my_app_imp.h
----------------------------------------------------------
AppWindow::AppWindow(){
    QTextBrowser *b = new QTextBrowser;
    b->setSource(QString("./index.html"));
}

main.cpp
----------------------------------------------------------

#include <QApplication>
#include "my_app_imp.h"

int main(int argc, char *argv[]){
    QApplication app(argc, argv);
    AppWindow *ap = new AppWindow;
    ap->show();
    return app.exec();
}