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42 #include "qqmlincubator.h"
43 #include "qqmlcomponent.h"
44 #include "qqmlincubator_p.h"
46 #include "qqmlcompiler_p.h"
47 #include "qqmlexpression_p.h"
50 // - check that the Component.onCompleted behavior is the same as 4.8 in the synchronous and
51 // async if nested cases
52 void QQmlEnginePrivate::incubate(QQmlIncubator &i, QQmlContextData *forContext)
54 QQmlIncubatorPrivate *p = i.d;
56 QQmlIncubator::IncubationMode mode = i.incubationMode();
58 if (!incubationController)
59 mode = QQmlIncubator::Synchronous;
61 if (mode == QQmlIncubator::AsynchronousIfNested) {
62 mode = QQmlIncubator::Synchronous;
64 // Need to find the first constructing context and see if it is asynchronous
65 QQmlIncubatorPrivate *parentIncubator = 0;
66 QQmlContextData *cctxt = forContext;
68 if (cctxt->activeVMEData) {
69 parentIncubator = (QQmlIncubatorPrivate *)cctxt->activeVMEData;
72 cctxt = cctxt->parent;
75 if (parentIncubator && parentIncubator->isAsynchronous) {
76 mode = QQmlIncubator::Asynchronous;
77 p->waitingOnMe = parentIncubator;
78 parentIncubator->waitingFor.insert(p);
82 p->isAsynchronous = (mode != QQmlIncubator::Synchronous);
84 inProgressCreations++;
86 if (mode == QQmlIncubator::Synchronous) {
87 typedef QQmlIncubatorPrivate IP;
88 QRecursionWatcher<IP, &IP::recursion> watcher(p);
90 p->changeStatus(QQmlIncubator::Loading);
92 if (!watcher.hasRecursed()) {
97 incubatorList.insert(p);
100 p->vmeGuard.guard(&p->vme);
101 p->changeStatus(QQmlIncubator::Loading);
103 if (incubationController)
104 incubationController->incubatingObjectCountChanged(incubatorCount);
109 Sets the engine's incubation \a controller. The engine can only have one active controller
110 and it does not take ownership of it.
112 \sa incubationController()
114 void QQmlEngine::setIncubationController(QQmlIncubationController *controller)
117 if (d->incubationController)
118 d->incubationController->d = 0;
119 d->incubationController = controller;
120 if (controller) controller->d = d;
124 Returns the currently set incubation controller, or 0 if no controller has been set.
126 \sa setIncubationController()
128 QQmlIncubationController *QQmlEngine::incubationController() const
130 Q_D(const QQmlEngine);
131 return d->incubationController;
134 QQmlIncubatorPrivate::QQmlIncubatorPrivate(QQmlIncubator *q,
135 QQmlIncubator::IncubationMode m)
136 : q(q), status(QQmlIncubator::Null), mode(m), isAsynchronous(false), progress(Execute),
137 result(0), component(0), vme(this), waitingOnMe(0)
141 QQmlIncubatorPrivate::~QQmlIncubatorPrivate()
145 void QQmlIncubatorPrivate::clear()
147 if (next.isInList()) {
150 QQmlEnginePrivate *enginePriv = QQmlEnginePrivate::get(component->engine);
151 component->release();
153 enginePriv->incubatorCount--;
154 QQmlIncubationController *controller = enginePriv->incubationController;
156 controller->incubatingObjectCountChanged(enginePriv->incubatorCount);
157 } else if (component) {
158 component->release();
161 if (!rootContext.isNull()) {
162 rootContext->activeVMEData = 0;
166 if (nextWaitingFor.isInList()) {
167 Q_ASSERT(waitingOnMe);
168 nextWaitingFor.remove();
174 \class QQmlIncubationController
175 \brief QQmlIncubationController instances drive the progress of QQmlIncubators
177 In order to behave asynchronously and not introduce stutters or freezes in an application,
178 the process of creating objects a QQmlIncubators must be driven only during the
179 application's idle time. QQmlIncubationController allows the application to control
180 exactly when, how often and for how long this processing occurs.
182 A QQmlIncubationController derived instance should be created and set on a
183 QQmlEngine by calling the QQmlEngine::setIncubationController() method.
184 Processing is then controlled by calling the QQmlIncubationController::incubateFor()
185 or QQmlIncubationController::incubateWhile() methods as dictated by the application's
188 For example, this is an example of a incubation controller that will incubate for a maximum
189 of 5 milliseconds out of every 16 milliseconds.
