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Subject RE: [tree2] Node Expansion & Dynamic Data
Date Mon, 01 Aug 2005 22:39:34 GMT
That's a possibility.

We've gotten our "lazy load" to work as follows (which admittedly is
sub-optimal, since it doesn't use the navigation icon features built
into the component):

<x:tree2 id="serverTree" value="#{treeBacker.treeData}" var="node"
		clientSideToggle="false" showNav="false">
	<f:facet name="module">
		<h:panelGroup style="font-size: 10">
			<h:commandLink immediate="true"
rendered="#{t.nodeExpanded && !t.node.leaf}" border="0"/>
rendered="#{!t.nodeExpanded && !t.node.leaf}" border="0"/>
			<h:graphicImage value="/images/ibar.gif"
rendered="#{t.node.leaf}" border="0"/>
value="/images/reference_modules.gif" border="0"/>
			<h:outputLink value="#" style="font-family:
arial; color: blue" onclick="alert(#{})">
				<h:outputText value="#{}"/>

The idea that we've been going with is that, as long as we can catch the
expand/collapse event, we're happy.  And the above JSF code does cause
our action listener to catch the event.  Our action listener then
bubbles up the component parent hierarchy until it hits something of
type HtmlTree, at which point it can access the Node and test whether it
is expanded, whether the children have already been fetched, etc.  If
the children have not already been fetched, our listener calls the back
end to fetch the children, then addes them to the list, and returns.
It's working pretty well so far.

The only problem we've been running into with the current component is
capturing the expand/collapse event when showNav="true" and we're not
using our own navigation icons.  I'm not sure whether this can be
addressed using the current architecture or not.

- Brendan
As promised I'd like to kick off a mini tree2 summit where we can
discuss some of the ideas that are being kicked around.  Yesterday I
closed out some of the easier tree2 related issues in JIRA.  There are
a few remaining which I'd like to address now.  Most of the
outstanding bugs can be addressed once we resolve a few key issues.

One possible change to tree2 that we might want to consider is making
TreeModel an interface and moving the code in the current TreeModel
class to a new DefaultTreeModel class.  The idea would be that users
could supply their own TreeModel using something like <x:tree2
model=#{MyModel} ...> If no model was specified, the DefaultTreeModel
could be used (basically what you have now.)

This might help users who want to specify their data dynamically.
Instead of requiring that the user have all of the data loaded at once
in a node hierarchy, you could implement the getNode() methods, etc.
in any manner that you wanted.  Of course, this would only really
apply to server side toggle (sst).  Client side toggle (cst) might be
possible with Ajax but lets not go down that road just yet :-)

I don't have a current need for this type of feature so those of you
looking to have dynamic trees in this manner should comment on whether
or not this change would be helpful.  Also, my thinking is that we
still require the node data to implement the TreeNode interface.  Its
just that your custom model can wrap the data on the fly as needed
(instead of doing this for all of your data at once.)

There could be another possible impact on adding a TreeModel interace.
 We could add methods for determining the expand/collapse state of
nodes.  I haven't thought this through completely but the thinking was
that TreeModel (and DefaultTreeModel) would have isNodeExpanded() and
isNodeSelected() methods.

Mathias Werlitz has also suggested that UITreeData could extend
UIData.  The code behind the current UITreeData is heavily influenced
by UIData.  It deals with many of the same complex challenges (like
iterrating over the data when encoding and decoding.)  My thinking on
this is that we leave UITreeData as extending UIComponentBase but that
we fine tune it to deal with the use case of containing other
components that render their own children.

So those are some thoughts to get us started.


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