Add support for cascading sub-menus

This commit adds initial support for cascading sub-menus by allowing
one to nest declarative Menu declarations. A follow-up commit adds
support for adding, inserting, and removing menus programmatically.

[ChangeLog][Controls][Menu] Added support for cascading sub-menus.

Task-number: QTBUG-60351
Change-Id: I0eee4f74d92a97c09333fcc4348b019782448535
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>

24 files changed, 473 insertions, 38 deletions

diff --git a/src/imports/controls/Menu.qml b/src/imports/controls/Menu.qml
index 31c9230a..1fbf9a92 100644
--- a/src/imports/controls/Menu.qml
+++ b/src/imports/controls/Menu.qml
@@ -48,6 +48,7 @@ T.Menu {
                              contentItem ? contentItem.implicitHeight : 0) + topPadding + bottomPadding
 
     margins: 0
+    overlap: 1
 
     delegate: MenuItem { }
 
diff --git a/src/imports/controls/MenuItem.qml b/src/imports/controls/MenuItem.qml
index 97c3f965..e0532719 100644
--- a/src/imports/controls/MenuItem.qml
+++ b/src/imports/controls/MenuItem.qml
@@ -57,8 +57,10 @@ T.MenuItem {
     icon.color: enabled ? Default.textDarkColor : Default.textDisabledColor
 
     contentItem: IconLabel {
-        leftPadding: control.checkable && !control.mirrored ? control.indicator.width + control.spacing : 0
-        rightPadding: control.checkable && control.mirrored ? control.indicator.width + control.spacing : 0
+        readonly property real arrowPadding: control.subMenu && control.arrow ? control.arrow.width + control.spacing : 0
+        readonly property real indicatorPadding: control.checkable && control.indicator ? control.indicator.width + control.spacing : 0
+        leftPadding: !control.mirrored ? indicatorPadding : arrowPadding
+        rightPadding: control.mirrored ? indicatorPadding : arrowPadding
 
         spacing: control.spacing
         mirrored: control.mirrored
@@ -79,6 +81,15 @@ T.MenuItem {
         source: control.checkable ? "qrc:/qt-project.org/imports/QtQuick/Controls.2/images/check.png" : ""
     }
 
+    arrow: Image {
+        x: control.mirrored ? control.leftPadding : control.width - width - control.rightPadding
+        y: control.topPadding + (control.availableHeight - height) / 2
+
+        visible: control.subMenu
+        mirror: control.mirrored
+        source: control.subMenu ? "qrc:/qt-project.org/imports/QtQuick/Controls.2/images/arrow-indicator.png" : ""
+    }
+
     background: Item {
         implicitWidth: 200
         implicitHeight: 40
diff --git a/src/imports/controls/fusion/Menu.qml b/src/imports/controls/fusion/Menu.qml
index 3fd4caa2..d7fceb92 100644
--- a/src/imports/controls/fusion/Menu.qml
+++ b/src/imports/controls/fusion/Menu.qml
@@ -51,6 +51,7 @@ T.Menu {
 
     margins: 0
     padding: 1
+    overlap: 2
 
     delegate: MenuItem { }
 
diff --git a/src/imports/controls/fusion/MenuItem.qml b/src/imports/controls/fusion/MenuItem.qml
index c0127ed7..ca828c40 100644
--- a/src/imports/controls/fusion/MenuItem.qml
+++ b/src/imports/controls/fusion/MenuItem.qml
@@ -58,8 +58,10 @@ T.MenuItem {
     icon.height: 16
 
     contentItem: IconLabel {
-        leftPadding: !control.mirrored ? control.indicator.width + control.spacing : 0
-        rightPadding: control.mirrored ? control.indicator.width + control.spacing : 0
+        readonly property real arrowPadding: control.subMenu && control.arrow ? control.arrow.width + control.spacing : 0
+        readonly property real indicatorPadding: control.checkable && control.indicator ? control.indicator.width + control.spacing : 0
+        leftPadding: !control.mirrored ? indicatorPadding : arrowPadding
+        rightPadding: control.mirrored ? indicatorPadding : arrowPadding
 
         spacing: control.spacing
         mirrored: control.mirrored
@@ -72,6 +74,18 @@ T.MenuItem {
         color: control.down || control.highlighted ? Fusion.highlightedText(control.palette) : control.palette.text
     }
 
+    arrow: ColorImage {
+        x: control.mirrored ? control.padding : control.width - width - control.padding
+        y: control.topPadding + (control.availableHeight - height) / 2
+        width: 20
+
+        visible: control.subMenu
+        rotation: control.mirrored ? 90 : -90
+        color: control.down || control.hovered || control.highlighted ? Fusion.highlightedText(control.palette) : control.palette.text
+        source: "qrc:/qt-project.org/imports/QtQuick/Controls.2/Fusion/images/arrow.png"
+        fillMode: Image.Pad
+    }
+
     indicator: CheckIndicator {
         x: control.mirrored ? control.width - width - control.rightPadding : control.leftPadding
         y: control.topPadding + (control.availableHeight - height) / 2
diff --git a/src/imports/controls/images/arrow-indicator.png b/src/imports/controls/images/arrow-indicator.png
new file mode 100644
index 00000000..50f230dc
--- /dev/null
+++ b/src/imports/controls/images/arrow-indicator.png
diff --git a/src/imports/controls/images/arrow-indicator@2x.png b/src/imports/controls/images/arrow-indicator@2x.png
new file mode 100644
index 00000000..457cdde0
--- /dev/null
+++ b/src/imports/controls/images/arrow-indicator@2x.png
diff --git a/src/imports/controls/images/arrow-indicator@3x.png b/src/imports/controls/images/arrow-indicator@3x.png
new file mode 100644
index 00000000..8d624154
--- /dev/null
+++ b/src/imports/controls/images/arrow-indicator@3x.png
diff --git a/src/imports/controls/images/arrow-indicator@4x.png b/src/imports/controls/images/arrow-indicator@4x.png
new file mode 100644
index 00000000..7d2c49e2
--- /dev/null
+++ b/src/imports/controls/images/arrow-indicator@4x.png
diff --git a/src/imports/controls/material/MenuItem.qml b/src/imports/controls/material/MenuItem.qml
index a5bf8a54..743f1e12 100644
--- a/src/imports/controls/material/MenuItem.qml
+++ b/src/imports/controls/material/MenuItem.qml
@@ -67,9 +67,21 @@ T.MenuItem {
         control: control
     }
 
