Menus: Clean popup hide and destroy logic

When a menu popup gets closed it usually needs to be destroyed right away
since we don't recycle its contents. There is an exception, however, and
it's when he user triggers a menu item.

In this case, we need to proceed in three steps. First, we hide the menu
popup, then we emit the triggered signal, and when that one returns, the
menu contents can be disposed. If we did all in a single step, we may end
up with a crash since we don't support deleting a QtQuick item while it's
running a signal handler. Delayed deletions don't work either in the case
when the triggered handler ends up running the event loop.

Task-number: QTBUG-45182
Task-number: QTBUG-47682
Task-number: QTBUG-48382
Change-Id: Ic39717e09f38df602f641250cd81cf4931863db6
Reviewed-by: J-P Nurmi <jpnurmi@theqtcompany.com>

9 files changed, 93 insertions, 42 deletions

diff --git a/src/controls/ComboBox.qml b/src/controls/ComboBox.qml
index d0940772..a2eff0b6 100644
--- a/src/controls/ComboBox.qml
+++ b/src/controls/ComboBox.qml
@@ -626,8 +626,7 @@ Control {
 
         function toggleShow() {
             if (popup.__popupVisible) {
-                popup.__dismissMenu()
-                popup.__destroyAllMenuPopups()
+                popup.__dismissAndDestroy()
             } else {
                 if (items[__selectedIndex])
                     items[__selectedIndex].checked = true
diff --git a/src/controls/MenuBar.qml b/src/controls/MenuBar.qml
index eddd48cd..444185cc 100644
--- a/src/controls/MenuBar.qml
+++ b/src/controls/MenuBar.qml
@@ -155,10 +155,8 @@ MenuBarPrivate {
 
                 if (oldIndex !== -1) {
                     var menu = root.menus[oldIndex]
-                    if (menu.__popupVisible) {
-                        menu.__dismissMenu()
-                        menu.__destroyAllMenuPopups()
-                    }
+                    if (menu.__popupVisible)
+                        menu.__dismissAndDestroy()
                 }
 
                 if (openedMenuIndex !== -1) {
diff --git a/src/controls/Private/EditMenu_base.qml b/src/controls/Private/EditMenu_base.qml
index e44ff599..15fe8d69 100644
--- a/src/controls/Private/EditMenu_base.qml
+++ b/src/controls/Private/EditMenu_base.qml
@@ -161,8 +161,7 @@ Item {
 
             if (control.menu) {
                 var menu = getMenuInstance();
-                menu.__dismissMenu();
-                menu.__destroyAllMenuPopups();
+                menu.__dismissAndDestroy();
                 var menuPos = mapToItem(null, mouse.x, mouse.y)
                 menu.__popup(Qt.rect(menuPos.x, menuPos.y, 0, 0), -1, MenuPrivate.EditMenu);
             }
diff --git a/src/controls/Private/MenuContentItem.qml b/src/controls/Private/MenuContentItem.qml
index 07edea2f..a0b346c4 100644
--- a/src/controls/Private/MenuContentItem.qml
+++ b/src/controls/Private/MenuContentItem.qml
@@ -80,16 +80,16 @@ Loader {
         function triggerCurrent() {
             var item = content.menuItemAt(__menu.__currentIndex)
             if (item)
-                content.triggered(item)
+                triggerAndDismiss(item)
         }
 
         function triggerAndDismiss(item) {
-            if (item && item.styleData.type !== MenuItemType.Separator) {
-                __menu.__dismissMenu()
-                if (item.styleData.type !== MenuItemType.Menu)
-                    item.__menuItem.trigger()
-                __menu.__destroyAllMenuPopups()
-            }
+            if (!item)
+                return;
+            if (item.styleData.type === MenuItemType.Separator)
+                __menu.__dismissAndDestroy()
+            else if (item.styleData.type === MenuItemType.Item)
+                item.__menuItem.trigger()
         }
     }
 
@@ -112,7 +112,7 @@ Loader {
         }
     }
 
-    Keys.onEscapePressed: __menu.__dismissMenu()
+    Keys.onEscapePressed: __menu.__dismissAndDestroy()
 
     Keys.onDownPressed: {
         if (__menu.__currentIndex < 0)
@@ -132,10 +132,8 @@ Loader {
     }
 
     Keys.onLeftPressed: {
-        if ((event.accepted = __menu.__parentMenu.hasOwnProperty("title"))) {
-            __menu.__closeMenu()
-            __menu.__destroyMenuPopup()
-        }
+        if ((event.accepted = __menu.__parentMenu.hasOwnProperty("title")))
+            __menu.__closeAndDestroy()
     }
 
