[gtk] widget: Parent widgets may also consume motions

[Timm Bäder <baedert src gnome org>]

commit b7963a06ab87a1b1591de3800bda889ba30f05e1
Author: Timm Bäder <mail baedert org>
Date:   Wed Nov 21 17:51:10 2018 +0100

    widget: Parent widgets may also consume motions
    
    This is important when the target widget of an event is not the one that
    would otherwise receive the gesture. For example, the GtkSwitch
    implementation currently attaches a pan gesture to the switch itself,
    but the target widget below the pointer might be the switch slider or
    label.
    
    See #1465

 gtk/gtkwidget.c | 31 ++++++++++++++++++-------------
 1 file changed, 18 insertions(+), 13 deletions(-)
---
diff --git a/gtk/gtkwidget.c b/gtk/gtkwidget.c
index 587bf81b0f..eeb5bc6423 100644
--- a/gtk/gtkwidget.c
+++ b/gtk/gtkwidget.c
@@ -12925,23 +12925,28 @@ _gtk_widget_consumes_motion (GtkWidget        *widget,
                              GdkEventSequence *sequence)
 {
   GtkWidgetPrivate *priv = gtk_widget_get_instance_private (widget);
-  GList *l;
-
-  g_return_val_if_fail (GTK_IS_WIDGET (widget), FALSE);
 
-  for (l = priv->event_controllers; l; l = l->next)
+  while (widget != NULL && !GTK_IS_WINDOW (widget))
     {
-      GtkEventController *controller = l->data;
+      GList *l;
 
-      if (controller == NULL ||
-          !GTK_IS_GESTURE (controller))
-        continue;
+      for (l = priv->event_controllers; l; l = l->next)
+        {
+          GtkEventController *controller = l->data;
 
-      if ((!GTK_IS_GESTURE_SINGLE (controller) ||
-           GTK_IS_GESTURE_DRAG (controller) ||
-           GTK_IS_GESTURE_SWIPE (controller)) &&
-          gtk_gesture_handles_sequence (GTK_GESTURE (controller), sequence))
-        return TRUE;
+          if (controller == NULL ||
+              !GTK_IS_GESTURE (controller))
+            continue;
+
+          if ((!GTK_IS_GESTURE_SINGLE (controller) ||
+               GTK_IS_GESTURE_DRAG (controller) ||
+               GTK_IS_GESTURE_SWIPE (controller)) &&
+              gtk_gesture_handles_sequence (GTK_GESTURE (controller), sequence))
+            return TRUE;
+        }
+
+      widget = priv->parent;
+      priv = gtk_widget_get_instance_private (widget);
     }
 
   return FALSE;