Merge remote-tracking branch 'origin/5.11.1' into 5.11

Change-Id: I9a4571ccf826a86e055dfbba23b5e5cbd8ea55e8

18 files changed, 215 insertions, 126 deletions

diff --git a/src/plugins/platforms/cocoa/qnswindowdelegate.mm b/src/plugins/platforms/cocoa/qnswindowdelegate.mm
index 15c141448d..057a4c2943 100644
--- a/src/plugins/platforms/cocoa/qnswindowdelegate.mm
+++ b/src/plugins/platforms/cocoa/qnswindowdelegate.mm
@@ -69,25 +69,38 @@ static QRegExp whitespaceRegex = QRegExp(QStringLiteral("\\s*"));
 /*!
     Overridden to ensure that the zoomed state always results in a maximized
     window, which would otherwise not be the case for borderless windows.
+
+    We also keep the window on the same screen as before; something AppKit
+    sometimes fails to do using its built in logic.
 */
 - (NSRect)windowWillUseStandardFrame:(NSWindow *)window defaultFrame:(NSRect)proposedFrame
 {
     Q_UNUSED(proposedFrame);
     Q_ASSERT(window == m_cocoaWindow->nativeWindow());
-
-    // We compute the maximized state based on the maximum size, and
-    // the current position of the window. This may result in the window
-    // geometry falling outside of the current screen's available geometry,
-    // e.g. when there is not maximize size set, but this is okey, AppKit
-    // will then shift and possibly clip the geometry for us.
     const QWindow *w = m_cocoaWindow->window();
-    QRect maximizedRect = QRect(w->framePosition(), w->maximumSize());
 
-    // QWindow::maximumSize() refers to the client size,
-    // but AppKit expects the full frame size.
-    maximizedRect.adjust(0, 0, 0, w->frameMargins().top());
+    // maximumSize() refers to the client size, but AppKit expects the full frame size
+    QSizeF maximumSize = w->maximumSize() + QSize(0, w->frameMargins().top());
+
+    // The window should never be larger than the current screen geometry
+    const QRectF screenGeometry = m_cocoaWindow->screen()->geometry();
+    maximumSize = maximumSize.boundedTo(screenGeometry.size());
+
+    // Use the current frame position for the initial maximized frame,
+    // so that the window stays put and just expand, in case its maximum
+    // size is within the screen bounds.
+    QRectF maximizedFrame = QRectF(w->framePosition(), maximumSize);
+
+    // But constrain the frame to the screen bounds in case the frame
+    // extends beyond the screen bounds as a result of starting out
+    // with the current frame position.
+    maximizedFrame.translate(QPoint(
+        qMax(screenGeometry.left() - maximizedFrame.left(), 0.0) +
+        qMin(screenGeometry.right() - maximizedFrame.right(), 0.0),
+        qMax(screenGeometry.top() - maximizedFrame.top(), 0.0) +
+        qMin(screenGeometry.bottom() - maximizedFrame.bottom(), 0.0)));
 
-    return QCocoaScreen::mapToNative(maximizedRect);
+    return QCocoaScreen::mapToNative(maximizedFrame);
 }
 
 - (BOOL)window:(NSWindow *)window shouldPopUpDocumentPathMenu:(NSMenu *)menu
diff --git a/src/plugins/platforms/ios/kernel.pro b/src/plugins/platforms/ios/kernel.pro
index 6eb9f2c534..71257d09f7 100644
--- a/src/plugins/platforms/ios/kernel.pro
+++ b/src/plugins/platforms/ios/kernel.pro
@@ -5,8 +5,6 @@ TARGET = qios
 # application's main() when the plugin is a shared library.
 qtConfig(shared): CONFIG += static
 
-CONFIG += no_app_extension_api_only
-
 QT += \
     core-private gui-private \
     clipboard_support-private fontdatabase_support-private graphics_support-private
diff --git a/src/plugins/platforms/ios/qiosapplicationstate.mm b/src/plugins/platforms/ios/qiosapplicationstate.mm
index cc76d198f5..bf4e9cc900 100644
--- a/src/plugins/platforms/ios/qiosapplicationstate.mm
+++ b/src/plugins/platforms/ios/qiosapplicationstate.mm
@@ -86,7 +86,7 @@ static void qRegisterApplicationStateNotifications()
             QLatin1String("Extension loaded, assuming state is active"));
     } else {
         // Initialize correct startup state, which may not be the Qt default (inactive)
-        UIApplicationState startupState = [UIApplication sharedApplication].applicationState;
+        UIApplicationState startupState = qt_apple_sharedApplication().applicationState;
         QIOSApplicationState::handleApplicationStateChanged(startupState, QLatin1String("Application loaded"));
     }
 }
@@ -95,7 +95,7 @@ Q_CONSTRUCTOR_FUNCTION(qRegisterApplicationStateNotifications)
 QIOSApplicationState::QIOSApplicationState()
 {
     if (!qt_apple_isApplicationExtension()) {
-        UIApplicationState startupState = [UIApplication sharedApplication].applicationState;
+        UIApplicationState startupState = qt_apple_sharedApplication().applicationState;
         QIOSApplicationState::handleApplicationStateChanged(startupState, QLatin1String("Application launched"));
     }
 }
diff --git a/src/plugins/platforms/ios/qiosfiledialog.mm b/src/plugins/platforms/ios/qiosfiledialog.mm
index 5987bc1540..e8a3f5b30e 100644
--- a/src/plugins/platforms/ios/qiosfiledialog.mm
+++ b/src/plugins/platforms/ios/qiosfiledialog.mm
@@ -43,6 +43,8 @@
 #include <QtGui/qwindow.h>
 #include <QDebug>
 