     Keys.onRightPressed: {
@@ -246,10 +244,8 @@ Loader {
                 id: closeMenuTimer
                 interval: 1
                 onTriggered: {
-                    if (__menu.__currentIndex !== __menuItemIndex) {
-                        __menuItem.__closeMenu()
-                        __menuItem.__destroyMenuPopup()
-                    }
+                    if (__menu.__currentIndex !== __menuItemIndex)
+                        __menuItem.__closeAndDestroy()
                 }
             }
 
diff --git a/src/controls/qquickmenu.cpp b/src/controls/qquickmenu.cpp
index 617a3d03..beabe65b 100644
--- a/src/controls/qquickmenu.cpp
+++ b/src/controls/qquickmenu.cpp
@@ -265,14 +265,15 @@ QQuickMenu::QQuickMenu(QObject *parent)
       m_popupVisible(false),
       m_containersCount(0),
       m_xOffset(0),
-      m_yOffset(0)
+      m_yOffset(0),
+      m_triggerCount(0)
 {
     connect(this, SIGNAL(__textChanged()), this, SIGNAL(titleChanged()));
 
     m_platformMenu = QGuiApplicationPrivate::platformTheme()->createPlatformMenu();
     if (m_platformMenu) {
         connect(m_platformMenu, SIGNAL(aboutToShow()), this, SIGNAL(aboutToShow()));
-        connect(m_platformMenu, SIGNAL(aboutToHide()), this, SLOT(__closeMenu()));
+        connect(m_platformMenu, SIGNAL(aboutToHide()), this, SLOT(hideMenu()));
         if (platformItem())
             platformItem()->setMenu(m_platformMenu);
     }
@@ -415,7 +416,7 @@ void QQuickMenu::popup()
 void QQuickMenu::__popup(const QRectF &targetRect, int atItemIndex, MenuType menuType)
 {
     if (popupVisible()) {
-        __closeMenu();
+        hideMenu();
         // Mac and Windows would normally move the menu under the cursor, so we should not
         // return here. However, very often we want to re-contextualize the menu, and this
         // has to be done at the application level.
@@ -488,14 +489,30 @@ QRect QQuickMenu::popupGeometry() const
     return m_popupWindow->geometry();
 }
 
-void QQuickMenu::__closeMenu()
+void QQuickMenu::prepareItemTrigger(QQuickMenuItem *)
+{
+    m_triggerCount++;
+    __dismissMenu();
+}
+
+void QQuickMenu::concludeItemTrigger(QQuickMenuItem *)
+{
+    if (--m_triggerCount == 0)
+        destroyAllMenuPopups();
+}
+
+/*!
+ * \internal
+ * Close this menu's popup window. Emits aboutToHide and sets __popupVisible to false.
+ */
+void QQuickMenu::hideMenu()
 {
     if (m_popupVisible) {
         emit aboutToHide();
         setPopupVisible(false);
     }
-    if (m_popupWindow)
-        m_popupWindow->setVisible(false);
+    if (m_popupWindow && m_popupWindow->isVisible())
+        m_popupWindow->hide();
     m_parentWindow = 0;
 }
 
@@ -512,6 +529,12 @@ QQuickMenuPopupWindow *QQuickMenu::topMenuPopup() const
     return 0;
 }
 
+/*!
+ * \internal
+ * Dismiss all the menus this menu is attached to, bottom-up.
+ * In QQuickPopupWindow, before closing, dismissPopup() emits popupDismissed()
+ * which is connected to dismissPopup() on any child popup.
+ */
 void QQuickMenu::__dismissMenu()
 {
     if (m_platformMenu) {
@@ -521,14 +544,22 @@ void QQuickMenu::__dismissMenu()
     }
 }
 
+/*!
+ * \internal
+ * Called when the popup window visible property changes.
+ */
 void QQuickMenu::windowVisibleChanged(bool v)
 {
     if (!v) {
-        if (m_popupWindow && qobject_cast<QQuickMenuPopupWindow *>(m_popupWindow->transientParent())) {
-            m_popupWindow->transientParent()->setMouseGrabEnabled(true);
-            m_popupWindow->transientParent()->setKeyboardGrabEnabled(true);
+        if (m_popupWindow) {
+            QQuickMenuPopupWindow *parentMenuPopup = qobject_cast<QQuickMenuPopupWindow *>(m_popupWindow->transientParent());
+            if (parentMenuPopup) {
+                parentMenuPopup->setMouseGrabEnabled(true);
+                parentMenuPopup->setKeyboardGrabEnabled(true);
+            }
         }
-        __closeMenu();
+        if (m_popupVisible)
+            __closeAndDestroy();
     }
 }
 
@@ -538,18 +569,34 @@ void QQuickMenu::clearPopupWindow()
     emit __menuPopupDestroyed();
 }
 
-void QQuickMenu::__destroyMenuPopup()
+void QQuickMenu::destroyMenuPopup()
 {
+    if (m_triggerCount > 0)
+        return;
     if (m_popupWindow)
         m_popupWindow->setToBeDeletedLater();
 }
 
-void QQuickMenu::__destroyAllMenuPopups() {
+void QQuickMenu::destroyAllMenuPopups() {
+    if (m_triggerCount > 0)
+        return;
     QQuickMenuPopupWindow *popup = topMenuPopup();
     if (popup)
         popup->setToBeDeletedLater();
 }
 
+void QQuickMenu::__closeAndDestroy()
+{
+    hideMenu();
+    destroyMenuPopup();
+}
+
+void QQuickMenu::__dismissAndDestroy()
+{
+    __dismissMenu();
+    destroyAllMenuPopups();
+}
+
 void QQuickMenu::itemIndexToListIndex(int itemIndex, int *listIndex, int *containerIndex) const
 {
     *listIndex = -1;
diff --git a/src/controls/qquickmenu_p.h b/src/controls/qquickmenu_p.h
index a16e720a..a626179a 100644
--- a/src/controls/qquickmenu_p.h
+++ b/src/controls/qquickmenu_p.h
@@ -89,10 +89,10 @@ public:
     Q_INVOKABLE void __popup(const QRectF &targetRect, int atItemIndex = -1, MenuType menuType = DefaultMenu);
 
 public Q_SLOTS:
-    void __closeMenu();
     void __dismissMenu();
-    void __destroyMenuPopup();
-    void __destroyAllMenuPopups();
+
+    void __closeAndDestroy();
+    void __dismissAndDestroy();
 
 Q_SIGNALS:
     void itemsChanged();
@@ -142,11 +142,17 @@ public:
 
     QRect popupGeometry() const;
 
+    void prepareItemTrigger(QQuickMenuItem *);
+    void concludeItemTrigger(QQuickMenuItem *);
+    void destroyMenuPopup();
+    void destroyAllMenuPopups();
+
 protected Q_SLOTS:
     void updateSelectedIndex();
 
     void setMenuContentItem(QQuickItem *);
     void setPopupVisible(bool);
+    void hideMenu();
     void clearPopupWindow();
 
     void updateText();
@@ -189,6 +195,7 @@ private:
     qreal m_xOffset;
     qreal m_yOffset;
     QFont m_font;
+    int m_triggerCount;
 };
 
 QT_END_NAMESPACE
diff --git a/src/controls/qquickmenuitem.cpp b/src/controls/qquickmenuitem.cpp
index 8093c5fe..be15a435 100644
--- a/src/controls/qquickmenuitem.cpp
+++ b/src/controls/qquickmenuitem.cpp
@@ -674,7 +674,12 @@ void QQuickMenuItem::setEnabled(bool enabled)
 
 void QQuickMenuItem::trigger()
 {
+    QPointer<QQuickMenu> menu(parentMenu());
+    if (menu)
+        menu->prepareItemTrigger(this);
     action()->trigger(this);
+    if (menu)
+        menu->concludeItemTrigger(this);
 }
 
 QT_END_NAMESPACE
diff --git a/src/controls/qquickpopupwindow.cpp b/src/controls/qquickpopupwindow.cpp
index 08407e2d..a8f45167 100644
--- a/src/controls/qquickpopupwindow.cpp
+++ b/src/controls/qquickpopupwindow.cpp
@@ -138,7 +138,7 @@ void QQuickPopupWindow::dismissPopup()
 {
     m_dismissed = true;
     emit popupDismissed();
-    close();
+    hide();
 }
 
 void QQuickPopupWindow::mouseMoveEvent(QMouseEvent *e)
diff --git a/tests/auto/controls/data/tst_combobox.qml b/tests/auto/controls/data/tst_combobox.qml
index 057ff471..da8c79f8 100644
--- a/tests/auto/controls/data/tst_combobox.qml
+++ b/tests/auto/controls/data/tst_combobox.qml
@@ -524,7 +524,7 @@ TestCase {
         verify(comboBox.data[menuIndex].__popupVisible)
 
         // close the menu before destroying the combobox
-        comboBox.data[menuIndex].__closeMenu()
+        comboBox.data[menuIndex].__closeAndDestroy()
         verify(!comboBox.data[menuIndex].__popupVisible)
 
         comboBox.destroy()
@@ -550,7 +550,7 @@ TestCase {
                 verify(comboBox.data[menuIndex].items[i].checked)
         }
         // close the menu before destroying the combobox
-        comboBox.data[menuIndex].__closeMenu()
+        comboBox.data[menuIndex].__closeAndDestroy()
         verify(!comboBox.data[menuIndex].__popupVisible)
         comboBox.destroy()
     }