3
It's even easier than that:
<{$xoTheme->folderName}>
There are also path generators:
<{xoAppUrl path/to/filename.ext}> will create:
XOOPS_URL/path/to/filename.ext
<{xoImgUrl path/to/filename.ext}> will create:
XOOPS_URL/themes/themedir/path/to/filename.ext
This second one will also try (should filename.ext not exist):
XOOPS_URL/images/path/to/filename.ext
And of course, $xoTheme has many other variables available as well.