text: #include <aboutwindow.h>
  #include <convertgui.h>
  #include <ui_aboutwindow.h>
  #include <qpushbutton.h>
  #include <qmetaobject.h>
  #include <qobject.h>
  
  AboutWindow::AboutWindow(QWidget *parent) : QWidget(parent), win(new Ui::AboutWindow)
  {
      win->setupUi(this);
      connect(win->btnCloseAw, &QPushButton::clicked, [=] {
          close();
      });
  }
  
  AboutWindow::~AboutWindow()
  {
      delete win;
  }
  
  AboutWindow* AboutWindow::instance = 0;
  
  AboutWindow* AboutWindow::openWindow() {
      if(!instance) {
          instance = new AboutWindow();
          return instance;
      } else {
          return instance;
      }
  }
  