text,widget{,/material}: [API] move all shaping parameters into text.Parameters

This commit moves the min/max width of shaped text and the text's Locale into
text.Parameters. They were previously passed as separate function parameters to
the shaper, but this made little sense and added visual noise. This is a breaking
change, but only if you previously invoked the shaping API directly.

Callers of text.(*Shaper).LayoutString should change:

    shaper.LayoutString(params, minWidth, maxWidth, locale, "string")

to

    params.MinWidth=minWidth
    params.MaxWidth=maxWidth
    params.Locale=locale
    shaper.LayoutString(params, "string")

Callers of text.(*Shaper).Layout should do likewise.

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

text/gotext.go

@@ -401,7 +401,7 @@ func (s *shaperImpl) shapeText(faces []font.Face, ppem fixed.Int26_6, lc system.
 }
 
 // shapeAndWrapText invokes the text shaper and returns wrapped lines in the shaper's native format.
-func (s *shaperImpl) shapeAndWrapText(faces []font.Face, params Parameters, maxWidth int, lc system.Locale, txt []rune) (_ []shaping.Line, truncated int) {
+func (s *shaperImpl) shapeAndWrapText(faces []font.Face, params Parameters, txt []rune) (_ []shaping.Line, truncated int) {
 	wc := shaping.WrapConfig{
 		TruncateAfterLines: params.MaxLines,
 	}
@@ -411,10 +411,10 @@ func (s *shaperImpl) shapeAndWrapText(faces []font.Face, params Parameters, maxW
 		}
 		// We only permit a single run as the truncator, regardless of whether more were generated.
 		// Just use the first one.
-		wc.Truncator = s.shapeText(faces, params.PxPerEm, lc, []rune(params.Truncator))[0]
+		wc.Truncator = s.shapeText(faces, params.PxPerEm, params.Locale, []rune(params.Truncator))[0]
 	}
 	// Wrap outputs into lines.
-	return s.wrapper.WrapParagraph(wc, maxWidth, txt, s.shapeText(faces, params.PxPerEm, lc, txt)...)
+	return s.wrapper.WrapParagraph(wc, params.MaxWidth, txt, s.shapeText(faces, params.PxPerEm, params.Locale, txt)...)
 }
 
 // replaceControlCharacters replaces problematic unicode
@@ -443,17 +443,17 @@ func replaceControlCharacters(in []rune) []rune {
 }
 
 // Layout shapes and wraps the text, and returns the result in Gio's shaped text format.
-func (s *shaperImpl) LayoutString(params Parameters, minWidth, maxWidth int, lc system.Locale, txt string) document {
+func (s *shaperImpl) LayoutString(params Parameters, txt string) document {
-	return s.LayoutRunes(params, minWidth, maxWidth, lc, []rune(txt))
+	return s.LayoutRunes(params, []rune(txt))
 }
 
 // Layout shapes and wraps the text, and returns the result in Gio's shaped text format.
-func (s *shaperImpl) Layout(params Parameters, minWidth, maxWidth int, lc system.Locale, txt io.RuneReader) document {
+func (s *shaperImpl) Layout(params Parameters, txt io.RuneReader) document {
 	s.scratchRunes = s.scratchRunes[:0]
 	for r, _, err := txt.ReadRune(); err != nil; r, _, err = txt.ReadRune() {
 		s.scratchRunes = append(s.scratchRunes, r)
 	}
-	return s.LayoutRunes(params, minWidth, maxWidth, lc, s.scratchRunes)
+	return s.LayoutRunes(params, s.scratchRunes)
 }
 
 func calculateYOffsets(lines []line) {
@@ -468,12 +468,12 @@ func calculateYOffsets(lines []line) {
 }
 
