Inject element to left, right, before/after content, ... without layout changes in m1

Question

I am creating an extension that will add dynamic content to different parts of page depends on selection. Admin user can add elements to left sidebar, right sidebar, before/after content, ...

So far I found one way of doing it: Define all 8 positions inside layout file, then check inside module block if user selected this specific position and display content if yes, otherwise skip it.

<default>
   <reference name="right">
     <block type="company/module" name="company_module_right" template="company/module.phtml" />
   </reference>
</default>

<default>
   <reference name="header">
     <block type="company/module" name="company_module_header_before" template="company/module.phtml" before="-" />
   </reference>
</default>
....

This would work fine, but it is not perfect solution because I will need to load the same block and go through the same collection 8 times, each time for each position to check if user selected this section to inject elements into.

I was thinking about using observer:

<controller_action_layout_load_before>
    <observers>
        <inject_content>
            <type>singleton</type>
            <class>company_module/observer</class>
            <method>addBlock</method>
        </inject_content>                   
    </observers>
</controller_action_layout_load_before> 

Observer.php:

public function addBlock(Varien_Event_Observer $observer)
{    
  $layout = Mage::getSingleton('core/layout');
  $collection = Mage::getModel('company_module/blocks')->getCollection(); 
  foreach($collection as $col){
    $content = $layout->getBlock($col->getData('parentBlockName'));
    $newBlock = $layout->createBlock('core/template', $col->getData('injectedBlockName'));
    $newBlock->setTemplate('company_module/blocks.phtml');
    $content->append($newBlock);        
  }                          
}   

But $layout->getBlock('content') or $layout->getBlock('left') or other blocks always return false. I tried also controller_action_layout_load_before, in this way it won't return false but it also won't inject block. Any idea how to make this work?

Answer 1

I found answer in this question.

It can be done by using addHandle method:

if (//if condition) {
    $layout = $observer->getLayout();
    $layout->getUpdate()->addHandle('custom_layout_handle_header');
}elseif(//if condition){
    $layout = $observer->getLayout();
    $layout->getUpdate()->addHandle('custom_layout_handle_right'); 
 }

layout file

<layout>
  <custom_layout_handle_header>
     <reference name="header">
       <block type="core/template" name="header_block" template="template.phtml" />
     </reference>
  </custom_layout_handle_header>
</layout>

<layout>
  <custom_layout_handle_right>
     <reference name="right">
       <block type="core/template" name="right_block" template="template_file.phtml" />
     </reference>
  </custom_layout_handle_right>
</layout>