I installed Magento 2 via Composer and it does not have a directory for theme in frontend. I tried to create a new theme in app/design, every time I create registration.php I get an error.
Question
Is it possible to edit the CSS file in vendor/Magento/theme-frontend-blank? Will the changes take in effect on front-end?
I am confused to where should the theme customization should be done. When I use Firebug I see that the location of the CSS files are directing me to pub/static/
In Magento 2, there is a term called static content deployment. You see js/css files links coming from pub/static/ directory because Magento deploys js/css files to this directory from your theme/module directory and whenever a user visits website, static files and referred/shown from pub/static/ directory.
Initially you will be developing your frontend theme in app/design/frontend/ and you can deploy static content to pub/static/frontend/ using command php bin/magento setup:static-content:deploy. During development you should delete everything inside pub/static/, var/cache/, var/page_cache/, var/generation/ and deploy you content using above command.
Here is basic theme configuration example which goes inside app/design/frontend/MyStore/MyAbstract/
theme.xml
<theme xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Config/etc/theme.xsd">
<title>Mystore</title>
<parent>Magento/blank</parent>
<media>
<preview_image>media/preview.jpg</preview_image>
</media>
</theme>
registration.php
<?php
\Magento\Framework\Component\ComponentRegistrar::register(
\Magento\Framework\Component\ComponentRegistrar::THEME,
'frontend/MyStore/MyAbstract',
__DIR__
);
Put preview image preview.jpg (you can change name is theme.xml) inside media directory and you should see your theme in admin section store configuration.
When you install magento2 via composer you find all modules and themes under the vendor dir.
if you want to customize the blank theme, you should create a new theme which is extending the blank theme. (For developing you can create your theme under app/design like in the github repository).
You need at least the registration.php and a theme.xml.
Best example for how to extend the blank theme is the luma theme: https://github.com/magento/magento2/tree/2.0.2/app/design/frontend/Magento/luma
You also should enable the developer mode in your webroots .htaccess file (just remove the #) https://github.com/magento/magento2/blob/develop/.htaccess#L5
The developer mode ensures that files under pub/static are created dynamically and are symlinks on your original files - so they also get the updates
Magento deploys the needed files to pub/static, thats why you find them there. You still have to develop in the theme itself.
