Cocoa Menus: Allow separators in app menu

We extend QCocoaNSMenuItem with separator items capabilities
and use it as any other custom item in the app menu.

Addition and removal of items in the app menu remains very
basic because that menu doesn't exist as such. Instead, it's
hinted through the QAction's menu role.

Change-Id: Ia13bfcc008c75e49fd21705d2528da5a85ed1c73
Task-number: QTBUG-63756
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

src/plugins/platforms/cocoa/qcocoamenu.mm

@@ -205,7 +205,7 @@ void QCocoaMenu::removeMenuItem(QPlatformMenuItem *menuItem)
 QCocoaMenuItem *QCocoaMenu::itemOrNull(int index) const
 {
     if ((index < 0) || (index >= m_menuItems.size()))
-        return 0;
+        return nullptr;
 
     return m_menuItems.at(index);
 }

src/plugins/platforms/cocoa/qcocoamenuitem.mm

@@ -219,12 +219,11 @@ void QCocoaMenuItem::setNativeContents(WId item)
 
 NSMenuItem *QCocoaMenuItem::sync()
 {
-    if (m_isSeparator != [m_native isSeparatorItem]) {
+    if (m_isSeparator != m_native.separatorItem) {
         [m_native release];
-        if (m_isSeparator) {
-            m_native = [[NSMenuItem separatorItem] retain];
-            [m_native setTag:reinterpret_cast<NSInteger>(this)];
-        } else
+        if (m_isSeparator)
+            m_native = [[QCocoaNSMenuItem separatorItemWithPlatformMenuItem:this] retain];
+        else
             m_native = nil;
     }
 
@@ -435,6 +434,9 @@ void QCocoaMenuItem::setIconSize(int size)
 
 void QCocoaMenuItem::resolveTargetAction()
 {
+    if (m_native.separatorItem)
+        return;
+
     // Some items created by QCocoaMenuLoader are not
     // instances of QCocoaNSMenuItem and have their
     // target/action set as Interface Builder would.

src/plugins/platforms/cocoa/qcocoamenuloader.mm

@@ -272,18 +272,21 @@
 
 - (NSMenuItem *)appSpecificMenuItem:(QCocoaMenuItem *)platformItem
 {
+    // No reason to create the item if it already exists.
     for (NSMenuItem *item in appMenu.itemArray)
         if ([item isMemberOfClass:[QCocoaNSMenuItem class]]
-            && static_cast<QCocoaNSMenuItem *>(item).platformMenuItem == platformItem) {
-            // No reason to create the item if it already exists.
+            && static_cast<QCocoaNSMenuItem *>(item).platformMenuItem == platformItem)
             return [[item retain] autorelease];
-        }
 
     // Create an App-Specific menu item, insert it into the menu and return
     // it as an autorelease item.
-    QCocoaNSMenuItem *item = [[QCocoaNSMenuItem alloc] initWithPlatformMenuItem:platformItem];
+    QCocoaNSMenuItem *item;
+    if (platformItem->isSeparator())
+        item = [[QCocoaNSMenuItem separatorItemWithPlatformMenuItem:platformItem] retain];
+    else
+        item = [[QCocoaNSMenuItem alloc] initWithPlatformMenuItem:platformItem];
 
-    NSInteger location = [appMenu indexOfItem:lastAppSpecificItem];
+    const auto location = [appMenu indexOfItem:lastAppSpecificItem];
 
     if (!lastAppSpecificItem.separatorItem)
         [lastAppSpecificItem release];

src/plugins/platforms/cocoa/qcocoansmenu.h

@@ -80,6 +80,7 @@ QT_FORWARD_DECLARE_CLASS(QCocoaMenuItem);
 
 @property (nonatomic) QCocoaMenuItem *platformMenuItem;
 
++ (instancetype)separatorItemWithPlatformMenuItem:(QCocoaMenuItem *)menuItem;
 - (instancetype)initWithPlatformMenuItem:(QCocoaMenuItem *)menuItem;
 
 @end

src/plugins/platforms/cocoa/qcocoansmenu.mm

@@ -97,6 +97,19 @@ static NSString *qt_mac_removePrivateUnicode(NSString* string)
     QPointer<QCocoaMenuItem> _platformMenuItem;
 }
 
++ (instancetype)separatorItemWithPlatformMenuItem:(QCocoaMenuItem *)menuItem
+{
+    // Safe because +[NSMenuItem separatorItem] invokes [[self alloc] init]
+    auto *item = static_cast<QCocoaNSMenuItem *>([self separatorItem]);
+    Q_ASSERT_X([item isMemberOfClass:[QCocoaNSMenuItem class]],
+               qPrintable(__FUNCTION__),
+               "Did +[NSMenuItem separatorItem] not invoke [[self alloc] init]?");
+    if (item)
+        item.platformMenuItem = menuItem;
+
+    return item;
+}
+
 - (instancetype)initWithPlatformMenuItem:(QCocoaMenuItem *)menuItem
 {
     if ((self = [super initWithTitle:@"" action:nil keyEquivalent:@""])) {