 // LayoutRunes shapes and wraps the text, and returns the result in Gio's shaped text format.
-func (s *shaperImpl) LayoutRunes(params Parameters, minWidth, maxWidth int, lc system.Locale, txt []rune) document {
+func (s *shaperImpl) LayoutRunes(params Parameters, txt []rune) document {
 	hasNewline := len(txt) > 0 && txt[len(txt)-1] == '\n'
 	if hasNewline {
 		txt = txt[:len(txt)-1]
 	}
-	ls, truncated := s.shapeAndWrapText(s.orderer.sortedFacesForStyle(params.Font), params, maxWidth, lc, replaceControlCharacters(txt))
+	ls, truncated := s.shapeAndWrapText(s.orderer.sortedFacesForStyle(params.Font), params, replaceControlCharacters(txt))
 
 	if truncated > 0 && hasNewline {
 		// We've truncated the newline, since it was at the end and we've truncated some amount of runes
@@ -484,7 +484,7 @@ func (s *shaperImpl) LayoutRunes(params Parameters, minWidth, maxWidth int, lc s
 	// Convert to Lines.
 	textLines := make([]line, len(ls))
 	for i := range ls {
-		otLine := toLine(&s.orderer, ls[i], lc.Direction)
+		otLine := toLine(&s.orderer, ls[i], params.Locale.Direction)
 		isFinalLine := i == len(ls)-1
 		if isFinalLine && hasNewline {
 			// If there was a trailing newline update the rune counts to include
@@ -536,7 +536,7 @@ func (s *shaperImpl) LayoutRunes(params Parameters, minWidth, maxWidth int, lc s
 	return document{
 		lines:      textLines,
 		alignment:  params.Alignment,
-		alignWidth: alignWidth(minWidth, textLines),
+		alignWidth: alignWidth(params.MinWidth, textLines),
 	}
 }
 

text/gotext_test.go

@@ -37,7 +37,11 @@ func TestEmptyString(t *testing.T) {
 	ltrFace, _ := opentype.Parse(goregular.TTF)
 	shaper := testShaper(ltrFace)
 
-	lines := shaper.LayoutRunes(Parameters{PxPerEm: ppem}, 0, 2000, english, []rune{})
+	lines := shaper.LayoutRunes(Parameters{
+		PxPerEm:  ppem,
+		MaxWidth: 2000,
+		Locale:   english,
+	}, []rune{})
 	if len(lines.lines) == 0 {
 		t.Fatalf("Layout returned no lines for empty string; expected 1")
 	}
@@ -110,7 +114,11 @@ func TestShapingAlignWidth(t *testing.T) {
 		},
 	} {
 		t.Run(tc.name, func(t *testing.T) {
-			lines := shaper.LayoutString(Parameters{PxPerEm: ppem}, tc.minWidth, tc.maxWidth, english, tc.str)
+			lines := shaper.LayoutString(Parameters{PxPerEm: ppem,
+				MinWidth: tc.minWidth,
+				MaxWidth: tc.maxWidth,
+				Locale:   english,
+			}, tc.str)
 			if lines.alignWidth != tc.expected {
 				t.Errorf("expected line alignWidth to be %d, got %d", tc.expected, lines.alignWidth)
 			}
@@ -155,7 +163,11 @@ func TestNewlineSynthesis(t *testing.T) {
 	} {
 		t.Run(tc.name, func(t *testing.T) {
 
-			doc := shaper.LayoutRunes(Parameters{PxPerEm: ppem}, 0, 200, tc.locale, []rune(tc.txt))
+			doc := shaper.LayoutRunes(Parameters{
+				PxPerEm:  ppem,
+				MaxWidth: 200,
+				Locale:   tc.locale,
+			}, []rune(tc.txt))
 			for lineIdx, line := range doc.lines {
 				lastRunIdx := len(line.runs) - 1
 				lastRun := line.runs[lastRunIdx]
@@ -256,8 +268,16 @@ func makeTestText(shaper *shaperImpl, primaryDir system.TextDirection, fontSize,
 			rtlSource = string(complexRunes[:runeLimit])
 		}
 	}
-	simpleText, _ := shaper.shapeAndWrapText(shaper.orderer.sortedFacesForStyle(Font{}), Parameters{PxPerEm: fixed.I(fontSize)}, lineWidth, locale, []rune(simpleSource))
+	simpleText, _ := shaper.shapeAndWrapText(shaper.orderer.sortedFacesForStyle(Font{}), Parameters{
-	complexText, _ := shaper.shapeAndWrapText(shaper.orderer.sortedFacesForStyle(Font{}), Parameters{PxPerEm: fixed.I(fontSize)}, lineWidth, locale, []rune(complexSource))
+		PxPerEm:  fixed.I(fontSize),
+		MaxWidth: lineWidth,
+		Locale:   locale,
+	}, []rune(simpleSource))
+	complexText, _ := shaper.shapeAndWrapText(shaper.orderer.sortedFacesForStyle(Font{}), Parameters{
+		PxPerEm:  fixed.I(fontSize),
+		MaxWidth: lineWidth,
+		Locale:   locale,
+	}, []rune(complexSource))
 	testShaper(rtlFace, ltrFace)
 	return simpleText, complexText
 }
@@ -536,7 +556,11 @@ func FuzzLayout(f *testing.F) {
 		if fontSize < 1 {
 			fontSize = 1
 		}
-		lines := shaper.LayoutRunes(Parameters{PxPerEm: fixed.I(int(fontSize))}, 0, int(width), locale, []rune(txt))
+		lines := shaper.LayoutRunes(Parameters{
+			PxPerEm:  fixed.I(int(fontSize)),
+			MaxWidth: int(width),
+			Locale:   locale,
+		}, []rune(txt))
 		validateLines(t, lines.lines, len([]rune(txt)))
 	})
 }
@@ -595,11 +619,15 @@ func TestTextAppend(t *testing.T) {
 	shaper := testShaper(ltrFace, rtlFace)
 
