We are investigating / debugging this. Must be possible!!
While reading this as a reference: Setting variables, we came up with the following:
1: set data=> Custom Layout Update in category (none working, so that's whye so many calls: WIP)
<reference name="content">
<action method="setAttributeFilterName"><value>shirt_size</value></action>
<action method="setAttributeFilterValue"><value>1</value></action>
</reference>
<reference name="product_list">
<action method="setAttributeFilterName"><value>shirt_size</value></action>
<action method="setAttributeFilterValue"><value>2</value></action>
</reference>
<reference name="left">
<action method="setAttributeFilterName"><value>shirt_size</value></action>
<action method="setAttributeFilterValue"><value>3</value></action>
</reference>
<action method="setAttributeFilterName"><value>shirt_size</value></action>
<action method="setAttributeFilterValue"><value>4</value></action>
<catalog_category_view>
<reference name="product_list">
<action method="setAttributeFilterName"><value>shirt_size</value></action>
<action method="setAttributeFilterValue"><value>5</value></action>
</reference>
</catalog_category_view>
<catalog_category_layered>
<reference name="product_list">
<action method="setAttributeFilterName"><value>shirt_size</value></action>
<action method="setAttributeFilterValue"><value>6</value></action>
</reference>
</catalog_category_layered>
2: collection get data=> Influence category collection set-up and picking up the value again as a filter
$f = $this->getData('attribute_filter_name');
$v = $this->getData('attribute_filter_value');
Mage::log('1: '.$f.'-'.$v,Zend_Log::DEBUG,'debug.log',true);
Mage::log('1: '.$this->getAttributeFilterName().' - '.$this->getAttributeFilterValue(),Zend_Log::DEBUG,'debug.log',true);
if (false) {
$collection->addAttributeToFilter($this->getAttributeFilterName(), $this->getAttributeFilterValue());
}
3: Conclustion=> Not working yet, any help appreciated