+    arrow: ColorImage {
+        x: control.mirrored ? control.padding : control.width - width - control.padding
+        y: control.topPadding + (control.availableHeight - height) / 2
+
+        visible: control.subMenu
+        mirror: control.mirrored
+        color: control.enabled ? control.Material.foreground : control.Material.hintTextColor
+        source: "qrc:/qt-project.org/imports/QtQuick/Controls.2/Material/images/arrow-indicator.png"
+    }
+
     contentItem: IconLabel {
-        leftPadding: control.checkable && !control.mirrored ? control.indicator.width + control.spacing : 0
-        rightPadding: control.checkable && control.mirrored ? control.indicator.width + control.spacing : 0
+        readonly property real arrowPadding: control.subMenu && control.arrow ? control.arrow.width + control.spacing : 0
+        readonly property real indicatorPadding: control.checkable && control.indicator ? control.indicator.width + control.spacing : 0
+        leftPadding: !control.mirrored ? indicatorPadding : arrowPadding
+        rightPadding: control.mirrored ? indicatorPadding : arrowPadding
 
         spacing: control.spacing
         mirrored: control.mirrored
diff --git a/src/imports/controls/material/images/arrow-indicator.png b/src/imports/controls/material/images/arrow-indicator.png
new file mode 100644
index 00000000..4a942849
--- /dev/null
+++ b/src/imports/controls/material/images/arrow-indicator.png
diff --git a/src/imports/controls/material/images/arrow-indicator.svg b/src/imports/controls/material/images/arrow-indicator.svg
new file mode 100644
index 00000000..1e7217c8
--- /dev/null
+++ b/src/imports/controls/material/images/arrow-indicator.svg
@@ -0,0 +1,56 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<svg
+   xmlns:dc="http://purl.org/dc/elements/1.1/"
+   xmlns:cc="http://creativecommons.org/ns#"
+   xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
+   xmlns:svg="http://www.w3.org/2000/svg"
+   xmlns="http://www.w3.org/2000/svg"
+   xmlns:sodipodi="http://sodipodi.sourceforge.net/DTD/sodipodi-0.dtd"
+   xmlns:inkscape="http://www.inkscape.org/namespaces/inkscape"
+   width="5"
+   height="10"
+   viewBox="0 0 5 10"
+   version="1.1"
+   id="svg2"
+   inkscape:version="0.91 r13725"
+   sodipodi:docname="arrow-indicator.svg">
+  <metadata
+     id="metadata10">
+    <rdf:RDF>
+      <cc:Work
+         rdf:about="">
+        <dc:format>image/svg+xml</dc:format>
+        <dc:type
+           rdf:resource="http://purl.org/dc/dcmitype/StillImage" />
+        <dc:title></dc:title>
+      </cc:Work>
+    </rdf:RDF>
+  </metadata>
+  <defs
+     id="defs8" />
+  <sodipodi:namedview
+     pagecolor="#ffffff"
+     bordercolor="#666666"
+     borderopacity="1"
+     objecttolerance="10"
+     gridtolerance="10"
+     guidetolerance="10"
+     inkscape:pageopacity="0"
+     inkscape:pageshadow="2"
+     inkscape:window-width="2560"
+     inkscape:window-height="1571"
+     id="namedview6"
+     showgrid="false"
+     inkscape:zoom="27.812867"
+     inkscape:cx="13.137558"
+     inkscape:cy="12.83583"
+     inkscape:window-x="0"
+     inkscape:window-y="55"
+     inkscape:window-maximized="1"
+     inkscape:current-layer="svg2" />
+  <path
+     d="M 0,10 5,5 0,0 Z"
+     id="path4"
+     inkscape:connector-curvature="0"
+     style="fill:#757575" />
+</svg>
diff --git a/src/imports/controls/material/images/arrow-indicator@2x.png b/src/imports/controls/material/images/arrow-indicator@2x.png
new file mode 100644
index 00000000..b31b56c1
--- /dev/null
+++ b/src/imports/controls/material/images/arrow-indicator@2x.png
diff --git a/src/imports/controls/material/images/arrow-indicator@3x.png b/src/imports/controls/material/images/arrow-indicator@3x.png
new file mode 100644
index 00000000..637e9674
--- /dev/null
+++ b/src/imports/controls/material/images/arrow-indicator@3x.png
diff --git a/src/imports/controls/material/images/arrow-indicator@4x.png b/src/imports/controls/material/images/arrow-indicator@4x.png
new file mode 100644
index 00000000..15b9a902
--- /dev/null
+++ b/src/imports/controls/material/images/arrow-indicator@4x.png
diff --git a/src/imports/controls/material/qtquickcontrols2materialstyleplugin.qrc b/src/imports/controls/material/qtquickcontrols2materialstyleplugin.qrc
index e2cc90fa..6e29aea4 100644
--- a/src/imports/controls/material/qtquickcontrols2materialstyleplugin.qrc
+++ b/src/imports/controls/material/qtquickcontrols2materialstyleplugin.qrc
@@ -1,5 +1,9 @@
 <RCC>
     <qresource prefix="/qt-project.org/imports/QtQuick/Controls.2/Material">
+        <file>images/arrow-indicator.png</file>
+        <file>images/arrow-indicator@2x.png</file>
+        <file>images/arrow-indicator@3x.png</file>
+        <file>images/arrow-indicator@4x.png</file>
         <file>images/check.png</file>
         <file>images/check@2x.png</file>
         <file>images/check@3x.png</file>
diff --git a/src/imports/controls/qtquickcontrols2plugin.qrc b/src/imports/controls/qtquickcontrols2plugin.qrc
index 0948a529..c2dd9d39 100644
--- a/src/imports/controls/qtquickcontrols2plugin.qrc
+++ b/src/imports/controls/qtquickcontrols2plugin.qrc
@@ -1,5 +1,9 @@
 <RCC>
     <qresource prefix="/qt-project.org/imports/QtQuick/Controls.2">
+        <file>images/arrow-indicator.png</file>
+        <file>images/arrow-indicator@2x.png</file>
+        <file>images/arrow-indicator@3x.png</file>
+        <file>images/arrow-indicator@4x.png</file>
         <file>images/check.png</file>
         <file>images/check@2x.png</file>
         <file>images/check@3x.png</file>
diff --git a/src/imports/controls/universal/Menu.qml b/src/imports/controls/universal/Menu.qml
index d7a27563..b2e71106 100644
--- a/src/imports/controls/universal/Menu.qml
+++ b/src/imports/controls/universal/Menu.qml
@@ -48,6 +48,7 @@ T.Menu {
                              contentItem ? contentItem.implicitHeight : 0) + topPadding + bottomPadding
 
