[TASK] Better behaviour for “Unused elements” after a drag & drop

The unused elements in the page module have a specific styling
(orange heading). When the items are drag&drop'ed into an active
colPos, they previously kept their unused styling.

This change gives the "Unused elements" a global warning background
and removes the warning style from the content items so that they don't
stay orange after a drag and drop in a real colPos.

Resolves: #95230
Releases: master
Change-Id: Idaa323166ec2c8f62b6f0fe747e7965910dbd4b8
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/71103
Tested-by: core-ci <typo3@b13.com>
Tested-by: Jonas Eberle <flightvision@googlemail.com>
Tested-by: Benni Mack <benni@typo3.org>
Reviewed-by: Jonas Eberle <flightvision@googlemail.com>
Reviewed-by: Benni Mack <benni@typo3.org>

Build/Sources/Sass/module/_page.scss

@@ -54,6 +54,10 @@ $page-ce-dropzone-possible-border: $state-warning-border;
     background-color: $page-grid-cell-restricted;
 }
 
+.t3-page-column-unused {
+    background-color: $state-warning-bg;
+}
+
 .t3-grid-cell-hidden {
     display: none;
 }
@@ -104,7 +108,6 @@ $page-ce-dropzone-possible-border: $state-warning-border;
     text-align: left;
 
     [data-colpos='unused'] & {
-        color: $state-warning-text;
         padding-top: $grid-gutter-width*2;
     }
 

typo3/sysext/backend/Classes/View/BackendLayout/Grid/GridColumnItem.php

@@ -87,9 +87,6 @@ public function getWrapperClassName(): string
         if ($this->isDisabled()) {
             $wrapperClassNames[] = 't3-page-ce-hidden t3js-hidden-record';
         }
-        if (!in_array((string)$this->record['colPos'], $this->context->getBackendLayout()->getColumnPositionNumbers(), true)) {
-            $wrapperClassNames[] = 't3-page-ce-warning';
-        }
 
         return implode(' ', $wrapperClassNames);
     }