This chapter is from the book
This chapter is from the book
This chapter is from the book
Storing Settings
In the MainWindow constructor, we called readSettings() to load the application's stored settings. Similarly, in closeEvent(), we called writeSettings() to save the settings. These two functions are the last MainWindow member functions that need to be implemented.
void MainWindow::writeSettings()
{
QSettings settings("Software Inc.", "Spreadsheet");
settings.setValue("geometry", saveGeometry());
settings.setValue("recentFiles", recentFiles);
settings.setValue("showGrid", showGridAction->isChecked());
settings.setValue("autoRecalc", autoRecalcAction->isChecked());
}
The writeSettings() function saves the main window's geometry (position and size), the list of recently opened files, and the Show Grid and Auto-Recalculate options.
By default, QSettings stores the application's settings in platform-specific locations. On Windows, it uses the system registry; on Unix, it stores the data in text files; on Mac OS X, it uses the Core Foundation Preferences API.
The constructor arguments specify the organization's name and the application's name. This information is used in a platform-specific way to find a location for the settings.
QSettings stores settings as key–value pairs. The key is similar to a file system path. Subkeys can be specified using a path-like syntax (e.g., findDialog/matchCase) or using beginGroup() and endGroup():
settings.beginGroup("findDialog");
settings.setValue("matchCase", caseCheckBox->isChecked());
settings.setValue("searchBackward", backwardCheckBox->isChecked());
settings.endGroup();
The value can be an int, a bool, a double, a QString, a QStringList, or any other type supported by QVariant, including registered custom types.
void MainWindow::readSettings()
{
QSettings settings("Software Inc.", "Spreadsheet");
restoreGeometry(settings.value("geometry").toByteArray());
recentFiles = settings.value("recentFiles").toStringList();
updateRecentFileActions();
bool showGrid = settings.value("showGrid", true).toBool();
showGridAction->setChecked(showGrid);
bool autoRecalc = settings.value("autoRecalc", true).toBool();
autoRecalcAction->setChecked(autoRecalc);
}
The readSettings() function loads the settings that were saved by writeSettings(). The second argument to the value() function specifies a default value, in case there are no settings available. The default values are used the first time the application is run. Since no second argument is given for geometry or for the recent files list, the window will have an arbitrary but reasonable size and position, and the recent files list will be an empty list on the first run.
The arrangement we opted for in MainWindow, with all the QSettings-related code in readSettings() and writeSettings(), is just one of many possible approaches. A QSettings object can be created to query or modify some setting at any time during the execution of the application and from anywhere in the code.
We have now completed the Spreadsheet's MainWindow implementation. In the following sections, we will discuss how the Spreadsheet application can be modified to handle multiple documents and how to implement a splash screen. We will complete its functionality, including handling formulas and sorting, in the next chapter.