QSettings mismatch when read by two different classes

Poldi

I have two classes reading the same Settings file and can't work out why one of the gives the correct results, while the other doesn't

The class that works looks something like this

const char *NetworkRemote::kSettingsGroup = "Remote";

void NetworkRemote::Init()
{
  QSettings s_;
  s_.beginGroup(NetworkRemote::kSettingsGroup);
  use_remote_ = s_.value("useRemote").toBool();
  local_only_ = s_.value("localOnly").toBool();
  remote_port_ = s_.value("remotePort").toInt();
  ipAddr_.setAddress(s_.value("ipAddress").toString());

  bool aa = s_.value("useRemote").toBool();
  bool bb = s_.value("localOnly").toBool();
  int cc = s_.value("remotePort").toInt();
  QString dd =s_.value("ipAddress").toString();
  qLog(Debug) << "Settings " << s_.fileName();
  qLog(Debug) << "Keys are " << s_.allKeys();
  qLog(Debug) << "aa = " << aa;
  qLog(Debug) << "bb = " << bb;
  qLog(Debug) << "cc = " << cc;
  qLog(Debug) << "dd = " << dd;
  
}

The one that fails looks something like this

const char *NetworkRemoteSettingsPage::kSettingsGroup = "Remote";

void NetworkRemoteSettingsPage::Load()
{
QSettings s_;
s_.beginGroup(NetworkRemoteSettingsPage::kSettingsGroup);

  bool aa = s_.value("useRemote").toBool();
  bool bb = s_.value("localOnly").toBool();
  int cc = s_.value("remotePort").toInt();
  QString dd =s_.value("ipAddress").toString();
  qLog(Debug) << "Settings " << s_.fileName();
  qLog(Debug) << "Keys are " << s_.allKeys();
  qLog(Debug) << "aa = " << aa;
  qLog(Debug) << "bb = " << bb;
  qLog(Debug) << "cc = " << cc;
  qLog(Debug) << "dd = " << dd;
  
}

The terminal output for works & fails are attached

Thanks

jsulm

@Poldi Maybe because in first case you have s_.beginGroup(NetworkRemote::kSettingsGroup); and in the second s_.beginGroup(NetworkRemoteSettingsPage::kSettingsGroup); ?

JonB

@jsulm
No, because code posted shows/claims both these are defined as the string "Remote".

@Poldi
Purely at a guess, I see one reports cc = 5053 and the other cc = 5050. These do not seem like "coincidental" values. I would look at exactly where you call these and what happens in between the calls, because it sounds like things have changed. Don't forget: QSettings does not flush changed values to file immediately, you may not be looking at what you think you are. You are not using separate threads here, are you?

Axel Spoerl

@Poldi
Settings get cached and what you experience looks like a race condition on the cache.
Try sync after the modification. If you work in different threads, mutex the settings.

Poldi

Here is a bit more detail

Yes, the two classes are in different threads, but the changes to the config file can only be made via the gui and the class NetworkRemoteSettingsPage.

I've attached a screenshot of the config file and the gui

Another interesting observation is that the changes I make via the gui always end up in the config file; it just doesn't get read correctly

Here is a more code

void NetworkRemoteSettingsPage::Load()
{
  ui_->portSelected->setRange(5050, 65535);
  ui_->ip_address->setText("0.0.0.0");

  s_.beginGroup(NetworkRemoteSettingsPage::kSettingsGroup);

  bool aa = s_.value("useRemote").toBool();
  bool bb = s_.value("localOnly").toBool();
  int cc = s_.value("remotePort").toInt();
  QString dd =s_.value("ipAddress").toString();
  qLog(Debug) << "Settings " << s_.fileName();
  qLog(Debug) << "Keys are " << s_.allKeys();
  qLog(Debug) << "aa = " << aa;
  qLog(Debug) << "bb = " << bb;
  qLog(Debug) << "cc = " << cc;
  qLog(Debug) << "dd = " << dd;

  if (s_.contains("useRemote")){
    ui_->useRemoteClient->setChecked(s_.value("useRemote", false).toBool());
    if (s_.value("useRemote").toBool()){
      ui_->localConnectionsOnly->setCheckable(true);
      ui_->portSelected->setReadOnly(false);
      ui_->localConnectionsOnly->setChecked(s_.value("localOnly", true).toBool());
      ui_->portSelected->setValue(s_.value("remotePort", 5050).toInt());
    }
    else {
      ui_->localConnectionsOnly->setCheckable(false);
      ui_->portSelected->setReadOnly(true);
    }
  }
  else{
    qLog(Debug) << "First time run the Network Remote";
    s_.setValue("useRemote", false);
    s_.setValue("localOnly",false);
    s_.setValue("remotePort",5050);
    s_.setValue("ipAddress","0.0.0.0");
  }
  s_.endGroup();
  DisplayIP();

  Init(ui_->layout_networkremotesettingspage->parentWidget());
}

void NetworkRemoteSettingsPage::Save()
{
  s_.beginGroup(NetworkRemoteSettingsPage::kSettingsGroup);
  s_.setValue("useRemote",ui_->useRemoteClient->isChecked());
  s_.setValue("localOnly",ui_->localConnectionsOnly->isChecked());
  s_.setValue("remotePort",int(ui_->portSelected->value()));
  s_.setValue("ipAddress",ipAddr_);
  s_.endGroup();
}

Poldi

I think I found the problem

the RemoteSettingsPage code sets up a few connectors to handle the screen changes

NetworkRemoteSettingsPage::NetworkRemoteSettingsPage(SettingsDialog *dialog, QWidget *parent) :
    SettingsPage(dialog,parent),
    ui_(new Ui_NetworkRemoteSettingsPage)
{

  ui_->setupUi(this);
  setWindowIcon(IconLoader::Load("network-remote", true, 0,32));
  
  QObject::connect(ui_->useRemoteClient,&QCheckBox::stateChanged, this, &NetworkRemoteSettingsPage::RemoteButtonClicked);
  QObject::connect(ui_->localConnectionsOnly, &QCheckBox::stateChanged, this, &NetworkRemoteSettingsPage::LocalConnectButtonClicked);
  QObject::connect(ui_->portSelected, &QSpinBox::valueChanged, this, &NetworkRemoteSettingsPage::PortChanged);
}

Any changes invoke a Refresh(), which incokes a (Settings) Save() and then a Load().
My expectation is/was that the

void NetworkRemoteSettingsPage::Load()

was invoked first, but what is happening is that when the page loads it triggers the PortChanged signal (not sure why), which invokes Refresh().

Poldi

I changed the events and it all works now as expected

  QObject::connect(ui_->useRemoteClient,&QAbstractButton::clicked, this, &NetworkRemoteSettingsPage::RemoteButtonClicked);
  QObject::connect(ui_->localConnectionsOnly, &QAbstractButton::clicked, this, &NetworkRemoteSettingsPage::LocalConnectButtonClicked);
  QObject::connect(ui_->portSelected, &QAbstractSpinBox::editingFinished, this, &NetworkRemoteSettingsPage::PortChanged);

Axel Spoerl

@Poldi
If one thread writes settings and the other reads it, it would still consider using settings.sync() and mutexing access to settings.

Poldi

@Axel-Spoerl Sure, although the only way to change the settings is via this one gui page.
Thanks