set a QDialog's initial location

[high_flyer]

I'd try the following:
0. Remove the moving code from the constructor.
1. Create the dialog hidden.
2. Call setGeometry() on it from the parent.
3. show it.

[tfort]

Thank you - this is the final solution that worked for me

helpDialog.h - same as above

in helpDialog.cpp:

HelpDialog::HelpDialog(QWidget *const theParent)
      : QDialog(theParent)
      , ui(new Ui::HelpDialog)
   {
      ui->setupUi(this);
 
      // display the dialog on the right of the current screen.
      if (nullptr != theParent)
      {
         setWindowFlags(Qt::Window); //ensure the minimize button on the QDialog
      }
 
   }

HelpDialog::HelpDialog(QWidget *const theParent)
      : QDialog(theParent)
      , ui(new Ui::HelpDialog)
   {
      ui->setupUi(this);

      // display the dialog on the right of the current screen.
      if (nullptr != theParent)
      {
         setWindowFlags(Qt::Window); //ensure the minimize button on the QDialog
      }

   }

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in code for main application window to bring this up:
in class init() function:

myHelpDialog = new HelpDialog(this);
   //lamba to handle pressing of help button
   const auto ToggleHelp = [this]()
   {
      const QString HelpText = tr("Some help text goes here");
 
      if (isVisible())
      {
         myHelpDialog ->setMessage(HelpText);
 
         //place help dialog "top right" corner just inside the top right corner of parent window
         QRect rect = myHelpDialog->geometry();  //get current geometry of help window
         QRect parentRect = this->geometry();      //get current geometry of this window
         rect.moveTo(mapToGlobal(QPoint(parentRect.x() + parentRect.width() - rect.width(), parentRect.y())));
 
         myHelpDialog ->setGeometry(rect);
 
         myHelpDialog ->show();  //use show for nonmodal dialogs
      }
   };
   ( void )connect(m_footerWidget, &FooterWidget::helpButtonClicked, ToggleHelp);
   myHelpDialog ->hide();

myHelpDialog = new HelpDialog(this);
   //lamba to handle pressing of help button
   const auto ToggleHelp = [this]()
   {
      const QString HelpText = tr("Some help text goes here");

      if (isVisible())
      {
         myHelpDialog ->setMessage(HelpText);

         //place help dialog "top right" corner just inside the top right corner of parent window
         QRect rect = myHelpDialog->geometry();  //get current geometry of help window
         QRect parentRect = this->geometry();      //get current geometry of this window
         rect.moveTo(mapToGlobal(QPoint(parentRect.x() + parentRect.width() - rect.width(), parentRect.y())));

         myHelpDialog ->setGeometry(rect);

         myHelpDialog ->show();  //use show for nonmodal dialogs
      }
   };
   ( void )connect(m_footerWidget, &FooterWidget::helpButtonClicked, ToggleHelp);
   myHelpDialog ->hide();

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