Merge remote-tracking branch 'origin/5.6' into 5.7

Conflicts:
	tests/auto/testlib/selftests/generate_expected_output.py

Change-Id: If856162abf9a24ae2c9946d336a7d1da03520fa7

18 files changed, 173 insertions, 97 deletions

diff --git a/src/corelib/global/qcompilerdetection.h b/src/corelib/global/qcompilerdetection.h
index 285931e794..d0eb2af423 100644
--- a/src/corelib/global/qcompilerdetection.h
+++ b/src/corelib/global/qcompilerdetection.h
@@ -950,7 +950,8 @@
 #    endif /* VC 11 */
 #    if _MSC_VER >= 1800
        /* C++11 features in VC12 = VC2013 */
-#      define Q_COMPILER_DEFAULT_MEMBERS
+/* Implemented, but can't be used on move special members */
+/* #      define Q_COMPILER_DEFAULT_MEMBERS */
 #      define Q_COMPILER_DELETE_MEMBERS
 #      define Q_COMPILER_DELEGATING_CONSTRUCTORS
 #      define Q_COMPILER_EXPLICIT_CONVERSIONS
@@ -968,6 +969,7 @@
 #    endif /* VC 12 SP 2 RC */
 #    if _MSC_VER >= 1900
        /* C++11 features in VC14 = VC2015 */
+#      define Q_COMPILER_DEFAULT_MEMBERS
 #      define Q_COMPILER_ALIGNAS
 #      define Q_COMPILER_ALIGNOF
 // Partial support, insufficient for Qt
diff --git a/src/corelib/tools/qbytearray.cpp b/src/corelib/tools/qbytearray.cpp
index c9d6f4e411..08a70a06c7 100644
--- a/src/corelib/tools/qbytearray.cpp
+++ b/src/corelib/tools/qbytearray.cpp
@@ -303,13 +303,14 @@ char *qstrncpy(char *dst, const char *src, uint len)
 {
     if (!src || !dst)
         return 0;
+    if (len > 0) {
 #if defined(_MSC_VER) && _MSC_VER >= 1400
-    strncpy_s(dst, len, src, len-1);
+        strncpy_s(dst, len, src, len - 1);
 #else
-    strncpy(dst, src, len);
+        strncpy(dst, src, len);
 #endif
-    if (len > 0)
         dst[len-1] = '\0';
+    }
     return dst;
 }
 
diff --git a/src/gui/image/qicon.cpp b/src/gui/image/qicon.cpp
index 716a7c52c2..db118edf04 100644
--- a/src/gui/image/qicon.cpp
+++ b/src/gui/image/qicon.cpp
@@ -841,8 +841,11 @@ QPixmap QIcon::pixmap(QWindow *window, const QSize &size, Mode mode, State state
     qreal devicePixelRatio = qt_effective_device_pixel_ratio(window);
 
     // Handle the simple normal-dpi case:
-    if (!(devicePixelRatio > 1.0))
-        return d->engine->pixmap(size, mode, state);
+    if (!(devicePixelRatio > 1.0)) {
+        QPixmap pixmap = d->engine->pixmap(size, mode, state);
+        pixmap.setDevicePixelRatio(1.0);
+        return pixmap;
+    }
 
