feat: Decouple SurfaceAccessor from source link implementations

Core/include/Acts/Detector/Detector.hpp

@@ -102,6 +102,13 @@ class Detector : public std::enable_shared_from_this<Detector> {
   /// @return the map which can be queried with GeometryID for ranges
   const GeometryHierarchyMap<const Surface*>& sensitiveHierarchyMap() const;
 
+  /// Search for a surface with the given identifier.
+  ///
+  /// @param id is the geometry identifier of the surface
+  /// @retval nullptr if no such surface exists
+  /// @retval pointer to the found surface otherwise.
+  const Surface* findSurface(GeometryIdentifier id) const;
+
   /// @brief Visit all reachable surfaces of the detector
   ///
   /// @tparam visitor_t Type of the callable visitor

Core/include/Acts/EventData/detail/TestSourceLink.hpp

@@ -10,6 +10,7 @@
 
 #include "Acts/Definitions/Algebra.hpp"
 #include "Acts/Definitions/TrackParametrization.hpp"
+#include "Acts/Detector/Detector.hpp"
 #include "Acts/EventData/MultiTrajectory.hpp"
 #include "Acts/EventData/SourceLink.hpp"
 #include "Acts/Geometry/GeometryContext.hpp"
@@ -27,6 +28,8 @@
 
 namespace Acts::detail::Test {
 
+struct TestSourceLinkSurfaceAccessor;
+
 /// A minimal source link implementation for testing.
 ///
 /// Instead of storing a reference to a measurement or raw data, the measurement
@@ -35,6 +38,8 @@ namespace Acts::detail::Test {
 /// identifier is stored that can be used to store additional information. How
 /// this is interpreted depends on the specific tests.
 struct TestSourceLink final {
+  using SurfaceAccessor = TestSourceLinkSurfaceAccessor;
+
   GeometryIdentifier m_geometryId{};
   std::size_t sourceId = 0u;
   // use eBoundSize to indicate unused indices
@@ -87,17 +92,30 @@ struct TestSourceLink final {
     return os;
   }
   constexpr std::size_t index() const { return sourceId; }
+};
 
-  struct SurfaceAccessor {
-    const Acts::TrackingGeometry& trackingGeometry;
+struct TestSourceLinkSurfaceAccessor {
+  const TrackingGeometry& geometry;
 
-    const Acts::Surface* operator()(const Acts::SourceLink& sourceLink) const {
-      const auto& testSourceLink = sourceLink.get<TestSourceLink>();
-      return trackingGeometry.findSurface(testSourceLink.m_geometryId);
-    }
-  };
+  const Acts::Surface* operator()(const Acts::SourceLink& sourceLink) const {
+    const auto& testSourceLink = sourceLink.get<TestSourceLink>();
+    return geometry.findSurface(testSourceLink.m_geometryId);
+  }
 };
 
+namespace Experimental {
+
+struct TestSourceLinkSurfaceAccessor {
+  const Acts::Experimental::Detector& geometry;
+
+  const Acts::Surface* operator()(const Acts::SourceLink& sourceLink) const {
+    const auto& testSourceLink = sourceLink.get<TestSourceLink>();
+    return geometry.findSurface(testSourceLink.m_geometryId);
+  }
+};
+
+}  // namespace Experimental
+
 inline std::ostream& operator<<(std::ostream& os,
                                 const TestSourceLink& sourceLink) {
   return sourceLink.print(os);

Core/src/Detector/Detector.cpp

@@ -207,3 +207,8 @@ const Acts::GeometryHierarchyMap<const Acts::Surface*>&
 Acts::Experimental::Detector::sensitiveHierarchyMap() const {
   return m_sensitiveHierarchyMap;
 }
+
+const Acts::Surface* Acts::Experimental::Detector::findSurface(
+    GeometryIdentifier geoID) const {
+  return *m_sensitiveHierarchyMap.find(geoID);
+}

Examples/Framework/include/ActsExamples/EventData/IndexSourceLink.hpp

@@ -8,6 +8,7 @@
 
 #pragma once
 
+#include "Acts/Detector/Detector.hpp"
 #include "Acts/EventData/SourceLink.hpp"
 #include "Acts/Geometry/TrackingGeometry.hpp"
 #include "Acts/Surfaces/Surface.hpp"
@@ -18,6 +19,8 @@
 
 namespace ActsExamples {
 
+struct IndexSourceLinkSurfaceAccessor;
+
 /// A source link that stores just an index.
 ///
 /// This is intentionally kept as barebones as possible. The source link
@@ -29,6 +32,8 @@ namespace ActsExamples {
 /// easily changed without having to also change the source link.
 class IndexSourceLink final {
  public:
+  using SurfaceAccessor = IndexSourceLinkSurfaceAccessor;
+
   /// Construct from geometry identifier and index.
   constexpr IndexSourceLink(Acts::GeometryIdentifier gid, Index idx)
       : m_geometryId(gid), m_index(idx) {}
@@ -46,15 +51,6 @@ class IndexSourceLink final {
 
   Acts::GeometryIdentifier geometryId() const { return m_geometryId; }
 
-  struct SurfaceAccessor {
-    const Acts::TrackingGeometry& trackingGeometry;
-
-    const Acts::Surface* operator()(const Acts::SourceLink& sourceLink) const {
-      const auto& indexSourceLink = sourceLink.get<IndexSourceLink>();
-      return trackingGeometry.findSurface(indexSourceLink.geometryId());
-    }
-  };
-
  private:
   Acts::GeometryIdentifier m_geometryId;
   Index m_index = 0;
@@ -70,6 +66,28 @@ class IndexSourceLink final {
   }
 };
 
+struct IndexSourceLinkSurfaceAccessor {
+  const Acts::TrackingGeometry& geometry;
+
+  const Acts::Surface* operator()(const Acts::SourceLink& sourceLink) const {
+    const auto& indexSourceLink = sourceLink.get<IndexSourceLink>();
+    return geometry.findSurface(indexSourceLink.geometryId());
+  }
+};
+
+namespace Experimental {
+
+struct IndexSourceLinkSurfaceAccessor {
+  const Acts::Experimental::Detector& geometry;
+
+  const Acts::Surface* operator()(const Acts::SourceLink& sourceLink) const {
+    const auto& indexSourceLink = sourceLink.get<IndexSourceLink>();
+    return geometry.findSurface(indexSourceLink.geometryId());
+  }
+};
+
+}  // namespace Experimental
+
 /// Container of index source links.
 ///
 /// Since the source links provide a `.geometryId()` accessor, they can be

Tests/UnitTests/Core/EventData/SourceLinkTests.cpp

@@ -22,6 +22,7 @@ BOOST_AUTO_TEST_SUITE(EventDataSourceLink)
 
 BOOST_AUTO_TEST_CASE(TestSourceLinkCoverage) {
   using Acts::detail::Test::TestSourceLink;
+
   TestSourceLink ts;
   Acts::Vector2 stddev(0.01, 0.1);
   Acts::SquareMatrix2 cov = stddev.cwiseProduct(stddev).asDiagonal();