Merge remote-tracking branch 'origin/5.14.0' into 5.14

Change-Id: I03927d2ef75514e4f2633839387806125d8954f1

6 files changed, 320 insertions, 90 deletions

diff --git a/src/3rdparty/VulkanMemoryAllocator/qt_attribution.json b/src/3rdparty/VulkanMemoryAllocator/qt_attribution.json
index 2548856ca7..0a5df738a8 100644
--- a/src/3rdparty/VulkanMemoryAllocator/qt_attribution.json
+++ b/src/3rdparty/VulkanMemoryAllocator/qt_attribution.json
@@ -2,7 +2,7 @@
     {
         "Id": "VulkanMemoryAllocator",
         "Name": "Vulkan Memory Allocator",
-        "QDocModule": "qtrhi",
+        "QDocModule": "qtgui",
         "Description": "Vulkan Memory Allocator",
         "QtUsage": "Memory management for the Vulkan backend of QRhi.",
 
diff --git a/src/corelib/global/qlibraryinfo.cpp b/src/corelib/global/qlibraryinfo.cpp
index 276741c9fb..f0f77fe68e 100644
--- a/src/corelib/global/qlibraryinfo.cpp
+++ b/src/corelib/global/qlibraryinfo.cpp
@@ -562,9 +562,39 @@ static QString getRelocatablePrefix()
     HMODULE hModule = getWindowsModuleHandle();
     const int kBufferSize = 4096;
     wchar_t buffer[kBufferSize];
-    const int pathSize = GetModuleFileName(hModule, buffer, kBufferSize);
-    if (pathSize > 0)
-        prefixPath = prefixFromQtCoreLibraryHelper(QString::fromWCharArray(buffer, pathSize));
+    DWORD pathSize = GetModuleFileName(hModule, buffer, kBufferSize);
+    const QString qtCoreFilePath = QString::fromWCharArray(buffer, int(pathSize));
+    const QString qtCoreDirPath = QFileInfo(qtCoreFilePath).absolutePath();
+    pathSize = GetModuleFileName(NULL, buffer, kBufferSize);
+    const QString exeDirPath = QFileInfo(QString::fromWCharArray(buffer, int(pathSize))).absolutePath();
+    if (QFileInfo(exeDirPath) == QFileInfo(qtCoreDirPath)) {
+        // QtCore DLL is next to the executable. This is either a windeployqt'ed executable or an
+        // executable within the QT_HOST_BIN directory. We're detecting the latter case by checking
+        // whether there's an import library corresponding to our QtCore DLL in PREFIX/lib.
+        const QString libdir = QString::fromLatin1(
+            qt_configure_strs + qt_configure_str_offsets[QLibraryInfo::LibrariesPath - 1]);
+        const QLatin1Char slash('/');
+#if defined(Q_CC_MINGW)
+        const QString implibPrefix = QStringLiteral("lib");
+        const QString implibSuffix = QStringLiteral(".a");
+#else
+        const QString implibPrefix;
+        const QString implibSuffix = QStringLiteral(".lib");
+#endif
+        const QString qtCoreImpLibFileName = implibPrefix
+                + QFileInfo(qtCoreFilePath).completeBaseName() + implibSuffix;
+        const QString qtCoreImpLibPath = qtCoreDirPath
+                + slash + QLatin1String(QT_CONFIGURE_LIBLOCATION_TO_PREFIX_PATH)
+                + slash + libdir
+                + slash + qtCoreImpLibFileName;
+        if (!QFileInfo::exists(qtCoreImpLibPath)) {
+            // We did not find a corresponding import library and conclude that this is a
+            // windeployqt'ed executable.
+            return exeDirPath;
+        }
+    }
+    if (!qtCoreFilePath.isEmpty())
+        prefixPath = prefixFromQtCoreLibraryHelper(qtCoreFilePath);
 #else
 #error "The chosen platform / config does not support querying for a dynamic prefix."
 #endif
