widget: add semantic descriptions

Some semantic information is automatically extracted, but some must be
provided by UI components. This change enriches the generic and material
widgets with such information.

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

widget/material/button.go

@@ -9,6 +9,7 @@ import (
 
 	"gioui.org/f32"
 	"gioui.org/internal/f32color"
+	"gioui.org/io/semantic"
 	"gioui.org/layout"
 	"gioui.org/op"
 	"gioui.org/op/clip"
@@ -89,6 +90,7 @@ func IconButton(th *Theme, button *widget.Clickable, icon *widget.Icon, descript
 // decoration.
 func Clickable(gtx layout.Context, button *widget.Clickable, w layout.Widget) layout.Dimensions {
 	return button.Layout(gtx, func(gtx layout.Context) layout.Dimensions {
+		semantic.Button.Add(gtx.Ops)
 		return layout.Stack{}.Layout(gtx,
 			layout.Expanded(func(gtx layout.Context) layout.Dimensions {
 				defer clip.Rect{Max: gtx.Constraints.Min}.Push(gtx.Ops).Pop()
@@ -118,6 +120,7 @@ func (b ButtonStyle) Layout(gtx layout.Context) layout.Dimensions {
 func (b ButtonLayoutStyle) Layout(gtx layout.Context, w layout.Widget) layout.Dimensions {
 	min := gtx.Constraints.Min
 	return b.Button.Layout(gtx, func(gtx layout.Context) layout.Dimensions {
+		semantic.Button.Add(gtx.Ops)
 		return layout.Stack{Alignment: layout.Center}.Layout(gtx,
 			layout.Expanded(func(gtx layout.Context) layout.Dimensions {
 				rr := float32(gtx.Px(b.CornerRadius))
@@ -149,6 +152,10 @@ func (b ButtonLayoutStyle) Layout(gtx layout.Context, w layout.Widget) layout.Di
 func (b IconButtonStyle) Layout(gtx layout.Context) layout.Dimensions {
 	m := op.Record(gtx.Ops)
 	dims := b.Button.Layout(gtx, func(gtx layout.Context) layout.Dimensions {
+		semantic.Button.Add(gtx.Ops)
+		if d := b.Description; d != "" {
+			semantic.DescriptionOp(b.Description).Add(gtx.Ops)
+		}
 		return layout.Stack{Alignment: layout.Center}.Layout(gtx,
 			layout.Expanded(func(gtx layout.Context) layout.Dimensions {
 				sizex, sizey := gtx.Constraints.Min.X, gtx.Constraints.Min.Y

widget/material/checkbox.go

@@ -3,6 +3,7 @@
 package material
 
 import (
+	"gioui.org/io/semantic"
 	"gioui.org/layout"
 	"gioui.org/unit"
 	"gioui.org/widget"
@@ -32,6 +33,7 @@ func CheckBox(th *Theme, checkBox *widget.Bool, label string) CheckBoxStyle {
 // Layout updates the checkBox and displays it.
 func (c CheckBoxStyle) Layout(gtx layout.Context) layout.Dimensions {
 	return c.CheckBox.Layout(gtx, func(gtx layout.Context) layout.Dimensions {
+		semantic.CheckBox.Add(gtx.Ops)
 		return c.layout(gtx, c.CheckBox.Value, c.CheckBox.Hovered())
 	})
 }

widget/material/editor.go

@@ -6,6 +6,7 @@ import (
 	"image/color"
 
 	"gioui.org/internal/f32color"
+	"gioui.org/io/semantic"
 	"gioui.org/layout"
 	"gioui.org/op"
 	"gioui.org/op/paint"
@@ -59,6 +60,7 @@ func (e EditorStyle) Layout(gtx layout.Context) layout.Dimensions {
 		gtx.Constraints.Min.Y = h
 	}
 	dims = e.Editor.Layout(gtx, e.shaper, e.Font, e.TextSize, func(gtx layout.Context) layout.Dimensions {
+		semantic.Editor.Add(gtx.Ops)
 		disabled := gtx.Queue == nil
 		if e.Editor.Len() > 0 {
 			paint.ColorOp{Color: blendDisabledColor(disabled, e.SelectionColor)}.Add(gtx.Ops)

widget/material/radiobutton.go

@@ -3,6 +3,7 @@
 package material
 
 import (
+	"gioui.org/io/semantic"
 	"gioui.org/layout"
 	"gioui.org/unit"
 	"gioui.org/widget"
@@ -38,6 +39,7 @@ func RadioButton(th *Theme, group *widget.Enum, key, label string) RadioButtonSt
 func (r RadioButtonStyle) Layout(gtx layout.Context) layout.Dimensions {
 	hovered, hovering := r.Group.Hovered()
 	return r.Group.Layout(gtx, r.Key, func(gtx layout.Context) layout.Dimensions {
+		semantic.RadioButton.Add(gtx.Ops)
 		return r.layout(gtx, r.Group.Value == r.Key, hovering && hovered == r.Key)
 	})
 }

widget/material/switch.go

@@ -8,6 +8,7 @@ import (
 
 	"gioui.org/f32"
 	"gioui.org/internal/f32color"
+	"gioui.org/io/semantic"
 	"gioui.org/layout"
 	"gioui.org/op"
 	"gioui.org/op/clip"
@@ -127,6 +128,10 @@ func (s SwitchStyle) Layout(gtx layout.Context) layout.Dimensions {
 	sz := image.Pt(clickSize, clickSize)
 	defer clip.Ellipse(f32.Rectangle{Max: layout.FPt(sz)}).Push(gtx.Ops).Pop()
 	s.Switch.Layout(gtx, func(gtx layout.Context) layout.Dimensions {
+		if d := s.Description; d != "" {
+			semantic.DescriptionOp(d).Add(gtx.Ops)
+		}
+		semantic.Switch.Add(gtx.Ops)
 		return layout.Dimensions{Size: sz}
 	})