Notice removed Authoritative reference needed by Jose Luis Esparza
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cms_wysiwyg_images_contentscms_wysiwyg_images_content.xml

<?xml version="1.0"?>
<!--
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
-->
<layout xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:View/Layout/etc/layout_generic.xsd">
    <container name="root">
        <referenceBlock name="wysiwyg_images.files">
            <arguments>
                <argument name="template" xsi:type="string">Gamma_Pdftype="string">Vendor_Stuff::browser/content/files.phtml</argument>
            </arguments>
        </referenceBlock>
    </container>
</layout>

cms_wysiwyg_images_contents.xml

<?xml version="1.0"?>
<!--
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
-->
<layout xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:View/Layout/etc/layout_generic.xsd">
    <container name="root">
        <referenceBlock name="wysiwyg_images.files">
            <arguments>
                <argument name="template" xsi:type="string">Gamma_Pdf::browser/content/files.phtml</argument>
            </arguments>
        </referenceBlock>
    </container>
</layout>

cms_wysiwyg_images_content.xml

<?xml version="1.0"?>
<!--
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
-->
<layout xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:View/Layout/etc/layout_generic.xsd">
    <container name="root">
        <referenceBlock name="wysiwyg_images.files">
            <arguments>
                <argument name="template" xsi:type="string">Vendor_Stuff::browser/content/files.phtml</argument>
            </arguments>
        </referenceBlock>
    </container>
</layout>
    Notice added Authoritative reference needed by Jose Luis Esparza
    Bounty Started worth 50 reputation by Jose Luis Esparza
2 added 1 character in body
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cms_wysiwyg_images_contentcms_wysiwyg_images_contents.xml

cms_wysiwyg_images_content.xml

cms_wysiwyg_images_contents.xml

1
source | link

override wysiwyg_images.files

I try to override Magento_Cms::browser/content/files.phtml but when i test , the block is dont display , and i dont know why

i have the next extructure

<Vendor>_<Module>
├── <Stuff>/
│   ├── etc/
│   │   ├── module.xml
│   ├── view/
│   │   ├── adminhtml/
│   │   │   ├── layout
│   │   │   │   ├── cms_wysiwyg_images_contents.xml
│   │   │   ├── templates   
│   │   │   │   ├── browser
│   │   │   │   │   ├── content
│   │   │   │   │   │   ├── files.phtml
│   │   │   ├── web 
│   │   │   │   ├── images  
│   │   │   │   │   ├── icon
│   │   │   │   │   │   ├── pdf.png
│   ├── registration.php/

cms_wysiwyg_images_content.xml

<?xml version="1.0"?>
<!--
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
-->
<layout xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:View/Layout/etc/layout_generic.xsd">
    <container name="root">
        <referenceBlock name="wysiwyg_images.files">
            <arguments>
                <argument name="template" xsi:type="string">Gamma_Pdf::browser/content/files.phtml</argument>
            </arguments>
        </referenceBlock>
    </container>
</layout>

files.phtml

<?php
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */

// @codingStandardsIgnoreFile

 /** @var $block \Magento\Cms\Block\Adminhtml\Wysiwyg\Images\Content\Files */

$_width  = $block->getImagesWidth();
$_height = $block->getImagesHeight();

?>
<?php if ($block->getFilesCount() > 0): ?>
    <?php foreach ($block->getFiles() as $file): ?>
    <div data-row="file" class="filecnt" id="<?= $block->escapeHtmlAttr($block->getFileId($file)) ?>">
        <p class="nm" style="height:<?= $block->escapeHtmlAttr($_height) ?>px;width:<?= $block->escapeHtmlAttr($_width) ?>px;">
        <?php if ($block->getFileThumbUrl($file)):?>
            <img src="<?= $block->escapeHtmlAttr($block->getFileThumbUrl($file)) ?>" alt="<?= $block->escapeHtmlAttr($block->getFileName($file)) ?>"/>
        <?php endif; ?>
        </p>
        <?php if ($block->getFileWidth($file)): ?>
            <small><?= $block->escapeHtml($block->getFileWidth($file)) ?>x<?= $block->escapeHtml($block->getFileHeight($file)) ?> <?= $block->escapeHtml(__('px.')) ?></small><br/>
        <?php endif; ?>
        <small><?= $block->escapeHtml($block->getFileShortName($file)) ?></small>
    </div>
    <?php endforeach; ?>
<?php else: ?>
    <div class="empty"><?= $block->escapeHtml(__('No files found')) ?></div>
<?php endif; ?>

i use "magento/product-community-edition": "2.2.6"

any suggestion ?