What does it do? 

This system extension provides a backend editor with syntax highlighting. The editor is used for TCA fields with type text and renderType t3editor and in the module Filelist.

Screenshots 

Configured by the following TCA:

'columns' => [
    't3editor_1' => [
        'exclude' => true,
        'label' => 't3editor_1 format=html, rows=7',
        'description' => 'field description',
        'config' => [
            'type' => 'text',
            'renderType' => 't3editor',
            'format' => 'html',
            'rows' => 7,
        ],
    ],
]

With Composer 

If your TYPO3 installation is using Composer, install the t3editor extension by:

composer require typo3/cms-t3editor

If you are using Composer and not working with the latest version of TYPO3 you will need to add a version constraint:

composer require typo3/cms-t3editor:"^10.4"

Without Composer 

If you are working with an installation of TYPO3 that doesn't use Composer, this extension will already be part of the installation due to the fact that legacy .tar & .zip packages come bundled with all system extensions.

However, whilst the extension is already downloaded, it is likely that the extension is not activated.

To activate the t3editor, navigate to Admin Tools > Extension Manager > Installed Extensions and search for "t3editor". If the extension is not active, activate it by selecting the Activate button in the column labeled A/D.

System Maintainer rights are required to activate the extension.

Examples 

'columns' => [
    't3editor_1' => [
        'exclude' => true,
        'label' => 't3editor_1 format=html, rows=7',
        'description' => 'field description',
        'config' => [
            'type' => 'text',
            'renderType' => 't3editor',
            'format' => 'html',
            'rows' => 7,
        ],
    ],
]

Displays an edior like the following:

Prerequisites 

To do this, extensions may have these two files to feed T3editor:

• Configuration/Backend/T3editor/Addons.php
• Configuration/Backend/T3editor/Modes.php

Both files return an array, as known as in TCA and Backend Routes, for example.

Register an addon 

To register an addon, the following code may be used:

<?php

return [
    'my/addon' => [
        'module' => JavaScriptModuleInstruction::create('@codemirror/addon', 'addon')->invoke()
        'cssFiles' => [
            'EXT:my_extension/Resources/Public/Css/MyAddon.css',
        ],
        'options' [
            'foobar' => 'baz',
        ],
        'modes' => ['htmlmixed', 'xml'],
    ],
];

Register a mode 

To register a mode, the following code may be used:

<?php

return [
    'css' => [
        'module' => 'cm/mode/css/css',
        'extensions' => ['css'],
    ],
];