PPAPI: Make PPB_MessageLoop_Dev::GetForMainThread work

ppapi/proxy/ppb_message_loop_proxy.cc

Index: ppapi/proxy/ppb_message_loop_proxy.cc
diff --git a/ppapi/proxy/ppb_message_loop_proxy.cc b/ppapi/proxy/ppb_message_loop_proxy.cc
index bcbb82a72a940e6086c450f695104a07f01840a2..916002d0795981d4be027dc4b2034ea080c33044 100644
--- a/ppapi/proxy/ppb_message_loop_proxy.cc
+++ b/ppapi/proxy/ppb_message_loop_proxy.cc
@@ -9,14 +9,13 @@
 #include "base/bind.h"
 #include "base/compiler_specific.h"
 #include "base/message_loop.h"
+#include "base/message_loop_proxy.h"
 #include "ppapi/c/dev/ppb_message_loop_dev.h"
 #include "ppapi/c/pp_errors.h"
 #include "ppapi/proxy/plugin_dispatcher.h"
 #include "ppapi/proxy/plugin_globals.h"
 #include "ppapi/shared_impl/proxy_lock.h"
-#include "ppapi/shared_impl/resource.h"
 #include "ppapi/thunk/enter.h"
-#include "ppapi/thunk/ppb_message_loop_api.h"
 
 using ppapi::thunk::PPB_MessageLoop_API;
 
@@ -24,78 +23,42 @@ namespace ppapi {
 namespace proxy {
 
 namespace {
-
 typedef thunk::EnterResource<PPB_MessageLoop_API> EnterMessageLoop;
-
-class MessageLoopResource : public Resource, public PPB_MessageLoop_API {
- public:
-  MessageLoopResource(PP_Instance instance);
-  virtual ~MessageLoopResource();
-
-  // Resource overrides.
-  virtual PPB_MessageLoop_API* AsPPB_MessageLoop_API() OVERRIDE;
-
-  // PPB_MessageLoop_API implementation.
-  virtual int32_t AttachToCurrentThread() OVERRIDE;
-  virtual int32_t Run() OVERRIDE;
-  virtual int32_t PostWork(PP_CompletionCallback callback,
-                           int64_t delay_ms) OVERRIDE;
-  virtual int32_t PostQuit(PP_Bool should_destroy) OVERRIDE;
-
-  void DetachFromThread();
-
- private:
-  struct TaskInfo {
-    tracked_objects::Location from_here;
-    base::Closure closure;
-    int64 delay_ms;
-  };
-
-  // Returns true if the object is associated with the current thread.
-  bool IsCurrent() const;
-
-  // Handles posting to the message loop if there is one, or the pending queue
-  // if there isn't.
-  // NOTE: The given closure will be run *WITHOUT* acquiring the Proxy lock.
-  //       This only makes sense for user code and completely thread-safe
-  //       proxy operations (e.g., MessageLoop::QuitClosure).
-  void PostClosure(const tracked_objects::Location& from_here,
-                   const base::Closure& closure,
-                   int64 delay_ms);
-
-  // TLS destructor function.
-  static void ReleaseMessageLoop(void* value);
-
-  // Created when we attach to the current thread, since MessageLoop assumes
-  // that it's created on the thread it will run on.
-  scoped_ptr<MessageLoop> loop_;
-
-  // Number of invocations of Run currently on the stack.
-  int nested_invocations_;
-
-  // Set to true when the message loop is destroyed to prevent forther
-  // posting of work.
-  bool destroyed_;
-
-  // Set to true if all message loop invocations should exit and that the
-  // loop should be destroyed once it reaches the outermost Run invocation.
-  bool should_destroy_;
-
-  // Since we allow tasks to be posted before the message loop is actually
-  // created (when it's associated with a thread), we keep tasks posted here
-  // until that happens. Once the loop_ is created, this is unused.
-  std::vector<TaskInfo> pending_tasks_;
-
-  DISALLOW_COPY_AND_ASSIGN(MessageLoopResource);
-};
+}
 
 MessageLoopResource::MessageLoopResource(PP_Instance instance)
     : Resource(OBJECT_IS_PROXY, instance),
       nested_invocations_(0),
       destroyed_(false),
-      should_destroy_(false) {
+      should_destroy_(false),
+      is_main_thread_loop_(false) {
+}
+
+MessageLoopResource::MessageLoopResource(ForMainThread)
+    : Resource(Resource::Untracked()),
+      nested_invocations_(0),
+      destroyed_(false),
+      should_destroy_(false),
+      is_main_thread_loop_(true) {
+  // We attach the main thread immediately. We can't use AttachToCurrentThread,
+  // because the MessageLoop already exists.
+
+  // This must be called only once, so the slot must be empty.
+  CHECK(!PluginGlobals::Get()->msg_loop_slot());
+  base::ThreadLocalStorage::Slot* slot =
+      new base::ThreadLocalStorage::Slot(&ReleaseMessageLoop);
+  PluginGlobals::Get()->set_msg_loop_slot(slot);
+
+  // Take a ref to the MessageLoop on behalf of the TLS. Note that this is an
+  // internal ref and not a plugin ref so the plugin can't accidentally
+  // release it. This is released by ReleaseMessageLoop().
+  AddRef();
+  slot->Set(this);
+
+  loop_proxy_ = base::MessageLoopProxy::current();
 }
 
