Optimize: Do not repeat method lookup on every scene change event.

Instead, cache the QMetaMethod lookup once and invoke it directly
in all subsequent calls to QPostMan::sceneChangeEvent.

Profiling showed me that QMetaObject::indexOfMethod took up ca.
8% of the total CPU time. This hotspot is now removed.

Change-Id: Id36d824900cc892fc98e5bd32880bfe6aae47341
Reviewed-by: Paul Lemire <paul.lemire@kdab.com>
Reviewed-by: Sean Harmer <sean.harmer@kdab.com>

1 files changed, 9 insertions, 3 deletions

diff --git a/src/core/qpostman.cpp b/src/core/qpostman.cpp
index 027a372a3..8f6201669 100644
--- a/src/core/qpostman.cpp
+++ b/src/core/qpostman.cpp
@@ -77,11 +77,17 @@ void QPostman::setScene(QSceneInterface *scene)
     d->m_scene = scene;
 }
 
+static inline QMetaMethod notifyFrontendNodeMethod()
+{
+    int idx = QPostman::staticMetaObject.indexOfMethod("notifyFrontendNode(QSceneChangePtr)");
+    Q_ASSERT(idx != -1);
+    return QPostman::staticMetaObject.method(idx);
+}
+
 void QPostman::sceneChangeEvent(const QSceneChangePtr &e)
 {
-    QMetaObject::invokeMethod(this,
-                              "notifyFrontendNode",
-                              Q_ARG(QSceneChangePtr, e));
+    static const QMetaMethod notifyFrontendNode = notifyFrontendNodeMethod();
+    notifyFrontendNode.invoke(this, Q_ARG(QSceneChangePtr, e));
 }
 
 void QPostman::notifyFrontendNode(QSceneChangePtr e)