Merge remote-tracking branch 'origin/5.9' into dev

Conflicts:
	examples/examples.pro
	qmake/library/qmakebuiltins.cpp
	src/corelib/global/qglobal.cpp
		Re-apply b525ec2 to qrandom.cpp(code movement in 030782e)
	src/corelib/global/qnamespace.qdoc
	src/corelib/global/qrandom.cpp
	src/gui/kernel/qwindow.cpp
		Re-apply a3d59c7 to QWindowPrivate::setVisible() (code movement in d7a9e08)
	src/network/ssl/qsslkey_openssl.cpp
	src/plugins/platforms/android/androidjniinput.cpp
	src/plugins/platforms/xcb/qxcbconnection.cpp
	src/plugins/platforms/xcb/qxcbconnection_xi2.cpp
	src/widgets/widgets/qmenu.cpp
	tests/auto/widgets/kernel/qwidget_window/tst_qwidget_window.cpp

Change-Id: If7ab427804408877a93cbe02079fca58e568bfd3

19 files changed, 79 insertions, 159 deletions

diff --git a/src/plugins/platforms/android/extract.cpp b/src/plugins/platforms/android/extract.cpp
index e6636e37d4..2f2ffa7126 100644
--- a/src/plugins/platforms/android/extract.cpp
+++ b/src/plugins/platforms/android/extract.cpp
@@ -43,6 +43,7 @@
 #include <android/log.h>
 #include <extract.h>
 #include <alloca.h>
+#include <stdlib.h>
 
 #define LOG_TAG    "extractSyleInfo"
 #define LOGE(...)  __android_log_print(ANDROID_LOG_ERROR,LOG_TAG,__VA_ARGS__)
diff --git a/src/plugins/platforms/android/qandroidinputcontext.cpp b/src/plugins/platforms/android/qandroidinputcontext.cpp
index 279cb338f4..7fa809f3f8 100644
--- a/src/plugins/platforms/android/qandroidinputcontext.cpp
+++ b/src/plugins/platforms/android/qandroidinputcontext.cpp
@@ -303,7 +303,7 @@ static jboolean paste(JNIEnv */*env*/, jobject /*thiz*/)
         return JNI_FALSE;
 
 #ifdef QT_DEBUG_ANDROID_IM_PROTOCOL
-    qDebug("@@@");
+    qDebug("@@@ PASTE");
 #endif
     return m_androidInputContext->paste();
 }
@@ -1138,6 +1138,7 @@ jboolean QAndroidInputContext::copyURL()
 
 jboolean QAndroidInputContext::paste()
 {
+    finishComposingText();
     m_cursorHandleShown = CursorHandleNotShown;
     sendShortcut(QKeySequence::Paste);
     return JNI_TRUE;
diff --git a/src/plugins/platforms/cocoa/qcocoaeventdispatcher.mm b/src/plugins/platforms/cocoa/qcocoaeventdispatcher.mm
index 874d3fc24b..bf9ba4eccf 100644
--- a/src/plugins/platforms/cocoa/qcocoaeventdispatcher.mm
+++ b/src/plugins/platforms/cocoa/qcocoaeventdispatcher.mm
@@ -400,8 +400,18 @@ bool QCocoaEventDispatcher::processEvents(QEventLoop::ProcessEventsFlags flags)
             // [NSApp run], which is the normal code path for cocoa applications.
             if (NSModalSession session = d->currentModalSession()) {
                 QBoolBlocker execGuard(d->currentExecIsNSAppRun, false);
-                while ([NSApp runModalSession:session] == NSModalResponseContinue && !d->interrupt)
+                while ([NSApp runModalSession:session] == NSModalResponseContinue && !d->interrupt) {
                     qt_mac_waitForMoreEvents(NSModalPanelRunLoopMode);
+                    if (session != d->currentModalSessionCached) {
+                        // It's possible to release the current modal session
+                        // while we are in this loop, for example, by closing all
+                        // windows from a slot via QApplication::closeAllWindows.
+                        // In this case we cannot use 'session' anymore. A warning
+                        // from Cocoa is: "Use of freed session detected. Do not
+                        // call runModalSession: after calling endModalSesion:."
+                        break;
+                    }
+                }
 