+#include <QtCore/private/qcore_mac_p.h>
+
 #include "qiosfiledialog.h"
 #include "qiosintegration.h"
 #include "qiosoptionalplugininterface.h"
@@ -94,7 +96,7 @@ bool QIOSFileDialog::showImagePickerDialog(QWindow *parent)
     }
 
     UIWindow *window = parent ? reinterpret_cast<UIView *>(parent->winId()).window
-        : [UIApplication sharedApplication].keyWindow;
+        : qt_apple_sharedApplication().keyWindow;
     [window.rootViewController presentViewController:m_viewController animated:YES completion:nil];
 
     return true;
diff --git a/src/plugins/platforms/ios/qiosglobal.mm b/src/plugins/platforms/ios/qiosglobal.mm
index f27b2242df..a523d1be45 100644
--- a/src/plugins/platforms/ios/qiosglobal.mm
+++ b/src/plugins/platforms/ios/qiosglobal.mm
@@ -42,6 +42,8 @@
 #include "qiosviewcontroller.h"
 #include "qiosscreen.h"
 
+#include <QtCore/private/qcore_mac_p.h>
+
 QT_BEGIN_NAMESPACE
 
 Q_LOGGING_CATEGORY(lcQpaApplication, "qt.qpa.application");
@@ -50,13 +52,16 @@ Q_LOGGING_CATEGORY(lcQpaWindow, "qt.qpa.window");
 
 bool isQtApplication()
 {
+    if (qt_apple_isApplicationExtension())
+        return false;
+
     // Returns \c true if the plugin is in full control of the whole application. This means
     // that we control the application delegate and the top view controller, and can take
     // actions that impacts all parts of the application. The opposite means that we are
     // embedded inside a native iOS application, and should be more focused on playing along
     // with native UIControls, and less inclined to change structures that lies outside the
     // scope of our QWindows/UIViews.
-    static bool isQt = ([[UIApplication sharedApplication].delegate isKindOfClass:[QIOSApplicationDelegate class]]);
+    static bool isQt = ([qt_apple_sharedApplication().delegate isKindOfClass:[QIOSApplicationDelegate class]]);
     return isQt;
 }
 
@@ -152,8 +157,13 @@ QT_END_NAMESPACE
 
 + (id)currentFirstResponder
 {
+    if (qt_apple_isApplicationExtension()) {
+        qWarning() << "can't get first responder in application extensions!";
+        return nil;
+    }
+
     QtFirstResponderEvent *event = [[[QtFirstResponderEvent alloc] init] autorelease];
-    [[UIApplication sharedApplication] sendAction:@selector(qt_findFirstResponder:event:) to:nil from:nil forEvent:event];
+    [qt_apple_sharedApplication() sendAction:@selector(qt_findFirstResponder:event:) to:nil from:nil forEvent:event];
     return event.firstResponder;
 }
 
diff --git a/src/plugins/platforms/ios/qiosinputcontext.mm b/src/plugins/platforms/ios/qiosinputcontext.mm
index 050c592aca..493c283ec1 100644
--- a/src/plugins/platforms/ios/qiosinputcontext.mm
+++ b/src/plugins/platforms/ios/qiosinputcontext.mm
@@ -49,6 +49,8 @@
 #include "qioswindow.h"
 #include "quiview.h"
 
+#include <QtCore/private/qcore_mac_p.h>
+
 #include <QGuiApplication>
 #include <QtGui/private/qwindow_p.h>
 
@@ -536,6 +538,11 @@ void QIOSInputContext::scroll(int y)
     if (!rootView)
         return;
 
+    if (qt_apple_isApplicationExtension()) {
+        qWarning() << "can't scroll root view in application extension";
+        return;
+    }
+
     CATransform3D translationTransform = CATransform3DMakeTranslation(0.0, -y, 0.0);
     if (CATransform3DEqualToTransform(translationTransform, rootView.layer.sublayerTransform))
         return;
@@ -574,7 +581,7 @@ void QIOSInputContext::scroll(int y)
 
             // Raise all known windows to above the status-bar if we're scrolling the screen,
             // while keeping the relative window level between the windows the same.
-            NSArray *applicationWindows = [[UIApplication sharedApplication] windows];
+            NSArray *applicationWindows = [qt_apple_sharedApplication() windows];
             static QHash<UIWindow *, UIWindowLevel> originalWindowLevels;
             for (UIWindow *window in applicationWindows) {
                 if (keyboardScrollIsActive && !originalWindowLevels.contains(window))
diff --git a/src/plugins/platforms/ios/qiosintegration.mm b/src/plugins/platforms/ios/qiosintegration.mm
index b8ce49aaca..ed2bfbc0d8 100644
--- a/src/plugins/platforms/ios/qiosintegration.mm
+++ b/src/plugins/platforms/ios/qiosintegration.mm
@@ -86,7 +86,7 @@ QIOSIntegration::QIOSIntegration()
     , m_accessibility(0)
     , m_optionalPlugins(new QFactoryLoader(QIosOptionalPluginInterface_iid, QLatin1String("/platforms/darwin")))
 {
-    if (Q_UNLIKELY(![UIApplication sharedApplication])) {
+    if (Q_UNLIKELY(!qt_apple_isApplicationExtension() && !qt_apple_sharedApplication())) {
         qFatal("Error: You are creating QApplication before calling UIApplicationMain.\n" \
                "If you are writing a native iOS application, and only want to use Qt for\n" \
                "parts of the application, a good place to create QApplication is from within\n" \
diff --git a/src/plugins/platforms/ios/qiosmessagedialog.mm b/src/plugins/platforms/ios/qiosmessagedialog.mm
index 9d05b792c2..a7de9b473a 100644
--- a/src/plugins/platforms/ios/qiosmessagedialog.mm
+++ b/src/plugins/platforms/ios/qiosmessagedialog.mm
@@ -43,6 +43,8 @@
 #include <QtGui/private/qguiapplication_p.h>
 #include <qpa/qplatformtheme.h>
 
