How to remove CSS files if the page being rendered is a front page in a theme?

Question

I want to remove default Drupal CSS files if it is a front page in Drupal 7 theme.

Following is the code (got from http://www.grahamgilchrist.com/blog/25) that I am trying to put in the template.php for barktik1 theme. How do I check if rendering page is a front page or not? Only $css variable is passed as an argument to the theme_css_alter() function while for other process functions $variables is passed from which it is easy to determine if it is a front page or not.

function bartik1_css_alter(&$css) { 

//do something to check if it is a front page
if ($is_front){
    //make a list of module css to remove 
    $css_to_remove = array(); 
    $css_to_remove[] = drupal_get_path('module','system').'/system.base.css'; 
    $css_to_remove[] = drupal_get_path('module','system').'/system.menus.css'; 

    // now we can remove the contribs from the array 
    foreach ($css_to_remove as $index => $css_file) { 
      unset($css[$css_file]); 
    } 
    }
} 

Thanks!

Answer 1

The function you're looking for is drupal_is_front_page().

Answer 2

In both Drupal 7 and 8 you have hook_css_alter for altering CSS files before output on the page.

If you want to remove some default css file from your Drupal 7 home page you can go with:

function YOUR_THEME_css_alter(&$css) {
  if (drupal_is_front_page() == TRUE  )  {
    unset($css['/'.drupal_get_path('theme', 'YOUR_THEME').'/css/removeme.css'] );
  }
}

Answer 3

To remove CSS files from a module and theme on a Drupal 8 page, you can follow these steps:

Remove single file

function YOUR_THEME_css_alter(&$css) {
    // Remove CSS files from modules.

  // Example: Remove 'defaults.css' from the 'system' module using the service method.
     $system_module_path = \Drupal::service('extension.list.module')->getPath('system') . '/defaults.css';
     unset($css[$system_module_path]);

// Example: Remove custom module CSS file.
    unset($css['modules/custom/ms_ajax_form_example/css/ms_ajax_form_example.css']);

// Example: Remove contributed module CSS file.
    unset($css['modules/contrib/module-machine-name/css/example.theme.css']);

// Remove CSS files from themes.

// Example: Remove 'align.module.css' from the 'stable' theme using the service method.
    $theme_path = \Drupal::service('extension.list.theme')->getPath('stable') . '/css/system/components/align.module.css';
    unset($css[$theme_path]);

// Example: Remove a custom theme's CSS file.
    unset($css['themes/custom/theme-machine-name/assets/css/jquery-ui.min.css']);
}

Remove all CSS files that belong to the stable theme

function YOUR_THEME_css_alter(&$css) {
    // Get the path to the 'stable' theme.
    $theme_path = \Drupal::service('extension.list.theme')->getPath('stable');

    // Iterate through the CSS array and remove any files that belong to the 'stable' theme.
    foreach ($css as $path => $value) {
        if (strpos($path, $theme_path) === 0) {
            unset($css[$path]);
        }
    }
}