gecko-dev/dom/gamepad/GamepadPlatformService.cpp

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this file,
 * You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "mozilla/dom/GamepadPlatformService.h"

#include "mozilla/dom/GamepadEventChannelParent.h"
#include "mozilla/ipc/BackgroundParent.h"
#include "mozilla/Mutex.h"
#include "mozilla/unused.h"

#include "nsCOMPtr.h"
#include "nsHashKeys.h"
#include "nsIThread.h"

using namespace mozilla::ipc;

namespace mozilla {
namespace dom {

namespace {

// This is the singleton instance of GamepadPlatformService, can be called
// by both background and monitor thread.
StaticRefPtr<GamepadPlatformService> gGamepadPlatformServiceSingleton;

} //namepsace

GamepadPlatformService::GamepadPlatformService()
  : mGamepadIndex(0),
    mMutex("mozilla::dom::GamepadPlatformService")
{}

GamepadPlatformService::~GamepadPlatformService()
{
  Cleanup();
}

// static
already_AddRefed<GamepadPlatformService>
GamepadPlatformService::GetParentService()
{
  //GamepadPlatformService can only be accessed in parent process
  MOZ_ASSERT(XRE_IsParentProcess());
  if (!gGamepadPlatformServiceSingleton) {
    // Only Background Thread can create new GamepadPlatformService instance.
    if (IsOnBackgroundThread()) {
      gGamepadPlatformServiceSingleton = new GamepadPlatformService();
    } else {
      return nullptr;
    }
  }
  RefPtr<GamepadPlatformService> service(gGamepadPlatformServiceSingleton);
  return service.forget();
}

template<class T>
void
GamepadPlatformService::NotifyGamepadChange(const T& aInfo)
{
  // This method is called by monitor populated in
  // platform-dependent backends
  MOZ_ASSERT(XRE_IsParentProcess());
  MOZ_ASSERT(!NS_IsMainThread());

  GamepadChangeEvent e(aInfo);

  // mChannelParents may be accessed by background thread in the
  // same time, we use mutex to prevent possible race condtion
  MutexAutoLock autoLock(mMutex);
  for(uint32_t i = 0; i < mChannelParents.Length(); ++i) {
    mChannelParents[i]->DispatchUpdateEvent(e);
  }
}

uint32_t
GamepadPlatformService::AddGamepad(const char* aID,
                                   GamepadMappingType aMapping,
                                   uint32_t aNumButtons, uint32_t aNumAxes)
{
  // This method is called by monitor thread populated in
  // platform-dependent backends
  MOZ_ASSERT(XRE_IsParentProcess());
  MOZ_ASSERT(!NS_IsMainThread());

  uint32_t index = ++mGamepadIndex;
  GamepadAdded a(NS_ConvertUTF8toUTF16(nsDependentCString(aID)), index,
                 (uint32_t)aMapping, aNumButtons, aNumAxes);
  NotifyGamepadChange<GamepadAdded>(a);
  return index;
}

void
GamepadPlatformService::RemoveGamepad(uint32_t aIndex)
{
  // This method is called by monitor thread populated in
  // platform-dependent backends
  MOZ_ASSERT(XRE_IsParentProcess());
  MOZ_ASSERT(!NS_IsMainThread());
  GamepadRemoved a(aIndex);
  NotifyGamepadChange<GamepadRemoved>(a);
}

void
GamepadPlatformService::NewButtonEvent(uint32_t aIndex, uint32_t aButton,
                                       bool aPressed, double aValue)
{
  // This method is called by monitor thread populated in
  // platform-dependent backends
  MOZ_ASSERT(XRE_IsParentProcess());
  MOZ_ASSERT(!NS_IsMainThread());
  GamepadButtonInformation a(aIndex, aButton, aPressed, aValue);
  NotifyGamepadChange<GamepadButtonInformation>(a);
}

