From b39d1bdac724f2c454a90931856462ef3cf12932 Mon Sep 17 00:00:00 2001
From: Elias Naur <mail@eliasnaur.com>
Date: Wed, 3 Mar 2021 18:12:39 +0100
Subject: [PATCH] widget: handle hovering of the empty Enum key

Before this change, a radio button with the empty key ("") would be
displayed as hovering if no other button were.

It's still not possible to have no radio buttons selected when one of
them is the empty key. If that's becomes necessary, Enum.Value can be
converted to a *string.

Signed-off-by: Elias Naur <mail@eliasnaur.com>
---
 widget/enum.go                 | 17 ++++++++++++-----
 widget/material/radiobutton.go |  3 ++-
 2 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/widget/enum.go b/widget/enum.go
index 883d0c26..1c9c509d 100644
--- a/widget/enum.go
+++ b/widget/enum.go
@@ -10,8 +10,9 @@ import (
 )
 
 type Enum struct {
-	Value   string
-	Hovered string
+	Value    string
+	hovered  string
+	hovering bool
 
 	changed bool
 
@@ -36,6 +37,11 @@ func (e *Enum) Changed() bool {
 	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
+}
+
 // Layout adds the event handler for key.
 func (e *Enum) Layout(gtx layout.Context, key string) layout.Dimensions {
 	defer op.Save(gtx.Ops).Load()
@@ -57,11 +63,12 @@ func (e *Enum) Layout(gtx layout.Context, key string) layout.Dimensions {
 				}
 			}
 		}
-		if e.Hovered == key {
-			e.Hovered = ""
+		if e.hovering && e.hovered == key {
+			e.hovering = false
 		}
 		if clk.Hovered() {
-			e.Hovered = key
+			e.hovered = key
+			e.hovering = true
 		}
 		clk.Add(gtx.Ops)
 	}
diff --git a/widget/material/radiobutton.go b/widget/material/radiobutton.go
index 24e9537d..96544a6f 100644
--- a/widget/material/radiobutton.go
+++ b/widget/material/radiobutton.go
@@ -36,7 +36,8 @@ func RadioButton(th *Theme, group *widget.Enum, key, label string) RadioButtonSt
 
 // Layout updates enum and displays the radio button.
 func (r RadioButtonStyle) Layout(gtx layout.Context) layout.Dimensions {
-	dims := r.layout(gtx, r.Group.Value == r.Key, r.Group.Hovered == r.Key)
+	hovered, hovering := r.Group.Hovered()
+	dims := r.layout(gtx, r.Group.Value == r.Key, hovering && hovered == r.Key)
 	gtx.Constraints.Min = dims.Size
 	r.Group.Layout(gtx, r.Key)
 	return dims