+#include <QtCore/private/qcore_mac_p.h>
+
 #include "qiosglobal.h"
 #include "quiview.h"
 #include "qiosmessagedialog.h"
@@ -126,7 +128,7 @@ bool QIOSMessageDialog::show(Qt::WindowFlags windowFlags, Qt::WindowModality win
         [m_alertController addAction:createAction(NoButton)];
     }
 
-    UIWindow *window = parent ? reinterpret_cast<UIView *>(parent->winId()).window : [UIApplication sharedApplication].keyWindow;
+    UIWindow *window = parent ? reinterpret_cast<UIView *>(parent->winId()).window : qt_apple_sharedApplication().keyWindow;
     [window.rootViewController presentViewController:m_alertController animated:YES completion:nil];
     return true;
 }
diff --git a/src/plugins/platforms/ios/qiosscreen.mm b/src/plugins/platforms/ios/qiosscreen.mm
index c394592d76..f367d1e75e 100644
--- a/src/plugins/platforms/ios/qiosscreen.mm
+++ b/src/plugins/platforms/ios/qiosscreen.mm
@@ -46,6 +46,8 @@
 #include "qiosviewcontroller.h"
 #include "quiview.h"
 
+#include <QtCore/private/qcore_mac_p.h>
+
 #include <QtGui/private/qwindow_p.h>
 #include <private/qcoregraphics_p.h>
 
@@ -271,17 +273,19 @@ QIOSScreen::QIOSScreen(UIScreen *screen)
         m_physicalDpi = 96;
     }
 
-    for (UIWindow *existingWindow in [[UIApplication sharedApplication] windows]) {
-        if (existingWindow.screen == m_uiScreen) {
-            m_uiWindow = [m_uiWindow retain];
-            break;
+    if (!qt_apple_isApplicationExtension()) {
+        for (UIWindow *existingWindow in qt_apple_sharedApplication().windows) {
+            if (existingWindow.screen == m_uiScreen) {
+                m_uiWindow = [m_uiWindow retain];
+                break;
+            }
         }
-    }
 
-    if (!m_uiWindow) {
-        // Create a window and associated view-controller that we can use
-        m_uiWindow = [[QUIWindow alloc] initWithFrame:[m_uiScreen bounds]];
-        m_uiWindow.rootViewController = [[[QIOSViewController alloc] initWithQIOSScreen:this] autorelease];
+        if (!m_uiWindow) {
+            // Create a window and associated view-controller that we can use
+            m_uiWindow = [[QUIWindow alloc] initWithFrame:[m_uiScreen bounds]];
+            m_uiWindow.rootViewController = [[[QIOSViewController alloc] initWithQIOSScreen:this] autorelease];
+        }
     }
 
     updateProperties();
@@ -327,17 +331,20 @@ void QIOSScreen::updateProperties()
 
 #ifndef Q_OS_TVOS
     if (m_uiScreen == [UIScreen mainScreen]) {
-        Qt::ScreenOrientation statusBarOrientation = toQtScreenOrientation(UIDeviceOrientation([UIApplication sharedApplication].statusBarOrientation));
-
         QIOSViewController *qtViewController = [m_uiWindow.rootViewController isKindOfClass:[QIOSViewController class]] ?
             static_cast<QIOSViewController *>(m_uiWindow.rootViewController) : nil;
 
         if (qtViewController.lockedOrientation) {
+            Q_ASSERT(!qt_apple_isApplicationExtension());
+
             // Setting the statusbar orientation (content orientation) on will affect the screen geometry,
             // which is not what we want. We want to reflect the screen geometry based on the locked orientation,
             // and adjust the available geometry based on the repositioned status bar for the current status
             // bar orientation.
 
+            Qt::ScreenOrientation statusBarOrientation = toQtScreenOrientation(
+                UIDeviceOrientation(qt_apple_sharedApplication().statusBarOrientation));
+
             Qt::ScreenOrientation lockedOrientation = toQtScreenOrientation(UIDeviceOrientation(qtViewController.lockedOrientation));
             QTransform transform = transformBetween(lockedOrientation, statusBarOrientation, m_geometry).inverted();
 
@@ -487,8 +494,8 @@ Qt::ScreenOrientation QIOSScreen::orientation() const
     // the orientation the application was started up in (which may not match
     // the physical orientation of the device, but typically does unless the
     // application has been locked to a subset of the available orientations).
-    if (deviceOrientation == UIDeviceOrientationUnknown)
-        deviceOrientation = UIDeviceOrientation([UIApplication sharedApplication].statusBarOrientation);
+    if (deviceOrientation == UIDeviceOrientationUnknown && !qt_apple_isApplicationExtension())
+        deviceOrientation = UIDeviceOrientation(qt_apple_sharedApplication().statusBarOrientation);
 
