feat: add scene view editor camera controls

tests/editor/test_scene_viewport_camera_controller.cpp

@@ -0,0 +1,75 @@
+#include <gtest/gtest.h>
+
+#include "Viewport/SceneViewportCameraController.h"
+
+#include <XCEngine/Components/GameObject.h>
+
+#include <cmath>
+
+namespace {
+
+bool NearlyEqual(float lhs, float rhs, float epsilon = 1e-4f) {
+    return std::abs(lhs - rhs) <= epsilon;
+}
+
+bool NearlyEqual(const XCEngine::Math::Vector3& lhs, const XCEngine::Math::Vector3& rhs, float epsilon = 1e-4f) {
+    return NearlyEqual(lhs.x, rhs.x, epsilon) &&
+           NearlyEqual(lhs.y, rhs.y, epsilon) &&
+           NearlyEqual(lhs.z, rhs.z, epsilon);
+}
+
+} // namespace
+
+using XCEngine::Components::GameObject;
+using XCEngine::Editor::SceneViewportCameraController;
+using XCEngine::Editor::SceneViewportCameraInputState;
+using XCEngine::Math::Vector3;
+
+TEST(SceneViewportCameraController_Test, ApplyToMatchesComputedPositionAndForward) {
+    SceneViewportCameraController controller;
+    controller.Reset();
+    controller.Focus(Vector3(2.0f, 1.0f, -3.0f));
+
+    GameObject cameraObject("EditorCamera");
+    controller.ApplyTo(*cameraObject.GetTransform());
+
+    EXPECT_TRUE(NearlyEqual(cameraObject.GetTransform()->GetPosition(), controller.GetPosition()));
+    const Vector3 localFocus = cameraObject.GetTransform()->InverseTransformPoint(controller.GetFocalPoint());
+    EXPECT_GT(localFocus.z, 0.0f);
+}
+
+TEST(SceneViewportCameraController_Test, ApplyInputUpdatesOrbitPanAndZoomState) {
+    SceneViewportCameraController controller;
+    controller.Reset();
+
+    const float initialDistance = controller.GetDistance();
+    const float initialYaw = controller.GetYawDegrees();
+    const float initialPitch = controller.GetPitchDegrees();
+    const Vector3 initialFocus = controller.GetFocalPoint();
+
+    SceneViewportCameraInputState input = {};
+    input.viewportHeight = 720.0f;
+    input.zoomDelta = 1.0f;
+    input.orbitDeltaX = 20.0f;
+    input.orbitDeltaY = -15.0f;
+    input.panDeltaX = 16.0f;
+    input.panDeltaY = -10.0f;
+    controller.ApplyInput(input);
+
+    EXPECT_LT(controller.GetDistance(), initialDistance);
+    EXPECT_NE(controller.GetYawDegrees(), initialYaw);
+    EXPECT_NE(controller.GetPitchDegrees(), initialPitch);
+    EXPECT_FALSE(NearlyEqual(controller.GetFocalPoint(), initialFocus));
+}
+
+TEST(SceneViewportCameraController_Test, FocusMovesPivotWithoutChangingDistance) {
+    SceneViewportCameraController controller;
+    controller.Reset();
+
+    const float initialDistance = controller.GetDistance();
+    const Vector3 target(5.0f, -2.0f, 7.5f);
+    controller.Focus(target);
+
+    EXPECT_TRUE(NearlyEqual(controller.GetFocalPoint(), target));
+    EXPECT_FLOAT_EQ(controller.GetDistance(), initialDistance);
+}