diff --git a/src/plugins/platforms/wayland/qwaylanddatadevice.cpp b/src/plugins/platforms/wayland/qwaylanddatadevice.cpp
index 11984f9d394..6b2a408eb19 100644
--- a/src/plugins/platforms/wayland/qwaylanddatadevice.cpp
+++ b/src/plugins/platforms/wayland/qwaylanddatadevice.cpp
@@ -154,9 +154,13 @@ void QWaylandDataDevice::data_device_drop()
 
 void QWaylandDataDevice::data_device_enter(uint32_t serial, wl_surface *surface, wl_fixed_t x, wl_fixed_t y, wl_data_offer *id)
 {
-    m_enterSerial = serial;
-    m_dragWindow = QWaylandWindow::fromWlSurface(surface)->window();
+    auto *dragWaylandWindow = QWaylandWindow::fromWlSurface(surface);
+    if (!dragWaylandWindow)
+        return; // Ignore foreign surfaces
+
+    m_dragWindow = dragWaylandWindow->window();
     m_dragPoint = calculateDragPosition(x, y, m_dragWindow);
+    m_enterSerial = serial;
 
     QMimeData *dragData = nullptr;
     Qt::DropActions supportedActions;
diff --git a/src/plugins/platforms/wayland/qwaylanddataoffer.cpp b/src/plugins/platforms/wayland/qwaylanddataoffer.cpp
index 0c732c02078..3da16ed0041 100644
--- a/src/plugins/platforms/wayland/qwaylanddataoffer.cpp
+++ b/src/plugins/platforms/wayland/qwaylanddataoffer.cpp
@@ -135,7 +135,7 @@ QVariant QWaylandMimeData::retrieveData_sys(const QString &mimeType, QVariant::T
     }
 
     int pipefd[2];
-    if (qt_safe_pipe(pipefd, O_NONBLOCK) == -1) {
+    if (qt_safe_pipe(pipefd) == -1) {
         qWarning("QWaylandMimeData: pipe2() failed");
         return QVariant();
     }
@@ -158,23 +158,32 @@ QVariant QWaylandMimeData::retrieveData_sys(const QString &mimeType, QVariant::T
 
 int QWaylandMimeData::readData(int fd, QByteArray &data) const
 {
-    char buf[4096];
-    int retryCount = 0;
-    int n;
-    while (true) {
-        n = QT_READ(fd, buf, sizeof buf);
-        if (n == -1 && (errno == EAGAIN || errno == EWOULDBLOCK) && ++retryCount < 1000)
-            usleep(1000);
-        else
-            break;
-    }
-    if (retryCount >= 1000)
+    fd_set readset;
+    FD_ZERO(&readset);
+    FD_SET(fd, &readset);
+    struct timeval timeout;
+    timeout.tv_sec = 1;
+    timeout.tv_usec = 0;
+
+    int ready = select(FD_SETSIZE, &readset, nullptr, nullptr, &timeout);
+    if (ready < 0) {
+        qWarning() << "QWaylandDataOffer: select() failed";
+        return -1;
+    } else if (ready == 0) {
         qWarning("QWaylandDataOffer: timeout reading from pipe");
-    if (n > 0) {
-        data.append(buf, n);
-        n = readData(fd, data);
+        return -1;
+    } else {
+        char buf[4096];
+        int n = QT_READ(fd, buf, sizeof buf);
+
+        if (n > 0) {
+            data.append(buf, n);
+            n = readData(fd, data);
+        } else if (n < 0) {
+            qWarning("QWaylandDataOffer: read() failed");
+        }
+        return n;
     }
-    return n;
 }
 
 }
diff --git a/src/plugins/platforms/wayland/qwaylanddisplay.cpp b/src/plugins/platforms/wayland/qwaylanddisplay.cpp
index 4a91c1c9697..78524f6fcaf 100644
--- a/src/plugins/platforms/wayland/qwaylanddisplay.cpp
+++ b/src/plugins/platforms/wayland/qwaylanddisplay.cpp
@@ -186,9 +186,9 @@ void QWaylandDisplay::checkError() const
     int ecode = wl_display_get_error(mDisplay);
     if ((ecode == EPIPE || ecode == ECONNRESET)) {
         // special case this to provide a nicer error
-        qWarning("The Wayland connection broke. Did the Wayland compositor die?");
+        qFatal("The Wayland connection broke. Did the Wayland compositor die?");
     } else {
-        qErrnoWarning(ecode, "The Wayland connection experienced a fatal error");
+        qFatal("The Wayland connection experienced a fatal error: %s", strerror(ecode));
     }
 }
 