                 if (!d->interrupt && session == d->currentModalSessionCached) {
                     // Someone called [NSApp stopModal:] from outside the event
diff --git a/src/plugins/platforms/cocoa/qcocoamenu.mm b/src/plugins/platforms/cocoa/qcocoamenu.mm
index 77a531f25d..eeb4c01791 100644
--- a/src/plugins/platforms/cocoa/qcocoamenu.mm
+++ b/src/plugins/platforms/cocoa/qcocoamenu.mm
@@ -426,6 +426,7 @@ void QCocoaMenu::scheduleUpdate()
 void QCocoaMenu::timerEvent(QTimerEvent *e)
 {
     if (e->timerId() == m_updateTimer) {
+        killTimer(m_updateTimer);
         m_updateTimer = 0;
         [m_nativeMenu update];
     }
diff --git a/src/plugins/platforms/cocoa/qcocoaprintersupport.h b/src/plugins/platforms/cocoa/qcocoaprintersupport.h
index 371212dae2..a07bf0ec1b 100644
--- a/src/plugins/platforms/cocoa/qcocoaprintersupport.h
+++ b/src/plugins/platforms/cocoa/qcocoaprintersupport.h
@@ -53,7 +53,7 @@ public:
     QCocoaPrinterSupport();
     ~QCocoaPrinterSupport();
 
-    QPrintEngine *createNativePrintEngine(QPrinter::PrinterMode printerMode) Q_DECL_OVERRIDE;
+    QPrintEngine *createNativePrintEngine(QPrinter::PrinterMode printerMode, const QString &deviceId = QString()) Q_DECL_OVERRIDE;
     QPaintEngine *createPaintEngine(QPrintEngine *, QPrinter::PrinterMode printerMode) Q_DECL_OVERRIDE;
 
     QPrintDevice createPrintDevice(const QString &id) Q_DECL_OVERRIDE;
diff --git a/src/plugins/platforms/cocoa/qcocoaprintersupport.mm b/src/plugins/platforms/cocoa/qcocoaprintersupport.mm
index c2f7d5b022..d7eaa469fb 100644
--- a/src/plugins/platforms/cocoa/qcocoaprintersupport.mm
+++ b/src/plugins/platforms/cocoa/qcocoaprintersupport.mm
@@ -54,9 +54,9 @@ QCocoaPrinterSupport::QCocoaPrinterSupport()
 QCocoaPrinterSupport::~QCocoaPrinterSupport()
 { }
 
-QPrintEngine *QCocoaPrinterSupport::createNativePrintEngine(QPrinter::PrinterMode printerMode)
+QPrintEngine *QCocoaPrinterSupport::createNativePrintEngine(QPrinter::PrinterMode printerMode, const QString &deviceId)
 {
-    return new QMacPrintEngine(printerMode);
+    return new QMacPrintEngine(printerMode, deviceId);
 }
 
 QPaintEngine *QCocoaPrinterSupport::createPaintEngine(QPrintEngine *printEngine, QPrinter::PrinterMode printerMode)
diff --git a/src/plugins/platforms/cocoa/qnsview.h b/src/plugins/platforms/cocoa/qnsview.h
index 414c6b7fe7..dcf8cf677a 100644
--- a/src/plugins/platforms/cocoa/qnsview.h
+++ b/src/plugins/platforms/cocoa/qnsview.h
@@ -126,9 +126,11 @@ Q_FORWARD_DECLARE_OBJC_CLASS(QT_MANGLE_NAMESPACE(QNSViewMouseMoveHelper));
 - (void)otherMouseUp:(NSEvent *)theEvent;
 - (void)handleFrameStrutMouseEvent:(NSEvent *)theEvent;
 
+#ifndef QT_NO_TABLETEVENT
 - (bool)handleTabletEvent: (NSEvent *)theEvent;
 - (void)tabletPoint: (NSEvent *)theEvent;
 - (void)tabletProximity: (NSEvent *)theEvent;
+#endif
 
