From a2cddc8da03a25a7d7cb7011a9965eab9bca7870 Mon Sep 17 00:00:00 2001
From: Tom Henderson <tomh@tomh.org>
Date: Tue, 7 Sep 2021 16:22:23 -0700
Subject: [PATCH] mobility: Expose child mobility model to parent position

---
 .../model/hierarchical-mobility-model.cc      |  2 +-
 src/mobility/model/mobility-model.cc          | 13 ++++++++++++
 src/mobility/model/mobility-model.h           | 20 +++++++++++++++++++
 3 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/src/mobility/model/hierarchical-mobility-model.cc b/src/mobility/model/hierarchical-mobility-model.cc
index 6be31ec04..de75b2d6b 100644
--- a/src/mobility/model/hierarchical-mobility-model.cc
+++ b/src/mobility/model/hierarchical-mobility-model.cc
@@ -117,7 +117,7 @@ HierarchicalMobilityModel::DoGetPosition (void) const
       return m_child->GetPosition ();
     }
   Vector parentPosition = m_parent->GetPosition ();
-  Vector childPosition = m_child->GetPosition ();
+  Vector childPosition = m_child->GetPositionWithReference (parentPosition);
   return Vector (parentPosition.x + childPosition.x,
                  parentPosition.y + childPosition.y,
                  parentPosition.z + childPosition.z);
diff --git a/src/mobility/model/mobility-model.cc b/src/mobility/model/mobility-model.cc
index 022f3d77f..e683f5a17 100644
--- a/src/mobility/model/mobility-model.cc
+++ b/src/mobility/model/mobility-model.cc
@@ -65,6 +65,19 @@ MobilityModel::GetPosition (void) const
 {
   return DoGetPosition ();
 }
+Vector
+MobilityModel::GetPositionWithReference (const Vector& referencePosition) const
+{
+  return DoGetPositionWithReference (referencePosition);
+}
+
+// Default implementation ignores referencePosition
+Vector
+MobilityModel::DoGetPositionWithReference (const Vector& referencePosition) const
+{
+  return DoGetPosition ();
+}
+
 Vector
 MobilityModel::GetVelocity (void) const
 {
diff --git a/src/mobility/model/mobility-model.h b/src/mobility/model/mobility-model.h
index 6333d1af8..60d288f9c 100644
--- a/src/mobility/model/mobility-model.h
+++ b/src/mobility/model/mobility-model.h
@@ -51,6 +51,18 @@ public:
    * \return the current position
    */
   Vector GetPosition (void) const;
+  /**
+   * This method may be used if the position returned may depend on some
+   * reference position provided.  For example, in a hierarchical mobility
+   * model that is buildings-aware, the child mobility model may not be able
+   * to determine if it is inside or outside of a building unless it knows
+   * the parent position.
+   *
+   * \param referencePosition reference position to consider
+   * \return the current position based on the provided referencePosition
+   * \sa ns3::MobilityModel::DoGetPositionWithReference
+   */
+  Vector GetPositionWithReference (const Vector &referencePosition) const;
   /**
    * \param position the position to set.
    */
@@ -100,6 +112,14 @@ private:
    * implement this method.
    */
   virtual Vector DoGetPosition (void) const = 0;
+  /**
+   * \param referencePosition the reference position to consider
+   * \return the current position.
+   *
+   * Unless subclasses override, this method will disregard the reference
+   * position and return "DoGetPosition (void)".
+   */
+  virtual Vector DoGetPositionWithReference (const Vector& referencePosition) const;
   /**
    * \param position the position to set.
    *