QInputMethod: check if focusobject supports the "new" IM function before calling it

We use QMetaObject to invoke the "queryFocusObject" function. But if
the current focus object doesn't implement this function, we get a
"QMetaObject::invokeMethod: No such method" warning.

This patch will add a check if the focus object supports IM queries
before trying to call "queryFocusObject", to avoid the warning.

Task-number: QTBUG-91545
Change-Id: I3aa8bd2d4bf57bd42c2d77ed71174ec4f9951f81
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

1 files changed, 10 insertions, 6 deletions

diff --git a/src/gui/kernel/qinputmethod.cpp b/src/gui/kernel/qinputmethod.cpp
index f5de06aea1..f358cc87fd 100644
--- a/src/gui/kernel/qinputmethod.cpp
+++ b/src/gui/kernel/qinputmethod.cpp
@@ -426,13 +426,17 @@ QVariant QInputMethod::queryFocusObject(Qt::InputMethodQuery query, const QVaria
     if (!focusObject)
         return retval;
 
-    bool newMethodWorks = QMetaObject::invokeMethod(focusObject, "inputMethodQuery",
-                                                    Qt::DirectConnection,
-                                                    Q_RETURN_ARG(QVariant, retval),
-                                                    Q_ARG(Qt::InputMethodQuery, query),
-                                                    Q_ARG(QVariant, argument));
-    if (newMethodWorks)
+    static const char *signature = "inputMethodQuery(Qt::InputMethodQuery,QVariant)";
+    const bool newMethodSupported = focusObject->metaObject()->indexOfMethod(signature) != -1;
+    if (newMethodSupported) {
+        const bool ok = QMetaObject::invokeMethod(focusObject, "inputMethodQuery",
+                                                        Qt::DirectConnection,
+                                                        Q_RETURN_ARG(QVariant, retval),
+                                                        Q_ARG(Qt::InputMethodQuery, query),
+                                                        Q_ARG(QVariant, argument));
+        Q_ASSERT(ok);
         return retval;
+    }
 
     QInputMethodQueryEvent queryEvent(query);
     QCoreApplication::sendEvent(focusObject, &queryEvent);