     margins: 0
+    overlap: 1
 
     delegate: MenuItem { }
 
diff --git a/src/imports/controls/universal/MenuItem.qml b/src/imports/controls/universal/MenuItem.qml
index 7924e025..56f2eafa 100644
--- a/src/imports/controls/universal/MenuItem.qml
+++ b/src/imports/controls/universal/MenuItem.qml
@@ -60,8 +60,10 @@ T.MenuItem {
     icon.color: !enabled ? Universal.baseLowColor : Universal.baseHighColor
 
     contentItem: IconLabel {
-        leftPadding: control.checkable && !control.mirrored ? control.indicator.width + control.spacing : 0
-        rightPadding: control.checkable && control.mirrored ? control.indicator.width + control.spacing : 0
+        readonly property real arrowPadding: control.subMenu && control.arrow ? control.arrow.width + control.spacing : 0
+        readonly property real indicatorPadding: control.checkable && control.indicator ? control.indicator.width + control.spacing : 0
+        leftPadding: !control.mirrored ? indicatorPadding : arrowPadding
+        rightPadding: control.mirrored ? indicatorPadding : arrowPadding
 
         spacing: control.spacing
         mirrored: control.mirrored
@@ -74,6 +76,16 @@ T.MenuItem {
         color: !control.enabled ? control.Universal.baseLowColor : control.Universal.baseHighColor
     }
 
+    arrow: ColorImage {
+        x: control.mirrored ? control.leftPadding : control.width - width - control.rightPadding
+        y: control.topPadding + (control.availableHeight - height) / 2
+
+        visible: control.subMenu
+        mirror: control.mirrored
+        color: !enabled ? control.Universal.baseLowColor : control.Universal.baseHighColor
+        source: "qrc:/qt-project.org/imports/QtQuick/Controls.2/Universal/images/rightarrow.png"
+    }
+
     indicator: ColorImage {
         x: control.text ? (control.mirrored ? control.width - width - control.rightPadding : control.leftPadding) : control.leftPadding + (control.availableWidth - width) / 2
         y: control.topPadding + (control.availableHeight - height) / 2
diff --git a/src/quicktemplates2/qquickmenu.cpp b/src/quicktemplates2/qquickmenu.cpp
index fa6b88ef..64f293d8 100644
--- a/src/quicktemplates2/qquickmenu.cpp
+++ b/src/quicktemplates2/qquickmenu.cpp
@@ -131,17 +131,30 @@ QT_BEGIN_NAMESPACE
     }
     \endcode
 
-    Since QtQuick.Controls 2.3 (Qt 5.10), it is also possible to declare
-    Action objects inside Menu:
+    Since QtQuick.Controls 2.3 (Qt 5.10), it is also possible to create sub-menus
+    and declare Action objects inside Menu:
 
     \code
     Menu {
         Action { text: "Cut" }
         Action { text: "Copy" }
         Action { text: "Paste" }
+
+        MenuSeparator { }
+
+        Menu {
+            title: "Find/Replace"
+            Action { text: "Find Next" }
+            Action { text: "Find Previous" }
+            Action { text: "Replace" }
+        }
     }
     \endcode
 
