src_gui_kernel_qapplication.cpp

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QCoreApplication* createApplication(int &argc, char *argv[])
{
    for (int i = 1; i < argc; ++i) {
        if (!qstrcmp(argv[i], "-no-gui"))
            return new QCoreApplication(argc, argv);
    }
    return new QApplication(argc, argv);
}
 
int main(int argc, char* argv[])
{
    QScopedPointer<QCoreApplication> app(createApplication(argc, argv));
 
    if (qobject_cast<QApplication *>(app.data())) {
       // start GUI version...
    } else {
       // start non-GUI version...
    }
 
    return app->exec();
}
 
 
QApplication::setStyle(QStyleFactory::create("Fusion"));
 
 
// ### fixme: Qt 6: Remove [2]
int main(int argc, char *argv[])
{
    QApplication::setColorSpec(QApplication::ManyColor);
    QApplication app(argc, argv);
    ...
    return app.exec();
}
 
 
QSize MyWidget::sizeHint() const
{
    return QSize(80, 25);
}
 
 
void showAllHiddenTopLevelWidgets()
{
    const QWidgetList topLevelWidgets = QApplication::topLevelWidgets();
    for (QWidget *widget : topLevelWidgets) {
        if (widget->isHidden())
            widget->show();
    }
}
 
 
void updateAllWidgets()
{
    const QWidgetList allWidgets = QApplication::allWidgets();
    for (QWidget *widget : allWidgets)
        widget->update();
}
 
 
int main(int argc, char *argv[])
{
    QApplication::setDesktopSettingsAware(false);
    QApplication app(argc, argv);
    ...
    return app.exec();
}
 
 
if ((startPos - currentPos).manhattanLength() >=
        QApplication::startDragDistance())
    startTheDrag();
 
 
void MyApplication::commitData(QSessionManager& manager)
{
    if (manager.allowsInteraction()) {
        int ret = QMessageBox::warning(
                    mainWindow,
                    tr("My Application"),
                    tr("Save changes to document?"),
                    QMessageBox::Save | QMessageBox::Discard | QMessageBox::Cancel);
 
        switch (ret) {
        case QMessageBox::Save:
            manager.release();
            if (!saveDocument())
                manager.cancel();
            break;
        case QMessageBox::Discard:
            break;
        case QMessageBox::Cancel:
        default:
            manager.cancel();
        }
    } else {
        // we did not get permission to interact, then
        // do something reasonable instead
    }
}
 
 
appname -session id
 
 
const QStringList commands = mySession.restartCommand();
for (const QString &command : commands)
    do_something(command);
 
 
const QStringList commands = mySession.discardCommand();
for (const QString &command : commands)
    do_something(command);
 
 
QWidget *widget = QApplication::widgetAt(x, y);
if (widget)
    widget = widget->window();
 
 
QWidget *widget = QApplication::widgetAt(point);
if (widget)
    widget = widget->window();