Task edit document preview component Alfresco

First question:

I want to implement a preview of the document in the form of the task-edit of the workflows... How can I do this? I try to adapt the document-details.xml and document-details.ftl to workflow-details.xml and workflow-details.ftl but not works. I tried to copy the components that have web-preview of the document-details files to workflow-details. Any hint to make this?

I have this in workflow-details.ftl:

<#include "include/alfresco-template.ftl" />
<@templateHeader>
   <@script type="text/javascript" src="${url.context}/res/modules/documentlibrary/doclib-actions.js" group="document-details"/>
   <@link rel="stylesheet" type="text/css" href="${url.context}/res/components/document-details/document-details-panel.css" group="document-details"/>
   <@link rel="stylesheet" type="text/css" href="${url.context}/res/components/workflow/task-edit-header.css" group="workflow-details"/>
   <@templateHtmlEditorAssets />
</@>


<@templateBody>
   <@markup id="alf-hd">
   <div id="alf-hd">
      <@region scope="global" id="share-header" chromeless="true"/>
      <@region id="title" scope="template"/>
      <#if page.url.args.nodeRef??>
         <@region id="path" scope="template"/>
      </#if>
   </div>
   </@>
   <@markup id="bd">
   <div id="bd">
      <div class="share-form">
         <@region id="data-header" scope="page" />
         <div class="yui-gc">
            <div class="yui-u first">
                 <#if (config.scoped['WorkflowDetails']['workflow-details'].getChildValue('display-web-preview') == "true")>
                    <@region id="web-preview" scope="template"/>
                 </#if>
            </div>
         </div>
         <@region id="data-form" scope="page" />
         <@region id="data-actions" scope="page" />
      </div>
   </div>
   </@>
</@>

<@templateFooter>
   <@markup id="alf-ft">
   <div id="alf-ft">
      <@region id="footer" scope="global"/>
      <@region id="data-loader" scope="page" />
   </div>
   </@>
</@>

In workflow-details.xml I add this component:

 <component>
         <region-id>web-preview</region-id>
         <sub-components>
            <sub-component id="default">
               <evaluations>
                  <evaluation>
                     <evaluators>
                        <evaluator type="config.component.evaluator">
                           <params>
                              <element>WorkflowDetails/workflow-details/display-web-preview</element>
                           </params>
                        </evaluator>
                     </evaluators>
                     <url>/components/preview/web-preview</url>
                     <properties>
                        <nodeRef>{nodeRef}</nodeRef>
                        <api>api</api>
                        <proxy>alfresco</proxy>
                        <dependencyGroup>workflow-details</dependencyGroup>
                     </properties>
                  </evaluation>
               </evaluations>
            </sub-component>
         </sub-components>
      </component>

This not shows the web-preview, only creates:

<div id="template_x002e_web-preview_x002e_workflow-details">
<div id="template_x002e_web-preview_x002e_workflow-details_x0023_default"> </div>
</div>

What's my error?

Second question:

In the preview of the Aikau page I get: Warning: unimplemented annotation type: Widget signature in the console of the firebug of the Mozilla Firefox and the document is displayed without the digital signatures... But, for example, if I upload a document with a digital signature, I can see the document with the signature in the page of document-details of the document. The preview of this page is different? How can I implement this preview?

It can be easier to just use the javascript previewer that is integrated in share (pdf.js). If you use directly the javascript library, it shouldn't be difficult to open a preview.

There are examples in the official site of the project: pdf.js

you can use the share webscript to initialise the javascript with the list of urls of the documents attached to the workflow. If the document attached is not a pdf, you will need to use its pdf rendition.