     // If the device reports face up or face down orientations, we can't map
     // them to Qt orientations, so we pretend we're in the same orientation
diff --git a/src/plugins/platforms/ios/qiosservices.mm b/src/plugins/platforms/ios/qiosservices.mm
index 3c44e1d7d6..7222bf6793 100644
--- a/src/plugins/platforms/ios/qiosservices.mm
+++ b/src/plugins/platforms/ios/qiosservices.mm
@@ -40,6 +40,9 @@
 #include "qiosservices.h"
 
 #include <QtCore/qurl.h>
+#include <QtCore/qdebug.h>
+#include <QtCore/private/qcore_mac_p.h>
+
 #include <QtGui/qdesktopservices.h>
 
 #import <UIKit/UIApplication.h>
@@ -48,6 +51,11 @@ QT_BEGIN_NAMESPACE
 
 bool QIOSServices::openUrl(const QUrl &url)
 {
+    if (qt_apple_isApplicationExtension()) {
+        qWarning() << "openUrl not implement for application extensions yet";
+        return false;
+    }
+
     if (url == m_handlingUrl)
         return false;
 
@@ -55,12 +63,25 @@ bool QIOSServices::openUrl(const QUrl &url)
         return openDocument(url);
 
     NSURL *nsUrl = url.toNSURL();
-    UIApplication *application = [UIApplication sharedApplication];
+    UIApplication *application = qt_apple_sharedApplication();
 
     if (![application canOpenURL:nsUrl])
         return false;
 
-    [application openURL:nsUrl options:@{} completionHandler:nil];
+    static SEL openUrlSelector = @selector(openURL:options:completionHandler:);
+    NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:
+        [UIApplication instanceMethodSignatureForSelector:openUrlSelector]];
+    invocation.target = application;
+    invocation.selector = openUrlSelector;
+
+    static auto kEmptyDictionary = @{};
+    // Indices 0 and 1 are self and _cmd
+    [invocation setArgument:&nsUrl atIndex:2];
+    [invocation setArgument:&kEmptyDictionary atIndex:3];
+    // Fourth argument is nil, so left unset
+
+    [invocation invoke];
+
     return true;
 }
 
diff --git a/src/plugins/platforms/ios/qiostextinputoverlay.mm b/src/plugins/platforms/ios/qiostextinputoverlay.mm
index fe3c29d037..87c282e24a 100644
--- a/src/plugins/platforms/ios/qiostextinputoverlay.mm
+++ b/src/plugins/platforms/ios/qiostextinputoverlay.mm
@@ -46,6 +46,7 @@
 
 #include <QtGui/private/qinputmethod_p.h>
 #include <QtCore/private/qobject_p.h>
+#include <QtCore/private/qcore_mac_p.h>
 
 #include "qiosglobal.h"
 #include "qiostextinputoverlay.h"
@@ -475,7 +476,7 @@ static void executeBlockWithoutAnimation(Block block)
 
     if (enabled) {
         _focusView = [reinterpret_cast<UIView *>(qApp->focusWindow()->winId()) retain];
-        _desktopView = [[UIApplication sharedApplication].keyWindow.rootViewController.view retain];
+        _desktopView = [qt_apple_sharedApplication().keyWindow.rootViewController.view retain];
         Q_ASSERT(_focusView && _desktopView && _desktopView.superview);
         [_desktopView addGestureRecognizer:self];
     } else {
@@ -991,6 +992,11 @@ QIOSTextInputOverlay::QIOSTextInputOverlay()
     , m_selectionRecognizer(nullptr)
     , m_openMenuOnTapRecognizer(nullptr)
 {
+    if (qt_apple_isApplicationExtension()) {
+        qWarning() << "text input overlays disabled in application extensions";
+        return;
+    }
+
     connect(qApp, &QGuiApplication::focusObjectChanged, this, &QIOSTextInputOverlay::updateFocusObject);
 }
 
diff --git a/src/plugins/platforms/ios/qiostheme.mm b/src/plugins/platforms/ios/qiostheme.mm
index 91980d3f35..5534264a60 100644
--- a/src/plugins/platforms/ios/qiostheme.mm
+++ b/src/plugins/platforms/ios/qiostheme.mm
@@ -41,6 +41,7 @@
 
 #include <QtCore/QStringList>
 #include <QtCore/QVariant>
+#include <QtCore/private/qcore_mac_p.h>
 
 #include <QtGui/QFont>
 
@@ -103,7 +104,7 @@ bool QIOSTheme::usePlatformNativeDialog(QPlatformTheme::DialogType type) const
     switch (type) {
     case FileDialog:
     case MessageDialog:
-        return true;
+        return !qt_apple_isApplicationExtension();
     default:
         return false;
     }
diff --git a/src/plugins/platforms/ios/qiosviewcontroller.mm b/src/plugins/platforms/ios/qiosviewcontroller.mm
index d7db6ba856..aa909d6f63 100644
--- a/src/plugins/platforms/ios/qiosviewcontroller.mm
+++ b/src/plugins/platforms/ios/qiosviewcontroller.mm
@@ -41,6 +41,7 @@
 #import "qiosviewcontroller.h"
 
