/* -*- 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 "CanvasThread.h"

#include "mozilla/SharedThreadPool.h"
#include "nsThreadUtils.h"
#include "prsystem.h"

bool NS_IsInCanvasThreadOrWorker() {
  return mozilla::layers::CanvasThreadHolder::IsInCanvasThreadOrWorker();
}

namespace mozilla {
namespace layers {

StaticDataMutex<StaticRefPtr<CanvasThreadHolder>>
    CanvasThreadHolder::sCanvasThreadHolder("sCanvasThreadHolder");

CanvasThreadHolder::CanvasThreadHolder(
    already_AddRefed<nsISerialEventTarget> aCanvasThread,
    already_AddRefed<nsIThreadPool> aCanvasWorkers)
    : mCanvasThread(aCanvasThread),
      mCanvasWorkers(aCanvasWorkers),
      mCompositorThreadKeepAlive(CompositorThreadHolder::GetSingleton()) {
  MOZ_ASSERT(NS_IsInCompositorThread());
  MOZ_ASSERT(mCanvasThread);
  MOZ_ASSERT(mCanvasWorkers);
}

CanvasThreadHolder::~CanvasThreadHolder() {
  // Note we can't just use NS_IsInCompositorThread() here because
  // sCompositorThreadHolder might have already gone.
  MOZ_ASSERT(
      mCompositorThreadKeepAlive->GetCompositorThread()->IsOnCurrentThread());
}

/* static */
already_AddRefed<CanvasThreadHolder> CanvasThreadHolder::EnsureCanvasThread() {
  MOZ_ASSERT(NS_IsInCompositorThread());

  auto lockedCanvasThreadHolder = sCanvasThreadHolder.Lock();
  if (!lockedCanvasThreadHolder.ref()) {
    nsCOMPtr<nsISerialEventTarget> canvasThread;
    nsresult rv =
        NS_CreateBackgroundTaskQueue("Canvas", getter_AddRefs(canvasThread));
    NS_ENSURE_SUCCESS(rv, nullptr);

    // Given that the canvas workers are receiving instructions from
    // content processes, it probably doesn't make sense to have more than
    // half the number of processors doing canvas drawing. We set the
    // lower limit to 2, so that even on single processor systems, if
    // there is more than one window with canvas drawing, the OS can
    // manage the load between them.
    uint32_t threadLimit = std::max(2, PR_GetNumberOfProcessors() / 2);
    nsCOMPtr<nsIThreadPool> canvasWorkers =
        SharedThreadPool::Get("CanvasWorkers"_ns, threadLimit);
    if (!canvasWorkers) {
      return nullptr;
    }

    lockedCanvasThreadHolder.ref() =
        new CanvasThreadHolder(canvasThread.forget(), canvasWorkers.forget());
  }

  return do_AddRef(lockedCanvasThreadHolder.ref());
}

/* static */
void CanvasThreadHolder::ReleaseOnCompositorThread(
    already_AddRefed<CanvasThreadHolder> aCanvasThreadHolder) {
  RefPtr<CanvasThreadHolder> canvasThreadHolder = aCanvasThreadHolder;
  auto lockedCanvasThreadHolder = sCanvasThreadHolder.Lock();
  lockedCanvasThreadHolder.ref()
      ->mCompositorThreadKeepAlive->GetCompositorThread()
      ->Dispatch(NS_NewRunnableFunction(
          "CanvasThreadHolder::StaticRelease",
          [canvasThreadHolder = std::move(canvasThreadHolder)]() mutable {
            RefPtr<CanvasThreadHolder> threadHolder =
                canvasThreadHolder.forget();
            threadHolder = nullptr;

            auto lockedCanvasThreadHolder = sCanvasThreadHolder.Lock();
            if (lockedCanvasThreadHolder.ref()->mRefCnt == 1) {
              lockedCanvasThreadHolder.ref() = nullptr;
            }
          }));
}

/* static */
bool CanvasThreadHolder::IsInCanvasThread() {
  auto lockedCanvasThreadHolder = sCanvasThreadHolder.Lock();
  return lockedCanvasThreadHolder.ref() &&
         lockedCanvasThreadHolder.ref()->mCanvasThread->IsOnCurrentThread();
}

/* static */
bool CanvasThreadHolder::IsInCanvasWorker() {
  auto lockedCanvasThreadHolder = sCanvasThreadHolder.Lock();
  return lockedCanvasThreadHolder.ref() &&
         lockedCanvasThreadHolder.ref()->mCanvasWorkers->IsOnCurrentThread();
}

/* static */
bool CanvasThreadHolder::IsInCanvasThreadOrWorker() {
  auto lockedCanvasThreadHolder = sCanvasThreadHolder.Lock();
  return lockedCanvasThreadHolder.ref() &&
         (lockedCanvasThreadHolder.ref()->mCanvasWorkers->IsOnCurrentThread() ||
          lockedCanvasThreadHolder.ref()->mCanvasThread->IsOnCurrentThread());
}

/* static */
void CanvasThreadHolder::MaybeDispatchToCanvasThread(
    already_AddRefed<nsIRunnable> aRunnable) {
  auto lockedCanvasThreadHolder = sCanvasThreadHolder.Lock();
  if (!lockedCanvasThreadHolder.ref()) {
    // There is no canvas thread just release the runnable.
    nsCOMPtr<nsIRunnable> runnable = aRunnable;
    return;
  }

  lockedCanvasThreadHolder.ref()->mCanvasThread->Dispatch(std::move(aRunnable));
}

void CanvasThreadHolder::DispatchToCanvasThread(
    already_AddRefed<nsIRunnable> aRunnable) {
  mCanvasThread->Dispatch(std::move(aRunnable));
}

already_AddRefed<TaskQueue> CanvasThreadHolder::CreateWorkerTaskQueue() {
  return MakeAndAddRef<TaskQueue>(do_AddRef(mCanvasWorkers));
}

}  // namespace layers
}  // namespace mozilla