 - (int) convertKeyCode : (QChar)keyCode;
 + (Qt::KeyboardModifiers) convertKeyModifiers : (ulong)modifierFlags;
diff --git a/src/plugins/platforms/cocoa/qnsview.mm b/src/plugins/platforms/cocoa/qnsview.mm
index 8d3cb6cc05..924173b4c5 100644
--- a/src/plugins/platforms/cocoa/qnsview.mm
+++ b/src/plugins/platforms/cocoa/qnsview.mm
@@ -511,10 +511,12 @@ static QTouchDevice *touchDevice = 0;
     if (!m_platformWindow)
         return;
 
+#ifndef QT_NO_TABLETEVENT
     // Tablet events may come in via the mouse event handlers,
     // check if this is a valid tablet event first.
     if ([self handleTabletEvent: theEvent])
         return;
+#endif
 
     QPointF qtWindowPoint;
     QPointF qtScreenPoint;
@@ -902,6 +904,7 @@ static QTouchDevice *touchDevice = 0;
     m_platformWindow->m_enterLeaveTargetWindow = 0;
 }
 
+#ifndef QT_NO_TABLETEVENT
 struct QCocoaTabletDeviceData
 {
     QTabletEvent::TabletDevice device;
@@ -1072,6 +1075,7 @@ static QTabletEvent::TabletDevice wacomTabletDevice(NSEvent *theEvent)
         QWindowSystemInterface::handleTabletLeaveProximityEvent(timestamp, deviceData.device, deviceData.pointerType, deviceData.uid);
     }
 }
+#endif
 
 - (bool)shouldSendSingleTouch
 {
diff --git a/src/plugins/platforms/cocoa/qprintengine_mac.mm b/src/plugins/platforms/cocoa/qprintengine_mac.mm
index 8098c5e829..c39af870d4 100644
--- a/src/plugins/platforms/cocoa/qprintengine_mac.mm
+++ b/src/plugins/platforms/cocoa/qprintengine_mac.mm
@@ -51,11 +51,15 @@ QT_BEGIN_NAMESPACE
 
 extern QMarginsF qt_convertMargins(const QMarginsF &margins, QPageLayout::Unit fromUnits, QPageLayout::Unit toUnits);
 
-QMacPrintEngine::QMacPrintEngine(QPrinter::PrinterMode mode) : QPaintEngine(*(new QMacPrintEnginePrivate))
+QMacPrintEngine::QMacPrintEngine(QPrinter::PrinterMode mode, const QString &deviceId)
+    : QPaintEngine(*(new QMacPrintEnginePrivate))
 {
     Q_D(QMacPrintEngine);
     d->mode = mode;
-    d->m_printDevice.reset(new QCocoaPrintDevice(QCocoaPrinterSupport().defaultPrintDeviceId()));
+    QString id = deviceId;
+    if (id.isEmpty())
+        id = QCocoaPrinterSupport().defaultPrintDeviceId();
+    d->m_printDevice.reset(new QCocoaPrintDevice(id));
     d->m_pageLayout.setPageSize(d->m_printDevice->defaultPageSize());
     d->initialize();
 }
diff --git a/src/plugins/platforms/cocoa/qprintengine_mac_p.h b/src/plugins/platforms/cocoa/qprintengine_mac_p.h
index ee98275b63..2d46a250d5 100644
--- a/src/plugins/platforms/cocoa/qprintengine_mac_p.h
+++ b/src/plugins/platforms/cocoa/qprintengine_mac_p.h
@@ -78,7 +78,7 @@ class QMacPrintEngine : public QPaintEngine, public QPrintEngine
 {
     Q_DECLARE_PRIVATE(QMacPrintEngine)
 public:
-    QMacPrintEngine(QPrinter::PrinterMode mode);
+    QMacPrintEngine(QPrinter::PrinterMode mode, const QString &deviceId);
 