@@ -198,25 +198,16 @@ void QWaylandDisplay::flushRequests()
         wl_display_read_events(mDisplay);
     }
 
-    if (wl_display_dispatch_pending(mDisplay) < 0) {
+    if (wl_display_dispatch_pending(mDisplay) < 0)
         checkError();
-        exitWithError();
-    }
 
     wl_display_flush(mDisplay);
 }
 
 void QWaylandDisplay::blockingReadEvents()
 {
-    if (wl_display_dispatch(mDisplay) < 0) {
+    if (wl_display_dispatch(mDisplay) < 0)
         checkError();
-        exitWithError();
-    }
-}
-
-void QWaylandDisplay::exitWithError()
-{
-    ::exit(1);
 }
 
 wl_event_queue *QWaylandDisplay::createEventQueue()
@@ -245,10 +236,9 @@ void QWaylandDisplay::dispatchQueueWhile(wl_event_queue *queue, std::function<bo
         else
             wl_display_cancel_read(mDisplay);
 
-        if (wl_display_dispatch_queue_pending(mDisplay, queue) < 0) {
+        if (wl_display_dispatch_queue_pending(mDisplay, queue) < 0)
             checkError();
-            exitWithError();
-        }
+
         if (!condition())
             break;
     }
diff --git a/src/plugins/platforms/wayland/qwaylanddisplay_p.h b/src/plugins/platforms/wayland/qwaylanddisplay_p.h
index 558d8d9b579..7cfbc19b8e2 100644
--- a/src/plugins/platforms/wayland/qwaylanddisplay_p.h
+++ b/src/plugins/platforms/wayland/qwaylanddisplay_p.h
@@ -201,7 +201,6 @@ public slots:
 
 private:
     void waitForScreens();
-    void exitWithError();
     void checkError() const;
 
     void handleWaylandSync();
diff --git a/src/plugins/platforms/wayland/qwaylandinputdevice.cpp b/src/plugins/platforms/wayland/qwaylandinputdevice.cpp
index 9ee3c19d4bb..b5c18a07481 100644
--- a/src/plugins/platforms/wayland/qwaylandinputdevice.cpp
+++ b/src/plugins/platforms/wayland/qwaylandinputdevice.cpp
@@ -562,6 +562,8 @@ void QWaylandInputDevice::Pointer::pointer_enter(uint32_t serial, struct wl_surf
         return;
 
     QWaylandWindow *window = QWaylandWindow::fromWlSurface(surface);
+    if (!window)
+        return; // Ignore foreign surfaces
 
     if (mFocus) {
         qCWarning(lcQpaWayland) << "The compositor sent a wl_pointer.enter event before sending a"
@@ -569,6 +571,7 @@ void QWaylandInputDevice::Pointer::pointer_enter(uint32_t serial, struct wl_surf
                                 << "attempting to work around it by invalidating the current focus";
         invalidateFocus();
     }
+
     mFocus = window;
     connect(mFocus.data(), &QWaylandWindow::wlSurfaceDestroyed, this, &Pointer::handleFocusDestroyed);
 
@@ -597,6 +600,10 @@ void QWaylandInputDevice::Pointer::pointer_leave(uint32_t time, struct wl_surfac
     if (!surface)
         return;
 
+    auto *window = QWaylandWindow::fromWlSurface(surface);
+    if (!window)
+        return; // Ignore foreign surfaces
+
     if (!QWaylandWindow::mouseGrab()) {
         QWaylandWindow *window = QWaylandWindow::fromWlSurface(surface);
         window->handleMouseLeave(mParent);
@@ -972,9 +979,13 @@ void QWaylandInputDevice::Touch::touch_down(uint32_t serial,
     if (!surface)
         return;
 