+    Sub-menus are \l {cascade}{cascading} by default on desktop platforms
+    that have a mouse cursor available. Non-cascading menus are shown one
+    menu at a time, and centered over the parent menu.
+
     Typically, menu items are statically declared as children of the menu, but
     Menu also provides API to \l {addItem}{add}, \l {insertItem}{insert},
     \l {moveItem}{move} and \l {removeItem}{remove} items dynamically. The
@@ -154,8 +167,24 @@ QT_BEGIN_NAMESPACE
     \sa {Customizing Menu}, {Menu Controls}, {Popup Controls}
 */
 
+static const QQuickPopup::ClosePolicy defaultMenuClosePolicy =
+        QQuickPopup::CloseOnEscape | QQuickPopup::CloseOnPressOutside | QQuickPopup::CloseOnReleaseOutside;
+static const QQuickPopup::ClosePolicy cascadingSubMenuClosePolicy =
+        QQuickPopup::CloseOnEscape | QQuickPopup::CloseOnPressOutsideParent | QQuickPopup::CloseOnReleaseOutsideParent;
+
+static bool shouldCascade()
+{
+#if QT_CONFIG(cursor)
+    return QGuiApplicationPrivate::platformIntegration()->hasCapability(QPlatformIntegration::MultipleWindows);
+#else
+    return false;
+#endif
+}
+
 QQuickMenuPrivate::QQuickMenuPrivate()
-    : contentItem(nullptr),
+    : cascade(shouldCascade()),
+      overlap(0),
+      contentItem(nullptr),
       contentModel(nullptr),
       delegate(nullptr)
 {
@@ -184,7 +213,7 @@ void QQuickMenuPrivate::insertItem(int index, QQuickItem *item)
         Q_Q(QQuickMenu);
         QQuickMenuItemPrivate::get(menuItem)->setMenu(q);
         QObjectPrivate::connect(menuItem, &QQuickMenuItem::pressed, this, &QQuickMenuPrivate::onItemPressed);
-        QObject::connect(menuItem, &QQuickMenuItem::triggered, q, &QQuickPopup::close);
+        QObjectPrivate::connect(menuItem, &QQuickMenuItem::triggered, this, &QQuickMenuPrivate::onItemTriggered);
         QObjectPrivate::connect(menuItem, &QQuickItem::activeFocusChanged, this, &QQuickMenuPrivate::onItemActiveFocusChanged);
         QObjectPrivate::connect(menuItem, &QQuickControl::hoveredChanged, this, &QQuickMenuPrivate::onItemHovered);
     }
@@ -205,16 +234,15 @@ void QQuickMenuPrivate::removeItem(int index, QQuickItem *item)
 
     QQuickMenuItem *menuItem = qobject_cast<QQuickMenuItem *>(item);
     if (menuItem) {
-        Q_Q(QQuickMenu);
         QQuickMenuItemPrivate::get(menuItem)->setMenu(nullptr);
         QObjectPrivate::disconnect(menuItem, &QQuickMenuItem::pressed, this, &QQuickMenuPrivate::onItemPressed);
-        QObject::disconnect(menuItem, &QQuickMenuItem::triggered, q, &QQuickPopup::close);
+        QObjectPrivate::disconnect(menuItem, &QQuickMenuItem::triggered, this, &QQuickMenuPrivate::onItemTriggered);
         QObjectPrivate::disconnect(menuItem, &QQuickItem::activeFocusChanged, this, &QQuickMenuPrivate::onItemActiveFocusChanged);
         QObjectPrivate::disconnect(menuItem, &QQuickControl::hoveredChanged, this, &QQuickMenuPrivate::onItemHovered);
     }
 }
 
-QQuickItem *QQuickMenuPrivate::createItem(QQuickAction *action)
+QQuickItem *QQuickMenuPrivate::beginCreateItem()
 {
     Q_Q(QQuickMenu);
     if (!delegate)
@@ -227,15 +255,37 @@ QQuickItem *QQuickMenuPrivate::createItem(QQuickAction *action)
     context->setContextObject(q);
 
     QObject *object = delegate->beginCreate(context);
-    if (QQuickItem *item = qobject_cast<QQuickItem *>(object)) {
-        if (QQuickAbstractButton *button = qobject_cast<QQuickAbstractButton*>(object))
-            button->setAction(action);
-        delegate->completeCreate();
-        return item;
-    }
+    QQuickItem *item = qobject_cast<QQuickItem *>(object);
+    if (!item)
+        delete object;
+
+    return item;
+}
+
+void QQuickMenuPrivate::completeCreateItem()
+{
+    if (!delegate)
+        return;
 
-    delete object;
-    return nullptr;
+    delegate->completeCreate();
+}
+
+QQuickItem *QQuickMenuPrivate::createItem(QQuickMenu *menu)
+{
+    QQuickItem *item = beginCreateItem();
+    if (QQuickMenuItem *menuItem = qobject_cast<QQuickMenuItem *>(item))
+        QQuickMenuItemPrivate::get(menuItem)->setSubMenu(menu);
+    completeCreateItem();
+    return item;
+}
+
+QQuickItem *QQuickMenuPrivate::createItem(QQuickAction *action)
+{
+    QQuickItem *item = beginCreateItem();
+    if (QQuickAbstractButton *button = qobject_cast<QQuickAbstractButton *>(item))
+        button->setAction(action);
+    completeCreateItem();
+    return item;
 }
 
 void QQuickMenuPrivate::resizeItem(QQuickItem *item)
@@ -299,6 +349,12 @@ void QQuickMenuPrivate::itemGeometryChanged(QQuickItem *, QQuickGeometryChange,
         resizeItems();
 }
 