diff --git a/src/corelib/time/qcalendar.cpp b/src/corelib/time/qcalendar.cpp
index d308aeba2b..6a4623ce92 100644
--- a/src/corelib/time/qcalendar.cpp
+++ b/src/corelib/time/qcalendar.cpp
@@ -100,7 +100,7 @@ struct Registry {
         if (id == QCalendar::System::User) {
             byId.push_back(calendar);
         } else {
-            Q_ASSERT(byId.at(size_t(id)) == nullptr);
+            Q_ASSERT(byId[size_t(id)] == nullptr);
             byId[size_t(id)] = calendar;
         }
         if (id == QCalendar::System::Gregorian) {
@@ -618,7 +618,7 @@ const QCalendarBackend *QCalendarBackend::fromEnum(QCalendar::System system)
     if (calendarRegistry.isDestroyed() || system == QCalendar::System::User)
         return nullptr;
     Q_ASSERT(calendarRegistry->byId.size() >= size_t(system));
-    if (auto *c = calendarRegistry->byId.at(size_t(system)))
+    if (auto *c = calendarRegistry->byId[size_t(system)])
         return c;
     switch (system) {
     case QCalendar::System::Gregorian:
diff --git a/src/plugins/platforms/android/qandroidassetsfileenginehandler.cpp b/src/plugins/platforms/android/qandroidassetsfileenginehandler.cpp
index 26e72a480f..fcc08ea00d 100644
--- a/src/plugins/platforms/android/qandroidassetsfileenginehandler.cpp
+++ b/src/plugins/platforms/android/qandroidassetsfileenginehandler.cpp
@@ -72,9 +72,10 @@ static inline QString prefixedPath(QString path)
 struct AssetItem {
     enum class Type {
         File,
-        Folder
+        Folder,
+        Invalid
     };
-
+    AssetItem() = default;
     AssetItem (const QString &rawName)
         : name(rawName)
     {
@@ -92,21 +93,47 @@ using AssetItemList = QVector<AssetItem>;
 class FolderIterator : public AssetItemList
 {
 public:
-    static QSharedPointer<FolderIterator> fromCache(const QString &path)
+    static QSharedPointer<FolderIterator> fromCache(const QString &path, bool clone)
     {
         QMutexLocker lock(&m_assetsCacheMutex);
         QSharedPointer<FolderIterator> *folder = m_assetsCache.object(path);
         if (!folder) {
             folder = new QSharedPointer<FolderIterator>{new FolderIterator{path}};
-            if (!m_assetsCache.insert(path, folder)) {
+            if ((*folder)->empty() || !m_assetsCache.insert(path, folder)) {
                 QSharedPointer<FolderIterator> res = *folder;
                 delete folder;
                 return res;
             }
         }
-        return *folder;
+        return clone ? QSharedPointer<FolderIterator>{new FolderIterator{*(*folder)}} : *folder;
+    }
+
+    static AssetItem::Type fileType(const QString &filePath)
+    {
+        const QStringList paths = filePath.split(QLatin1Char('/'));
+        QString fullPath;
+        AssetItem::Type res = AssetItem::Type::Invalid;
+        for (const auto &path: paths) {
+            auto folder = fromCache(fullPath, false);
+            auto it = std::lower_bound(folder->begin(), folder->end(), AssetItem{path}, [](const AssetItem &val, const AssetItem &assetItem) {
+                return val.name < assetItem.name;
+            });
+            if (it == folder->end() || it->name != path)
+                return AssetItem::Type::Invalid;
+            if (!fullPath.isEmpty())
+                fullPath.append(QLatin1Char('/'));
+            fullPath += path;
+            res = it->type;
+        }
+        return res;
     }
 
