I'm creating a plugin that creates a link to a print button. I've got it working fine as an opt-in renderrer, but I want to know: is there a way to make it so that it works as a widget?

Ie. I have a main blog page which lists 5 posts. I don't want people to see the print button on this page. But I do want it visible on the single post page. Trouble is, I want it to only be visible on certain single post pages.

I've tried combining my current plugin with some code from another plugin that allows you to set it as a widget only plugin... but I get an error. To be honest, I don't really know what I'm doing anyway, just trying stuff to see if I can get it to work.

I can post the code here if necessary. (The working version and the dud)

Thanks!