Qt Platform Abstraction | Qt 5.15

- Qt 5.15
- Qt Platform Abstraction
- Qt 5.15.19 Reference Documentation

# Qt Platform Abstraction

The Qt Platform Abstraction (QPA) is the platform abstraction layer for Qt 5 and replaces Qt for Embedded Linux and the platform ports from Qt 4.

QPA plugins are implemented by subclassing various `QPlatform*` classes. There are several root classes, such as `QPlatformIntegration` and `QPlatformWindow` for window system integration and `QPlatformTheme` for deeper platform theming and integration. QStyle is not a part of QPA.

There are no source or binary compatibility guarantees for the QPA classes, meaning that a platform plugin is only guaranteed to work with the Qt version it was developed against. API changes will however only be made in minor releases. (5.1, 5.2, and so on.)

## QPA Minimal Plugins

There is no detailed tutorial documentation for writing QPA plugins at this time. However, there are two minimal plugins shipped with Qt 5 for testing and other special purposes that you can use as examples:

- `qtbase/src/plugins/platforms/minimal/`
- `qtbase/src/plugins/platforms/minimalegl/`

The `qminimal` plugin is used for tools that link against Qt GUI, but do not require window system integration (for example, `qmlplugindump`). It also has diagnostic support for dumping window contents to image files as determined by environment variables.

## Class Overview

- QPlatformIntegration
  - QAbstractEventDispatcher
  - QPlatformAccessibility
  - QPlatformBackingStore
  - QPlatformClipboard
  - QPlatformCursor
  - QPlatformDrag
  - QPlatformFontDatabase
  - QPlatformGraphicsBuffer
  - QPlatformInputContext
  - QPlatformNativeInterface
  - QPlatformOffscreenSurface
  - QPlatformOpenGLContext
  - QPlatformScreen
  - QPlatformServices
  - QPlatformSharedGraphicsCache
  - QPlatformSurface
  - QPlatformWindow
- QPlatformTheme
  - QPlatformDialogHelper
  - QPlatformMenu
  - QPlatformMenuBar
  - QPlatformMenuItem
  - QPlatformSystemTrayIcon
  - platform palettes
  - platform fonts
  - theme hints

`qtbase/src/platformsupport` contains several helper classes for implementing platform plugins on Unix-like systems.

## QPA Plugins

The following table summarizes the platform plugins available for QPA:

Plugin Name | Plugin Class Name | Description
--- | --- | ---
`qandroid` | QAndroidPlatformIntegration | Android support
`qbsdfb` | QBsdFbIntegration | BsdFb support
`qcocoa` | QCocoaIntegrationPlugin | Cocoa support
`qdirect2d` | QWindowsDirect2DIntegrationPlugin | Similar to the `qwindows` plugin, but replaces the raster paint engine with a Direct2D-based paint engine for QPixmap and QBackingStore.
`qdirectfb` | QDirectFbIntegrationPlugin | DirectFB is centered around surfaces, which are the equivalent of a QPaintDevice.
`qeglfs` | QEglFSIntegrationPlugin | EGLFS support for embedded Linux devices.
`qhaiku` | QHaikuIntegration | Haiku support
`qios` | QIOSIntegrationPlugin | iOS support
`qlinuxfb` | QLinuxFbIntegrationPlugin | LinuxFB support for embedded Linux devices.
`qmirclient` | QMirClientIntegration | Mir client support
`qopenwf` | QOpenWFDIntegrationPlugin | OpenWF Display support for managing display control hardware.
`qqnx` | QQnxIntegrationPlugin | QNX support
`qvnc` | QVncIntegration | VNC support
`qwasm` | QWasmIntegration | WebAssembly support
`qwayland` | QWaylandIntegrationPlugin QWaylandBrcmEglPlatformIntegrationPlugin QWaylandEglPlatformIntegrationPlugin QWaylandXCompositeEglPlatformIntegrationPlugin QWaylandXCompositeGlxPlatformIntegrationPlugin | Wayland support
`qwindows` | QWindowsIntegrationPlugin | Windows support
`qwinrt` | QWinRTIntegrationPlugin | Universal Windows Platform (UWP) support Note: This plugin was originally written for WinRT (Windows Runtime), and is therefore called `qwinrt`.
`qxcb` | QXcbIntegrationPlugin | X Window System (X11) support
`webgl` | QWebGLIntegrationPlugin | WebGL support for Qt Quick applications