Plumb application quit through platform plugin

If we have a platform plugin we ask the platform to quit, and if
not we fall back to the base implementation of QCoreApplication
that sends Quit events directly.

This allows the platform to involve the rest of the system in the
process. The platform will then come back with a spontaneous quit
via QWSI::handleApplicationTermination(), which will then send
the corresponding Quit even from QGuiApplication like normal.

Task-number: QTBUG-45262
Task-number: QTBUG-33235
Task-number: QTBUG-72013
Task-number: QTBUG-59782
Change-Id: I0000aaf7192e4b905933c5da0e53901c6c88f26a
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

src/corelib/kernel/qcoreapplication.cpp

@@ -1975,11 +1975,18 @@ void QCoreApplication::quit()
     if (!self)
         return;
 
-    if (QThread::currentThread() == self->d_func()->mainThread()) {
+    self->d_func()->quit();
+}
+
+void QCoreApplicationPrivate::quit()
+{
+    Q_Q(QCoreApplication);
+
+    if (QThread::currentThread() == mainThread()) {
         QEvent quitEvent(QEvent::Quit);
-        QCoreApplication::sendEvent(self, &quitEvent);
+        QCoreApplication::sendEvent(q, &quitEvent);
     } else {
-        QCoreApplication::postEvent(self, new QEvent(QEvent::Quit));
+        QCoreApplication::postEvent(q, new QEvent(QEvent::Quit));
     }
 }
 

src/corelib/kernel/qcoreapplication_p.h

@@ -135,6 +135,8 @@ public:
     virtual bool shouldQuit() {
       return true;
     }
+
+    virtual void quit();
     void maybeQuit();
 
     static QBasicAtomicPointer<QThread> theMainThread;

src/gui/kernel/qguiapplication.cpp

@@ -3641,6 +3641,14 @@ bool QGuiApplicationPrivate::shouldQuitInternal(const QWindowList &processedWind
     return true;
 }
 
+void QGuiApplicationPrivate::quit()
+{
+    if (auto *platformIntegration = QGuiApplicationPrivate::platformIntegration())
+        platformIntegration->quit();
+    else
+        QCoreApplicationPrivate::quit();
+}
+
 void QGuiApplicationPrivate::processApplicationTermination(QWindowSystemInterfacePrivate::WindowSystemEvent *windowSystemEvent)
 {
     QEvent event(QEvent::Quit);

src/gui/kernel/qguiapplication_p.h

@@ -105,6 +105,7 @@ public:
     void addQtOptions(QList<QCommandLineOption> *options) override;
 #endif
     virtual bool shouldQuit() override;
+    void quit() override;
 
     bool shouldQuitInternal(const QWindowList &processedWindows);
 

src/gui/kernel/qplatformintegration.cpp

@@ -529,6 +529,20 @@ void QPlatformIntegration::beep() const
 {
 }
 
+/*!
+   \since 6.0
+
+   Asks the platform to terminate the application.
+
+   Overrides should ensure there's a callback into the QWSI
+   function handleApplicationTermination so that the quit can
+   be propagated to QtGui and the application.
+*/
+void QPlatformIntegration::quit() const
+{
+    QWindowSystemInterface::handleApplicationTermination<QWindowSystemInterface::SynchronousDelivery>();
+}
+
 #ifndef QT_NO_OPENGL
 /*!
   Platform integration function for querying the OpenGL implementation type.

src/gui/kernel/qplatformintegration.h

@@ -220,6 +220,7 @@ public:
     virtual void setApplicationIcon(const QIcon &icon) const;
 
     virtual void beep() const;
+    virtual void quit() const;
 
 #if QT_CONFIG(vulkan) || defined(Q_CLANG_QDOC)
     virtual QPlatformVulkanInstance *createPlatformVulkanInstance(QVulkanInstance *instance) const;

src/plugins/platforms/cocoa/qcocoaapplicationdelegate.mm

@@ -92,10 +92,6 @@
 #include <qpa/qwindowsysteminterface.h>
 #include <qwindowdefs.h>
 
-QT_BEGIN_NAMESPACE
-Q_LOGGING_CATEGORY(lcQpaApplication, "qt.qpa.application");
-QT_END_NAMESPACE
-
 QT_USE_NAMESPACE
 
 @implementation QCocoaApplicationDelegate {

src/plugins/platforms/cocoa/qcocoahelpers.h

@@ -72,6 +72,7 @@ Q_DECLARE_LOGGING_CATEGORY(lcQpaWindow)
 Q_DECLARE_LOGGING_CATEGORY(lcQpaDrawing)
 Q_DECLARE_LOGGING_CATEGORY(lcQpaMouse)
 Q_DECLARE_LOGGING_CATEGORY(lcQpaScreen)
+Q_DECLARE_LOGGING_CATEGORY(lcQpaApplication)
 
 class QPixmap;
 class QString;

src/plugins/platforms/cocoa/qcocoahelpers.mm

@@ -59,6 +59,7 @@ Q_LOGGING_CATEGORY(lcQpaWindow, "qt.qpa.window");
 Q_LOGGING_CATEGORY(lcQpaDrawing, "qt.qpa.drawing");
 Q_LOGGING_CATEGORY(lcQpaMouse, "qt.qpa.input.mouse", QtCriticalMsg);
 Q_LOGGING_CATEGORY(lcQpaScreen, "qt.qpa.screen", QtCriticalMsg);
+Q_LOGGING_CATEGORY(lcQpaApplication, "qt.qpa.application");
 
 //
 // Conversion Functions

src/plugins/platforms/cocoa/qcocoaintegration.h

@@ -132,6 +132,7 @@ public:
     void setApplicationIcon(const QIcon &icon) const override;
 
     void beep() const override;
+    void quit() const override;
 
     void closePopups(QWindow *forWindow = nullptr);
 

src/plugins/platforms/cocoa/qcocoaintegration.mm

@@ -488,6 +488,12 @@ void QCocoaIntegration::beep() const
     NSBeep();
 }
 
+void QCocoaIntegration::quit() const
+{
+    qCDebug(lcQpaApplication) << "Terminating application";
+    [NSApp terminate:nil];
+}
+
 void QCocoaIntegration::closePopups(QWindow *forWindow)
 {
     for (auto it = m_popupWindowStack.begin(); it != m_popupWindowStack.end();) {