     Qt::HANDLE handle() const;
 
diff --git a/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms/qeglfskmsgbmcursor.cpp b/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms/qeglfskmsgbmcursor.cpp
index a3868fdb1d..800118362d 100644
--- a/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms/qeglfskmsgbmcursor.cpp
+++ b/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms/qeglfskmsgbmcursor.cpp
@@ -240,6 +240,8 @@ void QEglFSKmsGbmCursor::setPos(const QPoint &pos)
             m_pos = pos;
         else
             qWarning("Failed to move cursor on screen %s: %d", kmsScreen->name().toLatin1().constData(), ret);
+
+        kmsScreen->handleCursorMove(pos);
     }
 }
 
diff --git a/src/plugins/platforms/ios/qiosbackingstore.h b/src/plugins/platforms/ios/qiosbackingstore.h
index 1c072c0935..3954347471 100644
--- a/src/plugins/platforms/ios/qiosbackingstore.h
+++ b/src/plugins/platforms/ios/qiosbackingstore.h
@@ -54,19 +54,10 @@ public:
     QIOSBackingStore(QWindow *window);
     ~QIOSBackingStore();
 
-    QPaintDevice *paintDevice() Q_DECL_OVERRIDE;
-
-    void beginPaint(const QRegion &) Q_DECL_OVERRIDE;
-    void endPaint() Q_DECL_OVERRIDE;
-
     void flush(QWindow *window, const QRegion &region, const QPoint &offset) Q_DECL_OVERRIDE;
-    void resize(const QSize &size, const QRegion &staticContents) Q_DECL_OVERRIDE;
-
-    void makeCurrent();
 
 private:
     QOpenGLContext *m_context;
-    QOpenGLPaintDevice *m_glDevice;
 };
 
 QT_END_NAMESPACE
diff --git a/src/plugins/platforms/ios/qiosbackingstore.mm b/src/plugins/platforms/ios/qiosbackingstore.mm
index 96be28af81..74229684e3 100644
--- a/src/plugins/platforms/ios/qiosbackingstore.mm
+++ b/src/plugins/platforms/ios/qiosbackingstore.mm
@@ -41,79 +41,31 @@
 #include "qioswindow.h"
 
 #include <QtGui/QOpenGLContext>
-#include <QtGui/QOpenGLPaintDevice>
-#include <QtGui/QOpenGLFramebufferObject>
-#include <QtGui/QOffscreenSurface>
-#include <QtGui/qpainter.h>
 #include <QtGui/private/qwindow_p.h>
 
 #include <QtDebug>
 
 QT_BEGIN_NAMESPACE
 
-class QIOSPaintDevice : public QOpenGLPaintDevice
-{
-public:
-    QIOSPaintDevice(QIOSBackingStore *backingStore) : m_backingStore(backingStore) { }
-    void ensureActiveTarget() Q_DECL_OVERRIDE;
-
-private:
-    QIOSBackingStore *m_backingStore;
-};
-
-void QIOSPaintDevice::ensureActiveTarget()
-{
-    m_backingStore->makeCurrent();
-}
-
 /*!
     \class QIOSBackingStore
 
-    \brief The QPlatformBackingStore on iOS.
-
     QBackingStore enables the use of QPainter to paint on a QWindow, as opposed
     to rendering to a QWindow through the use of OpenGL with QOpenGLContext.
-
-    Historically, the iOS port initially implemented the backing store by using
-    an QOpenGLPaintDevice as its paint device, triggering the use of the OpenGL
-    paint engine for QPainter based drawing. This was due to raster drawing
-    operations being too slow when not being NEON-optimized, and got the port
-    up and running quickly.
-
-    As of 3e892e4a97, released in Qt 5.7, the backing store now uses a QImage,
-    for its paint device, giving normal raster-based QPainter operations, and
-    enabling features such as antialiased drawing.
-
-    To account for regressions in performance, the old code path is still
-    available by setting the surface type of the QWindow to OpenGLSurface.
-    This surface type is normally used when rendering though QOpenGLContext,
-    but will in the case of QIOSBackingStore trigger the old OpenGL based
-    painter.
-
-    This fallback path is not too intrusive, as the QImage based path still
-    uses OpenGL to composite the image at flush() time using composeAndFlush.
 */
 QIOSBackingStore::QIOSBackingStore(QWindow *window)
     : QRasterBackingStore(window)
     , m_context(new QOpenGLContext)
-    , m_glDevice(nullptr)
 {
-    QSurfaceFormat fmt = window->requestedFormat();
-
-    // Due to sharing QIOSContext redirects our makeCurrent on window() attempts to
-    // the global share context. Hence it is essential to have a compatible format.
-    fmt.setDepthBufferSize(QSurfaceFormat::defaultFormat().depthBufferSize());
-    fmt.setStencilBufferSize(QSurfaceFormat::defaultFormat().stencilBufferSize());
-
-    if (fmt.depthBufferSize() == 0)
-        qWarning("No depth in default format, expect rendering errors");
-
     // We use the surface both for raster operations and for GL drawing (when
     // we blit the raster image), so the type needs to cover both use cases.
     if (window->surfaceType() == QSurface::RasterSurface)
         window->setSurfaceType(QSurface::RasterGLSurface);
 
