io/semantic: [API] replace DisabledOp with EnabledOp

The double-negative DisabledOp is harder to understand than a
straightforward EnabledOp. Note that the absence of an EnabledOp
implies still means that the widget is enabled.

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

widget/bool.go

@@ -49,7 +49,7 @@ func (b *Bool) Layout(gtx layout.Context, w layout.Widget) layout.Dimensions {
 			b.changed = true
 		}
 		semantic.SelectedOp(b.Value).Add(gtx.Ops)
-		semantic.DisabledOp(gtx.Queue == nil).Add(gtx.Ops)
+		semantic.EnabledOp(gtx.Queue != nil).Add(gtx.Ops)
 		return w(gtx)
 	})
 	return dims

widget/button.go

@@ -113,10 +113,10 @@ func (b *Clickable) Layout(gtx layout.Context, w layout.Widget) layout.Dimension
 	dims := w(gtx)
 	c := m.Stop()
 	defer clip.Rect(image.Rectangle{Max: dims.Size}).Push(gtx.Ops).Pop()
-	disabled := gtx.Queue == nil
-	semantic.DisabledOp(disabled).Add(gtx.Ops)
+	enabled := gtx.Queue != nil
+	semantic.EnabledOp(enabled).Add(gtx.Ops)
 	b.click.Add(gtx.Ops)
-	if !disabled {
+	if enabled {
 		keys := key.Set("⏎|Space")
 		if !b.focused {
 			keys = ""

widget/enum.go

@@ -116,14 +116,14 @@ func (e *Enum) Layout(gtx layout.Context, k string, content layout.Widget) layou
 	}
 
 	clk.Add(gtx.Ops)
-	disabled := gtx.Queue == nil
-	if !disabled {
+	enabled := gtx.Queue != nil
+	if enabled {
 		key.InputOp{Tag: &state.tag, Keys: "⏎|Space"}.Add(gtx.Ops)
 	} else if e.focus == k {
 		e.focused = false
 	}
 	semantic.SelectedOp(k == e.Value).Add(gtx.Ops)
-	semantic.DisabledOp(disabled).Add(gtx.Ops)
+	semantic.EnabledOp(enabled).Add(gtx.Ops)
 	c.Add(gtx.Ops)
 
 	return dims