 	text1 := shaper.LayoutString(Parameters{
-		PxPerEm: fixed.I(14),
+		PxPerEm:  fixed.I(14),
-	}, 0, 200, english, "د عرمثال dstي met لم aqل جدmوpمg lرe dرd  لو عل ميrةsdiduntut lab renنيتذدagلaaiua.ئPocttأior رادرsاي mيrbلmnonaيdتد ماةعcلخ.")
+		MaxWidth: 200,
+		Locale:   english,
+	}, "د عرمثال dstي met لم aqل جدmوpمg lرe dرd  لو عل ميrةsdiduntut lab renنيتذدagلaaiua.ئPocttأior رادرsاي mيrbلmnonaيdتد ماةعcلخ.")
 	text2 := shaper.LayoutString(Parameters{
-		PxPerEm: fixed.I(14),
+		PxPerEm:  fixed.I(14),
-	}, 0, 200, english, "د عرمثال dstي met لم aqل جدmوpمg lرe dرd  لو عل ميrةsdiduntut lab renنيتذدagلaaiua.ئPocttأior رادرsاي mيrbلmnonaيdتد ماةعcلخ.")
+		MaxWidth: 200,
+		Locale:   english,
+	}, "د عرمثال dstي met لم aqل جدmوpمg lرe dرd  لو عل ميrةsdiduntut lab renنيتذدagلaaiua.ئPocttأior رادرsاي mيrbلmnonaيdتد ماةعcلخ.")
 
 	text1.append(text2)
 	curY := math.MinInt

text/shaper.go

@@ -31,6 +31,11 @@ type Parameters struct {
 	// can currently ohly happen if MaxLines is nonzero and the text on the final line is
 	// truncated.
 	Truncator string
+	// MinWidth and MaxWidth provide the minimum and maximum horizontal space constraints
+	// for the shaped text.
+	MinWidth, MaxWidth int
+	// Locale provides primary direction and language information for the shaped text.
+	Locale system.Locale
 }
 
 // A FontFace is a Font and a matching Face.
@@ -194,13 +199,13 @@ func NewShaper(collection []FontFace) *Shaper {
 
 // Layout text from an io.Reader according to a set of options. Results can be retrieved by
 // iteratively calling NextGlyph.
-func (l *Shaper) Layout(params Parameters, minWidth, maxWidth int, lc system.Locale, txt io.Reader) {
+func (l *Shaper) Layout(params Parameters, txt io.Reader) {
-	l.layoutText(params, minWidth, maxWidth, lc, bufio.NewReader(txt), "")
+	l.layoutText(params, bufio.NewReader(txt), "")
 }
 