-    m_context->setFormat(fmt);
+    Q_ASSERT_X(window->surfaceType() != QSurface::OpenGLSurface, "QIOSBackingStore",
+        "QBackingStore on iOS can only be used with raster-enabled surfaces.");
+
+    m_context->setFormat(window->requestedFormat());
     m_context->setScreen(window->screen());
     Q_ASSERT(QOpenGLContext::globalShareContext());
     m_context->setShareContext(QOpenGLContext::globalShareContext());
@@ -122,54 +74,12 @@ QIOSBackingStore::QIOSBackingStore(QWindow *window)
 
 QIOSBackingStore::~QIOSBackingStore()
 {
-    if (window()->surfaceType() == QSurface::RasterGLSurface) {
-        // We're using composeAndFlush from QPlatformBackingStore, which
-        // need to clean up any textures in its destructor, so make the
-        // context current and keep it alive until QPlatformBackingStore
-        // has cleaned up everything.
-        makeCurrent();
-        m_context->deleteLater();
-    } else {
-        delete m_context;
-    }
-
-    delete m_glDevice;
-}
-
-void QIOSBackingStore::makeCurrent()
-{
-    if (!m_context->makeCurrent(window()))
-        qWarning("QIOSBackingStore: makeCurrent() failed");
-}
-
-void QIOSBackingStore::beginPaint(const QRegion &region)
-{
-    makeCurrent();
-
-    if (!m_glDevice)
-        m_glDevice = new QIOSPaintDevice(this);
-
-    if (window()->surfaceType() == QSurface::RasterGLSurface)
-        QRasterBackingStore::beginPaint(region);
-}
-
-void QIOSBackingStore::endPaint()
-{
-}
-
-QPaintDevice *QIOSBackingStore::paintDevice()
-{
-    Q_ASSERT(m_glDevice);
-
-    // Keep paint device size and device pixel ratio in sync with window
-    qreal devicePixelRatio = window()->devicePixelRatio();
-    m_glDevice->setSize(window()->size() * devicePixelRatio);
-    m_glDevice->setDevicePixelRatio(devicePixelRatio);
-
-    if (window()->surfaceType() == QSurface::RasterGLSurface)
-        return QRasterBackingStore::paintDevice();
-    else
-        return m_glDevice;
+    // We're using composeAndFlush from QPlatformBackingStore, which
+    // need to clean up any textures in its destructor, so make the
+    // context current and keep it alive until QPlatformBackingStore
+    // has cleaned up everything.
+    m_context->makeCurrent(window());
+    m_context->deleteLater();
 }
 
 void QIOSBackingStore::flush(QWindow *window, const QRegion &region, const QPoint &offset)
@@ -187,33 +97,8 @@ void QIOSBackingStore::flush(QWindow *window, const QRegion &region, const QPoin
         return;
     }
 
-    if (window->surfaceType() == QSurface::RasterGLSurface) {
-        static QPlatformTextureList emptyTextureList;
-        composeAndFlush(window, region, offset, &emptyTextureList, m_context, false);
-    } else {
-        m_context->makeCurrent(window);
-        m_context->swapBuffers(window);
-    }
-}
-
-void QIOSBackingStore::resize(const QSize &size, const QRegion &staticContents)
-{
-    Q_UNUSED(staticContents);
-
-    if (window()->surfaceType() == QSurface::OpenGLSurface) {
-        // Resizing the backing store would in this case mean resizing the QWindow,
-        // as we use an QOpenGLPaintDevice that we target at the window. That's
-        // probably not what the user intended, so we ignore resizes of the backing
-        // store and always keep the paint device's size in sync with the window
-        // size in beginPaint().
-
-        if (size != window()->size() && !window()->inherits("QWidgetWindow"))
-            qWarning("QIOSBackingStore needs to have the same size as its window");
-
-        return;
-    }
-
-    QRasterBackingStore::resize(size, staticContents);
+    static QPlatformTextureList emptyTextureList;
+    composeAndFlush(window, region, offset, &emptyTextureList, m_context, false);
 }
 
