working directory is not writable on OSX, use standard data location there instead

mainwindow.cpp

@@ -11,6 +11,9 @@
 #include <QTimer>
 #include <QScrollArea>
 #include <QLabel>
+#include <QStandardPaths>
+#include <QDir>
+#include <QFileInfo>
 #include "mainwindow.h"
 #include "libcppotp/bytes.h"
 #include "libcppotp/otp.h"
@@ -25,15 +28,23 @@ extern "C" {
 MainWindow::MainWindow(QWidget *parent) :
   QMainWindow(parent)
   ,m_centralWidget(nullptr)
+#ifdef __APPLE__
+  ,m_settings(QStandardPaths::writableLocation(QStandardPaths::DataLocation) + "/" + qApp->applicationName() + ".ini", QSettings::IniFormat)
+#else
   ,m_settings(qApp->applicationName() + ".ini", QSettings::IniFormat)
+#endif
   ,m_statusLabel(nullptr)
   ,m_timer(new QTimer())
 {
   m_settings.setIniCodec("UTF-8");
 
+#ifdef __APPLE__
+  QFileInfo(m_settings.fileName()).absoluteDir().mkpath(".");
+#endif
+
   if(!m_settings.isWritable()) {
     QMessageBox::critical(0, tr("Error"), tr("Permission denied while trying to write to settings file."));
-    qApp->quit();
+    QTimer::singleShot(0, qApp, &QCoreApplication::quit);
     return;
   }
 
@@ -104,7 +115,7 @@ void MainWindow::rebuildLayout() {
     QString name = names.at(i);
     QString key = m_settings.value(name).toString();
     QString code = generateCode(key);
-    
+
     QLabel *label = new QLabel(name + ": " + code, 0);
     codeVBoxLayout->addWidget(label);
   }