Simplify atomics with CAS operation

internal/widget/base.go

@@ -81,12 +81,10 @@ func (w *Base) Visible() bool {
 
 // Show this widget so it becomes visible
 func (w *Base) Show() {
-	if w.Visible() {
-		return
+	if !w.hidden.CompareAndSwap(true, false) {
+		return // Visible already
 	}
 
-	w.hidden.Store(false)
-
 	impl := w.super()
 	if impl == nil {
 		return
@@ -96,12 +94,10 @@ func (w *Base) Show() {
 
 // Hide this widget so it is no longer visible
 func (w *Base) Hide() {
-	if !w.Visible() {
-		return
+	if !w.hidden.CompareAndSwap(false, true) {
+		return // Hidden already
 	}
 
-	w.hidden.Store(true)
-
 	impl := w.super()
 	if impl == nil {
 		return

widget/widget.go

@@ -71,7 +71,7 @@ func (w *BaseWidget) MinSize() fyne.Size {
 
 	r := cache.Renderer(impl)
 	if r == nil {
-		return fyne.NewSize(0, 0)
+		return fyne.Size{}
 	}
 
 	return r.MinSize()
@@ -160,12 +160,10 @@ type DisableableWidget struct {
 
 // Enable this widget, updating any style or features appropriately.
 func (w *DisableableWidget) Enable() {
-	if !w.Disabled() {
-		return
+	if !w.disabled.CompareAndSwap(true, false) {
+		return // Enabled already
 	}
 
-	w.disabled.Store(false)
-
 	impl := w.super()
 	if impl == nil {
 		return
@@ -175,12 +173,10 @@ func (w *DisableableWidget) Enable() {
 
 // Disable this widget so that it cannot be interacted with, updating any style appropriately.
 func (w *DisableableWidget) Disable() {
-	if w.Disabled() {
-		return
+	if !w.disabled.CompareAndSwap(false, true) {
+		return // Disabled already
 	}
 
-	w.disabled.Store(true)
-
 	impl := w.super()
 	if impl == nil {
 		return