FIX(client) : Fixed config directory path assignment

[supersanban]

Config directory path in Linux should be picked from XDG_CONFIG_HOME environment variable.

Fixes #6029

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[Krzmbrzl]

Please change your commit message to what you have chosen for the PR title (git commit --amend) and also add the Fixes #6029 into the commit message body

[Hartmnt]

Has anyone actually verified that this fixes #6029?

If I understand correctly, the order of datapaths determines the preferred location to read from and write to. That means the mumble.sqlite, if it does not already exist, will be preferably placed in:

	datapaths << Global::get().qdBasePath.absolutePath();
	datapaths << QStandardPaths::writableLocation(QStandardPaths::DataLocation);

in that order, where qdBasePath refers to this line of code which resolves QStandardPaths::AppDataLocation to ~/.local/share/<APPNAME> [1].

The second entry is QStandardPaths::DataLocation is deprecated in Qt5 [2] and the same as QStandardPaths::AppDataLocation and QStandardPaths::AppLocalDataLocation (on Linux) and REMOVED in Qt6 [1]

Now as I see it, the changed code is only triggered, if ~/.local/share/<APPNAME> does not already contain a Mumble file and is not writable - which is possible, but unlikely on most systems.
The Qt documentation lists ~/.local/share[...]. Are we actually sure the ~ will be XDG_HOME or whatever it is exactly?
I am actually unable to find a reliable Qt source that states, if XDG is honored on Linux with regards to the QStandardPaths class...

I can barely wrap my head about the problem at this point. Can we have some decision matrix/table or something to visualize what is supposed to be stored where and when?

[1] https://doc.qt.io/qt-6/qstandardpaths.html
[2] https://doc.qt.io/qt-5/qstandardpaths.html

[Hartmnt]

Additional information:

On my very little used Mumble test VM, there is a ~/.local/share/Mumble/Mumble which contains the mumble.sqlite and the Themes and Plugins folder, as I would expect given my previous explanation. But there is also a ~/.config/Mumble/Mumble which contains the mumble_settings.json
So we have to at least also consider this function

[Krzmbrzl]

Has anyone actually verified that this fixes #6029?

I haven't. My thinking was that so far, the hard-coded path in the home-directory was used and this path has now been replaced by the XDG_CONFIG_HOME variable - if present.
However, we should indeed fix the logic here.

Other than that, this PR should probably also address the location of the settings JSON file:

mumble/src/mumble/Settings.cpp

Lines 1273 to 1322 in c338d1d

	QString Settings::findSettingsLocation(bool legacy, bool *foundExistingFile) const {
	// In order to make sure we'll find (mostly legacy) settings files, even if they end up being in a slightly
	// different dir than we currently expect, we construct a search path list that we'll traverse while searching for
	// the settings file. In case we find a suitable settings file within the search path, then we'll continue to use
	// this path instead of creating a new one (in the location that we currently think is best to use).
	QStringList paths;
	paths << QCoreApplication::instance()->applicationDirPath();
	paths << QStandardPaths::writableLocation(QStandardPaths::DataLocation);
	paths << QStandardPaths::writableLocation(QStandardPaths::AppConfigLocation);
	paths << QStandardPaths::writableLocation(QStandardPaths::ConfigLocation);
	paths << QFileInfo(QSettings().fileName()).dir().absolutePath();
	QStringList settingsFileNames = legacy ? QStringList({ QStringLiteral("mumble.conf"), QStringLiteral("Mumble.conf"),
	QStringLiteral("mumble.ini"), QStringLiteral("Mumble.ini") })
	: QStringList({ QStringLiteral("mumble_settings.json") });
	QString chosenPath;
	for (const QString &settingsFileName : settingsFileNames) {
	for (const QString &currentPath : paths) {
	QFile settingsFile(QString::fromLatin1("%1/%2").arg(currentPath).arg(settingsFileName));
	if (settingsFile.exists() && settingsFile.permissions().testFlag(QFile::WriteUser)) {
	// Found existing settings file -> use that
	chosenPath = QFileInfo(settingsFile).absoluteFilePath();
	break;
	}
	}
	}
	if (foundExistingFile) {
	*foundExistingFile = !chosenPath.isEmpty();
	}
	if (chosenPath.isEmpty()) {
	// We were unable to find an existing settings file -> Fall back to a default location
	chosenPath = QString::fromLatin1("%1/%2")
	.arg(QStandardPaths::writableLocation(QStandardPaths::AppConfigLocation))
	.arg(settingsFileNames[0]);
	// Note: QStandardPaths::AppConfigLocation will return a directory of the style <root>/<org>/<application> where
	// <root> is the path to the general config related directory on the respective OS, <org> is the name of our
	// organization and <application> is our application's name. In our case (at the time of writing this) <org> =
	// <application> = Mumble, leading to a doubly nested "Mumble" directory. This should only be a cosmetic issue
	// though.
	}
	return chosenPath;
	}

[Krzmbrzl]

@supersanban will you address the remaining issues?