Handle registry_global out of constructor

Factory functions in QWaylandDisplay::registry_global() can be overridden.
Later, other classes instantiated in the registry_global can support
platform specific implementation with inheritance and some factory function.

Change-Id: I92ce574e049b8c91587687cc7c30611f3dfdbe56
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io>

src/plugins/platforms/wayland/qwaylanddisplay.cpp

@@ -162,13 +162,6 @@ QWaylandDisplay::QWaylandDisplay(QWaylandIntegration *waylandIntegration)
     if (!mXkbContext)
         qCWarning(lcQpaWayland, "failed to create xkb context");
 #endif
-
-    forceRoundTrip();
-
-    if (!mWaitingScreens.isEmpty()) {
-        // Give wl_output.done and zxdg_output_v1.done events a chance to arrive
-        forceRoundTrip();
-    }
 }
 
 QWaylandDisplay::~QWaylandDisplay(void)
@@ -193,6 +186,18 @@ QWaylandDisplay::~QWaylandDisplay(void)
         wl_display_disconnect(mDisplay);
 }
 
+// Steps which is called just after constructor. This separates registry_global() out of the constructor
+// so that factory functions in integration can be overridden.
+void QWaylandDisplay::initialize()
+{
+    forceRoundTrip();
+
+    if (!mWaitingScreens.isEmpty()) {
+        // Give wl_output.done and zxdg_output_v1.done events a chance to arrive
+        forceRoundTrip();
+    }
+}
+
 void QWaylandDisplay::ensureScreen()
 {
     if (!mScreens.empty() || mPlaceholderScreen)

src/plugins/platforms/wayland/qwaylanddisplay_p.h

@@ -130,6 +130,8 @@ public:
     QWaylandDisplay(QWaylandIntegration *waylandIntegration);
     ~QWaylandDisplay(void) override;
 
+    void initialize();
+
 #if QT_CONFIG(xkbcommon)
     struct xkb_context *xkbContext() const { return mXkbContext.get(); }
 #endif

src/plugins/platforms/wayland/qwaylandintegration.cpp

@@ -189,8 +189,11 @@ QPlatformNativeInterface *QWaylandIntegration::createPlatformNativeInterface()
     return new QWaylandNativeInterface(this);
 }
 
+// Support platform specific initialization
 void QWaylandIntegration::initializePlatform()
 {
+    mDisplay->initialize();
+
     mNativeInterface.reset(createPlatformNativeInterface());
     initializeInputDeviceIntegration();
 #if QT_CONFIG(clipboard)
@@ -205,9 +208,6 @@ void QWaylandIntegration::initializePlatform()
 
 void QWaylandIntegration::initialize()
 {
-    // Support platform specicif initialization
-    initializePlatform();
-
     QAbstractEventDispatcher *dispatcher = QGuiApplicationPrivate::eventDispatcher;
     QObject::connect(dispatcher, SIGNAL(aboutToBlock()), mDisplay.data(), SLOT(flushRequests()));
     QObject::connect(dispatcher, SIGNAL(awake()), mDisplay.data(), SLOT(flushRequests()));
@@ -216,6 +216,9 @@ void QWaylandIntegration::initialize()
     QSocketNotifier *sn = new QSocketNotifier(fd, QSocketNotifier::Read, mDisplay.data());
     QObject::connect(sn, SIGNAL(activated(QSocketDescriptor)), mDisplay.data(), SLOT(flushRequests()));
 
+    // Call after eventDispatcher is fully connected, for QWaylandDisplay::forceRoundTrip()
+    initializePlatform();
+
     // Qt does not support running with no screens
     mDisplay->ensureScreen();
 }