QGoodWindow is a border less window for Microsoft Windows OS, it's easy to implement and maintain across other OSes like Android and Linux desktops, where the border less window are unavailable.
QGoodWindow inherits from QMainWindow, then just set the central widget likely you do in QMainWindow class and it's sub classes, however, when showing a modal dialog, you must pass QWidget *parentForModal(); function as a parent instead the QGoodWindow instance itself, also you need to draw the title bar yourself, as a part of centralWidget, on other OSes than Windows the native title bar is used! If you're working on a cross platform project you need to differentiate Windows, where you draw the title bar, and others OSes where you don't!
To use QGoodWindow in your project add include(path_to/QGoodWindowFiles/QGoodWindowFiles.pri) in your .pro file, #include <QGoodWindow> in your code, then use QGoodWindow as QMainWindow, for example, create an instance of QGoodWindow or sub class it. To see this project in action, see the demos that comes with it!