+bool QQuickMenuPrivate::blockInput(QQuickItem *item, const QPointF &point) const
+{
+    // keep the parent menu open when a cascading sub-menu (this menu) is interacted with
+    return (cascade && parentMenu && contains(point)) || QQuickPopupPrivate::blockInput(item, point);
+}
+
 void QQuickMenuPrivate::onItemPressed()
 {
     Q_Q(QQuickMenu);
@@ -314,9 +370,40 @@ void QQuickMenuPrivate::onItemHovered()
     if (!button || !button->isHovered() || QQuickAbstractButtonPrivate::get(button)->touchId != -1)
         return;
 
+    QQuickMenuItem *oldCurrentItem = currentItem;
+
     int index = contentModel->indexOf(button, nullptr);
-    if (index != -1)
+    if (index != -1) {
         setCurrentIndex(index);
+        if (oldCurrentItem != currentItem) {
+            if (oldCurrentItem)
+                closeSubMenu(oldCurrentItem->subMenu());
+            if (currentItem) {
+                QQuickMenu *subMenu = currentItem->menu();
+                if (subMenu && subMenu->cascade())
+                    openSubMenu(currentItem, false);
+            }
+        }
+    }
+}
+
+void QQuickMenuPrivate::onItemTriggered()
+{
+    Q_Q(QQuickMenu);
+    QQuickMenuItem *item = qobject_cast<QQuickMenuItem *>(q->sender());
+    if (!item)
+        return;
+
+    if (item->subMenu()) {
+        openSubMenu(item, true);
+    } else {
+        // close the whole chain of menus
+        q->close();
+        while (parentMenu) {
+            parentMenu->close();
+            parentMenu = QQuickMenuPrivate::get(parentMenu)->parentMenu;
+        }
+    }
 }
 
 void QQuickMenuPrivate::onItemActiveFocusChanged()
@@ -330,6 +417,67 @@ void QQuickMenuPrivate::onItemActiveFocusChanged()
     setCurrentIndex(indexOfItem);
 }
 
+void QQuickMenuPrivate::openSubMenu(QQuickMenuItem *item, bool activate)
+{
+    Q_Q(QQuickMenu);
+    QQuickMenu *subMenu = item ? item->subMenu() : nullptr;
+    if (!subMenu)
+        return;
+
+    if (cascade) {
+        subMenu->setParentItem(item);
+        subMenu->setClosePolicy(cascadingSubMenuClosePolicy);
+        if (popupItem->isMirrored()) {
+            subMenu->setTransformOrigin(QQuickPopup::TopRight);
+            subMenu->setPosition(QPointF(-subMenu->width() - q->leftPadding() + subMenu->overlap(), -subMenu->topPadding()));
+        } else {
+            subMenu->setTransformOrigin(QQuickPopup::TopLeft);
+            subMenu->setPosition(QPointF(item->width() + q->rightPadding() - subMenu->overlap(), -subMenu->topPadding()));
+        }
+    } else {
+        subMenu->setParentItem(parentItem);
+        subMenu->setClosePolicy(defaultMenuClosePolicy);
+        subMenu->setTransformOrigin(QQuickPopup::Center);
+        subMenu->setPosition(QPointF(q->x() + (q->width() - subMenu->width()) / 2,
+                                     q->y() + (q->height() - subMenu->height()) / 2));
+    }
+
+    QQuickMenuPrivate *p = QQuickMenuPrivate::get(subMenu);
+    p->parentMenu = q;
+    if (activate)
+        p->setCurrentIndex(0);
+    subMenu->setCascade(cascade);
+    subMenu->open();
+
+    // transfer focus to the sub-menu
+    if (focus)
+        subMenu->popupItem()->setFocus(true);
+
+    if (!subMenu->cascade())
+        q->close();
+}
+
+void QQuickMenuPrivate::closeSubMenu(QQuickMenu *subMenu)
+{
+    if (!subMenu || !subMenu->isVisible())
+        return;
+
+    // transfer focus back to the parent menu
+    QQuickMenu *parentMenu = QQuickMenuPrivate::get(subMenu)->parentMenu;
+    if (parentMenu && parentMenu->hasFocus()) {
+        parentMenu->popupItem()->setFocus(true);
+        if (!subMenu->cascade())
+            parentMenu->open();
+    }
+
+    // close the whole chain of sub-menus
+    while (subMenu) {
+        QPointer<QQuickMenuItem> currentSubMenuItem = QQuickMenuPrivate::get(subMenu)->currentItem;
+        subMenu->close();
+        subMenu = currentSubMenuItem ? currentSubMenuItem->subMenu() : nullptr;
+    }
+}
+
 int QQuickMenuPrivate::currentIndex() const
 {
     QVariant index = contentItem->property("currentIndex");
@@ -355,13 +503,15 @@ void QQuickMenuPrivate::setCurrentIndex(int index)
 
 void QQuickMenuPrivate::contentData_append(QQmlListProperty<QObject> *prop, QObject *obj)
 {
-    QQuickMenuPrivate *p = static_cast<QQuickMenuPrivate *>(prop->data);
-    QQuickMenu *q = static_cast<QQuickMenu *>(prop->object);
+    QQuickMenu *q = qobject_cast<QQuickMenu *>(prop->object);
+    QQuickMenuPrivate *p = QQuickMenuPrivate::get(q);
 
