QQmlIncubationController Class

详细描述

QQmlIncubationController instances drive the progress of QQmlIncubators

In order to behave asynchronously and not introduce stutters or freezes in an application, the process of creating objects a QQmlIncubators must be driven only during the application's idle time. QQmlIncubationController allows the application to control exactly when, how often and for how long this processing occurs.

A QQmlIncubationController derived instance should be created and set on a QQmlEngine by calling the QQmlEngine::setIncubationController() method. Processing is then controlled by calling the QQmlIncubationController::incubateFor() or QQmlIncubationController::incubateWhile() methods as dictated by the application's requirements.

For example, this is an example of a incubation controller that will incubate for a maximum of 5 milliseconds out of every 16 milliseconds.

  class PeriodicIncubationController : public QObject,
                                       public QQmlIncubationController
  {
  public:
      PeriodicIncubationController() {
          startTimer(16);
      }

  protected:
      void timerEvent(QTimerEvent *) override {
          incubateFor(5);
      }
  };

Although the previous example would work, it is not optimal. Real world incubation controllers should try and maximize the amount of idle time they consume - rather than a static amount like 5 milliseconds - while not disturbing the application.