text: add io.Reader Layout method to Shaper

use them for Editor, which is no longer required to construct a string
for laying out its content.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

widget/buffer.go

@@ -95,18 +95,30 @@ func (e *editBuffer) gapLen() int {
 	return e.gapend - e.gapstart
 }
 
+func (e *editBuffer) Reset() {
+	e.pos = 0
+}
+
 func (e *editBuffer) Read(p []byte) (int, error) {
 	if e.pos == e.len() {
 		return 0, io.EOF
 	}
-	var n int
+	var total int
 	if e.pos < e.gapstart {
-		n += copy(p, e.text[e.pos:e.gapstart])
+		n := copy(p, e.text[e.pos:e.gapstart])
 		p = p[n:]
+		total += n
+		e.pos += n
 	}
-	n += copy(p, e.text[e.gapend:])
-	e.pos += n
-	return n, nil
+	if e.pos >= e.gapstart {
+		n := copy(p, e.text[e.pos+e.gapLen():])
+		total += n
+		e.pos += n
+	}
+	if e.pos > e.len() {
+		panic("hey!")
+	}
+	return total, nil
 }
 
 func (e *editBuffer) ReadRune() (rune, int, error) {

widget/editor.go

@@ -273,13 +273,11 @@ func (e *Editor) layout(gtx *layout.Context, sh text.Shaper) {
 	}
 	e.shapes = e.shapes[:0]
 	for {
-		start, end, layout, off, ok := it.Next()
+		_, _, layout, off, ok := it.Next()
 		if !ok {
 			break
 		}
-		// TODO: remove
-		str := e.rr.String()[start:end]
-		path := sh.Shape(gtx, e.font, str, layout)
+		path := sh.Shape(gtx, e.font, layout)
 		e.shapes = append(e.shapes, line{off, path})
 	}
 
@@ -433,9 +431,9 @@ func (e *Editor) moveCoord(c unit.Converter, pos image.Point) {
 }
 
 func (e *Editor) layoutText(c unit.Converter, s text.Shaper, font text.Font) ([]text.Line, layout.Dimensions) {
-	txt := e.rr.String()
+	e.rr.Reset()
 	opts := text.LayoutOptions{MaxWidth: e.maxWidth}
-	lines := s.Layout(c, font, txt, opts)
+	lines, _ := s.Layout(c, font, &e.rr, opts)
 	dims := linesDimens(lines)
 	for i := 0; i < len(lines)-1; i++ {
 		// To avoid layout flickering while editing, assume a soft newline takes

widget/label.go

@@ -85,7 +85,7 @@ func (l *lineIterator) Next() (int, int, []text.Glyph, f32.Point, bool) {
 
 func (l Label) Layout(gtx *layout.Context, s text.Shaper, font text.Font, txt string) {
 	cs := gtx.Constraints
-	lines := s.Layout(gtx, font, txt, text.LayoutOptions{MaxWidth: cs.Width.Max})
+	lines := s.LayoutString(gtx, font, txt, text.LayoutOptions{MaxWidth: cs.Width.Max})
 	if max := l.MaxLines; max > 0 && len(lines) > max {
 		lines = lines[:max]
 	}
@@ -109,7 +109,7 @@ func (l Label) Layout(gtx *layout.Context, s text.Shaper, font text.Font, txt st
 		stack.Push(gtx.Ops)
 		op.TransformOp{}.Offset(off).Add(gtx.Ops)
 		str := txt[start:end]
-		s.Shape(gtx, font, str, layout).Add(gtx.Ops)
+		s.ShapeString(gtx, font, str, layout).Add(gtx.Ops)
 		paint.PaintOp{Rect: lclip}.Add(gtx.Ops)
 		stack.Pop()
 	}