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, 2 insertions, 1 deletions

diff --git a/src/widgets/widgets/qdockwidget_p.h b/src/widgets/widgets/qdockwidget_p.h
index 752d6519e5..9c68bc5fb1 100644
--- a/src/widgets/widgets/qdockwidget_p.h
+++ b/src/widgets/widgets/qdockwidget_p.h
@@ -108,7 +108,7 @@ public:
     void setWindowState(bool floating, bool unplug = false, const QRect &rect = QRect());
     void nonClientAreaMouseEvent(QMouseEvent *event);
     void initDrag(const QPoint &pos, bool nca);
-    void startDrag();
+    void startDrag(bool group = true);
     void endDrag(bool abort = false);
     void moveEvent(QMoveEvent *event);
 
@@ -151,6 +151,7 @@ public:
     int minimumTitleWidth() const;
     int titleHeight() const;
     void updateMaxSize();
+    static bool wmSupportsNativeWindowDeco();
     bool nativeWindowDeco() const;
     bool nativeWindowDeco(bool floating) const;