sceneviewstuff.cs

    static void DoScenePicking(SceneView sceneView)
    {
        var e = Event.current;
        if (e.alt || e.control || e.command)
            return;

        var controlID = GUIUtility.GetControlID(FocusType.Passive);
        switch (e.GetTypeForControl(controlID))
        {
            case EventType.Layout:
            {
                var selectedGameObject = PickSceneViewObject(sceneView.camera, e.mousePosition);
                if (selectedGameObject)
                    HandleUtility.AddDefaultControl(controlID);
                break;
            }
            case EventType.MouseDown:
            {
                if (e.button == 0 && HandleUtility.nearestControl == controlID && GUIUtility.hotControl == 0)
                    GUIUtility.hotControl = controlID;
                break;
            }
            case EventType.MouseUp:
            {
                if (e.button == 0 && GUIUtility.hotControl == controlID)
                {
                    GUIUtility.hotControl = 0;
                    Event.current.Use();

                    var selectedGameObject = PickSceneViewObject(sceneView.camera, e.mousePosition);
                    Selection.activeGameObject = selectedGameObject;
                }
                break;
            }
        }
    }