widget/material: add disabled state support to all widgets

This commit configures all remaining widgets to draw themselves in a disabled state
when their layout.Context is disabled. A description of the
strategy employed by each follows:

- Checkbox and RadioButton: Draws the icon component in a lighter color. Currently the label text is left
in its default color.
- ProgressBar: The "progress" color is lightened, but not as much as the background color. This makes the current progress value still readable.
- Editor: The cursor is no longer drawn and the text is lightened.
- Switch: The track is unchanged, but the circular "thumb" component is lightened.

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

widget/material/checkable.go

@@ -41,6 +41,9 @@ func (c *checkable) layout(gtx layout.Context, checked bool) layout.Dimensions {
 				return layout.UniformInset(unit.Dp(2)).Layout(gtx, func(gtx layout.Context) layout.Dimensions {
 					size := gtx.Px(c.Size)
 					icon.Color = c.IconColor
+					if gtx.Queue == nil {
+						icon.Color = mulAlpha(icon.Color, 150)
+					}
 					icon.Layout(gtx, unit.Px(float32(size)))
 					return layout.Dimensions{
 						Size: image.Point{X: size, Y: size},

widget/material/editor.go

@@ -52,13 +52,20 @@ 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)
+	disabled := gtx.Queue == nil
 	if e.Editor.Len() > 0 {
-		paint.ColorOp{Color: e.Color}.Add(gtx.Ops)
+		textColor := e.Color
+		if disabled {
+			textColor = mulAlpha(textColor, 150)
+		}
+		paint.ColorOp{Color: textColor}.Add(gtx.Ops)
 		e.Editor.PaintText(gtx)
 	} else {
 		call.Add(gtx.Ops)
 	}
-	paint.ColorOp{Color: e.Color}.Add(gtx.Ops)
-	e.Editor.PaintCaret(gtx)
+	if !disabled {
+		paint.ColorOp{Color: e.Color}.Add(gtx.Ops)
+		e.Editor.PaintCaret(gtx)
+	}
 	return dims
 }

widget/material/progressbar.go

@@ -64,7 +64,11 @@ func (p ProgressBarStyle) Layout(gtx layout.Context) layout.Dimensions {
 		}),
 		layout.Stacked(func(gtx layout.Context) layout.Dimensions {
 			fillWidth := (progressBarWidth / 100) * float32(progress)
-			return shader(fillWidth, p.Color)
+			fillColor := p.Color
+			if gtx.Queue == nil {
+				fillColor = mulAlpha(fillColor, 200)
+			}
+			return shader(fillWidth, fillColor)
 		}),
 	)
 }

widget/material/switch.go

@@ -47,12 +47,20 @@ func (s SwitchStyle) Layout(gtx layout.Context) layout.Dimensions {
 		X: float32(trackWidth),
 		Y: float32(trackHeight),
 	}}
+	col := s.Color.Disabled
+	if s.Switch.Value {
+		col = s.Color.Enabled
+	}
+	if gtx.Queue == nil {
+		col = mulAlpha(col, 150)
+	}
+	trackColor := mulAlpha(col, 150)
 	op.TransformOp{}.Offset(f32.Point{Y: trackOff}).Add(gtx.Ops)
 	clip.Rect{
 		Rect: trackRect,
 		NE:   trackCorner, NW: trackCorner, SE: trackCorner, SW: trackCorner,
 	}.Op(gtx.Ops).Add(gtx.Ops)
-	paint.ColorOp{Color: rgb(0x9b9b9b)}.Add(gtx.Ops)
+	paint.ColorOp{Color: trackColor}.Add(gtx.Ops)
 	paint.PaintOp{Rect: trackRect}.Add(gtx.Ops)
 	stack.Pop()
 
@@ -79,11 +87,9 @@ func (s SwitchStyle) Layout(gtx layout.Context) layout.Dimensions {
 
 	// Compute thumb offset and color.
 	stack = op.Push(gtx.Ops)
-	col := s.Color.Disabled
 	if s.Switch.Value {
 		off := trackWidth - thumbSize
 		op.TransformOp{}.Offset(f32.Point{X: float32(off)}).Add(gtx.Ops)
-		col = s.Color.Enabled
 	}
 
 	// Draw thumb shadow, a translucent disc slightly larger than the