+    FolderIterator(const FolderIterator &other)
+        : AssetItemList(other)
+        , m_index(-1)
+        , m_path(other.m_path)
+    {}
+
     FolderIterator(const QString &path)
         : m_path(path)
     {
@@ -118,8 +145,12 @@ public:
             QJNIEnvironmentPrivate env;
             jobjectArray jFiles = static_cast<jobjectArray>(files.object());
             const jint nFiles = env->GetArrayLength(jFiles);
-            for (int i = 0; i < nFiles; ++i)
-                push_back({QJNIObjectPrivate(env->GetObjectArrayElement(jFiles, i)).toString()});
+            for (int i = 0; i < nFiles; ++i) {
+                AssetItem item{QJNIObjectPrivate(env->GetObjectArrayElement(jFiles, i)).toString()};
+                insert(std::upper_bound(begin(), end(), item, [](const auto &a, const auto &b){
+                    return a.name < b.name;
+                }), item);
+            }
         }
         m_path = assetsPrefix + QLatin1Char('/') + m_path + QLatin1Char('/');
         m_path.replace(QLatin1String("//"), QLatin1String("/"));
@@ -169,7 +200,7 @@ public:
                                       const QString &path)
         : QAbstractFileEngineIterator(filters, nameFilters)
     {
-        m_stack.push_back(FolderIterator::fromCache(cleanedAssetPath(path)));
+        m_stack.push_back(FolderIterator::fromCache(cleanedAssetPath(path), true));
         if (m_stack.last()->empty())
             m_stack.pop_back();
     }
@@ -215,7 +246,7 @@ public:
         if (!res)
             return {};
         if (res->second.type == AssetItem::Type::Folder) {
-            m_stack.push_back(FolderIterator::fromCache(cleanedAssetPath(currentFilePath())));
+            m_stack.push_back(FolderIterator::fromCache(cleanedAssetPath(currentFilePath()), true));
             if (m_stack.last()->empty())
                 m_stack.pop_back();
         }
@@ -257,6 +288,7 @@ public:
             m_assetFile = 0;
             return true;
         }
+        m_isFolder = false;
         return false;
     }
 
@@ -305,12 +337,12 @@ public:
 
     FileFlags fileFlags(FileFlags type = FileInfoAll) const override
     {
-        FileFlags flags(ReadOwnerPerm|ReadUserPerm|ReadGroupPerm|ReadOtherPerm|ExistsFlag);
+        FileFlags commonFlags(ReadOwnerPerm|ReadUserPerm|ReadGroupPerm|ReadOtherPerm|ExistsFlag);
+        FileFlags flags;
         if (m_assetFile)
-            flags |= FileType;
+            flags = FileType | commonFlags;
         else if (m_isFolder)
-            flags |= DirectoryType;
-
+            flags = DirectoryType | commonFlags;
         return type & flags;
     }
 
@@ -341,9 +373,20 @@ public:
 
     void setFileName(const QString &file) override
     {
+        if (m_fileName == cleanedAssetPath(file))
+            return;
         close();
         m_fileName = cleanedAssetPath(file);
-        m_isFolder = !open(QIODevice::ReadOnly) && !FolderIterator::fromCache(m_fileName)->empty();
+        switch (FolderIterator::fileType(m_fileName)) {
+        case AssetItem::Type::File:
+            open(QIODevice::ReadOnly);
+            break;
+        case AssetItem::Type::Folder:
+            m_isFolder = true;
+            break;
+        case AssetItem::Type::Invalid:
+            break;
+        }
     }
 
     Iterator *beginEntryList(QDir::Filters filters, const QStringList &filterNames) override
@@ -355,9 +398,9 @@ public:
 
 private:
     AAsset *m_assetFile = nullptr;
-    AAssetManager *m_assetManager;
+    AAssetManager *m_assetManager = nullptr;
     QString m_fileName;
-    bool m_isFolder;
+    bool m_isFolder = false;
 };
 
 
diff --git a/src/plugins/platforms/cocoa/qcocoascreen.h b/src/plugins/platforms/cocoa/qcocoascreen.h
index 7ec9a2b5af..dcf6f1c753 100644
--- a/src/plugins/platforms/cocoa/qcocoascreen.h
+++ b/src/plugins/platforms/cocoa/qcocoascreen.h
@@ -53,9 +53,6 @@ class QCocoaIntegration;
 class QCocoaScreen : public QPlatformScreen
 {
 public:
-    static void initializeScreens();
-    static void cleanupScreens();
-
     ~QCocoaScreen();
 
