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I've created several block plugins each with their own block form. My goal is to make it so you can select what template to use based on a field in the blockForm. I understand that I can change a block template within the build function by specifying the '#theme' but that refers to the content. I want to change block.html.twig template being used that surrounds the content. I also understand that I can specify the block template by using the naming scheme like block--block-name.html.twig but I want to be able to select the template within a preprocess function. Below is my attempt.

In mytheme.theme I have

function mytheme_theme($existing,$type,$theme,$path){
    return [
        'wide_grid_block' => [
            'variables' => [
                'test' => 'Test default value',
            ],
        ]
    ];
}

function mytheme_preprocess_block(&$vars){
      $vars['#theme'] = 'wide_grid_block';
}

and in templates/block/wide-grid-block.html.twig I have

Testing: {{ test }}

I assumed the what should occur is that every block should use the wide-grid-block.html.twig file. But they're all still using block.html.twig.

How do I specify a custom block template in a preprocess function?

UPDATE: I've also tried using a theme_suggestions_block_alter hook but I get a white screen when attempting to do so

function alltechcom2017_theme_suggestions_block_alter(array &$suggestions, array $variables) {
$suggestions[0]= 'wide_grid_block';
}

And I've tried with and without the [0]

UPDATE 2: I've managed to add to the suggestions by using

$suggestions[] = 'wide_grid_block';

The issue I had before with the white screen was because the file was in the wrong location. So I know drupal can see it, I just need it to be the most desired one in the list of possible templates.

In the debug info I see

<!-- FILE NAME SUGGESTIONS:
   * block--product-selector.html.twig
   * wide-grid-block.html.twig
   x block.html.twig
-->

And I have a block.html.twig and a wide-grid-block.html.twig. Why is it using block.html.twig instead? It's acting as if my file doesn't exist. I looked at this https://sqndr.github.io/d8-theming-guide/theme-hooks-and-theme-hook-suggestions/theme-hook-suggestions.html and it appeared like I was on the right track.

UPDATE 3: I've added

function mytheme_theme($existing,$type,$theme,$path){
    return [
        'wide_grid_block' => [
            'path' => drupal_get_path('theme','mytheme').'/templates',
            'template' => 'wide_grid_block',
        ],
    ];
}

but still no luck

  • I'm afraid, as you already understand the naming schema, you have to use it. – 4k4 Nov 1 '17 at 21:47
  • There's no way to overwrite that? I need individual blocks to change on a case by case basis. – Matt Nov 1 '17 at 21:52
  • Also I already have it to the point where it's appearing in the file name suggestions. – Matt Nov 1 '17 at 21:59
  • Add to the suggestions block__wide_grid. – 4k4 Nov 1 '17 at 22:16
  • added $suggestions[] = 'block__wide_grid'; and made a block--wide-grid.html.twig file in the templates folder but still no luck. – Matt Nov 1 '17 at 22:26
1

I managed to get it working by using

function mytheme_theme($existing,$type,$theme,$path){
        return [
                'wide_grid_block' => [
                        'path' => drupal_get_path('theme','mytheme').'/templates',
                        'template' => 'wide-grid-block',
        'render element' => 'elements',
        'preprocess functions' => ['template_preprocess','template_preprocess_block','comment_preprocess_block','mytheme_preprocess_block'],
                ],
        ];
}

function mytheme_theme_suggestions_block_alter(array &$suggestions, array $variables) {
if($variables['elements']['#configuration']['id'] == 'page_title' || $variables['elements']['#configuration']['id'] == 'product_selector'){
        $suggestions[] = 'wide_grid_block';
}
  • 1
    With the name suggestion block__wide-grid you wouldn't need to redefine the block hook in hook_theme(). – 4k4 Nov 2 '17 at 7:15
  • I made an attempt using that format but still had issues. – Matt Nov 2 '17 at 13:44
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I just ran into a very similar issue, where theme suggestions were displaying my custom block template, and the template was present in my theme, but wasn't being used.

<!-- FILE NAME SUGGESTIONS:
   * block--my-custom-template.html.twig
   * block--views-block.html.twig
   x block.html.twig
-->

In my case, I wanted to add a template suggestion based on the tag (my-custom-template) of the view that the block is displaying:

function mytheme_theme_suggestions_block_alter(array &$suggestions, array $variables) {
  // Add Views tag suggestions for block templates
  if ($variables['elements']['#base_plugin_id'] == 'views_block') {
    $view = View::load($variables['elements']['content']['#view_id']);
    $suggestions[] = 'block__' . str_replace('-', '_', $view->get('tag'));
  }
}

Without the str_replace, the $suggestion is 'block__my-custom-template' when it needs to be 'block__my_custom_template' in order for the template to be found and called correctly.

I know it doesn't 100% match the original issue, but I wanted to share for others and for me when I come searching for this again in a year!

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