Conditionally add CSS file in layout XML (local.xml)

Question

I need to add a CSS file in local.xml based on some custom variables. I have 5 CSS files but each time only one needs to be loaded.

I only know how to check if a single variable is set in the config. If config returns TRUE, the CSS file will be loaded in the frontend:

<action method="addItem" ifconfig="my_module/settings/variable"><type>skin_css</type><name>css/a.css</name><params/></action>

So for now I must put my code in head.phtml in app\design\frontend\my_theme\default\template\page\html\ to load CSS files like this:

<?php
  $my_var = Mage::helper('my_module/my_helper')->getFileName();
?>
<link href="<?php echo $my_var; ?>.css" rel="stylesheet" type="text/css" media="all" />

But it has a drawback: my CSS files will not be merged by Magento's CSS/JS merge function.

So, is there any way to do the same but inside local.xml? Is there any way to call a method from the helper which would return the name of the CSS file which should be loaded (based on some calculations inside that helper)?

SOLUTION CANDIDATE :)

I tried something similar to what Alan Storm described in this thread: https://stackoverflow.com/a/5601579/1647291

I tried this in my local.xml file:

<action method="addItem">
    <type>skin_css</type>
    <name helper="my_module/my_helper/getFileName" />
    <params/>
</action>

Helper method getFileName() returns file name a.css. But Magento searches for that CSS file inside "base" theme, not in the current theme. Magento loads CSS file with this path:

http://example.com/skin/frontend/base/default/a.css

So my file name is prefixed with example.com/skin/frontend/base/default/. But the correct path should be:

http://example.com/skin/frontend/my_theme/default/a.css

Does anyone know how to achieve this?

Answer 1

Bottom line: you need to have a value calculated by PHP, therefore the approach of using a helper is appropriate. I think it makes sense to use the addCss convenience method rather than addItem a it's a little cleaner and should work fine for your needs:

<{handle}>
    <action block="head" method="addCss">
        <stylesheet helper="my_module/my_helper/getFileName" />
    </action>
</{handle}>

Your helper seems to be calculating the path to the CSS files using the design model, but this will be done again by the page/html_head block. Change your helper to simply return the file paths relative to the theme (i.e. not using the design model) and your problem is solved.

Answer 2

I just wanted to let you know that the solution described in my question actually works. I just did a stupid mistake. This code was added to local.xml in my theme:

<action method="addItem">
    <type>skin_css</type>
    <name helper="my_module/my_helper/getFileName" />
    <params/>
</action>

Helper method getFileName() returns file name a.css. But my CSS file wasn't in the correct directory:

http://example.com/skin/frontend/my_theme/default/a.css

so Magento tried to find that file inside "base" theme, not in the current theme:

http://example.com/skin/frontend/base/default/a.css

So if file is in the correct directory, all will work as expected. The code posted by @benmarks will also work:

<action method="addCss">
    <stylesheet helper="my_module/my_helper/getFileName" />
</action>