Allow to alter the build of a Pattern Layout

Provided MR.

Hi Tim,

Thanks for your proposal.

So, the idea is to alter component configuration in the just before we build the renderable:

  public function build(array $regions) {
    $configuration = $this->getConfiguration();
    ...
    $this->moduleHandler->alter('ui_patterns_layouts_display', $configuration, $this, $regions);

    return [
      '#type' => 'pattern',
      '#id' => $this->getPluginDefinition()->get('additional')['pattern'],
      '#fields' => $fields,
      '#variant' => $configuration['pattern']['variant'],
    ] + $this->elementInfo->getInfo('pattern');
  }

However, the configuration is only used for the variant after that. This is your need. But, it doesn't fit with the hook naming. We need a configuration alter hook doing more. Or we need a variant alterer doing the same. And I am afraid the later one is to specific.

What do you think?

Also, we need to be sure that this mechanism can be done also in UI Patterns 2.x and done in the same way with the 5 plugin types natively supported by UI Patterns 2 (layout, block field formatters, view style & view row) and can also be used/implemented in contrib space (DS field, field group formatter...)

To not be limited to variant modification while altering $configuration, we can alter the renderable instead.

  public function build(array $regions) {
    ...
    $build = [ 
      '#type' => 'pattern',
      '#id' => $this->getPluginDefinition()->get('additional')['pattern'],
      '#fields' => $fields,
      '#variant' => $configuration['pattern']['variant'],
    ] + $this->elementInfo->getInfo('pattern');
    $build = $this->moduleHandler->alter('ui_patterns_layouts_display', $build);
    return $build;
  }

So, why not using a preprocess hook (with the "layout" #context) instead?

Because there are 2 issues:

• currently, we have a preprocess hook for each pattern and no preprocess hook for all patterns
• pattern preprocess hook are forbidden by SDC API, so will be removed in UI Patterns 2.x. And there are no #context equivalent in UI Patterns 2.x

Another solution will be a hook_element_info_alter with a "#pre_render" (without using #context):

• works for all patterns
• will still work with UI Patterns 2 (after small changes)

function hook_element_info_alter(array &$types) {
  if (isset($types['pattern'])) {
    array_unshift($types['pattern']['#pre_render'], 'my_callback');
  }
}

So, you may not need to add a specific hook to achieve your goal.

Hey Pierre, much appreciated the time you put into this.
After our call, I went a different route that you suggested me.

For anyone else I've used a hook_preprocess_<PATTERN_ID> to alter the variant.
You can always ping me if you need more info.

tim-diels → closed merge request !85