Work around a bug in Qt where the wheelScrollLines setting is ignored. Fixes issue 2824.

src/main.cpp

@@ -303,6 +303,17 @@ int main(int argc, char *argv[]) {
   IncreaseFDLimit();
 
   QtSingleApplication a(argc, argv);
+
+  // A bug in Qt means the wheel_scroll_lines setting gets ignored and replaced
+  // with the default value of 3 in QApplicationPrivate::initialize.
+  {
+    QSettings qt_settings(QSettings::UserScope, "Trolltech");
+    qt_settings.beginGroup("Qt");
+    QApplication::setWheelScrollLines(
+          qt_settings.value("wheelScrollLines",
+                            QApplication::wheelScrollLines()).toInt());
+  }
+
 #ifdef Q_OS_DARWIN
   QCoreApplication::setLibraryPaths(
       QStringList() << QCoreApplication::applicationDirPath() + "/../PlugIns");