feat: Introduce DD4hep GeometryContext

Core/include/Acts/Utilities/detail/ContextType.hpp

@@ -79,6 +79,28 @@ class ContextType {
     return std::any_cast<const std::decay_t<T>&>(m_data);
   }
 
+  /// Retrieve a pointer to the contained type
+  ///
+  /// @note Returns `nullptr` if @p is not the contained type.
+  ///
+  /// @tparam T The type to attempt to retrieve the value as
+  /// @return Pointer to the contained value, may be null
+  template <typename T>
+  std::decay_t<T>* maybeGet() {
+    return std::any_cast<std::decay_t<T>>(&m_data);
+  }
+
+  /// Retrieve a pointer to the contained type
+  ///
+  /// @note Returns `nullptr` if @p is not the contained type.
+  ///
+  /// @tparam T The type to attempt to retrieve the value as
+  /// @return Pointer to the contained value, may be null
+  template <typename T>
+  const std::decay_t<T>* maybeGet() const {
+    return std::any_cast<const std::decay_t<T>>(&m_data);
+  }
+
   /// Check if the contained type is initialized.
   /// @return Boolean indicating whether a type is present
   bool hasValue() const { return m_data.has_value(); }

Plugins/DD4hep/CMakeLists.txt

@@ -7,6 +7,7 @@ add_library(
     src/DD4hepBlueprintFactory.cpp
     src/DD4hepBinningHelpers.cpp
     src/DD4hepDetectorStructure.cpp
+    src/DD4hepGeometryContext.cpp
     src/DD4hepMaterialHelpers.cpp
     src/DD4hepDetectorElement.cpp
     src/DD4hepDetectorSurfaceFactory.cpp

Plugins/DD4hep/include/Acts/Plugins/DD4hep/DD4hepDetectorElement.hpp

@@ -87,6 +87,13 @@ class DD4hepDetectorElement : public TGeoDetectorElement {
   // Give access to the DD4hep detector element
   const dd4hep::DetElement& sourceElement() const { return m_detElement; }
 
+  /// Return the transform for the Element proxy mechanism
+  ///
+  /// @param gctx The current geometry context object, e.g. alignment
+  /// @return The contextual transform matrix that may include misalignment
+  /// @note This method enables dynamic geometry updates through the context
+  const Transform3& transform(const GeometryContext& gctx) const final;
+
  private:
   /// DD4hep detector element
   dd4hep::DetElement m_detElement;

Plugins/DD4hep/include/Acts/Plugins/DD4hep/DD4hepGeometryContext.hpp

@@ -0,0 +1,58 @@
+// This file is part of the ACTS project.
+//
+// Copyright (C) 2016 CERN for the benefit of the ACTS project
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+#pragma once
+
+#include "Acts/Definitions/Algebra.hpp"
+#include "Acts/Geometry/GeometryContext.hpp"
+
+namespace Acts {
+
+class DD4hepDetectorElement;
+
+/// @class GeometryContext
+///
+/// @brief DD4hep specific geometry context for alignment handling
+///
+/// Extends the base GeometryContext to provide DD4hep-specific alignment
+/// capabilities. The context can be active or inactive, controlling whether
+/// alignment corrections should be applied.
+///
+/// @note This context is specifically designed to work with DD4hepDetectorElement
+/// and provides contextual transformations for alignment purposes.
+///
+class DD4hepGeometryContext : public GeometryContext{
+    public:
+    /// Explicit inactive constructor
+    /// Creates an inactive geometry context that skips alignment corrections
+    /// @return DD4hepGeometryContext instance with inactive state
+    static DD4hepGeometryContext inactive() { return DD4hepGeometryContext(false); }
+
+    /// The transform of this detector element within the given context
+    ///
+    /// @param dElement The detector element
+    ///
+    /// @return The transform of the detector element
+    const Transform3& contextualTransform( const DD4hepDetectorElement& dElement) const;
+
+    /// @brief  Return the active status of the context
+    /// @return boolean that indicates if the context is active
+    bool isActive() const { return m_active; }
+
+    private :
+    /// Constructor
+    explicit DD4hepGeometryContext(bool isContextActive) : m_active(isContextActive) {}
+
+    const bool m_active = true;
+
+};
+
+
+}  // namespace Acts
+
+

Plugins/DD4hep/src/DD4hepDetectorElement.cpp

@@ -8,6 +8,8 @@
 
 #include "Acts/Plugins/DD4hep/DD4hepDetectorElement.hpp"
 
+#include "Acts/Plugins/DD4hep/DD4hepGeometryContext.hpp"
+
 #include <utility>
 
 #include <DD4hep/Alignments.h>
@@ -23,3 +25,13 @@ Acts::DD4hepDetectorElement::DD4hepDetectorElement(
           detElement.nominal().worldTransformation(), axes, scalor,
           std::move(material)),
       m_detElement(detElement) {}
+
+const Acts::Transform3& Acts::DD4hepDetectorElement::transform(
+    const GeometryContext& gctx) const {
+  const Acts::DD4hepGeometryContext* dd4hepGtx =
+      gctx.maybeGet<DD4hepGeometryContext>();
+  if (dd4hepGtx != nullptr && dd4hepGtx->isActive()) {
+    return dd4hepGtx->contextualTransform(*this);
+  }
+  return TGeoDetectorElement::m_transform;
+}

Plugins/DD4hep/src/DD4hepGeometryContext.cpp

@@ -0,0 +1,16 @@
+// This file is part of the ACTS project.
+//
+// Copyright (C) 2016 CERN for the benefit of the ACTS project
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+#include "Acts/Plugins/DD4hep/DD4hepDetectorElement.hpp"
+#include "Acts/Plugins/DD4hep/DD4hepGeometryContext.hpp"
+
+const Acts::Transform3& Acts::DD4hepGeometryContext::contextualTransform(
+    const Acts::DD4hepDetectorElement& dElement) const {
+  // Use inactive context as the base transformation state
+  return dElement.transform(DD4hepGeometryContext::inactive());
+}

Plugins/TGeo/include/Acts/Plugins/TGeo/TGeoDetectorElement.hpp

@@ -133,7 +133,7 @@ class TGeoDetectorElement : public Acts::DetectorElementBase {
   /// Return the TGeoNode for back navigation
   const TGeoNode& tgeoNode() const { return *m_detElement; }
 
- private:
+ protected:
   /// Pointer to TGeoNode (not owned)
   const TGeoNode* m_detElement{nullptr};
   /// Transformation of the detector element