io/input: [API] introduce Source, the interface between a Router and widgets

This change gets rid of the event.Queue interface by replacing it with
input.Source values. Source provides the interface to Router necessary
to implement interface widgets.

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

widget/material/button.go

@@ -133,7 +133,7 @@ func (b ButtonLayoutStyle) Layout(gtx layout.Context, w layout.Widget) layout.Di
 				defer clip.UniformRRect(image.Rectangle{Max: gtx.Constraints.Min}, rr).Push(gtx.Ops).Pop()
 				background := b.Background
 				switch {
-				case gtx.Source == nil:
+				case !gtx.Enabled():
 					background = f32color.Disabled(b.Background)
 				case b.Button.Hovered() || b.Button.Focused():
 					background = f32color.Hovered(b.Background)
@@ -165,7 +165,7 @@ func (b IconButtonStyle) Layout(gtx layout.Context) layout.Dimensions {
 				defer clip.UniformRRect(image.Rectangle{Max: gtx.Constraints.Min}, rr).Push(gtx.Ops).Pop()
 				background := b.Background
 				switch {
-				case gtx.Source == nil:
+				case !gtx.Enabled():
 					background = f32color.Disabled(b.Background)
 				case b.Button.Hovered() || b.Button.Focused():
 					background = f32color.Hovered(b.Background)

widget/material/checkable.go

@@ -60,7 +60,7 @@ func (c *checkable) layout(gtx layout.Context, checked, hovered bool) layout.Dim
 					return layout.UniformInset(2).Layout(gtx, func(gtx layout.Context) layout.Dimensions {
 						size := gtx.Dp(c.Size)
 						col := c.IconColor
-						if gtx.Source == nil {
+						if !gtx.Enabled() {
 							col = f32color.Disabled(col)
 						}
 						gtx.Constraints.Min = image.Point{X: size}

widget/material/editor.go

@@ -61,7 +61,7 @@ func (e EditorStyle) Layout(gtx layout.Context) layout.Dimensions {
 	paint.ColorOp{Color: e.HintColor}.Add(gtx.Ops)
 	hintColor := hintColorMacro.Stop()
 	selectionColorMacro := op.Record(gtx.Ops)
-	paint.ColorOp{Color: blendDisabledColor(gtx.Source == nil, e.SelectionColor)}.Add(gtx.Ops)
+	paint.ColorOp{Color: blendDisabledColor(!gtx.Enabled(), e.SelectionColor)}.Add(gtx.Ops)
 	selectionColor := selectionColorMacro.Stop()
 
 	var maxlines int

widget/material/progressbar.go

@@ -51,7 +51,7 @@ func (p ProgressBarStyle) Layout(gtx layout.Context) layout.Dimensions {
 		layout.Stacked(func(gtx layout.Context) layout.Dimensions {
 			fillWidth := int(float32(progressBarWidth) * clamp1(p.Progress))
 			fillColor := p.Color
-			if gtx.Source == nil {
+			if !gtx.Enabled() {
 				fillColor = f32color.Disabled(fillColor)
 			}
 			return shader(fillWidth, fillColor)

widget/material/slider.go

@@ -56,7 +56,7 @@ func (s SliderStyle) Layout(gtx layout.Context) layout.Dimensions {
 	trans.Pop()
 
 	color := s.Color
-	if gtx.Source == nil {
+	if !gtx.Enabled() {
 		color = f32color.Disabled(color)
 	}
 

widget/material/switch.go

@@ -55,7 +55,7 @@ func (s SwitchStyle) Layout(gtx layout.Context) layout.Dimensions {
 	if s.Switch.Value {
 		col = s.Color.Enabled
 	}
-	if gtx.Source == nil {
+	if !gtx.Enabled() {
 		col = f32color.Disabled(col)
 	}
 	trackColor := s.Color.Track