 #include <QtCore/qscopedvaluerollback.h>
+#include <QtCore/private/qcore_mac_p.h>
 
 #include <QtGui/QGuiApplication>
 #include <QtGui/QWindow>
@@ -307,15 +308,17 @@
 {
     [super viewDidLoad];
 
+    Q_ASSERT(!qt_apple_isApplicationExtension());
+
 #ifndef Q_OS_TVOS
     NSNotificationCenter *center = [NSNotificationCenter defaultCenter];
     [center addObserver:self selector:@selector(willChangeStatusBarFrame:)
             name:UIApplicationWillChangeStatusBarFrameNotification
-            object:[UIApplication sharedApplication]];
+            object:qt_apple_sharedApplication()];
 
     [center addObserver:self selector:@selector(didChangeStatusBarOrientation:)
             name:UIApplicationDidChangeStatusBarOrientationNotification
-            object:[UIApplication sharedApplication]];
+            object:qt_apple_sharedApplication()];
 #endif
 }
 
@@ -455,7 +458,6 @@
     focusWindow = qt_window_private(focusWindow)->topLevelWindow();
 
 #ifndef Q_OS_TVOS
-    UIApplication *uiApplication = [UIApplication sharedApplication];
 
     // -------------- Status bar style and visbility ---------------
 
@@ -479,6 +481,8 @@
 
     // -------------- Content orientation ---------------
 
+    UIApplication *uiApplication = qt_apple_sharedApplication();
+
     static BOOL kAnimateContentOrientationChanges = YES;
 
     Qt::ScreenOrientation contentOrientation = focusWindow->contentOrientation();
diff --git a/src/plugins/platforms/xcb/qxcbbackingstore.cpp b/src/plugins/platforms/xcb/qxcbbackingstore.cpp
index 8cfcc49f9a..b81cb8efa1 100644
--- a/src/plugins/platforms/xcb/qxcbbackingstore.cpp
+++ b/src/plugins/platforms/xcb/qxcbbackingstore.cpp
@@ -95,6 +95,9 @@ public:
     void put(xcb_drawable_t dst, const QRegion &region, const QPoint &offset);
     void preparePaint(const QRegion &region);
 
+    static bool createSystemVShmSegment(QXcbConnection *c, size_t segmentSize = 1,
+                                        xcb_shm_segment_info_t *shm_info = nullptr);
+
 private:
     void createShmSegment(size_t segmentSize);
     void destroyShmSegment(size_t segmentSize);
@@ -325,15 +328,16 @@ void QXcbBackingStoreImage::createShmSegment(size_t segmentSize)
 #ifdef XCB_USE_SHM_FD
     if (connection()->hasShmFd()) {
         if (Q_UNLIKELY(segmentSize > std::numeric_limits<uint32_t>::max())) {
-            qWarning("QXcbShmImage: xcb_shm_create_segment() can't be called for size %zu, maximum allowed size is %u",
-                     segmentSize, std::numeric_limits<uint32_t>::max());
+            qCWarning(lcQpaXcb, "xcb_shm_create_segment() can't be called for size %zu, maximum"
+                      "allowed size is %u", segmentSize, std::numeric_limits<uint32_t>::max());
             return;
         }
+
         const auto seg = xcb_generate_id(xcb_connection());
         auto reply = Q_XCB_REPLY(xcb_shm_create_segment,
                                  xcb_connection(), seg, segmentSize, false);
         if (!reply) {
-            qWarning("QXcbShmImage: xcb_shm_create_segment() failed for size %zu", segmentSize);
+            qCWarning(lcQpaXcb, "xcb_shm_create_segment() failed for size %zu", segmentSize);
             return;
         }
 
@@ -342,13 +346,13 @@ void QXcbBackingStoreImage::createShmSegment(size_t segmentSize)
             for (int i = 0; i < reply->nfd; i++)
                 close(fds[i]);
 
-            qWarning("QXcbShmImage: failed to get file descriptor for shm segment of size %zu", segmentSize);
+            qCWarning(lcQpaXcb, "failed to get file descriptor for shm segment of size %zu", segmentSize);
             return;
         }
 
         void *addr = mmap(nullptr, segmentSize, PROT_READ|PROT_WRITE, MAP_SHARED, fds[0], 0);
         if (addr == MAP_FAILED) {
-            qWarning("QXcbShmImage: failed to mmap segment from X server (%d: %s) for size %zu",
+            qCWarning(lcQpaXcb, "failed to mmap segment from X server (%d: %s) for size %zu",
                      errno, strerror(errno), segmentSize);
             close(fds[0]);
             xcb_shm_detach(xcb_connection(), seg);
@@ -358,47 +362,54 @@ void QXcbBackingStoreImage::createShmSegment(size_t segmentSize)
         close(fds[0]);
         m_shm_info.shmseg = seg;
         m_shm_info.shmaddr = static_cast<quint8 *>(addr);
-
         m_segmentSize = segmentSize;
     } else
 #endif
     {
-        const int id = shmget(IPC_PRIVATE, segmentSize, IPC_CREAT | 0600);
-        if (id == -1) {
-            qWarning("QXcbShmImage: shmget() failed (%d: %s) for size %zu",
-                     errno, strerror(errno), segmentSize);
-            return;
-        }
-
-        void *addr = shmat(id, 0, 0);
-        if (addr == (void *)-1) {
-            qWarning("QXcbShmImage: shmat() failed (%d: %s) for id %d",
-                     errno, strerror(errno), id);
-            return;
-        }
-
-        if (shmctl(id, IPC_RMID, 0) == -1)
-            qWarning("QXcbBackingStore: Error while marking the shared memory segment to be destroyed");
+        if (createSystemVShmSegment(connection(), segmentSize, &m_shm_info))
+            m_segmentSize = segmentSize;
+    }
+}
 
