As expected, you gave the most complete answer.
No. I don't want to do this. It may work on most Browsers, but it's not standard compliant. CSS has to be defined in the <head> area.1. Emit the CSS in a <style> block. Maybe even use a @import rule to load the additional style
It's the most compatible way, even If I don't like the extra (nearly useless) plugin.2. Create a bundled event plugin (you should even be able to put sidebar+event plugin in one directory, see serendipity_plugin_adduser)
That's ok for using the plugin in a small environment. But for a simple installation (possibly in spartacus) this does not work. Plugins should work on the fly. (Hey, I'm an Apple User!)Give your users an instruction which CSS to add into their usual style.css files
Very good idea. But what if users deactivated Javascript (…for security reasons…4. Now this is my favourite: Use javascript to inject the style tag into the DOM-Tree of the HEAD-section
)? The plugin output would look ugly. That's not „unobtrusive Javascript“.I prefer solution 2. It's the only clean, compliant way.