implemented fullscreen stretch modes

src/qt/qt_renderercomon.hpp

@@ -0,0 +1,19 @@
+#pragma once
+
+#include <QRect>
+#include <QImage>
+
+class QWidget;
+
+class RendererCommon
+{
+public:
+    RendererCommon();
+
+    void onResize(int width, int height);
+protected:
+    void onPaint(QPaintDevice* device);
+
+    QImage image;
+    QRect source, destination;
+};