Add QMainWindow::GroupedDragging DockOption

If this setting is enabled, the entire group of docked tabs will
be draggable by the title bar of the group and and individual dock
can be dragged by dragging the tab.

When tabs are detached, the docks that are contained are reparented to
a QDockWidgetGroupWindow.

[ChangeLog][QtWidgets][QMainWindow] Added GroupedDragging as a DockOption
which allow users to drag all the tabs together when dragging the
title of a QDockWidget which is tabbed with others.

Change-Id: I5285685b129770498eb3e4fd5f4556e41225a595
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@theqtcompany.com>
Reviewed-by: Paul Olav Tvete <paul.tvete@theqtcompany.com>

1 files changed, 110 insertions, 43 deletions

diff --git a/src/widgets/widgets/qdockwidget.cpp b/src/widgets/widgets/qdockwidget.cpp
index 21b0904cc0..1b7473fbd7 100644
--- a/src/widgets/widgets/qdockwidget.cpp
+++ b/src/widgets/widgets/qdockwidget.cpp
@@ -65,6 +65,18 @@ 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)
+{
+    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();
+    }
+    return Q_NULLPTR;
+}
+
 static inline bool hasFeature(const QDockWidgetPrivate *priv, QDockWidget::DockWidgetFeature feature)
 { return (priv->features & feature) == feature; }
 
@@ -194,25 +206,40 @@ QDockWidgetLayout::~QDockWidgetLayout()
     qDeleteAll(item_list);
 }
 
+/*! \internal
+    Returns true if the dock widget managed by this layout should have a native
+    window decoration or if Qt needs to draw it.
+ */
 bool QDockWidgetLayout::nativeWindowDeco() const
 {
-    return nativeWindowDeco(parentWidget()->isWindow());
+    bool floating = parentWidget()->isWindow();
+    if (!floating && qobject_cast<QDockWidgetGroupWindow*>(parentWidget()->parentWidget()))
+        return wmSupportsNativeWindowDeco();
+    return nativeWindowDeco(floating);
 }
 
-static bool isXcb()
+/*! \internal
+    Returns true if the window manager can draw natively the windows decoration
+    of a dock widget
+ */
+bool QDockWidgetLayout::wmSupportsNativeWindowDeco()
 {
+#if defined(Q_OS_WINCE) || defined(Q_OS_ANDROID)
+    return false;
+#else
     static const bool xcb = !QGuiApplication::platformName().compare(QLatin1String("xcb"), Qt::CaseInsensitive);
-    return xcb;
+    return !xcb;
+#endif
 }
 
+/*! \internal
+   Returns true if the dock widget managed by this layout should have a native
+   window decoration or if Qt needs to draw it. The \a floating parameter
+   overrides the floating current state of the dock widget.
+ */
 bool QDockWidgetLayout::nativeWindowDeco(bool floating) const
 {
-#if defined(Q_OS_WINCE) || defined(Q_OS_ANDROID)
-    Q_UNUSED(floating)
-    return false;
-#else
-    return !isXcb() && (floating && item_list[QDockWidgetLayout::TitleBar] == 0);
-#endif
+    return wmSupportsNativeWindowDeco() && floating && item_list.at(QDockWidgetLayout::TitleBar) == 0;
 }
 
 
@@ -611,7 +638,10 @@ void QDockWidget::initStyleOption(QStyleOptionDockWidget *option) const
         return;
     QDockWidgetLayout *dwlayout = qobject_cast<QDockWidgetLayout*>(layout());
 
-    option->initFrom(this);
+    QDockWidgetGroupWindow *floatingTab = qobject_cast<QDockWidgetGroupWindow*>(parent());
+    // If we are in a floating tab, init from the parent because the attributes and the geometry
+    // of the title bar should be taken from the floating window.
+    option->initFrom(floatingTab && !isFloating() ? parentWidget() : this);
     option->rect = dwlayout->titleArea();
     option->title = d->fixedWindowTitle;
     option->closable = hasFeature(this, QDockWidget::DockWidgetClosable);
@@ -681,14 +711,20 @@ void QDockWidgetPrivate::_q_toggleTopLevel()
     q->setFloating(!q->isFloating());
 }
 
