widget: update text indexing expectations

The typesetting package has smarter line wrapping now, which is making our
test text require fewer lines to display. We needed to update the expected
data accordingly.

I've also added a feature that takes a screenshot of the rendered output of
one of our most complex cursoring tests. This will make it much easier to
verify its behavior in the future. This feature currently only triggers if
the test case fails.

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

widget/index_test.go

@@ -2,12 +2,18 @@ package widget
 
 import (
 	"bytes"
+	"image"
+	"image/png"
 	"io"
+	"os"
 	"testing"
 
 	nsareg "eliasnaur.com/font/noto/sans/arabic/regular"
 	"gioui.org/font"
 	"gioui.org/font/opentype"
+	"gioui.org/gpu/headless"
+	"gioui.org/layout"
+	"gioui.org/op"
 	"gioui.org/text"
 	"golang.org/x/image/font/gofont/goregular"
 	"golang.org/x/image/math/fixed"
@@ -16,11 +22,11 @@ import (
 // makePosTestText returns two bidi samples of shaped text at the given
 // font size and wrapped to the given line width. The runeLimit, if nonzero,
 // truncates the sample text to ensure shorter output for expensive tests.
-func makePosTestText(fontSize, lineWidth int, alignOpposite bool) (source string, bidiLTR, bidiRTL []text.Glyph) {
+func makePosTestText(fontSize, lineWidth int, alignOpposite bool) (shaper *text.Shaper, source string, bidiLTR, bidiRTL []text.Glyph) {
 	ltrFace, _ := opentype.Parse(goregular.TTF)
 	rtlFace, _ := opentype.Parse(nsareg.TTF)
 
-	shaper := text.NewShaper(text.NoSystemFonts(), text.WithCollection([]font.FontFace{
+	shaper = text.NewShaper(text.NoSystemFonts(), text.WithCollection([]font.FontFace{
 		{
 			Font: font.Font{Typeface: "LTR"},
 			Face: ltrFace,
@@ -58,7 +64,7 @@ func makePosTestText(fontSize, lineWidth int, alignOpposite bool) (source string
 	for g, ok := shaper.NextGlyph(); ok; g, ok = shaper.NextGlyph() {
 		bidiRTL = append(bidiRTL, g)
 	}
-	return bidiSource, bidiLTR, bidiRTL
+	return shaper, bidiSource, bidiLTR, bidiRTL
 }
 