-        const auto seg = xcb_generate_id(xcb_connection());
-        auto cookie = xcb_shm_attach_checked(xcb_connection(), seg, id, false);
-        auto *error = xcb_request_check(xcb_connection(), cookie);
-        if (error) {
-            connection()->printXcbError("QXcbShmImage: xcb_shm_attach() failed with error", error);
-            free(error);
-            if (shmdt(addr) == -1) {
-                qWarning("QXcbShmImage: shmdt() failed (%d: %s) for %p",
-                         errno, strerror(errno), addr);
-            }
-            return;
-        }
+bool QXcbBackingStoreImage::createSystemVShmSegment(QXcbConnection *c, size_t segmentSize,
+                                                    xcb_shm_segment_info_t *shmInfo)
+{
+    const int id = shmget(IPC_PRIVATE, segmentSize, IPC_CREAT | 0600);
+    if (id == -1) {
+        qCWarning(lcQpaXcb, "shmget() failed (%d: %s) for size %zu", errno, strerror(errno), segmentSize);
+        return false;
+    }
 
-        m_shm_info.shmseg = seg;
-        m_shm_info.shmid = id; // unused
-        m_shm_info.shmaddr = static_cast<quint8 *>(addr);
+    void *addr = shmat(id, 0, 0);
+    if (addr == (void *)-1) {
+        qCWarning(lcQpaXcb, "shmat() failed (%d: %s) for id %d", errno, strerror(errno), id);
+        return false;
+    }
 
-        m_segmentSize = segmentSize;
+    if (shmctl(id, IPC_RMID, 0) == -1)
+        qCWarning(lcQpaXcb, "Error while marking the shared memory segment to be destroyed");
+
+    const auto seg = xcb_generate_id(c->xcb_connection());
+    auto cookie = xcb_shm_attach_checked(c->xcb_connection(), seg, id, false);
+    auto *error = xcb_request_check(c->xcb_connection(), cookie);
+    if (error) {
+        c->printXcbError("xcb_shm_attach() failed with error", error);
+        free(error);
+        if (shmdt(addr) == -1)
+            qCWarning(lcQpaXcb, "shmdt() failed (%d: %s) for %p", errno, strerror(errno), addr);
+        return false;
+    } else if (!shmInfo) { // this was a test run, free the allocated test segment
+        xcb_shm_detach(c->xcb_connection(), seg);
+        auto shmaddr = static_cast<quint8 *>(addr);
+        if (shmdt(shmaddr) == -1)
+            qCWarning(lcQpaXcb, "shmdt() failed (%d: %s) for %p", errno, strerror(errno), shmaddr);
+    }
+    if (shmInfo) {
+        shmInfo->shmseg = seg;
+        shmInfo->shmid = id; // unused
+        shmInfo->shmaddr = static_cast<quint8 *>(addr);
     }
+    return true;
 }
 
 void QXcbBackingStoreImage::destroyShmSegment(size_t segmentSize)
@@ -409,21 +420,21 @@ void QXcbBackingStoreImage::destroyShmSegment(size_t segmentSize)
     auto cookie = xcb_shm_detach_checked(xcb_connection(), m_shm_info.shmseg);
     xcb_generic_error_t *error = xcb_request_check(xcb_connection(), cookie);
     if (error)
-        connection()->printXcbError("QXcbShmImage: xcb_shm_detach() failed with error", error);
+        connection()->printXcbError("xcb_shm_detach() failed with error", error);
     m_shm_info.shmseg = 0;
 
 #ifdef XCB_USE_SHM_FD
     if (connection()->hasShmFd()) {
         if (munmap(m_shm_info.shmaddr, segmentSize) == -1) {
-            qWarning("QXcbShmImage: munmap() failed (%d: %s) for %p with size %zu",
-                     errno, strerror(errno), m_shm_info.shmaddr, segmentSize);
+            qCWarning(lcQpaXcb, "munmap() failed (%d: %s) for %p with size %zu",
+                      errno, strerror(errno), m_shm_info.shmaddr, segmentSize);
         }
     } else
 #endif
     {
         if (shmdt(m_shm_info.shmaddr) == -1) {
-            qWarning("QXcbShmImage: shmdt() failed (%d: %s) for %p",
-                     errno, strerror(errno), m_shm_info.shmaddr);
+            qCWarning(lcQpaXcb, "shmdt() failed (%d: %s) for %p",
+                      errno, strerror(errno), m_shm_info.shmaddr);
         }
         m_shm_info.shmid = 0; // unused
     }
@@ -718,6 +729,12 @@ void QXcbBackingStoreImage::preparePaint(const QRegion &region)
     m_pendingFlush |= region;
 }
 