     QQuickItem *item = qobject_cast<QQuickItem *>(obj);
     if (!item) {
         if (QQuickAction *action = qobject_cast<QQuickAction *>(obj))
             item = p->createItem(action);
+        else if (QQuickMenu *menu = qobject_cast<QQuickMenu *>(obj))
+            item = p->createItem(menu);
     }
 
     if (item) {
@@ -378,27 +528,27 @@ void QQuickMenuPrivate::contentData_append(QQmlListProperty<QObject> *prop, QObj
 
 int QQuickMenuPrivate::contentData_count(QQmlListProperty<QObject> *prop)
 {
-    QQuickMenuPrivate *p = static_cast<QQuickMenuPrivate *>(prop->data);
-    return p->contentData.count();
+    QQuickMenu *q = static_cast<QQuickMenu *>(prop->object);
+    return QQuickMenuPrivate::get(q)->contentData.count();
 }
 
 QObject *QQuickMenuPrivate::contentData_at(QQmlListProperty<QObject> *prop, int index)
 {
-    QQuickMenuPrivate *p = static_cast<QQuickMenuPrivate *>(prop->data);
-    return p->contentData.value(index);
+    QQuickMenu *q = static_cast<QQuickMenu *>(prop->object);
+    return QQuickMenuPrivate::get(q)->contentData.value(index);
 }
 
 void QQuickMenuPrivate::contentData_clear(QQmlListProperty<QObject> *prop)
 {
-    QQuickMenuPrivate *p = static_cast<QQuickMenuPrivate *>(prop->data);
-    p->contentData.clear();
+    QQuickMenu *q = static_cast<QQuickMenu *>(prop->object);
+    QQuickMenuPrivate::get(q)->contentData.clear();
 }
 
 QQuickMenu::QQuickMenu(QObject *parent)
     : QQuickPopup(*(new QQuickMenuPrivate), parent)
 {
     setFocus(true);
-    setClosePolicy(CloseOnEscape | CloseOnPressOutside | CloseOnReleaseOutside);
+    setClosePolicy(defaultMenuClosePolicy);
 }
 
 /*!
@@ -568,8 +718,7 @@ QVariant QQuickMenu::contentModel() const
 */
 QQmlListProperty<QObject> QQuickMenu::contentData()
 {
-    Q_D(QQuickMenu);
-    return QQmlListProperty<QObject>(this, d,
+    return QQmlListProperty<QObject>(this, nullptr,
         QQuickMenuPrivate::contentData_append,
         QQuickMenuPrivate::contentData_count,
         QQuickMenuPrivate::contentData_at,
@@ -602,6 +751,64 @@ void QQuickMenu::setTitle(QString &title)
 
 /*!
     \since QtQuick.Controls 2.3 (Qt 5.10)
+    \qmlproperty bool QtQuick.Controls::Menu::cascade
+
+    This property holds whether the menu cascades its sub-menus.
+
+    The default value is platform-specific. Menus are cascading by default on
+    desktop platforms that have a mouse cursor available. Non-cascading menus
+    are shown one menu at a time, and centered over the parent menu.
+
+    \note Changing the value of the property has no effect while the menu is open.
+
+    \sa overlap
+*/
+bool QQuickMenu::cascade() const
+{
+    Q_D(const QQuickMenu);
+    return d->cascade;
+}
+
+void QQuickMenu::setCascade(bool cascade)
+{
+    Q_D(QQuickMenu);
+    if (d->cascade == cascade)
+        return;
+    d->cascade = cascade;
+    emit cascadeChanged();
+}
+
+/*!
+    \since QtQuick.Controls 2.3 (Qt 5.10)
+    \qmlproperty real QtQuick.Controls::Menu::overlap
+
+    This property holds the amount of pixels by which the menu horizontally overlaps its parent menu.
+
+    The property only has effect when the menu is used as a cascading sub-menu.
+
+    The default value is style-specific.
+
+    \note Changing the value of the property has no effect while the menu is open.
+
+    \sa cascade
+*/
+qreal QQuickMenu::overlap() const
+{
+    Q_D(const QQuickMenu);
+    return d->overlap;
+}
+
+void QQuickMenu::setOverlap(qreal overlap)
+{
+    Q_D(QQuickMenu);
+    if (d->overlap == overlap)
+        return;
+    d->overlap = overlap;
+    emit cascadeChanged();
+}
+
+/*!
+    \since QtQuick.Controls 2.3 (Qt 5.10)
     \qmlproperty Component QtQuick.Controls::Menu::delegate
 
     This property holds the component that is used to create items
@@ -758,7 +965,7 @@ void QQuickMenu::itemChange(QQuickItem::ItemChange change, const QQuickItem::Ite
     QQuickPopup::itemChange(change, data);
 
     if (change == QQuickItem::ItemVisibleHasChanged) {
-        if (!data.boolValue) {
+        if (!data.boolValue && d->cascade) {
             // Ensure that when the menu isn't visible, there's no current item
             // the next time it's opened.
             QQuickItem *focusItem = QQuickItemPrivate::get(d->contentItem)->subFocusItem;
@@ -796,6 +1003,16 @@ void QQuickMenu::keyReleaseEvent(QKeyEvent *event)
             QMetaObject::invokeMethod(d->contentItem, "incrementCurrentIndex");
         break;
 
