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76e3009ab8
This is motivated by three separate but related problems: 1. Our concept of recursion depth is broken for things that run from AfterProcessNextEvent observers (e.g. Promises). We decrement the recursionDepth counter before firing observers, so a Promise callback running at the lowest event loop depth has a recursion depth of 0 (whereas a regular nsIRunnable would be 1). This is a problem because it's impossible to distinguish a Promise running after a sync XHR's onreadystatechange handler from a top-level event (since the former runs with depth 2 - 1 = 1, and the latter runs with just 1). 2. The nsIThreadObserver mechanism that is used by a lot of code to run "after" the current event is a poor fit for anything that runs script. First, the order the observers fire in is the order they were added, not anything fixed by spec. Additionally, running script can cause the event loop to spin, which is a big source of pain here (bholley has some nasty bug caused by this). 3. We run Promises from different points in the code for workers and main thread. The latter runs from XPConnect's nsIThreadObserver callbacks, while the former runs from a hardcoded call to run Promises in the worker event loop. What workers do is particularly problematic because it means we can't get the right recursion depth no matter what we do to nsThread. The solve this, this patch does the following: 1. Consolidate some handling of microtasks and all handling of stable state from appshell and WorkerPrivate into CycleCollectedJSRuntime. 2. Make the recursionDepth counter only available to CycleCollectedJSRuntime (and its consumers) and remove it from the nsIThreadInternal and nsIThreadObserver APIs. 3. Adjust the recursionDepth counter so that microtasks run with the recursionDepth of the task they are associated with. 4. Introduce the concept of metastable state to replace appshell's RunBeforeNextEvent. Metastable state is reached after every microtask or task is completed. This provides the semantics that bent and I want for IndexedDB, where transactions autocommit at the end of a microtask and do not "spill" from one microtask into a subsequent microtask. This differs from appshell's RunBeforeNextEvent in two ways: a) It fires between microtasks, which was the motivation for starting this. b) It no longer ensures that we're at the same event loop depth in the native event queue. bent decided we don't care about this. 5. Reorder stable state to happen after microtasks such as Promises, per HTML. Right now we call the regular thread observers, including appshell, before the main thread observer (XPConnect), so stable state tasks happen before microtasks.
72 lines
1.8 KiB
Objective-C
72 lines
1.8 KiB
Objective-C
/* -*- Mode: c++; tab-width: 2; indent-tabs-mode: nil; -*- */
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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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/*
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* Runs the main native Cocoa run loop, interrupting it as needed to process
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* Gecko events.
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*/
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#ifndef nsAppShell_h_
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#define nsAppShell_h_
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#include "nsBaseAppShell.h"
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#include "nsTArray.h"
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// GeckoNSApplication
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//
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// Subclass of NSApplication for filtering out certain events.
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@interface GeckoNSApplication : NSApplication
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{
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}
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@end
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@class AppShellDelegate;
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class nsAppShell : public nsBaseAppShell
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{
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public:
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NS_IMETHOD ResumeNative(void);
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nsAppShell();
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nsresult Init();
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NS_IMETHOD Run(void);
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NS_IMETHOD Exit(void);
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NS_IMETHOD OnProcessNextEvent(nsIThreadInternal *aThread, bool aMayWait);
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NS_IMETHOD AfterProcessNextEvent(nsIThreadInternal *aThread,
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bool aEventWasProcessed);
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// public only to be visible to Objective-C code that must call it
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void WillTerminate();
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protected:
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virtual ~nsAppShell();
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virtual void ScheduleNativeEventCallback();
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virtual bool ProcessNextNativeEvent(bool aMayWait);
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static void ProcessGeckoEvents(void* aInfo);
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protected:
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CFMutableArrayRef mAutoreleasePools;
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AppShellDelegate* mDelegate;
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CFRunLoopRef mCFRunLoop;
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CFRunLoopSourceRef mCFRunLoopSource;
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bool mRunningEventLoop;
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bool mStarted;
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bool mTerminated;
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bool mSkippedNativeCallback;
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bool mRunningCocoaEmbedded;
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int32_t mNativeEventCallbackDepth;
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// Can be set from different threads, so must be modified atomically
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int32_t mNativeEventScheduledDepth;
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};
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#endif // nsAppShell_h_
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