void
GamepadPlatformService::NewButtonEvent(uint32_t aIndex, uint32_t aButton,
                                       bool aPressed)
{
  // This method is called by monitor thread populated in
  // platform-dependent backends
  MOZ_ASSERT(XRE_IsParentProcess());
  MOZ_ASSERT(!NS_IsMainThread());
  // When only a digital button is available the value will be synthesized.
  NewButtonEvent(aIndex, aButton, aPressed, aPressed ? 1.0L : 0.0L);
}

void
GamepadPlatformService::NewAxisMoveEvent(uint32_t aIndex, uint32_t aAxis,
                                         double aValue)
{
  // This method is called by monitor thread populated in
  // platform-dependent backends
  MOZ_ASSERT(XRE_IsParentProcess());
  MOZ_ASSERT(!NS_IsMainThread());
  GamepadAxisInformation a(aIndex, aAxis, aValue);
  NotifyGamepadChange<GamepadAxisInformation>(a);
}

void
GamepadPlatformService::ResetGamepadIndexes()
{
  // This method is called by monitor thread populated in
  // platform-dependent backends
  MOZ_ASSERT(XRE_IsParentProcess());
  MOZ_ASSERT(!NS_IsMainThread());
  mGamepadIndex = 0;
}

void
GamepadPlatformService::AddChannelParent(GamepadEventChannelParent* aParent)
{
  // mChannelParents can only be modified once GamepadEventChannelParent
  // is created or removed in Background thread
  AssertIsOnBackgroundThread();
  MOZ_ASSERT(aParent);
  MOZ_ASSERT(!mChannelParents.Contains(aParent));

  // We use mutex here to prevent race condition with monitor thread
  MutexAutoLock autoLock(mMutex);
  mChannelParents.AppendElement(aParent);
}

void
GamepadPlatformService::RemoveChannelParent(GamepadEventChannelParent* aParent)
{
  // mChannelParents can only be modified once GamepadEventChannelParent
  // is created or removed in Background thread
  AssertIsOnBackgroundThread();
  MOZ_ASSERT(aParent);
  MOZ_ASSERT(mChannelParents.Contains(aParent));

  // We use mutex here to prevent race condition with monitor thread
  MutexAutoLock autoLock(mMutex);
  mChannelParents.RemoveElement(aParent);
}

bool
GamepadPlatformService::HasGamepadListeners()
{
  // mChannelParents may be accessed by background thread in the
  // same time, we use mutex to prevent possible race condtion
  AssertIsOnBackgroundThread();

  // We use mutex here to prevent race condition with monitor thread
  MutexAutoLock autoLock(mMutex);
  for (uint32_t i = 0; i < mChannelParents.Length(); i++) {
    if(mChannelParents[i]->HasGamepadListener()) {
      return true;
    }
  }
  return false;
}

void
GamepadPlatformService::MaybeShutdown()
{
  // This method is invoked in MaybeStopGamepadMonitoring when
  // an IPDL channel is going to be destroyed
  AssertIsOnBackgroundThread();

  // We have to release gGamepadPlatformServiceSingleton ouside
  // the mutex as well as making upcoming GetParentService() call
  // recreate new singleton, so we use this RefPtr to temporarily
  // hold the reference, postponing the release process until this
  // method ends.
  RefPtr<GamepadPlatformService> kungFuDeathGrip;

  bool isChannelParentEmpty;
  {
    MutexAutoLock autoLock(mMutex);
    isChannelParentEmpty = mChannelParents.IsEmpty();
    if(isChannelParentEmpty) {
      kungFuDeathGrip = gGamepadPlatformServiceSingleton;
      gGamepadPlatformServiceSingleton = nullptr;
    }
  }
}

void
GamepadPlatformService::Cleanup()
{
  // This method is called when GamepadPlatformService is
  // successfully distructed in background thread
  AssertIsOnBackgroundThread();

  MutexAutoLock autoLock(mMutex);
  mChannelParents.Clear();
}

} // namespace dom
} // namespace mozilla