1 files changed, 20 insertions, 32 deletions

diff --git a/src/widgets/widgets/qmenubar.cpp b/src/widgets/widgets/qmenubar.cpp
index 99fddee53d..a77c0f9753 100644
--- a/src/widgets/widgets/qmenubar.cpp
+++ b/src/widgets/widgets/qmenubar.cpp
@@ -612,9 +612,10 @@ void QMenuBar::initStyleOption(QStyleOptionMenuItem *option, const QAction *acti
     for items in the menu bar are only shown when the \uicontrol{Alt} key is
     pressed.
 
-    \section1 QMenuBar on \macos
+    \section1 QMenuBar as a Global Menu Bar
 
-    QMenuBar on \macos is a wrapper for using the system-wide menu bar.
+    On \macos and on certain Linux desktop environments such as
+    Ubuntu Unity, QMenuBar is a wrapper for using the system-wide menu bar.
     If you have multiple menu bars in one dialog the outermost menu bar
     (normally inside a widget with widget flag Qt::Window) will
     be used for the system-wide menu bar.
@@ -657,11 +658,16 @@ void QMenuBar::initStyleOption(QStyleOptionMenuItem *option, const QAction *acti
     as its parent. That menu bar would only be displayed for the
     parent QMainWindow.
 
-    \b{Note:} The text used for the application name in the menu
+    \b{Note:} The text used for the application name in the \macos menu
     bar is obtained from the value set in the \c{Info.plist} file in
     the application's bundle. See \l{Qt for macOS - Deployment}
     for more information.
 
+    \b{Note:} On Linux, if the com.canonical.AppMenu.Registrar
+    service is available on the D-Bus session bus, then Qt will
+    communicate with it to install the application's menus into the
+    global menu bar, as described.
+
     \section1 Examples
 
     The \l{mainwindows/menus}{Menus} example shows how to use QMenuBar
@@ -985,13 +991,11 @@ void QMenuBar::paintEvent(QPaintEvent *e)
 */
 void QMenuBar::setVisible(bool visible)
 {
-#if defined(Q_OS_DARWIN)
     if (isNativeMenuBar()) {
         if (!visible)
             QWidget::setVisible(false);
         return;
     }
-#endif
     QWidget::setVisible(visible);
 }
 
@@ -1534,11 +1538,7 @@ QRect QMenuBar::actionGeometry(QAction *act) const
 QSize QMenuBar::minimumSizeHint() const
 {
     Q_D(const QMenuBar);
-#if defined(Q_OS_DARWIN)
     const bool as_gui_menubar = !isNativeMenuBar();
-#else
-    const bool as_gui_menubar = true;
-#endif
 
     ensurePolished();
     QSize ret(0, 0);
@@ -1590,12 +1590,7 @@ QSize QMenuBar::minimumSizeHint() const
 QSize QMenuBar::sizeHint() const
 {
     Q_D(const QMenuBar);
-#if defined(Q_OS_DARWIN)
     const bool as_gui_menubar = !isNativeMenuBar();
-#else
-    const bool as_gui_menubar = true;
-#endif
-
 
     ensurePolished();
     QSize ret(0, 0);
@@ -1648,11 +1643,7 @@ QSize QMenuBar::sizeHint() const
 int QMenuBar::heightForWidth(int) const
 {
     Q_D(const QMenuBar);
-#if defined(Q_OS_DARWIN)
     const bool as_gui_menubar = !isNativeMenuBar();
-#else
-    const bool as_gui_menubar = true;
-#endif
 
     const_cast<QMenuBarPrivate*>(d)->updateGeometries();
     int height = 0;
@@ -1783,23 +1774,23 @@ QWidget *QMenuBar::cornerWidget(Qt::Corner corner) const
     \brief Whether or not a menubar will be used as a native menubar on platforms that support it
     \since 4.6
 
-    This property specifies whether or not the menubar should be used as a native menubar on \macos.
+    This property specifies whether or not the menubar should be used as a native menubar on
+    platforms that support it. The currently supported platforms are \macos, and
+    Linux desktops which use the com.canonical.dbusmenu D-Bus interface (such as Ubuntu Unity).
     If this property is \c true, the menubar is used in the native menubar and is not in the window of
-    its parent, if \c false the menubar remains in the window. On other platforms the value of this
-    attribute has no effect.
+    its parent; if \c false the menubar remains in the window. On other platforms,
+    setting this attribute has no effect, and reading this attribute will always return \c false.
 
     The default is to follow whether the Qt::AA_DontUseNativeMenuBar attribute
-    is set for the application. Explicitly settings this property overrides
-    the presence (or abscence) of the attribute.
+    is set for the application. Explicitly setting this property overrides
+    the presence (or absence) of the attribute.
 */
 
 void QMenuBar::setNativeMenuBar(bool nativeMenuBar)
 {
     Q_D(QMenuBar);
-    if (d->nativeMenuBar == -1 || (nativeMenuBar != bool(d->nativeMenuBar))) {
-        d->nativeMenuBar = nativeMenuBar;
-
-        if (!d->nativeMenuBar) {
+    if (nativeMenuBar != bool(d->platformMenuBar)) {
+        if (!nativeMenuBar) {
             delete d->platformMenuBar;
             d->platformMenuBar = 0;
         } else {
@@ -1808,7 +1799,7 @@ void QMenuBar::setNativeMenuBar(bool nativeMenuBar)
         }
 
         updateGeometry();
-        if (!d->nativeMenuBar && parentWidget())
+        if (!nativeMenuBar && parentWidget())
             setVisible(true);
     }
 }
@@ -1816,10 +1807,7 @@ void QMenuBar::setNativeMenuBar(bool nativeMenuBar)
 bool QMenuBar::isNativeMenuBar() const
 {
     Q_D(const QMenuBar);
-    if (d->nativeMenuBar == -1) {
-        return !QApplication::instance()->testAttribute(Qt::AA_DontUseNativeMenuBar);
-    }
-    return d->nativeMenuBar;
+    return bool(d->platformMenuBar);
 }
 
 /*!