scalebutton: Add an active property

This is set to TRUE while the popup is visible.
We will use it to prevent the button from being
hidden while the user is interacting with it.

gtk/gtkscalebutton.c

@@ -98,7 +98,8 @@ enum
   PROP_VALUE,
   PROP_SIZE,
   PROP_ADJUSTMENT,
-  PROP_ICONS
+  PROP_ICONS,
+  PROP_ACTIVE
 };
 
 typedef struct
@@ -248,6 +249,13 @@ gtk_scale_button_class_init (GtkScaleButtonClass *klass)
                                                        G_TYPE_STRV,
                                                        GTK_PARAM_READWRITE));
 
+  g_object_class_install_property (gobject_class,
+                                   PROP_ACTIVE,
+                                   g_param_spec_boolean ("active",
+                                                         P_("Active"),
+                                                         P_("Active"),
+                                                         FALSE,
+                                                         G_PARAM_READABLE));
   /**
    * GtkScaleButton::value-changed:
    * @button: the object which received the signal
@@ -403,6 +411,14 @@ gtk_scale_button_closed (GtkScaleButton *button)
   gtk_toggle_button_set_active (GTK_TOGGLE_BUTTON (priv->button), FALSE);
 }
 
+static void
+notify_active (GObject    *object,
+               GParamSpec *pspec,
+               GObject    *button)
+{
+  g_object_notify (button, "active");
+}
+
 static void
 gtk_scale_button_init (GtkScaleButton *button)
 {
@@ -416,6 +432,9 @@ gtk_scale_button_init (GtkScaleButton *button)
   gtk_widget_init_template (GTK_WIDGET (button));
   gtk_widget_set_parent (priv->dock, GTK_WIDGET (button));
 
+  g_signal_connect (priv->dock, "notify::visible",
+                    G_CALLBACK (notify_active), button);
+
   /* Need a local reference to the adjustment */
   priv->adjustment = gtk_adjustment_new (0, 0, 100, 2, 20, 0);
   g_object_ref_sink (priv->adjustment);
@@ -503,6 +522,9 @@ gtk_scale_button_get_property (GObject     *object,
     case PROP_ICONS:
       g_value_set_boxed (value, priv->icon_list);
       break;
+    case PROP_ACTIVE:
+      g_value_set_boolean (value, gtk_widget_get_visible (priv->dock));
+      break;
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
       break;