+/*! \internal
+    Initialize the drag state structure and remember the position of the click.
+    This is called when the mouse is pressed, but the dock is not yet dragged out.
+
+    \a nca specify that the event comes from NonClientAreaMouseButtonPress
+ */
 void QDockWidgetPrivate::initDrag(const QPoint &pos, bool nca)
 {
+    Q_Q(QDockWidget);
+
     if (state != 0)
         return;
 
-    QMainWindow *win = qobject_cast<QMainWindow*>(parent);
-    Q_ASSERT(win != 0);
-    QMainWindowLayout *layout = qt_mainwindow_layout(win);
+    QMainWindowLayout *layout = qt_mainwindow_layout_from_dock(q);
     Q_ASSERT(layout != 0);
     if (layout->pluggingWidget != 0) // the main window is animating a docking operation
         return;
@@ -702,17 +738,23 @@ void QDockWidgetPrivate::initDrag(const QPoint &pos, bool nca)
     state->ctrlDrag = false;
 }
 
-void QDockWidgetPrivate::startDrag()
+/*! \internal
+    Actually start the drag and detach the dockwidget.
+    The \a group parameter is true when we should potentially drag a group of
+    tabbed widgets, and false if the dock widget should always be dragged
+    alone.
+ */
+void QDockWidgetPrivate::startDrag(bool group)
 {
     Q_Q(QDockWidget);
 
     if (state == 0 || state->dragging)
         return;
 
-    QMainWindowLayout *layout = qt_mainwindow_layout(qobject_cast<QMainWindow *>(q->parentWidget()));
+    QMainWindowLayout *layout = qt_mainwindow_layout_from_dock(q);
     Q_ASSERT(layout != 0);
 
-    state->widgetItem = layout->unplug(q);
+    state->widgetItem = layout->unplug(q, group);
     if (state->widgetItem == 0) {
         /* I have a QMainWindow parent, but I was never inserted with
             QMainWindow::addDockWidget, so the QMainWindowLayout has no
@@ -728,6 +770,11 @@ void QDockWidgetPrivate::startDrag()
     state->dragging = true;
 }
 
+/*! \internal
+    Ends the drag end drop operation of the QDockWidget.
+    The \a abort parameter specifies that it ends because of programmatic state
+    reset rather than mouse release event.
+ */
 void QDockWidgetPrivate::endDrag(bool abort)
 {
     Q_Q(QDockWidget);
@@ -736,29 +783,31 @@ void QDockWidgetPrivate::endDrag(bool abort)
     q->releaseMouse();
 
     if (state->dragging) {
-        QMainWindowLayout *mwLayout = qt_mainwindow_layout(qobject_cast<QMainWindow *>(q->parentWidget()));
+        QMainWindowLayout *mwLayout = qt_mainwindow_layout_from_dock(q);
         Q_ASSERT(mwLayout != 0);
 
         if (abort || !mwLayout->plug(state->widgetItem)) {
             if (hasFeature(this, QDockWidget::DockWidgetFloatable)) {
+                // This QDockWidget will now stay in the floating state.
                 if (state->ownWidgetItem)
                     delete state->widgetItem;
                 mwLayout->restore();
-                if (isXcb()) {
+                QDockWidgetLayout *dwLayout = qobject_cast<QDockWidgetLayout*>(layout);
+                if (!dwLayout->nativeWindowDeco()) {
                     // get rid of the X11BypassWindowManager window flag and activate the resizer
                     Qt::WindowFlags flags = q->windowFlags();
                     flags &= ~Qt::X11BypassWindowManagerHint;
                     q->setWindowFlags(flags);
-                    setResizerActive(true);
+                    setResizerActive(q->isFloating());
                     q->show();
                 } else {
-                    QDockWidgetLayout *myLayout
-                            = qobject_cast<QDockWidgetLayout*>(layout);
-                    setResizerActive(myLayout->widgetForRole(QDockWidgetLayout::TitleBar) != 0);
+                    setResizerActive(false);
                 }
                 undockedGeometry = q->geometry();
                 q->activateWindow();
             } else {
+                // The tab was not plugged back in the QMainWindow but the QDockWidget cannot
+                // stay floating, revert to the previous state.
                 mwLayout->revert(state->widgetItem);
             }
         }
@@ -782,11 +831,7 @@ bool QDockWidgetPrivate::isAnimating() const
 {
     Q_Q(const QDockWidget);
 
