
+// iteratively calling NextGlyph.
+func (l *Shaper) LayoutReader(params Parameters, minWidth, maxWidth int, lc system.Locale, txt io.Reader) {
+	l.layoutText(params, minWidth, maxWidth, lc, bufio.NewReader(txt), "")
+}
+
 // LayoutString is Layout for strings.
 func (l *Shaper) LayoutString(params Parameters, minWidth, maxWidth int, lc system.Locale, str string) {
 	l.layoutText(params, minWidth, maxWidth, lc, nil, str)

text/shaper_test.go

@@ -113,7 +113,7 @@ func TestShapingNewlineHandling(t *testing.T) {
 			}
 			checkGlyphs()
 
-			cache.Layout(Parameters{
+			cache.LayoutReader(Parameters{
 				Alignment: Middle,
 				PxPerEm:   fixed.I(10),
 			}, 200, 200, english, strings.NewReader(tc.textInput))