# Package org.zkoss.zk.ui.impl

- Interface Summary
  Interface | Description
  --- | ---
  UiEngineImpl.Extension | An interface used to extend the UI engine.

- Class Summary
  Class | Description
  --- | ---
  AbortByRemoveDesktop | The aborting reason when the remove-desktop command is received.
  AbortBySendRedirect | The aborting reason for send-redirect.
  AbstractExecution | A skeletal implementation of `Execution`.
  AbstractUiFactory | The skeletal implementation of `UiFactory`.
  AbstractWebApp | A skeletal implementation of `WebApp`.
  Attributes | Attributes used internally for implementation only.
  DesktopImpl | The implementation of `Desktop`.
  DesktopRecycles | Utilities to handle `DesktopRecycle`.
  EventInterceptors | Utilities used to handle `EventInterceptor`.
  EventProcessingThreadImpl | Thread to handle events.
  EventProcessor | A utility class that simplify the implementation of `EventProcessingThread`.
  ExecutionCarryOver | A utility to carry over the execution to a server-push thread.
  GlobalDesktopCacheProvider | A implementation of `DesktopCacheProvider` that stores all desktops from the same Web application into one desktop cache.
  LegacyDesktopIdGenerator | A legacy sequential desktop ID generator used in ZK before 9.6.0.
  MultiComposer<T extends Component> | To proxy a collection of composers.
  NativeHelpers | Utilities for implementing `Native.Helper`.
  PageImpl | An implementation of `Page` and `PageCtrl`.
  PollingServerPush | A server-push implementation that is based on client-polling.
  ProxyEvent | Used to proxy another event.
  RequestInfoImpl | An implementation of `RequestInfo`.
  RequestQueueImpl | An implementation of `RequestQueue` behaving as a queue of `AuRequest`.
  RichletConfigImpl | An implementation of `RichletConfig`.
  ScopeListeners | Utilities to implement `Scope.addScopeListener(org.zkoss.zk.ui.ext.ScopeListener)` and `Scope.removeScopeListener(org.zkoss.zk.ui.ext.ScopeListener)`.
  SessionDesktopCacheProvider | A implementation of `DesktopCacheProvider` that stores all desktops from the same session in one desktop cache.
  SimpleDesktopCache | A simple implementation of `DesktopCache`.
  SimpleScope | A simple implementation of `Scope`.
  StaticIdGenerator | Use this generator will generate fixed uuid for each component.
  SynchronizedScope | A synchronized scope.
  UiEngineExtension | An implementation of `UiEngineImpl.Extension` to extend `UiEngineImpl` to support stubonly and the merging of native
  UiEngineImpl | An implementation of `UiEngine` to create and update components.
  Utils | Utilities to implement ZK.
  VolatilePage | A page that does not really exist at the client.
  ZScriptInitiator | An initiator used to evaluate a zscript file.