Magento - Add Button to Sales Order View Page (Observer/Event)

Question

I\'m trying to add a custom printing button (like print invoice) on the Sales Order View page (Sales > Orders > Order #... view).

I\'ve do

Answer 1

I solved it a little bit after I posted. The solution for me was the following:

// Order View Page button
        if(get_class($block) =='Mage_Adminhtml_Block_Sales_Order_View'
            && $block->getRequest()->getControllerName() == 'sales_order')
        {
            $block->addButton('test_print', array(
                'label'     => 'Test',
                'onclick'   => 'setLocation(\'' . $block->getUrl('html/sales_order/print') . '\')',
                'class'     => 'go'
            ));
        }