QWindow

QWindow is a class in the Qt multimedia and windowing framework that represents an independently renderable window. It provides the foundation for Qt's windowing system and is designed to handle low‑level window operations such as positioning, resizing, and visibility control. Unlike QWidget, which is built on top of the QWindow class and is used for creating widget‑based user interfaces, QWindow operates directly with the platform’s native window protocols, making it suitable for high‑performance graphics, video playback, and OpenGL/Qt Quick rendering.

Instances of QWindow construct a native window via the underlying operating system’s windowing API (such as X11, Wayland, macOS Cocoa, or Windows GDI). The class offers signals like geometryChanged, visibilityChanged, and exposeChanged to expose window state changes to other parts of an application. It also supports event handling through its virtual event methods, allowing developers to override methods such as exposeEvent, resizeEvent, and keyPressEvent. QWindow can be shown using the show() method or setVisible(true), and can be hidden with setVisible(false).

Qt Quick applications often use QWindow indirectly: a QQuickWindow, which inherits from QWindow, adds support for rendering Qt Quick QML scenes. Similarly, QOpenGLWindow inherits QWindow to provide an OpenGL context. The design of QWindow separates low‑level window handling from the higher‑level visual components, enabling developers to use a single window class across multiple GUI frameworks while maintaining efficient rendering pipelines.