QQuickMenu: add a little delay for opening sub-menus on hover

This improves the usability on desktop. When a menu has multiple sub-
menu items, they don't all trigger a sub-menu (and close immediately)
while moving mouse over the items.

Change-Id: Ie4c9e409da8d6877e35506bffb94ed57f5985dcd
Reviewed-by: Mitch Curtis <mitch.curtis@qt.io>

src/quicktemplates2/qquickmenu.cpp

@@ -59,6 +59,9 @@
 
 QT_BEGIN_NAMESPACE
 
+// copied from qfusionstyle.cpp
+static const int SUBMENU_DELAY = 225;
+
 /*!
     \qmltype Menu
     \inherits Popup
@@ -183,6 +186,7 @@ static bool shouldCascade()
 
 QQuickMenuPrivate::QQuickMenuPrivate()
     : cascade(shouldCascade()),
+      hoverTimer(0),
       overlap(0),
       contentItem(nullptr),
       contentModel(nullptr),
@@ -371,7 +375,7 @@ void QQuickMenuPrivate::onItemHovered()
             if (currentItem) {
                 QQuickMenu *subMenu = currentItem->menu();
                 if (subMenu && subMenu->cascade())
-                    openSubMenu(currentItem, false);
+                    startHoverTimer();
             }
         }
     }
@@ -468,6 +472,23 @@ void QQuickMenuPrivate::closeSubMenu(QQuickMenu *subMenu)
     }
 }
 
+void QQuickMenuPrivate::startHoverTimer()
+{
+    Q_Q(QQuickMenu);
+    stopHoverTimer();
+    hoverTimer = q->startTimer(SUBMENU_DELAY);
+}
+
+void QQuickMenuPrivate::stopHoverTimer()
+{
+    Q_Q(QQuickMenu);
+    if (!hoverTimer)
+        return;
+
+    q->killTimer(hoverTimer);
+    hoverTimer = 0;
+}
+
 int QQuickMenuPrivate::currentIndex() const
 {
     QVariant index = contentItem->property("currentIndex");
@@ -483,6 +504,7 @@ void QQuickMenuPrivate::setCurrentIndex(int index)
     QQuickMenuItem *newCurrentItem = contentItem->property("currentItem").value<QQuickMenuItem *>();
 
     if (currentItem != newCurrentItem) {
+        stopHoverTimer();
         if (currentItem)
             currentItem->setHighlighted(false);
         if (newCurrentItem)
@@ -1013,6 +1035,15 @@ void QQuickMenu::keyReleaseEvent(QKeyEvent *event)
         item->forceActiveFocus();
 }
 
+void QQuickMenu::timerEvent(QTimerEvent *event)
+{
+    Q_D(QQuickMenu);
+    if (event->timerId() == d->hoverTimer) {
+        d->openSubMenu(d->currentItem, false);
+        d->stopHoverTimer();
+    }
+}
+
 QFont QQuickMenu::defaultFont() const
 {
     return QQuickControlPrivate::themeFont(QPlatformTheme::MenuFont);

src/quicktemplates2/qquickmenu_p.h

@@ -111,6 +111,8 @@ Q_SIGNALS:
     Q_REVISION(3) void delegateChanged();
 
 protected:
+    void timerEvent(QTimerEvent *event) override;
+
     QFont defaultFont() const override;
     QPalette defaultPalette() const override;
 

src/quicktemplates2/qquickmenu_p_p.h

@@ -102,6 +102,9 @@ public:
     void openSubMenu(QQuickMenuItem *item, bool activate);
     void closeSubMenu(QQuickMenu *subMenu);
 
+    void startHoverTimer();
+    void stopHoverTimer();
+
     int currentIndex() const;
     void setCurrentIndex(int index);
 
@@ -111,6 +114,7 @@ public:
     static void contentData_clear(QQmlListProperty<QObject> *prop);
 
     bool cascade;
+    int hoverTimer;
     qreal overlap;
     QPointer<QQuickMenu> parentMenu;
     QPointer<QQuickMenuItem> currentItem;

tests/auto/menu/tst_menu.cpp

@@ -636,7 +636,9 @@ void tst_menu::subMenuMouse()
     QCOMPARE(mainMenu->isVisible(), cascade);
     QVERIFY(subMenu1->isVisible());
     QVERIFY(!subMenu2->isVisible());
-    QCOMPARE(subSubMenu1->isVisible(), cascade);
+    QVERIFY(!subSubMenu1->isVisible());
+    if (cascade)
+        QTRY_VERIFY(subSubMenu1->isVisible());
 
     // close the sub-sub-menu with mouse hover over another parent menu item
     QQuickMenuItem *subMenuItem1 = qobject_cast<QQuickMenuItem *>(subMenu1->itemAt(0));
@@ -653,7 +655,9 @@ void tst_menu::subMenuMouse()
     QCOMPARE(mainMenu->isVisible(), cascade);
     QVERIFY(subMenu1->isVisible());
     QVERIFY(!subMenu2->isVisible());
-    QCOMPARE(subSubMenu1->isVisible(), cascade);
+    QVERIFY(!subSubMenu1->isVisible());
+    if (cascade)
+        QTRY_VERIFY(subSubMenu1->isVisible());
 
     // close sub-menu and sub-sub-menu with mouse hover in the main menu
     QQuickMenuItem *mainMenuItem1 = qobject_cast<QQuickMenuItem *>(mainMenu->itemAt(0));