proposed solution for remembering scroll position

[Jason Young]

I have a problem where an a4j:outputPanel is larger than its container, so we have scrollbars (using css height & overflow properties). However, when the panel is rerendered, the scroll position is lost.

I initially attempted to fix this by setting the scrollTop attribute in the onComplete handler. However, this produced jumpiness that wouldn't be acceptable to an enduser. So instead, I tried adding it to the updatePagePart handler in the AJAX.js file. Adjusting the scrollTop at this level seems to work much better, since I can't tell visually that it is happening.

Can the maintainers of A4J tell me if this is something that could be accepted into the main CVS tree? I don't care if want to change how I did it, but having this functionality in the library itself would be a great help.

Thanks in advance!

 if ( oldnode ) {
 var oldScrollTop = 0;
 if (oldnode.scrollTop > 0)
 oldScrollTop = oldnode.scrollTop;
 LOG.debug("oldScrollTop = " + oldScrollTop);
 var anchor = oldnode.parentNode ;
 // need to check for firstChild due to opera 8 bug with hasChildNodes
 Sarissa.clearChildNodes(oldnode);
 if(oldnode.outerHTML){
 LOG.debug("Replace content of node by outerHTML()");
 oldnode.outerHTML = new XMLSerializer().serializeToString(newnode);
 if (oldScrollTop > 0) {
 LOG.debug("setting scrollTop = " + oldScrollTop);
 oldnode.scrollTop = oldScrollTop;
 }
 } else {
 var importednode ;
 importednode = window.document.importNode(newnode, true);
 LOG.debug("Replace content of node by replaceChild()");
 anchor.replaceChild(importednode,oldnode);

 if (oldScrollTop > 0) {
 LOG.debug("setting scrollTop = " + oldScrollTop);
 importednode.scrollTop = oldScrollTop;
 }
 }

[Jason Young]

bump

Is this a topic for the developer forum?

[Sergey Smirnov]

post this issue to jira as a request for new feature. Refer to this post.

[Jason Young]

Thanks for the response, Sergey. I will open a request. Do you think this is something that could be slipped into the next point release?

[Jason Young]

http://jira.jboss.com/jira/browse/AJSF-33

[Sergey Smirnov]

not sure about the next release. First, because we have other tasks with higher priority. Second, the similar attempt to scroll the page in the MyFaces had many side effects. So, we have to investigate the possible side effects before add such feature in production release.

[Jason Young]

Wanted to post an update on this issue. I have found a workaround for the scroll issue. Also, the proposed solution I added above does not always work for IE. Sometimes, the node is not ready to have the scroll position set (scrollHeight is still zero), resulting in a script error.

The solution I found is to have a hierarchy of a4j:outputPanel. In my case I need 3 levels. This seems to at least work in IE6, IE7, and FF2. Not sure about other browsers.

<a4j:outputPanel id="panel0" layout="block" style="clear:both; height: 400px; overflow: auto; width:100%;">
<a4j:outputPanel id="panel1" layout="block">
<a4j:outputPanel id="panel2" layout="block">

... content here ...

</a4j:outputPanel>
</a4j:outputPanel>
</a4j:outputPanel>

<a4j:poll id="poller" interval="5000" eventsQueue="pollerQueue" bypassUpdates="true" ajaxSingle="true" action="#{myBean.checkForNewData}" reRender="panel2"/>