     // Try get a pixmap that is big enough to be displayed at device pixel resolution.
     QPixmap pixmap = d->engine->pixmap(size * devicePixelRatio, mode, state);
diff --git a/src/gui/kernel/qwindow.cpp b/src/gui/kernel/qwindow.cpp
index 5f71bdaded..18e8bcf99c 100644
--- a/src/gui/kernel/qwindow.cpp
+++ b/src/gui/kernel/qwindow.cpp
@@ -2195,6 +2195,9 @@ void QWindowPrivate::deliverUpdateRequest()
 */
 void QWindow::requestUpdate()
 {
+    Q_ASSERT_X(QThread::currentThread() == QCoreApplication::instance()->thread(),
+        "QWindow", "Updates can only be scheduled from the GUI (main) thread");
+
     Q_D(QWindow);
     if (d->updateRequestPending || !d->platformWindow)
         return;
diff --git a/src/gui/opengl/qopenglframebufferobject.cpp b/src/gui/opengl/qopenglframebufferobject.cpp
index b6e8855d46..14581c89f6 100644
--- a/src/gui/opengl/qopenglframebufferobject.cpp
+++ b/src/gui/opengl/qopenglframebufferobject.cpp
@@ -1288,11 +1288,11 @@ static inline QImage qt_gl_read_framebuffer_rgba8(const QSize &size, bool includ
                               ? context->hasExtension(QByteArrayLiteral("GL_EXT_read_format_bgra"))
                               : context->hasExtension(QByteArrayLiteral("GL_EXT_bgra"));
 
+#ifndef Q_OS_IOS
     const char *renderer = reinterpret_cast<const char *>(funcs->glGetString(GL_RENDERER));
     const char *ver = reinterpret_cast<const char *>(funcs->glGetString(GL_VERSION));
 
     // Blacklist GPU chipsets that have problems with their BGRA support.
-#ifndef Q_OS_IOS
     const bool blackListed = (qstrcmp(renderer, "PowerVR Rogue G6200") == 0
                              && ::strstr(ver, "1.3") != 0) ||
                              (qstrcmp(renderer, "Mali-T760") == 0
diff --git a/src/gui/painting/qdrawhelper.cpp b/src/gui/painting/qdrawhelper.cpp
index 30d3dee473..867eb76200 100644
--- a/src/gui/painting/qdrawhelper.cpp
+++ b/src/gui/painting/qdrawhelper.cpp
@@ -5383,17 +5383,17 @@ static const ProcessSpans processTextureSpans[NBlendTypes][QImage::NImageFormats
         blend_src_generic, // ARGB32
         blend_transformed_argb, // ARGB32_Premultiplied
         blend_transformed_rgb565,
-        blend_src_generic,
-        blend_src_generic,
-        blend_src_generic,
-        blend_src_generic,
-        blend_src_generic,
-        blend_src_generic,
-        blend_src_generic,
-        blend_src_generic,
-        blend_src_generic,
-        blend_src_generic,
-        blend_src_generic,
+        blend_src_generic, // ARGB8565_Premultiplied
+        blend_src_generic, // RGB666
+        blend_src_generic, // ARGB6666_Premultiplied
+        blend_src_generic, // RGB555
+        blend_src_generic, // ARGB8555_Premultiplied
+        blend_src_generic, // RGB888
+        blend_src_generic, // RGB444
+        blend_src_generic, // ARGB4444_Premultiplied
+        blend_src_generic, // RGBX8888
+        blend_src_generic, // RGBA8888
+        blend_src_generic, // RGBA8888_Premultiplied
         blend_src_generic_rgb64,
         blend_src_generic_rgb64,
         blend_src_generic_rgb64,
@@ -5411,16 +5411,17 @@ static const ProcessSpans processTextureSpans[NBlendTypes][QImage::NImageFormats
         blend_src_generic, // ARGB32
         blend_transformed_tiled_argb, // ARGB32_Premultiplied
         blend_transformed_tiled_rgb565,
-        blend_src_generic,
-        blend_src_generic,
-        blend_src_generic,
-        blend_src_generic,
-        blend_src_generic,
-        blend_src_generic,
-        blend_src_generic,
-        blend_src_generic,
-        blend_src_generic,
-        blend_src_generic,
+        blend_src_generic, // ARGB8565_Premultiplied
+        blend_src_generic, // RGB666
+        blend_src_generic, // ARGB6666_Premultiplied
+        blend_src_generic, // RGB555
+        blend_src_generic, // ARGB8555_Premultiplied
+        blend_src_generic, // RGB888
+        blend_src_generic, // RGB444
+        blend_src_generic, // ARGB4444_Premultiplied
+        blend_src_generic, // RGBX8888
+        blend_src_generic, // RGBA8888
+        blend_src_generic, // RGBA8888_Premultiplied
         blend_src_generic_rgb64,
         blend_src_generic_rgb64,
         blend_src_generic_rgb64,
@@ -5438,17 +5439,17 @@ static const ProcessSpans processTextureSpans[NBlendTypes][QImage::NImageFormats
         blend_src_generic, // ARGB32
         blend_src_generic, // ARGB32_Premultiplied
         blend_transformed_bilinear_rgb565,
-        blend_src_generic,
-        blend_src_generic,
-        blend_src_generic,
-        blend_src_generic,
-        blend_src_generic,
-        blend_src_generic,
-        blend_src_generic,
-        blend_src_generic,
-        blend_src_generic,
-        blend_src_generic,
-        blend_src_generic,
+        blend_src_generic, // ARGB8565_Premultiplied
+        blend_src_generic, // RGB666
+        blend_src_generic, // ARGB6666_Premultiplied
+        blend_src_generic, // RGB555
+        blend_src_generic, // ARGB8555_Premultiplied
+        blend_src_generic, // RGB888
+        blend_src_generic, // RGB444
+        blend_src_generic, // ARGB4444_Premultiplied
+        blend_src_generic, // RGBX8888
+        blend_src_generic, // RGBA8888
+        blend_src_generic, // RGBA8888_Premultiplied
         blend_src_generic_rgb64,
         blend_src_generic_rgb64,
         blend_src_generic_rgb64,
diff --git a/src/gui/text/qfontdatabase.cpp b/src/gui/text/qfontdatabase.cpp
index c4a130e04c..283d03f22c 100644
--- a/src/gui/text/qfontdatabase.cpp
+++ b/src/gui/text/qfontdatabase.cpp
@@ -842,9 +842,13 @@ QStringList QPlatformFontDatabase::fallbacksForFamily(const QString &family, QFo
     return retList;
 }
 
+static void initializeDb();
+
 static QStringList fallbacksForFamily(const QString &family, QFont::Style style, QFont::StyleHint styleHint, QChar::Script script)
 {
     QFontDatabasePrivate *db = privateDb();
+    if (!db->count)
+        initializeDb();
 
     const FallbacksCacheKey cacheKey = { family, style, styleHint, script };
 
diff --git a/src/platformsupport/cglconvenience/cglconvenience.mm b/src/platformsupport/cglconvenience/cglconvenience.mm
index a18510a9e2..a4c5c7f61e 100644
--- a/src/platformsupport/cglconvenience/cglconvenience.mm
+++ b/src/platformsupport/cglconvenience/cglconvenience.mm
@@ -75,8 +75,11 @@ void *qcgl_createNSOpenGLPixelFormat(const QSurfaceFormat &format)
 
     QVector<NSOpenGLPixelFormatAttribute> attrs;
 
-    if (format.swapBehavior() != QSurfaceFormat::SingleBuffer)
+    if (format.swapBehavior() == QSurfaceFormat::DoubleBuffer
+        || format.swapBehavior() == QSurfaceFormat::DefaultSwapBehavior)
         attrs.append(NSOpenGLPFADoubleBuffer);
+    else if (format.swapBehavior() == QSurfaceFormat::TripleBuffer)
+        attrs.append(NSOpenGLPFATripleBuffer);
 
 #if MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_7
     if (QSysInfo::MacintoshVersion >= QSysInfo::MV_10_7) {
diff --git a/src/plugins/platforms/cocoa/qcocoaglcontext.mm b/src/plugins/platforms/cocoa/qcocoaglcontext.mm
index 7a12969972..628357eb39 100644
--- a/src/plugins/platforms/cocoa/qcocoaglcontext.mm
+++ b/src/plugins/platforms/cocoa/qcocoaglcontext.mm
@@ -312,8 +312,16 @@ void QCocoaGLContext::updateSurfaceFormat()
         m_format.setSamples(samples);
 
     int doubleBuffered = -1;
+    int tripleBuffered = -1;
     [pixelFormat getValues:&doubleBuffered forAttribute:NSOpenGLPFADoubleBuffer forVirtualScreen:0];
-    m_format.setSwapBehavior(doubleBuffered == 1 ? QSurfaceFormat::DoubleBuffer : QSurfaceFormat::SingleBuffer);
+    [pixelFormat getValues:&tripleBuffered forAttribute:NSOpenGLPFATripleBuffer forVirtualScreen:0];
+
+    if (tripleBuffered == 1)
+        m_format.setSwapBehavior(QSurfaceFormat::TripleBuffer);
+    else if (doubleBuffered == 1)
+        m_format.setSwapBehavior(QSurfaceFormat::DoubleBuffer);
+    else
+        m_format.setSwapBehavior(QSurfaceFormat::SingleBuffer);
 
     int steroBuffers = -1;
     [pixelFormat getValues:&steroBuffers forAttribute:NSOpenGLPFAStereo forVirtualScreen:0];
diff --git a/src/plugins/platforms/windows/qwindowsdialoghelpers.cpp b/src/plugins/platforms/windows/qwindowsdialoghelpers.cpp
index d5e5f87e5c..817728dca2 100644
--- a/src/plugins/platforms/windows/qwindowsdialoghelpers.cpp
+++ b/src/plugins/platforms/windows/qwindowsdialoghelpers.cpp
@@ -1050,12 +1050,15 @@ void QWindowsNativeFileDialogBase::setDirectory(const QUrl &directory)
 
 QString QWindowsNativeFileDialogBase::directory() const
 {
+    QString result;
 #ifndef Q_OS_WINCE
     IShellItem *item = 0;
-    if (m_fileDialog && SUCCEEDED(m_fileDialog->GetFolder(&item)) && item)
-        return QWindowsNativeFileDialogBase::itemPath(item);
+    if (m_fileDialog && SUCCEEDED(m_fileDialog->GetFolder(&item)) && item) {
+        result = QWindowsNativeFileDialogBase::itemPath(item);
+        item->Release();
+    }
 #endif
-    return QString();
+    return result;
 }
 
 void QWindowsNativeFileDialogBase::doExec(HWND owner)
@@ -1520,8 +1523,10 @@ QList<QUrl> QWindowsNativeSaveFileDialog::selectedFiles() const
     QList<QUrl> result;
     IShellItem *item = 0;
     const HRESULT hr = fileDialog()->GetCurrentSelection(&item);
-    if (SUCCEEDED(hr) && item)
+    if (SUCCEEDED(hr) && item) {
         result.push_back(QUrl::fromLocalFile(QWindowsNativeSaveFileDialog::itemPath(item)));
+        item->Release();
+    }
     return result;
 }
 
diff --git a/src/printsupport/kernel/qprintengine_win.cpp b/src/printsupport/kernel/qprintengine_win.cpp
index 228607d7e3..dd2bf3a0a3 100644
--- a/src/printsupport/kernel/qprintengine_win.cpp
+++ b/src/printsupport/kernel/qprintengine_win.cpp
@@ -924,14 +924,14 @@ void QWin32PrintEnginePrivate::initialize()
     Q_ASSERT(hPrinter);
     Q_ASSERT(pInfo);
 
+    initHDC();
+
     if (devMode) {
         num_copies = devMode->dmCopies;
         devMode->dmCollate = DMCOLLATE_TRUE;
         updatePageLayout();
     }
 
-    initHDC();
-
 #if defined QT_DEBUG_DRAW || defined QT_DEBUG_METRICS
     qDebug("QWin32PrintEngine::initialize()");
     debugMetrics();
diff --git a/src/printsupport/kernel/qprintengine_win_p.h b/src/printsupport/kernel/qprintengine_win_p.h
index 32da184b08..b436f5c9b0 100644
--- a/src/printsupport/kernel/qprintengine_win_p.h
+++ b/src/printsupport/kernel/qprintengine_win_p.h
@@ -130,10 +130,14 @@ public:
         state(QPrinter::Idle),
         resolution(0),
         m_pageLayout(QPageLayout(QPageSize(QPageSize::A4), QPageLayout::Portrait, QMarginsF(0, 0, 0, 0))),
+        stretch_x(1), stretch_y(1), origin_x(0), origin_y(0),
+        dpi_x(96), dpi_y(96), dpi_display(96),
         num_copies(1),
         printToFile(false),
         reinit(false),
-        embed_fonts(true)
+        complex_xform(false), has_pen(false), has_brush(false), has_custom_paper_size(false),
+        embed_fonts(true),
+        txop(0 /* QTransform::TxNone */)
     {
     }
 
diff --git a/src/tools/uic/cpp/cppwriteinitialization.cpp b/src/tools/uic/cpp/cppwriteinitialization.cpp
index 714841d6cf..dfc7ee3a61 100644
--- a/src/tools/uic/cpp/cppwriteinitialization.cpp
+++ b/src/tools/uic/cpp/cppwriteinitialization.cpp
@@ -2311,7 +2311,7 @@ QString WriteInitialization::trCall(const QString &str, const QString &commentHi
         return QLatin1String("QString()");
 
     QString result;
-    const QString comment = commentHint.isEmpty() ? QString(QLatin1Char('0')) : fixString(commentHint, m_dindent);
+    const QString comment = commentHint.isEmpty() ? QString(QLatin1String("Q_NULLPTR")) : fixString(commentHint, m_dindent);
 
     if (m_option.translateFunction.isEmpty()) {
         if (m_option.idBased) {
diff --git a/src/widgets/styles/qstylesheetstyle.cpp b/src/widgets/styles/qstylesheetstyle.cpp
index 4cf77b7a1e..e8e99a4386 100644
--- a/src/widgets/styles/qstylesheetstyle.cpp
+++ b/src/widgets/styles/qstylesheetstyle.cpp
@@ -3818,6 +3818,13 @@ void QStyleSheetStyle::drawControl(ControlElement ce, const QStyleOption *opt, Q
                 ParentStyle::drawControl(ce, opt, p, w);
                 return;
             }
+            if (subRule.hasFont) {
+                const QFont oldFont = p->font();
+                p->setFont(subRule.font.resolve(p->font()));
+                baseStyle()->drawControl(ce, opt, p, w);
+                p->setFont(oldFont);
+                return;
+            }
         }
         break;
     case CE_HeaderSection:
@@ -4931,13 +4938,14 @@ QSize QStyleSheetStyle::sizeFromContents(ContentsType ct, const QStyleOption *op
     case CT_HeaderSection: {
             if (const QStyleOptionHeader *hdr = qstyleoption_cast<const QStyleOptionHeader *>(opt)) {
                 QRenderRule subRule = renderRule(w, opt, PseudoElement_HeaderViewSection);
-                if (subRule.hasGeometry() || subRule.hasBox() || !subRule.hasNativeBorder()) {
+                if (subRule.hasGeometry() || subRule.hasBox() || !subRule.hasNativeBorder() || subRule.hasFont) {
                     sz = subRule.adjustSize(csz);
                     if (!subRule.hasGeometry()) {
                         QSize nativeContentsSize;
                         bool nullIcon = hdr->icon.isNull();
                         int iconSize = nullIcon ? 0 : pixelMetric(QStyle::PM_SmallIconSize, hdr, w);
-                        QSize txt = hdr->fontMetrics.size(0, hdr->text);
+                        const QSize txt = subRule.hasFont ? QFontMetrics(subRule.font).size(0, hdr->text)
+                                                          : hdr->fontMetrics.size(0, hdr->text);
                         nativeContentsSize.setHeight(qMax(iconSize, txt.height()));
                         nativeContentsSize.setWidth(iconSize + txt.width());
                         sz = sz.expandedTo(nativeContentsSize);
diff --git a/src/widgets/widgets/qdockarealayout.cpp b/src/widgets/widgets/qdockarealayout.cpp
index fd155bf156..50be36ae93 100644
--- a/src/widgets/widgets/qdockarealayout.cpp
+++ b/src/widgets/widgets/qdockarealayout.cpp
@@ -2610,6 +2610,21 @@ void QDockAreaLayout::remove(const QList<int> &path)
     docks[index].remove(path.mid(1));
 }
 
+void QDockAreaLayout::removePlaceHolder(const QString &name)
+{
+    QList<int> index = indexOfPlaceHolder(name);
+    if (!index.isEmpty())
+        remove(index);
+    foreach (QDockWidgetGroupWindow *dwgw, mainWindow->findChildren<QDockWidgetGroupWindow *>(
+                                               QString(), Qt::FindDirectChildrenOnly)) {
+        index = dwgw->layoutInfo()->indexOfPlaceHolder(name);
+        if (!index.isEmpty()) {
+            dwgw->layoutInfo()->remove(index);
+            dwgw->destroyOrHideIfEmpty();
+        }
+    }
+}
+
 static inline int qMax(int i1, int i2, int i3) { return qMax(i1, qMax(i2, i3)); }
 
 void QDockAreaLayout::getGrid(QVector<QLayoutStruct> *_ver_struct_list,
@@ -3036,15 +3051,27 @@ QRect QDockAreaLayout::constrainedRect(QRect rect, QWidget* widget)
 
 bool QDockAreaLayout::restoreDockWidget(QDockWidget *dockWidget)
 {
-    QList<int> index = indexOfPlaceHolder(dockWidget->objectName());
-    if (index.isEmpty())
-        return false;
+    QDockAreaLayoutItem *item = 0;
+    foreach (QDockWidgetGroupWindow *dwgw, mainWindow->findChildren<QDockWidgetGroupWindow *>(
+                                               QString(), Qt::FindDirectChildrenOnly)) {
+        QList<int> index = dwgw->layoutInfo()->indexOfPlaceHolder(dockWidget->objectName());
+        if (!index.isEmpty()) {
+            dockWidget->setParent(dwgw);
+            item = const_cast<QDockAreaLayoutItem *>(&dwgw->layoutInfo()->item(index));
+            break;
+        }
+    }
+    if (!item) {
+        QList<int> index = indexOfPlaceHolder(dockWidget->objectName());
+        if (index.isEmpty())
+            return false;
+        item = const_cast<QDockAreaLayoutItem *>(&this->item(index));
+    }
 
-    QDockAreaLayoutItem &item = this->item(index);
-    QPlaceHolderItem *placeHolder = item.placeHolderItem;
+    QPlaceHolderItem *placeHolder = item->placeHolderItem;
     Q_ASSERT(placeHolder != 0);
 
-    item.widgetItem = new QDockWidgetItem(dockWidget);
+    item->widgetItem = new QDockWidgetItem(dockWidget);
 
     if (placeHolder->window) {
         const QRect r = constrainedRect(placeHolder->topLevelRect, dockWidget);
@@ -3056,7 +3083,7 @@ bool QDockAreaLayout::restoreDockWidget(QDockWidget *dockWidget)
         dockWidget->d_func()->setWindowState(true);
 #endif
 
-    item.placeHolderItem = 0;
+    item->placeHolderItem = 0;
     delete placeHolder;
 
     return true;
@@ -3092,9 +3119,7 @@ void QDockAreaLayout::addDockWidget(QInternal::DockPosition pos, QDockWidget *do
         info = new_info;
     }
 
-    QList<int> index = indexOfPlaceHolder(dockWidget->objectName());
-    if (!index.isEmpty())
-        remove(index);
+    removePlaceHolder(dockWidget->objectName());
 }
 
 void QDockAreaLayout::tabifyDockWidget(QDockWidget *first, QDockWidget *second)
@@ -3107,9 +3132,7 @@ void QDockAreaLayout::tabifyDockWidget(QDockWidget *first, QDockWidget *second)
     Q_ASSERT(info != 0);
     info->tab(path.last(), new QDockWidgetItem(second));
 
-    QList<int> index = indexOfPlaceHolder(second->objectName());
-    if (!index.isEmpty())
-        remove(index);
+    removePlaceHolder(second->objectName());
 }
 
 void QDockAreaLayout::resizeDocks(const QList<QDockWidget *> &docks,
@@ -3171,9 +3194,7 @@ void QDockAreaLayout::splitDockWidget(QDockWidget *after,
     Q_ASSERT(info != 0);
     info->split(path.last(), orientation, new QDockWidgetItem(dockWidget));
 
-    QList<int> index = indexOfPlaceHolder(dockWidget->objectName());
-    if (!index.isEmpty())
-        remove(index);
+    removePlaceHolder(dockWidget->objectName());
 }
 
 void QDockAreaLayout::apply(bool animate)
diff --git a/src/widgets/widgets/qdockarealayout_p.h b/src/widgets/widgets/qdockarealayout_p.h
index 0ae1350394..bc9d418783 100644
--- a/src/widgets/widgets/qdockarealayout_p.h
+++ b/src/widgets/widgets/qdockarealayout_p.h
@@ -261,6 +261,7 @@ public:
     QLayoutItem *plug(const QList<int> &path);
     QLayoutItem *unplug(const QList<int> &path);
     void remove(const QList<int> &path);
+    void removePlaceHolder(const QString &name);
 
     void fitLayout();
 
diff --git a/src/widgets/widgets/qmainwindowlayout.cpp b/src/widgets/widgets/qmainwindowlayout.cpp
index b2c7225e8a..b138c42ba2 100644
--- a/src/widgets/widgets/qmainwindowlayout.cpp
+++ b/src/widgets/widgets/qmainwindowlayout.cpp
@@ -221,11 +221,10 @@ public:
     }
     void setGeometry(const QRect&r) Q_DECL_OVERRIDE
     {
+        static_cast<QDockWidgetGroupWindow *>(parent())->destroyOrHideIfEmpty();
         QDockAreaLayoutInfo *li = layoutInfo();
-        if (li->isEmpty()) {
-            static_cast<QDockWidgetGroupWindow *>(parent())->destroyIfEmpty();
+        if (li->isEmpty())
             return;
-        }
         int fw = frameWidth();
         li->reparentWidgets(parentWidget());
         li->rect = r.adjusted(fw, fw, -fw, -fw);
@@ -278,6 +277,10 @@ bool QDockWidgetGroupWindow::event(QEvent *e)
         if (qobject_cast<QDockWidget *>(static_cast<QChildEvent*>(e)->child()))
             adjustFlags();
         break;
+    case QEvent::LayoutRequest:
+        // We might need to show the widget again
+        destroyOrHideIfEmpty();
+        break;
     default:
         break;
     }
@@ -331,34 +334,43 @@ QDockWidget *QDockWidgetGroupWindow::topDockWidget() const
 }
 
