image/IProgressObserver.h
author Kartikaya Gupta <kgupta@mozilla.com>
Wed, 30 May 2018 15:54:50 -0400
changeset 420571 8a1bdb8d8bf5a1c8869bf3f82fd86c56f9f4b72c
parent 402771 62497967f092c6c76778ddc1534f110d4583eeb9
child 448947 6f3709b3878117466168c40affa7bca0b60cf75b
permissions -rw-r--r--
Bug 1457590 - Strengthen the contract around recycling HitTestingTreeNodes. r=botond This patch makes three related changes: - A non-functional change that factors a IsRecyclable function on HitTestingTreeNode. - A non-functional change that sprinkles proof-of-tree-lock arguments to a few HitTestingTreeNode functions, to ensure at compile-time that they can only be called while holding the tree lock. - A functional change that stops clearing mLayersId in HitTestingTreeNode::Destroy, so that if a node is non-recyclable, and it gets Destroy()'d while other code still has a RefPtr to it, that other code can still read the layers id off in a safe manner. These changes provide a stronger set of checks around node recycling, and allows for a safe mechanism to use a HitTestingTreeNode on the controller thread without having to lock the entire APZ tree. The mechanism is effectively a per-node lock, which will be added in the next patch. MozReview-Commit-ID: DBIjFDZJwhE

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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/. */

#ifndef mozilla_image_IProgressObserver_h
#define mozilla_image_IProgressObserver_h

#include "mozilla/WeakPtr.h"
#include "nsISupports.h"
#include "nsRect.h"

class nsIEventTarget;

namespace mozilla {
namespace image {

/**
 * An interface for observing changes to image state, as reported by
 * ProgressTracker.
 *
 * This is the ImageLib-internal version of imgINotificationObserver,
 * essentially, with implementation details that code outside of ImageLib
 * shouldn't see.
 *
 * XXX(seth): It's preferable to avoid adding anything to this interface if
 * possible.  In the long term, it would be ideal to get to a place where we can
 * just use the imgINotificationObserver interface internally as well.
 */
class IProgressObserver : public SupportsWeakPtr<IProgressObserver>
{
public:
  MOZ_DECLARE_WEAKREFERENCE_TYPENAME(IProgressObserver)

  // Subclasses may or may not be XPCOM classes, so we just require that they
  // implement AddRef and Release.
  NS_INLINE_DECL_PURE_VIRTUAL_REFCOUNTING

  // imgINotificationObserver methods:
  virtual void Notify(int32_t aType, const nsIntRect* aRect = nullptr) = 0;
  virtual void OnLoadComplete(bool aLastPart) = 0;

  // Other, internal-only methods:
  virtual void SetHasImage() = 0;
  virtual bool NotificationsDeferred() const = 0;
  virtual void MarkPendingNotify() = 0;
  virtual void ClearPendingNotify() = 0;

  virtual already_AddRefed<nsIEventTarget> GetEventTarget() const
  {
    return nullptr;
  }

protected:
  virtual ~IProgressObserver() { }
};

} // namespace image
} // namespace mozilla

#endif // mozilla_image_IProgressObserver_h