gfx/layers/MemoryPressureObserver.cpp
author Dustin J. Mitchell <dustin@mozilla.com>
Wed, 04 Jul 2018 02:46:59 +0000
changeset 490807 ab58645e9230620ca45de3ec03ee9e61eb4a7cbf
parent 489290 d4a387207b7ae2cb4a431c62ff78a526e12c2ee2
child 508163 6f3709b3878117466168c40affa7bca0b60cf75b
permissions -rw-r--r--
Bug 1398277: special-case retriggering of tasks not in the taskgraph; r=bstack This will apply to cron tasks, action tasks, and decision tasks. It is a distinct retrigger implementation because (a) we do not want to follow dependencies, and (b) it takes a lot of scopes to create a decision task, so we need to limit access to this action. MozReview-Commit-ID: 21DVSiagcrO

/* -*- 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 "MemoryPressureObserver.h"

namespace mozilla {
namespace layers {

MemoryPressureObserver::MemoryPressureObserver(MemoryPressureListener* aListener)
: mListener(aListener)
{}

MemoryPressureObserver::~MemoryPressureObserver()
{
  // If this assertion is hit we probably forgot to unregister the observer.
  MOZ_ASSERT(!mListener);
}

already_AddRefed<MemoryPressureObserver>
MemoryPressureObserver::Create(MemoryPressureListener* aListener)
{
  nsCOMPtr<nsIObserverService> service = services::GetObserverService();

  if (!service) {
    return nullptr;
  }

  RefPtr<MemoryPressureObserver> observer = new MemoryPressureObserver(aListener);

  bool useWeakRef = false;
  service->AddObserver(observer, "memory-pressure", useWeakRef);

  return observer.forget();
}

void
MemoryPressureObserver::Unregister()
{
  if (!mListener) {
    return;
  }

  nsCOMPtr<nsIObserverService> service = services::GetObserverService();
  if (service) {
    service->RemoveObserver(this, "memory-pressure");
  }

  mListener = nullptr;
}

NS_IMETHODIMP
MemoryPressureObserver::Observe(nsISupports* aSubject,
                                const char* aTopic,
                                const char16_t* aData)
{
  if (mListener && strcmp(aTopic, "memory-pressure") == 0) {
    MemoryPressureReason reason = MemoryPressureReason::LOW_MEMORY;
    auto reason_string = nsDependentString(aData);
    if (StringBeginsWith(reason_string, NS_LITERAL_STRING("low-memory-ongoing"))) {
        reason = MemoryPressureReason::LOW_MEMORY_ONGOING;
    } else if (StringBeginsWith(reason_string, NS_LITERAL_STRING("heap-minimize"))) {
        reason = MemoryPressureReason::HEAP_MINIMIZE;
    }
    mListener->OnMemoryPressure(reason);
  }

  return NS_OK;
}

NS_IMPL_ISUPPORTS(MemoryPressureObserver, nsIObserver)

} // namespace layers
} // namespace mozilla