wip: Add more information to crossing events

Add fields for direct descendents to GtkCrossingData,
and populate them when emitting focus change events.

Also add accessors for these fields to GtkEventControllerKey,
and verify that they are set properly in the focus test.

Not done yet: Do the same for pointer crossing events.

4 files changed, 117 insertions, 8 deletions

diff --git a/gtk/gtkeventcontroller.h b/gtk/gtkeventcontroller.h
index 38569453f1..2cd8167c03 100644
--- a/gtk/gtkeventcontroller.h
+++ b/gtk/gtkeventcontroller.h
@@ -48,10 +48,15 @@ typedef struct _GtkCrossingData GtkCrossingData;
  * @direction: whether this is a focus-in or focus-out event
  * @mode: the crossing mode
  * @old_target: the old target
+ * @old_descendent: the direct child of the receiving widget that
+ *     is an ancestor of @old_target, or %NULL if @old_target is not
+ *     a descendent of the receiving widget
  * @new_target: the new target
+ * @new_descendent: the direct child of the receiving widget that
+ *     is an ancestor of @new_target, or %NULL if @new_target is not
+ *     a descendent of the receiving widget
  *
- * The struct that is passed to gtk_event_controller_handle_crossing()
- * and is also passed to #GtkEventControllerKey::focus-change.
+ * The struct that is passed to gtk_event_controller_handle_crossing().
  *
  * The @old_target and @new_target fields are set to the old or new
  * focus or hover location.
@@ -61,7 +66,9 @@ struct _GtkCrossingData {
   GtkCrossingDirection direction;
   GdkCrossingMode mode;
   GtkWidget *old_target;
+  GtkWidget *old_descendent;
   GtkWidget *new_target;
+  GtkWidget *new_descendent;
 };
 
 GDK_AVAILABLE_IN_ALL
diff --git a/gtk/gtkeventcontrollerkey.c b/gtk/gtkeventcontrollerkey.c
index a8a5912d33..14a79e7b0c 100644
--- a/gtk/gtkeventcontrollerkey.c
+++ b/gtk/gtkeventcontrollerkey.c
@@ -548,6 +548,24 @@ gtk_event_controller_key_get_focus_target (GtkEventControllerKey *controller)
   return controller->current_crossing->new_target;
 }
 
+GtkWidget *
+gtk_event_controller_key_get_old_focus_child (GtkEventControllerKey *controller)
+{
+  g_return_val_if_fail (GTK_IS_EVENT_CONTROLLER_KEY (controller), NULL);
+  g_return_val_if_fail (controller->current_crossing != NULL, NULL);
+
+  return controller->current_crossing->old_descendent;
+}
+
+GtkWidget *
+gtk_event_controller_key_get_new_focus_child (GtkEventControllerKey *controller)
+{
+  g_return_val_if_fail (GTK_IS_EVENT_CONTROLLER_KEY (controller), NULL);
+  g_return_val_if_fail (controller->current_crossing != NULL, NULL);
+
+  return controller->current_crossing->new_descendent;
+}
+
 /**
  * gtk_event_controller_key_contains_focus:
  * @self: a #GtkEventControllerKey
diff --git a/gtk/gtkeventcontrollerkey.h b/gtk/gtkeventcontrollerkey.h
index 755947d255..4aa22777d6 100644
--- a/gtk/gtkeventcontrollerkey.h
+++ b/gtk/gtkeventcontrollerkey.h
@@ -62,6 +62,10 @@ GDK_AVAILABLE_IN_ALL
 GtkWidget *         gtk_event_controller_key_get_focus_origin   (GtkEventControllerKey  *controller);
 GDK_AVAILABLE_IN_ALL
 GtkWidget *         gtk_event_controller_key_get_focus_target   (GtkEventControllerKey  *controller);
+GDK_AVAILABLE_IN_ALL
+GtkWidget *         gtk_event_controller_key_get_old_focus_child (GtkEventControllerKey  *controller);
+GDK_AVAILABLE_IN_ALL
+GtkWidget *         gtk_event_controller_key_get_new_focus_child (GtkEventControllerKey  *controller);
 
 GDK_AVAILABLE_IN_ALL
 gboolean            gtk_event_controller_key_contains_focus     (GtkEventControllerKey  *self);
diff --git a/gtk/gtkwindow.c b/gtk/gtkwindow.c
index 736d76441b..d399d3c7d7 100644
--- a/gtk/gtkwindow.c
+++ b/gtk/gtkwindow.c
@@ -6347,14 +6347,48 @@ gtk_window_move_focus (GtkWidget        *widget,
 }
 
 static void
+check_crossing_invariants (GtkWidget *widget,
+                           GtkCrossingData *crossing)
+{
+  if (crossing->old_target == NULL)
+    g_assert (crossing->old_descendent == NULL);
+  else if (crossing->old_descendent == NULL)
+    g_assert (crossing->old_target == widget || !gtk_widget_is_ancestor (crossing->old_target, widget));
+  else
+    {
+      g_assert (gtk_widget_get_parent (crossing->old_descendent) == widget);
+      g_assert (gtk_widget_is_ancestor (crossing->old_descendent, widget));
+      g_assert (crossing->old_target == crossing->old_descendent || gtk_widget_is_ancestor (crossing->old_target, crossing->old_descendent));
+    }
+  if (crossing->new_target == NULL)
+    g_assert (crossing->new_descendent == NULL);
+  else if (crossing->new_descendent == NULL)
+    g_assert (crossing->new_target == widget || !gtk_widget_is_ancestor (crossing->new_target, widget));
+  else
+    {
+      g_assert (gtk_widget_get_parent (crossing->new_descendent) == widget);
+      g_assert (gtk_widget_is_ancestor (crossing->new_descendent, widget));
+      g_assert (crossing->new_target == crossing->new_descendent || gtk_widget_is_ancestor (crossing->new_target, crossing->new_descendent));
+    }
+}
+
+static void
 synthesize_focus_change_events (GtkWindow *window,
                                 GtkWidget *old_focus,
                                 GtkWidget *new_focus)
 {
   GtkCrossingData crossing;
+  GtkWidget *ancestor;
   GtkWidget *widget, *focus_child;
   GList *list, *l;
   GtkStateFlags flags;
+  GtkWidget *prev;
+  gboolean seen_ancestor;
+
+  if (old_focus && new_focus)
+    ancestor = gtk_widget_common_ancestor (old_focus, new_focus);
+  else
+    ancestor = NULL;
 
   flags = GTK_STATE_FLAG_FOCUSED;
   if (gtk_window_get_focus_visible (GTK_WINDOW (window)))
@@ -6363,29 +6397,52 @@ synthesize_focus_change_events (GtkWindow *window,
   crossing.type = GTK_CROSSING_FOCUS;
   crossing.mode = GDK_CROSSING_NORMAL;
   crossing.old_target = old_focus;
+  crossing.old_descendent = NULL;
   crossing.new_target = new_focus;
+  crossing.new_descendent = NULL;
 
   crossing.direction = GTK_CROSSING_OUT;
 
+  prev = NULL;
+  seen_ancestor = FALSE;
   widget = old_focus;
   while (widget)
     {
+      crossing.old_descendent = prev;
+      if (seen_ancestor)
+        {
+          crossing.new_descendent = new_focus ? prev : NULL;
+        }
+      else if (widget == ancestor)
+        {
+          GtkWidget *w;
+
+          crossing.new_descendent = NULL;
+          for (w = new_focus; w != ancestor; w = gtk_widget_get_parent (w))
+            crossing.new_descendent = w;
+
+          seen_ancestor = TRUE;
+        }
+      else
+        {
+          crossing.new_descendent = NULL;
+        }
+      
+      check_crossing_invariants (widget, &crossing);
       gtk_widget_handle_crossing (widget, &crossing, 0, 0);
       gtk_widget_unset_state_flags (widget, flags);
       gtk_widget_set_focus_child (widget, NULL);
+      prev = widget;
       widget = gtk_widget_get_parent (widget);
     }
 
   list = NULL;
-  widget = new_focus;
-  while (widget)
-    {
-      list = g_list_prepend (list, widget);
-      widget = gtk_widget_get_parent (widget);
-    }
+  for (widget = new_focus; widget; widget = gtk_widget_get_parent (widget))
+    list = g_list_prepend (list, widget);
 
   crossing.direction = GTK_CROSSING_IN;
 
+  seen_ancestor = FALSE;
   for (l = list; l; l = l->next)
     {
       widget = l->data;
@@ -6393,6 +6450,29 @@ synthesize_focus_change_events (GtkWindow *window,
         focus_child = l->next->data;
       else
         focus_child = NULL;
+
+      crossing.new_descendent = focus_child;
+      if (seen_ancestor)
+        {
+          crossing.old_descendent = NULL;
+        }
+      else if (widget == ancestor)
+        {
+          GtkWidget *w;
+
+          crossing.old_descendent = NULL;
+          for (w = old_focus; w != ancestor; w = gtk_widget_get_parent (w))
+            {
+              crossing.old_descendent = w;
+            }
+
+          seen_ancestor = TRUE;
+        }
+      else
+        {
+          crossing.old_descendent = old_focus ? focus_child : NULL;
+        }
+      check_crossing_invariants (widget, &crossing);
       gtk_widget_handle_crossing (widget, &crossing, 0, 0);
       gtk_widget_set_state_flags (widget, flags, FALSE);
       gtk_widget_set_focus_child (widget, focus_child);