I've set up a Colorbox module on the Drupal 8 based site, and I found that it doesn't work for each content type because Colorbox related CSS and JS files are not being included into all pages.
I have two different content types, lets call it GOOD and BAD. Both has CSS and JS being rendered within standard html.html.twig template and using that <js-placeholder token="{{ placeholder_token }}">
Only difference between them is that in GOOD content type, there is a common Image field where I set a Colorbox as a view "handler" meanwhile in BAD template the Image is being created within it's code. So I added a CSS classes into the equivalent element ( <a class="colorbox .." rtc.) but the problem is that that there is not Colorbox JS file linked within the BAD output html.
Example putput from GOOD (shortened):
<!-- BEGIN OUTPUT from 'themes/cav/templates/html.html.twig' -->
<!DOCTYPE html>
<html lang="cs" dir="ltr" prefix="og: http://ogp.me/ns#">
<head>
...
<link rel="stylesheet" media="all" href="/core/modules/quickedit/css/quickedit.icons.theme.css?q01vyb" />
<link rel="stylesheet" media="all" href="/core/themes/seven/css/components/quickedit.css?q01vyb" />
<link rel="stylesheet" media="all" href="/modules/colorbox/styles/plain/colorbox_style.css?q01vyb" />
<link rel="stylesheet" media="all" href="/core/modules/toolbar/css/toolbar.theme.css?q01vyb" />
...
and from BAD:
<!-- BEGIN OUTPUT from 'themes/cav/templates/html.html.twig' -->
<!DOCTYPE html>
<html lang="cs" dir="ltr" prefix="og: http://ogp.me/ns#">
<head>
<meta charset="utf-8" />
...
<link rel="stylesheet" media="all" href="/core/modules/quickedit/css/quickedit.icons.theme.css?q01ykj" />
<link rel="stylesheet" media="all" href="/core/themes/seven/css/components/quickedit.css?q01ykj" />
<link rel="stylesheet" media="all" href="/core/modules/toolbar/css/toolbar.theme.css?q01ykj" />
...
I somehow feel that those JS and CSS files related to Colorbox are not linked to BAD as I didn't "set up the Colorbox" within the BAD content type (as I couldn't as there is no formal image field) but is there a way how can I "enforece" to adding them into page any other way?
Thanks. TC
Colorbox and all the modules and libraries are loaded only if necessary (as it's a field formatter, it only loads if you display that field in that format). This is the default behaviour to send the browser only the necessary code. You can load Colorbox in every page with the https://www.drupal.org/project/colorbox_inline module.