+    auto *window = QWaylandWindow::fromWlSurface(surface);
+    if (!window)
+        return; // Ignore foreign surfaces
+
     mParent->mTime = time;
     mParent->mSerial = serial;
-    mFocus = QWaylandWindow::fromWlSurface(surface);
+    mFocus = window;
     mParent->mQDisplay->setLastInputDevice(mParent, serial, mFocus);
     mParent->handleTouchPoint(id, wl_fixed_to_double(x), wl_fixed_to_double(y), Qt::TouchPointPressed);
 }
diff --git a/src/plugins/platforms/wayland/qwaylandintegration.cpp b/src/plugins/platforms/wayland/qwaylandintegration.cpp
index ea2b50b4aea..85fcef43fc7 100644
--- a/src/plugins/platforms/wayland/qwaylandintegration.cpp
+++ b/src/plugins/platforms/wayland/qwaylandintegration.cpp
@@ -310,11 +310,14 @@ QPlatformTheme *QWaylandIntegration::createPlatformTheme(const QString &name) co
     return GenericWaylandTheme::createUnixTheme(name);
 }
 
+// May be called from non-GUI threads
 QWaylandClientBufferIntegration *QWaylandIntegration::clientBufferIntegration() const
 {
-    if (!mClientBufferIntegrationInitialized)
+    // Do an inexpensive check first to avoid locking whenever possible
+    if (Q_UNLIKELY(!mClientBufferIntegrationInitialized))
         const_cast<QWaylandIntegration *>(this)->initializeClientBufferIntegration();
 
+    Q_ASSERT(mClientBufferIntegrationInitialized);
     return mClientBufferIntegration && mClientBufferIntegration->isValid() ? mClientBufferIntegration.data() : nullptr;
 }
 
@@ -334,9 +337,12 @@ QWaylandShellIntegration *QWaylandIntegration::shellIntegration() const
     return mShellIntegration.data();
 }
 
+// May be called from non-GUI threads
 void QWaylandIntegration::initializeClientBufferIntegration()
 {
-    mClientBufferIntegrationInitialized = true;
+    QMutexLocker lock(&mClientBufferInitLock);
+    if (mClientBufferIntegrationInitialized)
+        return;
 
     QString targetKey = QString::fromLocal8Bit(qgetenv("QT_WAYLAND_CLIENT_BUFFER_INTEGRATION"));
 
@@ -352,22 +358,25 @@ void QWaylandIntegration::initializeClientBufferIntegration()
 
     if (targetKey.isEmpty()) {
         qWarning("Failed to determine what client buffer integration to use");
-        return;
-    }
-
-    QStringList keys = QWaylandClientBufferIntegrationFactory::keys();
-    qCDebug(lcQpaWayland) << "Available client buffer integrations:" << keys;
-
-    if (keys.contains(targetKey))
-        mClientBufferIntegration.reset(QWaylandClientBufferIntegrationFactory::create(targetKey, QStringList()));
-
-    if (mClientBufferIntegration) {
-        qCDebug(lcQpaWayland) << "Initializing client buffer integration" << targetKey;
-        mClientBufferIntegration->initialize(mDisplay.data());
     } else {
-        qCWarning(lcQpaWayland) << "Failed to load client buffer integration:" << targetKey;
-        qCWarning(lcQpaWayland) << "Available client buffer integrations:" << keys;
+        QStringList keys = QWaylandClientBufferIntegrationFactory::keys();
+        qCDebug(lcQpaWayland) << "Available client buffer integrations:" << keys;
+
+        if (keys.contains(targetKey))
+            mClientBufferIntegration.reset(QWaylandClientBufferIntegrationFactory::create(targetKey, QStringList()));
+
+        if (mClientBufferIntegration) {
+            qCDebug(lcQpaWayland) << "Initializing client buffer integration" << targetKey;
+            mClientBufferIntegration->initialize(mDisplay.data());
+        } else {
+            qCWarning(lcQpaWayland) << "Failed to load client buffer integration:" << targetKey;
+            qCWarning(lcQpaWayland) << "Available client buffer integrations:" << keys;
+        }
     }
+
+    // This must be set last to make sure other threads don't use the
+    // integration before initialization is complete.
+    mClientBufferIntegrationInitialized = true;
 }
 
 void QWaylandIntegration::initializeServerBufferIntegration()
diff --git a/src/plugins/platforms/wayland/qwaylandintegration_p.h b/src/plugins/platforms/wayland/qwaylandintegration_p.h
index 3aef2c4d988..a66999c7f22 100644
--- a/src/plugins/platforms/wayland/qwaylandintegration_p.h
+++ b/src/plugins/platforms/wayland/qwaylandintegration_p.h
@@ -54,6 +54,7 @@
 #include <QtWaylandClient/qtwaylandclientglobal.h>
 #include <qpa/qplatformintegration.h>
 #include <QtCore/QScopedPointer>
+#include <QtCore/QMutex>
 