     // ----------------------------------------------------
@@ -79,7 +76,6 @@ public:
     // ----------------------------------------------------
 
     NSScreen *nativeScreen() const;
-    void updateProperties();
 
     void requestUpdate();
     void deliverUpdateRequests();
@@ -88,6 +84,7 @@ public:
     static QCocoaScreen *primaryScreen();
     static QCocoaScreen *get(NSScreen *nsScreen);
     static QCocoaScreen *get(CGDirectDisplayID displayId);
+    static QCocoaScreen *get(CFUUIDRef uuid);
 
     static CGPoint mapToNative(const QPointF &pos, QCocoaScreen *screen = QCocoaScreen::primaryScreen());
     static CGRect mapToNative(const QRectF &rect, QCocoaScreen *screen = QCocoaScreen::primaryScreen());
@@ -95,11 +92,23 @@ public:
     static QRectF mapFromNative(CGRect rect, QCocoaScreen *screen = QCocoaScreen::primaryScreen());
 
 private:
-    QCocoaScreen(CGDirectDisplayID displayId);
+    static void initializeScreens();
+    static void updateScreens();
+    static void cleanupScreens();
+
+    static bool updateScreensIfNeeded();
+    static NSArray *s_screenConfigurationBeforeUpdate;
+
     static void add(CGDirectDisplayID displayId);
+    QCocoaScreen(CGDirectDisplayID displayId);
+    void update(CGDirectDisplayID displayId);
     void remove();
 
+    bool isOnline() const;
+    bool isMirroring() const;
+
     CGDirectDisplayID m_displayId = kCGNullDirectDisplay;
+    CGDirectDisplayID displayId() const { return m_displayId; }
 
     QRect m_geometry;
     QRect m_availableGeometry;
@@ -116,6 +125,8 @@ private:
     dispatch_source_t m_displayLinkSource = nullptr;
     QAtomicInt m_pendingUpdates;
 
+    friend class QCocoaIntegration;
+    friend class QCocoaWindow;
     friend QDebug operator<<(QDebug debug, const QCocoaScreen *screen);
 };
 
diff --git a/src/plugins/platforms/cocoa/qcocoascreen.mm b/src/plugins/platforms/cocoa/qcocoascreen.mm
index bd5c95b9d0..e4dd4cf6c6 100644
--- a/src/plugins/platforms/cocoa/qcocoascreen.mm
+++ b/src/plugins/platforms/cocoa/qcocoascreen.mm
@@ -57,6 +57,7 @@ QT_BEGIN_NAMESPACE
 namespace CoreGraphics {
     Q_NAMESPACE
     enum DisplayChange {
+        ReconfiguredWithFlagsMissing = 0,
         Moved = kCGDisplayMovedFlag,
         SetMain = kCGDisplaySetMainFlag,
         SetMode = kCGDisplaySetModeFlag,
@@ -71,73 +72,165 @@ namespace CoreGraphics {
     Q_ENUM_NS(DisplayChange)
 }
 
+NSArray *QCocoaScreen::s_screenConfigurationBeforeUpdate = nil;
+
 void QCocoaScreen::initializeScreens()
 {
-    uint32_t displayCount = 0;
-    if (CGGetActiveDisplayList(0, nullptr, &displayCount) != kCGErrorSuccess)
-        qFatal("Failed to get number of active displays");
-
-    CGDirectDisplayID activeDisplays[displayCount];
-    if (CGGetActiveDisplayList(displayCount, &activeDisplays[0], &displayCount) != kCGErrorSuccess)
-        qFatal("Failed to get active displays");
-
-    for (CGDirectDisplayID displayId : activeDisplays)
-        QCocoaScreen::add(displayId);
+    updateScreens();
 
