[gtk+] widget: Improve hack to ignore drags from widgets using motion events

[Matthias Clasen <matthiasc src gnome org>]

commit 08494f86a062713ca99f71a0cc29bde9e762592c
Author: Carlos Garnacho <carlosg gnome org>
Date:   Tue Mar 3 22:17:58 2015 +0100

    widget: Improve hack to ignore drags from widgets using motion events
    
    Postpone until the last moment whether the target widget still
    potentially uses updates from this sequence, or window dragging
    actually applies because all gestures on the target went to denied
    state.
    
    This fixes window dragging on empty space in a headerbar that is
    contained in a paned (as in e.g. gedit).
    
    https://bugzilla.gnome.org/show_bug.cgi?id=745562

 gtk/gtkwidget.c        |   12 +++++++-----
 gtk/gtkwidgetprivate.h |    3 ++-
 gtk/gtkwindow.c        |   29 +++++++++++++++++------------
 3 files changed, 26 insertions(+), 18 deletions(-)
---
diff --git a/gtk/gtkwidget.c b/gtk/gtkwidget.c
index c50b684..715105d 100644
--- a/gtk/gtkwidget.c
+++ b/gtk/gtkwidget.c
@@ -17284,7 +17284,8 @@ _gtk_widget_list_controllers (GtkWidget           *widget,
 }
 
 gboolean
-_gtk_widget_consumes_motion (GtkWidget *widget)
+_gtk_widget_consumes_motion (GtkWidget        *widget,
+                             GdkEventSequence *sequence)
 {
   EventControllerData *data;
   GtkWidgetPrivate *priv;
@@ -17301,10 +17302,11 @@ _gtk_widget_consumes_motion (GtkWidget *widget)
       if (data->controller == NULL)
         continue;
 
-      if (!GTK_IS_GESTURE_SINGLE (data->controller))
-        return TRUE;
-      else if (GTK_IS_GESTURE_DRAG (data->controller) ||
-               GTK_IS_GESTURE_SWIPE (data->controller))
+      if ((!GTK_IS_GESTURE_SINGLE (data->controller) ||
+           GTK_IS_GESTURE_DRAG (data->controller) ||
+           GTK_IS_GESTURE_SWIPE (data->controller)) &&
+          gtk_gesture_get_sequence_state (GTK_GESTURE (data->controller),
+                                          sequence) != GTK_EVENT_SEQUENCE_DENIED)
         return TRUE;
     }
 
diff --git a/gtk/gtkwidgetprivate.h b/gtk/gtkwidgetprivate.h
index 676d6e8..7f121aa 100644
--- a/gtk/gtkwidgetprivate.h
+++ b/gtk/gtkwidgetprivate.h
@@ -160,7 +160,8 @@ void              _gtk_widget_remove_controller            (GtkWidget
                                                             GtkEventController  *controller);
 GList *           _gtk_widget_list_controllers             (GtkWidget           *widget,
                                                             GtkPropagationPhase  phase);
-gboolean          _gtk_widget_consumes_motion              (GtkWidget           *widget);
+gboolean          _gtk_widget_consumes_motion              (GtkWidget           *widget,
+                                                            GdkEventSequence    *sequence);
 
 gboolean          gtk_widget_has_tick_callback             (GtkWidget *widget);
 
diff --git a/gtk/gtkwindow.c b/gtk/gtkwindow.c
index ba79229..92d7a03 100644
--- a/gtk/gtkwindow.c
+++ b/gtk/gtkwindow.c
@@ -1509,7 +1509,6 @@ drag_gesture_begin_cb (GtkGestureDrag *gesture,
   GdkEventSequence *sequence;
   GtkWindowRegion region;
   const GdkEvent *event;
-  GtkWidget *event_widget;
 
   sequence = gtk_gesture_single_get_current_sequence (GTK_GESTURE_SINGLE (gesture));
   event = gtk_gesture_get_last_event (GTK_GESTURE (gesture), sequence);
@@ -1517,19 +1516,10 @@ drag_gesture_begin_cb (GtkGestureDrag *gesture,
   if (!event)
     return;
 
-  event_widget = gtk_get_event_widget ((GdkEvent *) event);
+  region = get_active_region_type (window, (GdkEventAny*) event, x, y);
 
-  if (event_widget != GTK_WIDGET (window) &&
-      !gtk_widget_has_grab (event_widget) &&
-      _gtk_widget_consumes_motion (event_widget))
+  if (region != GTK_WINDOW_REGION_TITLE)
     gtk_gesture_set_state (GTK_GESTURE (gesture), GTK_EVENT_SEQUENCE_DENIED);
-  else
-    {
-      region = get_active_region_type (window, (GdkEventAny*) event, x, y);
-
-      if (region != GTK_WINDOW_REGION_TITLE)
-        gtk_gesture_set_state (GTK_GESTURE (gesture), GTK_EVENT_SEQUENCE_DENIED);
-    }
 }
 
 static void
@@ -1549,8 +1539,23 @@ drag_gesture_update_cb (GtkGestureDrag *gesture,
   if (ABS (offset_x) > double_click_distance ||
       ABS (offset_y) > double_click_distance)
     {
+      GdkEventSequence *sequence;
       gdouble start_x, start_y;
       gint x_root, y_root;
+      const GdkEvent *event;
+      GtkWidget *event_widget;
+
+      sequence = gtk_gesture_single_get_current_sequence (GTK_GESTURE_SINGLE (gesture));
+      event = gtk_gesture_get_last_event (GTK_GESTURE (gesture), sequence);
+      event_widget = gtk_get_event_widget ((GdkEvent *) event);
+
+      if (event_widget != GTK_WIDGET (window) &&
+          !gtk_widget_has_grab (event_widget) &&
+          _gtk_widget_consumes_motion (event_widget, sequence))
+        {
+          gtk_gesture_set_state (GTK_GESTURE (gesture), GTK_EVENT_SEQUENCE_DENIED);
+          return;
+        }
 
       gtk_gesture_set_state (GTK_GESTURE (gesture), GTK_EVENT_SEQUENCE_CLAIMED);