Change the strategy used to attempt nesting-deferred work to account equally...

base/message_pump_mac.h

 // Copyright (c) 2008 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // The basis for all native run loops on the Mac is the CFRunLoop.  It can be
 // used directly, it can be used as the driving force behind the similar
 // Foundation NSRunLoop, and it can be used to implement higher-level event
 // loops such as the NSApplication event loop.
 //
 // This file introduces a basic CFRunLoop-based implementation of the
@@ skipping 36 matching lines @@
   // in the DoRun method.  MessagePumpCFRunLoopBase::Run calls DoRun directly.
   // This arrangement is used because MessagePumpCFRunLoopBase needs to set
   // up and tear down things before and after the "meat" of DoRun.
   virtual void Run(Delegate* delegate);
   virtual void DoRun(Delegate* delegate) = 0;
 
   virtual void ScheduleWork();
   virtual void ScheduleDelayedWork(const Time& delayed_work_time);
 
  protected:
-  // The thread's run loop.
-  CFRunLoopRef run_loop_;
-
-  // The recursion depth of the currently-executing CFRunLoopRun loop on the
-  // run loop's thread.  0 if no run loops are running inside of whatever scope
-  // the object was created in.
-  int nesting_level_;
-
-  // The recursion depth (calculated in the same way as nesting_level_) of the
-  // innermost executing CFRunLoopRun loop started by a call to Run.
-  int run_nesting_level_;
+  // Accessors for private data members to be used by subclasses.
+  CFRunLoopRef run_loop() const { return run_loop_; }
+  int nesting_level() const { return nesting_level_; }
+  int run_nesting_level() const { return run_nesting_level_; }
 
  private:
   // Timer callback scheduled by ScheduleDelayedWork.  This does not do any
   // work, but it signals delayed_work_source_ so that delayed work can be
   // performed within the appropriate priority constraints.
   static void RunDelayedWorkTimer(CFRunLoopTimerRef timer, void* info);
 
   // Perform highest-priority work.  This is associated with work_source_
   // signalled by ScheduleWork.  The static method calls the instance method;
   // the instance method returns true if work was done.
@@ skipping 11 matching lines @@
   // Perform idle-priority work.  This is normally called by PreWaitObserver,
   // but is also associated with idle_work_source_.  When this function
   // actually does perform idle work, it will resignal that source.  The
   // static method calls the instance method; the instance method returns
   // true if idle work was done.
   static void RunIdleWorkSource(void* info);
   bool RunIdleWork();
 
   // Perform work that may have been deferred because it was not runnable
   // within a nested run loop.  This is associated with
-  // nesting_deferred_work_source_ and is signalled by EnterExitObserver when
-  // a run loop exits, so that an outer loop will be able to perform the
-  // necessary tasks.  The static method calls the instance method; the
-  // instance method returns true if anything was done.
+  // nesting_deferred_work_source_ and is signalled by
+  // MaybeScheduleNestingDeferredWork when returning from a nested loop,
+  // so that an outer loop will be able to perform the necessary tasks if it
+  // permits nestable tasks.
   static void RunNestingDeferredWorkSource(void* info);
   bool RunNestingDeferredWork();
 
+  // Schedules possible nesting-deferred work to be processed before the run
+  // loop goes to sleep or exits.  If this function detects that a nested loop
+  // had run since the previous attempt to schedule nesting-deferred work, it
+  // will schedule a call to RunNestingDeferredWorkSource.
+  void MaybeScheduleNestingDeferredWork();
+
   // Observer callback responsible for performing idle-priority work, before
   // the run loop goes to sleep.  Associated with idle_work_observer_.
   static void PreWaitObserver(CFRunLoopObserverRef observer,
                               CFRunLoopActivity activity, void* info);
 
   // Observer callback called when the run loop starts and stops, at the
   // beginning and end of calls to CFRunLoopRun.  This is used to maintain
   // nesting_level_.  Associated with enter_exit_observer_.
   static void EnterExitObserver(CFRunLoopObserverRef observer,
                                 CFRunLoopActivity activity, void* info);
 
   // Called by EnterExitObserver after performing maintenance on nesting_level_.
   // This allows subclasses an opportunity to perform additional processing on
   // the basis of run loops starting and stopping.
   virtual void EnterExitRunLoop(CFRunLoopActivity activity);
 
+  // The thread's run loop.
+  CFRunLoopRef run_loop_;
+
   // The timer, sources, and observers are described above alongside their
   // callbacks.
   CFRunLoopTimerRef delayed_work_timer_;
   CFRunLoopSourceRef work_source_;
   CFRunLoopSourceRef delayed_work_source_;
   CFRunLoopSourceRef idle_work_source_;
   CFRunLoopSourceRef nesting_deferred_work_source_;
   CFRunLoopObserverRef pre_wait_observer_;
   CFRunLoopObserverRef enter_exit_observer_;
 
   // (weak) Delegate passed as an argument to the innermost Run call.
   Delegate* delegate_;
 
+  // The recursion depth of the currently-executing CFRunLoopRun loop on the
+  // run loop's thread.  0 if no run loops are running inside of whatever scope
+  // the object was created in.
+  int nesting_level_;
+
+  // The recursion depth (calculated in the same way as nesting_level_) of the
+  // innermost executing CFRunLoopRun loop started by a call to Run.
+  int run_nesting_level_;
+
+  // The deepest (numerically highest) recursion depth encountered since the
+  // most recent attempt to run nesting-deferred work.
+  int deepest_nesting_level_;
+
   // "Delegateless" work flags are set when work is ready to be performed but
   // must wait until a delegate is available to process it.  This can happen
   // when a MessagePumpCFRunLoopBase is instantiated and work arrives without
   // any call to Run on the stack.  The Run method will check for delegateless
   // work on entry and redispatch it as needed once a delegate is available.
   bool delegateless_work_;
   bool delegateless_delayed_work_;
   bool delegateless_idle_work_;
 
   DISALLOW_COPY_AND_ASSIGN(MessagePumpCFRunLoopBase);
@@ skipping 63 matching lines @@
   // thread.  Otherwise, returns a new instance of MessagePumpNSRunLoop.
   static MessagePump* Create();
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(MessagePumpMac);
 };
 
 }  // namespace base
 
 #endif  // BASE_MESSAGE_PUMP_MAC_H_