go.*,text,widget{,/material}: enable configurable line wrapping within words

This commit enables consumers of the text shaper to select a policy for how
line breaking candidates will be chosen. The new default policy can break lines
within "words" (UAX#14 segments) when words do not fit by themselves on a line.
This ensures that text does not horizontally overflow its bounding box unless
the available width is insufficient to display a single UAX#29 grapheme cluster.

Fixes: https://todo.sr.ht/~eliasnaur/gio/467
Signed-off-by: Chris Waldon <christopher.waldon.dev@gmail.com>

widget/editor.go

@@ -57,6 +57,8 @@ type Editor struct {
 	// Filter is the list of characters allowed in the Editor. If Filter is empty,
 	// all characters are allowed.
 	Filter string
+	// WrapPolicy configures how displayed text will be broken into lines.
+	WrapPolicy text.WrapPolicy
 
 	buffer *editBuffer
 	// scratch is a byte buffer that is reused to efficiently read portions of text
@@ -504,6 +506,7 @@ func (e *Editor) initBuffer() {
 	e.text.Alignment = e.Alignment
 	e.text.SingleLine = e.SingleLine
 	e.text.Mask = e.Mask
+	e.text.WrapPolicy = e.WrapPolicy
 }
 
 // Layout lays out the editor using the provided textMaterial as the paint material

widget/editor_test.go

@@ -409,6 +409,7 @@ func TestEditorRTL(t *testing.T) {
 
 func TestEditorLigature(t *testing.T) {
 	e := new(Editor)
+	e.WrapPolicy = text.WrapWords
 	gtx := layout.Context{
 		Ops:         new(op.Ops),
 		Constraints: layout.Exact(image.Pt(100, 100)),

widget/label.go

@@ -28,6 +28,8 @@ type Label struct {
 	// Truncator is the text that will be shown at the end of the final
 	// line if MaxLines is exceeded. Defaults to "…" if empty.
 	Truncator string
+	// WrapPolicy configures how displayed text will be broken into lines.
+	WrapPolicy text.WrapPolicy
 }
 
 // Layout the label with the given shaper, font, size, text, and material.
@@ -35,14 +37,15 @@ func (l Label) Layout(gtx layout.Context, lt *text.Shaper, font font.Font, size
 	cs := gtx.Constraints
 	textSize := fixed.I(gtx.Sp(size))
 	lt.LayoutString(text.Parameters{
-		Font:      font,
-		PxPerEm:   textSize,
-		MaxLines:  l.MaxLines,
-		Truncator: l.Truncator,
-		Alignment: l.Alignment,
-		MaxWidth:  cs.Max.X,
-		MinWidth:  cs.Min.X,
-		Locale:    gtx.Locale,
+		Font:       font,
+		PxPerEm:    textSize,
+		MaxLines:   l.MaxLines,
+		Truncator:  l.Truncator,
+		Alignment:  l.Alignment,
+		WrapPolicy: l.WrapPolicy,
+		MaxWidth:   cs.Max.X,
+		MinWidth:   cs.Min.X,
+		Locale:     gtx.Locale,
 	}, txt)
 	m := op.Record(gtx.Ops)
 	viewport := image.Rectangle{Max: cs.Max}

widget/material/label.go

@@ -29,6 +29,8 @@ type LabelStyle struct {
 	Alignment text.Alignment
 	// MaxLines limits the number of lines. Zero means no limit.
 	MaxLines int
+	// WrapPolicy configures how displayed text will be broken into lines.
+	WrapPolicy text.WrapPolicy
 	// Truncator is the text that will be shown at the end of the final
 	// line if MaxLines is exceeded. Defaults to "…" if empty.
 	Truncator string
@@ -127,12 +129,14 @@ func (l LabelStyle) Layout(gtx layout.Context) layout.Dimensions {
 		l.State.Alignment = l.Alignment
 		l.State.MaxLines = l.MaxLines
 		l.State.Truncator = l.Truncator
+		l.State.WrapPolicy = l.WrapPolicy
 		return l.State.Layout(gtx, l.Shaper, l.Font, l.TextSize, textColor, selectColor)
 	}
 	tl := widget.Label{
-		Alignment: l.Alignment,
-		MaxLines:  l.MaxLines,
-		Truncator: l.Truncator,
+		Alignment:  l.Alignment,
+		MaxLines:   l.MaxLines,
+		Truncator:  l.Truncator,
+		WrapPolicy: l.WrapPolicy,
 	}
 	return tl.Layout(gtx, l.Shaper, l.Font, l.TextSize, l.Text, textColor)
 }

widget/selectable.go

@@ -57,7 +57,9 @@ type Selectable struct {
 	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
+	Truncator string
+	// WrapPolicy configures how displayed text will be broken into lines.
+	WrapPolicy  text.WrapPolicy
 	initialized bool
 	source      stringSource
 	// scratch is a buffer reused to efficiently read text out of the
@@ -182,6 +184,7 @@ func (l *Selectable) Layout(gtx layout.Context, lt *text.Shaper, font font.Font,
 	l.text.Alignment = l.Alignment
 	l.text.MaxLines = l.MaxLines
 	l.text.Truncator = l.Truncator
+	l.text.WrapPolicy = l.WrapPolicy
 	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/text.go

@@ -53,6 +53,8 @@ type textView struct {
 	// Truncator is the text that will be shown at the end of the final
 	// line if MaxLines is exceeded. Defaults to "…" if empty.
 	Truncator string
+	// WrapPolicy configures how displayed text will be broken into lines.
+	WrapPolicy text.WrapPolicy
 	// Mask replaces the visual display of each rune in the contents with the given rune.
 	// Newline characters are not masked. When non-zero, the unmasked contents
 	// are accessed by Len, Text, and SetText.
@@ -267,6 +269,10 @@ func (e *textView) Update(gtx layout.Context, lt *text.Shaper, font font.Font, s
 		e.params.MaxLines = e.MaxLines
 		e.invalidate()
 	}
+	if e.WrapPolicy != e.params.WrapPolicy {
+		e.params.WrapPolicy = e.WrapPolicy
+		e.invalidate()
+	}
 
 	e.makeValid()
 	if eventHandling != nil {