add Qt viewport

app/gcompose/src/MainWindow.h

@@ -0,0 +1,25 @@
+#ifndef MAINWINDOW_H
+#define MAINWINDOW_H
+
+#include <QMainWindow>
+#include <QVTKOpenGLNativeWidget.h>
+
+namespace uLib {
+namespace Vtk {
+class QViewport;
+}
+}
+
+class MainWindow : public QMainWindow {
+    Q_OBJECT
+public:
+    MainWindow(QWidget* parent = nullptr);
+    virtual ~MainWindow();
+
+    uLib::Vtk::QViewport* getViewport() { return m_viewport; }
+
+private:
+    uLib::Vtk::QViewport* m_viewport;
+};
+
+#endif