 QT_END_NAMESPACE
diff --git a/src/plugins/platforms/ios/qiosintegration.mm b/src/plugins/platforms/ios/qiosintegration.mm
index 5c42828885..482f996943 100644
--- a/src/plugins/platforms/ios/qiosintegration.mm
+++ b/src/plugins/platforms/ios/qiosintegration.mm
@@ -97,11 +97,6 @@ QIOSIntegration::QIOSIntegration()
     // The backingstore needs a global share context in order to support composition in
     // QPlatformBackingStore.
     qApp->setAttribute(Qt::AA_ShareOpenGLContexts, true);
-    // And that context must match the format used for the backingstore's context.
-    QSurfaceFormat fmt = QSurfaceFormat::defaultFormat();
-    fmt.setDepthBufferSize(16);
-    fmt.setStencilBufferSize(8);
-    QSurfaceFormat::setDefaultFormat(fmt);
 
     // Set current directory to app bundle folder
     QDir::setCurrent(QString::fromUtf8([[[NSBundle mainBundle] bundlePath] UTF8String]));
diff --git a/src/plugins/platforms/windows/qwindowswindow.cpp b/src/plugins/platforms/windows/qwindowswindow.cpp
index 3e445f0f7f..3f417fde27 100644
--- a/src/plugins/platforms/windows/qwindowswindow.cpp
+++ b/src/plugins/platforms/windows/qwindowswindow.cpp
@@ -896,8 +896,10 @@ void QWindowsBaseWindow::hide_sys() // Normal hide, do not activate other window
 void QWindowsBaseWindow::raise_sys()
 {
     qCDebug(lcQpaWindows) << __FUNCTION__ << this << window();
-    if ((window()->flags() & (Qt::WindowStaysOnTopHint | Qt::WindowStaysOnBottomHint)) == 0)
+    if (window()->type() == Qt::Popup
+        || (window()->flags() & (Qt::WindowStaysOnTopHint | Qt::WindowStaysOnBottomHint)) == 0) {
         SetWindowPos(handle(), HWND_TOP, 0, 0, 0, 0, SWP_NOACTIVATE | SWP_NOMOVE | SWP_NOSIZE);
+    }
 }
 
 void QWindowsBaseWindow::lower_sys()
diff --git a/src/plugins/platforms/winrt/winrt.pro b/src/plugins/platforms/winrt/winrt.pro
index 02a848b03f..042b270cff 100644
--- a/src/plugins/platforms/winrt/winrt.pro
+++ b/src/plugins/platforms/winrt/winrt.pro
@@ -8,7 +8,7 @@ QT += \
 
 DEFINES *= QT_NO_CAST_FROM_ASCII __WRL_NO_DEFAULT_LIB__
 
-LIBS += $$QMAKE_LIBS_CORE -ld3d11
+LIBS += -lws2_32 -ld3d11
 
 SOURCES = \
     main.cpp  \
diff --git a/src/plugins/platforms/xcb/qxcbconnection.cpp b/src/plugins/platforms/xcb/qxcbconnection.cpp
index 23bb5c6410..536c709dbe 100644
--- a/src/plugins/platforms/xcb/qxcbconnection.cpp
+++ b/src/plugins/platforms/xcb/qxcbconnection.cpp
@@ -556,9 +556,10 @@ QXcbConnection::QXcbConnection(QXcbNativeInterface *nativeInterface, bool canGra
     m_connection = xcb_connect(m_displayName.constData(), &m_primaryScreenNumber);
 #endif // QT_CONFIG(xcb_xlib)
 
