CKEditor Toolbar - various button issues when the language is RTL

I tested this, with beta 15 versus HEAD plus the patch (https://simplytest.me/project/drupal/8.x?patch[]=https://www.drupal.org/...). Unfortunately, I don't see any difference before vs after.

1. +++ b/core/modules/ckeditor/ckeditor.admin.inc
   @@ -70,7 +70,7 @@ function template_preprocess_ckeditor_settings_toolbar(&$variables) {
   -    elseif (isset($button['image'])) {
   +    elseif (isset($button['image' . $rtl]) ) {
   
   +++ b/core/modules/ckeditor/src/Plugin/CKEditorPlugin/DrupalImage.php
   @@ -53,10 +54,12 @@ public function getConfig(Editor $editor) {
      public function getButtons() {
   +    $language_interface = \Drupal::languageManager()->getCurrentLanguage();
   +    $rtl = $language_interface->getDirection() === LanguageInterface::DIRECTION_RTL ? '_rtl' : '';
        return array(
          'DrupalImage' => array(
            'label' => t('Image'),
   -        'image' => drupal_get_path('module', 'ckeditor') . '/js/plugins/drupalimage/image.png',
   +        'image' . $rtl => drupal_get_path('module', 'ckeditor') . '/js/plugins/drupalimage/image.png',
          ),
   
   +++ b/core/modules/ckeditor/src/Plugin/CKEditorPlugin/DrupalLink.php
   @@ -52,14 +53,16 @@ public function getConfig(Editor $editor) {
   +    $language_interface = \Drupal::languageManager()->getCurrentLanguage();
   +    $rtl = $language_interface->getDirection() === LanguageInterface::DIRECTION_RTL ? '_rtl' : '';
        return array(
          'DrupalLink' => array(
            'label' => t('Link'),
   -        'image' => $path . '/link.png',
   +        'image' . $rtl => $path . '/link.png',
          ),
          'DrupalUnlink' => array(
            'label' => t('Unlink'),
   -        'image' => $path . '/unlink.png',
   +        'image' . $rtl => $path . '/unlink.png',
   
   +++ b/core/modules/ckeditor/src/Plugin/CKEditorPlugin/Internal.php
   @@ -146,48 +146,59 @@ public function getButtons() {
   +        'image_alternative_rtl' => $button('bold', 'rtl'),
   ...
   +        'image_alternative_rtl' => $button('italic', 'rtl'),
   

   I don't see why these changes are necessary?

   AFAICT you can delete all these changes and still end up with exactly the same HTML?

   In other words: I don't think these changes are necessary to fix the problem?

2. +++ b/core/modules/ckeditor/css/ckeditor.admin.css
   @@ -182,11 +182,16 @@
   +.ckeditor-buttons li .cke_ltr {
   +    direction: ltr;
   +}
   +.ckeditor-buttons li .cke_rtl {
   +    direction: rtl;
   +}
   

   Nit: Indented with 4 instead of 2 spaces.

3. +++ b/core/modules/ckeditor/src/Tests/CKEditorToolbarButtonTest.php
   @@ -0,0 +1,81 @@
   + * @package Drupal\ckeditor\Tests
   

   You can delete this line.

4. +++ b/core/modules/ckeditor/src/Tests/CKEditorToolbarButtonTest.php
   @@ -0,0 +1,81 @@
   +class CKEditorToolbarButtonTest extends WebTestBase {
   +  /**
   

   Nit: needs a \n in between.

5. +++ b/core/modules/ckeditor/src/Tests/CKEditorToolbarButtonTest.php
   @@ -0,0 +1,81 @@
   +  }
   +}
   

   Nit: needs a \n in between.

#7 As my screenshots show, I tested this on simplytest.me, so I don't see how browser caches could ever cause any problems :( Did you perhaps forget to include a few small things in the patch, that you do have locally? Otherwise, I really have no idea at all how we could be seeing so vastly different things! Note I tested in Chrome.

The theme_image is searching for a button with key "image_rtl" if the direction is RTL.

Oh, LOL, how did I miss that!? I think this would be a much simpler solution then:

-    elseif (isset($button['image'])) {
+    elseif (isset($button['image' . $rtl]) || isset($button['image'])) {
       $value = array(
         '#theme' => 'image',
-        '#uri' => $button['image' . $rtl],
+        '#uri' => isset($button['image' . $rtl]) ? $button['image' . $rtl] : $button['image'],

In other words: the buttons that don't need LTR/RTL variants, can just use the much simpler $button['image']. Those that do have LTR and RTL variants can provide both $button['image_ltr'] and $button['image_rtl'].

Confirmed now that it works perfectly :)

So, all that is left, is addressing the nits in points 2–5 in #5, and the simpler solution in #7.

Great work, @aneek! Thanks for your patience!

Committed ae70ed6 and pushed to 8.0.x. Thanks!