[libhandy] stackable-box: Add get_adjacent_child()

[Adrien Plazas <aplazas src gnome org>]

commit 411afd2186fd9e2af450ce44e68be1d47b36d733
Author: Alexander Mikhaylenko <alexm gnome org>
Date:   Tue Jun 2 00:16:45 2020 +0500

    stackable-box: Add get_adjacent_child()
    
    Signed-off-by: Alexander Mikhaylenko <alexm gnome org>

 src/hdy-stackable-box-private.h |  2 ++
 src/hdy-stackable-box.c         | 30 ++++++++++++++++++++++++++++++
 2 files changed, 32 insertions(+)
---
diff --git a/src/hdy-stackable-box-private.h b/src/hdy-stackable-box-private.h
index ac403713..605e80b4 100644
--- a/src/hdy-stackable-box-private.h
+++ b/src/hdy-stackable-box-private.h
@@ -65,6 +65,8 @@ gboolean         hdy_stackable_box_get_can_swipe_forward (HdyStackableBox *self)
 void             hdy_stackable_box_set_can_swipe_forward (HdyStackableBox *self,
                                                           gboolean         can_swipe_forward);
 
+GtkWidget       *hdy_stackable_box_get_adjacent_child (HdyStackableBox        *self,
+                                                       HdyNavigationDirection  direction);
 gboolean         hdy_stackable_box_navigate (HdyStackableBox        *self,
                                              HdyNavigationDirection  direction);
 
diff --git a/src/hdy-stackable-box.c b/src/hdy-stackable-box.c
index 318bd17c..51e93165 100644
--- a/src/hdy-stackable-box.c
+++ b/src/hdy-stackable-box.c
@@ -1333,6 +1333,36 @@ find_swipeable_child (HdyStackableBox        *self,
   return child;
 }
 
+/**
+ * hdy_stackable_box_get_adjacent_child
+ * @self: a #HdyStackableBox
+ * @direction: the direction
+ *
+ * Gets the previous or next child that doesn't have 'allow-visible' child
+ * property set to %FALSE, or %NULL if it doesn't exist. This will be the same
+ * widget hdy_stackable_box_navigate() will navigate to.
+ *
+ * Returns: (nullable) (transfer none): the previous or next child, or
+ *   %NULL if it doesn't exist.
+ *
+ * Since: 1.0
+ */
+GtkWidget *
+hdy_stackable_box_get_adjacent_child (HdyStackableBox        *self,
+                                      HdyNavigationDirection  direction)
+{
+  HdyStackableBoxChildInfo *child;
+
+  g_return_val_if_fail (HDY_IS_STACKABLE_BOX (self), NULL);
+
+  child = find_swipeable_child (self, direction);
+
+  if (!child)
+    return NULL;
+
+  return child->widget;
+}
+
 /**
  * hdy_stackable_box_navigate
  * @self: a #HdyStackableBox