Restoring a Window's Geometry

This document describes how to save and restore a window's geometry using the geometry properties. On Windows, this is basically storing the result of QWindow::geometry() and calling QWindow::setGeometry() in the next session before calling show().

On X11, this might not work because an invisible window does not have a frame yet. The window manager will decorate the window later. When this happens, the window shifts towards the bottom/right corner of the screen depending on the size of the decoration frame. Although X provides a way to avoid this shift, some window managers fail to implement this feature.

When using Qt Widgets, Qt provides functions that saves and restores a widget window's geometry and state for you. QWidget::saveGeometry() saves the window geometry and maximized/fullscreen state, while QWidget::restoreGeometry() restores it. The restore function also checks if the restored geometry is outside the available screen geometry, and modifies it as appropriate if it is:

  void MyMainWindow::closeEvent(QCloseEvent *event)
  {
      QSettings settings("MyCompany", "MyApp");
      settings.setValue("geometry", saveGeometry());
      settings.setValue("windowState", saveState());
      QMainWindow::closeEvent(event);
  }
  void MainWindow::readSettings()
  {
      QSettings settings("MyCompany", "MyApp");
      restoreGeometry(settings.value("myWidget/geometry").toByteArray());
      restoreState(settings.value("myWidget/windowState").toByteArray());
  }

Another solution is to store both pos() and size() and to restore the geometry using QWidget::resize() and move() before calling show(), as demonstrated in the Application example.