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Qt Platform Abstraction

The Qt Platform Abstraction (QPA) is the main platform abstraction layer in Qt.

The API can be identified by the QPlatform* class prefix, and is used for implementing higher level classes typically found in Qt GUI, e.g. QPlatformWindow for window system integration exposed through QWindow, or QPlatformTheme for deeper platform theming and integration, exposed through QStyleHint and QStyle.

There are no source or binary compatibility guarantees for the QPA classes, meaning that the API 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.)

API Overview

Window system integration
- QPlatformIntegration
- QPlatformAccessibility
- QPlatformBackingStore
- QPlatformClipboard
- QPlatformCursor
- QPlatformDrag
- QPlatformFontDatabase
- QPlatformGraphicsBuffer
- QPlatformInputContext
- QPlatformOffscreenSurface
- QPlatformOpenGLContext
- QPlatformScreen
- QPlatformServices
- QPlatformSharedGraphicsCache
- QPlatformSurface
- QPlatformWindow
Style/theming
- QPlatformTheme
- platform palettes
- platform fonts
- theme hints
Native dialogs and menus
- QPlatformDialogHelper
- QPlatformMenu
- QPlatformMenuBar
- QPlatformMenuItem

Note: In addition to the QPA APIs, there are many other platform abstractions in Qt, for example the event dispatcher abstractions in Qt Core and the rendering hardware abstractions in RHI. The QPA APIs are mostly focused on window system integration and related support.

QPA Plugins

Concrete implementations of the interfaces listed above live in QPA plugins, or platform plugins, adding support for the various platforms Qt runs on. QPA plugins are implemented by subclassing the QPlatform* classes.

The following table summarizes the platform plugins available:

Plugin Name	Plugin Class Name	Description
`qandroid`	QAndroidPlatformIntegration	Android support
`qbsdfb`	QBsdFbIntegration	BsdFb support
`qcocoa`	QCocoaIntegrationPlugin	macOS 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.
`qvnc`	QVncIntegration	VNC support
`qwayland`	QWaylandIntegrationPlugin QWaylandBrcmEglPlatformIntegrationPlugin QWaylandEglPlatformIntegrationPlugin QWaylandXCompositeEglPlatformIntegrationPlugin QWaylandXCompositeGlxPlatformIntegrationPlugin	Wayland support
`qwindows`	QWindowsIntegrationPlugin	Windows support
`qxcb`	QXcbIntegrationPlugin	X Window System (X11) support

Writing a QPA plugin

There is no detailed tutorial documentation for writing QPA plugins at this time. However, there are two minimal plugins shipped with Qt 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.