split imageselector

* image updating in seperate class ImageSwitcher
 * image selection in class ImageSelector

src/imageswitcher.cpp

@@ -0,0 +1,39 @@
+#include "imageswitcher.h"
+#include "imageselector.h"
+#include "mainwindow.h"
+#include <QDirIterator>
+#include <QTimer>
+#include <QApplication>
+#include <QDir>
+#include <iostream>
+#include <stdlib.h>     /* srand, rand */
+#include <time.h>       /* time */
+
+ImageSwitcher::ImageSwitcher(MainWindow& w, unsigned int timeout, const ImageSelector& selector):
+    QObject::QObject(),
+    window(w),
+    timeout(timeout),
+    selector(selector),
+    timer(this)
+{
+}
+
+void ImageSwitcher::updateImage()
+{
+    std::string filename(selector.getNextImage());
+    if (filename == "")
+    {
+      window.warn("No image found.");
+    }
+    else
+    {
+      window.setImage(filename);
+    }
+}
+
+void ImageSwitcher::start()
+{
+    updateImage();
+    connect(&timer, SIGNAL(timeout()), this, SLOT(updateImage()));
+    timer.start(timeout);
+}