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>

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]
-	}
 }