192 class PeriodicIncubationController : public QObject,
193 public QQmlIncubationController
196 PeriodicIncubationController() {
201 virtual void timerEvent(QTimerEvent *) {
207 Although the previous example would work, it is not optimal. Real world incubation
208 controllers should try and maximize the amount of idle time they consume - rather
209 than a static amount like 5 milliseconds - while not disturbing the application.
213 Create a new incubation controller.
215 QQmlIncubationController::QQmlIncubationController()
221 QQmlIncubationController::~QQmlIncubationController()
223 if (d) QQmlEnginePrivate::get(d)->setIncubationController(0);
228 Return the QQmlEngine this incubation controller is set on, or 0 if it
229 has not been set on any engine.
231 QQmlEngine *QQmlIncubationController::engine() const
233 return QQmlEnginePrivate::get(d);
237 Return the number of objects currently incubating.
239 int QQmlIncubationController::incubatingObjectCount() const
242 return d->incubatorCount;
248 Called when the number of incubating objects changes. \a incubatingObjectCount is the
249 new number of incubating objects.
251 The default implementation does nothing.
253 void QQmlIncubationController::incubatingObjectCountChanged(int incubatingObjectCount)
255 Q_UNUSED(incubatingObjectCount);
258 void QQmlIncubatorPrivate::incubate(QQmlVME::Interrupt &i)
262 typedef QQmlIncubatorPrivate IP;
263 QRecursionWatcher<IP, &IP::recursion> watcher(this);
265 QQmlEngine *engine = component->engine;
266 QQmlEnginePrivate *enginePriv = QQmlEnginePrivate::get(engine);
268 bool guardOk = vmeGuard.isOK();
273 error.setUrl(component->url);
274 error.setDescription(QQmlComponent::tr("Object destroyed during incubation"));
276 progress = QQmlIncubatorPrivate::Completed;
281 if (progress == QQmlIncubatorPrivate::Execute) {
282 enginePriv->referenceScarceResources();
283 QObject *tresult = vme.execute(&errors, i);
284 enginePriv->dereferenceScarceResources();
286 if (watcher.hasRecursed())
290 if (errors.isEmpty() && result == 0)
294 QQmlData *ddata = QQmlData::get(result);
296 ddata->indestructible = true;
298 q->setInitialState(result);
301 if (watcher.hasRecursed())
304 if (errors.isEmpty())
305 progress = QQmlIncubatorPrivate::Completing;
307 progress = QQmlIncubatorPrivate::Completed;
309 changeStatus(calculateStatus());
311 if (watcher.hasRecursed())
314 if (i.shouldInterrupt())
318 if (progress == QQmlIncubatorPrivate::Completing) {
320 if (watcher.hasRecursed())
323 QQmlContextData *ctxt = vme.complete(i);
326 progress = QQmlIncubatorPrivate::Completed;
329 } while (!i.shouldInterrupt());
333 if (progress == QQmlIncubatorPrivate::Completed && waitingFor.isEmpty()) {
334 typedef QQmlIncubatorPrivate IP;
336 QQmlIncubatorPrivate *isWaiting = waitingOnMe;
340 QRecursionWatcher<IP, &IP::recursion> watcher(isWaiting);
341 changeStatus(calculateStatus());
342 if (!watcher.hasRecursed())
343 isWaiting->incubate(i);
345 changeStatus(calculateStatus());
348 enginePriv->inProgressCreations--;
350 if (0 == enginePriv->inProgressCreations) {
351 while (enginePriv->erroredBindings) {
352 enginePriv->warning(enginePriv->erroredBindings->error);
353 enginePriv->erroredBindings->removeError();
357 vmeGuard.guard(&vme);
362 Incubate objects for \a msecs, or until there are no more objects to incubate.
364 void QQmlIncubationController::incubateFor(int msecs)
366 if (!d || d->incubatorCount == 0)
369 QQmlVME::Interrupt i(msecs * 1000000);
372 QQmlIncubatorPrivate *p = (QQmlIncubatorPrivate*)d->incubatorList.first();
374 } while (d && d->incubatorCount != 0 && !i.shouldInterrupt());
378 Incubate objects while the bool pointed to by \a flag is true, or until there are no
379 more objects to incubate, or up to msecs if msecs is not zero.
381 Generally this method is used in conjunction with a thread or a UNIX signal that sets
382 the bool pointed to by \a flag to false when it wants incubation to be interrupted.
