macOS: Add support for context menu keyboard hotkey

macOS 15 introduced the ability to trigger context menus via a keyboard
hotkey (Ctrl+Return by default). We now catch this hotkey, propagate it
as a normal key event first (in case the application wants to handle it
by itself), and trigger a QContextMenuEvent if the system determines that
the action should result in a context menu.

[ChangeLog][macOS] The context menu keyboard hotkey available on macOS
15 is now propagated as a QContextMenuEvent if the corresponding
QKeyEvent is not accepted.

Task-number: QTBUG-67331
Change-Id: I3a64a9a18d2caf767fc32637d314a06465aae88f
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
(cherry picked from commit e7c8c2ccc859f8083fb3bf442647b0a315cf1b60)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/plugins/platforms/cocoa/qnsview_keys.mm

@@ -250,6 +250,25 @@ static bool sendAsShortcut(const KeyEvent &keyEvent, QWindow *window)
     }
 }
 
+#if QT_MACOS_PLATFORM_SDK_EQUAL_OR_ABOVE(150000)
+- (void)contextMenuKeyDown:(NSEvent *)nsevent
+{
+    qCDebug(lcQpaKeys) << "Handling context menu key down for" << nsevent;
+
+    if ([self isTransparentForUserInput])
+        return [super contextMenuKeyDown:nsevent];
+
+    if ([self handleKeyEvent:nsevent]) {
+        qCDebug(lcQpaKeys) << "Accepted context menu event as regular key down";
+        m_acceptedKeyDowns.insert(nsevent.keyCode);
+    } else {
+        // Forward up the responder chain to trigger default system
+        // behavior of calling showContextMenuForSelection.
+        [super contextMenuKeyDown:nsevent];
+    }
+}
+#endif
+
 @end
 
 // -------------------------------------------------------------------------

src/plugins/platforms/cocoa/qnsview_menus.mm

@@ -39,6 +39,43 @@
     return [super supplementalTargetForAction:action sender:sender];
 }
 
+#if QT_MACOS_PLATFORM_SDK_EQUAL_OR_ABOVE(150000)
+- (void)showContextMenuForSelection:(id)sender
+{
+    QPointF windowPoint;
+    QPointF screenPoint;
+    [self convertFromScreen:[NSEvent mouseLocation]
+        toWindowPoint:&windowPoint andScreenPoint:&screenPoint];
+
+    auto *keyMapper = QCocoaIntegration::instance()->keyMapper();
+    auto keyboardModifiers = keyMapper->queryKeyboardModifiers();
+
+    // We currently propagate this as QContextMenuEvent::Reason::Keyboard,
+    // but we can also get here via an accessibility ShowMenu action, in
+    // which case QContextMenuEvent::Reason::Other reason might fit better.
+    // Unfortunately QWSI/QGuiApplication/QWidgetWindow doesn't handle that
+    // yet. FIXME: Teach other parts of Qt about QContextMenuEvent::Other.
+    const bool mouseTriggered = false;
+
+    qCDebug(lcQpaMenus) << "Initiating context menu at"
+        << windowPoint.toPoint() << "in" << m_platformWindow
+        << "with" << keyboardModifiers;
+
+    bool accepted = QWindowSystemInterface::handleContextMenuEvent<
+        QWindowSystemInterface::SynchronousDelivery>(
+        m_platformWindow->window(), mouseTriggered,
+        windowPoint.toPoint(), screenPoint.toPoint(),
+        keyboardModifiers);
+
+    qCDebug(lcQpaMenus) << "Context menu event accepted =" << accepted;
+
+    // If the view does not support a context menu we should pass
+    // the request up the responder chain.
+    if (!accepted)
+        [[self nextResponder] tryToPerform:_cmd with:sender];
+}
+#endif
+
 @end
 
 @interface QNSViewMenuHelper ()