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9edd615af7
This patch refactors the nsThread event queue to clean it up and to make it easier to restructure. The fundamental concepts are as follows: Each nsThread will have a pointer to a refcounted SynchronizedEventQueue. A SynchronizedEQ takes care of doing the locking and condition variable work when posting and popping events. For the actual storage of events, it delegates to an AbstractEventQueue data structure. It keeps a UniquePtr to the AbstractEventQueue that it uses for storage. Both SynchronizedEQ and AbstractEventQueue are abstract classes. There is only one concrete implementation of SynchronizedEQ in this patch, which is called ThreadEventQueue. ThreadEventQueue uses locks and condition variables to post and pop events the same way nsThread does. It also encapsulates the functionality that DOM workers need to implement their special event loops (PushEventQueue and PopEventQueue). In later Quantum DOM work, I plan to have another SynchronizedEQ implementation for the main thread, called SchedulerEventQueue. It will have special code for the cooperatively scheduling threads in Quantum DOM. There are two concrete implementations of AbstractEventQueue in this patch: EventQueue and PrioritizedEventQueue. EventQueue replaces the old nsEventQueue. The other AbstractEventQueue implementation is PrioritizedEventQueue, which uses multiple queues for different event priorities. The final major piece here is ThreadEventTarget, which splits some of the code for posting events out of nsThread. Eventually, my plan is for multiple cooperatively scheduled nsThreads to be able to share a ThreadEventTarget. In this patch, though, each nsThread has its own ThreadEventTarget. The class's purpose is just to collect some related code together. One final note: I tried to avoid virtual dispatch overhead as much as possible. Calls to SynchronizedEQ methods do use virtual dispatch, since I plan to use different implementations for different threads with Quantum DOM. But all the calls to EventQueue methods should be non-virtual. Although the methods are declared virtual, all the classes used are final and the concrete classes involved should all be known through templatization. MozReview-Commit-ID: 9Evtr9oIJvx
111 lines
4.1 KiB
Plaintext
111 lines
4.1 KiB
Plaintext
/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim:set ts=2 sw=2 sts=2 et cindent: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#include "nsIThread.idl"
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interface nsIRunnable;
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interface nsIThreadObserver;
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/**
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* The XPCOM thread object implements this interface, which allows a consumer
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* to observe dispatch activity on the thread.
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*/
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[builtinclass, scriptable, uuid(a3a72e5f-71d9-4add-8f30-59a78fb6d5eb)]
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interface nsIThreadInternal : nsIThread
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{
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/**
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* Get/set the current thread observer (may be null). This attribute may be
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* read from any thread, but must only be set on the thread corresponding to
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* this thread object. The observer will be released on the thread
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* corresponding to this thread object after all other events have been
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* processed during a call to Shutdown.
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*/
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attribute nsIThreadObserver observer;
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/**
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* Add an observer that will *only* receive onProcessNextEvent,
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* beforeProcessNextEvent. and afterProcessNextEvent callbacks. Always called
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* on the target thread, and the implementation does not have to be
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* threadsafe. Order of callbacks is not guaranteed (i.e.
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* afterProcessNextEvent may be called first depending on whether or not the
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* observer is added in a nested loop). Holds a strong ref.
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*/
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void addObserver(in nsIThreadObserver observer);
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/**
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* Remove an observer added via the addObserver call. Once removed the
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* observer will never be called again by the thread.
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*/
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void removeObserver(in nsIThreadObserver observer);
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};
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/**
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* This interface provides the observer with hooks to implement a layered
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* event queue. For example, it is possible to overlay processing events
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* for a GUI toolkit on top of the events for a thread:
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*
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* var NativeQueue;
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* Observer = {
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* onDispatchedEvent() {
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* NativeQueue.signal();
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* }
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* onProcessNextEvent(thread, mayWait) {
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* if (NativeQueue.hasNextEvent())
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* NativeQueue.processNextEvent();
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* while (mayWait && !thread.hasPendingEvent()) {
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* NativeQueue.wait();
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* NativeQueue.processNextEvent();
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* }
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* }
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* };
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*
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* NOTE: The implementation of this interface must be threadsafe.
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*
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* NOTE: It is valid to change the thread's observer during a call to an
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* observer method.
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*
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* NOTE: Will be split into two interfaces soon: one for onProcessNextEvent and
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* afterProcessNextEvent, then another that inherits the first and adds
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* onDispatchedEvent.
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*/
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[uuid(cc8da053-1776-44c2-9199-b5a629d0a19d)]
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interface nsIThreadObserver : nsISupports
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{
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/**
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* This method is called after an event has been dispatched to the thread.
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* This method may be called from any thread.
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*/
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void onDispatchedEvent();
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/**
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* This method is called when nsIThread::ProcessNextEvent is called. It does
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* not guarantee that an event is actually going to be processed. This method
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* is only called on the target thread.
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*
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* @param thread
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* The thread being asked to process another event.
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* @param mayWait
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* Indicates whether or not the method is allowed to block the calling
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* thread. For example, this parameter is false during thread shutdown.
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*/
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void onProcessNextEvent(in nsIThreadInternal thread, in boolean mayWait);
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/**
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* This method is called (from nsIThread::ProcessNextEvent) after an event
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* is processed. It does not guarantee that an event was actually processed
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* (depends on the value of |eventWasProcessed|. This method is only called
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* on the target thread. DO NOT EVER RUN SCRIPT FROM THIS CALLBACK!!!
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*
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* @param thread
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* The thread that processed another event.
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* @param eventWasProcessed
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* Indicates whether an event was actually processed. May be false if the
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* |mayWait| flag was false when calling nsIThread::ProcessNextEvent().
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*/
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void afterProcessNextEvent(in nsIThreadInternal thread,
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in bool eventWasProcessed);
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};
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