Question

I am developing a project using Qt4 and I have run into a slight issue.
I am creating a modal window from the main window. I want this to disable the toolbar at the top.
I have a menu item that spawns the modal from the menu. What I want is that when the modal is spawned that menus is disabled. I have tried using the setEnabled(false) function but that doesn’t reset it.

Here is the code:

void Main_Screen::Create_ViPro()
{
   std::auto_ptr<ViPro_Dialog> modal(new ViPro_Dialog(this));
   modal->show();
   modal->exec();
}

So It is just a simple class that is triggered when a menu item is selected. I feel that the problem stems from the fact that i’m setting the parent to the main screen, however I don’t know how to create a modal without a parent(it doesn’t make sense to do that). Is there a way to disable the parents toolbar from the child? The only thing I have seen so far is _fileMenu->setEnabled(false);
That works as long as I don’t create the modal, but as soon as that is spawned, the menu works again. I’m totally lost.
Thanks in advance

Edit as Patrice

Here is the constructor

    Main_Screen::Main_Screen(QWidget* parent /*= NULL*/) 
                        : QMainWindow(parent),
                          _newProj(new QAction(tr("New &ViPro"), this)),
                          _fileMenu(menuBar()->addMenu(tr("&File")))
{    
  //create slot for creating a new project
  connect(_newProj.get(), SIGNAL(triggered()), this, SLOT(Create_ViPro()));
  _fileMenu->addAction(_newProj.get());
  //if i do this then setEnabled(false) works perfectly and i can't access the menu
  Create_ViPro()
}

So the function is signaled by triggering the newproject action. If i call the function directly from within the constructor it disables it as you stated patrice, however, if I have the function called via the trigger, it doesn’t disable it. Am I handling the signal / slot mechanism wrong? Thanks again.

Another example, if I make the function create_vipro() as below

void Main_Screen::Create_ViPro()
{
     _fileMenu->setEnabled(false);
}

The file menu isn’t disabled when I trigger the event, so it must have nothing to do with the modal itself, but instead how signals are handled.

Answer 1

Since child is a modal dialog main screen can’t react to event. But you can disable the toolbar (or menubar) before creating the modal dialog and enable it as soon as you leave the exec function:

void Main_Screen::Create_ViPro()
{
   _fileMenu->setEnabled(false);

   std::auto_ptr<ViPro_Dialog> modal(new ViPro_Dialog(this));
   modal->show();
   modal->exec(); // Will stay here until you close the modal dialog

   _fileMenu->setEnabled(true);
}

if ViPro_Dialog is really a modal dialog it will works.

Another thing, since ViPro_Dialog is modal you can declare it locally without using auto_ptr:

void Main_Screen::Create_ViPro()
{
   _fileMenu->setEnabled(false);

   ViPro_Dialog modal(this);
   modal.show();
   modal.exec(); // Will stay here until you close the modal dialog

   _fileMenu->setEnabled(true);
}

EDIT:

I guess (I can’t test at work) that you can’t enable/disable menu when it is executing a QAction. Signal is calling slots sequentially so QAction is busy when you try to disable the menu.
Try this:

1. In Main Screen, create a slot with one boolean parameter that enable/disable menubar. Just call the setEnabled function
2. In ViPro_Dialog, emit a signal with a boolean parameter (false at startup, true at validation)
3. In Create_ViPro, once dialog created, connect the new signal with the slot, exec dialog and don’t forget to disconnect slot from signal:

void Main_Screen::Create_ViPro()
{
ViPro_Dialog modal(this);

// Connect signal/slot

modal.show();
modal.exec(); // Will stay here until you close the modal dialog

// Disconnect signal/slot
}

This can achieve what you want

EDIT2

You are doing a mistake when using modal dialog. There’s a conflict between show() and exec(). When you are displaying modal dialog you don’t need to disable other windows: it’s automatically done by modal status of the dialog. There are many modal depth: http://qt-project.org/doc/qt-4.8/qt.html#WindowModality-enum. So your code should be:

void Main_Screen::Create_ViPro()
{
   ViPro_Dialog modal(this);

   // modal.setWindowModality(Qt::WindowModal); // Uncomment this line if you want to only disable parent

   modal.exec();
}

Read this for more detail: http://qt-project.org/doc/qt-4.8/QDialog.html#details.