Hi,
Bundles must be compiled by the add-on developer (the way he/she prefers, and doing it with the resource registry is a very valid way).
The compiled bundle must be stored in the add-on sources and must be specified in registry.xml:
<value key="csscompilation">++resource++xmldirector.dropbox/styles-compiled.min.css</value>
But in your case, it does not really make sense to compile your unique css in a unique css bundle (it would make more sense if you have a bunch of .less or .scss files to compile in a unique css bundle).
So what you should do is to declare your CSS file directly as a bundle:
- remove your first registry entry,
- change the second one like this:
<records prefix="plone.bundles/xmldirector-dropbox"
interface='Products.CMFPlone.interfaces.IBundleRegistry'>
<value key="csscompilation">++resource++xmldirector.dropbox/styles.css</value>
<value key="enabled">True</value>
<value key="compile">False</value>
<value key="depends">plone</value>
</records>```
And that's it, no complation needed.