Unexpected behavior of QFileSystemModel

JonB

@midnightdim
This is not good! :( Assuming your filing system on D: is the same as on C:, plus it's a local drive, both of which I imagine are the case.

Any chance of testing it from PySide2 or even PyQt5/6? If it's really an issue, I imagine it will lie in QFileSystemModel (perhaps under Qt6), rather than being anything Python/PySide/PyQt related....

midnightdim

@JonB I tried to quickly port to PySide2, but ran into some issues.
I could port it to PyQt6, and I could reproduce this issue.
So it looks like this problem lies deeper. I'll check if I can reports this bug in Qt bug tracker.

JonB

@midnightdim
Shame you couldn't have tried PyQt5. Your usage looks OK, and QFileSystemModel must work right in versions of Qt prior to 6?

midnightdim

@JonB I found a bug that looks kind of similar: https://bugreports.qt.io/browse/QTBUG-12934
But it's closed as invalid.

JonB

@midnightdim
Yes, that is indeed your situation. But it's closed/invalid because you need to read what the comments say and make your QFileSystemModel::rootPath line up with your QTreeView::setRootIndex().

midnightdim

@JonB OK, this is exactly the same issue that was described in https://bugreports.qt.io/browse/QTBUG-12934

When I set the root path to "" and have the full tree displayed, and then I expand the first drive C: all folders look as expected.
However, all folders under other drives have files and folders mixed - exactly like on the screenshots attached to the issue.

I don't fully understand the solution. The comment before the last one says:

But it's not a bug imho.
The user explicitly sets the QFileSystemModel::rootPath to be a sub-tree of the model (C:\ in this case).
Now he is supposed to use QTreView::setRootIndex() to show only the sub-tree, D:'s sorting becomes a moot point because it's hidden.

What exactly should be updated in the code to have this resolved? It's not clear from setRootIndex documentation for QTreeView.

midnightdim

@JonB Here's how I'm using it:

path = r"D:\Downloads"
self.model = QFileSystemModel()
self.model.setRootPath((QDir.rootPath()))
self.ui.treeView.setModel(self.model)
self.ui.treeView.setRootIndex(self.model.index(path))

It seems to correspond to what that ticket suggests.

midnightdim

OK, I found my mistake. It should be:

path = r"D:\Downloads"
self.model = QFileSystemModel()
self.model.setRootPath(path)
self.ui.treeView.setModel(self.model)
self.ui.treeView.setRootIndex(self.model.index(path))

I.e. root path should be set to the same folder. Thanks for your support.

JonB

@midnightdim
Good stuff.

As a small tip: Qt pathnames (for Qt functions expecting a pathname) are best always written using /s instead of \s, on every platform, even Windows. path = "D:/Downloads". The same for Python's pathlib. Tends to work with backslashes, but can be "gotchas", so use forward always.

midnightdim

@JonB Thanks. I use os.path.normpath everywhere to get rid of this kind of problems :)