widget,widget/material: remove disabled drawing modes

Determining the enabled state of a widget from whether its Clicked method has
been called only works for button-like widgets. For example, it's not clear a
Clicked method is appropriate for a CheckBox.

Remove the feature for now, and let's find a better design in the future.

As a nice side effect, we can now process events in Layout methods, so that
buttons react to user input even when Clicked is not called.

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

example/kitchen/kitchen.go

@@ -62,13 +62,13 @@ var (
 		SingleLine: true,
 		Submit:     true,
 	}
-	button         = new(widget.Button)
-	disabledButton = new(widget.Button)
-	iconButton     = new(widget.Button)
-	list           = &layout.List{
+	button      = new(widget.Button)
+	greenButton = new(widget.Button)
+	iconButton  = new(widget.Button)
+	list        = &layout.List{
 		Axis: layout.Vertical,
 	}
-	enabled  bool
+	green    = true
 	topLabel = "Hello, Gio"
 	icon     *material.Icon
 )
@@ -98,15 +98,13 @@ func kitchen(gtx *layout.Context, th *material.Theme) {
 			in := layout.UniformInset(unit.Dp(8))
 			b1 := buttons.Rigid(gtx, func() {
 				in.Layout(gtx, func() {
-					for iconButton.Clicked(gtx) {
-					}
 					th.IconButton(icon).Layout(gtx, iconButton)
 				})
 			})
 			b2 := buttons.Rigid(gtx, func() {
 				in.Layout(gtx, func() {
 					for button.Clicked(gtx) {
-						enabled = !enabled
+						green = !green
 					}
 					th.Button("Click me!").Layout(gtx, button)
 				})
@@ -114,15 +112,11 @@ func kitchen(gtx *layout.Context, th *material.Theme) {
 			b3 := buttons.Rigid(gtx, func() {
 				in.Layout(gtx, func() {
 					var btn material.Button
-					if enabled {
-						for disabledButton.Clicked(gtx) {
-						}
-						btn = th.Button("Enabled")
-					} else {
-						btn = th.Button("Disabled")
+					btn = th.Button("Green button")
+					if green {
+						btn.Background = color.RGBA{A: 0xff, R: 0x9e, G: 0x9d, B: 0x24}
 					}
-					btn.Background = color.RGBA{A: 0xff, R: 0x9e, G: 0x9d, B: 0x24}
-					btn.Layout(gtx, disabledButton)
+					btn.Layout(gtx, greenButton)
 				})
 			})
 			buttons.Layout(gtx, b1, b2, b3)

widget/button.go

@@ -12,9 +12,13 @@ import (
 )
 
 type Button struct {
-	click   gesture.Click
-	clicks  int
-	history []Click
+	click gesture.Click
+	// clicks tracks the number of unreported clicks.
+	clicks int
+	// prevClicks tracks the number of unreported clicks
+	// that belong to the previous frame.
+	prevClicks int
+	history    []Click
 }
 
 // Click represents a historic click.
@@ -24,6 +28,42 @@ type Click struct {
 }
 
 func (b *Button) Clicked(gtx *layout.Context) bool {
+	b.processEvents(gtx)
+	if b.clicks > 0 {
+		b.clicks--
+		if b.prevClicks > 0 {
+			b.prevClicks--
+		}
+		if b.clicks > 0 {
+			// Ensure timely delivery of remaining clicks.
+			op.InvalidateOp{}.Add(gtx.Ops)
+		}
+		return true
+	}
+	return false
+}
+
+func (b *Button) History() []Click {
+	return b.history
+}
+
+func (b *Button) Layout(gtx *layout.Context) {
+	// Flush clicks from before the previous frame.
+	b.clicks -= b.prevClicks
+	b.prevClicks = 0
+	b.processEvents(gtx)
+	b.click.Add(gtx.Ops)
+	for len(b.history) > 0 {
+		c := b.history[0]
+		if gtx.Now().Sub(c.Time) < 1*time.Second {
+			break
+		}
+		copy(b.history, b.history[1:])
+		b.history = b.history[:len(b.history)-1]
+	}
+}
+
+func (b *Button) processEvents(gtx *layout.Context) {
 	for _, e := range b.click.Events(gtx) {
 		switch e.Type {
 		case gesture.TypeClick:
@@ -35,36 +75,4 @@ func (b *Button) Clicked(gtx *layout.Context) bool {
 			})
 		}
 	}
-	if b.clicks > 0 {
-		b.clicks--
-		if b.clicks > 0 {
-			// Ensure timely delivery of remaining clicks.
-			op.InvalidateOp{}.Add(gtx.Ops)
-		}
-		return true
-	}
-	return false
-}
-
-func (b *Button) Active() bool {
-	return b.click.Active()
-}
-
-func (b *Button) History() []Click {
-	return b.history
-}
-
-func (b *Button) Layout(gtx *layout.Context) {
-	b.click.Add(gtx.Ops)
-	if !b.Active() {
-		b.clicks = 0
-	}
-	for len(b.history) > 0 {
-		c := b.history[0]
-		if gtx.Now().Sub(c.Time) < 1*time.Second {
-			break
-		}
-		copy(b.history, b.history[1:])
-		b.history = b.history[:len(b.history)-1]
-	}
 }

widget/editor.go

@@ -60,6 +60,8 @@ type Editor struct {
 
 	// events is the list of events not yet processed.
 	events []EditorEvent
+	// prevEvents is the number of events from the previous frame.
+	prevEvents int
 }
 
 type EditorEvent interface {
@@ -90,6 +92,7 @@ func (e *Editor) Events(gtx *layout.Context) []EditorEvent {
 	e.processEvents(gtx)
 	events := e.events
 	e.events = nil
+	e.prevEvents = 0
 	return events
 }
 
@@ -177,15 +180,16 @@ func (e *Editor) Focus() {
 
 // Layout lays out the editor.
 func (e *Editor) Layout(gtx *layout.Context, sh *text.Shaper, font text.Font) {
+	// Flush events from before the previous frame.
+	copy(e.events, e.events[e.prevEvents:])
+	e.events = e.events[:len(e.events)-e.prevEvents]
+	e.prevEvents = len(e.events)
 	if e.font != font {
 		e.invalidate()
 		e.font = font
 	}
 	e.processEvents(gtx)
 	e.layout(gtx, sh)
-	if !e.clicker.Active() {
-		e.events = nil
-	}
 }
 
 func (e *Editor) layout(gtx *layout.Context, sh *text.Shaper) {

widget/material/button.go

@@ -78,10 +78,6 @@ func (t *Theme) IconButton(icon *Icon) IconButton {
 func (b Button) Layout(gtx *layout.Context, button *widget.Button) {
 	col := b.Color
 	bgcol := b.Background
-	if !button.Active() {
-		col = rgb(0x888888)
-		bgcol = rgb(0xcccccc)
-	}
 	st := layout.Stack{Alignment: layout.Center}
 	hmin := gtx.Constraints.Width.Min
 	vmin := gtx.Constraints.Height.Min
@@ -128,9 +124,6 @@ func (b IconButton) Layout(gtx *layout.Context, button *widget.Button) {
 		button.Layout(gtx)
 	})
 	bgcol := b.Background
-	if !button.Active() {
-		bgcol = rgb(0xcccccc)
-	}
 	bg := st.Expand(gtx, func() {
 		size := float32(gtx.Constraints.Width.Min)
 		rr := float32(size) * .5