From af91ce2a09a0e47a9807c14be1566ca92a16ae68 Mon Sep 17 00:00:00 2001
From: Chris Waldon <christopher.waldon.dev@gmail.com>
Date: Mon, 7 Nov 2022 10:33:04 -0500
Subject: [PATCH] styledtext: adapt to new text shaping APIs

This commit fixes up styledtext to use the new text shaping API. This mostly involved
changing its iteration strategy over lines and how it accessed line data. The most
complex change was to look up whether spans terminate with a newline in the rune data
instead of relying on an invalid text shaper heuristic.

Signed-off-by: Chris Waldon <christopher.waldon.dev@gmail.com>
---
 styledtext/styledtext.go | 46 ++++++++++++++++++++++++++++++----------
 1 file changed, 35 insertions(+), 11 deletions(-)

diff --git a/styledtext/styledtext.go b/styledtext/styledtext.go
index bf0f7b8..ba89284 100644
--- a/styledtext/styledtext.go
+++ b/styledtext/styledtext.go
@@ -28,7 +28,7 @@ type SpanStyle struct {
 // spanShape describes the text shaping of a single span.
 type spanShape struct {
 	offset image.Point
-	layout text.Layout
+	layout text.Line
 	size   image.Point
 	ascent int
 }
@@ -37,7 +37,7 @@ type spanShape struct {
 func (ss SpanStyle) Layout(gtx layout.Context, s text.Shaper, shape spanShape) layout.Dimensions {
 	paint.ColorOp{Color: ss.Color}.Add(gtx.Ops)
 	defer op.Offset(shape.offset).Push(gtx.Ops).Pop()
-	defer clip.Outline{Path: s.Shape(ss.Font, fixed.I(gtx.Sp(ss.Size)), shape.layout)}.Op().Push(gtx.Ops).Pop()
+	defer clip.Outline{Path: s.Shape(shape.layout)}.Op().Push(gtx.Ops).Pop()
 	paint.PaintOp{}.Add(gtx.Ops)
 	return layout.Dimensions{Size: shape.size}
 }
@@ -90,13 +90,37 @@ func (t TextStyle) Layout(gtx layout.Context, spanFn func(gtx layout.Context, id
 		maxWidth := gtx.Constraints.Max.X - lineDims.X
 
 		// shape the text of the current span
-		lines := t.Shaper.LayoutString(span.Font, fixed.I(gtx.Sp(span.Size)), maxWidth, gtx.Locale, span.Content)
+		shaped := t.Shaper.LayoutString(text.Parameters{
+			Font:    span.Font,
+			PxPerEm: fixed.I(gtx.Sp(span.Size)),
+		}, 0, maxWidth, gtx.Locale, span.Content)
+
+		shaped.SetViewport(image.Rectangle{Max: image.Pt(1e6, 1e6)})
 
 		// grab the first line of the result and compute its dimensions
-		firstLine := lines[0]
-		spanWidth := firstLine.Width.Ceil()
-		spanHeight := (firstLine.Ascent + firstLine.Descent).Ceil()
-		spanAscent := firstLine.Ascent.Ceil()
+		firstLine, ok := shaped.Next()
+		if !ok {
+			continue
+		}
+		width, ascent, descent := firstLine.Metrics()
+		_, multiLine := shaped.Next()
+		spanWidth := width.Ceil()
+		spanHeight := (ascent + descent).Ceil()
+		spanAscent := ascent.Ceil()
+		runeCount := firstLine.Runes()
+		if runeCount > 0 && !multiLine {
+			// synthesize and insert a new span
+			byteLen := 0
+			var lastRune rune
+			var n int
+			for i := 0; i < firstLine.Runes(); i++ {
+				lastRune, n = utf8.DecodeRuneInString(span.Content[byteLen:])
+				byteLen += n
+			}
+			if lastRune == '\n' {
+				multiLine = true
+			}
+		}
 
 		// forceToNextLine handles the case in which the first segment of the new span does not fit
 		// AND there is already content on the current line. If there is no content on the line,
@@ -109,7 +133,7 @@ func (t TextStyle) Layout(gtx layout.Context, spanFn func(gtx layout.Context, id
 			lineShapes = append(lineShapes, spanShape{
 				offset: image.Point{X: lineDims.X},
 				size:   image.Point{X: spanWidth, Y: spanHeight},
-				layout: firstLine.Layout,
+				layout: firstLine,
 				ascent: spanAscent,
 			})
 			// update the dimensions of the current line
@@ -130,7 +154,7 @@ func (t TextStyle) Layout(gtx layout.Context, spanFn func(gtx layout.Context, id
 
 		// if we are breaking the current span across lines or we are on the
 		// last span, lay out all of the spans for the line.
-		if len(lines) > 1 || i == len(spans)-1 || forceToNextLine {
+		if multiLine || i == len(spans)-1 || forceToNextLine {
 			lineMacro := op.Record(gtx.Ops)
 			for i, shape := range lineShapes {
 				// lay out this span
@@ -178,7 +202,7 @@ func (t TextStyle) Layout(gtx layout.Context, spanFn func(gtx layout.Context, id
 		}
 
 		// if the current span breaks across lines
-		if len(lines) > 1 && !forceToNextLine {
+		if multiLine && !forceToNextLine {
 			// mark where the next line to be laid out starts
 			lineStartIndex = i + 1
 			lineDims = image.Point{}
@@ -192,7 +216,7 @@ func (t TextStyle) Layout(gtx layout.Context, spanFn func(gtx layout.Context, id
 			}
 			// synthesize and insert a new span
 			byteLen := 0
-			for i := 0; i < firstLine.Layout.Runes.Count; i++ {
+			for i := 0; i < firstLine.Runes(); i++ {
 				_, n := utf8.DecodeRuneInString(span.Content[byteLen:])
 				byteLen += n
 			}
-- 
2.45.2