384 void QQmlIncubationController::incubateWhile(volatile bool *flag, int msecs)
386 if (!d || d->incubatorCount == 0)
389 QQmlVME::Interrupt i(flag, msecs * 1000000);
392 QQmlIncubatorPrivate *p = (QQmlIncubatorPrivate*)d->incubatorList.first();
394 } while (d && d->incubatorCount != 0 && !i.shouldInterrupt());
399 \brief The QQmlIncubator class allows QML objects to be created asynchronously.
401 Creating QML objects - like delegates in a view, or a new page in an application - can take
402 a noticable amount of time, especially on resource constrained mobile devices. When an
403 application uses QQmlComponent::create() directly, the QML object instance is created
404 synchronously which, depending on the complexity of the object, can cause noticable pauses or
405 stutters in the application.
407 The use of QQmlIncubator gives more control over the creation of a QML object,
408 including allowing it to be created asynchronously using application idle time. The following
409 example shows a simple use of QQmlIncubator.
412 QQmlIncubator incubator;
413 component->create(incubator);
415 while (incubator.isReady()) {
416 QCoreApplication::processEvents(QEventLoop::AllEvents, 50);
419 QObject *object = incubator.object();
422 Asynchronous incubators are controlled by a QQmlIncubationController that is
423 set on the QQmlEngine, which lets the engine know when the application is idle and
424 incubating objects should be processed. If an incubation controller is not set on the
425 QQmlEngine, QQmlIncubator creates objects synchronously regardless of the
426 specified IncubationMode.
428 QQmlIncubator supports three incubation modes:
430 \i Synchronous The creation occurs synchronously. That is, once the
431 QQmlComponent::create() call returns, the incubator will already be in either the
432 Error or Ready state. A synchronous incubator has no real advantage compared to using
433 the synchronous creation methods on QQmlComponent directly, but it may simplify an
434 application's implementation to use the same API for both synchronous and asynchronous
437 \i Asynchronous (default) The creation occurs asynchronously, assuming a
438 QQmlIncubatorController is set on the QQmlEngine.
440 The incubator will remain in the Loading state until either the creation is complete or an error
441 occurs. The statusChanged() callback can be used to be notified of status changes.
443 Applications should use the Asynchronous incubation mode to create objects that are not needed
444 immediately. For example, the ListView element uses Asynchronous incubation to create objects
445 that are slightly off screen while the list is being scrolled. If, during asynchronous creation,
446 the object is needed immediately the QQmlIncubator::forceCompletion() method can be called
447 to complete the creation process synchronously.
449 \i AsynchronousIfNested The creation will occur asynchronously if part of a nested asynchronous
450 creation, or synchronously if not.
452 In most scenarios where a QML element or component wants the appearance of a synchronous
453 instantiation, it should use this mode.
455 This mode is best explained with an example. When the ListView element is first created, it needs
456 to populate itself with an initial set of delegates to show. If the ListView was 400 pixels high,
457 and each delegate was 100 pixels high, it would need to create four initial delegate instances. If
458 the ListView used the Asynchronous incubation mode, the ListView would always be created empty and
459 then, sometime later, the four initial elements would appear.
461 Conversely, if the ListView was to use the Synchronous incubation mode it would behave correctly
462 but it may introduce stutters into the application. As QML would have to stop and instantiate the
463 ListView's delegates synchronously, if the ListView was part of a QML component that was being
464 instantiated asynchronously this would undo much of the benefit of asynchronous instantiation.
466 The AsynchronousIfNested mode reconciles this problem. By using AsynchronousIfNested, the ListView
467 delegates are instantiated asynchronously if the ListView itself is already part of an asynchronous
468 instantiation, and synchronously otherwise. In the case of a nested asynchronous instantiation, the
469 outer asynchronous instantiation will not complete until after all the nested instantiations have also
470 completed. This ensures that by the time the outer asynchronous instantitation completes, inner
471 elements like ListView have already completed loading their initial delegates.
473 It is almost always incorrect to use the Synchronous incubation mode - elements or components that
474 want the appearance of synchronous instantiation, but without the downsides of introducing freezes
475 or stutters into the application, should use the AsynchronousIfNested incubation mode.
480 Create a new incubator with the specified \a mode
482 QQmlIncubator::QQmlIncubator(IncubationMode mode)
483 : d(new QQmlIncubatorPrivate(this, mode))
488 QQmlIncubator::~QQmlIncubator()
496 \enum QQmlIncubator::IncubationMode
498 Specifies the mode the incubator operates in. Regardless of the incubation mode, a
499 QQmlIncubator will behave synchronously if the QQmlEngine does not have
500 a QQmlIncubationController set.