 QT_BEGIN_NAMESPACE
 
@@ -152,6 +153,7 @@ private:
     mutable QScopedPointer<QPlatformAccessibility> mAccessibility;
 #endif
     bool mFailed = false;
+    QMutex mClientBufferInitLock;
     bool mClientBufferIntegrationInitialized = false;
     bool mServerBufferIntegrationInitialized = false;
     bool mShellIntegrationInitialized = false;
diff --git a/src/plugins/platforms/wayland/qwaylandqtkey.cpp b/src/plugins/platforms/wayland/qwaylandqtkey.cpp
index a60185bd641..19261973853 100644
--- a/src/plugins/platforms/wayland/qwaylandqtkey.cpp
+++ b/src/plugins/platforms/wayland/qwaylandqtkey.cpp
@@ -70,7 +70,11 @@ void QWaylandQtKeyExtension::zqt_key_v1_key(struct wl_surface *surface,
     }
 
     QWaylandInputDevice *dev = inputDevices.first();
-    QWaylandWindow *win = surface ? QWaylandWindow::fromWlSurface(surface) : dev->keyboardFocus();
+
+    auto *win = surface ? QWaylandWindow::fromWlSurface(surface) : nullptr;
+
+    if (!win)
+        win = dev->keyboardFocus();
 
     if (!win || !win->window()) {
         qWarning("qt_key_extension: handle_qtkey: No keyboard focus");
diff --git a/src/plugins/platforms/wayland/qwaylandscreen.cpp b/src/plugins/platforms/wayland/qwaylandscreen.cpp
index 5b04ae60907..d116a807bb9 100644
--- a/src/plugins/platforms/wayland/qwaylandscreen.cpp
+++ b/src/plugins/platforms/wayland/qwaylandscreen.cpp
@@ -217,8 +217,9 @@ QWaylandScreen * QWaylandScreen::waylandScreenFromWindow(QWindow *window)
 
 QWaylandScreen *QWaylandScreen::fromWlOutput(::wl_output *output)
 {
-    auto wlOutput = static_cast<QtWayland::wl_output *>(wl_output_get_user_data(output));
-    return static_cast<QWaylandScreen *>(wlOutput);
+    if (auto *o = QtWayland::wl_output::fromObject(output))
+        return static_cast<QWaylandScreen *>(o);
+    return nullptr;
 }
 
 void QWaylandScreen::output_mode(uint32_t flags, int width, int height, int refresh)
diff --git a/src/plugins/platforms/wayland/qwaylandwindow.cpp b/src/plugins/platforms/wayland/qwaylandwindow.cpp
index 7f82136fe2f..40289d81416 100644
--- a/src/plugins/platforms/wayland/qwaylandwindow.cpp
+++ b/src/plugins/platforms/wayland/qwaylandwindow.cpp
@@ -199,7 +199,9 @@ void QWaylandWindow::initWindow()
 
 void QWaylandWindow::initializeWlSurface()
 {
+    Q_ASSERT(!isInitialized());
     init(mDisplay->createSurface(static_cast<QtWayland::wl_surface *>(this)));
+    emit wlSurfaceCreated();
 }
 
 bool QWaylandWindow::shouldCreateShellSurface() const
diff --git a/src/plugins/platforms/wayland/qwaylandwindow_p.h b/src/plugins/platforms/wayland/qwaylandwindow_p.h
index 9eff738b81f..9a104028857 100644
--- a/src/plugins/platforms/wayland/qwaylandwindow_p.h
+++ b/src/plugins/platforms/wayland/qwaylandwindow_p.h
@@ -203,6 +203,7 @@ public slots:
     void applyConfigure();
 
 signals:
+    void wlSurfaceCreated();
     void wlSurfaceDestroyed();
 
