[xsl] rendering a treeview *hairy problem*

["Mattias Konradsson" <preacher at fragzone dot se>]

weee, this problem has been on my mind the last couple of days... So roll up
your sleeves and get your gray ones going, hopefully they work better than
mine :)

I have an forum with xml structure something like this

<forum>

<thread>
    <post  postID="1" Subject="First Post">
        <post  postID="2" Subject="Reply to first Post"/>
        <post  postID="3" Subject="Second Reply to first Post">
            <post  postID="4" Subject="First Reply to Second Reply to first
Post"/>
        </post>
    </post>
    <post  postID="5" Subject="Second Post"/>
</thread>
<thread>
...
</thread>
</forum>

and I want to make an xslt stylesheet that outputs a graphical hierarchial
tree based on this, this is what I got sofar

 <xsl:template match="/">
     <xsl:apply-templates/>
 </xsl:template>

 <xsl:template match="forum">
      <div>
           <xsl:for-each select="thread">
                <xsl:apply-templates />
           </xsl:for-each>
      </div>
 </xsl:template>


 <xsl:template match="post">
   <div style="padding-left:12px">
       <xsl:choose>
             <xsl:when test="position() = last()">
               <img align="middle" src="/community/images/thread.gif"
alt="" border="0"/>
         </xsl:when>
     <xsl:otherwise >
       <img align="middle" src="/community/images/branch.gif"  alt=""
border="0"/>
     </xsl:otherwise>
    </xsl:choose>


   <xsl:value-of select="@subject" /> &#160; <xsl:value-of
select="@nickname" />

   <xsl:if test="position() = last()">last</xsl:if>
   <xsl:value-of  select="count(child::post)"/>

           <xsl:apply-templates />
       </div>
 </xsl:template>

branch.gif is a a image where the the tree branches but has more nodes after
it and thread.gif is a L-shaped image for the last node in a branch . This
is what's produced (here we go with the ascii)

I- First Post
    L Reply to First Post
    L  Second Reply to First Post
        L First Reply to Second Reply to first post
L  Second Post

Sofar so good, the padding takes care of the indenting and we check to see
if a node is last to select image. The *problem is that there should be
Lines connecting the First and Second Post and any Siblings (if there were
any) So I want it to look like this:

I- First Post
I   L Reply to First Post
I   L Second Reply to First Post
I   I     L First Reply to Second Reply to first post
I   L  Third Reply to first post
L  Second Post

But I haven't been able to figure out a good solution.. the current solution
is recursive but for this to work you'd have to keep track on which siblings
line graphics should be before replies. Anyway, I hope I've explained it
well, if anyone can solve this hairy problem I'd be forever grateful :)

Best Regards
---
Mattias Konradsson






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