 // LayoutString is Layout for strings.
-func (l *Shaper) LayoutString(params Parameters, minWidth, maxWidth int, lc system.Locale, str string) {
+func (l *Shaper) LayoutString(params Parameters, str string) {
-	l.layoutText(params, minWidth, maxWidth, lc, nil, str)
+	l.layoutText(params, nil, str)
 }
 
 func (l *Shaper) reset(align Alignment) {
@@ -213,10 +218,10 @@ func (l *Shaper) reset(align Alignment) {
 // layoutText lays out a large text document by breaking it into paragraphs and laying
 // out each of them separately. This allows the shaping results to be cached independently
 // by paragraph. Only one of txt and str should be provided.
-func (l *Shaper) layoutText(params Parameters, minWidth, maxWidth int, lc system.Locale, txt io.RuneReader, str string) {
+func (l *Shaper) layoutText(params Parameters, txt io.RuneReader, str string) {
 	l.reset(params.Alignment)
 	if txt == nil && len(str) == 0 {
-		l.txt.append(l.layoutParagraph(params, minWidth, maxWidth, lc, "", nil))
+		l.txt.append(l.layoutParagraph(params, "", nil))
 		return
 	}
 	truncating := params.MaxLines > 0
@@ -250,7 +255,7 @@ func (l *Shaper) layoutText(params Parameters, minWidth, maxWidth int, lc system
 			done = endByte == len(str)
 		}
 		if startByte != endByte || (len(l.paragraph) > 0 || len(l.txt.lines) == 0) {
-			lines := l.layoutParagraph(params, minWidth, maxWidth, lc, str[startByte:endByte], l.paragraph)
+			lines := l.layoutParagraph(params, str[startByte:endByte], l.paragraph)
 			if truncating {
 				params.MaxLines -= len(lines.lines)
 				if params.MaxLines == 0 {
@@ -285,7 +290,7 @@ func (l *Shaper) layoutText(params Parameters, minWidth, maxWidth int, lc system
 	}
 }
 
-func (l *Shaper) layoutParagraph(params Parameters, minWidth, maxWidth int, lc system.Locale, asStr string, asRunes []rune) document {
+func (l *Shaper) layoutParagraph(params Parameters, asStr string, asRunes []rune) document {
 	if l == nil {
 		return document{}
 	}
@@ -294,14 +299,14 @@ func (l *Shaper) layoutParagraph(params Parameters, minWidth, maxWidth int, lc s
 	}
 	// Alignment is not part of the cache key because changing it does not impact shaping.
 	lk := layoutKey{
-		truncator: params.Truncator,
 		ppem:      params.PxPerEm,
-		maxWidth:  maxWidth,
+		maxWidth:  params.MaxWidth,
-		minWidth:  minWidth,
+		minWidth:  params.MinWidth,
 		maxLines:  params.MaxLines,
-		str:       asStr,
+		truncator: params.Truncator,
-		locale:    lc,
+		locale:    params.Locale,
 		font:      params.Font,
+		str:       asStr,
 	}
 	if l, ok := l.layoutCache.Get(lk); ok {
 		return l
@@ -309,7 +314,7 @@ func (l *Shaper) layoutParagraph(params Parameters, minWidth, maxWidth int, lc s
 	if len(asRunes) == 0 && len(asStr) > 0 {
 		asRunes = []rune(asStr)
 	}
-	lines := l.shaper.LayoutRunes(params, minWidth, maxWidth, lc, asRunes)
+	lines := l.shaper.LayoutRunes(params, asRunes)
 	l.layoutCache.Put(lk, lines)
 	return lines
 }

text/shaper_test.go

@@ -25,7 +25,10 @@ func TestWrappingTruncation(t *testing.T) {
 	cache.LayoutString(Parameters{
 		Alignment: Middle,
 		PxPerEm:   fixed.I(10),
-	}, 200, 200, english, textInput)
+		MinWidth:  200,
+		MaxWidth:  200,
+		Locale:    english,
+	}, textInput)
 	untruncatedCount := len(cache.txt.lines)
 