 /*! \internal
-    Destroy this window if there is no more QDockWidget in it.
+    Destroy or hide this window if there is no more QDockWidget in it.
+    Otherwise make sure it is shown.
  */
-void QDockWidgetGroupWindow::destroyIfEmpty()
-{
-    if (layoutInfo()->isEmpty()) {
-        // Make sure to reparent the possibly floating or hidden QDockWidgets to the parent
-        foreach (QDockWidget *dw,
-                 findChildren<QDockWidget *>(QString(), Qt::FindDirectChildrenOnly)) {
-            bool wasFloating = dw->isFloating();
-            bool wasHidden = dw->isHidden();
-            dw->setParent(parentWidget());
-            if (wasFloating) {
-                dw->setFloating(true);
-            } else {
-                // maybe it was hidden, we still have to put it back in the main layout.
-                QMainWindowLayout *ml = qt_mainwindow_layout(static_cast<QMainWindow*>(parentWidget()));
-                Qt::DockWidgetArea area = ml->dockWidgetArea(this);
-                if (area == Qt::NoDockWidgetArea)
-                    area = Qt::LeftDockWidgetArea;
-                static_cast<QMainWindow*>(parentWidget())->addDockWidget(area, dw);
-            }
-            if (!wasHidden)
-                dw->show();
+void QDockWidgetGroupWindow::destroyOrHideIfEmpty()
+{
+    if (!layoutInfo()->isEmpty()) {
+        show(); // It might have been hidden,
+        return;
+    }
+    // There might still be placeholders
+    if (!layoutInfo()->item_list.isEmpty()) {
+        hide();
+        return;
+    }
+
+    // Make sure to reparent the possibly floating or hidden QDockWidgets to the parent
+    foreach (QDockWidget *dw, findChildren<QDockWidget *>(QString(), Qt::FindDirectChildrenOnly)) {
+        bool wasFloating = dw->isFloating();
+        bool wasHidden = dw->isHidden();
+        dw->setParent(parentWidget());
+        if (wasFloating) {
+            dw->setFloating(true);
+        } else {
+            // maybe it was hidden, we still have to put it back in the main layout.
+            QMainWindowLayout *ml =
+                qt_mainwindow_layout(static_cast<QMainWindow *>(parentWidget()));
+            Qt::DockWidgetArea area = ml->dockWidgetArea(this);
+            if (area == Qt::NoDockWidgetArea)
+                area = Qt::LeftDockWidgetArea;
+            static_cast<QMainWindow *>(parentWidget())->addDockWidget(area, dw);
         }
-        foreach (QTabBar *tb, findChildren<QTabBar *>(QString(), Qt::FindDirectChildrenOnly))
-            tb->setParent(parentWidget());
-        deleteLater();
+        if (!wasHidden)
+            dw->show();
     }
+    foreach (QTabBar *tb, findChildren<QTabBar *>(QString(), Qt::FindDirectChildrenOnly))
+        tb->setParent(parentWidget());
+    deleteLater();
 }
 
 /*! \internal
@@ -2089,7 +2101,7 @@ void QMainWindowLayout::animationFinished(QWidget *widget)
                 item.subinfo->reparentWidgets(parentWidget());
                 item.subinfo->setTabBarShape(parentInfo->tabBarShape);
             }
-            dwgw->destroyIfEmpty();
+            dwgw->destroyOrHideIfEmpty();
         }
 
         if (QDockWidget *dw = qobject_cast<QDockWidget*>(widget)) {
diff --git a/src/widgets/widgets/qmainwindowlayout_p.h b/src/widgets/widgets/qmainwindowlayout_p.h
index 4c61374d83..4f2e8078d3 100644
--- a/src/widgets/widgets/qmainwindowlayout_p.h
+++ b/src/widgets/widgets/qmainwindowlayout_p.h
@@ -80,7 +80,7 @@ public:
         : QWidget(parent, f) {}
     QDockAreaLayoutInfo *layoutInfo() const;
     QDockWidget *topDockWidget() const;
-    void destroyIfEmpty();
+    void destroyOrHideIfEmpty();
     void adjustFlags();
 protected:
     bool event(QEvent *) Q_DECL_OVERRIDE;