Merge remote-tracking branch 'origin/5.13' into dev

Change-Id: I38389a69411f4549fed432f1181dbe23398b34a2

84 files changed, 1243 insertions, 778 deletions

diff --git a/src/android/jar/src/org/qtproject/qt5/android/QtActivityDelegate.java b/src/android/jar/src/org/qtproject/qt5/android/QtActivityDelegate.java
index 1cbb8fe117..8fa889fa31 100644
--- a/src/android/jar/src/org/qtproject/qt5/android/QtActivityDelegate.java
+++ b/src/android/jar/src/org/qtproject/qt5/android/QtActivityDelegate.java
@@ -765,11 +765,19 @@ public class QtActivityDelegate
         }
         m_layout = new QtLayout(m_activity, startApplication);
 
+        int orientation = m_activity.getResources().getConfiguration().orientation;
+
         try {
             ActivityInfo info = m_activity.getPackageManager().getActivityInfo(m_activity.getComponentName(), PackageManager.GET_META_DATA);
-            if (info.metaData.containsKey("android.app.splash_screen_drawable")) {
+
+            String splashScreenKey = "android.app.splash_screen_drawable_"
+                + (orientation == Configuration.ORIENTATION_LANDSCAPE ? "landscape" : "portrait");
+            if (!info.metaData.containsKey(splashScreenKey))
+                splashScreenKey = "android.app.splash_screen_drawable";
+
+            if (info.metaData.containsKey(splashScreenKey)) {
                 m_splashScreenSticky = info.metaData.containsKey("android.app.splash_screen_sticky") && info.metaData.getBoolean("android.app.splash_screen_sticky");
-                int id = info.metaData.getInt("android.app.splash_screen_drawable");
+                int id = info.metaData.getInt(splashScreenKey);
                 m_splashScreen = new ImageView(m_activity);
                 m_splashScreen.setImageDrawable(m_activity.getResources().getDrawable(id));
                 m_splashScreen.setScaleType(ImageView.ScaleType.FIT_XY);
@@ -789,7 +797,6 @@ public class QtActivityDelegate
                                   new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,
                                                              ViewGroup.LayoutParams.MATCH_PARENT));
 
-        int orientation = m_activity.getResources().getConfiguration().orientation;
         int rotation = m_activity.getWindowManager().getDefaultDisplay().getRotation();
         boolean rot90 = (rotation == Surface.ROTATION_90 || rotation == Surface.ROTATION_270);
         boolean currentlyLandscape = (orientation == Configuration.ORIENTATION_LANDSCAPE);
diff --git a/src/android/templates/AndroidManifest.xml b/src/android/templates/AndroidManifest.xml
index f4b99e0895..aed8a3c888 100644
--- a/src/android/templates/AndroidManifest.xml
+++ b/src/android/templates/AndroidManifest.xml
@@ -52,6 +52,12 @@
             <!--  Messages maps -->
 
             <!-- Splash screen -->
+            <!-- Orientation-specific (portrait/landscape) data is checked first. If not available for current orientation,
+                 then android.app.splash_screen_drawable. For best results, use together with splash_screen_sticky and
+                 use hideSplashScreen() with a fade-out animation from Qt Android Extras to hide the splash screen when you
+                 are done populating your window with content. -->
+            <!-- meta-data android:name="android.app.splash_screen_drawable_portrait" android:resource="@drawable/logo_portrait" / -->
+            <!-- meta-data android:name="android.app.splash_screen_drawable_landscape" android:resource="@drawable/logo_landscape" / -->
             <!-- meta-data android:name="android.app.splash_screen_drawable" android:resource="@drawable/logo"/ -->
             <!-- meta-data android:name="android.app.splash_screen_sticky" android:value="true"/ -->
             <!-- Splash screen -->
diff --git a/src/corelib/doc/src/datastreamformat.qdoc b/src/corelib/doc/src/datastreamformat.qdoc
index 73ca51974d..d6b60f10ce 100644
--- a/src/corelib/doc/src/datastreamformat.qdoc
+++ b/src/corelib/doc/src/datastreamformat.qdoc
@@ -28,357 +28,71 @@
 /*!
     \page datastreamformat.html
     \title Serializing Qt Data Types
-    \brief Representations of data types that can be serialized by QDataStream.
+    \brief List of data types that can be serialized by QDataStream.
 
-    The \l QDataStream allows you to serialize some of the Qt data types.
-    The table below lists the data types that QDataStream can serialize
-    and how they are represented. The format described below is
-    \l{QDataStream::setVersion()}{version 13}.
+    The \l QDataStream class allows you to serialize the Qt data types
+    listed in this section as of \l{QDataStream::setVersion()}{version 18}.
 
     It is always best to cast integers to a Qt integer type, such as
-    qint16 or quint32, when reading and writing. This ensures that
+    \l{qint16} or \l{quint32}, when reading and writing. This ensures that
     you always know exactly what size integers you are reading and
     writing, no matter what the underlying platform and architecture
     the application happens to be running on.
 
-    \table
-    \row \li bool
-         \li \list
-            \li boolean
-            \endlist
-    \row \li qint8
-         \li \list
-            \li signed byte
-            \endlist
-    \row \li qint16
-         \li \list
-            \li signed 16-bit integer
-            \endlist
-    \row \li qint32
-         \li \list
-            \li signed 32-bit integer
-            \endlist
-    \row \li qint64
-         \li \list
-            \li signed 64-bit integer
-            \endlist
-    \row \li quint8
-         \li \list
-            \li unsigned byte
-            \endlist
-    \row \li quint16
-         \li \list
-            \li unsigned 16-bit integer
-            \endlist
-    \row \li quint32
-         \li \list
-            \li unsigned 32-bit integer
-            \endlist
-    \row \li quint64
-         \li \list
-            \li unsigned 64-bit integer
-            \endlist
-    \row \li \c float
-         \li \list
-            \li 32-bit floating point number using the standard IEEE 754 format
-            \endlist
-    \row \li \c double
-         \li \list
-            \li 64-bit floating point number using the standard IEEE 754 format
-            \endlist
-    \row \li \c {const char *}
-         \li \list
-            \li The string length (quint32)
-            \li The string bytes, excluding the terminating 0
-            \endlist
-    \row \li QBitArray
-         \li \list
-            \li The array size (quint32)
-            \li The array bits, i.e. (size + 7)/8 bytes
-            \endlist
-    \row \li QBrush
-         \li \list
-            \li The brush style (quint8)
-            \li The brush color (QColor)
-            \li If style is CustomPattern, the brush pixmap (QPixmap)
-            \endlist
-    \row \li QByteArray
-         \li \list
-            \li If the byte array is null: 0xFFFFFFFF (quint32)
-            \li Otherwise: the array size (quint32) followed by the array bytes, i.e. size bytes
-            \endlist
-    \row \li \l QColor
-         \li \list
-            \li Color spec (qint8)
-            \li Alpha value (quint16)
-            \li Red value (quint16)
-            \li Green value (quint16)
-            \li Blue value (quint16)
-            \li Pad value (quint16)
-            \endlist
-    \row \li QCursor
-         \li \list
-            \li Shape ID (qint16)
-            \li If shape is BitmapCursor: The bitmap (QPixmap), mask (QPixmap), and hot spot (QPoint)
-            \endlist
-    \row \li QDate
-         \li \list
-            \li Julian day (quint32)
-            \endlist
-    \row \li QDateTime
-         \li \list
-            \li Date (QDate)
-            \li Time (QTime)
-            \li The \l{Qt::TimeSpec}{time spec}
-                offsetFromUtc (qint32) if Qt::TimeSpec is offsetFromUtc
-                TimeZone(QTimeZone) if Qt::TimeSpec is TimeZone
-            \endlist
-    \row \li QEasingCurve
-         \li \list
-            \li type (quint8)
-            \li func (quint64)
-            \li hasConfig (bool)
-            \li If hasConfig is true then these fields follow:
-            \li list
-                \li period (double)
-                \li amplitude (double)
-                \li overshoot (double)
-            \endlist
-    \row \li QFont
-         \li \list
-            \li The family (QString)
-            \li The style name (QString)
-            \li The point size (double)
-            \li The pixel size (qint32)
-            \li The style hint (quint8)
-            \li The style strategy (quint16)
-            \li The char set (quint8)
-            \li The weight (quint8)
-            \li The font bits (quint8)
-            \li The font stretch (quint16)
-            \li The extended font bits (quint8)
-            \li The letter spacing (double)
-            \li The word spacing (double)
-            \li The hinting preference (quint8)
-            \endlist
-    \row \li QHash<Key, T>
-         \li \list
-            \li The number of items (quint32)
-            \li For all items, the key (Key) and value (T)
-            \endlist
-    \row \li QIcon
-         \li \list
-            \li The number of pixmap entries (quint32)
-            \li For all pixmap entries:
-               \list
-               \li The pixmap (QPixmap)
-               \li The file name (QString)
-               \li The pixmap size (QSize)
-               \li The \l{QIcon::Mode}{mode} (quint32)
-               \li The \l{QIcon::State}{state} (quint32)
-               \endlist
-            \endlist
-    \row \li QImage
-         \li \list
-            \li If the image is null a "null image" marker is saved;
-            otherwise the image is saved in PNG or BMP format (depending
-            on the stream version). If you want control of the format,
-            stream the image into a QBuffer (using QImageIOHandler/QImageIOPlugin) and stream
-            that.
-            \endlist
-    \row \li QKeySequence
-         \li \list
-            \li A QList<int>, where each integer is a key in the key sequence
-            \endlist
-    \row \li QLinkedList<T>
-         \li \list
-            \li The number of items (quint32)
-            \li The items (T)
-            \endlist
-    \row \li QList<T>
-         \li \list
-            \li The number of items (quint32)
-            \li The items (T)
-            \endlist
-    \row \li QMap<Key, T>
-         \li \list
-            \li The number of items (quint32)
-            \li For all items, the key (Key) and value (T)
-            \endlist
-    \row \li QMargins
-         \li \list
-            \li left (int)
-            \li top (int)
-            \li right (int)
-            \li bottom (int)
-            \endlist
-    \row \li QMatrix
-         \li \list
-            \li m11 (double)
-            \li m12 (double)
-            \li m21 (double)
-            \li m22 (double)
-            \li dx (double)
-            \li dy (double)
-            \endlist
-    \row \li QMatrix4x4
-         \li \list
-            \li m11 (float)
-            \li m12 (float)
-            \li m13 (float)
-            \li m14 (float)
-            \li m21 (float)
-            \li m22 (float)
-            \li m23 (float)
-            \li m24 (float)
-            \li m31 (float)
-            \li m32 (float)
-            \li m33 (float)
-            \li m34 (float)
-            \li m41 (float)
-            \li m42 (float)
-            \li m43 (float)
-            \li m44 (float)
-            \endlist
-    \row \li QPair<T1, T2>
-         \li \list
-            \li first (T1)
-            \li second (T2)
-            \endlist
-    \row \li QPalette
-         \li The disabled, active, and inactive color groups, each of which consists
-            of the following:
-            \list
-            \li foreground (QBrush)
-            \li button (QBrush)
-            \li light (QBrush)
-            \li midlight (QBrush)
-            \li dark (QBrush)
-            \li mid (QBrush)
-            \li text (QBrush)
-            \li brightText (QBrush)
-            \li buttonText (QBrush)
-            \li base (QBrush)
-            \li background (QBrush)
-            \li shadow (QBrush)
-            \li highlight (QBrush)
-            \li highlightedText (QBrush)
-            \li link (QBrush)
-            \li linkVisited (QBrush)
-            \endlist
-    \row \li QPen
-         \li \list
-            \li The pen styles (quint8)
-            \li The pen width (quint16)
-            \li The pen color (QColor)
-            \endlist
-    \row \li QPicture
-         \li \list
-            \li The size of the picture data (quint32)
-            \li The raw bytes of picture data (char)
-            \endlist
-    \row \li QPixmap
-         \li \list
-            \li Save it as a PNG image.
-            \endlist
-    \row \li QPoint
-         \li \list
-            \li The x coordinate (qint32)
-            \li The y coordinate (qint32)
-            \endlist
-    \row \li QQuaternion
-         \li \list
-            \li The scalar component (float)
-            \li The x coordinate (float)
-            \li The y coordinate (float)
-            \li The z coordinate (float)
-            \endlist
-    \row \li QRect
-         \li \list
-            \li left (qint32)
-            \li top (qint32)
-            \li right (qint32)
-            \li bottom (qint32)
-            \endlist
-    \row \li QRegExp
-         \li \list
-            \li The regexp pattern (QString)
-            \li Case sensitivity (quint8)
-            \li Regular expression syntax (quint8)
-            \li Minimal matching (quint8)
-            \endlist
-    \row \li QRegularExpression
-         \li \list
-            \li The regular expression pattern (QString)
-            \li The pattern options (quint32)
-            \endlist
-    \row \li QRegion
-         \li \list
-            \li The size of the data, i.e. 8 + 16 * (number of rectangles) (quint32)
-            \li 10 (qint32)
-            \li The number of rectangles (quint32)
-            \li The rectangles in sequential order (QRect)
-            \endlist
-    \row \li QSize
-         \li \list
-            \li width (qint32)
-            \li height (qint32)
-            \endlist
-    \row \li QString
-         \li \list
-            \li If the string is null: 0xFFFFFFFF (quint32)
-            \li Otherwise: The string length in bytes (quint32) followed by the data in UTF-16
-            \endlist
-    \row \li QTime
-         \li \list
-            \li Milliseconds since midnight (quint32)
-            \endlist
-    \row \li QTransform
-         \li \list
-            \li m11 (double)
-            \li m12 (double)
-            \li m13 (double)
-            \li m21 (double)
-            \li m22 (double)
-            \li m23 (double)
-            \li m31 (double)
-            \li m32 (double)
-            \li m33 (double)
-            \endlist
-    \row \li QUrl
-         \li \list
-            \li Holds an URL (QString)
-            \endlist
-    \row \li QVariant
-         \li \list
-            \li The type of the data (quint32)
-            \li The null flag (qint8)
-            \li The data of the specified type
-            \endlist
-    \row \li QVector2D
-         \li \list
-            \li the x coordinate (float)
-            \li the y coordinate (float)
-            \endlist
-    \row \li QVector3D
-         \li \list
-            \li the x coordinate (float)
-            \li the y coordinate (float)
-            \li the z coordinate (float)
-            \endlist
-    \row \li QVector4D
-         \li \list
-            \li the x coordinate (float)
-            \li the y coordinate (float)
-            \li the z coordinate (float)
-            \li the w coordinate (float)
-            \endlist
-    \row \li QVector<T>
-         \li \list
-            \li The number of items (quint32)
-            \li The items (T)
-            \endlist
-    \endtable
+    \list
+    \li bool
+    \li \l{qint8}
+    \li \l{qint16}
+    \li \l{qint32}
+    \li \l{qint64}
+    \li \l{quint8}
+    \li \l{quint16}
+    \li \l{quint32}
+    \li \l{quint64}
+    \li \c float
+    \li \c double
+    \li \c {const char *}
+    \li QBitArray
+    \li QBrush
+    \li QByteArray
+    \li QColor
+    \li QCursor
+    \li QDate
+    \li QDateTime
+    \li QEasingCurve
+    \li QFont
+    \li QGenericMatrix
+    \li QHash<Key, T>
+    \li QIcon
+    \li QImage
+    \li QKeySequence
+    \li QLinkedList<T>
+    \li QList<T>
+    \li QMap<Key, T>
+    \li QMargins
+    \li QMatrix4x4
+    \li QPair<T1, T2>
+    \li QPalette
+    \li QPen
+    \li QPicture
+    \li QPixmap
+    \li QPoint
+    \li QQuaternion
+    \li QRect
+    \li QRegExp
+    \li QRegularExpression
+    \li QRegion
+    \li QSize
+    \li QString
+    \li QTime
+    \li QTransform
+    \li QUrl
+    \li QVariant
+    \li QVector2D
+    \li QVector3D
+    \li QVector4D
+    \li QVector<T>
+    \endlist
 
     \sa {JSON Support in Qt}
 */
diff --git a/src/corelib/io/qtemporaryfile.cpp b/src/corelib/io/qtemporaryfile.cpp
index 35bb465a04..ced08a9a87 100644
--- a/src/corelib/io/qtemporaryfile.cpp
+++ b/src/corelib/io/qtemporaryfile.cpp
@@ -908,8 +908,8 @@ QTemporaryFile *QTemporaryFile::createNativeFile(QFile &file)
         qint64 old_off = 0;
         if(wasOpen)
             old_off = file.pos();
-        else
-            file.open(QIODevice::ReadOnly);
+        else if (!file.open(QIODevice::ReadOnly))
+            return nullptr;
         //dump data
         QTemporaryFile *ret = new QTemporaryFile;
         if (ret->open()) {
diff --git a/src/corelib/kernel/qtranslator.cpp b/src/corelib/kernel/qtranslator.cpp
index dc39490ab0..a2111a084f 100644
--- a/src/corelib/kernel/qtranslator.cpp
+++ b/src/corelib/kernel/qtranslator.cpp
@@ -66,6 +66,7 @@
 #endif
 
 #include <stdlib.h>
+#include <new>
 
 #include "qobject_p.h"
 
@@ -585,7 +586,7 @@ bool QTranslatorPrivate::do_load(const QString &realname, const QString &directo
 #endif // QT_USE_MMAP
 
         if (!ok) {
-            d->unmapPointer = new char[d->unmapLength];
+            d->unmapPointer = new (std::nothrow) char[d->unmapLength];
             if (d->unmapPointer) {
                 file.seek(0);
                 qint64 readResult = file.read(d->unmapPointer, d->unmapLength);
diff --git a/src/gui/image/qiconloader.cpp b/src/gui/image/qiconloader.cpp
index a9adde8c8d..1d0c93f26f 100644
--- a/src/gui/image/qiconloader.cpp
+++ b/src/gui/image/qiconloader.cpp
@@ -629,7 +629,10 @@ void QIconLoaderEngine::ensureLoaded()
 void QIconLoaderEngine::paint(QPainter *painter, const QRect &rect,
                              QIcon::Mode mode, QIcon::State state)
 {
-    QSize pixmapSize = rect.size();
+    const qreal dpr = !qApp->testAttribute(Qt::AA_UseHighDpiPixmaps) ?
+                qreal(1.0) : painter->device()->devicePixelRatioF();
+
+    QSize pixmapSize = rect.size() * dpr;
     painter->drawPixmap(rect, pixmap(pixmapSize, mode, state));
 }
 
diff --git a/src/gui/image/qimage.cpp b/src/gui/image/qimage.cpp
index 18125460c7..a6ac3bc333 100644
--- a/src/gui/image/qimage.cpp
+++ b/src/gui/image/qimage.cpp
@@ -127,7 +127,7 @@ QImageData * QImageData::create(const QSize &size, QImage::Format format)
     int height = size.height();
     int depth = qt_depthForFormat(format);
     auto params = calculateImageParameters(width, height, depth);
-    if (params.bytesPerLine < 0)
+    if (!params.isValid())
         return nullptr;
 
     QScopedPointer<QImageData> d(new QImageData);
@@ -786,7 +786,7 @@ QImageData *QImageData::create(uchar *data, int width, int height,  int bpl, QIm
 
     const int depth = qt_depthForFormat(format);
     auto params = calculateImageParameters(width, height, depth);
-    if (params.totalSize < 0)
+    if (!params.isValid())
         return nullptr;
 
     if (bpl > 0) {
@@ -1492,10 +1492,17 @@ qsizetype QImage::sizeInBytes() const
 
     \sa scanLine()
 */
+#if QT_VERSION >= QT_VERSION_CHECK(6,0,0)
+qsizetype QImage::bytesPerLine() const
+{
+    return d ? d->bytes_per_line : 0;
+}
+#else
 int QImage::bytesPerLine() const
 {
     return d ? d->bytes_per_line : 0;
 }
+#endif
 
 
 /*!
diff --git a/src/gui/image/qimage.h b/src/gui/image/qimage.h
index b09e69c839..af7e6988cb 100644
--- a/src/gui/image/qimage.h
+++ b/src/gui/image/qimage.h
@@ -228,7 +228,11 @@ public:
     uchar *scanLine(int);
     const uchar *scanLine(int) const;
     const uchar *constScanLine(int) const;
+#if QT_VERSION >= QT_VERSION_CHECK(6,0,0)
+    qsizetype bytesPerLine() const;
+#else
     int bytesPerLine() const;
+#endif
 
     bool valid(int x, int y) const;
     bool valid(const QPoint &pt) const;
diff --git a/src/gui/image/qimage_p.h b/src/gui/image/qimage_p.h
index 1e0578a0f4..9da6acd0a7 100644
--- a/src/gui/image/qimage_p.h
+++ b/src/gui/image/qimage_p.h
@@ -113,6 +113,7 @@ struct Q_GUI_EXPORT QImageData {        // internal image data
     struct ImageSizeParameters {
         qsizetype bytesPerLine;
         qsizetype totalSize;
+        bool isValid() const { return bytesPerLine > 0 && totalSize > 0; }
     };
     static ImageSizeParameters calculateImageParameters(qsizetype width, qsizetype height, qsizetype depth);
 };
@@ -139,6 +140,11 @@ QImageData::calculateImageParameters(qsizetype width, qsizetype height, qsizetyp
     qsizetype dummy;
     if (mul_overflow(height, qsizetype(sizeof(uchar *)), &dummy))
         return invalid;                                 // why is this here?
+#if QT_VERSION < QT_VERSION_CHECK(6,0,0)
+    // Disallow images where width * depth calculations might overflow
+    if (width > (INT_MAX - 31) / depth)
+        return invalid;
+#endif
 
     return { bytes_per_line, total_size };
 }
diff --git a/src/gui/kernel/qplatformgraphicsbuffer.h b/src/gui/kernel/qplatformgraphicsbuffer.h
index 65c24bebc9..9004116ea4 100644
--- a/src/gui/kernel/qplatformgraphicsbuffer.h
+++ b/src/gui/kernel/qplatformgraphicsbuffer.h
@@ -71,12 +71,14 @@ public:
         TextureAccess       = 0x04,
         HWCompositor        = 0x08
     };
+    Q_ENUM(AccessType);
     Q_DECLARE_FLAGS(AccessTypes, AccessType);
 
     enum Origin {
         OriginBottomLeft,
         OriginTopLeft
     };
+    Q_ENUM(Origin);
 
     ~QPlatformGraphicsBuffer();
 
diff --git a/src/gui/kernel/qplatformintegration.cpp b/src/gui/kernel/qplatformintegration.cpp
index 199ef0de07..490cfc6178 100644
--- a/src/gui/kernel/qplatformintegration.cpp
+++ b/src/gui/kernel/qplatformintegration.cpp
@@ -462,87 +462,6 @@ QList<int> QPlatformIntegration::possibleKeys(const QKeyEvent *) const
     return QList<int>();
 }
 
-/*!
-  Should be called by the implementation whenever a new screen is added.
-
-  The first screen added will be the primary screen, used for default-created
-  windows, GL contexts, and other resources unless otherwise specified.
-
-  This adds the screen to QGuiApplication::screens(), and emits the
-  QGuiApplication::screenAdded() signal.
-
-  The screen should be deleted by calling QPlatformIntegration::destroyScreen().
-*/
-void QPlatformIntegration::screenAdded(QPlatformScreen *ps, bool isPrimary)
-{
-    QScreen *screen = new QScreen(ps);
-
-    if (isPrimary) {
-        QGuiApplicationPrivate::screen_list.prepend(screen);
-    } else {
-        QGuiApplicationPrivate::screen_list.append(screen);
-    }
-
-    QGuiApplicationPrivate::resetCachedDevicePixelRatio();
-
-    emit qGuiApp->screenAdded(screen);
-
-    if (isPrimary)
-        emit qGuiApp->primaryScreenChanged(screen);
-}
-
-/*!
-  Just removes the screen, call destroyScreen instead.
-
-  \sa destroyScreen()
-*/
-
-void QPlatformIntegration::removeScreen(QScreen *screen)
-{
-    const bool wasPrimary = (!QGuiApplicationPrivate::screen_list.isEmpty() && QGuiApplicationPrivate::screen_list.at(0) == screen);
-    QGuiApplicationPrivate::screen_list.removeOne(screen);
-
-    QGuiApplicationPrivate::resetCachedDevicePixelRatio();
-
-    if (wasPrimary && qGuiApp && !QGuiApplicationPrivate::screen_list.isEmpty())
-        emit qGuiApp->primaryScreenChanged(QGuiApplicationPrivate::screen_list.at(0));
-}
-
-/*!
-  Should be called by the implementation whenever a screen is removed.
-
-  This removes the screen from QGuiApplication::screens(), and deletes it.
-
-  Failing to call this and manually deleting the QPlatformScreen instead may
-  lead to a crash due to a pure virtual call.
-*/
-void QPlatformIntegration::destroyScreen(QPlatformScreen *screen)
-{
-    QScreen *qScreen = screen->screen();
-    removeScreen(qScreen);
-    delete qScreen;
-    delete screen;
-}
-
-/*!
-  Should be called whenever the primary screen changes.
-
-  When the screen specified as primary changes, this method will notify
-  QGuiApplication and emit the QGuiApplication::primaryScreenChanged signal.
- */
-
-void QPlatformIntegration::setPrimaryScreen(QPlatformScreen *newPrimary)
-{
-    QScreen* newPrimaryScreen = newPrimary->screen();
-    int idx = QGuiApplicationPrivate::screen_list.indexOf(newPrimaryScreen);
-    Q_ASSERT(idx >= 0);
-    if (idx == 0)
-        return;
-
-    QGuiApplicationPrivate::screen_list.swapItemsAt(0, idx);
-    emit qGuiApp->primaryScreenChanged(newPrimaryScreen);
-}
-
 QStringList QPlatformIntegration::themeNames() const
 {
     return QStringList();
diff --git a/src/gui/kernel/qplatformintegration.h b/src/gui/kernel/qplatformintegration.h
index 8ece390420..b764bd2617 100644
--- a/src/gui/kernel/qplatformintegration.h
+++ b/src/gui/kernel/qplatformintegration.h
@@ -192,8 +192,6 @@ public:
 #endif
     virtual void setApplicationIcon(const QIcon &icon) const;
 
-    void removeScreen(QScreen *screen);
-
     virtual void beep() const;
 
 #if QT_CONFIG(vulkan) || defined(Q_CLANG_QDOC)
@@ -202,10 +200,6 @@ public:
 
 protected:
     QPlatformIntegration() = default;
-
-    void screenAdded(QPlatformScreen *screen, bool isPrimary = false);
-    void destroyScreen(QPlatformScreen *screen);
-    void setPrimaryScreen(QPlatformScreen *newPrimary);
 };
 
 QT_END_NAMESPACE
diff --git a/src/gui/kernel/qplatformscreen.cpp b/src/gui/kernel/qplatformscreen.cpp
index b7b312e89e..9c5876550a 100644
--- a/src/gui/kernel/qplatformscreen.cpp
+++ b/src/gui/kernel/qplatformscreen.cpp
@@ -61,8 +61,7 @@ QPlatformScreen::~QPlatformScreen()
 {
     Q_D(QPlatformScreen);
     if (d->screen) {
-        qWarning("Manually deleting a QPlatformScreen. Call QPlatformIntegration::destroyScreen instead.");
-        QGuiApplicationPrivate::platformIntegration()->removeScreen(d->screen);
+        qWarning("Manually deleting a QPlatformScreen. Call QWindowSystemInterface::handleScreenRemoved instead.");
         delete d->screen;
     }
 }
diff --git a/src/gui/kernel/qscreen.cpp b/src/gui/kernel/qscreen.cpp
index f208eb02be..952023dd1b 100644
--- a/src/gui/kernel/qscreen.cpp
+++ b/src/gui/kernel/qscreen.cpp
@@ -106,9 +106,18 @@ void QScreenPrivate::setPlatformScreen(QPlatformScreen *screen)
  */
 QScreen::~QScreen()
 {
-    if (!qApp)
+    // Remove screen
+    const bool wasPrimary = QGuiApplication::primaryScreen() == this;
+    QGuiApplicationPrivate::screen_list.removeOne(this);
+    QGuiApplicationPrivate::resetCachedDevicePixelRatio();
+
+    if (!qGuiApp)
         return;
 
+    QScreen *newPrimaryScreen = QGuiApplication::primaryScreen();
+    if (wasPrimary && newPrimaryScreen)
+        emit qGuiApp->primaryScreenChanged(newPrimaryScreen);
+
     // Allow clients to manage windows that are affected by the screen going
     // away, before we fall back to moving them to the primary screen.
     emit qApp->screenRemoved(this);
@@ -116,11 +125,8 @@ QScreen::~QScreen()
     if (QGuiApplication::closingDown())
         return;
 
-    QScreen *primaryScreen = QGuiApplication::primaryScreen();
-    if (this == primaryScreen)
-        return;
-
-    bool movingFromVirtualSibling = primaryScreen && primaryScreen->handle()->virtualSiblings().contains(handle());
+    bool movingFromVirtualSibling = newPrimaryScreen
+        && newPrimaryScreen->handle()->virtualSiblings().contains(handle());
 
     // Move any leftover windows to the primary screen
     const auto allWindows = QGuiApplication::allWindows();
@@ -129,7 +135,7 @@ QScreen::~QScreen()
             continue;
 
         const bool wasVisible = window->isVisible();
-        window->setScreen(primaryScreen);
+        window->setScreen(newPrimaryScreen);
 
         // Re-show window if moved from a virtual sibling screen. Otherwise
         // leave it up to the application developer to show the window.
diff --git a/src/gui/kernel/qscreen.h b/src/gui/kernel/qscreen.h
index 8c9b16e08e..14392d3036 100644
--- a/src/gui/kernel/qscreen.h
+++ b/src/gui/kernel/qscreen.h
@@ -169,6 +169,7 @@ private:
     friend class QPlatformIntegration;
     friend class QPlatformScreen;
     friend class QHighDpiScaling;
+    friend class QWindowSystemInterface;
 };
 
 #ifndef QT_NO_DEBUG_STREAM
diff --git a/src/gui/kernel/qwindow.cpp b/src/gui/kernel/qwindow.cpp
index 6e0c2de240..19a5d39ad5 100644
--- a/src/gui/kernel/qwindow.cpp
+++ b/src/gui/kernel/qwindow.cpp
@@ -1922,9 +1922,6 @@ void QWindowPrivate::destroy()
     resizeEventPending = true;
     receivedExpose = false;
     exposed = false;
-
-    if (wasVisible)
-        maybeQuitOnLastWindowClosed();
 }
 
 /*!
@@ -2313,8 +2310,17 @@ bool QWindow::event(QEvent *ev)
 #endif
 
     case QEvent::Close:
-        if (ev->isAccepted())
+        if (ev->isAccepted()) {
+            Q_D(QWindow);
+            bool wasVisible = isVisible();
             destroy();
+            if (wasVisible) {
+                // FIXME: This check for visibility is a workaround for both QWidgetWindow
+                // and QWindow having logic to emit lastWindowClosed, and possibly quit the
+                // application. We should find a better way to handle this.
+                d->maybeQuitOnLastWindowClosed();
+            }
+        }
         break;
 
     case QEvent::Expose:
diff --git a/src/gui/kernel/qwindowsysteminterface.cpp b/src/gui/kernel/qwindowsysteminterface.cpp
index 8e6e3ce618..6f3edb10b4 100644
--- a/src/gui/kernel/qwindowsysteminterface.cpp
+++ b/src/gui/kernel/qwindowsysteminterface.cpp
@@ -780,6 +780,67 @@ QT_DEFINE_QPA_EVENT_HANDLER(void, handleTouchCancelEvent, QWindow *window, ulong
     QWindowSystemInterfacePrivate::handleWindowSystemEvent<Delivery>(e);
 }
 
+/*!
+    Should be called by the implementation whenever a new screen is added.
+
+    The first screen added will be the primary screen, used for default-created
+    windows, GL contexts, and other resources unless otherwise specified.
+
+    This adds the screen to QGuiApplication::screens(), and emits the
+    QGuiApplication::screenAdded() signal.
+
+    The screen should be deleted by calling QWindowSystemInterface::handleScreenRemoved().
+*/
+void QWindowSystemInterface::handleScreenAdded(QPlatformScreen *ps, bool isPrimary)
+{
+    QScreen *screen = new QScreen(ps);
+
+    if (isPrimary)
+        QGuiApplicationPrivate::screen_list.prepend(screen);
+    else
+        QGuiApplicationPrivate::screen_list.append(screen);
+
+    QGuiApplicationPrivate::resetCachedDevicePixelRatio();
+
+    emit qGuiApp->screenAdded(screen);
+
+    if (isPrimary)
+        emit qGuiApp->primaryScreenChanged(screen);
+}
+
+/*!
+    Should be called by the implementation whenever a screen is removed.
+
+    This removes the screen from QGuiApplication::screens(), and deletes it.
+
+    Failing to call this and manually deleting the QPlatformScreen instead may
+    lead to a crash due to a pure virtual call.
+*/
+void QWindowSystemInterface::handleScreenRemoved(QPlatformScreen *platformScreen)
+{
+    // Important to keep this order since the QSceen doesn't own the platform screen
+    delete platformScreen->screen();
+    delete platformScreen;
+}
+
+/*!
+    Should be called whenever the primary screen changes.
+
+    When the screen specified as primary changes, this method will notify
+    QGuiApplication and emit the QGuiApplication::primaryScreenChanged signal.
+ */
+void QWindowSystemInterface::handlePrimaryScreenChanged(QPlatformScreen *newPrimary)
+{
+    QScreen *newPrimaryScreen = newPrimary->screen();
+    int indexOfScreen = QGuiApplicationPrivate::screen_list.indexOf(newPrimaryScreen);
+    Q_ASSERT(indexOfScreen >= 0);
+    if (indexOfScreen == 0)
+        return;
+
+    QGuiApplicationPrivate::screen_list.swapItemsAt(0, indexOfScreen);
+    emit qGuiApp->primaryScreenChanged(newPrimaryScreen);
+}
+
 void QWindowSystemInterface::handleScreenOrientationChange(QScreen *screen, Qt::ScreenOrientation orientation)
 {
     QWindowSystemInterfacePrivate::ScreenOrientationEvent *e =
diff --git a/src/gui/kernel/qwindowsysteminterface.h b/src/gui/kernel/qwindowsysteminterface.h
index 03b3bd16f0..fd70eda9ff 100644
--- a/src/gui/kernel/qwindowsysteminterface.h
+++ b/src/gui/kernel/qwindowsysteminterface.h
@@ -237,6 +237,10 @@ public:
 #endif
 
     // Changes to the screen
+    static void handleScreenAdded(QPlatformScreen *screen, bool isPrimary = false);
+    static void handleScreenRemoved(QPlatformScreen *screen);
+    static void handlePrimaryScreenChanged(QPlatformScreen *newPrimary);
+
     static void handleScreenOrientationChange(QScreen *screen, Qt::ScreenOrientation newOrientation);
     static void handleScreenGeometryChange(QScreen *screen, const QRect &newGeometry, const QRect &newAvailableGeometry);
     static void handleScreenLogicalDotsPerInchChange(QScreen *screen, qreal newDpiX, qreal newDpiY);
diff --git a/src/gui/text/qtextdocumentlayout.cpp b/src/gui/text/qtextdocumentlayout.cpp
index 323253c70d..2e1a2b5bff 100644
--- a/src/gui/text/qtextdocumentlayout.cpp
+++ b/src/gui/text/qtextdocumentlayout.cpp
@@ -58,23 +58,17 @@
 #include <limits.h>
 #include <qbasictimer.h>
 #include "private/qfunctions_p.h"
+#include <qloggingcategory.h>
 
 #include <algorithm>
 
-// #define LAYOUT_DEBUG
-
-#ifdef LAYOUT_DEBUG
-#define LDEBUG qDebug()
-#define INC_INDENT debug_indent += "  "
-#define DEC_INDENT debug_indent = debug_indent.left(debug_indent.length()-2)
-#else
-#define LDEBUG if(0) qDebug()
-#define INC_INDENT do {} while(0)
-#define DEC_INDENT do {} while(0)
-#endif
-
 QT_BEGIN_NAMESPACE
 
+Q_LOGGING_CATEGORY(lcDraw, "qt.text.drawing")
+Q_LOGGING_CATEGORY(lcHit, "qt.text.hittest")
+Q_LOGGING_CATEGORY(lcLayout, "qt.text.layout")
+Q_LOGGING_CATEGORY(lcTable, "qt.text.layout.table")
+
 // ################ should probably add frameFormatChange notification!
 
 struct QTextLayoutStruct;
@@ -583,16 +577,16 @@ QTextDocumentLayoutPrivate::hitTest(QTextFrame *frame, const QFixedPoint &point,
 
     QTextFrame *rootFrame = docPrivate->rootFrame();
 
-//     LDEBUG << "checking frame" << frame->firstPosition() << "point=" << point
-//            << "position" << fd->position << "size" << fd->size;
+    qCDebug(lcHit) << "checking frame" << frame->firstPosition() << "point=" << point.toPointF()
+                   << "position" << fd->position.toPointF() << "size" << fd->size.toSizeF();
     if (frame != rootFrame) {
         if (relativePoint.y < 0 || relativePoint.x < 0) {
             *position = frame->firstPosition() - 1;
-//             LDEBUG << "before pos=" << *position;
+            qCDebug(lcHit) << "before pos=" << *position;
             return PointBefore;
         } else if (relativePoint.y > fd->size.height || relativePoint.x > fd->size.width) {
             *position = frame->lastPosition() + 1;
-//             LDEBUG << "after pos=" << *position;
+            qCDebug(lcHit) << "after pos=" << *position;
             return PointAfter;
         }
     }
@@ -666,8 +660,6 @@ QTextDocumentLayoutPrivate::HitPoint
 QTextDocumentLayoutPrivate::hitTest(QTextFrame::Iterator it, HitPoint hit, const QFixedPoint &p,
                                     int *position, QTextLayout **l, Qt::HitTestAccuracy accuracy) const
 {
-    INC_INDENT;
-
     for (; !it.atEnd(); ++it) {
         QTextFrame *c = it.currentFrame();
         HitPoint hp;
@@ -693,8 +685,7 @@ QTextDocumentLayoutPrivate::hitTest(QTextFrame::Iterator it, HitPoint hit, const
         }
     }
 
-    DEC_INDENT;
-//     LDEBUG << "inside=" << hit << " pos=" << *position;
+    qCDebug(lcHit) << "inside=" << hit << " pos=" << *position;
     return hit;
 }
 
@@ -741,15 +732,14 @@ QTextDocumentLayoutPrivate::hitTest(const QTextBlock &bl, const QFixedPoint &poi
     QTextLayout *tl = bl.layout();
     QRectF textrect = tl->boundingRect();
     textrect.translate(tl->position());
-//     LDEBUG << "    checking block" << bl.position() << "point=" << point
-//            << "    tlrect" << textrect;
+    qCDebug(lcHit) << "    checking block" << bl.position() << "point=" << point.toPointF() << "    tlrect" << textrect;
     *position = bl.position();
     if (point.y.toReal() < textrect.top()) {
-//             LDEBUG << "    before pos=" << *position;
+        qCDebug(lcHit) << "    before pos=" << *position;
         return PointBefore;
     } else if (point.y.toReal() > textrect.bottom()) {
         *position += bl.length();
-//             LDEBUG << "    after pos=" << *position;
+        qCDebug(lcHit) << "    after pos=" << *position;
         return PointAfter;
     }
 
@@ -781,7 +771,7 @@ QTextDocumentLayoutPrivate::hitTest(const QTextBlock &bl, const QFixedPoint &poi
     }
     *position += off;
 
-//     LDEBUG << "    inside=" << hit << " pos=" << *position;
+    qCDebug(lcHit) << "    inside=" << hit << " pos=" << *position;
     return hit;
 }
 
@@ -944,8 +934,7 @@ void QTextDocumentLayoutPrivate::drawFrame(const QPointF &offset, QPainter *pain
             || off.x() > context.clip.right() || off.x() + fd->size.width.toReal() < context.clip.left()))
         return;
 
-//     LDEBUG << debug_indent << "drawFrame" << frame->firstPosition() << "--" << frame->lastPosition() << "at" << offset;
-//     INC_INDENT;
+     qCDebug(lcDraw) << "drawFrame" << frame->firstPosition() << "--" << frame->lastPosition() << "at" << offset;
 
     // if the cursor is /on/ a table border we may need to repaint it
     // afterwards, as we usually draw the decoration first
@@ -1076,8 +1065,6 @@ void QTextDocumentLayoutPrivate::drawFrame(const QPointF &offset, QPainter *pain
         painter->setPen(oldPen);
     }
 
-//     DEC_INDENT;
-
     return;
 }
 
@@ -1280,7 +1267,7 @@ void QTextDocumentLayoutPrivate::drawBlock(const QPointF &offset, QPainter *pain
     r.translate(offset + tl->position());
     if (!bl.isVisible() || (context.clip.isValid() && (r.bottom() < context.clip.y() || r.top() > context.clip.bottom())))
         return;
-//      LDEBUG << debug_indent << "drawBlock" << bl.position() << "at" << offset << "br" << tl->boundingRect();
+    qCDebug(lcDraw) << "drawBlock" << bl.position() << "at" << offset << "br" << tl->boundingRect();
 
     QTextBlockFormat blockFormat = bl.blockFormat();
 
@@ -1512,7 +1499,7 @@ QTextLayoutStruct QTextDocumentLayoutPrivate::layoutCell(QTextTable *t, const QT
                                                         int layoutFrom, int layoutTo, QTextTableData *td,
                                                         QFixed absoluteTableY, bool withPageBreaks)
 {
-    LDEBUG << "layoutCell";
+    qCDebug(lcTable) << "layoutCell";
     QTextLayoutStruct layoutStruct;
     layoutStruct.frame = t;
     layoutStruct.minimumWidth = 0;
@@ -1587,7 +1574,7 @@ QTextLayoutStruct QTextDocumentLayoutPrivate::layoutCell(QTextTable *t, const QT
 
 QRectF QTextDocumentLayoutPrivate::layoutTable(QTextTable *table, int layoutFrom, int layoutTo, QFixed parentY)
 {
-    LDEBUG << "layoutTable";
+    qCDebug(lcTable) << "layoutTable from" << layoutFrom << "to" << layoutTo << "parentY" << parentY;
     QTextTableData *td = static_cast<QTextTableData *>(data(table));
     Q_ASSERT(td->sizeDirty);
     const int rows = table->rows();
@@ -1709,6 +1696,7 @@ recalc_minmax_widths:
         if (length.type() == QTextLength::FixedLength) {
             td->minWidths[i] = td->widths[i] = qMax(scaleToDevice(QFixed::fromReal(length.rawValue())), td->minWidths.at(i));
             remainingWidth -= td->widths.at(i);
+            qCDebug(lcTable) << "column" << i << "has width constraint" << td->minWidths.at(i) << "px, remaining width now" << remainingWidth;
         } else if (length.type() == QTextLength::PercentageLength) {
             totalPercentage += QFixed::fromReal(length.rawValue());
         } else if (length.type() == QTextLength::VariableLength) {
@@ -1716,6 +1704,7 @@ recalc_minmax_widths:
 
             td->widths[i] = td->minWidths.at(i);
             remainingWidth -= td->minWidths.at(i);
+            qCDebug(lcTable) << "column" << i << "has variable width, min" << td->minWidths.at(i) << "remaining width now" << remainingWidth;
         }
         totalMinWidth += td->minWidths.at(i);
     }
@@ -1735,6 +1724,8 @@ recalc_minmax_widths:
                 } else {
                     td->widths[i] = td->minWidths.at(i);
                 }
+                qCDebug(lcTable) << "column" << i << "has width constraint" << columnWidthConstraints.at(i).rawValue()
+                                 << "%, allocated width" << td->widths[i] << "remaining width now" << remainingWidth;
                 remainingWidth -= td->widths.at(i);
             }
         }
@@ -1978,9 +1969,12 @@ relayout:
     td->minimumWidth += rightMargin - td->border;
 
     td->maximumWidth = td->columnPositions.at(0);
-    for (int i = 0; i < columns; ++i)
+    for (int i = 0; i < columns; ++i) {
         if (td->maxWidths.at(i) != QFIXED_MAX)
             td->maximumWidth += td->maxWidths.at(i) + 2 * td->border + cellSpacing;
+        qCDebug(lcTable) << "column" << i << "has final width" << td->widths.at(i).toReal()
+                         << "min" << td->minWidths.at(i).toReal() << "max" << td->maxWidths.at(i).toReal();
+    }
     td->maximumWidth += rightMargin - td->border;
 
     td->updateTableSize();
@@ -2052,9 +2046,8 @@ void QTextDocumentLayoutPrivate::positionFloat(QTextFrame *frame, QTextLine *cur
 
 QRectF QTextDocumentLayoutPrivate::layoutFrame(QTextFrame *f, int layoutFrom, int layoutTo, QFixed parentY)
 {
-    LDEBUG << "layoutFrame (pre)";
+    qCDebug(lcLayout, "layoutFrame (%d--%d), parent=%p", f->firstPosition(), f->lastPosition(), f->parentFrame());
     Q_ASSERT(data(f)->sizeDirty);
-//     qDebug("layouting frame (%d--%d), parent=%p", f->firstPosition(), f->lastPosition(), f->parentFrame());
 
     QTextFrameFormat fformat = f->frameFormat();
 
@@ -2076,9 +2069,8 @@ QRectF QTextDocumentLayoutPrivate::layoutFrame(QTextFrame *f, int layoutFrom, in
 
 QRectF QTextDocumentLayoutPrivate::layoutFrame(QTextFrame *f, int layoutFrom, int layoutTo, QFixed frameWidth, QFixed frameHeight, QFixed parentY)
 {
-    LDEBUG << "layoutFrame from=" << layoutFrom << "to=" << layoutTo;
+    qCDebug(lcLayout, "layoutFrame (%d--%d), parent=%p", f->firstPosition(), f->lastPosition(), f->parentFrame());
     Q_ASSERT(data(f)->sizeDirty);
-//     qDebug("layouting frame (%d--%d), parent=%p", f->firstPosition(), f->lastPosition(), f->parentFrame());
 
     QTextFrameData *fd = data(f);
     QFixed newContentsWidth;
@@ -2165,8 +2157,8 @@ QRectF QTextDocumentLayoutPrivate::layoutFrame(QTextFrame *f, int layoutFrom, in
     layoutStruct.maximumWidth = QFIXED_MAX;
     layoutStruct.fullLayout = fullLayout || (fd->oldContentsWidth != newContentsWidth);
     layoutStruct.updateRect = QRectF(QPointF(0, 0), QSizeF(qreal(INT_MAX), qreal(INT_MAX)));
-    LDEBUG << "layoutStruct: x_left" << layoutStruct.x_left << "x_right" << layoutStruct.x_right
-           << "fullLayout" << layoutStruct.fullLayout;
+    qCDebug(lcLayout) << "layoutStruct: x_left" << layoutStruct.x_left << "x_right" << layoutStruct.x_right
+                      << "fullLayout" << layoutStruct.fullLayout;
     fd->oldContentsWidth = newContentsWidth;
 
     layoutStruct.pageHeight = QFixed::fromReal(document->pageSize().height());
@@ -2220,7 +2212,7 @@ QRectF QTextDocumentLayoutPrivate::layoutFrame(QTextFrame *f, int layoutFrom, in
 void QTextDocumentLayoutPrivate::layoutFlow(QTextFrame::Iterator it, QTextLayoutStruct *layoutStruct,
                                             int layoutFrom, int layoutTo, QFixed width)
 {
-    LDEBUG << "layoutFlow from=" << layoutFrom << "to=" << layoutTo;
+    qCDebug(lcLayout) << "layoutFlow from=" << layoutFrom << "to=" << layoutTo;
     QTextFrameData *fd = data(layoutStruct->frame);
 
     fd->currentLayoutStruct = layoutStruct;
@@ -2578,9 +2570,8 @@ void QTextDocumentLayoutPrivate::layoutBlock(const QTextBlock &bl, int blockPosi
     QTextLayout *tl = bl.layout();
     const int blockLength = bl.length();
 
-    LDEBUG << "layoutBlock from=" << layoutFrom << "to=" << layoutTo;
-
-//    qDebug() << "layoutBlock; width" << layoutStruct->x_right - layoutStruct->x_left << "(maxWidth is btw" << tl->maximumWidth() << ')';
+    qCDebug(lcLayout) << "layoutBlock from=" << layoutFrom << "to=" << layoutTo
+                      << "; width" << layoutStruct->x_right - layoutStruct->x_left << "(maxWidth is btw" << tl->maximumWidth() << ')';
 
     if (previousBlockFormat) {
         qreal margin = qMax(blockFormat.topMargin(), previousBlockFormat->bottomMargin());
@@ -2612,7 +2603,7 @@ void QTextDocumentLayoutPrivate::layoutBlock(const QTextBlock &bl, int blockPosi
         // force relayout if we cross a page boundary
         || (layoutStruct->pageHeight != QFIXED_MAX && layoutStruct->absoluteY() + QFixed::fromReal(tl->boundingRect().height()) > layoutStruct->pageBottom)) {
 
-        LDEBUG << " do layout";
+        qCDebug(lcLayout) << "do layout";
         QTextOption option = docPrivate->defaultTextOption;
         option.setTextDirection(dir);
         option.setTabs( blockFormat.tabPositions() );
@@ -2741,7 +2732,7 @@ void QTextDocumentLayoutPrivate::layoutBlock(const QTextBlock &bl, int blockPosi
         const int cnt = tl->lineCount();
         QFixed bottom;
         for (int i = 0; i < cnt; ++i) {
-            LDEBUG << "going to move text line" << i;
+            qCDebug(lcLayout) << "going to move text line" << i;
             QTextLine line = tl->lineAt(i);
             layoutStruct->contentsWidth
                 = qMax(layoutStruct->contentsWidth, QFixed::fromReal(line.x() + tl->lineAt(i).naturalTextWidth()) + totalRightMargin);
diff --git a/src/network/access/qnetworkaccessmanager.cpp b/src/network/access/qnetworkaccessmanager.cpp
index 62c915908b..50b9488594 100644
--- a/src/network/access/qnetworkaccessmanager.cpp
+++ b/src/network/access/qnetworkaccessmanager.cpp
@@ -1390,7 +1390,8 @@ QNetworkReply *QNetworkAccessManager::createRequest(QNetworkAccessManager::Opera
     QString scheme = req.url().scheme();
 
 #ifdef Q_OS_WASM
-    if (scheme == QLatin1String("http") || scheme == QLatin1String("https")) {
+    // Support http, https, and relateive urls
+    if (scheme == QLatin1String("http") || scheme == QLatin1String("https") || scheme.isEmpty()) {
         QNetworkReplyWasmImpl *reply = new QNetworkReplyWasmImpl(this);
         QNetworkReplyWasmImplPrivate *priv = reply->d_func();
         priv->manager = this;
diff --git a/src/network/configure.json b/src/network/configure.json
index be9e35c7fe..56805da7b2 100644
--- a/src/network/configure.json
+++ b/src/network/configure.json
@@ -86,11 +86,11 @@
             "sources": [
                 { "type": "openssl" },
                 {
-                    "libs": "-lssleay32 -llibeay32",
+                    "libs": "-lssleay32 -llibeay32 -lUser32 -lWs2_32 -lAdvapi32 -lGdi32",
                     "condition": "config.win32"
                 },
                 {
-                    "libs": "-llibssl -llibcrypto",
+                    "libs": "-llibssl -llibcrypto -lUser32 -lWs2_32 -lAdvapi32 -lCrypt32",
                     "condition": "config.msvc"
                 },
                 {
diff --git a/src/platformsupport/fontdatabases/fontconfig/qfontconfigdatabase.cpp b/src/platformsupport/fontdatabases/fontconfig/qfontconfigdatabase.cpp
index aa8f9a892a..e545d54ec2 100644
--- a/src/platformsupport/fontdatabases/fontconfig/qfontconfigdatabase.cpp
+++ b/src/platformsupport/fontdatabases/fontconfig/qfontconfigdatabase.cpp
@@ -908,7 +908,7 @@ QFont QFontconfigDatabase::defaultFont() const
 void QFontconfigDatabase::setupFontEngine(QFontEngineFT *engine, const QFontDef &fontDef) const
 {
     bool antialias = !(fontDef.styleStrategy & QFont::NoAntialias);
-    bool forcedAntialiasSetting = !antialias;
+    bool forcedAntialiasSetting = !antialias || QHighDpiScaling::isActive();
 
     const QPlatformServices *services = QGuiApplicationPrivate::platformIntegration()->services();
     bool useXftConf = false;
diff --git a/src/platformsupport/glxconvenience/qglxconvenience.cpp b/src/platformsupport/glxconvenience/qglxconvenience.cpp
index 40521ef6da..6458454336 100644
--- a/src/platformsupport/glxconvenience/qglxconvenience.cpp
+++ b/src/platformsupport/glxconvenience/qglxconvenience.cpp
@@ -223,6 +223,7 @@ GLXFBConfig qglx_findConfig(Display *display, int screen , QSurfaceFormat format
                     continue;
             }
 
+            QXlibPointer<XVisualInfo> visual(glXGetVisualFromFBConfig(display, candidate));
             int actualRed;
             int actualGreen;
             int actualBlue;
@@ -231,7 +232,8 @@ GLXFBConfig qglx_findConfig(Display *display, int screen , QSurfaceFormat format
             glXGetFBConfigAttrib(display, candidate, GLX_GREEN_SIZE, &actualGreen);
             glXGetFBConfigAttrib(display, candidate, GLX_BLUE_SIZE, &actualBlue);
             glXGetFBConfigAttrib(display, candidate, GLX_ALPHA_SIZE, &actualAlpha);
-
+            // Sometimes the visuals don't have a depth that includes the alpha channel.
+            actualAlpha = qMin(actualAlpha, visual->depth - actualRed - actualGreen - actualBlue);
 
             if (requestedRed && actualRed < requestedRed)
                 continue;
diff --git a/src/platformsupport/input/xkbcommon/xkbcommon.pro b/src/platformsupport/input/xkbcommon/xkbcommon.pro
index 2f5d132b5c..22b16ae44a 100644
--- a/src/platformsupport/input/xkbcommon/xkbcommon.pro
+++ b/src/platformsupport/input/xkbcommon/xkbcommon.pro
@@ -7,7 +7,7 @@ CONFIG += static internal_module
 DEFINES += QT_NO_CAST_FROM_ASCII
 PRECOMPILED_HEADER = ../../../corelib/global/qt_pch.h
 
-QMAKE_USE_PRIVATE += xkbcommon
+QMAKE_USE += xkbcommon
 
 HEADERS += \
     qxkbcommon_p.h
diff --git a/src/plugins/platforminputcontexts/ibus/ibus.pro b/src/plugins/platforminputcontexts/ibus/ibus.pro
index 52836bb8b6..9ba2297e38 100644
--- a/src/plugins/platforminputcontexts/ibus/ibus.pro
+++ b/src/plugins/platforminputcontexts/ibus/ibus.pro
@@ -1,6 +1,6 @@
 TARGET = ibusplatforminputcontextplugin
 
-QT += dbus gui-private
+QT += dbus gui-private xkbcommon_support-private
 SOURCES += $$PWD/qibusplatforminputcontext.cpp \
            $$PWD/qibusproxy.cpp \
            $$PWD/qibusproxyportal.cpp \
diff --git a/src/plugins/platforminputcontexts/ibus/qibusplatforminputcontext.cpp b/src/plugins/platforminputcontexts/ibus/qibusplatforminputcontext.cpp
index 7e66439ea7..f2429f24ff 100644
--- a/src/plugins/platforminputcontexts/ibus/qibusplatforminputcontext.cpp
+++ b/src/plugins/platforminputcontexts/ibus/qibusplatforminputcontext.cpp
@@ -51,6 +51,8 @@
 
 #include <QtGui/private/qguiapplication_p.h>
 
+#include <QtXkbCommonSupport/private/qxkbcommon_p.h>
+
 #include "qibusproxy.h"
 #include "qibusproxyportal.h"
 #include "qibusinputcontextproxy.h"
@@ -335,14 +337,12 @@ void QIBusPlatformInputContext::forwardKeyEvent(uint keyval, uint keycode, uint
     if (!input)
         return;
 
-    if (debug)
-        qDebug() << "forwardKeyEvent" << keyval << keycode << state;
-
     QEvent::Type type = QEvent::KeyPress;
     if (state & IBUS_RELEASE_MASK)
         type = QEvent::KeyRelease;
 
     state &= ~IBUS_RELEASE_MASK;
+    keycode += 8;
 
     Qt::KeyboardModifiers modifiers = Qt::NoModifier;
     if (state & IBUS_SHIFT_MASK)
@@ -354,7 +354,13 @@ void QIBusPlatformInputContext::forwardKeyEvent(uint keyval, uint keycode, uint
     if (state & IBUS_META_MASK)
         modifiers |= Qt::MetaModifier;
 
-    QKeyEvent event(type, keyval, modifiers, QString(keyval));
+    int qtcode = QXkbCommon::keysymToQtKey(keyval, modifiers);
+    QString text = QXkbCommon::lookupStringNoKeysymTransformations(keyval);
+
+    if (debug)
+        qDebug() << "forwardKeyEvent" << keyval << keycode << state << modifiers << qtcode << text;
+
+    QKeyEvent event(type, qtcode, modifiers, keycode, keyval, state, text);
     QCoreApplication::sendEvent(input, &event);
 }
 
diff --git a/src/plugins/platforminputcontexts/platforminputcontexts.pro b/src/plugins/platforminputcontexts/platforminputcontexts.pro
index 68f6792377..56a39a49e7 100644
--- a/src/plugins/platforminputcontexts/platforminputcontexts.pro
+++ b/src/plugins/platforminputcontexts/platforminputcontexts.pro
@@ -1,10 +1,11 @@
 TEMPLATE = subdirs
 QT_FOR_CONFIG += gui-private
 
-qtHaveModule(dbus) {
-!mac:!win32:SUBDIRS += ibus
-}
-
-qtConfig(xkbcommon): SUBDIRS += compose
+qtConfig(xkbcommon) {
+    SUBDIRS += compose
 
+    qtHaveModule(dbus) {
+        !macos:!win32:SUBDIRS += ibus
+    }
+}
 
diff --git a/src/plugins/platforms/android/qandroidplatformintegration.cpp b/src/plugins/platforms/android/qandroidplatformintegration.cpp
index 763b294660..e0c437be27 100644
--- a/src/plugins/platforms/android/qandroidplatformintegration.cpp
+++ b/src/plugins/platforms/android/qandroidplatformintegration.cpp
@@ -173,7 +173,7 @@ QAndroidPlatformIntegration::QAndroidPlatformIntegration(const QStringList &para
         qFatal("Could not bind GL_ES API");
 
     m_primaryScreen = new QAndroidPlatformScreen();
-    screenAdded(m_primaryScreen);
+    QWindowSystemInterface::handleScreenAdded(m_primaryScreen);
     m_primaryScreen->setPhysicalSize(QSize(m_defaultPhysicalSizeWidth, m_defaultPhysicalSizeHeight));
     m_primaryScreen->setSize(QSize(m_defaultScreenWidth, m_defaultScreenHeight));
     m_primaryScreen->setAvailableGeometry(QRect(0, 0, m_defaultGeometryWidth, m_defaultGeometryHeight));
diff --git a/src/plugins/platforms/bsdfb/qbsdfbintegration.cpp b/src/plugins/platforms/bsdfb/qbsdfbintegration.cpp
index 6a7d445e69..e4c90d26af 100644
--- a/src/plugins/platforms/bsdfb/qbsdfbintegration.cpp
+++ b/src/plugins/platforms/bsdfb/qbsdfbintegration.cpp
@@ -53,6 +53,7 @@
 #include <QtGui/private/qguiapplication_p.h>
 #include <qpa/qplatforminputcontext.h>
 #include <qpa/qplatforminputcontextfactory_p.h>
+#include <qpa/qwindowsysteminterface.h>
 
 #if QT_CONFIG(tslib)
 #include <QtInputSupport/private/qtslib_p.h>
@@ -69,13 +70,13 @@ QBsdFbIntegration::QBsdFbIntegration(const QStringList &paramList)
 
 QBsdFbIntegration::~QBsdFbIntegration()
 {
-    destroyScreen(m_primaryScreen.take());
+    QWindowSystemInterface::handleScreenRemoved(m_primaryScreen.take());
 }
 
 void QBsdFbIntegration::initialize()
 {
     if (m_primaryScreen->initialize())
-        screenAdded(m_primaryScreen.data());
+        QWindowSystemInterface::handleScreenAdded(m_primaryScreen.data());
     else
         qWarning("bsdfb: Failed to initialize screen");
 
diff --git a/src/plugins/platforms/cocoa/cocoa.pro b/src/plugins/platforms/cocoa/cocoa.pro
index 8d65cf328f..083b7c1655 100644
--- a/src/plugins/platforms/cocoa/cocoa.pro
+++ b/src/plugins/platforms/cocoa/cocoa.pro
@@ -33,6 +33,7 @@ SOURCES += main.mm \
     qcocoaintrospection.mm \
     qcocoakeymapper.mm \
     qcocoamimetypes.mm \
+    qiosurfacegraphicsbuffer.mm \
     messages.cpp
 
 HEADERS += qcocoaintegration.h \
@@ -67,6 +68,7 @@ HEADERS += qcocoaintegration.h \
     qcocoaintrospection.h \
     qcocoakeymapper.h \
     messages.h \
+    qiosurfacegraphicsbuffer.h \
     qcocoamimetypes.h
 
 qtConfig(opengl.*) {
@@ -81,7 +83,7 @@ qtConfig(vulkan) {
 
 RESOURCES += qcocoaresources.qrc
 
-LIBS += -framework AppKit -framework CoreServices -framework Carbon -framework IOKit -framework QuartzCore -framework CoreVideo -framework Metal -lcups
+LIBS += -framework AppKit -framework CoreServices -framework Carbon -framework IOKit -framework QuartzCore -framework CoreVideo -framework Metal -framework IOSurface -lcups
 
 QT += \
     core-private gui-private \
diff --git a/src/plugins/platforms/cocoa/qcocoabackingstore.h b/src/plugins/platforms/cocoa/qcocoabackingstore.h
index b4cd506513..508f24d578 100644
--- a/src/plugins/platforms/cocoa/qcocoabackingstore.h
+++ b/src/plugins/platforms/cocoa/qcocoabackingstore.h
@@ -44,13 +44,16 @@
 
 #include <private/qcore_mac_p.h>
 
+#include <QScopedPointer>
+#include "qiosurfacegraphicsbuffer.h"
+
 QT_BEGIN_NAMESPACE
 
-class QCocoaBackingStore : public QRasterBackingStore
+class QNSWindowBackingStore : public QRasterBackingStore
 {
 public:
-    QCocoaBackingStore(QWindow *window);
-    ~QCocoaBackingStore();
+    QNSWindowBackingStore(QWindow *window);
+    ~QNSWindowBackingStore();
 
     void flush(QWindow *, const QRegion &, const QPoint &) override;
 
@@ -60,6 +63,49 @@ private:
     void redrawRoundedBottomCorners(CGRect) const;
 };
 
+class QCALayerBackingStore : public QPlatformBackingStore
+{
+public:
+    QCALayerBackingStore(QWindow *window);
+    ~QCALayerBackingStore();
+
+    void resize(const QSize &size, const QRegion &staticContents) override;
+
+    void beginPaint(const QRegion &region) override;
+    QPaintDevice *paintDevice() override;
+    void endPaint() override;
+
+    void flush(QWindow *, const QRegion &, const QPoint &) override;
+    void composeAndFlush(QWindow *window, const QRegion &region, const QPoint &offset,
+        QPlatformTextureList *textures, bool translucentBackground) override;
+
+    QPlatformGraphicsBuffer *graphicsBuffer() const override;
+
+private:
+    QSize m_requestedSize;
+    QRegion m_paintedRegion;
+
+    class GraphicsBuffer : public QIOSurfaceGraphicsBuffer
+    {
+    public:
+        GraphicsBuffer(const QSize &size, qreal devicePixelRatio,
+                const QPixelFormat &format, QCFType<CGColorSpaceRef> colorSpace);
+
+        QRegion dirtyRegion; // In unscaled coordinates
+        QImage *asImage();
+
+    private:
+        qreal m_devicePixelRatio;
+        QImage m_image;
+    };
+
+    void ensureBackBuffer();
+    bool recreateBackBufferIfNeeded();
+    bool prepareForFlush();
+
+    std::list<std::unique_ptr<GraphicsBuffer>> m_buffers;
+};
+
 QT_END_NAMESPACE
 
 #endif
diff --git a/src/plugins/platforms/cocoa/qcocoabackingstore.mm b/src/plugins/platforms/cocoa/qcocoabackingstore.mm
index 81a0a7d040..8e4e928bc5 100644
--- a/src/plugins/platforms/cocoa/qcocoabackingstore.mm
+++ b/src/plugins/platforms/cocoa/qcocoabackingstore.mm
@@ -42,24 +42,28 @@
 #include "qcocoawindow.h"
 #include "qcocoahelpers.h"
 
+#include <QtCore/qmath.h>
+
+#include <QuartzCore/CATransaction.h>
+
 QT_BEGIN_NAMESPACE
 
-QCocoaBackingStore::QCocoaBackingStore(QWindow *window)
+QNSWindowBackingStore::QNSWindowBackingStore(QWindow *window)
     : QRasterBackingStore(window)
 {
 }
 
-QCocoaBackingStore::~QCocoaBackingStore()
+QNSWindowBackingStore::~QNSWindowBackingStore()
 {
 }
 
-bool QCocoaBackingStore::windowHasUnifiedToolbar() const
+bool QNSWindowBackingStore::windowHasUnifiedToolbar() const
 {
     Q_ASSERT(window()->handle());
     return static_cast<QCocoaWindow *>(window()->handle())->m_drawContentBorderGradient;
 }
 
-QImage::Format QCocoaBackingStore::format() const
+QImage::Format QNSWindowBackingStore::format() const
 {
     if (windowHasUnifiedToolbar())
         return QImage::Format_ARGB32_Premultiplied;
@@ -78,7 +82,7 @@ QImage::Format QCocoaBackingStore::format() const
     coordinates, and the \a offset will be the child window's offset in relation
     to the backingstore's top level window.
 */
-void QCocoaBackingStore::flush(QWindow *window, const QRegion &region, const QPoint &offset)
+void QNSWindowBackingStore::flush(QWindow *window, const QRegion &region, const QPoint &offset)
 {
     if (m_image.isNull())
         return;
@@ -103,131 +107,113 @@ void QCocoaBackingStore::flush(QWindow *window, const QRegion &region, const QPo
         qCDebug(lcQpaBackingStore) << "Flushing" << region << "of" << view << qPrintable(targetViewDescription);
     }
 
-    // Prevent potentially costly color conversion by assigning the display color space
-    // to the backingstore image. This does not copy the underlying image data.
-    CGColorSpaceRef displayColorSpace = view.window.screen.colorSpace.CGColorSpace;
-    QCFType<CGImageRef> cgImage = CGImageCreateCopyWithColorSpace(
-        QCFType<CGImageRef>(m_image.toCGImage()), displayColorSpace);
-
-    if (view.layer) {
-        // In layer-backed mode, locking focus on a view does not give the right
-        // view transformation, and doesn't give us a graphics context to render
-        // via when drawing outside of the display cycle. Instead we tell AppKit
-        // that we want to update the layer's content, via [NSView wantsUpdateLayer],
-        // which result in AppKit not creating a backingstore for each layer, and
-        // we then directly set the layer's backingstore (content) to our backingstore,
-        // masked to the part of the subview that is relevant.
-        // FIXME: Figure out if there's a way to do partial updates
-        view.layer.contents = (__bridge id)static_cast<CGImageRef>(cgImage);
-        if (view != topLevelView) {
-            const CGSize topLevelSize = topLevelView.bounds.size;
-            view.layer.contentsRect = CGRectApplyAffineTransform(
-                [view convertRect:view.bounds toView:topLevelView],
-                // The contentsRect is in unit coordinate system
-                CGAffineTransformMakeScale(1.0 / topLevelSize.width, 1.0 / topLevelSize.height));
-        }
-    } else {
-        // Normally a NSView is drawn via drawRect, as part of the display cycle in the
-        // main runloop, via setNeedsDisplay and friends. AppKit will lock focus on each
-        // individual view, starting with the top level and then traversing any subviews,
-        // calling drawRect for each of them. This pull model results in expose events
-        // sent to Qt, which result in drawing to the backingstore and flushing it.
-        // Qt may also decide to paint and flush the backingstore via e.g. timers,
-        // or other events such as mouse events, in which case we're in a push model.
-        // If there is no focused view, it means we're in the latter case, and need
-        // to manually flush the NSWindow after drawing to its graphic context.
-        const bool drawingOutsideOfDisplayCycle = ![NSView focusView];
-
-        // We also need to ensure the flushed view has focus, so that the graphics
-        // context is set up correctly (coordinate system, clipping, etc). Outside
-        // of the normal display cycle there is no focused view, as explained above,
-        // so we have to handle it manually. There's also a corner case inside the
-        // normal display cycle due to way QWidgetBackingStore composits native child
-        // widgets, where we'll get a flush of a native child during the drawRect of
-        // its parent/ancestor, and the parent/ancestor being the one locked by AppKit.
-        // In this case we also need to lock and unlock focus manually.
-        const bool shouldHandleViewLockManually = [NSView focusView] != view;
-        if (shouldHandleViewLockManually && ![view lockFocusIfCanDraw]) {
-            qWarning() << "failed to lock focus of" << view;
-            return;
-        }
+    // Normally a NSView is drawn via drawRect, as part of the display cycle in the
+    // main runloop, via setNeedsDisplay and friends. AppKit will lock focus on each
+    // individual view, starting with the top level and then traversing any subviews,
+    // calling drawRect for each of them. This pull model results in expose events
+    // sent to Qt, which result in drawing to the backingstore and flushing it.
+    // Qt may also decide to paint and flush the backingstore via e.g. timers,
+    // or other events such as mouse events, in which case we're in a push model.
+    // If there is no focused view, it means we're in the latter case, and need
+    // to manually flush the NSWindow after drawing to its graphic context.
+    const bool drawingOutsideOfDisplayCycle = ![NSView focusView];
+
+    // We also need to ensure the flushed view has focus, so that the graphics
+    // context is set up correctly (coordinate system, clipping, etc). Outside
+    // of the normal display cycle there is no focused view, as explained above,
+    // so we have to handle it manually. There's also a corner case inside the
+    // normal display cycle due to way QWidgetBackingStore composits native child
+    // widgets, where we'll get a flush of a native child during the drawRect of
+    // its parent/ancestor, and the parent/ancestor being the one locked by AppKit.
+    // In this case we also need to lock and unlock focus manually.
+    const bool shouldHandleViewLockManually = [NSView focusView] != view;
+    if (shouldHandleViewLockManually && ![view lockFocusIfCanDraw]) {
+        qWarning() << "failed to lock focus of" << view;
+        return;
+    }
 
-        const qreal devicePixelRatio = m_image.devicePixelRatio();
+    const qreal devicePixelRatio = m_image.devicePixelRatio();
 
-        // If the flushed window is a content view, and we're filling the drawn area
-        // completely, or it doesn't have a window background we need to preserve,
-        // we can get away with copying instead of blending the backing store.
-        QCocoaWindow *cocoaWindow = static_cast<QCocoaWindow *>(window->handle());
-        const NSCompositingOperation compositingOperation = cocoaWindow->isContentView()
-            && (cocoaWindow->isOpaque() || view.window.backgroundColor == NSColor.clearColor)
-                ? NSCompositingOperationCopy : NSCompositingOperationSourceOver;
+    // If the flushed window is a content view, and we're filling the drawn area
+    // completely, or it doesn't have a window background we need to preserve,
+    // we can get away with copying instead of blending the backing store.
+    QCocoaWindow *cocoaWindow = static_cast<QCocoaWindow *>(window->handle());
+    const NSCompositingOperation compositingOperation = cocoaWindow->isContentView()
+        && (cocoaWindow->isOpaque() || view.window.backgroundColor == NSColor.clearColor)
+            ? NSCompositingOperationCopy : NSCompositingOperationSourceOver;
 
 #ifdef QT_DEBUG
-        static bool debugBackingStoreFlush = [[NSUserDefaults standardUserDefaults]
-            boolForKey:@"QtCocoaDebugBackingStoreFlush"];
+    static bool debugBackingStoreFlush = [[NSUserDefaults standardUserDefaults]
+        boolForKey:@"QtCocoaDebugBackingStoreFlush"];
 #endif
 
-        // -------------------------------------------------------------------------
+    // -------------------------------------------------------------------------
 
-        // The current contexts is typically a NSWindowGraphicsContext, but can be
-        // NSBitmapGraphicsContext e.g. when debugging the view hierarchy in Xcode.
-        // If we need to distinguish things here in the future, we can use e.g.
-        // [NSGraphicsContext drawingToScreen], or the attributes of the context.
-        NSGraphicsContext *graphicsContext = [NSGraphicsContext currentContext];
-        Q_ASSERT_X(graphicsContext, "QCocoaBackingStore",
-            "Focusing the view should give us a current graphics context");
+    // The current contexts is typically a NSWindowGraphicsContext, but can be
+    // NSBitmapGraphicsContext e.g. when debugging the view hierarchy in Xcode.
+    // If we need to distinguish things here in the future, we can use e.g.
+    // [NSGraphicsContext drawingToScreen], or the attributes of the context.
+    NSGraphicsContext *graphicsContext = [NSGraphicsContext currentContext];
+    Q_ASSERT_X(graphicsContext, "QCocoaBackingStore",
+        "Focusing the view should give us a current graphics context");
 
-        // Create temporary image to use for blitting, without copying image data
-        NSImage *backingStoreImage = [[[NSImage alloc] initWithCGImage:cgImage size:NSZeroSize] autorelease];
+    // Prevent potentially costly color conversion by assigning the display color space
+    // to the backingstore image. This does not copy the underlying image data.
+    CGColorSpaceRef displayColorSpace = view.window.screen.colorSpace.CGColorSpace;
+    QCFType<CGImageRef> cgImage = CGImageCreateCopyWithColorSpace(
+        QCFType<CGImageRef>(m_image.toCGImage()), displayColorSpace);
 
-        QRegion clippedRegion = region;
-        for (QWindow *w = window; w; w = w->parent()) {
-            if (!w->mask().isEmpty()) {
-                clippedRegion &= w == window ? w->mask()
-                    : w->mask().translated(window->mapFromGlobal(w->mapToGlobal(QPoint(0, 0))));
-            }
+    // Create temporary image to use for blitting, without copying image data
+    NSImage *backingStoreImage = [[[NSImage alloc] initWithCGImage:cgImage size:NSZeroSize] autorelease];
+
+    QRegion clippedRegion = region;
+    for (QWindow *w = window; w; w = w->parent()) {
+        if (!w->mask().isEmpty()) {
+            clippedRegion &= w == window ? w->mask()
+                : w->mask().translated(window->mapFromGlobal(w->mapToGlobal(QPoint(0, 0))));
         }
+    }
 
-        for (const QRect &viewLocalRect : clippedRegion) {
-            QPoint backingStoreOffset = viewLocalRect.topLeft() + offset;
-            QRect backingStoreRect(backingStoreOffset * devicePixelRatio, viewLocalRect.size() * devicePixelRatio);
-            if (graphicsContext.flipped) // Flip backingStoreRect to match graphics context
-                backingStoreRect.moveTop(m_image.height() - (backingStoreRect.y() + backingStoreRect.height()));
+    for (const QRect &viewLocalRect : clippedRegion) {
+        QPoint backingStoreOffset = viewLocalRect.topLeft() + offset;
+        QRect backingStoreRect(backingStoreOffset * devicePixelRatio, viewLocalRect.size() * devicePixelRatio);
+        if (graphicsContext.flipped) // Flip backingStoreRect to match graphics context
+            backingStoreRect.moveTop(m_image.height() - (backingStoreRect.y() + backingStoreRect.height()));
 
-            CGRect viewRect = viewLocalRect.toCGRect();
+        CGRect viewRect = viewLocalRect.toCGRect();
 
-            if (windowHasUnifiedToolbar())
-                NSDrawWindowBackground(viewRect);
+        if (windowHasUnifiedToolbar())
+            NSDrawWindowBackground(viewRect);
 
-            [backingStoreImage drawInRect:viewRect fromRect:backingStoreRect.toCGRect()
-                operation:compositingOperation fraction:1.0 respectFlipped:YES hints:nil];
+        [backingStoreImage drawInRect:viewRect fromRect:backingStoreRect.toCGRect()
+            operation:compositingOperation fraction:1.0 respectFlipped:YES hints:nil];
 
 #ifdef QT_DEBUG
-            if (Q_UNLIKELY(debugBackingStoreFlush)) {
-                [[NSColor colorWithCalibratedRed:drand48() green:drand48() blue:drand48() alpha:0.3] set];
-                [NSBezierPath fillRect:viewRect];
-
-                if (drawingOutsideOfDisplayCycle) {
-                    [[[NSColor magentaColor] colorWithAlphaComponent:0.5] set];
-                    [NSBezierPath strokeLineFromPoint:viewLocalRect.topLeft().toCGPoint()
-                        toPoint:viewLocalRect.bottomRight().toCGPoint()];
-                }
+        if (Q_UNLIKELY(debugBackingStoreFlush)) {
+            [[NSColor colorWithCalibratedRed:drand48() green:drand48() blue:drand48() alpha:0.3] set];
+            [NSBezierPath fillRect:viewRect];
+
+            if (drawingOutsideOfDisplayCycle) {
+                [[[NSColor magentaColor] colorWithAlphaComponent:0.5] set];
+                [NSBezierPath strokeLineFromPoint:viewLocalRect.topLeft().toCGPoint()
+                    toPoint:viewLocalRect.bottomRight().toCGPoint()];
             }
-#endif
         }
+#endif
+    }
 
-        // -------------------------------------------------------------------------
+    // -------------------------------------------------------------------------
 
-        if (shouldHandleViewLockManually)
-            [view unlockFocus];
+    if (shouldHandleViewLockManually)
+        [view unlockFocus];
 
-        if (drawingOutsideOfDisplayCycle) {
-            redrawRoundedBottomCorners([view convertRect:region.boundingRect().toCGRect() toView:nil]);
-            [view.window flushWindow];
-        }
+    if (drawingOutsideOfDisplayCycle) {
+        redrawRoundedBottomCorners([view convertRect:region.boundingRect().toCGRect() toView:nil]);
+        [view.window flushWindow];
     }
 
-    // Done flushing to either CALayer or NSWindow backingstore
+
+    // Done flushing to NSWindow backingstore
 
     QCocoaWindow *topLevelCocoaWindow = static_cast<QCocoaWindow *>(topLevelWindow->handle());
     if (Q_UNLIKELY(topLevelCocoaWindow->m_needsInvalidateShadow)) {
@@ -251,7 +237,7 @@ void QCocoaBackingStore::flush(QWindow *window, const QRegion &region, const QPo
 
     https://trac.webkit.org/changeset/85376/webkit
 */
-void QCocoaBackingStore::redrawRoundedBottomCorners(CGRect windowRect) const
+void QNSWindowBackingStore::redrawRoundedBottomCorners(CGRect windowRect) const
 {
 #if !defined(QT_APPLE_NO_PRIVATE_APIS)
     Q_ASSERT(this->window()->handle());
@@ -285,4 +271,345 @@ void QCocoaBackingStore::redrawRoundedBottomCorners(CGRect windowRect) const
 #endif
 }
 
+// ----------------------------------------------------------------------------
+
+// https://stackoverflow.com/a/52722575/2761869
+template<class R>
+struct backwards_t {
+  R r;
+  constexpr auto begin() const { using std::rbegin; return rbegin(r); }
+  constexpr auto begin() { using std::rbegin; return rbegin(r); }
+  constexpr auto end() const { using std::rend; return rend(r); }
+  constexpr auto end() { using std::rend; return rend(r); }
+};
+template<class R>
+constexpr backwards_t<R> backwards(R&& r) { return {std::forward<R>(r)}; }
+
+QCALayerBackingStore::QCALayerBackingStore(QWindow *window)
+    : QPlatformBackingStore(window)
+{
+    qCDebug(lcQpaBackingStore) << "Creating QCALayerBackingStore for" << window;
+    m_buffers.resize(1);
+}
+
+QCALayerBackingStore::~QCALayerBackingStore()
+{
+}
+
+void QCALayerBackingStore::resize(const QSize &size, const QRegion &staticContents)
+{
+    qCDebug(lcQpaBackingStore) << "Resize requested to" << size;
+
+    if (!staticContents.isNull())
+        qCWarning(lcQpaBackingStore) << "QCALayerBackingStore does not support static contents";
+
+    m_requestedSize = size;
+}
+
+void QCALayerBackingStore::beginPaint(const QRegion &region)
+{
+    Q_UNUSED(region);
+
+    QMacAutoReleasePool pool;
+
+    qCInfo(lcQpaBackingStore) << "Beginning paint of" << region << "into backingstore of" << m_requestedSize;
+
+    ensureBackBuffer(); // Find an unused back buffer, or reserve space for a new one
+
+    const bool bufferWasRecreated = recreateBackBufferIfNeeded();
+
+    m_buffers.back()->lock(QPlatformGraphicsBuffer::SWWriteAccess);
+
+    // Although undocumented, QBackingStore::beginPaint expects the painted region
+    // to be cleared before use if the window has a surface format with an alpha.
+    // Fresh IOSurfaces are already cleared, so we don't need to clear those.
+    if (!bufferWasRecreated && window()->format().hasAlpha()) {
+        qCDebug(lcQpaBackingStore) << "Clearing" << region << "before use";
+        QPainter painter(m_buffers.back()->asImage());
+        painter.setCompositionMode(QPainter::CompositionMode_Source);
+        for (const QRect &rect : region)
+            painter.fillRect(rect, Qt::transparent);
+    }
+
+    m_paintedRegion += region;
+}
+
+void QCALayerBackingStore::ensureBackBuffer()
+{
+    if (window()->format().swapBehavior() == QSurfaceFormat::SingleBuffer)
+        return;
+
+    // The current back buffer may have been assigned to a layer in a previous flush,
+    // but we deferred the swap. Do it now if the surface has been picked up by CA.
+    if (m_buffers.back() && m_buffers.back()->isInUse() && m_buffers.back() != m_buffers.front()) {
+        qCInfo(lcQpaBackingStore) << "Back buffer has been picked up by CA, swapping to front";
+        std::swap(m_buffers.back(), m_buffers.front());
+    }
+
+    if (Q_UNLIKELY(lcQpaBackingStore().isDebugEnabled())) {
+        // ┌───────┬───────┬───────┬─────┬──────┐
+        // │ front ┊ spare ┊ spare ┊ ... ┊ back │
+        // └───────┴───────┴───────┴─────┴──────┘
+        for (const auto &buffer : m_buffers) {
+            qCDebug(lcQpaBackingStore).nospace() << "  "
+                << (buffer == m_buffers.front() ? "front" :
+                    buffer == m_buffers.back()  ? " back" :
+                                                  "spare"
+                ) << ": " << buffer.get();
+        }
+    }
+
+    // Ensure our back buffer is ready to draw into. If not, find a buffer that
+    // is not in use, or reserve space for a new buffer if none can be found.
+    for (auto &buffer : backwards(m_buffers)) {
+        if (!buffer || !buffer->isInUse()) {
+            // Buffer is okey to use, swap if necessary
+            if (buffer != m_buffers.back())
+                std::swap(buffer, m_buffers.back());
+            qCDebug(lcQpaBackingStore) << "Using back buffer" << m_buffers.back().get();
+
+            static const int kMaxSwapChainDepth = 3;
+            if (m_buffers.size() > kMaxSwapChainDepth) {
+                qCDebug(lcQpaBackingStore) << "Reducing swap chain depth to" << kMaxSwapChainDepth;
+                m_buffers.erase(std::next(m_buffers.begin(), 1), std::prev(m_buffers.end(), 2));
+            }
+
+            break;
+        } else if (buffer == m_buffers.front()) {
+            // We've exhausted the available buffers, make room for a new one
+            const int swapChainDepth = m_buffers.size() + 1;
+            qCDebug(lcQpaBackingStore) << "Available buffers exhausted, increasing swap chain depth to" << swapChainDepth;
+            m_buffers.resize(swapChainDepth);
+            break;
+        }
+    }
+
+    Q_ASSERT(!m_buffers.back() || !m_buffers.back()->isInUse());
+}
+
+// Disabled until performance issue on 5K iMac Pro has been investigated further,
+// as rounding up during resize will typically result in full screen buffer sizes
+// and low frame rate also for smaller window sizes.
+#define USE_LAZY_BUFFER_ALLOCATION_DURING_LIVE_WINDOW_RESIZE 0
+
+bool QCALayerBackingStore::recreateBackBufferIfNeeded()
+{
+    const qreal devicePixelRatio = window()->devicePixelRatio();
+    QSize requestedBufferSize = m_requestedSize * devicePixelRatio;
+
+    const NSView *backingStoreView = static_cast<QCocoaWindow *>(window()->handle())->view();
+    Q_UNUSED(backingStoreView);
+
+    auto bufferSizeMismatch = [&](const QSize requested, const QSize actual) {
+#if USE_LAZY_BUFFER_ALLOCATION_DURING_LIVE_WINDOW_RESIZE
+        if (backingStoreView.inLiveResize) {
+            // Prevent over-eager buffer allocation during window resize by reusing larger buffers
+            return requested.width() > actual.width() || requested.height() > actual.height();
+        }
+#endif
+        return requested != actual;
+    };
+
+    if (!m_buffers.back() || bufferSizeMismatch(requestedBufferSize, m_buffers.back()->size())) {
+#if USE_LAZY_BUFFER_ALLOCATION_DURING_LIVE_WINDOW_RESIZE
+        if (backingStoreView.inLiveResize) {
+            // Prevent over-eager buffer allocation during window resize by rounding up
+            QSize nativeScreenSize = window()->screen()->geometry().size() * devicePixelRatio;
+            requestedBufferSize = QSize(qNextPowerOfTwo(requestedBufferSize.width()),
+                qNextPowerOfTwo(requestedBufferSize.height())).boundedTo(nativeScreenSize);
+        }
+#endif
+
+        qCInfo(lcQpaBackingStore) << "Creating surface of" << requestedBufferSize
+            << "based on requested" << m_requestedSize << "and dpr =" << devicePixelRatio;
+
+        static auto pixelFormat = QImage::toPixelFormat(QImage::Format_ARGB32_Premultiplied);
+
+        NSView *view = static_cast<QCocoaWindow *>(window()->handle())->view();
+        auto colorSpace = QCFType<CGColorSpaceRef>::constructFromGet(view.window.screen.colorSpace.CGColorSpace);
+
+        m_buffers.back().reset(new GraphicsBuffer(requestedBufferSize, devicePixelRatio, pixelFormat, colorSpace));
+        return true;
+    }
+
+    return false;
+}
+
+QPaintDevice *QCALayerBackingStore::paintDevice()
+{
+    Q_ASSERT(m_buffers.back());
+    return m_buffers.back()->asImage();
+}
+
+void QCALayerBackingStore::endPaint()
+{
+    qCInfo(lcQpaBackingStore) << "Paint ended with painted region" << m_paintedRegion;
+    m_buffers.back()->unlock();
+}
+
+void QCALayerBackingStore::flush(QWindow *flushedWindow, const QRegion &region, const QPoint &offset)
+{
+    Q_UNUSED(region);
+    Q_UNUSED(offset);
+
+    if (!prepareForFlush())
+        return;
+
+    QMacAutoReleasePool pool;
+
+    NSView *backingStoreView = static_cast<QCocoaWindow *>(window()->handle())->view();
+    NSView *flushedView = static_cast<QCocoaWindow *>(flushedWindow->handle())->view();
+
+    id backBufferSurface = (__bridge id)m_buffers.back()->surface();
+    if (flushedView.layer.contents == backBufferSurface) {
+        // We've managed to paint to the back buffer again before Core Animation had time
+        // to flush the transaction and persist the layer changes to the window server.
+        // The layer already knows about the back buffer, and we don't need to re-apply
+        // it to pick up the surface changes, so bail out early.
+        qCInfo(lcQpaBackingStore).nospace() << "Skipping flush of " << flushedView
+            << ", layer already reflects back buffer";
+        return;
+    }
+
+    // Trigger a new display cycle if there isn't one. This ensures that our layer updates
+    // are committed as part of a display-cycle instead of on the next runloop pass. This
+    // means CA won't try to throttle us if we flush too fast, and we'll coalesce our flush
+    // with other pending view and layer updates.
+    backingStoreView.window.viewsNeedDisplay = YES;
+
+    if (window()->format().swapBehavior() == QSurfaceFormat::SingleBuffer) {
+        // The private API [CALayer reloadValueForKeyPath:@"contents"] would be preferable,
+        // but barring any side effects or performance issues we opt for the hammer for now.
+        flushedView.layer.contents = nil;
+    }
+
+    qCInfo(lcQpaBackingStore) << "Flushing" << backBufferSurface
+         << "to" << flushedView.layer << "of" << flushedView;
+
+    flushedView.layer.contents = backBufferSurface;
+
+    if (flushedView != backingStoreView) {
+        const CGSize backingStoreSize = backingStoreView.bounds.size;
+        flushedView.layer.contentsRect = CGRectApplyAffineTransform(
+            [flushedView convertRect:flushedView.bounds toView:backingStoreView],
+            // The contentsRect is in unit coordinate system
+            CGAffineTransformMakeScale(1.0 / backingStoreSize.width, 1.0 / backingStoreSize.height));
+    }
+
+    // Since we may receive multiple flushes before a new frame is started, we do not
+    // swap any buffers just yet. Instead we check in the next beginPaint if the layer's
+    // surface is in use, and if so swap to an unused surface as the new back buffer.
+
+    // Note: Ideally CoreAnimation would mark a surface as in use the moment we assign
+    // it to a layer, but as that's not the case we may end up painting to the same back
+    // buffer once more if we are painting faster than CA can ship the surfaces over to
+    // the window server.
+}
+
+void QCALayerBackingStore::composeAndFlush(QWindow *window, const QRegion &region, const QPoint &offset,
+                                    QPlatformTextureList *textures, bool translucentBackground)
+{
+    if (!prepareForFlush())
+        return;
+
+    QPlatformBackingStore::composeAndFlush(window, region, offset, textures, translucentBackground);
+}
+
+QPlatformGraphicsBuffer *QCALayerBackingStore::graphicsBuffer() const
+{
+    return m_buffers.back().get();
+}
+
+bool QCALayerBackingStore::prepareForFlush()
+{
+    if (!m_buffers.back()) {
+        qCWarning(lcQpaBackingStore) << "Tried to flush backingstore without painting to it first";
+        return false;
+    }
+
+    // Update dirty state of buffers based on what was painted. The back buffer will be
+    // less dirty, since we painted to it, while other buffers will become more dirty.
+    // This allows us to minimize copies between front and back buffers on swap in the
+    // cases where the painted region overlaps with the previous frame (front buffer).
+    for (const auto &buffer : m_buffers) {
+        if (buffer == m_buffers.back())
+            buffer->dirtyRegion -= m_paintedRegion;
+        else
+            buffer->dirtyRegion += m_paintedRegion;
+    }
+
+    // After painting, the back buffer is only guaranteed to have content for the painted
+    // region, and may still have dirty areas that need to be synced up with the front buffer,
+    // if we have one. We know that the front buffer is always up to date.
+    if (!m_buffers.back()->dirtyRegion.isEmpty() && m_buffers.front() != m_buffers.back()) {
+        QRegion preserveRegion = m_buffers.back()->dirtyRegion;
+        qCDebug(lcQpaBackingStore) << "Preserving" << preserveRegion << "from front to back buffer";
+
+        m_buffers.front()->lock(QPlatformGraphicsBuffer::SWReadAccess);
+        const QImage *frontBuffer = m_buffers.front()->asImage();
+
+        const QRect frontSurfaceBounds(QPoint(0, 0), m_buffers.front()->size());
+        const qreal sourceDevicePixelRatio = frontBuffer->devicePixelRatio();
+
+        m_buffers.back()->lock(QPlatformGraphicsBuffer::SWWriteAccess);
+        QPainter painter(m_buffers.back()->asImage());
+        painter.setCompositionMode(QPainter::CompositionMode_Source);
+
+        // Let painter operate in device pixels, to make it easier to compare coordinates
+        const qreal targetDevicePixelRatio = painter.device()->devicePixelRatio();
+        painter.scale(1.0 / targetDevicePixelRatio, 1.0 / targetDevicePixelRatio);
+
+        for (const QRect &rect : preserveRegion) {
+            QRect sourceRect(rect.topLeft() * sourceDevicePixelRatio, rect.size() * sourceDevicePixelRatio);
+            QRect targetRect(rect.topLeft() * targetDevicePixelRatio, rect.size() * targetDevicePixelRatio);
+
+#ifdef QT_DEBUG
+            if (Q_UNLIKELY(!frontSurfaceBounds.contains(sourceRect.bottomRight()))) {
+                qCWarning(lcQpaBackingStore) << "Front buffer too small to preserve"
+                    << QRegion(sourceRect).subtracted(frontSurfaceBounds);
+            }
+#endif
+            painter.drawImage(targetRect, *frontBuffer, sourceRect);
+        }
+
+        m_buffers.back()->unlock();
+        m_buffers.front()->unlock();
+
+        // The back buffer is now completely in sync, ready to be presented
+        m_buffers.back()->dirtyRegion = QRegion();
+    }
+
+    // Prepare for another round of painting
+    m_paintedRegion = QRegion();
+
+    return true;
+}
+
+// ----------------------------------------------------------------------------
+
+QCALayerBackingStore::GraphicsBuffer::GraphicsBuffer(const QSize &size, qreal devicePixelRatio,
+                                const QPixelFormat &format, QCFType<CGColorSpaceRef> colorSpace)
+    : QIOSurfaceGraphicsBuffer(size, format, colorSpace)
+    , dirtyRegion(0, 0, size.width() / devicePixelRatio, size.height() / devicePixelRatio)
+    , m_devicePixelRatio(devicePixelRatio)
+{
+}
+
+QImage *QCALayerBackingStore::GraphicsBuffer::asImage()
+{
+    if (m_image.isNull()) {
+        qCDebug(lcQpaBackingStore) << "Setting up paint device for" << this;
+        CFRetain(surface());
+        m_image = QImage(data(), size().width(), size().height(),
+            bytesPerLine(), QImage::toImageFormat(format()),
+            QImageCleanupFunction(CFRelease), surface());
+        m_image.setDevicePixelRatio(m_devicePixelRatio);
+    }
+
+    Q_ASSERT_X(m_image.constBits() == data(), "QCALayerBackingStore",
+        "IOSurfaces should have have a fixed location in memory once created");
+
+    return &m_image;
+}
+
 QT_END_NAMESPACE
diff --git a/src/plugins/platforms/cocoa/qcocoaintegration.mm b/src/plugins/platforms/cocoa/qcocoaintegration.mm
index affbee35b7..fb3d05d3e4 100644
--- a/src/plugins/platforms/cocoa/qcocoaintegration.mm
+++ b/src/plugins/platforms/cocoa/qcocoaintegration.mm
@@ -244,7 +244,7 @@ QCocoaIntegration::~QCocoaIntegration()
 
     // Delete screens in reverse order to avoid crash in case of multiple screens
     while (!mScreens.isEmpty()) {
-        destroyScreen(mScreens.takeLast());
+        QWindowSystemInterface::handleScreenRemoved(mScreens.takeLast());
     }
 
     clearToolbars();
@@ -304,7 +304,7 @@ void QCocoaIntegration::updateScreens()
             screen = new QCocoaScreen(i);
             mScreens.append(screen);
             qCDebug(lcQpaScreen) << "Adding" << screen;
-            screenAdded(screen);
+            QWindowSystemInterface::handleScreenAdded(screen);
         }
         siblings << screen;
     }
@@ -321,7 +321,7 @@ void QCocoaIntegration::updateScreens()
         // Prevent stale references to NSScreen during destroy
         screen->m_screenIndex = -1;
         qCDebug(lcQpaScreen) << "Removing" << screen;
-        destroyScreen(screen);
+        QWindowSystemInterface::handleScreenRemoved(screen);
     }
 }
 
@@ -407,7 +407,16 @@ QPlatformOpenGLContext *QCocoaIntegration::createPlatformOpenGLContext(QOpenGLCo
 
 QPlatformBackingStore *QCocoaIntegration::createPlatformBackingStore(QWindow *window) const
 {
-    return new QCocoaBackingStore(window);
+    QCocoaWindow *platformWindow = static_cast<QCocoaWindow*>(window->handle());
+    if (!platformWindow) {
+        qWarning() << window << "must be created before being used with a backingstore";
+        return nullptr;
+    }
+
+    if (platformWindow->view().layer)
+        return new QCALayerBackingStore(window);
+    else
+        return new QNSWindowBackingStore(window);
 }
 
 QAbstractEventDispatcher *QCocoaIntegration::createEventDispatcher() const
diff --git a/src/plugins/platforms/cocoa/qiosurfacegraphicsbuffer.h b/src/plugins/platforms/cocoa/qiosurfacegraphicsbuffer.h
new file mode 100644
index 0000000000..872773cb7a
--- /dev/null
+++ b/src/plugins/platforms/cocoa/qiosurfacegraphicsbuffer.h
@@ -0,0 +1,77 @@
+/****************************************************************************
+**
+** Copyright (C) 2019 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the plugins of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QIOSURFACEGRAPHICSBUFFER_H
+#define QIOSURFACEGRAPHICSBUFFER_H
+
+#include <qpa/qplatformgraphicsbuffer.h>
+#include <private/qcore_mac_p.h>
+
+QT_BEGIN_NAMESPACE
+
+class QIOSurfaceGraphicsBuffer : public QPlatformGraphicsBuffer
+{
+public:
+    QIOSurfaceGraphicsBuffer(const QSize &size, const QPixelFormat &format, QCFType<CGColorSpaceRef> colorSpace);
+    ~QIOSurfaceGraphicsBuffer();
+
+    const uchar *data() const override;
+    uchar *data() override;
+    int bytesPerLine() const override;
+
+    IOSurfaceRef surface();
+    bool isInUse() const;
+
+protected:
+    bool doLock(AccessTypes access, const QRect &rect) override;
+    void doUnlock() override;
+
+private:
+    QCFType<IOSurfaceRef> m_surface;
+
+    friend QDebug operator<<(QDebug, const QIOSurfaceGraphicsBuffer *);
+};
+
+#ifndef QT_NO_DEBUG_STREAM
+QDebug operator<<(QDebug, const QIOSurfaceGraphicsBuffer *);
+#endif
+
+QT_END_NAMESPACE
+
+#endif // QIOSURFACEGRAPHICSBUFFER_H
diff --git a/src/plugins/platforms/cocoa/qiosurfacegraphicsbuffer.mm b/src/plugins/platforms/cocoa/qiosurfacegraphicsbuffer.mm
new file mode 100644
index 0000000000..a367487e85
--- /dev/null
+++ b/src/plugins/platforms/cocoa/qiosurfacegraphicsbuffer.mm
@@ -0,0 +1,188 @@
+/****************************************************************************
+**
+** Copyright (C) 2019 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the plugins of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "qiosurfacegraphicsbuffer.h"
+
+#include <QtCore/qdebug.h>
+#include <QtCore/qloggingcategory.h>
+
+#include <CoreGraphics/CoreGraphics.h>
+#include <IOSurface/IOSurface.h>
+
+// CGColorSpaceCopyPropertyList is available on 10.12 and above,
+// but was only added in the 10.14 SDK, so declare it just in case.
+extern "C" CFPropertyListRef CGColorSpaceCopyPropertyList(CGColorSpaceRef space);
+
+QT_BEGIN_NAMESPACE
+
+Q_LOGGING_CATEGORY(lcQpaIOSurface, "qt.qpa.backingstore.iosurface");
+
+QIOSurfaceGraphicsBuffer::QIOSurfaceGraphicsBuffer(const QSize &size, const QPixelFormat &format, QCFType<CGColorSpaceRef> colorSpace)
+    : QPlatformGraphicsBuffer(size, format)
+{
+    const size_t width = size.width();
+    const size_t height = size.height();
+
+    Q_ASSERT(width <= IOSurfaceGetPropertyMaximum(kIOSurfaceWidth));
+    Q_ASSERT(height <= IOSurfaceGetPropertyMaximum(kIOSurfaceHeight));
+
+    static const char bytesPerElement = 4;
+
+    const size_t bytesPerRow = IOSurfaceAlignProperty(kIOSurfaceBytesPerRow, width * bytesPerElement);
+    const size_t totalBytes = IOSurfaceAlignProperty(kIOSurfaceAllocSize, height * bytesPerRow);
+
+    NSDictionary *options = @{
+        (id)kIOSurfaceWidth: @(width),
+        (id)kIOSurfaceHeight: @(height),
+        (id)kIOSurfacePixelFormat: @(unsigned('BGRA')),
+        (id)kIOSurfaceBytesPerElement: @(bytesPerElement),
+        (id)kIOSurfaceBytesPerRow: @(bytesPerRow),
+        (id)kIOSurfaceAllocSize: @(totalBytes),
+    };
+
+    m_surface = IOSurfaceCreate((CFDictionaryRef)options);
+    Q_ASSERT(m_surface);
+
+    Q_ASSERT(size_t(bytesPerLine()) == bytesPerRow);
+    Q_ASSERT(size_t(byteCount()) == totalBytes);
+
+    if (colorSpace) {
+        IOSurfaceSetValue(m_surface, CFSTR("IOSurfaceColorSpace"),
+            QCFType<CFPropertyListRef>(CGColorSpaceCopyPropertyList(colorSpace)));
+    }
+}
+
+QIOSurfaceGraphicsBuffer::~QIOSurfaceGraphicsBuffer()
+{
+}
+
+const uchar *QIOSurfaceGraphicsBuffer::data() const
+{
+    return (const uchar *)IOSurfaceGetBaseAddress(m_surface);
+}
+
+uchar *QIOSurfaceGraphicsBuffer::data()
+{
+    return (uchar *)IOSurfaceGetBaseAddress(m_surface);
+}
+
+int QIOSurfaceGraphicsBuffer::bytesPerLine() const
+{
+    return IOSurfaceGetBytesPerRow(m_surface);
+}
+
+IOSurfaceRef QIOSurfaceGraphicsBuffer::surface()
+{
+    return m_surface;
+}
+
+bool QIOSurfaceGraphicsBuffer::isInUse() const
+{
+    return IOSurfaceIsInUse(m_surface);
+}
+
+IOSurfaceLockOptions lockOptionsForAccess(QPlatformGraphicsBuffer::AccessTypes access)
+{
+    IOSurfaceLockOptions lockOptions = 0;
+    if (!(access & QPlatformGraphicsBuffer::SWWriteAccess))
+        lockOptions |= kIOSurfaceLockReadOnly;
+    return lockOptions;
+}
+
+bool QIOSurfaceGraphicsBuffer::doLock(AccessTypes access, const QRect &rect)
+{
+    Q_UNUSED(rect);
+    Q_ASSERT(!isLocked());
+
+    qCDebug(lcQpaIOSurface) << "Locking" << this << "for" << access;
+
+    // FIXME: Teach QPlatformBackingStore::composeAndFlush about non-2D texture
+    // targets, so that we can use CGLTexImageIOSurface2D to support TextureAccess.
+    if (access & (TextureAccess | HWCompositor))
+        return false;
+
+    auto lockOptions = lockOptionsForAccess(access);
+
+    // Try without read-back first
+    lockOptions |= kIOSurfaceLockAvoidSync;
+    kern_return_t ret = IOSurfaceLock(m_surface, lockOptions, nullptr);
+    if (ret == kIOSurfaceSuccess)
+        return true;
+
+    if (ret == kIOReturnCannotLock) {
+        qCWarning(lcQpaIOSurface) << "Locking of" << this << "requires read-back";
+        lockOptions ^= kIOSurfaceLockAvoidSync;
+        ret = IOSurfaceLock(m_surface, lockOptions, nullptr);
+    }
+
+    if (ret != kIOSurfaceSuccess) {
+        qCWarning(lcQpaIOSurface) << "Failed to lock" << this << ret;
+        return false;
+    }
+
+    return true;
+}
+
+void QIOSurfaceGraphicsBuffer::doUnlock()
+{
+    qCDebug(lcQpaIOSurface) << "Unlocking" << this << "from" << isLocked();
+
+    auto lockOptions = lockOptionsForAccess(isLocked());
+    bool success = IOSurfaceUnlock(m_surface, lockOptions, nullptr) == kIOSurfaceSuccess;
+    Q_ASSERT_X(success, "QIOSurfaceGraphicsBuffer", "Unlocking surface should succeed");
+}
+
+#ifndef QT_NO_DEBUG_STREAM
+QDebug operator<<(QDebug debug, const QIOSurfaceGraphicsBuffer *graphicsBuffer)
+{
+    QDebugStateSaver saver(debug);
+    debug.nospace();
+    debug << "QIOSurfaceGraphicsBuffer(" << (const void *)graphicsBuffer;
+    if (graphicsBuffer) {
+        debug << ", surface=" << graphicsBuffer->m_surface;
+        debug << ", size=" << graphicsBuffer->size();
+        debug << ", isLocked=" << bool(graphicsBuffer->isLocked());
+        debug << ", isInUse=" << graphicsBuffer->isInUse();
+    }
+    debug << ')';
+    return debug;
+}
+#endif // !QT_NO_DEBUG_STREAM
+
+QT_END_NAMESPACE
diff --git a/src/plugins/platforms/cocoa/qnsview_drawing.mm b/src/plugins/platforms/cocoa/qnsview_drawing.mm
index 6db5ed8bad..f7e14b7883 100644
--- a/src/plugins/platforms/cocoa/qnsview_drawing.mm
+++ b/src/plugins/platforms/cocoa/qnsview_drawing.mm
@@ -163,6 +163,13 @@
     return NSViewLayerContentsRedrawDuringViewResize;
 }
 
+- (NSViewLayerContentsPlacement)layerContentsPlacement
+{
+    // Always place the layer at top left without any automatic scaling,
+    // so that we can re-use larger layers when resizing a window down.
+    return NSViewLayerContentsPlacementTopLeft;
+}
+
 - (void)updateMetalLayerDrawableSize:(CAMetalLayer *)layer
 {
     CGSize drawableSize = layer.bounds.size;
diff --git a/src/plugins/platforms/directfb/qdirectfb_egl.cpp b/src/plugins/platforms/directfb/qdirectfb_egl.cpp
index dad553c890..d3c95f0b65 100644
--- a/src/plugins/platforms/directfb/qdirectfb_egl.cpp
+++ b/src/plugins/platforms/directfb/qdirectfb_egl.cpp
@@ -44,6 +44,7 @@
 
 #include <QtGui/QOpenGLContext>
 #include <qpa/qplatformopenglcontext.h>
+#include <qpa/qwindowsysteminterface.h>
 #include <QtGui/QScreen>
 
 #include <QtEglSupport/private/qeglplatformcontext_p.h>
@@ -248,7 +249,7 @@ QPlatformOpenGLContext *QDirectFbIntegrationEGL::createPlatformOpenGLContext(QOp
 void QDirectFbIntegrationEGL::initializeScreen()
 {
     m_primaryScreen.reset(new QDirectFbScreenEGL(0));
-    screenAdded(m_primaryScreen.data());
+    QWindowSystemInterface::handleScreenAdded(m_primaryScreen.data());
 }
 
 bool QDirectFbIntegrationEGL::hasCapability(QPlatformIntegration::Capability cap) const
diff --git a/src/plugins/platforms/directfb/qdirectfbintegration.cpp b/src/plugins/platforms/directfb/qdirectfbintegration.cpp
index cdf340da7a..73e308da53 100644
--- a/src/plugins/platforms/directfb/qdirectfbintegration.cpp
+++ b/src/plugins/platforms/directfb/qdirectfbintegration.cpp
@@ -56,6 +56,7 @@
 #include <QtCore/QThread>
 #include <QtCore/QAbstractEventDispatcher>
 #include <qpa/qplatforminputcontextfactory_p.h>
+#include <qpa/qwindowsysteminterface.h>
 
 QT_BEGIN_NAMESPACE
 
@@ -113,7 +114,7 @@ void QDirectFbIntegration::initializeDirectFB()
 void QDirectFbIntegration::initializeScreen()
 {
     m_primaryScreen.reset(new QDirectFbScreen(0));
-    screenAdded(m_primaryScreen.data());
+    QWindowSystemInterface::handleScreenAdded(m_primaryScreen.data());
 }
 
 void QDirectFbIntegration::initializeInput()
diff --git a/src/plugins/platforms/eglfs/api/qeglfsdeviceintegration.cpp b/src/plugins/platforms/eglfs/api/qeglfsdeviceintegration.cpp
index 0a3a37863a..81bad45cd2 100644
--- a/src/plugins/platforms/eglfs/api/qeglfsdeviceintegration.cpp
+++ b/src/plugins/platforms/eglfs/api/qeglfsdeviceintegration.cpp
@@ -200,10 +200,8 @@ void QEglFSDeviceIntegration::screenInit()
 void QEglFSDeviceIntegration::screenDestroy()
 {
     QGuiApplication *app = qGuiApp;
-    QEglFSIntegration *platformIntegration = static_cast<QEglFSIntegration *>(
-        QGuiApplicationPrivate::platformIntegration());
     while (!app->screens().isEmpty())
-        platformIntegration->removeScreen(app->screens().constLast()->handle());
+        QWindowSystemInterface::handleScreenRemoved(app->screens().constLast()->handle());
 }
 
 QSizeF QEglFSDeviceIntegration::physicalScreenSize() const
diff --git a/src/plugins/platforms/eglfs/api/qeglfsintegration.cpp b/src/plugins/platforms/eglfs/api/qeglfsintegration.cpp
index 8ccb0ef2cd..48469b0f8c 100644
--- a/src/plugins/platforms/eglfs/api/qeglfsintegration.cpp
+++ b/src/plugins/platforms/eglfs/api/qeglfsintegration.cpp
@@ -120,16 +120,6 @@ QEglFSIntegration::QEglFSIntegration()
     initResources();
 }
 
-void QEglFSIntegration::addScreen(QPlatformScreen *screen, bool isPrimary)
-{
-    screenAdded(screen, isPrimary);
-}
-
-void QEglFSIntegration::removeScreen(QPlatformScreen *screen)
-{
-    destroyScreen(screen);
-}
-
 void QEglFSIntegration::initialize()
 {
     qt_egl_device_integration()->platformInit();
@@ -147,7 +137,7 @@ void QEglFSIntegration::initialize()
     m_vtHandler.reset(new QFbVtHandler);
 
     if (qt_egl_device_integration()->usesDefaultScreen())
-        addScreen(new QEglFSScreen(display()));
+        QWindowSystemInterface::handleScreenAdded(new QEglFSScreen(display()));
     else
         qt_egl_device_integration()->screenInit();
 
diff --git a/src/plugins/platforms/eglfs/api/qeglfsintegration_p.h b/src/plugins/platforms/eglfs/api/qeglfsintegration_p.h
index 4b4585d33c..898b322834 100644
--- a/src/plugins/platforms/eglfs/api/qeglfsintegration_p.h
+++ b/src/plugins/platforms/eglfs/api/qeglfsintegration_p.h
@@ -103,9 +103,6 @@ public:
 
     QFbVtHandler *vtHandler() { return m_vtHandler.data(); }
 
-    void addScreen(QPlatformScreen *screen, bool isPrimary = false);
-    void removeScreen(QPlatformScreen *screen);
-
 private:
     EGLNativeDisplayType nativeDisplay() const;
     void createInputHandlers();
diff --git a/src/plugins/platforms/eglfs/deviceintegration/eglfs_emu/qeglfsemulatorintegration.cpp b/src/plugins/platforms/eglfs/deviceintegration/eglfs_emu/qeglfsemulatorintegration.cpp
index 5e2708e958..cb7844aff0 100644
--- a/src/plugins/platforms/eglfs/deviceintegration/eglfs_emu/qeglfsemulatorintegration.cpp
+++ b/src/plugins/platforms/eglfs/deviceintegration/eglfs_emu/qeglfsemulatorintegration.cpp
@@ -45,6 +45,8 @@
 #include <QtEglSupport/private/qeglconvenience_p.h>
 #include <QtEglSupport/private/qeglplatformcontext_p.h>
 
+#include <qpa/qwindowsysteminterface.h>
+
 #include <QtCore/QJsonDocument>
 #include <QtCore/QJsonArray>
 #include <QtCore/QJsonParseError>
@@ -80,8 +82,6 @@ bool QEglFSEmulatorIntegration::usesDefaultScreen()
 
 void QEglFSEmulatorIntegration::screenInit()
 {
-    QEglFSIntegration *integration = static_cast<QEglFSIntegration *>(QGuiApplicationPrivate::platformIntegration());
-
     // Use qgsGetDisplays() call to retrieve the available screens from the Emulator
     if (getDisplays) {
         QByteArray displaysInfo = getDisplays();
@@ -93,7 +93,7 @@ void QEglFSEmulatorIntegration::screenInit()
                 QJsonArray screenArray = displaysDocument.array();
                 for (auto screenValue : screenArray) {
                     if (screenValue.isObject())
-                        integration->addScreen(new QEglFSEmulatorScreen(screenValue.toObject()));
+                        QWindowSystemInterface::handleScreenAdded(new QEglFSEmulatorScreen(screenValue.toObject()));
                 }
             }
         } else {
diff --git a/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms_egldevice/qeglfskmsegldeviceintegration.cpp b/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms_egldevice/qeglfskmsegldeviceintegration.cpp
index 9f4c9f5703..ef732f9832 100644
--- a/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms_egldevice/qeglfskmsegldeviceintegration.cpp
+++ b/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms_egldevice/qeglfskmsegldeviceintegration.cpp
@@ -310,7 +310,7 @@ QKmsDevice *QEglFSKmsEglDeviceIntegration::createDevice()
     if (Q_UNLIKELY(!deviceName))
         qFatal("Failed to query device name from EGLDevice");
 
-    return new QEglFSKmsEglDevice(this, screenConfig(), deviceName);
+    return new QEglFSKmsEglDevice(this, screenConfig(), QLatin1String(deviceName));
 }
 
 bool QEglFSKmsEglDeviceIntegration::query_egl_device()
diff --git a/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms_support/qeglfskmsdevice.cpp b/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms_support/qeglfskmsdevice.cpp
index b073577797..4f0b0d7725 100644
--- a/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms_support/qeglfskmsdevice.cpp
+++ b/src/plugins/platforms/eglfs/deviceintegration/eglfs_kms_support/qeglfskmsdevice.cpp
@@ -58,7 +58,7 @@ void QEglFSKmsDevice::registerScreen(QPlatformScreen *screen,
     QEglFSKmsScreen *s = static_cast<QEglFSKmsScreen *>(screen);
     s->setVirtualPosition(virtualPos);
     s->setVirtualSiblings(virtualSiblings);
-    static_cast<QEglFSIntegration *>(QGuiApplicationPrivate::platformIntegration())->addScreen(s, isPrimary);
+    QWindowSystemInterface::handleScreenAdded(s, isPrimary);
 }
 
 QT_END_NAMESPACE
diff --git a/src/plugins/platforms/haiku/qhaikuintegration.cpp b/src/plugins/platforms/haiku/qhaikuintegration.cpp
index 8bd2171794..44df6ae8f5 100644
--- a/src/plugins/platforms/haiku/qhaikuintegration.cpp
+++ b/src/plugins/platforms/haiku/qhaikuintegration.cpp
@@ -49,6 +49,7 @@
 #include <QCoreApplication>
 #include <QFileInfo>
 #include <qpa/qplatformwindow.h>
+#include <qpa/qwindowsysteminterface.h>
 #include <QtEventDispatcherSupport/private/qgenericunixeventdispatcher_p.h>
 
 #include <Application.h>
@@ -81,12 +82,12 @@ QHaikuIntegration::QHaikuIntegration(const QStringList &parameters)
     m_services = new QHaikuServices;
 
     // notify system about available screen
-    screenAdded(m_screen);
+    QWindowSystemInterface::handleScreenAdded(m_screen);
 }
 
 QHaikuIntegration::~QHaikuIntegration()
 {
-    destroyScreen(m_screen);
+    QWindowSystemInterface::handleScreenRemoved(m_screen);
     m_screen = nullptr;
 
     delete m_services;
diff --git a/src/plugins/platforms/integrity/qintegrityfbintegration.cpp b/src/plugins/platforms/integrity/qintegrityfbintegration.cpp
index ae802bb1fa..3ad31dc562 100644
--- a/src/plugins/platforms/integrity/qintegrityfbintegration.cpp
+++ b/src/plugins/platforms/integrity/qintegrityfbintegration.cpp
@@ -51,7 +51,7 @@
 
 #include <QtGui/private/qguiapplication_p.h>
 #include <qpa/qplatforminputcontextfactory_p.h>
-
+#include <qpa/qwindowsysteminterface.h>
 
 QT_BEGIN_NAMESPACE
 
@@ -64,13 +64,13 @@ QIntegrityFbIntegration::QIntegrityFbIntegration(const QStringList &paramList)
 
 QIntegrityFbIntegration::~QIntegrityFbIntegration()
 {
-    destroyScreen(m_primaryScreen);
+    QWindowSystemInterface::handleScreenRemoved(m_primaryScreen);
 }
 
 void QIntegrityFbIntegration::initialize()
 {
     if (m_primaryScreen->initialize())
-        screenAdded(m_primaryScreen);
+        QWindowSystemInterface::handleScreenAdded(m_primaryScreen);
     else
         qWarning("integrityfb: Failed to initialize screen");
 
diff --git a/src/plugins/platforms/ios/qiosintegration.h b/src/plugins/platforms/ios/qiosintegration.h
index 818250fcee..eeb44b54d3 100644
--- a/src/plugins/platforms/ios/qiosintegration.h
+++ b/src/plugins/platforms/ios/qiosintegration.h
@@ -92,10 +92,6 @@ public:
     QPlatformAccessibility *accessibility() const override;
 #endif
 
-    // Called from Objective-C class QIOSScreenTracker, which can't be friended
-    void addScreen(QPlatformScreen *screen) { screenAdded(screen); }
-    void destroyScreen(QPlatformScreen *screen) { QPlatformIntegration::destroyScreen(screen); }
-
     void beep() const override;
 
     static QIOSIntegration *instance();
diff --git a/src/plugins/platforms/ios/qiosintegration.mm b/src/plugins/platforms/ios/qiosintegration.mm
index bec8354fcc..9eca0eaad3 100644
--- a/src/plugins/platforms/ios/qiosintegration.mm
+++ b/src/plugins/platforms/ios/qiosintegration.mm
@@ -107,7 +107,7 @@ void QIOSIntegration::initialize()
     }
 
     for (UIScreen *screen in screens)
-        addScreen(new QIOSScreen(screen));
+        QWindowSystemInterface::handleScreenAdded(new QIOSScreen(screen));
 
     // Depends on a primary screen being present
     m_inputContext = new QIOSInputContext;
@@ -143,7 +143,7 @@ QIOSIntegration::~QIOSIntegration()
     m_inputContext = 0;
 
     foreach (QScreen *screen, QGuiApplication::screens())
-        destroyScreen(screen->handle());
+        QWindowSystemInterface::handleScreenRemoved(screen->handle());
 
     delete m_platformServices;
     m_platformServices = 0;
diff --git a/src/plugins/platforms/ios/qiosscreen.mm b/src/plugins/platforms/ios/qiosscreen.mm
index 4f753be21a..9aba658479 100644
--- a/src/plugins/platforms/ios/qiosscreen.mm
+++ b/src/plugins/platforms/ios/qiosscreen.mm
@@ -50,6 +50,7 @@
 
 #include <QtGui/private/qwindow_p.h>
 #include <private/qcoregraphics_p.h>
+#include <qpa/qwindowsysteminterface.h>
 
 #include <sys/sysctl.h>
 
@@ -105,10 +106,10 @@ static QIOSScreen* qtPlatformScreenFor(UIScreen *uiScreen)
 
 + (void)screenConnected:(NSNotification*)notification
 {
-    QIOSIntegration *integration = QIOSIntegration::instance();
-    Q_ASSERT_X(integration, Q_FUNC_INFO, "Screen connected before QIOSIntegration creation");
+    Q_ASSERT_X(QIOSIntegration::instance(), Q_FUNC_INFO,
+        "Screen connected before QIOSIntegration creation");
 
-    integration->addScreen(new QIOSScreen([notification object]));
+    QWindowSystemInterface::handleScreenAdded(new QIOSScreen([notification object]));
 }
 
 + (void)screenDisconnected:(NSNotification*)notification
@@ -116,8 +117,7 @@ static QIOSScreen* qtPlatformScreenFor(UIScreen *uiScreen)
     QIOSScreen *screen = qtPlatformScreenFor([notification object]);
     Q_ASSERT_X(screen, Q_FUNC_INFO, "Screen disconnected that we didn't know about");
 
-    QIOSIntegration *integration = QIOSIntegration::instance();
-    integration->destroyScreen(screen);
+    QWindowSystemInterface::handleScreenRemoved(screen);
 }
 
 + (void)screenModeChanged:(NSNotification*)notification
diff --git a/src/plugins/platforms/linuxfb/qlinuxfbintegration.cpp b/src/plugins/platforms/linuxfb/qlinuxfbintegration.cpp
index 9e38900bcd..68843aa4c5 100644
--- a/src/plugins/platforms/linuxfb/qlinuxfbintegration.cpp
+++ b/src/plugins/platforms/linuxfb/qlinuxfbintegration.cpp
@@ -54,6 +54,7 @@
 
 #include <QtGui/private/qguiapplication_p.h>
 #include <qpa/qplatforminputcontextfactory_p.h>
+#include <qpa/qwindowsysteminterface.h>
 
 #if QT_CONFIG(libinput)
 #include <QtInputSupport/private/qlibinputhandler_p.h>
@@ -89,13 +90,13 @@ QLinuxFbIntegration::QLinuxFbIntegration(const QStringList &paramList)
 
 QLinuxFbIntegration::~QLinuxFbIntegration()
 {
-    destroyScreen(m_primaryScreen);
+    QWindowSystemInterface::handleScreenRemoved(m_primaryScreen);
 }
 
 void QLinuxFbIntegration::initialize()
 {
     if (m_primaryScreen->initialize())
-        screenAdded(m_primaryScreen);
+        QWindowSystemInterface::handleScreenAdded(m_primaryScreen);
     else
         qWarning("linuxfb: Failed to initialize screen");
 
diff --git a/src/plugins/platforms/minimal/qminimalintegration.cpp b/src/plugins/platforms/minimal/qminimalintegration.cpp
index 0c04608fca..f457f69f11 100644
--- a/src/plugins/platforms/minimal/qminimalintegration.cpp
+++ b/src/plugins/platforms/minimal/qminimalintegration.cpp
@@ -43,6 +43,7 @@
 #include <QtGui/private/qpixmap_raster_p.h>
 #include <QtGui/private/qguiapplication_p.h>
 #include <qpa/qplatformwindow.h>
+#include <qpa/qwindowsysteminterface.h>
 
 #include <QtFontDatabaseSupport/private/qfreetypefontdatabase_p.h>
 #if defined(Q_OS_WINRT)
@@ -108,7 +109,7 @@ QMinimalIntegration::QMinimalIntegration(const QStringList &parameters)
     mPrimaryScreen->mDepth = 32;
     mPrimaryScreen->mFormat = QImage::Format_ARGB32_Premultiplied;
 
-    screenAdded(mPrimaryScreen);
+    QWindowSystemInterface::handleScreenAdded(mPrimaryScreen);
 }
 
 QMinimalIntegration::~QMinimalIntegration()
diff --git a/src/plugins/platforms/minimalegl/qminimaleglintegration.cpp b/src/plugins/platforms/minimalegl/qminimaleglintegration.cpp
index da58441d67..a0d35a80cd 100644
--- a/src/plugins/platforms/minimalegl/qminimaleglintegration.cpp
+++ b/src/plugins/platforms/minimalegl/qminimaleglintegration.cpp
@@ -58,6 +58,7 @@
 #include <QtGui/QSurfaceFormat>
 #include <QtGui/QOpenGLContext>
 #include <QtGui/QScreen>
+#include <qpa/qwindowsysteminterface.h>
 
 // this is where EGL headers are pulled in, make sure it is last
 #include "qminimaleglscreen.h"
@@ -90,7 +91,7 @@ protected:
 QMinimalEglIntegration::QMinimalEglIntegration()
     : mFontDb(new QGenericUnixFontDatabase()), mScreen(new QMinimalEglScreen(EGL_DEFAULT_DISPLAY))
 {
-    screenAdded(mScreen);
+    QWindowSystemInterface::handleScreenAdded(mScreen);
 
 #ifdef QEGL_EXTRA_DEBUG
     qWarning("QMinimalEglIntegration\n");
@@ -99,7 +100,7 @@ QMinimalEglIntegration::QMinimalEglIntegration()
 
 QMinimalEglIntegration::~QMinimalEglIntegration()
 {
-    destroyScreen(mScreen);
+    QWindowSystemInterface::handleScreenRemoved(mScreen);
     delete mFontDb;
 }
 
diff --git a/src/plugins/platforms/offscreen/qoffscreenintegration.cpp b/src/plugins/platforms/offscreen/qoffscreenintegration.cpp
index f2933b7179..869e9228cd 100644
--- a/src/plugins/platforms/offscreen/qoffscreenintegration.cpp
+++ b/src/plugins/platforms/offscreen/qoffscreenintegration.cpp
@@ -63,6 +63,7 @@
 #include <qpa/qplatforminputcontextfactory_p.h>
 #include <qpa/qplatforminputcontext.h>
 #include <qpa/qplatformtheme.h>
+#include <qpa/qwindowsysteminterface.h>
 
 #include <qpa/qplatformservices.h>
 
@@ -121,7 +122,7 @@ QOffscreenIntegration::QOffscreenIntegration()
 #endif
     m_services.reset(new QPlatformServices);
 
-    screenAdded(new QOffscreenScreen);
+    QWindowSystemInterface::handleScreenAdded(new QOffscreenScreen);
 }
 
 QOffscreenIntegration::~QOffscreenIntegration()
diff --git a/src/plugins/platforms/openwfd/qopenwfdintegration.cpp b/src/plugins/platforms/openwfd/qopenwfdintegration.cpp
index 4850ca2e45..c5dc40a206 100644
--- a/src/plugins/platforms/openwfd/qopenwfdintegration.cpp
+++ b/src/plugins/platforms/openwfd/qopenwfdintegration.cpp
@@ -50,6 +50,7 @@
 #include <QtGui/private/qguiapplication_p.h>
 #include <QtGui/QOpenGLContext>
 #include <QtGui/QScreen>
+#include <qpa/qwindowsysteminterface.h>
 
 #include <QtEventDispatcherSupport/private/qgenericunixeventdispatcher_p.h>
 #include <QtFontDatabaseSupport/private/qgenericunixfontdatabase_p.h>
@@ -135,13 +136,3 @@ QPlatformPrinterSupport * QOpenWFDIntegration::printerSupport() const
 {
     return mPrinterSupport;
 }
-
-void QOpenWFDIntegration::addScreen(QOpenWFDScreen *screen)
-{
-    screenAdded(screen);
-}
-
-void QOpenWFDIntegration::destroyScreen(QOpenWFDScreen *screen)
-{
-    QPlatformIntegration::destroyScreen(screen);
-}
diff --git a/src/plugins/platforms/openwfd/qopenwfdintegration.h b/src/plugins/platforms/openwfd/qopenwfdintegration.h
index 1ce1001bed..444aaccaaf 100644
--- a/src/plugins/platforms/openwfd/qopenwfdintegration.h
+++ b/src/plugins/platforms/openwfd/qopenwfdintegration.h
@@ -68,8 +68,6 @@ public:
 
     QPlatformPrinterSupport *printerSupport() const;
 
-    void addScreen(QOpenWFDScreen *screen);
-    void destroyScreen(QOpenWFDScreen *screen);
 private:
     QList<QPlatformScreen *> mScreens;
     QList<QOpenWFDDevice *>mDevices;
diff --git a/src/plugins/platforms/openwfd/qopenwfdport.cpp b/src/plugins/platforms/openwfd/qopenwfdport.cpp
index 33254fe83c..34b4439958 100644
--- a/src/plugins/platforms/openwfd/qopenwfdport.cpp
+++ b/src/plugins/platforms/openwfd/qopenwfdport.cpp
@@ -133,7 +133,7 @@ void QOpenWFDPort::attach()
     wfdBindPipelineToPort(mDevice->handle(),mPort,mPipeline);
 
     mScreen = new QOpenWFDScreen(this);
-    mDevice->integration()->addScreen(mScreen);
+    QWindowSystemInterface::handleScreenAdded(mScreen);
     mAttached = true;
 }
 
@@ -145,7 +145,7 @@ void QOpenWFDPort::detach()
     mAttached = false;
     mOn = false;
 
-    mDevice->integration()->destroyScreen(mScreen);
+    QWindowSystemInterface::handleScreenRemoved(mScreen);
 
     wfdDestroyPipeline(mDevice->handle(),mPipeline);
     mPipelineId = WFD_INVALID_PIPELINE_ID;
diff --git a/src/plugins/platforms/qnx/qqnxintegration.cpp b/src/plugins/platforms/qnx/qqnxintegration.cpp
index a996e765c4..a45dcabeb7 100644
--- a/src/plugins/platforms/qnx/qqnxintegration.cpp
+++ b/src/plugins/platforms/qnx/qqnxintegration.cpp
@@ -649,7 +649,7 @@ void QQnxIntegration::createDisplay(screen_display_t display, bool isPrimary)
 {
     QQnxScreen *screen = new QQnxScreen(m_screenContext, display, isPrimary);
     m_screens.append(screen);
-    screenAdded(screen);
+    QWindowSystemInterface::handleScreenAdded(screen);
     screen->adjustOrientation();
 
     QObject::connect(m_screenEventHandler, SIGNAL(newWindowCreated(void*)),
@@ -669,14 +669,14 @@ void QQnxIntegration::removeDisplay(QQnxScreen *screen)
     Q_CHECK_PTR(screen);
     Q_ASSERT(m_screens.contains(screen));
     m_screens.removeAll(screen);
-    destroyScreen(screen);
+    QWindowSystemInterface::handleScreenRemoved(screen);
 }
 
 void QQnxIntegration::destroyDisplays()
 {
     qIntegrationDebug();
     Q_FOREACH (QQnxScreen *screen, m_screens) {
-        QPlatformIntegration::destroyScreen(screen);
+        QWindowSystemInterface::handleScreenRemoved(screen);
     }
     m_screens.clear();
 }
diff --git a/src/plugins/platforms/vnc/qvncintegration.cpp b/src/plugins/platforms/vnc/qvncintegration.cpp
index 1e2cf6292c..c7a796464a 100644
--- a/src/plugins/platforms/vnc/qvncintegration.cpp
+++ b/src/plugins/platforms/vnc/qvncintegration.cpp
@@ -52,6 +52,7 @@
 #include <QtGui/private/qguiapplication_p.h>
 #include <qpa/qplatforminputcontextfactory_p.h>
 #include <private/qinputdevicemanager_p_p.h>
+#include <qpa/qwindowsysteminterface.h>
 
 #include <QtCore/QRegularExpression>
 
@@ -77,13 +78,13 @@ QVncIntegration::QVncIntegration(const QStringList &paramList)
 QVncIntegration::~QVncIntegration()
 {
     delete m_server;
-    destroyScreen(m_primaryScreen);
+    QWindowSystemInterface::handleScreenRemoved(m_primaryScreen);
 }
 
 void QVncIntegration::initialize()
 {
     if (m_primaryScreen->initialize())
-        screenAdded(m_primaryScreen);
+        QWindowSystemInterface::handleScreenAdded(m_primaryScreen);
     else
         qWarning("vnc: Failed to initialize screen");
 
diff --git a/src/plugins/platforms/wasm/qwasmintegration.cpp b/src/plugins/platforms/wasm/qwasmintegration.cpp
index 1964cefdad..486f4cb2b3 100644
--- a/src/plugins/platforms/wasm/qwasmintegration.cpp
+++ b/src/plugins/platforms/wasm/qwasmintegration.cpp
@@ -98,7 +98,10 @@ QWasmIntegration::QWasmIntegration()
 QWasmIntegration::~QWasmIntegration()
 {
     delete m_fontDb;
-    qDeleteAll(m_screens);
+
+    while (!m_screens.isEmpty())
+        QWindowSystemInterface::handleScreenRemoved(m_screens.takeLast());
+
     s_instance = nullptr;
 }
 
@@ -113,7 +116,7 @@ bool QWasmIntegration::hasCapability(QPlatformIntegration::Capability cap) const
     switch (cap) {
     case ThreadedPixmaps: return true;
     case OpenGL: return true;
-    case ThreadedOpenGL: return true;
+    case ThreadedOpenGL: return false;
     case RasterGLSurface: return false; // to enable this you need to fix qopenglwidget and quickwidget for wasm
     case MultipleWindows: return true;
     case WindowManagement: return true;
@@ -191,7 +194,7 @@ void QWasmIntegration::addScreen(const QString &canvasId)
     QWasmScreen *screen = new QWasmScreen(canvasId);
     m_clipboard->installEventHandlers(canvasId);
     m_screens.append(screen);
-    screenAdded(screen);
+    QWindowSystemInterface::handleScreenAdded(screen);
 }
 
 QT_END_NAMESPACE
diff --git a/src/plugins/platforms/wasm/wasm_shell.html b/src/plugins/platforms/wasm/wasm_shell.html
index 39bb711b6b..6ad7886ed4 100644
--- a/src/plugins/platforms/wasm/wasm_shell.html
+++ b/src/plugins/platforms/wasm/wasm_shell.html
@@ -27,9 +27,9 @@
 
     <script type='text/javascript'>
         function init() {
-          var spinner = document.getElementById('qtspinner');
-          var canvas = document.getElementById('qtcanvas');
-          var status = document.getElementById('qtstatus')
+          var spinner = document.querySelector('#qtspinner');
+          var canvas = document.querySelector('#qtcanvas');
+          var status = document.querySelector('#qtstatus')
 
           var qtLoader = QtLoader({
               canvasElements : [canvas],
diff --git a/src/plugins/platforms/windows/qwindowsintegration.h b/src/plugins/platforms/windows/qwindowsintegration.h
index da86852766..e28b2c2fb3 100644
--- a/src/plugins/platforms/windows/qwindowsintegration.h
+++ b/src/plugins/platforms/windows/qwindowsintegration.h
@@ -107,9 +107,6 @@ public:
 
     static QWindowsIntegration *instance() { return m_instance; }
 
-    inline void emitScreenAdded(QPlatformScreen *s, bool isPrimary = false) { screenAdded(s, isPrimary); }
-    inline void emitDestroyScreen(QPlatformScreen *s) { destroyScreen(s); }
-
     unsigned options() const;
 
     void beep() const override;
diff --git a/src/plugins/platforms/windows/qwindowsscreen.cpp b/src/plugins/platforms/windows/qwindowsscreen.cpp
index a161dc46e9..0520f88935 100644
--- a/src/plugins/platforms/windows/qwindowsscreen.cpp
+++ b/src/plugins/platforms/windows/qwindowsscreen.cpp
@@ -121,7 +121,7 @@ BOOL QT_WIN_CALLBACK monitorEnumCallback(HMONITOR hMonitor, HDC, LPRECT, LPARAM
     QWindowsScreenData data;
     if (monitorData(hMonitor, &data)) {
         WindowsScreenDataList *result = reinterpret_cast<WindowsScreenDataList *>(p);
-        // QPlatformIntegration::screenAdded() documentation specifies that first
+        // QWindowSystemInterface::handleScreenAdded() documentation specifies that first
         // added screen will be the primary screen, so order accordingly.
         // Note that the side effect of this policy is that there is no way to change primary
         // screen reported by Qt, unless we want to delete all existing screens and add them
@@ -521,7 +521,7 @@ void QWindowsScreenManager::removeScreen(int index)
         if (movedWindowCount)
             QWindowSystemInterface::flushWindowSystemEvents();
     }
-    QWindowsIntegration::instance()->emitDestroyScreen(m_screens.takeAt(index));
+    QWindowSystemInterface::handleScreenRemoved(m_screens.takeAt(index));
 }
 
 /*!
@@ -541,7 +541,7 @@ bool QWindowsScreenManager::handleScreenChanges()
         } else {
             QWindowsScreen *newScreen = new QWindowsScreen(newData);
             m_screens.push_back(newScreen);
-            QWindowsIntegration::instance()->emitScreenAdded(newScreen,
+            QWindowSystemInterface::handleScreenAdded(newScreen,
                                                              newData.flags & QWindowsScreenData::PrimaryScreen);
             qCDebug(lcQpaWindows) << "New Monitor: " << newData;
         }    // exists
@@ -561,7 +561,7 @@ void QWindowsScreenManager::clearScreens()
 {
     // Delete screens in reverse order to avoid crash in case of multiple screens
     while (!m_screens.isEmpty())
-        QWindowsIntegration::instance()->emitDestroyScreen(m_screens.takeLast());
+        QWindowSystemInterface::handleScreenRemoved(m_screens.takeLast());
 }
 
 const QWindowsScreen *QWindowsScreenManager::screenAtDp(const QPoint &p) const
diff --git a/src/plugins/platforms/windows/qwindowswindow.cpp b/src/plugins/platforms/windows/qwindowswindow.cpp
index 8bf090bf03..07fd2916c2 100644
--- a/src/plugins/platforms/windows/qwindowswindow.cpp
+++ b/src/plugins/platforms/windows/qwindowswindow.cpp
@@ -1759,15 +1759,12 @@ void QWindowsWindow::checkForScreenChanged()
 
     QPlatformScreen *currentScreen = screen();
     const auto &screenManager = QWindowsContext::instance()->screenManager();
-    // QTBUG-62971: When dragging a window by its border, detect by mouse position
-    // to prevent it from oscillating between screens when it resizes
-    const QWindowsScreen *newScreen = testFlag(ResizeMoveActive)
-        ? screenManager.screenAtDp(QWindowsCursor::mousePosition())
-        : screenManager.screenForHwnd(m_data.hwnd);
+    const QWindowsScreen *newScreen = screenManager.screenForHwnd(m_data.hwnd);
     if (newScreen != nullptr && newScreen != currentScreen) {
         qCDebug(lcQpaWindows).noquote().nospace() << __FUNCTION__
             << ' ' << window() << " \"" << currentScreen->name()
             << "\"->\"" << newScreen->name() << '"';
+        setFlag(SynchronousGeometryChangeEvent);
         QWindowSystemInterface::handleWindowScreenChanged(window(), newScreen->screen());
     }
 }
@@ -1786,11 +1783,14 @@ void QWindowsWindow::handleGeometryChange()
         fireExpose(QRect(QPoint(0, 0), m_data.geometry.size()), true);
     }
 
+    const bool wasSync = testFlag(SynchronousGeometryChangeEvent);
     checkForScreenChanged();
 
     if (testFlag(SynchronousGeometryChangeEvent))
         QWindowSystemInterface::flushWindowSystemEvents(QEventLoop::ExcludeUserInputEvents);
 
+    if (!wasSync)
+        clearFlag(SynchronousGeometryChangeEvent);
     qCDebug(lcQpaEvents) << __FUNCTION__ << this << window() << m_data.geometry;
 }
 
diff --git a/src/plugins/platforms/winrt/qwinrtintegration.cpp b/src/plugins/platforms/winrt/qwinrtintegration.cpp
index 78cbc3aec3..27d3746933 100644
--- a/src/plugins/platforms/winrt/qwinrtintegration.cpp
+++ b/src/plugins/platforms/winrt/qwinrtintegration.cpp
@@ -133,7 +133,7 @@ QWinRTIntegration::QWinRTIntegration() : d_ptr(new QWinRTIntegrationPrivate)
     });
     d->inputContext.reset(new QWinRTInputContext(d->mainScreen));
 
-    screenAdded(d->mainScreen);
+    QWindowSystemInterface::handleScreenAdded(d->mainScreen);
     d->platformServices = new QWinRTServices;
     d->clipboard = new QWinRTClipboard;
 #if QT_CONFIG(accessibility)
@@ -154,7 +154,7 @@ QWinRTIntegration::~QWinRTIntegration()
         Q_ASSERT_SUCCEEDED(hr);
     }
 
-    destroyScreen(d->mainScreen);
+    QWindowSystemInterface::handleScreenRemoved(d->mainScreen);
     Windows::Foundation::Uninitialize();
 }
 
diff --git a/src/plugins/platforms/xcb/gl_integrations/xcb_glx/qglxintegration.cpp b/src/plugins/platforms/xcb/gl_integrations/xcb_glx/qglxintegration.cpp
index d42a33c22b..476de6d1e5 100644
--- a/src/plugins/platforms/xcb/gl_integrations/xcb_glx/qglxintegration.cpp
+++ b/src/plugins/platforms/xcb/gl_integrations/xcb_glx/qglxintegration.cpp
@@ -652,6 +652,12 @@ static const char *qglx_threadedgl_blacklist_renderer[] = {
     0
 };
 
+static const char *qglx_threadedgl_blacklist_vendor[] = {
+    "llvmpipe",                             // QTCREATORBUG-10666
+    "nouveau",                              // https://bugs.freedesktop.org/show_bug.cgi?id=91632
+    nullptr
+};
+
 void QGLXContext::queryDummyContext()
 {
     if (m_queriedDummyContext)
@@ -710,6 +716,18 @@ void QGLXContext::queryDummyContext()
             }
         }
     }
+    if (const char *vendor = (const char *) glGetString(GL_VENDOR)) {
+        for (int i = 0; qglx_threadedgl_blacklist_vendor[i]; ++i) {
+            if (strstr(vendor, qglx_threadedgl_blacklist_vendor[i]) != 0) {
+                qCDebug(lcQpaGl).nospace() << "Multithreaded OpenGL disabled: "
+                                              "blacklisted vendor \""
+                                           << qglx_threadedgl_blacklist_vendor[i]
+                                           << "\"";
+                m_supportsThreading = false;
+                break;
+            }
+        }
+    }
 
     if (glxvendor && m_supportsThreading) {
         // Blacklist Mesa drivers due to QTCREATORBUG-10875 (crash in creator),
diff --git a/src/plugins/platforms/xcb/nativepainting/qbackingstore_x11.cpp b/src/plugins/platforms/xcb/nativepainting/qbackingstore_x11.cpp
index ed482e5dae..bbc156fc53 100644
--- a/src/plugins/platforms/xcb/nativepainting/qbackingstore_x11.cpp
+++ b/src/plugins/platforms/xcb/nativepainting/qbackingstore_x11.cpp
@@ -192,6 +192,10 @@ bool QXcbNativeBackingStore::scroll(const QRegion &area, int dx, int dy)
 
 void QXcbNativeBackingStore::beginPaint(const QRegion &region)
 {
+    QX11PlatformPixmap *x11pm = qt_x11Pixmap(m_pixmap);
+    if (x11pm)
+        x11pm->setIsBackingStore(true);
+
 #if QT_CONFIG(xrender)
     if (m_translucentBackground) {
         const QVector<XRectangle> xrects = qt_region_to_xrectangles(region);
diff --git a/src/plugins/platforms/xcb/nativepainting/qpaintengine_x11.cpp b/src/plugins/platforms/xcb/nativepainting/qpaintengine_x11.cpp
index 2688d6e884..3377eeaae9 100644
--- a/src/plugins/platforms/xcb/nativepainting/qpaintengine_x11.cpp
+++ b/src/plugins/platforms/xcb/nativepainting/qpaintengine_x11.cpp
@@ -200,6 +200,7 @@ public:
     uint has_pattern : 1;
     uint has_alpha_pen : 1;
     uint has_alpha_brush : 1;
+    uint use_sysclip : 1;
     uint render_hints;
 
     const QXcbX11Info *xinfo;
@@ -701,6 +702,9 @@ bool QX11PaintEngine::begin(QPaintDevice *pdev)
     d->xlibMaxLinePoints = 32762; // a safe number used to avoid, call to XMaxRequestSize(d->dpy) - 3;
     d->opacity = 1;
 
+    QX11PlatformPixmap *x11pm = paintDevice()->devType() == QInternal::Pixmap ? qt_x11Pixmap(*static_cast<QPixmap *>(paintDevice())) : nullptr;
+    d->use_sysclip = paintDevice()->devType() == QInternal::Widget || (x11pm ? x11pm->isBackingStore() : false);
+
     // Set up the polygon clipper. Note: This will only work in
     // polyline mode as long as we have a buffer zone, since a
     // polyline may be clipped into several non-connected polylines.
@@ -1472,7 +1476,7 @@ void QX11PaintEngine::updatePen(const QPen &pen)
     }
 
     if (!d->has_clipping) { // if clipping is set the paintevent clip region is merged with the clip region
-        QRegion sysClip = systemClip();
+        QRegion sysClip = d->use_sysclip ? systemClip() : QRegion();
         if (!sysClip.isEmpty())
             x11SetClipRegion(d->dpy, d->gc, 0, d->picture, sysClip);
         else
@@ -1603,7 +1607,7 @@ void QX11PaintEngine::updateBrush(const QBrush &brush, const QPointF &origin)
     vals.fill_style = s;
     XChangeGC(d->dpy, d->gc_brush, mask, &vals);
     if (!d->has_clipping) {
-        QRegion sysClip = systemClip();
+        QRegion sysClip = d->use_sysclip ? systemClip() : QRegion();
         if (!sysClip.isEmpty())
             x11SetClipRegion(d->dpy, d->gc_brush, 0, d->picture, sysClip);
         else
@@ -2223,7 +2227,7 @@ void QX11PaintEngine::updateMatrix(const QTransform &mtx)
 void QX11PaintEngine::updateClipRegion_dev(const QRegion &clipRegion, Qt::ClipOperation op)
 {
     Q_D(QX11PaintEngine);
-    QRegion sysClip = systemClip();
+    QRegion sysClip = d->use_sysclip ? systemClip() : QRegion();
     if (op == Qt::NoClip) {
         d->has_clipping = false;
         d->crgn = sysClip;
diff --git a/src/plugins/platforms/xcb/nativepainting/qpixmap_x11.cpp b/src/plugins/platforms/xcb/nativepainting/qpixmap_x11.cpp
index 86c87e5e30..b1ce39f363 100644
--- a/src/plugins/platforms/xcb/nativepainting/qpixmap_x11.cpp
+++ b/src/plugins/platforms/xcb/nativepainting/qpixmap_x11.cpp
@@ -1772,6 +1772,20 @@ XID QX11PlatformPixmap::createBitmapFromImage(const QImage &image)
     return hd;
 }
 
+bool QX11PlatformPixmap::isBackingStore() const
+{
+    return (flags & IsBackingStore);
+}
+
+void QX11PlatformPixmap::setIsBackingStore(bool on)
+{
+    if (on)
+        flags |= IsBackingStore;
+    else {
+        flags &= ~IsBackingStore;
+    }
+}
+
 #if QT_CONFIG(xrender)
 void QX11PlatformPixmap::convertToARGB32(bool preserveContents)
 {
diff --git a/src/plugins/platforms/xcb/nativepainting/qpixmap_x11_p.h b/src/plugins/platforms/xcb/nativepainting/qpixmap_x11_p.h
index 7392cbfccf..9c0ba98300 100644
--- a/src/plugins/platforms/xcb/nativepainting/qpixmap_x11_p.h
+++ b/src/plugins/platforms/xcb/nativepainting/qpixmap_x11_p.h
@@ -90,6 +90,8 @@ public:
     void convertToARGB32(bool preserveContents = true);
 #endif
 
+    bool isBackingStore() const;
+    void setIsBackingStore(bool on);
 private:
     friend class QX11PaintEngine;
     friend const QXcbX11Info &qt_x11Info(const QPixmap &pixmap);
@@ -110,7 +112,8 @@ private:
         Uninitialized = 0x1,
         Readonly = 0x2,
         InvertedWhenBoundToTexture = 0x4,
-        GlSurfaceCreatedWithAlpha = 0x8
+        GlSurfaceCreatedWithAlpha = 0x8,
+        IsBackingStore = 0x10
     };
     uint flags;
 
diff --git a/src/plugins/platforms/xcb/qxcbconnection.cpp b/src/plugins/platforms/xcb/qxcbconnection.cpp
index e35b97dab4..d27a288feb 100644
--- a/src/plugins/platforms/xcb/qxcbconnection.cpp
+++ b/src/plugins/platforms/xcb/qxcbconnection.cpp
@@ -152,10 +152,9 @@ QXcbConnection::~QXcbConnection()
     if (m_eventQueue)
         delete m_eventQueue;
 
-    QXcbIntegration *integration = QXcbIntegration::instance();
     // Delete screens in reverse order to avoid crash in case of multiple screens
     while (!m_screens.isEmpty())
-        integration->destroyScreen(m_screens.takeLast());
+        QWindowSystemInterface::handleScreenRemoved(m_screens.takeLast());
 
     while (!m_virtualDesktops.isEmpty())
         delete m_virtualDesktops.takeLast();
diff --git a/src/plugins/platforms/xcb/qxcbconnection_basic.h b/src/plugins/platforms/xcb/qxcbconnection_basic.h
index 3691763398..b979129cba 100644
--- a/src/plugins/platforms/xcb/qxcbconnection_basic.h
+++ b/src/plugins/platforms/xcb/qxcbconnection_basic.h
@@ -40,6 +40,7 @@
 #define QXCBBASICCONNECTION_H
 
 #include "qxcbatom.h"
+#include "qxcbexport.h"
 
 #include <QtCore/QPair>
 #include <QtCore/QObject>
@@ -55,7 +56,7 @@ QT_BEGIN_NAMESPACE
 
 Q_DECLARE_LOGGING_CATEGORY(lcQpaXcb)
 
-class QXcbBasicConnection : public QObject
+class Q_XCB_EXPORT QXcbBasicConnection : public QObject
 {
     Q_OBJECT
 public:
diff --git a/src/plugins/platforms/xcb/qxcbconnection_screens.cpp b/src/plugins/platforms/xcb/qxcbconnection_screens.cpp
index 4bafe83156..9ba71ada37 100644
--- a/src/plugins/platforms/xcb/qxcbconnection_screens.cpp
+++ b/src/plugins/platforms/xcb/qxcbconnection_screens.cpp
@@ -44,6 +44,8 @@
 #include <QtCore/QString>
 #include <QtCore/QList>
 
+#include <qpa/qwindowsysteminterface.h>
+
 #include <xcb/xinerama.h>
 
 void QXcbConnection::xrandrSelectEvents()
@@ -211,7 +213,7 @@ void QXcbConnection::updateScreen(QXcbScreen *screen, const xcb_randr_output_cha
                 m_screens.swapItemsAt(0, idx);
             }
             screen->virtualDesktop()->setPrimaryScreen(screen);
-            QXcbIntegration::instance()->setPrimaryScreen(screen);
+            QWindowSystemInterface::handlePrimaryScreenChanged(screen);
         }
     }
 }
@@ -234,7 +236,7 @@ QXcbScreen *QXcbConnection::createScreen(QXcbVirtualDesktop *virtualDesktop,
         m_screens.append(screen);
     }
     virtualDesktop->addScreen(screen);
-    QXcbIntegration::instance()->screenAdded(screen, screen->isPrimary());
+    QWindowSystemInterface::handleScreenAdded(screen, screen->isPrimary());
 
     return screen;
 }
@@ -261,10 +263,10 @@ void QXcbConnection::destroyScreen(QXcbScreen *screen)
             const int idx = m_screens.indexOf(newPrimary);
             if (idx > 0)
                 m_screens.swapItemsAt(0, idx);
-            QXcbIntegration::instance()->setPrimaryScreen(newPrimary);
+            QWindowSystemInterface::handlePrimaryScreenChanged(newPrimary);
         }
 
-        QXcbIntegration::instance()->destroyScreen(screen);
+        QWindowSystemInterface::handleScreenRemoved(screen);
     }
 }
 
@@ -406,7 +408,7 @@ void QXcbConnection::initializeScreens()
         // Push the screens to QGuiApplication
         for (QXcbScreen *screen : qAsConst(m_screens)) {
             qCDebug(lcQpaScreen) << "adding" << screen << "(Primary:" << screen->isPrimary() << ")";
-            QXcbIntegration::instance()->screenAdded(screen, screen->isPrimary());
+            QWindowSystemInterface::handleScreenAdded(screen, screen->isPrimary());
         }
 
         qCDebug(lcQpaScreen) << "primary output is" << qAsConst(m_screens).first()->name();
diff --git a/src/plugins/platforms/xcb/qxcbintegration.h b/src/plugins/platforms/xcb/qxcbintegration.h
index f13e232291..571726c354 100644
--- a/src/plugins/platforms/xcb/qxcbintegration.h
+++ b/src/plugins/platforms/xcb/qxcbintegration.h
@@ -137,8 +137,6 @@ private:
 
     QScopedPointer<QPlatformServices> m_services;
 
-    friend class QXcbConnection; // access QPlatformIntegration::screenAdded()
-
     mutable QByteArray m_wmClass;
     const char *m_instanceName;
     bool m_canGrab;
diff --git a/src/plugins/platforms/xcb/qxcbnativeinterface.cpp b/src/plugins/platforms/xcb/qxcbnativeinterface.cpp
index 4d526a6bda..899081e752 100644
--- a/src/plugins/platforms/xcb/qxcbnativeinterface.cpp
+++ b/src/plugins/platforms/xcb/qxcbnativeinterface.cpp
@@ -412,12 +412,15 @@ void *QXcbNativeInterface::atspiBus()
         auto reply = Q_XCB_REPLY(xcb_get_property, defaultConnection->xcb_connection(),
                                      false, defaultConnection->rootWindow(),
                                      atspiBusAtom, XCB_ATOM_STRING, 0, 128);
-        Q_ASSERT(!reply->bytes_after);
+        if (!reply)
+            return nullptr;
+
         char *data = (char *)xcb_get_property_value(reply.get());
         int length = xcb_get_property_value_length(reply.get());
         return new QByteArray(data, length);
     }
-    return 0;
+
+    return nullptr;
 }
 
 void QXcbNativeInterface::setAppTime(QScreen* screen, xcb_timestamp_t time)
diff --git a/src/tools/androiddeployqt/main.cpp b/src/tools/androiddeployqt/main.cpp
index fd7f72eebf..3af5237f3d 100644
--- a/src/tools/androiddeployqt/main.cpp
+++ b/src/tools/androiddeployqt/main.cpp
@@ -900,7 +900,7 @@ bool readInputFile(Options *options)
             options->extraPlugins = extraPlugins.toString().split(QLatin1Char(','));
     }
 
-    {
+    if (!options->auxMode) {
         const QJsonValue stdcppPath = jsonObject.value(QStringLiteral("stdcpp-path"));
         if (stdcppPath.isUndefined()) {
             fprintf(stderr, "No stdcpp-path defined in json file.\n");
diff --git a/src/widgets/dialogs/qdialog.h b/src/widgets/dialogs/qdialog.h
index ce57ce5de7..ce2194a1de 100644
--- a/src/widgets/dialogs/qdialog.h
+++ b/src/widgets/dialogs/qdialog.h
@@ -70,10 +70,10 @@ public:
     void setVisible(bool visible) override;
 
 #if QT_DEPRECATED_SINCE(5, 13)
-    QT_DEPRECATED void setOrientation(Qt::Orientation orientation);
-    QT_DEPRECATED Qt::Orientation orientation() const;
-    QT_DEPRECATED void setExtension(QWidget* extension);
-    QT_DEPRECATED QWidget* extension() const;
+    QT_DEPRECATED_X("Use show/hide on the affected widget instead") void setOrientation(Qt::Orientation orientation);
+    QT_DEPRECATED_X("Use show/hide on the affected widget instead") Qt::Orientation orientation() const;
+    QT_DEPRECATED_X("Use show/hide on the affected widget instead") void setExtension(QWidget* extension);
+    QT_DEPRECATED_X("Use show/hide on the affected widget instead") QWidget* extension() const;
 #endif
 
     QSize sizeHint() const override;
@@ -98,7 +98,7 @@ public Q_SLOTS:
     virtual void reject();
 
 #if QT_DEPRECATED_SINCE(5, 13)
-    QT_DEPRECATED void showExtension(bool);
+    QT_DEPRECATED_X("Use show/hide on the affected widget instead") void showExtension(bool);
 #endif
 
 protected:
diff --git a/src/widgets/kernel/qgesturemanager.cpp b/src/widgets/kernel/qgesturemanager.cpp
index 57d6994c88..cd27c9c5be 100644
--- a/src/widgets/kernel/qgesturemanager.cpp
+++ b/src/widgets/kernel/qgesturemanager.cpp
@@ -143,11 +143,6 @@ Qt::GestureType QGestureManager::registerGestureRecognizer(QGestureRecognizer *r
 void QGestureManager::unregisterGestureRecognizer(Qt::GestureType type)
 {
     QList<QGestureRecognizer *> list = m_recognizers.values(type);
-    while (QGestureRecognizer *recognizer = m_recognizers.take(type)) {
-        // ensuring an entry exists causes the recognizer to be deleted on destruction of the manager
-        auto &gestures = m_obsoleteGestures[recognizer];
-        Q_UNUSED(gestures);
-    }
     foreach (QGesture *g, m_gestureToRecognizer.keys()) {
         QGestureRecognizer *recognizer = m_gestureToRecognizer.value(g);
         if (list.contains(recognizer)) {
diff --git a/src/widgets/kernel/qgesturerecognizer.cpp b/src/widgets/kernel/qgesturerecognizer.cpp
index 65c46a5e56..75d091ce4e 100644
--- a/src/widgets/kernel/qgesturerecognizer.cpp
+++ b/src/widgets/kernel/qgesturerecognizer.cpp
@@ -41,6 +41,7 @@
 
 #include "private/qgesture_p.h"
 #include "private/qgesturemanager_p.h"
+#include "private/qapplication_p.h"
 
 #ifndef QT_NO_GESTURES
 
@@ -231,6 +232,11 @@ Qt::GestureType QGestureRecognizer::registerRecognizer(QGestureRecognizer *recog
 */
 void QGestureRecognizer::unregisterRecognizer(Qt::GestureType type)
 {
+    auto qAppPriv = QApplicationPrivate::instance();
+    if (!qAppPriv)
+        return;
+    if (!qAppPriv->gestureManager)
+        return;
     QGestureManager::instance()->unregisterGestureRecognizer(type);
 }
 
diff --git a/src/widgets/styles/qstyle.cpp b/src/widgets/styles/qstyle.cpp
index ac4fb7fbd1..97ec1d3f19 100644
--- a/src/widgets/styles/qstyle.cpp
+++ b/src/widgets/styles/qstyle.cpp
@@ -1971,8 +1971,8 @@ void QStyle::drawItemPixmap(QPainter *painter, const QRect &rect, int alignment,
 
     \value SH_Widget_Animate Deprecated. Use \l{SH_Widget_Animation_Duration} instead.
 
-    \value SH_Splitter_OpaqueResize Determines if resizing is opaque
-           This enum value has been introduced in Qt 5.2
+    \value SH_Splitter_OpaqueResize Determines if widgets are resized dynamically (opaquely) while
+           interactively moving the splitter. This enum value was introduced in Qt 5.2.
 
     \value SH_TabBar_ChangeCurrentDelay Determines the delay before the current
            tab is changed while dragging over the tabbar, in milliseconds. This
diff --git a/src/widgets/widgets/qdockwidget.cpp b/src/widgets/widgets/qdockwidget.cpp
index ba8bd90da6..4041c730b8 100644
--- a/src/widgets/widgets/qdockwidget.cpp
+++ b/src/widgets/widgets/qdockwidget.cpp
@@ -67,18 +67,21 @@ extern QString qt_setWindowTitle_helperHelper(const QString&, const QWidget*); /
 // qmainwindow.cpp
 extern QMainWindowLayout *qt_mainwindow_layout(const QMainWindow *window);
 
-static inline QMainWindowLayout *qt_mainwindow_layout_from_dock(const QDockWidget *dock)
+static const QMainWindow *mainwindow_from_dock(const QDockWidget *dock)
 {
-    const QWidget *p = dock->parentWidget();
-    while (p) {
-        const QMainWindow *window = qobject_cast<const QMainWindow*>(p);
-        if (window)
-            return qt_mainwindow_layout(window);
-        p = p->parentWidget();
+    for (const QWidget *p = dock->parentWidget(); p; p = p->parentWidget()) {
+        if (const QMainWindow *window = qobject_cast<const QMainWindow*>(p))
+            return window;
     }
     return nullptr;
 }
 
+static inline QMainWindowLayout *qt_mainwindow_layout_from_dock(const QDockWidget *dock)
+{
+    auto mainWindow = mainwindow_from_dock(dock);
+    return mainWindow ? qt_mainwindow_layout(mainWindow) : nullptr;
+}
+
 static inline bool hasFeature(const QDockWidgetPrivate *priv, QDockWidget::DockWidgetFeature feature)
 { return (priv->features & feature) == feature; }
 
@@ -839,8 +842,9 @@ void QDockWidgetPrivate::endDrag(bool abort)
     q->releaseMouse();
 
     if (state->dragging) {
-        QMainWindowLayout *mwLayout = qt_mainwindow_layout_from_dock(q);
-        Q_ASSERT(mwLayout != 0);
+        const QMainWindow *mainWindow = mainwindow_from_dock(q);
+        Q_ASSERT(mainWindow != nullptr);
+        QMainWindowLayout *mwLayout = qt_mainwindow_layout(mainWindow);
 
         if (abort || !mwLayout->plug(state->widgetItem)) {
             if (hasFeature(this, QDockWidget::DockWidgetFloatable)) {
@@ -861,8 +865,12 @@ void QDockWidgetPrivate::endDrag(bool abort)
                 } else {
                     setResizerActive(false);
                 }
-                if (q->isFloating()) // Might not be floating when dragging a QDockWidgetGroupWindow
+                if (q->isFloating()) { // Might not be floating when dragging a QDockWidgetGroupWindow
                     undockedGeometry = q->geometry();
+#if QT_CONFIG(tabwidget)
+                    tabPosition = mwLayout->tabPosition(mainWindow->dockWidgetArea(q));
+#endif
+                }
                 q->activateWindow();
             } else {
                 // The tab was not plugged back in the QMainWindow but the QDockWidget cannot
diff --git a/src/widgets/widgets/qdockwidget_p.h b/src/widgets/widgets/qdockwidget_p.h
index 2543f10f97..bc6ac86c45 100644
--- a/src/widgets/widgets/qdockwidget_p.h
+++ b/src/widgets/widgets/qdockwidget_p.h
@@ -57,6 +57,10 @@
 #include "QtWidgets/qboxlayout.h"
 #include "QtWidgets/qdockwidget.h"
 
+#if QT_CONFIG(tabwidget)
+#  include "QtWidgets/qtabwidget.h"
+#endif
+
 QT_REQUIRE_CONFIG(dockwidget);
 
 QT_BEGIN_NAMESPACE
@@ -81,28 +85,26 @@ class QDockWidgetPrivate : public QWidgetPrivate
     };
 
 public:
-    inline QDockWidgetPrivate()
-        : QWidgetPrivate(), state(nullptr),
-          features(QDockWidget::DockWidgetClosable
-                   | QDockWidget::DockWidgetMovable
-                   | QDockWidget::DockWidgetFloatable),
-          allowedAreas(Qt::AllDockWidgetAreas), resizer(nullptr)
-    { }
-
     void init();
     void _q_toggleView(bool); // private slot
     void _q_toggleTopLevel(); // private slot
 
     void updateButtons();
-    DragState *state;
 
-    QDockWidget::DockWidgetFeatures features;
-    Qt::DockWidgetAreas allowedAreas;
+#if QT_CONFIG(tabwidget)
+    QTabWidget::TabPosition tabPosition = QTabWidget::North;
+#endif
+
+    DragState *state = nullptr;
+
+    QDockWidget::DockWidgetFeatures features = QDockWidget::DockWidgetClosable
+        | QDockWidget::DockWidgetMovable | QDockWidget::DockWidgetFloatable;
+    Qt::DockWidgetAreas allowedAreas = Qt::AllDockWidgetAreas;
 
     QFont font;
 
 #ifndef QT_NO_ACTION
-    QAction *toggleViewAction;
+    QAction *toggleViewAction = nullptr;
 #endif
 
 //    QMainWindow *findMainWindow(QWidget *widget) const;
@@ -129,7 +131,7 @@ public:
     bool isAnimating() const;
 
 private:
-    QWidgetResizeHandler *resizer;
+    QWidgetResizeHandler *resizer = nullptr;
 };
 
 class Q_WIDGETS_EXPORT QDockWidgetLayout : public QLayout
diff --git a/src/widgets/widgets/qmainwindowlayout.cpp b/src/widgets/widgets/qmainwindowlayout.cpp
index ed054c7e9a..f54835f23b 100644
--- a/src/widgets/widgets/qmainwindowlayout.cpp
+++ b/src/widgets/widgets/qmainwindowlayout.cpp
@@ -2525,6 +2525,30 @@ void QMainWindowLayout::updateGapIndicator()
 #endif // QT_CONFIG(rubberband)
 }
 
+static QTabBar::Shape tabwidgetPositionToTabBarShape(QWidget *w)
+{
+    QTabBar::Shape result = QTabBar::RoundedSouth;
+#if QT_CONFIG(tabwidget)
+    if (qobject_cast<QDockWidget *>(w)) {
+        switch (static_cast<QDockWidgetPrivate *>(qt_widget_private(w))->tabPosition) {
+        case QTabWidget::North:
+            result = QTabBar::RoundedNorth;
+            break;
+        case QTabWidget::South:
+            result = QTabBar::RoundedSouth;
+            break;
+        case QTabWidget::West:
+            result = QTabBar::RoundedWest;
+            break;
+        case QTabWidget::East:
+            result = QTabBar::RoundedEast;
+            break;
+        }
+    }
+#endif // tabwidget
+    return result;
+}
+
 void QMainWindowLayout::hover(QLayoutItem *widgetItem, const QPoint &mousePos)
 {
     if (!parentWidget()->isVisible() || parentWidget()->isMinimized()
@@ -2573,8 +2597,9 @@ void QMainWindowLayout::hover(QLayoutItem *widgetItem, const QPoint &mousePos)
                 QDockWidgetGroupWindow *floatingTabs = createTabbedDockWindow(); // FIXME
                 floatingTabs->setGeometry(dropTo->geometry());
                 QDockAreaLayoutInfo *info = floatingTabs->layoutInfo();
+                const QTabBar::Shape shape = tabwidgetPositionToTabBarShape(dropTo);
                 *info = QDockAreaLayoutInfo(&layoutState.dockAreaLayout.sep, QInternal::LeftDock,
-                                            Qt::Horizontal, QTabBar::RoundedSouth,
+                                            Qt::Horizontal, shape,
                                             static_cast<QMainWindow *>(parentWidget()));
                 info->tabbed = true;
                 QLayout *parentLayout = dropTo->parentWidget()->layout();
diff --git a/src/widgets/widgets/qsplashscreen.cpp b/src/widgets/widgets/qsplashscreen.cpp
index 4af4f90119..bf6bf1c7c9 100644
--- a/src/widgets/widgets/qsplashscreen.cpp
+++ b/src/widgets/widgets/qsplashscreen.cpp
@@ -289,8 +289,7 @@ void QSplashScreen::setPixmap(const QPixmap &pixmap)
 // 1) If a QDesktopScreenWidget is found in the parent hierarchy, use that (see docs on
 //    QSplashScreen(QWidget *, QPixmap).
 // 2) If a widget with associated QWindow is found, use that
-// 3) When nothing can be found, do not position the widget, allowing for
-//    QPlatformWindow::initialGeometry() to center it over the cursor
+// 3) When nothing can be found, try to center it over the cursor
 
 static inline int screenNumberOf(const QDesktopScreenWidget *dsw)
 {
@@ -307,7 +306,15 @@ const QScreen *QSplashScreenPrivate::screenFor(const QWidget *w)
         if (QWindow *window = p->windowHandle())
             return window->screen();
     }
-    return nullptr;
+#if QT_CONFIG(cursor)
+    // Note: We could rely on QPlatformWindow::initialGeometry() to center it
+    // over the cursor, but not all platforms (namely Android) use that.
+    if (QGuiApplication::screens().size() > 1) {
+        if (auto screenAtCursor = QGuiApplication::screenAt(QCursor::pos()))
+            return screenAtCursor;
+    }
+#endif // cursor
+    return QGuiApplication::primaryScreen();
 }
 
 void QSplashScreenPrivate::setPixmap(const QPixmap &p, const QScreen *screen)
diff --git a/src/widgets/widgets/qsplitter.cpp b/src/widgets/widgets/qsplitter.cpp
index 98bb23caad..de838a8f93 100644
--- a/src/widgets/widgets/qsplitter.cpp
+++ b/src/widgets/widgets/qsplitter.cpp
@@ -161,11 +161,10 @@ Qt::Orientation QSplitterHandle::orientation() const
 
 
 /*!
-    Returns \c true if widgets are resized dynamically (opaquely), otherwise
-    returns \c false. This value is controlled by the QSplitter.
+    Returns \c true if widgets are resized dynamically (opaquely) while interactively moving the
+    splitter. Otherwise returns \c false. This value is controlled by the QSplitter.
 
     \sa QSplitter::opaqueResize()
-
 */
 bool QSplitterHandle::opaqueResize() const
 {
@@ -1483,7 +1482,8 @@ int QSplitter::closestLegalPosition(int pos, int index)
 
 /*!
     \property QSplitter::opaqueResize
-    \brief whether resizing is opaque
+    Returns \c true if widgets are resized dynamically (opaquely) while interactively moving the
+    splitter. Otherwise returns \c false.
 
     The default resize behavior is style dependent (determined by the
     SH_Splitter_OpaqueResize style hint). However, you can override it