Help using QCompleter with QFileSystemModel

[EvanED]

I want to adapt the 'customcompleter' example (http://doc.qt.digia.com/qt/tools-customcompleter.html) to use a file system completer instead of reading out of the word list.

The docs say you can use a QFileSystemModel using the following (http://doc.qt.digia.com/qt/qcompleter.html):

@ QCompleter *completer = new QCompleter(this);
completer->setModel(new QDirModel(completer));
lineEdit->setCompleter(completer);
@

[Typo, btw.] So in the example, I tried changing:

@ completer->setModel(modelFromFile(":/resources/wordlist.txt"));@

to

@ QFileSystemModel * model = new QFileSystemModel(completer);
model->setRootPath("");
completer->setModel(model);
@

(I also tried it without the setRootPath call, passing in "." and "/", and with QDirModel instead.)

It no longer works: the completion window does not appear either on its own or when called with ctrl-E. What am I doing wrong?

[EvanED]

Oh, I guess I should say that I'm using Qt 4.8.1 on Linux.