> The file manager then launches your PDF viewer and hands it the token. The PDF viewer, upon starting, shows this token to the compositor and asks to be activated. The compositor checks if the token is legit and, if so, gives the PDF viewer focus.

>If the token is missing, old, or otherwise invalid, the compositor says no.

Doesn't seem to go far enough. If this is a long operation and you switch to another app to read a page in a browser, will the opened PDF steal focus from your reading or allow you to switch to PDF at your own leisure?

> The viewer window will not get focus, and instead, its icon in the taskbar will start flashing to grab your attention.

This is just a common awful alternative. There is nothing important about this activity to flash, charging the style once would be just fine. But at least it's not jumping up like the UI geniuses at Apple have done.

But otherwise, great initiative, focus stealing is a serious UI crime!