/Users/sven/Desktop/foo.txt
file:///Users/sven/Desktop/foo.txt

But what about native (OS platform) conventions ?

I don't want to see Windows backslashes, but Windows user might disagree.

file:// is URI scheme and as per RFC (��http://tools.ietf.org/html/rfc1630 ) there is always forward slash; even on Windows.

After all as we've found with git, using backslashes on Windows doesn't even work... so maybe use file:// as universal scheme?