postion renderer fixed

        widgetHtml = renderTree(doc.root);

    }

    // Preserve the preview scroll position across reloads (the preview

    // iframe navigates to a fresh document on every refresh, so scroll

    // state has to round-trip through the iframe's own sessionStorage).

    {

        std::string scrollKey = "blogi_preview_scroll_" + sessionid;

        json_object *keyJson = json_object_new_string(scrollKey.c_str());

        std::string keyLiteral = json_object_to_json_string_ext(keyJson, JSON_C_TO_STRING_NOSLASHESCAPE);

        json_object_put(keyJson);

        widgetHtml +=

            "<script>(function(){"

            "var K=" + keyLiteral + ";"

            "try{var y=sessionStorage.getItem(K);"

            "if(y!==null)window.scrollTo(0,parseInt(y,10)||0);}catch(e){}"

            "var save=function(){try{sessionStorage.setItem(K,window.scrollY||window.pageYOffset||0);}catch(e){}};"

            "window.addEventListener('load',function(){"

            "try{var y2=sessionStorage.getItem(K);"

            "if(y2!==null)window.scrollTo(0,parseInt(y2,10)||0);}catch(e){}"

            "});"

            "window.addEventListener('scroll',save,{passive:true});"

            "window.addEventListener('beforeunload',save);"

            "})();</script>";

    }

    json_object *resp = json_object_new_object();

    json_object_object_add(resp, "blogUrl", json_object_new_string(blogUrl.c_str()));

    json_object_object_add(resp, "authid", json_object_new_string(authid.c_str()));