 	for i := untruncatedCount + 1; i > 0; i-- {
@@ -34,7 +37,10 @@ func TestWrappingTruncation(t *testing.T) {
 				Alignment: Middle,
 				PxPerEm:   fixed.I(10),
 				MaxLines:  i,
-			}, 200, 200, english, textInput)
+				MinWidth:  200,
+				MaxWidth:  200,
+				Locale:    english,
+			}, textInput)
 			lineCount := 0
 			lastGlyphWasLineBreak := false
 			glyphs := []Glyph{}
@@ -130,7 +136,10 @@ func TestShapingNewlineHandling(t *testing.T) {
 			cache.LayoutString(Parameters{
 				Alignment: Middle,
 				PxPerEm:   fixed.I(10),
-			}, 200, 200, english, tc.textInput)
+				MinWidth:  200,
+				MaxWidth:  200,
+				Locale:    english,
+			}, tc.textInput)
 			if lineCount := len(cache.txt.lines); lineCount > tc.expectedLines {
 				t.Errorf("shaping string %q created %d lines", tc.textInput, lineCount)
 			}
@@ -139,7 +148,10 @@ func TestShapingNewlineHandling(t *testing.T) {
 			cache.Layout(Parameters{
 				Alignment: Middle,
 				PxPerEm:   fixed.I(10),
-			}, 200, 200, english, strings.NewReader(tc.textInput))
+				MinWidth:  200,
+				MaxWidth:  200,
+				Locale:    english,
+			}, strings.NewReader(tc.textInput))
 			if lineCount := len(cache.txt.lines); lineCount > tc.expectedLines {
 				t.Errorf("shaping reader %q created %d lines", tc.textInput, lineCount)
 			}
@@ -157,7 +169,10 @@ func TestCacheEmptyString(t *testing.T) {
 	cache.LayoutString(Parameters{
 		Alignment: Middle,
 		PxPerEm:   fixed.I(10),
-	}, 200, 200, english, "")
+		MinWidth:  200,
+		MaxWidth:  200,
+		Locale:    english,
+	}, "")
 	glyphs := make([]Glyph, 0, 1)
 	for g, ok := cache.NextGlyph(); ok; g, ok = cache.NextGlyph() {
 		glyphs = append(glyphs, g)
@@ -190,31 +205,38 @@ func TestCacheAlignment(t *testing.T) {
 	ltrFace, _ := opentype.Parse(goregular.TTF)
 	collection := []FontFace{{Face: ltrFace}}
 	cache := NewShaper(collection)
-	params := Parameters{Alignment: Start, PxPerEm: fixed.I(10)}
+	params := Parameters{
-	cache.LayoutString(params, 200, 200, english, "A")
+		Alignment: Start,
+		PxPerEm:   fixed.I(10),
+		MinWidth:  200,
+		MaxWidth:  200,
+		Locale:    english,
+	}
+	cache.LayoutString(params, "A")
 	glyph, _ := cache.NextGlyph()
 	startX := glyph.X
 	params.Alignment = Middle
-	cache.LayoutString(params, 200, 200, english, "A")
+	cache.LayoutString(params, "A")
 	glyph, _ = cache.NextGlyph()
 	middleX := glyph.X
 	params.Alignment = End
-	cache.LayoutString(params, 200, 200, english, "A")
+	cache.LayoutString(params, "A")
 	glyph, _ = cache.NextGlyph()
 	endX := glyph.X
 	if startX == middleX || startX == endX || endX == middleX {
 		t.Errorf("[LTR] shaping with with different alignments should not produce the same X, start %d, middle %d, end %d", startX, middleX, endX)
 	}
+	params.Locale = arabic
 	params.Alignment = Start
-	cache.LayoutString(params, 200, 200, arabic, "A")
+	cache.LayoutString(params, "A")
 	glyph, _ = cache.NextGlyph()
 	rtlStartX := glyph.X
 	params.Alignment = Middle
-	cache.LayoutString(params, 200, 200, arabic, "A")
+	cache.LayoutString(params, "A")
 	glyph, _ = cache.NextGlyph()
 	rtlMiddleX := glyph.X
 	params.Alignment = End
-	cache.LayoutString(params, 200, 200, arabic, "A")
+	cache.LayoutString(params, "A")
 	glyph, _ = cache.NextGlyph()
 	rtlEndX := glyph.X
 	if rtlStartX == rtlMiddleX || rtlStartX == rtlEndX || rtlEndX == rtlMiddleX {
@@ -250,8 +272,10 @@ func TestCacheGlyphConverstion(t *testing.T) {
 		t.Run(tc.name, func(t *testing.T) {
 			cache := NewShaper(collection)
 			cache.LayoutString(Parameters{
-				PxPerEm: fixed.I(10),
+				PxPerEm:  fixed.I(10),
-			}, 0, 200, tc.locale, tc.text)
+				MaxWidth: 200,
+				Locale:   tc.locale,
+			}, tc.text)
 			doc := cache.txt
 			glyphs := make([]Glyph, 0, len(tc.expected))
 			for g, ok := cache.NextGlyph(); ok; g, ok = cache.NextGlyph() {