-    if (Q_UNLIKELY(!m_connection || xcb_connection_has_error(m_connection)))
-        qFatal("QXcbConnection: Could not connect to display %s", m_displayName.constData());
-
+    if (Q_UNLIKELY(!m_connection || xcb_connection_has_error(m_connection))) {
+        qCWarning(lcQpaScreen, "QXcbConnection: Could not connect to display %s", m_displayName.constData());
+        return;
+    }
 
     m_reader = new QXcbEventReader(this);
     m_reader->start();
@@ -648,7 +649,7 @@ QXcbConnection::~QXcbConnection()
 #ifndef QT_NO_DRAGANDDROP
     delete m_drag;
 #endif
-    if (m_reader->isRunning()) {
+    if (m_reader && m_reader->isRunning()) {
         sendConnectionEvent(QXcbAtom::_QT_CLOSE_CONNECTION);
         m_reader->wait();
     }
@@ -665,15 +666,22 @@ QXcbConnection::~QXcbConnection()
 
     delete m_glIntegration;
 
+    if (isConnected()) {
 #if QT_CONFIG(xcb_xlib)
-    XCloseDisplay(static_cast<Display *>(m_xlib_display));
+        XCloseDisplay(static_cast<Display *>(m_xlib_display));
 #else
-    xcb_disconnect(xcb_connection());
+        xcb_disconnect(xcb_connection());
 #endif
+    }
 
     delete m_keyboard;
 }
 
+bool QXcbConnection::isConnected() const
+{
+    return m_connection && !xcb_connection_has_error(m_connection);
+}
+
 QXcbScreen *QXcbConnection::primaryScreen() const
 {
     if (!m_screens.isEmpty()) {
diff --git a/src/plugins/platforms/xcb/qxcbconnection.h b/src/plugins/platforms/xcb/qxcbconnection.h
index a37ce5f5a6..999dc0630c 100644
--- a/src/plugins/platforms/xcb/qxcbconnection.h
+++ b/src/plugins/platforms/xcb/qxcbconnection.h
@@ -391,6 +391,7 @@ public:
     ~QXcbConnection();
 
     QXcbConnection *connection() const { return const_cast<QXcbConnection *>(this); }
+    bool isConnected() const;
 
     const QList<QXcbVirtualDesktop *> &virtualDesktops() const { return m_virtualDesktops; }
     const QList<QXcbScreen *> &screens() const { return m_screens; }
diff --git a/src/plugins/platforms/xcb/qxcbintegration.cpp b/src/plugins/platforms/xcb/qxcbintegration.cpp
index c8efe2fce8..72d31060db 100644
--- a/src/plugins/platforms/xcb/qxcbintegration.cpp
+++ b/src/plugins/platforms/xcb/qxcbintegration.cpp
@@ -188,12 +188,25 @@ QXcbIntegration::QXcbIntegration(const QStringList &parameters, int &argc, char
 
     const int numParameters = parameters.size();
     m_connections.reserve(1 + numParameters / 2);
-    m_connections << new QXcbConnection(m_nativeInterface.data(), m_canGrab, m_defaultVisualId, displayName);
+    auto conn = new QXcbConnection(m_nativeInterface.data(), m_canGrab, m_defaultVisualId, displayName);
+    if (conn->isConnected())
+        m_connections << conn;
+    else
+        delete conn;
 
     for (int i = 0; i < numParameters - 1; i += 2) {
         qCDebug(lcQpaScreen) << "connecting to additional display: " << parameters.at(i) << parameters.at(i+1);
         QString display = parameters.at(i) + QLatin1Char(':') + parameters.at(i+1);
-        m_connections << new QXcbConnection(m_nativeInterface.data(), m_canGrab, m_defaultVisualId, display.toLatin1().constData());
+        conn = new QXcbConnection(m_nativeInterface.data(), m_canGrab, m_defaultVisualId, display.toLatin1().constData());
+        if (conn->isConnected())
+            m_connections << conn;
+        else
+            delete conn;
+    }
+
+    if (m_connections.isEmpty()) {
+        qCritical("Could not connect to any X display.");
+        exit(1);
     }
 
     m_fontDatabase.reset(new QGenericUnixFontDatabase());