private void OnEnable()
        {
            Rect subPos = GetSubWindowArea();

            if (m_AssetFolderTab == null)
            {
                m_AssetFolderTab = new AssetFolderTab();
            }
            m_AssetFolderTab.OnEnable(subPos, this);
            if (m_ManageTab == null)
            {
                m_ManageTab = new AssetBundleManageTab();
            }
            m_ManageTab.OnEnable(subPos, this);
            if (m_BuildTab == null)
            {
                m_BuildTab = new AssetBundleBuildTab();
            }
            m_BuildTab.OnEnable(subPos, this);
            if (m_InspectTab == null)
            {
                m_InspectTab = new AssetBundleInspectTab();
            }
            m_InspectTab.OnEnable(subPos, this);

            m_RefreshTexture = EditorGUIUtility.FindTexture("Refresh");


            //determine if we are "multi source" or not...
            multiDataSource = false;
            List <System.Type> types = AssetBundleDataSource.ABDataSourceProviderUtility.CustomABDataSourceTypes;

            if (types.Count > 1)
            {
                multiDataSource = true;
            }
        }