Reduce open and stat system calls for QSettings

The patch moves the global static QSettings object
from QLibrary to QCoreApplication and reduces a
few stat and open calls.

Without the patch, a large Trolltech.conf was
pushed out of the unused settings cache during
startup, meaning Trolltech.conf was parsed
more than once.

Reviewed-by: Liang Qi

2 files changed, 14 insertions, 0 deletions

diff --git a/src/corelib/kernel/qcoreapplication.cpp b/src/corelib/kernel/qcoreapplication.cpp
index be86c58..df8bc59 100644
--- a/src/corelib/kernel/qcoreapplication.cpp
+++ b/src/corelib/kernel/qcoreapplication.cpp
@@ -270,6 +270,8 @@ bool QCoreApplicationPrivate::is_app_closing = false;
 Q_CORE_EXPORT bool qt_locale_initialized = false;
 
 
+QSettings *QCoreApplicationPrivate::trolltechConf = 0;
+
 Q_CORE_EXPORT uint qGlobalPostedEventsCount()
 {
     QThreadData *currentThreadData = QThreadData::current();
@@ -371,6 +373,9 @@ QCoreApplicationPrivate::~QCoreApplicationPrivate()
         threadData->postEventList.recursion = 0;
         threadData->quitNow = false;
     }
+
+    delete trolltechConf;
+    trolltechConf = 0;
 }
 
 void QCoreApplicationPrivate::createEventDispatcher()
@@ -688,6 +693,13 @@ void QCoreApplication::init()
     }
 #endif
 
+
+    /*
+      Create an instance of Trolltech.conf. This ensures that the settings will not
+      be thrown out of QSetting's cache for unused settings.
+      */
+    d->trolltechConf = new QSettings(QSettings::UserScope, QLatin1String("Trolltech"));
+
     qt_startup_hook();
 }
 
diff --git a/src/corelib/kernel/qcoreapplication_p.h b/src/corelib/kernel/qcoreapplication_p.h
index add2a35..0557f83 100644
--- a/src/corelib/kernel/qcoreapplication_p.h
+++ b/src/corelib/kernel/qcoreapplication_p.h
@@ -55,6 +55,7 @@
 
 #include "QtCore/qcoreapplication.h"
 #include "QtCore/qtranslator.h"
+#include "QtCore/qsettings.h"
 #include "private/qobject_p.h"
 
 #ifdef Q_OS_SYMBIAN
@@ -139,6 +140,7 @@ public:
 #if defined(QT3_SUPPORT)
     static bool useQt3Support;
 #endif
+    static QSettings *trolltechConf;
 };
 
 QT_END_NAMESPACE