widget: [API] move Enum state update to Changed, rename it to Update

Similar to an earlier change for other widgets, this change separate
Enum state changes for access earlier than Layout.

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

widget/enum.go

@@ -20,8 +20,6 @@ type Enum struct {
 	focus   string
 	focused bool
 
-	changed bool
-
 	keys []*enumKey
 }
 
@@ -40,40 +38,15 @@ func (e *Enum) index(k string) *enumKey {
 	return nil
 }
 
-// Changed reports whether Value has changed by user interaction since the last
-// call to Changed.
-func (e *Enum) Changed() bool {
-	changed := e.changed
-	e.changed = false
-	return changed
-}
-
-// Hovered returns the key that is highlighted, or false if none are.
-func (e *Enum) Hovered() (string, bool) {
-	return e.hovered, e.hovering
-}
-
-// Focused reports the focused key, or false if no key is focused.
-func (e *Enum) Focused() (string, bool) {
-	return e.focus, e.focused
-}
-
-// Layout adds the event handler for the key k.
-func (e *Enum) Layout(gtx layout.Context, k string, content layout.Widget) layout.Dimensions {
-	m := op.Record(gtx.Ops)
-	dims := content(gtx)
-	c := m.Stop()
-	defer clip.Rect{Max: dims.Size}.Push(gtx.Ops).Pop()
-
-	state := e.index(k)
-	if state == nil {
-		state = &enumKey{
-			key: k,
+// Update the state and report whether Value has changed by user interaction.
+func (e *Enum) Update(gtx layout.Context) bool {
+	if gtx.Queue == nil {
+		e.focused = false
 	}
-		e.keys = append(e.keys, state)
-	}
-	clk := &state.click
-	for _, ev := range clk.Events(gtx) {
+	e.hovering = false
+	changed := false
+	for _, state := range e.keys {
+		for _, ev := range state.click.Events(gtx) {
 			switch ev.Kind {
 			case gesture.KindPress:
 				if ev.Source == pointer.Mouse {
@@ -82,7 +55,7 @@ func (e *Enum) Layout(gtx layout.Context, k string, content layout.Widget) layou
 			case gesture.KindClick:
 				if state.key != e.Value {
 					e.Value = state.key
-				e.changed = true
+					changed = true
 				}
 			}
 		}
@@ -104,23 +77,49 @@ func (e *Enum) Layout(gtx layout.Context, k string, content layout.Widget) layou
 				}
 				if state.key != e.Value {
 					e.Value = state.key
-				e.changed = true
+					changed = true
 				}
 			}
 		}
-	if clk.Hovered() {
-		e.hovered = k
+		if state.click.Hovered() {
+			e.hovered = state.key
 			e.hovering = true
-	} else if e.hovered == k {
-		e.hovering = false
+		}
 	}
 
+	return changed
+}
+
+// Hovered returns the key that is highlighted, or false if none are.
+func (e *Enum) Hovered() (string, bool) {
+	return e.hovered, e.hovering
+}
+
+// Focused reports the focused key, or false if no key is focused.
+func (e *Enum) Focused() (string, bool) {
+	return e.focus, e.focused
+}
+
+// Layout adds the event handler for the key k.
+func (e *Enum) Layout(gtx layout.Context, k string, content layout.Widget) layout.Dimensions {
+	e.Update(gtx)
+	m := op.Record(gtx.Ops)
+	dims := content(gtx)
+	c := m.Stop()
+	defer clip.Rect{Max: dims.Size}.Push(gtx.Ops).Pop()
+
+	state := e.index(k)
+	if state == nil {
+		state = &enumKey{
+			key: k,
+		}
+		e.keys = append(e.keys, state)
+	}
+	clk := &state.click
 	clk.Add(gtx.Ops)
 	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.EnabledOp(enabled).Add(gtx.Ops)