     CGDisplayRegisterReconfigurationCallback([](CGDirectDisplayID displayId, CGDisplayChangeSummaryFlags flags, void *userInfo) {
-        if (flags & kCGDisplayBeginConfigurationFlag)
-            return; // Wait for changes to apply
-
         Q_UNUSED(userInfo);
 
-        qCDebug(lcQpaScreen).verbosity(0).nospace() << "Display reconfiguration"
-            << " (" << QFlags<CoreGraphics::DisplayChange>(flags) << ")"
-            << " for displayId=" << displayId;
-
-        QCocoaScreen *cocoaScreen = QCocoaScreen::get(displayId);
+        // Displays are reconfigured in batches, and we want to update our screens
+        // once a batch ends, so that all the states of the displays are up to date.
+        static int displayReconfigurationsInProgress = 0;
+
+        const bool beforeReconfigure = flags & kCGDisplayBeginConfigurationFlag;
+        qCDebug(lcQpaScreen).verbosity(0).nospace() << "Display " << displayId
+                << (beforeReconfigure ? " about to reconfigure" : " was ")
+                << QFlags<CoreGraphics::DisplayChange>(flags)
+                << " with " << displayReconfigurationsInProgress
+                << " display configuration(s) in progress";
+
+        if (!flags) {
+            // CGDisplayRegisterReconfigurationCallback has been observed to be called
+            // with flags unset. This seems like a bug. The callback is not paired with
+            // a matching "completion" callback either, so we don't know whether to treat
+            // it as a begin or end of reconfigure.
+            return;
+        }
 
-        if ((flags & kCGDisplayAddFlag) || !cocoaScreen) {
-            if (!CGDisplayIsActive(displayId)) {
-                qCDebug(lcQpaScreen) << "Not adding inactive display" << displayId;
-                return; // Will be added when activated
+        if (beforeReconfigure) {
+            if (!displayReconfigurationsInProgress++) {
+                // There might have been a screen reconfigure before this that
+                // we didn't process yet, so do that now if that's the case.
+                updateScreensIfNeeded();
+
+                Q_ASSERT(!s_screenConfigurationBeforeUpdate);
+                s_screenConfigurationBeforeUpdate = NSScreen.screens;
+                qCDebug(lcQpaScreen, "Display reconfigure transaction started"
+                    " with screen configuration %p", s_screenConfigurationBeforeUpdate);
+
+                static void (^tryScreenUpdate)();
+                tryScreenUpdate = ^void () {
+                    qCDebug(lcQpaScreen) << "Attempting screen update from runloop block";
+                    if (!updateScreensIfNeeded())
+                        CFRunLoopPerformBlock(CFRunLoopGetMain(), kCFRunLoopCommonModes, tryScreenUpdate);
+                };
+                CFRunLoopPerformBlock(CFRunLoopGetMain(), kCFRunLoopCommonModes, tryScreenUpdate);
             }
-            QCocoaScreen::add(displayId);
-        } else if ((flags & kCGDisplayRemoveFlag) || !CGDisplayIsActive(displayId)) {
-            cocoaScreen->remove();
         } else {
-            // Detect changes to the primary screen immediately, instead of
-            // waiting for a display reconfigure with kCGDisplaySetMainFlag.
-            // This ensures that any property updates to the other screens
-            // will be in reference to the correct primary screen.
-            QCocoaScreen *mainDisplay = QCocoaScreen::get(CGMainDisplayID());
-            if (QGuiApplication::primaryScreen()->handle() != mainDisplay) {
-                mainDisplay->updateProperties();
-                qCInfo(lcQpaScreen) << "Primary screen changed to" << mainDisplay;
-                QWindowSystemInterface::handlePrimaryScreenChanged(mainDisplay);
-                if (cocoaScreen == mainDisplay)
-                    return; // Already reconfigured
-            }
+            Q_ASSERT_X(displayReconfigurationsInProgress, "QCococaScreen",
+                "Display configuration transactions are expected to be balanced");
 