widget/index_test.go

@@ -32,17 +32,30 @@ func makePosTestText(fontSize, lineWidth int, alignOpposite bool) (source string
 	// bidiSource is crafted to contain multiple consecutive RTL runs (by
 	// changing scripts within the RTL).
 	bidiSource := "The quick سماء שלום لا fox تمط שלום غير the lazy dog."
-	ltrParams := text.Parameters{Font: text.Font{Typeface: "LTR"}, PxPerEm: fixed.I(fontSize)}
+	ltrParams := text.Parameters{
-	rtlParams := text.Parameters{Alignment: text.End, Font: text.Font{Typeface: "RTL"}, PxPerEm: fixed.I(fontSize)}
+		Font:     text.Font{Typeface: "LTR"},
+		PxPerEm:  fixed.I(fontSize),
+		MaxWidth: lineWidth,
+		MinWidth: lineWidth,
+		Locale:   english,
+	}
+	rtlParams := text.Parameters{
+		Alignment: text.End,
+		Font:      text.Font{Typeface: "RTL"},
+		PxPerEm:   fixed.I(fontSize),
+		MaxWidth:  lineWidth,
+		MinWidth:  lineWidth,
+		Locale:    arabic,
+	}
 	if alignOpposite {
 		ltrParams.Alignment = text.End
 		rtlParams.Alignment = text.Start
 	}
-	shaper.LayoutString(ltrParams, lineWidth, lineWidth, english, bidiSource)
+	shaper.LayoutString(ltrParams, bidiSource)
 	for g, ok := shaper.NextGlyph(); ok; g, ok = shaper.NextGlyph() {
 		bidiLTR = append(bidiLTR, g)
 	}
-	shaper.LayoutString(rtlParams, lineWidth, lineWidth, arabic, bidiSource)
+	shaper.LayoutString(rtlParams, bidiSource)
 	for g, ok := shaper.NextGlyph(); ok; g, ok = shaper.NextGlyph() {
 		bidiRTL = append(bidiRTL, g)
 	}
@@ -64,8 +77,12 @@ func makeAccountingTestText(str string, fontSize, lineWidth int) (txt []text.Gly
 			Face: rtlFace,
 		},
 	})
-	params := text.Parameters{PxPerEm: fixed.I(fontSize)}
+	params := text.Parameters{
-	shaper.LayoutString(params, 0, lineWidth, english, str)
+		PxPerEm:  fixed.I(fontSize),
+		MaxWidth: lineWidth,
+		Locale:   english,
+	}
+	shaper.LayoutString(params, str)
 	for g, ok := shaper.NextGlyph(); ok; g, ok = shaper.NextGlyph() {
 		txt = append(txt, g)
 	}
@@ -86,8 +103,14 @@ func getGlyphs(fontSize, minWidth, lineWidth int, align text.Alignment, str stri
 			Face: rtlFace,
 		},
 	})
-	params := text.Parameters{PxPerEm: fixed.I(fontSize), Alignment: align}
+	params := text.Parameters{
-	shaper.LayoutString(params, minWidth, lineWidth, english, str)
+		PxPerEm:   fixed.I(fontSize),
+		Alignment: align,
+		MinWidth:  minWidth,
+		MaxWidth:  lineWidth,
+		Locale:    english,
+	}
+	shaper.LayoutString(params, str)
 	for g, ok := shaper.NextGlyph(); ok; g, ok = shaper.NextGlyph() {
 		txt = append(txt, g)
 	}