+    case Qt::Key_Left:
+    case Qt::Key_Right:
+        if (d->popupItem->isMirrored() == (event->key() == Qt::Key_Right)) {
+            if (d->parentMenu && d->currentItem)
+                d->closeSubMenu(this);
+        } else {
+            d->openSubMenu(d->currentItem, true);
+        }
+        return;
+
     default:
         break;
     }
diff --git a/src/quicktemplates2/qquickmenu_p.h b/src/quicktemplates2/qquickmenu_p.h
index 04186f1a..f7f56d45 100644
--- a/src/quicktemplates2/qquickmenu_p.h
+++ b/src/quicktemplates2/qquickmenu_p.h
@@ -65,6 +65,8 @@ class Q_QUICKTEMPLATES2_PRIVATE_EXPORT QQuickMenu : public QQuickPopup
     Q_PROPERTY(QVariant contentModel READ contentModel CONSTANT FINAL)
     Q_PROPERTY(QQmlListProperty<QObject> contentData READ contentData FINAL)
     Q_PROPERTY(QString title READ title WRITE setTitle NOTIFY titleChanged FINAL)
+    Q_PROPERTY(bool cascade READ cascade WRITE setCascade NOTIFY cascadeChanged FINAL REVISION 3)
+    Q_PROPERTY(qreal overlap READ overlap WRITE setOverlap NOTIFY overlapChanged FINAL REVISION 3)
     Q_PROPERTY(QQmlComponent *delegate READ delegate WRITE setDelegate NOTIFY delegateChanged FINAL REVISION 3)
     Q_CLASSINFO("DefaultProperty", "contentData")
 
@@ -85,6 +87,12 @@ public:
     QString title() const;
     void setTitle(QString &title);
 
+    bool cascade() const;
+    void setCascade(bool cascade);
+
+    qreal overlap() const;
+    void setOverlap(qreal overlap);
+
     QQmlComponent *delegate() const;
     void setDelegate(QQmlComponent *delegate);
 
@@ -98,6 +106,8 @@ protected:
 
 Q_SIGNALS:
     void titleChanged(const QString &title);
+    Q_REVISION(3) void cascadeChanged();
+    Q_REVISION(3) void overlapChanged();
     Q_REVISION(3) void delegateChanged();
 
 protected:
diff --git a/src/quicktemplates2/qquickmenu_p_p.h b/src/quicktemplates2/qquickmenu_p_p.h
index b9e0512b..9fd10779 100644
--- a/src/quicktemplates2/qquickmenu_p_p.h
+++ b/src/quicktemplates2/qquickmenu_p_p.h
@@ -51,11 +51,11 @@
 #include <QtCore/qvector.h>
 #include <QtCore/qpointer.h>
 
+#include <QtQuickTemplates2/private/qquickmenu_p.h>
 #include <QtQuickTemplates2/private/qquickpopup_p_p.h>
 
 QT_BEGIN_NAMESPACE
 
-class QQuickMenu;
 class QQuickAction;
 class QQmlComponent;
 class QQmlObjectModel;
@@ -68,10 +68,20 @@ class Q_QUICKTEMPLATES2_PRIVATE_EXPORT QQuickMenuPrivate : public QQuickPopupPri
 public:
     QQuickMenuPrivate();
 
+    static QQuickMenuPrivate *get(QQuickMenu *menu)
+    {
+        return menu->d_func();
+    }
+
     QQuickItem *itemAt(int index) const;
     void insertItem(int index, QQuickItem *item);
     void moveItem(int from, int to);
     void removeItem(int index, QQuickItem *item);
+
+    QQuickItem *beginCreateItem();
+    void completeCreateItem();
+
+    QQuickItem *createItem(QQuickMenu *menu);
     QQuickItem *createItem(QQuickAction *action);
 
     void resizeItem(QQuickItem *item);
@@ -83,10 +93,16 @@ public:
     void itemDestroyed(QQuickItem *item) override;
     void itemGeometryChanged(QQuickItem *, QQuickGeometryChange change, const QRectF &diff) override;
 
+    bool blockInput(QQuickItem *item, const QPointF &point) const override;
+
     void onItemPressed();
     void onItemHovered();
+    void onItemTriggered();
     void onItemActiveFocusChanged();
 
+    void openSubMenu(QQuickMenuItem *item, bool activate);
+    void closeSubMenu(QQuickMenu *subMenu);
+
     int currentIndex() const;
     void setCurrentIndex(int index);
 
@@ -95,6 +111,9 @@ public:
     static QObject *contentData_at(QQmlListProperty<QObject> *prop, int index);
     static void contentData_clear(QQmlListProperty<QObject> *prop);
 
+    bool cascade;
+    qreal overlap;
+    QPointer<QQuickMenu> parentMenu;
     QPointer<QQuickMenuItem> currentItem;
     QQuickItem *contentItem; // TODO: cleanup
     QVector<QObject *> contentData;
diff --git a/src/quicktemplates2/qquickmenuitem.cpp b/src/quicktemplates2/qquickmenuitem.cpp
index 3ef03caf..69a2b73b 100644
--- a/src/quicktemplates2/qquickmenuitem.cpp
+++ b/src/quicktemplates2/qquickmenuitem.cpp
@@ -36,6 +36,7 @@
 
 #include "qquickmenuitem_p.h"
 #include "qquickmenuitem_p_p.h"
+#include "qquickmenu_p.h"
 
 #include <QtGui/qpa/qplatformtheme.h>
 #include <QtQuick/private/qquickevents_p_p.h>
@@ -89,7 +90,9 @@ QT_BEGIN_NAMESPACE
 