-    QMainWindow *mainWin = qobject_cast<QMainWindow*>(parent);
-    if (mainWin == 0)
-        return false;
-
-    QMainWindowLayout *mainWinLayout = qt_mainwindow_layout(mainWin);
+    QMainWindowLayout *mainWinLayout = qt_mainwindow_layout_from_dock(q);
     if (mainWinLayout == 0)
         return false;
 
@@ -804,12 +849,14 @@ bool QDockWidgetPrivate::mousePressEvent(QMouseEvent *event)
     if (!dwLayout->nativeWindowDeco()) {
         QRect titleArea = dwLayout->titleArea();
 
+        QDockWidgetGroupWindow *floatingTab = qobject_cast<QDockWidgetGroupWindow*>(parent);
+
         if (event->button() != Qt::LeftButton ||
             !titleArea.contains(event->pos()) ||
             // check if the tool window is movable... do nothing if it
             // is not (but allow moving if the window is floating)
             (!hasFeature(this, QDockWidget::DockWidgetMovable) && !q->isFloating()) ||
-            qobject_cast<QMainWindow*>(parent) == 0 ||
+            (qobject_cast<QMainWindow*>(parent) == 0 && !floatingTab) ||
             isAnimating() || state != 0) {
             return false;
         }
@@ -853,7 +900,7 @@ bool QDockWidgetPrivate::mouseMoveEvent(QMouseEvent *event)
 
     QDockWidgetLayout *dwlayout
         = qobject_cast<QDockWidgetLayout *>(layout);
-    QMainWindowLayout *mwlayout = qt_mainwindow_layout(qobject_cast<QMainWindow *>(q->parentWidget()));
+    QMainWindowLayout *mwlayout = qt_mainwindow_layout_from_dock(q);
     if (!dwlayout->nativeWindowDeco()) {
         if (!state->dragging
             && mwlayout->pluggingWidget == 0
@@ -871,7 +918,12 @@ bool QDockWidgetPrivate::mouseMoveEvent(QMouseEvent *event)
 
     if (state->dragging && !state->nca) {
         QPoint pos = event->globalPos() - state->pressPos;
-        q->move(pos);
+
+        QDockWidgetGroupWindow *floatingTab = qobject_cast<QDockWidgetGroupWindow*>(parent);
+        if (floatingTab && !q->isFloating())
+            floatingTab->move(pos);
+        else
+            q->move(pos);
 
         if (state && !state->ctrlDrag)
             mwlayout->hover(state->widgetItem, event->globalPos());
@@ -902,8 +954,9 @@ void QDockWidgetPrivate::nonClientAreaMouseEvent(QMouseEvent *event)
 
     int fw = q->style()->pixelMetric(QStyle::PM_DockWidgetFrameWidth, 0, q);
 
-    QRect geo = q->geometry();
-    QRect titleRect = q->frameGeometry();
+    QWidget *tl = q->topLevelWidget();
+    QRect geo = tl->geometry();
+    QRect titleRect = tl->frameGeometry();
 #ifdef Q_DEAD_CODE_FROM_QT4_MAC
     if ((features & QDockWidget::DockWidgetVerticalTitleBar)) {
         titleRect.setTop(geo.top());
@@ -924,7 +977,7 @@ void QDockWidgetPrivate::nonClientAreaMouseEvent(QMouseEvent *event)
                 break;
             if (state != 0)
                 break;
-            if (qobject_cast<QMainWindow*>(parent) == 0)
+            if (qobject_cast<QMainWindow*>(parent) == 0 && qobject_cast<QDockWidgetGroupWindow*>(parent) == 0)
                 break;
             if (isAnimating())
                 break;
@@ -958,11 +1011,17 @@ void QDockWidgetPrivate::nonClientAreaMouseEvent(QMouseEvent *event)
     }
 }
 
+/*! \internal
+    Called when the QDockWidget or the QDockWidgetGroupWindow is moved
+ */
 void QDockWidgetPrivate::moveEvent(QMoveEvent *event)
 {
     Q_Q(QDockWidget);
 
-    if (state == 0 || !state->dragging || !state->nca || !q->isWindow())
+    if (state == 0 || !state->dragging || !state->nca)
+        return;
+
+    if (!q->isWindow() && qobject_cast<QDockWidgetGroupWindow*>(parent) == 0)
         return;
 