widget/label.go

@@ -38,7 +38,10 @@ func (l Label) Layout(gtx layout.Context, lt *text.Shaper, font text.Font, size
 		MaxLines:  l.MaxLines,
 		Truncator: l.Truncator,
 		Alignment: l.Alignment,
-	}, cs.Min.X, cs.Max.X, gtx.Locale, txt)
+		MaxWidth:  cs.Max.X,
+		MinWidth:  cs.Min.X,
+		Locale:    gtx.Locale,
+	}, txt)
 	m := op.Record(gtx.Ops)
 	viewport := image.Rectangle{Max: cs.Max}
 	it := textIterator{

widget/material/label.go

@@ -116,8 +116,15 @@ func (l LabelStyle) Layout(gtx layout.Context) layout.Dimensions {
 		if l.State.Text() != l.Text {
 			l.State.SetText(l.Text)
 		}
+		l.State.Alignment = l.Alignment
+		l.State.MaxLines = l.MaxLines
+		l.State.Truncator = l.Truncator
 		return l.State.Layout(gtx, l.shaper, l.Font, l.TextSize, textColor, selectColor)
 	}
-	tl := widget.Label{Alignment: l.Alignment, MaxLines: l.MaxLines}
+	tl := widget.Label{
+		Alignment: l.Alignment,
+		MaxLines:  l.MaxLines,
+		Truncator: l.Truncator,
+	}
 	return tl.Layout(gtx, l.shaper, l.Font, l.TextSize, l.Text, textColor)
 }

widget/selectable.go

@@ -48,8 +48,15 @@ func (s stringSource) ReadAt(b []byte, offset int64) (int, error) {
 func (s stringSource) ReplaceRunes(byteOffset, runeCount int64, str string) {
 }
 
-// Selectable holds text selection state.
+// Selectable displays selectable text.
 type Selectable struct {
+	// Alignment controls the alignment of the text.
+	Alignment text.Alignment
+	// MaxLines is the maximum number of lines of text to be displayed.
+	MaxLines int
+	// Truncator is the symbol to use at the end of the final line of text
+	// if text was cut off. Defaults to "…" if left empty.
+	Truncator   string
 	initialized bool
 	source      stringSource
 	// scratch is a buffer reused to efficiently read text out of the
@@ -171,6 +178,9 @@ func (l *Selectable) Truncated() bool {
 // paint material for the text and selection rectangles, respectively.
 func (l *Selectable) Layout(gtx layout.Context, lt *text.Shaper, font text.Font, size unit.Sp, textMaterial, selectionMaterial op.CallOp) layout.Dimensions {
 	l.initialize()
+	l.text.Alignment = l.Alignment
+	l.text.MaxLines = l.MaxLines
+	l.text.Truncator = l.Truncator
 	l.text.Update(gtx, lt, font, size, l.handleEvents)
 	dims := l.text.Dimensions()
 	defer clip.Rect(image.Rectangle{Max: dims.Size}).Push(gtx.Ops).Pop()

widget/selectable_test.go

@@ -100,7 +100,7 @@ func TestSelectableConfigurations(t *testing.T) {
 					gtx.Constraints.Min = gtx.Constraints.Max
 				}
 				s := new(Selectable)
-				s.text.Alignment = alignment
+				s.Alignment = alignment
 				s.SetText(sentence)
 				interactiveDims := s.Layout(gtx, cache, font, fontSize, op.CallOp{}, op.CallOp{})
 				staticDims := Label{Alignment: alignment}.Layout(gtx, cache, font, fontSize, sentence, op.CallOp{})

widget/text.go

@@ -10,7 +10,6 @@ import (
 	"unicode/utf8"
 
 	"gioui.org/f32"
-	"gioui.org/io/system"
 	"gioui.org/layout"
 	"gioui.org/op"
 	"gioui.org/op/clip"
@@ -58,22 +57,20 @@ type textView struct {
 	// are accessed by Len, Text, and SetText.
 	Mask rune
 
-	font       text.Font
+	params     text.Parameters
 	shaper     *text.Shaper
-	textSize   fixed.Int26_6
 	seekCursor int64
 	rr         textSource
 	maskReader maskReader
 	// graphemes tracks the indices of grapheme cluster boundaries within rr.
 	graphemes []int
 	// paragraphReader is used to populate graphemes.
-	paragraphReader    graphemeReader
+	paragraphReader graphemeReader
-	lastMask           rune
+	lastMask        rune
-	maxWidth, minWidth int
+	viewSize        image.Point
-	viewSize           image.Point
+	valid           bool
-	valid              bool
+	regions         []Region
-	regions            []Region
+	dims            layout.Dimensions
-	dims               layout.Dimensions
 