+bool QXcbBackingStore::createSystemVShmSegment(QXcbConnection *c, size_t segmentSize, void *shmInfo)
+{
+    auto info = reinterpret_cast<xcb_shm_segment_info_t *>(shmInfo);
+    return QXcbBackingStoreImage::createSystemVShmSegment(c, segmentSize, info);
+}
+
 QXcbBackingStore::QXcbBackingStore(QWindow *window)
     : QPlatformBackingStore(window)
 {
@@ -757,7 +774,7 @@ void QXcbBackingStore::beginPaint(const QRegion &region)
 void QXcbBackingStore::endPaint()
 {
     if (Q_UNLIKELY(m_paintRegions.isEmpty())) {
-        qWarning("%s: paint regions empty!", Q_FUNC_INFO);
+        qCWarning(lcQpaXcb, "%s: paint regions empty!", Q_FUNC_INFO);
         return;
     }
 
@@ -811,7 +828,7 @@ void QXcbBackingStore::flush(QWindow *window, const QRegion &region, const QPoin
 
     QXcbWindow *platformWindow = static_cast<QXcbWindow *>(window->handle());
     if (!platformWindow) {
-        qWarning("QXcbBackingStore::flush: QWindow has no platform window (QTBUG-32681)");
+        qCWarning(lcQpaXcb, "%s QWindow has no platform window, see QTBUG-32681", Q_FUNC_INFO);
         return;
     }
 
diff --git a/src/plugins/platforms/xcb/qxcbbackingstore.h b/src/plugins/platforms/xcb/qxcbbackingstore.h
index 747626c213..734de1f7d7 100644
--- a/src/plugins/platforms/xcb/qxcbbackingstore.h
+++ b/src/plugins/platforms/xcb/qxcbbackingstore.h
@@ -74,6 +74,9 @@ public:
     void beginPaint(const QRegion &) override;
     void endPaint() override;
 
+    static bool createSystemVShmSegment(QXcbConnection *c, size_t segmentSize = 1,
+                                        void *shmInfo = nullptr);
+
 private:
     QXcbBackingStoreImage *m_image = nullptr;
     QStack<QRegion> m_paintRegions;
diff --git a/src/plugins/platforms/xcb/qxcbconnection.cpp b/src/plugins/platforms/xcb/qxcbconnection.cpp
index 879d31f29a..5fd1fc6a47 100644
--- a/src/plugins/platforms/xcb/qxcbconnection.cpp
+++ b/src/plugins/platforms/xcb/qxcbconnection.cpp
@@ -55,6 +55,7 @@
 #include "qxcbsystemtraytracker.h"
 #include "qxcbglintegrationfactory.h"
 #include "qxcbglintegration.h"
+#include "qxcbbackingstore.h"
 
 #include <QSocketNotifier>
 #include <QAbstractEventDispatcher>
@@ -585,7 +586,8 @@ QXcbConnection::QXcbConnection(QXcbNativeInterface *nativeInterface, bool canGra
 
     initializeAllAtoms();
 
-    initializeShm();
+    if (!qEnvironmentVariableIsSet("QT_XCB_NO_MITSHM"))
+        initializeShm();
     if (!qEnvironmentVariableIsSet("QT_XCB_NO_XRANDR"))
         initializeXRandr();
     if (!has_randr_extension)
@@ -973,7 +975,7 @@ void QXcbConnection::printXcbError(const char *message, xcb_generic_error_t *err
     uint clamped_error_code = qMin<uint>(error->error_code, (sizeof(xcb_errors) / sizeof(xcb_errors[0])) - 1);
     uint clamped_major_code = qMin<uint>(error->major_code, (sizeof(xcb_protocol_request_codes) / sizeof(xcb_protocol_request_codes[0])) - 1);
 
-    qWarning("%s: %d (%s), sequence: %d, resource id: %d, major code: %d (%s), minor code: %d",
+    qCWarning(lcQpaXcb, "%s: %d (%s), sequence: %d, resource id: %d, major code: %d (%s), minor code: %d",
              message,
              int(error->error_code), xcb_errors[clamped_error_code],
              int(error->sequence), int(error->resource_id),
@@ -1683,12 +1685,14 @@ bool QXcbConnection::compressEvent(xcb_generic_event_t *event, int currentIndex,
         if (!hasXInput2())
             return false;
 
-        // compress XI_Motion, but not from tablet devices
+        // compress XI_Motion
         if (isXIType(event, m_xiOpCode, XI_Motion)) {
 #if QT_CONFIG(tabletevent)
             xXIDeviceEvent *xdev = reinterpret_cast<xXIDeviceEvent *>(event);
+            // Xlib's XI2 events need memmove, see xi2PrepareXIGenericDeviceEvent()
+            auto sourceId = *reinterpret_cast<uint16_t *>(reinterpret_cast<char *>(&xdev->sourceid) + 4);
             if (!QCoreApplication::testAttribute(Qt::AA_CompressTabletEvents) &&
-                    const_cast<QXcbConnection *>(this)->tabletDataForDevice(xdev->sourceid))
+                    const_cast<QXcbConnection *>(this)->tabletDataForDevice(sourceId))
                 return false;
 #endif // QT_CONFIG(tabletevent)
             for (int j = nextIndex; j < eventqueue->size(); ++j) {
@@ -2101,20 +2105,34 @@ void QXcbConnection::initializeShm()
 {
     const xcb_query_extension_reply_t *reply = xcb_get_extension_data(m_connection, &xcb_shm_id);
     if (!reply || !reply->present) {
-        qWarning("QXcbConnection: MIT-SHM extension is not present on the X server.");
+        qCDebug(lcQpaXcb, "MIT-SHM extension is not present on the X server");
         return;
     }
-
     has_shm = true;
 
     auto shm_query = Q_XCB_REPLY(xcb_shm_query_version, m_connection);
-    if (!shm_query) {
-        qWarning("QXcbConnection: Failed to request MIT-SHM version");
-        return;
+    if (shm_query) {
+        has_shm_fd = (shm_query->major_version == 1 && shm_query->minor_version >= 2) ||
+                      shm_query->major_version > 1;
+    } else {
+        qCWarning(lcQpaXcb, "QXcbConnection: Failed to request MIT-SHM version");
     }
 
