Feature Proposal: Add a new optional attribute to the META{"parent" ...} variable to limit number of upstream ancestors

Motivation

When a deeply nested Topic is viewed using the Pattern skin [or one of many skins that displays the META{"parent"} variable], the page is often rendered very wide, distorting the rest of the page's layout. The addition of an optional attribute (maxelements) is a small change, and completely backwards-compatible; any current unchanged uses of META{"parent"} will be unaffected.

Description

This change would add an optional attribute to the META{"parent"} variable - "maxelements". Once maxelements ancestors have been prepended to the list, all other ancestors are replaced by "...", thus limiting the length of the displayed list. Because the number of elements to be displayed is set on a per-use basis, developers can decide whether this added functionality is useful in a given context, and furthermore to what extent the context calls for the limiting of the ancestory list length.

-- OrrBernstein - 08 Mar 2005

Impact and Available Solutions

Note: Patch is attached as https://www.twiki.org/p/pub/Codev/MetaParentOptionalLengthLimit/twiki-render-meta-parent-patch.diff. The patch is against the TWikiProductionRelease of 02 Sep 2004 or 01 Sep 2004 (Cairo Release).

Documentation

The topic, TWikiMetaData (#Rendering_Meta_Data), would need to be changed as such:

...

At present support is fairly basic:

...

Examples

One example is putting the ancestory on the WebTopBar, as a easy navigation mechanism if your TWiki has a good amount of hierarchical organization:

<div class="twikiLeft">
<table border="0" cellpadding="0" cellspacing="0">
<tr>
<td width="170"<a href="%WIKILOGOURL%"><img src="%WIKILOGOIMG%" border="0" alt="Home"/></a></td>
<td valign="bottom" align="right"><br/><br/>[[%BASEWEB%.WebHome][Codev]] %META{"parent" nowebhome="on" prefix=" < " suffix="" maxelements="2"}% < <nop>%BASETOPIC%</td>
</tr>
</table>
</div>
<div class="twikiRight twikiSearchBox">
<table border="0" cellpadding="0" cellspacing="0">
<tr>
<td><label for="go">Jump: </label><input type="text" id="go" name="topic" size="16" /></td>
</tr>
</table>
</div>

Implementation

After reading in the new attribute,

...
   my $maxElements = 0;

   if( $args ) {
...
       $maxElements = TWiki::extractNameValuePair( $args, "maxelements" );
   }
...

we simply start counting how many elements we've seen - if we reach one past the max (note that we start counting at 0, so we've past the max when the count == the max specified), we add a "..." and break out of the loop.

...
            my $elementCount = 0;
...
            $elementCount += 1;
            if( $elementCount == $maxElements ) {
               $text = "...$sep$text";
               last;
            } else {
               $text = "[[$pWeb.$pTopic][$pTopic]]$sep$text";
            }
            (this replaces: $text = "[[$pWeb.$pTopic][$pTopic]]$sep$text";)
...

Small change, but the effect on the visual effect of the trail is noticable.

Discussion:

• twiki-render-meta-parent-patch.diff: Unified diff for patching