QQmlProperty: Accept badly capitalized signal handler names

... but warn about them. Apparently we did accept them prior to 6.4.

Fixes: QTBUG-116576
Pick-to: 6.5 6.6
Change-Id: If890db85f5a8d71c0bcdfaf646ee9f01765a0b3c
Reviewed-by: Sami Shalayel <sami.shalayel@qt.io>

2 files changed, 22 insertions, 0 deletions

diff --git a/src/qml/common/qqmlsignalnames.cpp b/src/qml/common/qqmlsignalnames.cpp
index e66c26d4e2..d2a23205a6 100644
--- a/src/qml/common/qqmlsignalnames.cpp
+++ b/src/qml/common/qqmlsignalnames.cpp
@@ -191,6 +191,25 @@ std::optional<QString> QQmlSignalNames::handlerNameToSignalName(QStringView hand
 
 /*!
 \internal
+Returns a signal name from \a handlerName string. Do not use it on changed handlers, see
+changedHandlerNameToSignalName for that! Accepts improperly capitalized handler names and
+incorrectly resolves signal names that start with '_' or '$'.
+*/
+std::optional<QString> QQmlSignalNames::badHandlerNameToSignalName(QStringView handler)
+{
+    if (handler.size() <= StrlenOn || !handler.startsWith(On))
+        return {};
+
+    QString signalName = handler.sliced(StrlenOn).toString();
+
+    // This is quite wrong. But we need it for backwards compatibility.
+    signalName.front() = signalName.front().toLower();
+
+    return signalName;
+}
+
+/*!
+\internal
 Returns a signal name from \a changedHandlerName string. Makes sure not to lowercase the 'C' from
 Changed.
 */
diff --git a/src/qml/common/qqmlsignalnames_p.h b/src/qml/common/qqmlsignalnames_p.h
index 753f2ca97a..9c3d192666 100644
--- a/src/qml/common/qqmlsignalnames_p.h
+++ b/src/qml/common/qqmlsignalnames_p.h
@@ -49,6 +49,9 @@ public:
     static bool isHandlerName(QStringView signalName);
 
     static QString addPrefixToPropertyName(QStringView prefix, QStringView propertyName);
+
+    // ### Qt7: remove this
+    static std::optional<QString> badHandlerNameToSignalName(QStringView handler);
 };
 
 QT_END_NAMESPACE