Magento 2.4 - Build Child Theme parent of theme installed via composer

Question

) I need a tip. I've installed a theme via composer and I need to create a child theme having as parent a theme installed via composer.

path of theme installed via composer: vendor/{vendor}/{theme}/ path of child theme: app/design/frontend/{vendor}/{theme}/

in the child theme folder i've created: theme.xml

<theme xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Config/etc/theme.xsd">
    <title>TitleTheme</title>
    <parent>{folder-name-vendor}/{folder-name-theme}</parent>
    <media>
        <preview_image>media/preview.jpg</preview_image>
    </media>
</theme>

Composer.json

{
    "name": "{my-vendor-folder}/{my-child-theme}",
    "description": "N/A",
    "require": {
        "php": "~5.5.0|~5.6.0|~7.0.0",
        "magento/framework": "100.0.*"
    },
    "type": "magento2-theme",
    "version": "100.0.2",
    "license": [
        "OSL-3.0",
        "AFL-3.0"
    ],
    "autoload": {
        "files": [
            "registration.php"
        ]
    }
}

registration.php

<?php
/**
* Copyright © 2015 Magento. All rights reserved.
* See COPYING.txt for license details.
*/
\Magento\Framework\Component\ComponentRegistrar::register(
    \Magento\Framework\Component\ComponentRegistrar::THEME,
    'frontend/{my-vendor-folder}/{my-child-theme}',
    __DIR__
);

When I change the theme from the magento backend panel under Content > Design > Configuration and then run: php bin/magento setup:upgrade php bin/magento setup:static-content:deploy

It does not load me the parent theme I have chosen, but the default magento theme.I don't know what I'm wrong. Can someone help me? Thank you ;)

Answer 1

I had the same problem. I was using _extend.less in the child theme to add my own styles. But as it turned out the parent theme had an _extend.less extending the blank theme. This approach using a _extend-child.less helped me solve it;

https://devdocs.magento.com/guides/v2.4/frontend-dev-guide/css-guide/css_quick_guide_approach.html