Add a function to QMetaObject to check for inheritance

This is analogous to QObject::inherits() but only requires the
metaobjects rather than pointers to a QObject instances. This is needed
for type checking on the backend of Qt 3D where we do not have access
to QObject pointers.

Change-Id: I14d26c4cbb5cc3fbecb57725f2c14ee0ffda4a11
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>
Reviewed-by: Milian Wolff <milian.wolff@kdab.com>
Reviewed-by: Lars Knoll <lars.knoll@theqtcompany.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/src/corelib/kernel/qmetaobject.cpp b/src/corelib/kernel/qmetaobject.cpp
index 1c426225a5..8024c97373 100644
--- a/src/corelib/kernel/qmetaobject.cpp
+++ b/src/corelib/kernel/qmetaobject.cpp
@@ -325,6 +325,24 @@ const char *QMetaObject::className() const
     \sa className()
 */
 
+/*
+    Returns \c true if the class described by this QMetaObject inherits
+    the type described by \a metaObject; otherwise returns false.
+
+    A type is considered to inherit itself.
+
+    \since 5.7
+*/
+bool QMetaObject::inherits(const QMetaObject *metaObject) const Q_DECL_NOEXCEPT
+{
+    const QMetaObject *m = this;
+    do {
+        if (metaObject == m)
+            return true;
+    } while ((m = m->d.superdata));
+    return false;
+}
+
 /*!
     \internal