QStandardPaths returning inconsistent directories (Windows)

Sprezzatura

I am confused by the directory names returned by QStandardPaths::locate() in Windows. Several different types return the same directory. Some types return a different path at the beginning of program execution, than at the end, the latter being within the executable directory.

Ex:

[A] DataLocation (9), GenericDataLocation (11), ConfigLocation (13), GenericConfigLocation (16) and AppConfigLocation (18) all return the same C:/Users/username/AppData/Local/.

[B] At the end of program execution, DataLocation (9), ConfigLocation (13), AppDataLocation (17) and AppConfigLocation (18) have been switched to \MyApp\Win32\Debug.

I would expect consistent paths, I wouldn't expect to have to save the values at the beginning of a session.

What am I missing?

Sprezzatura

OK, I think I've got it. This is what I called:

QString qstr = QStandardPaths::locate(QStandardPaths::AppDataLocation, "", QStandardPaths::LocateDirectory);

After scrutinizing the documentation, I tried:

QStringList qstrList = QStandardPaths::standardLocations(QStandardPaths::AppDataLocation);

and qstrList[0] is consistently C:/Users/username/AppData/Roaming/

Hurrah! Got what I needed. Thank you all for your contributions and inspiration. I continue to be delighted with Qt.

JonB

@Sprezzatura
I don't know the answer, but just how early is "at the beginning of program execution"? How much Qt start-up has or has not happened by then? Something in your code happening "later" is presumably altering what they return.

Sprezzatura

Here's the main() code:

int main(int argc, char *argv[])
{
	int ret;

	loadAllOptions(rpd);	// first time we call QStandardPaths
	
	QApplication app(argc, argv);
		
	ChooseDialog *chooseDialog = new ChooseDialog(0);	// show a dialog
	chooseDialog->show();
	
	ret = app.exec();
	
	saveAllOptions(rpd);	// second time we call QStandardPaths
	return ret;
}

We don't change any of the QStandardPaths to the best of my knowledge (we're Qt newbies).

J.Hilk

@Sprezzatura said in QStandardPaths returning inconsistent directories (Windows):

QApplication

The very first thing inside your main should be the creation of QApplication.

I had something similar where I had QStandardPaths inside a static QString and that lead to all kinds of issue. I assume the creation of the static string was done before QApplication was finished creating.

Because when I changed it, the problem went away.

JonB

@Sprezzatura
I did not mean that your code changes paths, I meant (I am guessing that) they may get changed by whatever Qt does internally whenever.

I think you should try printing them out immediately after your call to QApplication app(argc, argv);. Are they at that point as they were before that, or are they as they will be at the end of the app where you currently print them a second time?

Sprezzatura

@J-Hilk Good suggestion. Unfortunately, when I move the call to after:

	QApplication app(argc, argv);
	loadAllOptions(rpd);	// first time we call QStandardPaths

AppDataLocation (9) returns \MyApp\Win32\Debug right off the bat. I want it to stay at C:/Users/username/AppData/Roaming/ like it was when I called it before

QApplication app(argc, argv);

J.Hilk

@Sprezzatura
I can not confirm that.

Calling

qDebug() <<  QStandardPaths::writableLocation(QStandardPaths::AppDataLocation);

returns the expected

"C:/Users/<USER>/AppData/Roaming/<APPNAME>",

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    qDebug() << QStandardPaths::writableLocation(QStandardPaths::AppDataLocation);

    return a.exec();
}

JonB

@Sprezzatura
You should read through https://doc.qt.io/qt-5.9/qstandardpaths.html carefully, especially the example table of return results under Windows. E.g.

AppDataLocation    "C:/Users/<USER>/AppData/Roaming/<APPNAME>", "C:/ProgramData/<APPNAME>", "<APPDIR>", "<APPDIR>/data"

I presume your \MyApp\Win32\Debug matches "<APPDIR>". It will only get initialised to include this after QApplication() has been constructed. I assume you know these calls return a list of directories, and you are looking through each element.

Sprezzatura

OK, I think I've got it. This is what I called:

QString qstr = QStandardPaths::locate(QStandardPaths::AppDataLocation, "", QStandardPaths::LocateDirectory);

After scrutinizing the documentation, I tried:

QStringList qstrList = QStandardPaths::standardLocations(QStandardPaths::AppDataLocation);

and qstrList[0] is consistently C:/Users/username/AppData/Roaming/

Hurrah! Got what I needed. Thank you all for your contributions and inspiration. I continue to be delighted with Qt.

Sprezzatura

@JonB Noooo... I did not understand that the enumeration of multiple paths in the Windows example referred to a list. Now I know :o) thanks.