-    has_shm_fd = (shm_query->major_version == 1 && shm_query->minor_version >= 2) ||
-                  shm_query->major_version > 1;
+    qCDebug(lcQpaXcb) << "Has MIT-SHM     :" << has_shm;
+    qCDebug(lcQpaXcb) << "Has MIT-SHM FD  :" << has_shm_fd;
+
+    // Temporary disable warnings (unless running in debug mode).
+    auto logging = const_cast<QLoggingCategory*>(&lcQpaXcb());
+    bool wasEnabled = logging->isEnabled(QtMsgType::QtWarningMsg);
+    if (!logging->isEnabled(QtMsgType::QtDebugMsg))
+        logging->setEnabled(QtMsgType::QtWarningMsg, false);
+    if (!QXcbBackingStore::createSystemVShmSegment(this)) {
+        qCDebug(lcQpaXcb, "failed to create System V shared memory segment (remote "
+                          "X11 connection?), disabling SHM");
+        has_shm = has_shm_fd = false;
+    }
+    if (wasEnabled)
+        logging->setEnabled(QtMsgType::QtWarningMsg, true);
 }
 
 void QXcbConnection::initializeXFixes()
diff --git a/src/plugins/platforms/xcb/qxcbscreen.cpp b/src/plugins/platforms/xcb/qxcbscreen.cpp
index e1bd8eb752..df458e85d7 100644
--- a/src/plugins/platforms/xcb/qxcbscreen.cpp
+++ b/src/plugins/platforms/xcb/qxcbscreen.cpp
@@ -750,12 +750,7 @@ void QXcbScreen::updateGeometry(const QRect &geometry, uint8_t rotation)
         m_sizeMillimeters = sizeInMillimeters(geometry.size(), virtualDpi());
 
     qreal dpi = geometry.width() / physicalSize().width() * qreal(25.4);
-    qreal rawFactor = dpi/96;
-    int roundedFactor = qFloor(rawFactor);
-    // Round up for .8 and higher. This favors "small UI" over "large UI".
-    if (rawFactor - roundedFactor >= 0.8)
-        roundedFactor = qCeil(rawFactor);
-    m_pixelDensity = qMax(1, roundedFactor);
+    m_pixelDensity = qMax(1, qRound(dpi/96));
     m_geometry = geometry;
     m_availableGeometry = geometry & m_virtualDesktop->workArea();
     QWindowSystemInterface::handleScreenGeometryChange(QPlatformScreen::screen(), m_geometry, m_availableGeometry);
diff --git a/src/plugins/styles/mac/qmacstyle_mac.mm b/src/plugins/styles/mac/qmacstyle_mac.mm
index 5999163c91..2d212bfe3b 100644
--- a/src/plugins/styles/mac/qmacstyle_mac.mm
+++ b/src/plugins/styles/mac/qmacstyle_mac.mm
@@ -248,24 +248,6 @@ QT_NAMESPACE_ALIAS_OBJC_CLASS(QVerticalSplitView);
 }
 @end
 
-#if !QT_CONFIG(appstore_compliant)
-
-// This API was requested to Apple in rdar #36197888.
-// We know it's safe to use up to macOS 10.13.3.
-// See drawComplexControl(CC_ComboBox) for its usage.
-
-@interface NSComboBoxCell (QtButtonCell)
-@property (readonly) NSButtonCell *qt_buttonCell;
-@end
-
-@implementation NSComboBoxCell (QtButtonCell)
-- (NSButtonCell *)qt_buttonCell {
-    return self->_buttonCell;
-}
-@end
-
-#endif
-
 QT_BEGIN_NAMESPACE
 
 // The following constants are used for adjusting the size
@@ -5215,11 +5197,14 @@ void QMacStyle::drawComplexControl(ComplexControl cc, const QStyleOptionComplex
                 auto *cb = static_cast<NSComboBox *>(cc);
                 const auto frameRect = cw.adjustedControlFrame(combo->rect);
                 cb.frame = frameRect.toCGRect();
-#if !QT_CONFIG(appstore_compliant)
-                static_cast<NSComboBoxCell *>(cc.cell).qt_buttonCell.highlighted = isPressed;
-#else
-                // TODO Render to pixmap and darken the button manually
-#endif
+
+                // This API was requested to Apple in rdar #36197888. We know it's safe to use up to macOS 10.13.3
+                if (NSButtonCell *cell = static_cast<NSButtonCell *>([cc.cell qt_valueForPrivateKey:@"_buttonCell"])) {
+                    cell.highlighted = isPressed;
+                } else {
+                    // TODO Render to pixmap and darken the button manually
+                }
+
                 d->drawNSViewInRect(cb, frameRect, p, ^(CGContextRef __unused ctx, const CGRect &r) {
                     // FIXME This is usually drawn in the control's superview, but we wouldn't get inactive look in this case
                     [cb.cell drawWithFrame:r inView:cb];