+
 MessageLoopResource::~MessageLoopResource() {
 }
 
@@ -104,6 +67,9 @@ PPB_MessageLoop_API* MessageLoopResource::AsPPB_MessageLoop_API() {
 }
 
 int32_t MessageLoopResource::AttachToCurrentThread() {
+  if (is_main_thread_loop_)
+    return PP_ERROR_INPROGRESS;
+
   PluginGlobals* globals = PluginGlobals::Get();
 
   base::ThreadLocalStorage::Slot* slot = globals->msg_loop_slot();
@@ -123,6 +89,7 @@ int32_t MessageLoopResource::AttachToCurrentThread() {
   slot->Set(this);
 
   loop_.reset(new MessageLoop(MessageLoop::TYPE_DEFAULT));
+  loop_proxy_ = base::MessageLoopProxy::current();
 
   // Post all pending work to the message loop.
   for (size_t i = 0; i < pending_tasks_.size(); i++) {
@@ -137,9 +104,8 @@ int32_t MessageLoopResource::AttachToCurrentThread() {
 int32_t MessageLoopResource::Run() {
   if (!IsCurrent())
     return PP_ERROR_WRONG_THREAD;
-  // TODO(brettw) prevent this from happening on the main thread & return
-  // PP_ERROR_BLOCKS_MAIN_THREAD.  Maybe have a special constructor for that
-  // one?
+  if (is_main_thread_loop_)
+    return PP_ERROR_INPROGRESS;
 
   nested_invocations_++;
   CallWhileUnlocked(base::Bind(&MessageLoop::Run,
@@ -147,6 +113,7 @@ int32_t MessageLoopResource::Run() {
   nested_invocations_--;
 
   if (should_destroy_ && nested_invocations_ == 0) {
+    loop_proxy_ = NULL;
     loop_.reset();
     destroyed_ = true;
   }
@@ -167,6 +134,9 @@ int32_t MessageLoopResource::PostWork(PP_CompletionCallback callback,
 }
 
 int32_t MessageLoopResource::PostQuit(PP_Bool should_destroy) {
+  if (is_main_thread_loop_)
+    return PP_ERROR_WRONG_THREAD;
+
   if (PP_ToBool(should_destroy))
     should_destroy_ = true;
 
@@ -178,8 +148,14 @@ int32_t MessageLoopResource::PostQuit(PP_Bool should_destroy) {
 }
 
 void MessageLoopResource::DetachFromThread() {
+  // Never detach the main thread from its loop resource. Other plugin instances
+  // might need it.
+  if (is_main_thread_loop_)
+    return;
+
   // Note that the message loop must be destroyed on the thread is was created
   // on.
+  loop_proxy_ = NULL;
   loop_.reset();
 
   // Cancel out the AddRef in AttachToCurrentThread().
@@ -199,10 +175,10 @@ void MessageLoopResource::PostClosure(
     const tracked_objects::Location& from_here,
     const base::Closure& closure,
     int64 delay_ms) {
-  if (loop_.get()) {
-    loop_->PostDelayedTask(from_here,
-                           closure,
-                           base::TimeDelta::FromMilliseconds(delay_ms));
+  if (loop_proxy_) {
+    loop_proxy_->PostDelayedTask(from_here,
+                                 closure,
+                                 base::TimeDelta::FromMilliseconds(delay_ms));
   } else {
     TaskInfo info;
     info.from_here = FROM_HERE;
@@ -228,8 +204,7 @@ PP_Resource Create(PP_Instance instance) {
 }
 
 PP_Resource GetForMainThread() {
-  // TODO(brettw).
-  return 0;
+  return PluginGlobals::Get()->loop_for_main_thread()->GetReference();
 }
 
 PP_Resource GetCurrent() {
@@ -281,8 +256,6 @@ const PPB_MessageLoop_Dev_0_1 ppb_message_loop_interface = {
   &PostQuit
 };
 
-}  // namespace
-
 PPB_MessageLoop_Proxy::PPB_MessageLoop_Proxy(Dispatcher* dispatcher)
     : InterfaceProxy(dispatcher) {
 }