Convert reusable layout classes to BEM standards

hmm true, but I'm think we should do this anyway because #2471791: Improve the CSS layout framework for Drupal's admin interface need bikeshedding and might not happen for a while.

Yep

@martins.kajins We also have to go through the markup to to make sure the classes there match the CSS.

I found one instance of the layout-column.quarter:

/Library/WebServer/Documents/core/modules/help/src/Controller/HelpController.php:
   78        '#type' => 'container',
   79        'links' => array('#theme' => 'item_list'),
   80:       '#attributes' => array('class' => array('layout-column', 'quarter')),
   81      );
   82      $output = array(

Ah you know what I just realised? We have to include both the layout-column class and the layout-column--variant classes.

+++ b/core/modules/help/src/Controller/HelpController.php
@@ -77,7 +77,7 @@ protected function helpLinksAsList() {
-      '#attributes' => array('class' => array('layout-column', 'quarter')),
+      '#attributes' => array('class' => array('layout-column--quarter')),

As an example this would be 'class' => array('layout-column','layout-column--quarter')

+++ b/core/modules/config_translation/templates/config_translation_manage_form_element.html.twig
@@ -15,10 +15,10 @@
-  <div class="layout-column half translation-set__source">
+  <div class="layout-column--half translation-set__source">
...
-  <div class="layout-column half translation-set__translated">
+  <div class="layout-column--half translation-set__translated">

+++ b/core/modules/system/templates/admin-page.html.twig
@@ -17,7 +17,7 @@
-    <div class="layout-column half">
+    <div class="layout-column--half">

+++ b/core/modules/update/templates/update-version.html.twig
@@ -19,12 +19,12 @@
+    <div class="project-update__version-title layout-column--quarter">{{ title }}</div>
+    <div class="project-update__version-details layout-column--quarter">
...
+    <div class="layout-column--half">

Thanks, we still need to do this for these instances

Ghost fail

Thanks Alex, here's the problem. We are missing the layout-column class:

Thanks, this looks correct: