QCocoaMenu: De-pessimize the number of calls to validateMenuItem:

Calling -[NSMenu update] every time we add a new item can result in
a quadratic behavior since the function itself will iterate over all
the items in the menu. We solve this by using a 0-timer which will
trigger the call to update the next time the event loop spins.

Menurama manual test updated.

Change-Id: Ic155d364515cc93eb81b1c8085c8e44c93799954
Task-number: QTBUG-62396
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

src/plugins/platforms/cocoa/qcocoamenu.h

@@ -96,14 +96,18 @@ public:
     bool isOpen() const;
     void setIsOpen(bool isOpen);
 
+    void timerEvent(QTimerEvent *e) Q_DECL_OVERRIDE;
+
 private:
     QCocoaMenuItem *itemOrNull(int index) const;
     void insertNative(QCocoaMenuItem *item, QCocoaMenuItem *beforeItem);
+    void scheduleUpdate();
 
     QList<QCocoaMenuItem *> m_menuItems;
     NSMenu *m_nativeMenu;
     NSMenuItem *m_attachedItem;
     quintptr m_tag;
+    int m_updateTimer;
     bool m_enabled:1;
     bool m_parentEnabled:1;
     bool m_visible:1;

src/plugins/platforms/cocoa/qcocoamenu.mm

@@ -260,6 +260,7 @@ QT_BEGIN_NAMESPACE
 QCocoaMenu::QCocoaMenu() :
     m_attachedItem(0),
     m_tag(0),
+    m_updateTimer(0),
     m_enabled(true),
     m_parentEnabled(true),
     m_visible(true),
@@ -410,6 +411,20 @@ QCocoaMenuItem *QCocoaMenu::itemOrNull(int index) const
     return m_menuItems.at(index);
 }
 
+void QCocoaMenu::scheduleUpdate()
+{
+    if (!m_updateTimer)
+        m_updateTimer = startTimer(0);
+}
+
+void QCocoaMenu::timerEvent(QTimerEvent *e)
+{
+    if (e->timerId() == m_updateTimer) {
+        m_updateTimer = 0;
+        [m_nativeMenu update];
+    }
+}
+
 void QCocoaMenu::syncMenuItem(QPlatformMenuItem *menuItem)
 {
     QMacAutoReleasePool pool;
@@ -436,9 +451,9 @@ void QCocoaMenu::syncMenuItem(QPlatformMenuItem *menuItem)
         QCocoaMenuItem* beforeItem = itemOrNull(m_menuItems.indexOf(cocoaItem) + 1);
         insertNative(cocoaItem, beforeItem);
     } else {
-        // Force NSMenuValidation to kick in. This is needed e.g.
+        // Schedule NSMenuValidation to kick in. This is needed e.g.
         // when an item's enabled state changes after menuWillOpen:
-        [m_nativeMenu update];
+        scheduleUpdate();
     }
 }
 

tests/manual/cocoa/menurama/mainwindow.cpp

@@ -56,6 +56,19 @@ MainWindow::MainWindow(QWidget *parent) :
     connect(ui->pushButton, &QPushButton::clicked, [=] {
         menuApp->populateMenu(ui->menuOn_Click, true /*clear*/);
     });
+
+    connect(ui->addManyButton, &QPushButton::clicked, [=] {
+        QMenu *menu = new QMenu(QLatin1String("Many More ") +
+                                QString::number(ui->menuBar->actions().count()));
+        ui->menuBar->insertMenu(ui->menuDynamic_Stuff->menuAction(), menu);
+        for (int i = 0; i < 2000; i++) {
+            auto *action = menu->addAction(QLatin1String("Item ") + QString::number(i));
+            if (i & 0x1)
+                action->setEnabled(false);
+            if (i & 0x2)
+                action->setVisible(false);
+        }
+    });
 }
 
 MainWindow::~MainWindow()

tests/manual/cocoa/menurama/mainwindow.ui

@@ -6,50 +6,60 @@
    <rect>
     <x>0</x>
     <y>0</y>
-    <width>429</width>
-    <height>251</height>
+    <width>486</width>
+    <height>288</height>
    </rect>
   </property>
   <property name="windowTitle">
    <string>MainWindow</string>
   </property>
   <widget class="QWidget" name="centralWidget">
-   <layout class="QVBoxLayout" name="verticalLayout_2">
+   <layout class="QVBoxLayout" name="verticalLayout">
     <item>
-     <layout class="QVBoxLayout" name="verticalLayout">
-      <property name="spacing">
-       <number>24</number>
-      </property>
-      <item>
-       <widget class="QLabel" name="label">
-        <property name="text">
-         <string>The &quot;Help&quot; menu should NOT be visible.
+     <widget class="QLabel" name="label">
+      <property name="text">
+       <string>The &quot;Help&quot; menu should NOT be visible.
 
 Click on &quot;Dynamic Stuff&quot; then move left and right to other menus. Disabled items should remain that way.</string>
-        </property>
-        <property name="scaledContents">
-         <bool>false</bool>
-        </property>
-        <property name="alignment">
-         <set>Qt::AlignLeading|Qt::AlignLeft|Qt::AlignTop</set>
-        </property>
-        <property name="wordWrap">
-         <bool>true</bool>
-        </property>
-       </widget>
-      </item>
+      </property>
+      <property name="scaledContents">
+       <bool>false</bool>
+      </property>
+      <property name="alignment">
+       <set>Qt::AlignLeading|Qt::AlignLeft|Qt::AlignTop</set>
+      </property>
+      <property name="wordWrap">
+       <bool>true</bool>
+      </property>
+     </widget>
+    </item>
+    <item>
+     <widget class="QCheckBox" name="checkBox">
+      <property name="text">
+       <string>Enable &quot;Stuff&quot; Menu</string>
+      </property>
+      <property name="checked">
+       <bool>true</bool>
+      </property>
+     </widget>
+    </item>
+    <item>
+     <widget class="QPushButton" name="pushButton">
+      <property name="sizePolicy">
+       <sizepolicy hsizetype="Maximum" vsizetype="Fixed">
+        <horstretch>0</horstretch>
+        <verstretch>0</verstretch>
+       </sizepolicy>
+      </property>
+      <property name="text">
+       <string>Populate Dynamic Submenu</string>
+      </property>
+     </widget>
+    </item>
+    <item>
+     <layout class="QHBoxLayout" name="horizontalLayout">
       <item>
-       <widget class="QCheckBox" name="checkBox">
-        <property name="text">
-         <string>Enable &quot;Stuff&quot; Menu</string>
-        </property>
-        <property name="checked">
-         <bool>true</bool>
-        </property>
-       </widget>
-      </item>
-      <item>
-       <widget class="QPushButton" name="pushButton">
+       <widget class="QPushButton" name="addManyButton">
         <property name="sizePolicy">
          <sizepolicy hsizetype="Maximum" vsizetype="Fixed">
           <horstretch>0</horstretch>
@@ -57,7 +67,17 @@ Click on &quot;Dynamic Stuff&quot; then move left and right to other menus. Disa
          </sizepolicy>
         </property>
         <property name="text">
-         <string>Populate Dynamic Submenu</string>
+         <string>Add Many Items</string>
+        </property>
+       </widget>
+      </item>
+      <item>
+       <widget class="QLabel" name="label_2">
+        <property name="text">
+         <string>Adding hundreds of items should not block the UI for noticeable periods of time. Odd numbered items should be disabled, those with 2nd LSB on should be hidden.</string>
+        </property>
+        <property name="wordWrap">
+         <bool>true</bool>
         </property>
        </widget>
       </item>
@@ -70,7 +90,7 @@ Click on &quot;Dynamic Stuff&quot; then move left and right to other menus. Disa
     <rect>
      <x>0</x>
      <y>0</y>
-     <width>429</width>
+     <width>486</width>
      <height>22</height>
     </rect>
    </property>