 	// offIndex is an index of rune index to byte offsets.
 	offIndex []offEntry
@@ -93,8 +90,6 @@ type textView struct {
 	}
 
 	scrollOff image.Point
-
-	locale system.Locale
 }
 
 func (e *textView) Changed() bool {
@@ -228,27 +223,27 @@ func (e *textView) calculateViewSize(gtx layout.Context) image.Point {
 // allow parent widgets to adapt to any changes in text content or positioning. If eventHandling modifies the contents
 // of the textView, it is guaranteed to be reshaped (and ready for painting) before Update returns.
 func (e *textView) Update(gtx layout.Context, lt *text.Shaper, font text.Font, size unit.Sp, eventHandling func(gtx layout.Context)) {
-	if e.locale != gtx.Locale {
+	if e.params.Locale != gtx.Locale {
-		e.locale = gtx.Locale
+		e.params.Locale = gtx.Locale
 		e.invalidate()
 	}
 	textSize := fixed.I(gtx.Sp(size))
-	if e.font != font || e.textSize != textSize {
+	if e.params.Font != font || e.params.PxPerEm != textSize {
 		e.invalidate()
-		e.font = font
+		e.params.Font = font
-		e.textSize = textSize
+		e.params.PxPerEm = textSize
 	}
 	maxWidth := gtx.Constraints.Max.X
 	if e.SingleLine {
 		maxWidth = math.MaxInt
 	}
 	minWidth := gtx.Constraints.Min.X
-	if maxWidth != e.maxWidth {
+	if maxWidth != e.params.MaxWidth {
-		e.maxWidth = maxWidth
+		e.params.MaxWidth = maxWidth
 		e.invalidate()
 	}
-	if minWidth != e.minWidth {
+	if minWidth != e.params.MinWidth {
-		e.minWidth = minWidth
+		e.params.MinWidth = minWidth
 		e.invalidate()
 	}
 	if lt != e.shaper {
@@ -259,6 +254,18 @@ func (e *textView) Update(gtx layout.Context, lt *text.Shaper, font text.Font, s
 		e.lastMask = e.Mask
 		e.invalidate()
 	}
+	if e.Alignment != e.params.Alignment {
+		e.params.Alignment = e.Alignment
+		e.invalidate()
+	}
+	if e.Truncator != e.params.Truncator {
+		e.params.Truncator = e.Truncator
+		e.invalidate()
+	}
+	if e.MaxLines != e.params.MaxLines {
+		e.params.MaxLines = e.MaxLines
+		e.invalidate()
+	}
 
 	e.makeValid()
 	if eventHandling != nil {
@@ -463,13 +470,7 @@ func (e *textView) layoutText(lt *text.Shaper) {
 	e.index.reset()
 	it := textIterator{viewport: image.Rectangle{Max: image.Point{X: math.MaxInt, Y: math.MaxInt}}}
 	if lt != nil {
-		lt.Layout(text.Parameters{
+		lt.Layout(e.params, r)
-			Font:      e.font,
-			PxPerEm:   e.textSize,
-			Alignment: e.Alignment,
-			MaxLines:  e.MaxLines,
-			Truncator: e.Truncator,
-		}, e.minWidth, e.maxWidth, e.locale, r)
 		for glyph, ok := it.processGlyph(lt.NextGlyph()); ok; glyph, ok = it.processGlyph(lt.NextGlyph()) {
 			e.index.Glyph(glyph)
 		}
@@ -635,7 +636,7 @@ func (e *textView) MoveEnd(selAct selectionAction) {
 	caret := e.closestToRune(e.caret.start)
 	caret = e.closestToLineCol(caret.lineCol.line, math.MaxInt)
 	e.caret.start = caret.runes
-	e.caret.xoff = fixed.I(e.maxWidth) - caret.x
+	e.caret.xoff = fixed.I(e.params.MaxWidth) - caret.x
 	e.updateSelection(selAct)
 	e.clampCursorToGraphemes()
 }