Allow Thread to initialize COM for Windows consumers who need it

base/threading/thread.cc

 // Copyright (c) 2012 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.
 
 #include "base/threading/thread.h"
 
 #include "base/bind.h"
 #include "base/lazy_instance.h"
 #include "base/third_party/dynamic_annotations/dynamic_annotations.h"
 #include "base/threading/thread_local.h"
 #include "base/threading/thread_restrictions.h"
 #include "base/synchronization/waitable_event.h"
 
+#if defined(OS_WIN)
+#include "base/win/scoped_com_initializer.h"
+#endif
+
 namespace base {
 
 namespace {
 
 // We use this thread-local variable to record whether or not a thread exited
 // because its Stop method was called.  This allows us to catch cases where
 // MessageLoop::Quit() is called directly, which is unexpected when using a
 // Thread to setup and run a MessageLoop.
 base::LazyInstance<base::ThreadLocalBoolean> lazy_tls_bool =
     LAZY_INSTANCE_INITIALIZER;
@@ skipping 29 matching lines @@
       message_loop_(NULL),
       thread_id_(kInvalidThreadId),
       name_(name) {
 }
 
 Thread::~Thread() {
   Stop();
 }
 
 bool Thread::Start() {
-  return StartWithOptions(Options());
+  Options options;
+#if defined(OS_WIN)
+  if (com_status_ == STA)
+    options.message_loop_type = MessageLoop::TYPE_UI;
+#endif
+  return StartWithOptions(options);
 }
 
 bool Thread::StartWithOptions(const Options& options) {
   DCHECK(!message_loop_);
+#if defined(OS_WIN)
+  DCHECK((com_status_ != STA) ||
+      (options.message_loop_type == MessageLoop::TYPE_UI));
+#endif
 
   SetThreadWasQuitProperly(false);
 
   StartupData startup_data(options);
   startup_data_ = &startup_data;
 
   if (!PlatformThread::Create(options.stack_size, this, &thread_)) {
     DLOG(ERROR) << "failed to create thread";
     startup_data_ = NULL;
     return false;
   }
 
   // Wait for the thread to start and initialize message_loop_
   base::ThreadRestrictions::ScopedAllowWait allow_wait;
   startup_data.event.Wait();
 
   // set it to NULL so we don't keep a pointer to some object on the stack.
   startup_data_ = NULL;
   started_ = true;
 
   DCHECK(message_loop_);
   return true;
 }
 
 void Thread::Stop() {
-  if (!thread_was_started())
+  if (!started_)
     return;
 
   StopSoon();
 
   // Wait for the thread to exit.
   //
   // TODO(darin): Unfortunately, we need to keep message_loop_ around until
   // the thread exits.  Some consumers are abusing the API.  Make them stop.
   //
   PlatformThread::Join(thread_);
@@ skipping 46 matching lines @@
     // The message loop for this thread.
     MessageLoop message_loop(startup_data_->options.message_loop_type);
 
     // Complete the initialization of our Thread object.
     thread_id_ = PlatformThread::CurrentId();
     PlatformThread::SetName(name_.c_str());
     ANNOTATE_THREAD_NAME(name_.c_str());  // Tell the name to race detector.
     message_loop.set_thread_name(name_);
     message_loop_ = &message_loop;
 
+#if defined(OS_WIN)
+    if (com_status_ != NONE) {
+      com_initializer_.reset((com_status_ == STA) ?
+          new win::ScopedCOMInitializer() :
+          new win::ScopedCOMInitializer(win::ScopedCOMInitializer::kMTA));
+    }
+#endif
+
     // Let the thread do extra initialization.
     // Let's do this before signaling we are started.
     Init();
 
     running_ = true;
     startup_data_->event.Signal();
     // startup_data_ can't be touched anymore since the starting thread is now
     // unlocked.
 
     Run(message_loop_);
     running_ = false;
 
     // Let the thread do extra cleanup.
     CleanUp();
 
+#if defined(OS_WIN)
+    com_initializer_.reset();

[Ami GONE FROM CHROMIUM, 2012/10/16 02:52:03]

observation: this variable is only used in this function, so it could be a local
instead of class-member (and stack-allocated instead of heap, if it's not big).

This would let you drop the fwd-decl in the .h, too.

+#endif
+
     // Assert that MessageLoop::Quit was called by ThreadQuitHelper.
     DCHECK(GetThreadWasQuitProperly());
 
     // We can't receive messages anymore.
     message_loop_ = NULL;
   }
 }
 
 }  // namespace base