 protected:
diff --git a/src/plugins/platforms/wayland/shared/qwaylandsharedmemoryformathelper_p.h b/src/plugins/platforms/wayland/shared/qwaylandsharedmemoryformathelper_p.h
index 85905c02fa3..72cc8401c26 100644
--- a/src/plugins/platforms/wayland/shared/qwaylandsharedmemoryformathelper_p.h
+++ b/src/plugins/platforms/wayland/shared/qwaylandsharedmemoryformathelper_p.h
@@ -51,7 +51,26 @@ class QWaylandSharedMemoryFormatHelper
 {
 public:
     static inline wl_shm_format fromQImageFormat(QImage::Format format);
-    static inline QImage::Format fromWaylandShmFormat(wl_shm_format format);
+    static inline QImage::Format fromWaylandShmFormat(wl_shm_format format)
+    {
+        switch (format) {
+        case WL_SHM_FORMAT_XRGB8888: return QImage::Format_RGB32;
+        case WL_SHM_FORMAT_ARGB8888: return QImage::Format_ARGB32_Premultiplied;
+        case WL_SHM_FORMAT_RGB565: return QImage::Format_RGB16;
+        case WL_SHM_FORMAT_XRGB1555: return QImage::Format_RGB555;
+        case WL_SHM_FORMAT_RGB888: return QImage::Format_RGB888;
+        case WL_SHM_FORMAT_XRGB4444: return QImage::Format_RGB444;
+        case WL_SHM_FORMAT_ARGB4444: return QImage::Format_ARGB4444_Premultiplied;
+        case WL_SHM_FORMAT_XBGR8888: return QImage::Format_RGBX8888;
+        case WL_SHM_FORMAT_ABGR8888: return QImage::Format_RGBA8888_Premultiplied;
+        case WL_SHM_FORMAT_XBGR2101010: return QImage::Format_BGR30;
+        case WL_SHM_FORMAT_ABGR2101010: return QImage::Format_A2BGR30_Premultiplied;
+        case WL_SHM_FORMAT_XRGB2101010: return QImage::Format_RGB30;
+        case WL_SHM_FORMAT_ARGB2101010: return QImage::Format_A2RGB30_Premultiplied;
+        case WL_SHM_FORMAT_C8: return QImage::Format_Alpha8;
+        default: return QImage::Format_Invalid;
+        }
+    }
     static inline QVector<wl_shm_format> supportedWaylandFormats();
 
 private:
@@ -108,16 +127,6 @@ wl_shm_format QWaylandSharedMemoryFormatHelper::fromQImageFormat(QImage::Format
     return array.data[format];
 }
 
-QImage::Format QWaylandSharedMemoryFormatHelper::fromWaylandShmFormat(wl_shm_format format)
-{
-    Array array = getData();
-    for (size_t i = 0; i < array.size; i++) {
-        if (array.data[i] == format)
-            return QImage::Format(i);
-    }
-    return QImage::Format_Invalid;
-}
-
 QVector<wl_shm_format> QWaylandSharedMemoryFormatHelper::supportedWaylandFormats()
 {
     QVector<wl_shm_format> retFormats;
diff --git a/src/tools/qtwaylandscanner/qtwaylandscanner.cpp b/src/tools/qtwaylandscanner/qtwaylandscanner.cpp
index 56045e88058..7f3dc5ad6bb 100644
--- a/src/tools/qtwaylandscanner/qtwaylandscanner.cpp
+++ b/src/tools/qtwaylandscanner/qtwaylandscanner.cpp
@@ -986,6 +986,7 @@ bool Scanner::process()
             printf("\n");
             printf("        struct ::%s *object() { return m_%s; }\n", interfaceName, interfaceName);
             printf("        const struct ::%s *object() const { return m_%s; }\n", interfaceName, interfaceName);
+            printf("        static %s *fromObject(struct ::%s *object);\n", interfaceName, interfaceName);
             printf("\n");
             printf("        bool isInitialized() const;\n");
             printf("\n");
@@ -1130,6 +1131,16 @@ bool Scanner::process()
             printf("    }\n");
             printf("\n");
 
+            printf("    %s *%s::fromObject(struct ::%s *object)\n", interfaceName, interfaceName, interfaceName);
+            printf("    {\n");
+            if (hasEvents) {
+                printf("        if (wl_proxy_get_listener((struct ::wl_proxy *)object) != (void *)&m_%s_listener)\n", interfaceName);
+                printf("            return nullptr;\n");
+            }
+            printf("        return static_cast<%s *>(%s_get_user_data(object));\n", interfaceName, interfaceName);
+            printf("    }\n");
+            printf("\n");
+
             printf("    bool %s::isInitialized() const\n", interfaceName);
             printf("    {\n");
             printf("        return m_%s != nullptr;\n", interfaceName);