 // makeAccountingTestText shapes text designed to stress rune accounting
@@ -260,7 +266,7 @@ func TestIndexPositionWhitespace(t *testing.T) {
 func TestIndexPositionBidi(t *testing.T) {
 	fontSize := 16
 	lineWidth := fontSize * 10
-	_, bidiLTRText, bidiRTLText := makePosTestText(fontSize, lineWidth, false)
+	shaper, _, bidiLTRText, bidiRTLText := makePosTestText(fontSize, lineWidth, false)
 	type testcase struct {
 		name       string
 		glyphs     []text.Glyph
@@ -284,13 +290,12 @@ func TestIndexPositionBidi(t *testing.T) {
 			name:   "bidi rtl",
 			glyphs: bidiRTLText,
 			expectedXs: []fixed.Int26_6{
-				2646, 3272, 3842, 4412, 4697, 5267, 5837, 6090, 6602, 7114, 2646, 2380, 1577, 985, 687, 266, // Positions on line 0.
+				// Line 0
-
+				5718, 6344, 6914, 7484, 7769, 8339, 8909, 9162, 9674, 10186, 5718, 5452, 4649, 4057, 3759, 3338, 3072, 2304, 1536, 768, 0,
-				7867, 7099, 6331, 5563, 4795, 4510, 4212, 3914, 3648, 2281, 2566, 3136, 3648, 2281, 2015, 1709, 1117, 266, // Positions on line 1.
+				// Line 1
-
+				9170, 8872, 8574, 8308, 6941, 7226, 7796, 8308, 6941, 6675, 6369, 5777, 4926, 4660, 3892, 3124, 2356, 1588, 1303, 788, 406, 0,
-				8794, 8026, 7258, 6490, 5722, 5437, 4922, 4540, 4134, 3868, 0, 290, 860, 1430, 1715, 1989, 2559, 3071, 3583, // Positions on line 2.
+				// Line 2
-
+				324, 614, 1184, 1754, 2039, 2313, 2883, 3395, 3907, 4192, 4762, 5332, 5902, 324, 0,
-				324, 894, 1464, 2034, 324, 0, // Positions on line 3.
 			},
 		},
 	} {
@@ -337,6 +342,35 @@ func TestIndexPositionBidi(t *testing.T) {
 			printPositions(t, gi.positions)
 			if t.Failed() {
 				printGlyphs(t, tc.glyphs)
+				width := lineWidth
+				height := 100
+				cap := image.NewRGBA(image.Rect(0, 0, width, height))
+				w, _ := headless.NewWindow(width, height)
+				defer w.Release()
+				ops := new(op.Ops)
+				gtx := layout.Context{
+					Constraints: layout.Constraints{Max: image.Pt(width, height)},
+					Ops:         ops,
+				}
+				it := textIterator{viewport: image.Rectangle{Max: image.Point{X: width, Y: height}}}
+				for _, g := range tc.glyphs {
+					it.processGlyph(g, true)
+				}
+				var glyphs [32]text.Glyph
+				line := glyphs[:0]
+				for _, g := range gi.glyphs {
+					var ok bool
+					if line, ok = it.paintGlyph(gtx, shaper, g, line); !ok {
+						break
+					}
+				}
+				w.Frame(ops)
+				w.Screenshot(cap)
+				b := new(bytes.Buffer)
+				_ = png.Encode(b, cap)
+				screenshotName := tc.name + ".png"
+				_ = os.WriteFile(screenshotName, b.Bytes(), 0o644)
+				t.Logf("wrote %q", screenshotName)
 			}
 		})
 	}
@@ -345,8 +379,8 @@ func TestIndexPositionBidi(t *testing.T) {
 func TestIndexPositionLines(t *testing.T) {
 	fontSize := 16
 	lineWidth := fontSize * 10
-	source1, bidiLTRText, bidiRTLText := makePosTestText(fontSize, lineWidth, false)
+	_, source1, bidiLTRText, bidiRTLText := makePosTestText(fontSize, lineWidth, false)
-	source2, bidiLTRTextOpp, bidiRTLTextOpp := makePosTestText(fontSize, lineWidth, true)
+	_, source2, bidiLTRTextOpp, bidiRTLTextOpp := makePosTestText(fontSize, lineWidth, true)
 	type testcase struct {
 		name          string
 		source        string
@@ -379,7 +413,7 @@ func TestIndexPositionLines(t *testing.T) {
 					xOff:    fixed.Int26_6(0),
 					yOff:    60,
 					glyphs:  18,
-					width:   fixed.Int26_6(8813),
+					width:   fixed.Int26_6(8528),
 					ascent:  fixed.Int26_6(1407),
 					descent: fixed.Int26_6(756),
 				},
@@ -401,32 +435,24 @@ func TestIndexPositionLines(t *testing.T) {
 				{
 					xOff:    fixed.Int26_6(0),
 					yOff:    22,
-					glyphs:  15,
+					glyphs:  20,
-					width:   fixed.Int26_6(7114),
+					width:   fixed.Int26_6(10186),
 					ascent:  fixed.Int26_6(1407),
 					descent: fixed.Int26_6(756),
 				},
 				{
 					xOff:    fixed.Int26_6(0),
 					yOff:    41,
-					glyphs:  15,
+					glyphs:  19,
-					width:   fixed.Int26_6(7867),
+					width:   fixed.Int26_6(9170),
 					ascent:  fixed.Int26_6(1407),
 					descent: fixed.Int26_6(756),
 				},
 				{
 					xOff:    fixed.Int26_6(0),
 					yOff:    60,
-					glyphs:  18,
+					glyphs:  13,
-					width:   fixed.Int26_6(8794),
+					width:   fixed.Int26_6(5902),
-					ascent:  fixed.Int26_6(1407),
-					descent: fixed.Int26_6(756),
-				},
-				{
-					xOff:    fixed.Int26_6(0),
-					yOff:    79,
-					glyphs:  4,
-					width:   fixed.Int26_6(2034),
 					ascent:  fixed.Int26_6(968),
 					descent: fixed.Int26_6(216),
 				},
@@ -454,10 +480,10 @@ func TestIndexPositionLines(t *testing.T) {
 					descent: fixed.Int26_6(756),
 				},
 				{
-					xOff:    fixed.Int26_6(1427),
+					xOff:    fixed.Int26_6(1712),
 					yOff:    60,
 					glyphs:  18,
-					width:   fixed.Int26_6(8813),
+					width:   fixed.Int26_6(8528),
 					ascent:  fixed.Int26_6(1407),
 					descent: fixed.Int26_6(756),
 				},
@@ -477,34 +503,26 @@ func TestIndexPositionLines(t *testing.T) {
 			glyphs: bidiRTLTextOpp,
 			expectedLines: []lineInfo{
 				{
-					xOff:    fixed.Int26_6(3126),
+					xOff:    fixed.Int26_6(54),
 					yOff:    22,
-					glyphs:  15,
+					glyphs:  20,
-					width:   fixed.Int26_6(7114),
+					width:   fixed.Int26_6(10186),
 					ascent:  fixed.Int26_6(1407),
 					descent: fixed.Int26_6(756),
 				},
 				{
-					xOff:    fixed.Int26_6(2373),
+					xOff:    fixed.Int26_6(1070),
 					yOff:    41,
-					glyphs:  15,
+					glyphs:  19,
-					width:   fixed.Int26_6(7867),
+					width:   fixed.Int26_6(9170),
 					ascent:  fixed.Int26_6(1407),
 					descent: fixed.Int26_6(756),
 				},
 				{
-					xOff:    fixed.Int26_6(1446),
+					xOff:    fixed.Int26_6(4338),
 					yOff:    60,
-					glyphs:  18,
+					glyphs:  13,
-					width:   fixed.Int26_6(8794),
+					width:   fixed.Int26_6(5902),
-					ascent:  fixed.Int26_6(1407),
-					descent: fixed.Int26_6(756),
-				},
-				{
-					xOff:    fixed.Int26_6(8206),
-					yOff:    79,
-					glyphs:  4,
-					width:   fixed.Int26_6(2034),
 					ascent:  fixed.Int26_6(968),
 					descent: fixed.Int26_6(216),
 				},