-            cocoaScreen->updateProperties();
-            qCInfo(lcQpaScreen).nospace() << "Reconfigured " <<
-                (primaryScreen() == cocoaScreen ? "primary " : "")
-                << cocoaScreen;
+            if (!--displayReconfigurationsInProgress) {
+                qCDebug(lcQpaScreen) << "Display reconfigure transaction completed";
+                // We optimistically update now, in case the NSScreens have changed
+                updateScreensIfNeeded();
+            }
         }
     }, nullptr);
+
+    static QMacNotificationObserver screenParameterObserver(NSApplication.sharedApplication,
+        NSApplicationDidChangeScreenParametersNotification, [&]() {
+            qCDebug(lcQpaScreen) << "Received screen parameter change notification";
+            updateScreensIfNeeded(); // As a last resort we update screens here
+        });
+}
+
+bool QCocoaScreen::updateScreensIfNeeded()
+{
+    if (!s_screenConfigurationBeforeUpdate) {
+        qCDebug(lcQpaScreen) << "QScreens have already been updated, all good";
+        return true;
+    }
+
+    if (s_screenConfigurationBeforeUpdate == NSScreen.screens) {
+        qCDebug(lcQpaScreen) << "Still waiting for NSScreen configuration change";
+        return false;
+    }
+
+    qCDebug(lcQpaScreen, "NSScreen configuration changed to %p", NSScreen.screens);
+    updateScreens();
+
+    s_screenConfigurationBeforeUpdate = nil;
+    return true;
+}
+
+/*
+    Update the list of available QScreens, and the properties of existing screens.
+
+    At this point we rely on the NSScreen.screens to be up to date.
+*/
+void QCocoaScreen::updateScreens()
+{
+    uint32_t displayCount = 0;
+    if (CGGetOnlineDisplayList(0, nullptr, &displayCount) != kCGErrorSuccess)
+        qFatal("Failed to get number of online displays");
+
+    QVector<CGDirectDisplayID> onlineDisplays(displayCount);
+    if (CGGetOnlineDisplayList(displayCount, onlineDisplays.data(), &displayCount) != kCGErrorSuccess)
+        qFatal("Failed to get online displays");
+
+    qCInfo(lcQpaScreen) << "Updating screens with" << displayCount
+        << "online displays:" << onlineDisplays;
+
+    // TODO: Verify whether we can always assume the main display is first
+    int mainDisplayIndex = onlineDisplays.indexOf(CGMainDisplayID());
+    if (mainDisplayIndex < 0) {
+        qCWarning(lcQpaScreen) << "Main display not in list of online displays!";
+    } else if (mainDisplayIndex > 0) {
+        qCWarning(lcQpaScreen) << "Main display not first display, making sure it is";
+        onlineDisplays.move(mainDisplayIndex, 0);
+    }
+
+    for (CGDirectDisplayID displayId : onlineDisplays) {
+        Q_ASSERT(CGDisplayIsOnline(displayId));
+
+        if (CGDisplayMirrorsDisplay(displayId))
+            continue;
+
+        // A single physical screen can map to multiple displays IDs,
+        // depending on which GPU is in use or which physical port the
+        // screen is connected to. By mapping the display ID to a UUID,
+        // which are shared between displays that target the same screen,
+        // we can pick an existing QScreen to update instead of needlessly
+        // adding and removing QScreens.
+        QCFType<CFUUIDRef> uuid = CGDisplayCreateUUIDFromDisplayID(displayId);
+        Q_ASSERT(uuid);
+
+        if (QCocoaScreen *existingScreen = QCocoaScreen::get(uuid)) {
+            existingScreen->update(displayId);
+            qCInfo(lcQpaScreen) << "Updated" << existingScreen;
+            if (CGDisplayIsMain(displayId) && existingScreen != qGuiApp->primaryScreen()->handle()) {
+                qCInfo(lcQpaScreen) << "Primary screen changed to" << existingScreen;
+                QWindowSystemInterface::handlePrimaryScreenChanged(existingScreen);
+            }
+        } else {
+            QCocoaScreen::add(displayId);
+        }
+    }
+
+    for (QScreen *screen : QGuiApplication::screens()) {
+        QCocoaScreen *platformScreen = static_cast<QCocoaScreen*>(screen->handle());
+        if (!platformScreen->isOnline() || platformScreen->isMirroring())
+            platformScreen->remove();
+    }
 }
 
