[gtk/BUG_scale_button_propagated_state] GtkScaleButton: fix unwanted state propagation

[Nelson Benítez León <nbenitez src gnome org>]

commit dad8d2dc1bb9dcabc33357a6e67a3a69d3ab3d71
Author: Nelson Benítez León <nbenitezl gmail com>
Date:   Fri Sep 6 23:52:48 2019 -0400

    GtkScaleButton: fix unwanted state propagation
    
    GtkScaleButton/GtkVolumeButton use a popover
    to show content. With the new GTK4 event model
    clicking or hovering on that child popover produces
    ACTIVE and PRELIGHT states that are propagated to
    the main button, this is unwanted behaviour as the
    button's appearance changes according to those.
    
    We connect to the "state-flags-changed" signal of
    GtkScaleButton, and remove the unwanted state flags
    after verifying they're coming from the popover.
    
    Fixes issue #2063

 gtk/gtkscalebutton.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)
---
diff --git a/gtk/gtkscalebutton.c b/gtk/gtkscalebutton.c
index fa683db75f..836cc3c8c3 100644
--- a/gtk/gtkscalebutton.c
+++ b/gtk/gtkscalebutton.c
@@ -157,6 +157,9 @@ static gboolean gtk_scale_button_scroll_controller_scroll (GtkEventControllerScr
                                                            gdouble                   dx,
                                                            gdouble                   dy,
                                                            GtkScaleButton           *button);
+static void     gtk_scale_button_state_flags_changed      (GtkWidget           *widget,
+                                                           GtkStateFlags        previous_state,
+                                                           gpointer             user_data);
 
 G_DEFINE_TYPE_WITH_CODE (GtkScaleButton, gtk_scale_button, GTK_TYPE_BUTTON,
                          G_ADD_PRIVATE (GtkScaleButton)
@@ -378,6 +381,8 @@ gtk_scale_button_init (GtkScaleButton *button)
 
   gtk_widget_init_template (GTK_WIDGET (button));
   gtk_popover_set_relative_to (GTK_POPOVER (priv->dock), GTK_WIDGET (button));
+  g_signal_connect (button, "state-flags-changed",
+                    G_CALLBACK (gtk_scale_button_state_flags_changed), priv->dock);
 
   /* Need a local reference to the adjustment */
   priv->adjustment = gtk_adjustment_new (0, 0, 100, 2, 20, 0);
@@ -498,6 +503,7 @@ gtk_scale_button_dispose (GObject *object)
   GtkScaleButton *button = GTK_SCALE_BUTTON (object);
   GtkScaleButtonPrivate *priv = gtk_scale_button_get_instance_private (button);
 
+  g_signal_handlers_disconnect_by_func (button, gtk_scale_button_state_flags_changed, priv->dock);
   g_clear_pointer (&priv->dock, gtk_widget_unparent);
 
   if (priv->click_id != 0)
@@ -1010,3 +1016,24 @@ gtk_scale_button_size_allocate (GtkWidget *widget,
 
   gtk_native_check_resize (GTK_NATIVE (priv->dock));
 }
+
+/* Removes ACTIVE and PRELIGHT states from the main button
+ * if they were propagated from the popover. Issue #2063 */
+static void
+gtk_scale_button_state_flags_changed (GtkWidget     *widget,
+                                      GtkStateFlags  previous_state,
+                                      gpointer       user_data)
+{
+  GtkWidget *popover = GTK_WIDGET (user_data);
+  GtkStateFlags state_popover = gtk_widget_get_state_flags (popover);
+  GtkStateFlags flags_to_unset = 0;
+
+  if (state_popover & GTK_STATE_FLAG_ACTIVE)
+    flags_to_unset |= GTK_STATE_FLAG_ACTIVE;
+
+  if (state_popover & GTK_STATE_FLAG_PRELIGHT)
+    flags_to_unset |= GTK_STATE_FLAG_PRELIGHT;
+
+  if (flags_to_unset)
+    gtk_widget_unset_state_flags (widget, flags_to_unset);
+}