502 \value Asynchronous The object will be created asynchronously.
503 \value AsynchronousIfNested If the object is being created in a context that is already part
504 of an asynchronous creation, this incubator will join that existing incubation and execute
505 asynchronously. The existing incubation will not become Ready until both it and this
506 incubation have completed. Otherwise, the incubation will execute synchronously.
507 \value Synchronous The object will be created synchronously.
511 \enum QQmlIncubator::Status
513 Specifies the status of the QQmlIncubator.
515 \value Null Incubation is not in progress. Call QQmlComponent::create() to begin incubating.
516 \value Ready The object is fully created and can be accessed by calling object().
517 \value Loading The object is in the process of being created.
518 \value Error An error occurred. The errors can be access by calling errors().
522 Clears the incubator. Any in-progress incubation is aborted. If the incubator is in the
523 Ready state, the created object is \b not deleted.
525 void QQmlIncubator::clear()
527 typedef QQmlIncubatorPrivate IP;
528 QRecursionWatcher<IP, &IP::recursion> watcher(d);
535 QQmlEnginePrivate *enginePriv = 0;
537 Q_ASSERT(d->component);
538 enginePriv = QQmlEnginePrivate::get(d->component->engine);
539 if (d->result) d->result->deleteLater();
548 Q_ASSERT(d->component == 0);
549 Q_ASSERT(d->waitingOnMe == 0);
550 Q_ASSERT(d->waitingFor.isEmpty());
551 Q_ASSERT(!d->nextWaitingFor.isInList());
554 d->progress = QQmlIncubatorPrivate::Execute;
558 Q_ASSERT(enginePriv);
560 enginePriv->inProgressCreations--;
561 if (0 == enginePriv->inProgressCreations) {
562 while (enginePriv->erroredBindings) {
563 enginePriv->warning(enginePriv->erroredBindings->error);
564 enginePriv->erroredBindings->removeError();
569 d->changeStatus(Null);
573 Force any in-progress incubation to finish synchronously. Once this call
574 returns, the incubator will not be in the Loading state.
576 void QQmlIncubator::forceCompletion()
578 QQmlVME::Interrupt i;
579 while (Loading == status()) {
580 while (Loading == status() && !d->waitingFor.isEmpty())
581 static_cast<QQmlIncubatorPrivate *>(d->waitingFor.first())->incubate(i);
582 if (Loading == status())
588 Returns true if the incubator's status() is Null.
590 bool QQmlIncubator::isNull() const
592 return status() == Null;
596 Returns true if the incubator's status() is Ready.
598 bool QQmlIncubator::isReady() const
600 return status() == Ready;
604 Returns true if the incubator's status() is Error.
606 bool QQmlIncubator::isError() const
608 return status() == Error;
612 Returns true if the incubator's status() is Loading.
614 bool QQmlIncubator::isLoading() const
616 return status() == Loading;
620 Return the list of errors encountered while incubating the object.
622 QList<QQmlError> QQmlIncubator::errors() const
628 Return the incubation mode passed to the QQmlIncubator constructor.
630 QQmlIncubator::IncubationMode QQmlIncubator::incubationMode() const
636 Return the current status of the incubator.
638 QQmlIncubator::Status QQmlIncubator::status() const
644 Return the incubated object if the status is Ready, otherwise 0.
646 QObject *QQmlIncubator::object() const
648 if (status() != Ready) return 0;
649 else return d->result;
653 Called when the status of the incubator changes. \a status is the new status.
655 The default implementation does nothing.
657 void QQmlIncubator::statusChanged(Status status)
663 Called after the object is first created, but before property bindings are
664 evaluated and, if applicable, QQmlParserStatus::componentComplete() is
665 called. This is equivalent to the point between QQmlComponent::beginCreate()
666 and QQmlComponent::endCreate(), and can be used to assign initial values
667 to the object's properties.
669 The default implementation does nothing.
671 void QQmlIncubator::setInitialState(QObject *object)
676 void QQmlIncubatorPrivate::changeStatus(QQmlIncubator::Status s)
682 q->statusChanged(status);
685 QQmlIncubator::Status QQmlIncubatorPrivate::calculateStatus() const
687 if (!errors.isEmpty())
688 return QQmlIncubator::Error;
689 else if (result && progress == QQmlIncubatorPrivate::Completed &&
690 waitingFor.isEmpty())
691 return QQmlIncubator::Ready;
693 return QQmlIncubator::Loading;
695 return QQmlIncubator::Null;