 void QCocoaScreen::add(CGDirectDisplayID displayId)
 {
     const bool isPrimary = CGDisplayIsMain(displayId);
     QCocoaScreen *cocoaScreen = new QCocoaScreen(displayId);
-    qCInfo(lcQpaScreen).nospace() << "Adding " << (isPrimary ? "new primary " : "") << cocoaScreen;
+    qCInfo(lcQpaScreen) << "Adding" << cocoaScreen
+        << (isPrimary ? "as new primary screen" : "");
     QWindowSystemInterface::handleScreenAdded(cocoaScreen, isPrimary);
 }
 
 QCocoaScreen::QCocoaScreen(CGDirectDisplayID displayId)
     : QPlatformScreen(), m_displayId(displayId)
 {
-    updateProperties();
+    update(m_displayId);
     m_cursor = new QCocoaCursor;
 }
 
@@ -150,8 +243,6 @@ void QCocoaScreen::cleanupScreens()
 
 void QCocoaScreen::remove()
 {
-    m_displayId = kCGNullDirectDisplay; // Prevent stale references during removal
-
     // This may result in the application responding to QGuiApplication::screenRemoved
     // by moving the window to another screen, either by setGeometry, or by setScreen.
     // If the window isn't moved by the application, Qt will as a fallback move it to
@@ -163,7 +254,7 @@ void QCocoaScreen::remove()
     // QCocoaWindow::windowDidChangeScreen. At that point the window will appear to have
     // already changed its screen, but that's only true if comparing the Qt screens,
     // not when comparing the NSScreens.
-    qCInfo(lcQpaScreen).nospace() << "Removing " << (primaryScreen() == this ? "current primary " : "") << this;
+    qCInfo(lcQpaScreen) << "Removing " << this;
     QWindowSystemInterface::handleScreenRemoved(this);
 }
 
@@ -210,9 +301,14 @@ static QString displayName(CGDirectDisplayID displayID)
     return QString();
 }
 
-void QCocoaScreen::updateProperties()
+void QCocoaScreen::update(CGDirectDisplayID displayId)
 {
-    Q_ASSERT(m_displayId);
+    if (displayId != m_displayId) {
+        qCDebug(lcQpaScreen) << "Reconnecting" << this << "as display" << displayId;
+        m_displayId = displayId;
+    }
+
+    Q_ASSERT(isOnline());
 
     const QRect previousGeometry = m_geometry;
     const QRect previousAvailableGeometry = m_availableGeometry;
@@ -350,8 +446,8 @@ struct DeferredDebugHelper
 
 void QCocoaScreen::deliverUpdateRequests()
 {
-    if (!m_displayId)
-        return; // Screen removed
+    if (!isOnline())
+        return;
 
     QMacAutoReleasePool pool;
 
@@ -562,6 +658,29 @@ QPixmap QCocoaScreen::grabWindow(WId view, int x, int y, int width, int height)
     return windowPixmap;
 }
 
