Cart price calculation on user login is set to zero

Question

I made a module to calculate the price, based on given dimensions. This is working very nice, but when I login as user, the cart price resets to zero.

How do I solve this?

/// edit #1

After some digging, I found out that the vars: $quantity and $dimensionsPrice not working on quote merging. Do you know why? $dimensionPrice is from the custom attribute dimension_price.

/// edit #2

Turns out that when I want to add a product to the cart I have to use $product->getQty(). And when I login (so it merges), I have to use $quote_item->getQty(). Bit strange, but I fixed it with:

  $quantity = ($product->getQty()) ? $product->getQty() : $quote_item->getQty();

Now, I still not getting my attribute 'dimension price'...?

mymodule/etc/config.xml

<?xml version="1.0"?>
<config>
    <modules>
      <Roywulms_Dimensioncalculator>
          <version>0.1.0</version>
      </Roywulms_Dimensioncalculator>
    </modules>
    <global>
    <models>
        <Roywulms_Dimensioncalculator>
            <class>Roywulms_Dimensioncalculator_Model</class>
        </Roywulms_Dimensioncalculator>
    </models>
     <events>
        <sales_quote_add_item>
            <observers>
               <Roywulms_Dimensioncalculator_Model_Observer>
                  <type>singleton</type>
                  <class>Roywulms_Dimensioncalculator_Model_Observer</class>
                  <method>changingPrice</method>
               </Roywulms_Dimensioncalculator_Model_Observer>
           </observers>
        </sales_quote_add_item>
    </events>
    </global>
</config>

mymodule/Model/Observer.php

<?php
class Roywulms_Dimensioncalculator_Model_Observer {
    public function __construct()
   {

   }
    public function changingPrice(Varien_Event_Observer $observer){

        $event = $observer->getEvent();
        $quote_item = $event->getQuoteItem();
        $product = $quote_item->getProduct();
        $quantity = $product->getQty();
        $options = $this->getProductOptions($quote_item);

        if(sizeof($options) > 0)
        {
            foreach($options as $option)
            {
                if($option['option_type'] == 'height')
                    $heightVal =  $option['value'];
                if($option['option_type'] == 'width')
                    $widthVal =  $option['value'];
            }
            $basePrice = $product->getPrice();
            $dimensionsPrice =  $product->getDimensionPrice();

            if(isset($heightVal) && isset($widthVal)){
              $meter = $basePrice + ($widthVal * $heightVal)*$dimensionsPrice;
              $new_price = $meter*$quantity;
              $quote_item->setOriginalCustomPrice($new_price);
            }
        }
     }

      function getProductOptions(&$item)
        {
          $options = array();

          if ($optionIds = $item->getOptionByCode('option_ids')) {
              $options = array();
              foreach (explode(',', $optionIds->getValue()) as $optionId) {
                  if ($option = $item->getProduct()->getOptionById($optionId)) {

                      $quoteItemOption = $item->getOptionByCode('option_' . $option->getId());

                      $group = $option->groupFactory($option->getType())
                          ->setOption($option)
                          ->setQuoteItemOption($quoteItemOption);

                      $options[] = array(
                          'label' => $option->getTitle(),
                          'value' => $group->getFormattedOptionValue($quoteItemOption->getValue()),
                          'print_value' => $group->getPrintableOptionValue($quoteItemOption->getValue()),
                          'price'=> $group->getOptionPrice($quoteItemOption->getValue(),0),
                          'option_id' => $option->getId(),
                          'option_type' => $option->getType(),
                          'custom_view' => $group->isCustomizedView()
                      );
                  }
              }
          }
          if ($addOptions = $item->getOptionByCode('additional_options')) {
              $options = array_merge($options, unserialize($addOptions->getValue()));
          }
          return $options;
        }
}
?>

Answer 1

Found the solution. Not the best I think, so if you know a better approach, please tell me.

Turns out I had two problems:

1: Quantity was not loaded on quote merge (happens when a user is logging in)

Replaced

 $quantity = $product->getQty();

with

$quantity = ($product->getQty()) ? $product->getQty() : $quote_item->getQty();

2: Attribute was not loaded on quote merge.

Replaced

$dimensionsPrice =  $product->getDimensionPrice();

with

$dimensionsPrice =  Mage::getModel('catalog/product')->load($product->getId())->getData('dimension_price');