public PageMarkupRendererImpl(MarkupRenderer markupRendererPipeline,
    PageRenderQueue pageRenderQueue,
    Environment environment,
    Request request) 
{
        // We have to go through some awkward tricks here:
        // - MarkupRenderer and MarkupRendererFilter are PUBLIC
        // - Page, PageMarkupRenderer, PageRenderQueue are PRIVATE
        // - This service is the bridge between public and private
        this.pageRenderQueue = pageRenderQueue;
        this.environment = environment;
        this.markupRendererPipeline = markupRendererPipeline;
        this.request = request;
}

 public  void renderPageMarkup(Page page,
    MarkupWriter writer) 
{
        // Don't clear the environment when rendering a page to a document as we may be doing so when in the middle
        // of another render.
        if (request.getAttribute(InternalConstants.GENERATING_RENDERED_PAGE) == null)
            environment.clear();
        // This is why the PRQ is scope perthread; we tell it what to render here ...
        pageRenderQueue.initializeForCompletePage(page);
        // ... then our statically fixed pipeline is able to (eventually) call into it.
        markupRendererPipeline.renderMarkup(writer);
        if (writer.getDocument().getRootElement() == null)
            throw new RuntimeException(ServicesMessages.noMarkupFromPageRender(page));
}