+bool QCocoaScreen::isOnline() const
+{
+    // When a display is disconnected CGDisplayIsOnline and other CGDisplay
+    // functions that take a displayId will not return false, but will start
+    // returning -1 to signal that the displayId is invalid. Some functions
+    // will also assert or even crash in this case, so it's important that
+    // we double check if a display is online before calling other functions.
+    auto isOnline = CGDisplayIsOnline(m_displayId);
+    static const uint32_t kCGDisplayIsDisconnected = int32_t(-1);
+    return isOnline != kCGDisplayIsDisconnected && isOnline;
+}
+
+/*
+    Returns true if a screen is mirroring another screen
+*/
+bool QCocoaScreen::isMirroring() const
+{
+    if (!isOnline())
+        return false;
+
+    return CGDisplayMirrorsDisplay(m_displayId);
+}
+
 /*!
     The screen used as a reference for global window geometry
 */
@@ -586,6 +705,12 @@ QList<QPlatformScreen*> QCocoaScreen::virtualSiblings() const
 
 QCocoaScreen *QCocoaScreen::get(NSScreen *nsScreen)
 {
+    if (s_screenConfigurationBeforeUpdate) {
+        qCWarning(lcQpaScreen) << "Trying to resolve screen while waiting for screen reconfigure!";
+        if (!updateScreensIfNeeded())
+            qCWarning(lcQpaScreen) << "Failed to do last minute screen update. Expect crashes.";
+    }
+
     return get(nsScreen.qt_displayId);
 }
 
@@ -600,23 +725,34 @@ QCocoaScreen *QCocoaScreen::get(CGDirectDisplayID displayId)
     return nullptr;
 }
 
+QCocoaScreen *QCocoaScreen::get(CFUUIDRef uuid)
+{
+    for (QScreen *screen : QGuiApplication::screens()) {
+        auto *platformScreen = static_cast<QCocoaScreen*>(screen->handle());
+        if (!platformScreen->isOnline())
+            continue;
+
+        auto displayId = platformScreen->displayId();
+        QCFType<CFUUIDRef> candidateUuid(CGDisplayCreateUUIDFromDisplayID(displayId));
+        Q_ASSERT(candidateUuid);
+
+        if (candidateUuid == uuid)
+            return platformScreen;
+    }
+
+    return nullptr;
+}
+
 NSScreen *QCocoaScreen::nativeScreen() const
 {
     if (!m_displayId)
         return nil; // The display has been disconnected
 
-    // A single display may have different displayIds depending on
-    // which GPU is in use or which physical port the display is
-    // connected to. By comparing UUIDs instead of display IDs we
-    // ensure that we always pick up the appropriate NSScreen.
-    QCFType<CFUUIDRef> uuid = CGDisplayCreateUUIDFromDisplayID(m_displayId);
-
-    for (NSScreen *screen in [NSScreen screens]) {
-        if (QCFType<CFUUIDRef>(CGDisplayCreateUUIDFromDisplayID(screen.qt_displayId)) == uuid)
+    for (NSScreen *screen in NSScreen.screens) {
+        if (screen.qt_displayId == m_displayId)
             return screen;
     }
 
-    qCWarning(lcQpaScreen) << "Could not find NSScreen for display ID" << m_displayId;
     return nil;
 }
 
@@ -651,11 +787,21 @@ QDebug operator<<(QDebug debug, const QCocoaScreen *screen)
     debug.nospace();
     debug << "QCocoaScreen(" << (const void *)screen;
     if (screen) {
-        debug << ", geometry=" << screen->geometry();
+        debug << ", " << screen->name();
+        if (screen->isOnline()) {
+            if (CGDisplayIsAsleep(screen->displayId()))
+                debug << ", Sleeping";
+            if (auto mirroring = CGDisplayMirrorsDisplay(screen->displayId()))
+                debug << ", mirroring=" << mirroring;
+        } else {
+            debug << ", Offline";
+        }
+        debug << ", " << screen->geometry();
         debug << ", dpr=" << screen->devicePixelRatio();
-        debug << ", name=" << screen->name();
-        debug << ", displayId=" << screen->m_displayId;
-        debug << ", native=" << screen->nativeScreen();
+        debug << ", displayId=" << screen->displayId();
+
+        if (auto nativeScreen = screen->nativeScreen())
+            debug << ", " << nativeScreen;
     }
     debug << ')';
     return debug;