QT 为实现支持多平台，实现如下类虚函数
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.