MumbleApplication: introduce getenvQString and use it in applicationVersionRoot.

src/mumble/MumbleApplication.cpp

@@ -11,6 +11,54 @@
 #include "GlobalShortcut.h"
 #include "Global.h"
 
+// getenvQString is a wrapper around _wgetenv_s (on Windows)
+// and getenv (on everything else).
+//
+// On Windows, it expects a Unicode environment -- so variables
+// are expected to be UTF16.
+// On everthing else, it expects the environment variables to be
+// UTF-8 encoded.
+static QString getenvQString(QString name) {
+#ifdef Q_OS_WIN
+	QByteArray buf;
+	size_t requiredSize = 0;
+
+	static_assert(sizeof(wchar_t) == sizeof(ushort), "expected 2-byte wchar_t");
+
+	const wchar_t *wname = reinterpret_cast<const wchar_t *>(name.utf16());
+
+	// Query the required buffer size (in elements).
+	_wgetenv_s(&requiredSize, 0, 0, wname);
+	if (requiredSize == 0) {
+		return QString();
+	}
+
+	// Resize buf to fit the value and put it there.
+	buf.resize(static_cast<int>(requiredSize * sizeof(wchar_t)));
+	_wgetenv_s(&requiredSize, reinterpret_cast<wchar_t *>(buf.data()), requiredSize * sizeof(wchar_t), wname);
+
+	// Find the length of the buffer without
+	// counting NUL elements.
+	const wchar_t *wbuf = reinterpret_cast<const wchar_t *>(buf.constData());
+	size_t len = 0;
+	for (len = 0; len < requiredSize; len++) {
+		if (wbuf[len] == 0) {
+			break;
+		}
+	}
+
+	// Convert the value to QString and return it.
+	return QString::fromWCharArray(wbuf, static_cast<int>(len));
+#else
+	QByteArray nameU8 = name.toUtf8();
+	char *val = ::getenv(nameU8.constData());
+	if (val == NULL) {
+		return QString();
+	}
+	return QString::fromUtf8(val);
+#endif
+}
+
 MumbleApplication *MumbleApplication::instance() {
 	return static_cast<MumbleApplication *>(QCoreApplication::instance());
 }
@@ -25,9 +73,9 @@ MumbleApplication::MumbleApplication(int &pargc, char **pargv)
 }
 
 QString MumbleApplication::applicationVersionRootPath() {
-	QByteArray versionRoot = qgetenv("MUMBLE_VERSION_ROOT");
+	QString versionRoot = getenvQString(QLatin1String("MUMBLE_VERSION_ROOT"));
 	if (versionRoot.count() > 0) {
-		return QString::fromUtf8(versionRoot.constData());
+		return versionRoot;
 	}
 	return this->applicationDirPath();
 }