[gtk] Fix hover state handling

[Matthias Clasen <matthiasc src gnome org>]

commit 1ada7bbc02bc54d23b337d7e29c0cbd3efd11f35
Author: Matthias Clasen <mclasen redhat com>
Date:   Fri Mar 22 16:33:53 2019 -0400

    Fix hover state handling
    
    We were not paying enough attention to detail when updating
    hover and focus state while generating crossing events. The
    invariant that we need to preserve here is that when a widget
    has focus or hover, its parent does too.

 gtk/gtkmain.c | 38 +++++++++++++++++++++++++++++++++++++-
 1 file changed, 37 insertions(+), 1 deletion(-)
---
diff --git a/gtk/gtkmain.c b/gtk/gtkmain.c
index d95890b52f..193bd10b3c 100644
--- a/gtk/gtkmain.c
+++ b/gtk/gtkmain.c
@@ -1403,6 +1403,42 @@ get_virtual_notify_type (GdkNotifyType notify_type)
     }
 }
 
+/* Determine from crossing mode details whether the ultimate
+ * target is us or a descendant. Keep this code in sync with
+ * gtkeventcontrollerkey.c:update_focus
+ */
+static gboolean
+is_or_contains (gboolean      enter,
+                GdkNotifyType detail)
+{
+  gboolean is = FALSE;
+  gboolean contains = FALSE;
+
+  switch (detail)
+    {
+    case GDK_NOTIFY_VIRTUAL:
+    case GDK_NOTIFY_NONLINEAR_VIRTUAL:
+      is = FALSE;
+      contains = enter;
+      break;
+    case GDK_NOTIFY_ANCESTOR:
+    case GDK_NOTIFY_NONLINEAR:
+      is = enter;
+      contains = FALSE;
+      break;
+    case GDK_NOTIFY_INFERIOR:
+      is = enter;
+      contains = !enter;
+      break;
+    case GDK_NOTIFY_UNKNOWN:
+    default:
+      g_warning ("Unknown focus change detail");
+      return;
+    }
+
+  return is || contains;
+}
+
 static void
 synth_crossing (GtkWidget       *widget,
                 GtkWidget       *toplevel,
@@ -1451,7 +1487,7 @@ synth_crossing (GtkWidget       *widget,
   if (event->any.surface)
     g_object_ref (event->any.surface);
 
-  if (enter)
+  if (is_or_contains (enter, notify_type))
     gtk_widget_set_state_flags (widget, flags, FALSE);
   else
     gtk_widget_unset_state_flags (widget, flags);