feat: implement contact listeners

tests/destrum_tests.cpp

@@ -20,6 +20,7 @@
 #include <destrum/Physics/JoltPhysicsWorld.h>
 #include <destrum/Components/Physics/SphereCollider.h>
 #include <destrum/Components/Physics/BoxCollider.h>
+#include <destrum/Components/Physics/Collider.h>
 #include <destrum/Components/Animator.h>
 #include <destrum/Components/Physics/Rigidbody.h>
 #include <destrum/Graphics/Material.h>
@@ -483,6 +484,65 @@ namespace {
         check(!AssetReference::fromCacheKey("CharacterMedium.fbx").has_value(),
               "plain cache names must not be treated as file-backed assets");
     }
+
+    class TriggerTracker final : public Component {
+    public:
+        explicit TriggerTracker(GameObject& owner)
+            : Component(owner, "TriggerTracker") {}
+
+        void Update(float) override {}
+        std::string GetTypeName() const override { return "TriggerTracker"; }
+
+        void OnTriggerEnter(GameObject* other) override {
+            ++enterCount;
+            lastOther = other;
+            enterObjectName = other ? other->GetName() : "null";
+        }
+
+        void OnTriggerExit(GameObject* other) override {
+            ++exitCount;
+        }
+
+        int enterCount{0};
+        int exitCount{0};
+        GameObject* lastOther{nullptr};
+        std::string enterObjectName;
+    };
+
+    void testTriggerZone()
+    {
+        Scene& scene = SceneManager::GetInstance().CreateScene("trigger-test");
+
+        // Trigger box at origin (Static rigidbody + BoxCollider as trigger).
+        GameObject* triggerObj = scene.CreateGameObject("TriggerZone");
+        triggerObj->AddComponent<BoxCollider>(glm::vec3{3.0f, 3.0f, 3.0f});
+        triggerObj->GetComponent<BoxCollider>()->SetTrigger(true);
+        auto* triggerRb = triggerObj->AddComponent<Rigidbody>();
+        triggerRb->SetType(RigidbodyType::Static);
+        auto* tracker = triggerObj->AddComponent<TriggerTracker>();
+
+        // Falling sphere above the trigger.
+        GameObject* sphere = scene.CreateGameObject("FallingSphere");
+        sphere->AddComponent<SphereCollider>(0.5f);
+        sphere->AddComponent<Rigidbody>();
+        sphere->GetTransform().SetWorldPosition({0.0f, 8.0f, 0.0f});
+
+        scene.CommitPendingAdditions();
+
+        // Run physics for enough steps that the sphere falls into the trigger.
+        for (int step = 0; step < 120; ++step) {
+            scene.FixedUpdate(1.0f / 60.0f);
+        }
+
+        check(tracker->enterCount >= 1,
+              "falling sphere must trigger OnTriggerEnter at least once");
+        check(tracker->exitCount >= 1,
+              "falling sphere passing through trigger must exit");
+        check(tracker->enterObjectName == "FallingSphere",
+              "OnTriggerEnter must report the correct entering object");
+
+        SceneManager::GetInstance().Destroy();
+    }
 }
 
 int main()
@@ -503,6 +563,7 @@ int main()
     testAnimatorAssetReferences();
     testSimpleColorMaterial();
     testAssetReferenceCacheKeys();
+    testTriggerZone();
     std::cout << "destrum tests passed\n";
     return EXIT_SUCCESS;
 }