     // When the native window frame is being dragged, all we get is these mouse
@@ -971,7 +1030,7 @@ void QDockWidgetPrivate::moveEvent(QMoveEvent *event)
     if (state->ctrlDrag)
         return;
 
-    QMainWindowLayout *layout = qt_mainwindow_layout(qobject_cast<QMainWindow *>(q->parentWidget()));
+    QMainWindowLayout *layout = qt_mainwindow_layout_from_dock(q);
     Q_ASSERT(layout != 0);
 
     QPoint globalMousePos = event->pos() + state->pressPos;
@@ -999,8 +1058,9 @@ void QDockWidgetPrivate::setWindowState(bool floating, bool unplug, const QRect
     Q_Q(QDockWidget);
 
     if (!floating && parent) {
-        QMainWindowLayout *mwlayout = qt_mainwindow_layout(qobject_cast<QMainWindow *>(q->parentWidget()));
-        if (mwlayout && mwlayout->dockWidgetArea(q) == Qt::NoDockWidgetArea)
+        QMainWindowLayout *mwlayout = qt_mainwindow_layout_from_dock(q);
+        if (mwlayout && mwlayout->dockWidgetArea(q) == Qt::NoDockWidgetArea
+                && !qobject_cast<QDockWidgetGroupWindow *>(parent))
             return; // this dockwidget can't be redocked
     }
 
@@ -1048,7 +1108,7 @@ void QDockWidgetPrivate::setWindowState(bool floating, bool unplug, const QRect
     if (floating != wasFloating) {
         emit q->topLevelChanged(floating);
         if (!floating && parent) {
-            QMainWindowLayout *mwlayout = qt_mainwindow_layout(qobject_cast<QMainWindow *>(q->parentWidget()));
+            QMainWindowLayout *mwlayout = qt_mainwindow_layout_from_dock(q);
             if (mwlayout)
                 emit q->dockLocationChanged(mwlayout->dockWidgetArea(q));
         }
@@ -1230,8 +1290,11 @@ void QDockWidget::setFeatures(QDockWidget::DockWidgetFeatures features)
     emit featuresChanged(d->features);
     update();
     if (closableChanged && layout->nativeWindowDeco()) {
-        //this ensures the native decoration is drawn
-        d->setWindowState(true /*floating*/, true /*unplug*/);
+        QDockWidgetGroupWindow *floatingTab = qobject_cast<QDockWidgetGroupWindow *>(parent());
+        if (floatingTab && !isFloating())
+            floatingTab->adjustFlags();
+        else
+            d->setWindowState(true /*floating*/, true /*unplug*/);  //this ensures the native decoration is drawn
     }
 }
 
@@ -1323,11 +1386,12 @@ void QDockWidget::changeEvent(QEvent *event)
 #endif
 #ifndef QT_NO_TABBAR
         {
-            QMainWindow *win = qobject_cast<QMainWindow*>(parentWidget());
-            if (QMainWindowLayout *winLayout = qt_mainwindow_layout(win)) {
+            if (QMainWindowLayout *winLayout = qt_mainwindow_layout_from_dock(this)) {
                 if (QDockAreaLayoutInfo *info = winLayout->layoutState.dockAreaLayout.info(this))
                     info->updateTabBar();
             }
+            if (QDockWidgetGroupWindow *p = qobject_cast<QDockWidgetGroupWindow *>(parent()))
+                p->adjustFlags();
         }
 #endif // QT_NO_TABBAR
         break;
@@ -1380,7 +1444,7 @@ bool QDockWidget::event(QEvent *event)
     Q_D(QDockWidget);
 
     QMainWindow *win = qobject_cast<QMainWindow*>(parentWidget());
-    QMainWindowLayout *layout = qt_mainwindow_layout(win);
+    QMainWindowLayout *layout = qt_mainwindow_layout_from_dock(this);
 
     switch (event->type()) {
 #ifndef QT_NO_ACTION
@@ -1417,6 +1481,9 @@ bool QDockWidget::event(QEvent *event)
         }
         if (!isFloating() && layout != 0 && onTop)
             layout->raise(this);
+        if (QDockWidgetGroupWindow *p = qobject_cast<QDockWidgetGroupWindow *>(parent()))
+            p->adjustFlags();
+
         break;
     }
     case QEvent::WindowActivate: