Restoring a Window's Geometry | Qt 5.15

- Qt 5.15
- Best Practice Guides
- Restoring a Window's Geometry
- Qt 5.15.18 Reference Documentation

# 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.