How to hide a QDialog (not showing GUI) on exec() - qt

Question

I want to exec() a QDialog without GUI for my test - there's no need to show GUI.
In the main window, when I exec() a QDialog, it shows its GUI window. I connect a signal from thread in QDialog to a slot in QDialog, so QDialog.exec() is needed. QDialog.hide() is not working.
Is there any solution?

Answer 1

You should never exec() a dialog. This can lead to subtle bugs, because the exec() call can reenter code you don't plan on being reentered.
If you really insist on using exec(), then the simple solution is to post a CloseEvent to the dialog. The event will be processed once the dialog's event loop starts running.
MyDialog dialog;
QCoreApplication::postEvent(&dialog, new QCloseEvent());
dialog.exec();
This code is functionally equivalent to the following:
MyDialog dialog;
QMetaObject::invokeMethod(&dialog, "close", Qt::QueuedConnection);
dialog.exec();
An alternative, much safer way to accomplish this is not to use exec. Simply connect the dialog's accepted() and rejected() signals to slots in your code - after all, the dialog's acceptance or rejection happens asynchronously.
It's then easy enough simply not to show() the dialog in the test code path. You can also easily simulate the dialog being accepted or rejected by invoking either accept or reject slots.
I really don't understand exactly how you "connected" signals from a thread to dialog's slots, and so on. Feel free to paste the example below into your question, modify it to do the threaded "stuff", and show how it doesn't work. It'd also help to see how you implement the test harness.
The example below is all a single file, it'd help if you would keep it that way when producing a test case that illustrates your problem.
// main.cpp
#include <QApplication>
#include <QDialog>
#include <QLabel>
#include <QGridLayout>
#include <QPushButton>
#include <QDialogButtonBox>
class MyDialog : public QDialog {
QGridLayout m_layout;
QDialogButtonBox m_box;
public:
MyDialog(QWidget * parent = 0) : QDialog(parent), m_layout(this),
m_box(QDialogButtonBox::Ok | QDialogButtonBox::Cancel)
{
m_layout.addWidget(&m_box);
connect(&m_box, SIGNAL(accepted()), SLOT(accept()));
connect(&m_box, SIGNAL(rejected()), SLOT(reject()));
}
};
class MyGui : public QWidget {
Q_OBJECT
QGridLayout m_layout;
QLabel m_label;
QPushButton m_button;
MyDialog m_dialog;
Q_SLOT void on_button_clicked() {
m_dialog.show();
}
Q_SLOT void on_dialog_accepted() {
m_label.setText("The dialog was accepted");
}
Q_SLOT void on_dialog_rejected() {
m_label.setText("The dialog was rejected");
}
public:
MyGui() : m_layout(this), m_button("Show Dialog"), m_dialog(this) {
m_button.setObjectName("button");
m_dialog.setObjectName("dialog");
m_layout.addWidget(&m_label);
m_layout.addWidget(&m_button);
QMetaObject::connectSlotsByName(this);
}
};
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
MyGui gui;
gui.show();
return app.exec();
}
#include "main.moc"