 QQuickMenuItemPrivate::QQuickMenuItemPrivate()
     : highlighted(false),
-      menu(nullptr)
+      arrow(nullptr),
+      menu(nullptr),
+      subMenu(nullptr)
 {
 }
 
@@ -103,6 +106,24 @@ void QQuickMenuItemPrivate::setMenu(QQuickMenu *newMenu)
     emit q->menuChanged();
 }
 
+void QQuickMenuItemPrivate::setSubMenu(QQuickMenu *newSubMenu)
+{
+    Q_Q(QQuickMenuItem);
+    if (subMenu == newSubMenu)
+        return;
+
+    if (subMenu)
+        QObject::disconnect(subMenu, &QQuickMenu::titleChanged, q, &QQuickAbstractButton::setText);
+
+    if (newSubMenu) {
+        QObject::connect(newSubMenu, &QQuickMenu::titleChanged, q, &QQuickAbstractButton::setText);
+        q->setText(newSubMenu->title());
+    }
+
+    subMenu = newSubMenu;
+    emit q->subMenuChanged();
+}
+
 /*!
     \qmlsignal void QtQuick.Controls::MenuItem::triggered()
 
@@ -142,6 +163,33 @@ void QQuickMenuItem::setHighlighted(bool highlighted)
 
 /*!
     \since QtQuick.Controls 2.3 (Qt 5.10)
+    \qmlproperty Item QtQuick.Controls::MenuItem::arrow
+
+    This property holds the sub-menu arrow item.
+
+    \sa {Customizing MenuItem}
+*/
+QQuickItem *QQuickMenuItem::arrow() const
+{
+    Q_D(const QQuickMenuItem);
+    return d->arrow;
+}
+
+void QQuickMenuItem::setArrow(QQuickItem *arrow)
+{
+    Q_D(QQuickMenuItem);
+    if (d->arrow == arrow)
+        return;
+
+    QQuickControlPrivate::destroyDelegate(d->arrow, this);
+    d->arrow = arrow;
+    if (arrow && !arrow->parentItem())
+        arrow->setParentItem(this);
+    emit arrowChanged();
+}
+
+/*!
+    \since QtQuick.Controls 2.3 (Qt 5.10)
     \qmlproperty Menu QtQuick.Controls::MenuItem::menu
     \readonly
 
@@ -154,6 +202,20 @@ QQuickMenu *QQuickMenuItem::menu() const
     return d->menu;
 }
 
+/*!
+    \since QtQuick.Controls 2.3 (Qt 5.10)
+    \qmlproperty Menu QtQuick.Controls::MenuItem::subMenu
+    \readonly
+
+    This property holds the sub-menu that this item presents in
+    the parent menu, or \c null if this item is not a sub-menu item.
+*/
+QQuickMenu *QQuickMenuItem::subMenu() const
+{
+    Q_D(const QQuickMenuItem);
+    return d->subMenu;
+}
+
 QFont QQuickMenuItem::defaultFont() const
 {
     return QQuickControlPrivate::themeFont(QPlatformTheme::MenuItemFont);
diff --git a/src/quicktemplates2/qquickmenuitem_p.h b/src/quicktemplates2/qquickmenuitem_p.h
index 92b42488..7c469b6a 100644
--- a/src/quicktemplates2/qquickmenuitem_p.h
+++ b/src/quicktemplates2/qquickmenuitem_p.h
@@ -59,7 +59,9 @@ class Q_QUICKTEMPLATES2_PRIVATE_EXPORT QQuickMenuItem : public QQuickAbstractBut
 {
     Q_OBJECT
     Q_PROPERTY(bool highlighted READ isHighlighted WRITE setHighlighted NOTIFY highlightedChanged FINAL)
+    Q_PROPERTY(QQuickItem *arrow READ arrow WRITE setArrow NOTIFY arrowChanged FINAL REVISION 3)
     Q_PROPERTY(QQuickMenu *menu READ menu NOTIFY menuChanged FINAL REVISION 3)
+    Q_PROPERTY(QQuickMenu *subMenu READ subMenu NOTIFY subMenuChanged FINAL REVISION 3)
 
 public:
     explicit QQuickMenuItem(QQuickItem *parent = nullptr);
@@ -67,12 +69,18 @@ public:
     bool isHighlighted() const;
     void setHighlighted(bool highlighted);
 
+    QQuickItem *arrow() const;
+    void setArrow(QQuickItem *arrow);
+
     QQuickMenu *menu() const;
+    QQuickMenu *subMenu() const;
 
 Q_SIGNALS:
     void triggered();
     void highlightedChanged();
+    Q_REVISION(3) void arrowChanged();
     Q_REVISION(3) void menuChanged();
+    Q_REVISION(3) void subMenuChanged();
 
 protected:
     QFont defaultFont() const override;
diff --git a/src/quicktemplates2/qquickmenuitem_p_p.h b/src/quicktemplates2/qquickmenuitem_p_p.h
index f1cded91..d8b86d6e 100644
--- a/src/quicktemplates2/qquickmenuitem_p_p.h
+++ b/src/quicktemplates2/qquickmenuitem_p_p.h
@@ -68,9 +68,12 @@ public:
     }
 
     void setMenu(QQuickMenu *menu);
+    void setSubMenu(QQuickMenu *subMenu);
 
     bool highlighted;
+    QQuickItem *arrow;
     QQuickMenu *menu;
+    QQuickMenu *subMenu;
 };
 
 QT_END_NAMESPACE