third_party/blink/renderer/core/css/css_image_generator_value.h

/*
 * Copyright (C) 2008 Apple Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef THIRD_PARTY_BLINK_RENDERER_CORE_CSS_CSS_IMAGE_GENERATOR_VALUE_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_CSS_CSS_IMAGE_GENERATOR_VALUE_H_

#include <map>
#include "base/memory/scoped_refptr.h"
#include "third_party/blink/renderer/core/core_export.h"
#include "third_party/blink/renderer/core/css/css_value.h"
#include "third_party/blink/renderer/platform/geometry/float_size.h"
#include "third_party/blink/renderer/platform/heap/self_keep_alive.h"
#include "third_party/blink/renderer/platform/wtf/allocator.h"
#include "third_party/blink/renderer/platform/wtf/casting.h"
#include "third_party/blink/renderer/platform/wtf/hash_map.h"

namespace blink {

class Document;
class Image;
class ComputedStyle;
class ImageResourceObserver;

// These maps do not contain many objects because we do not expect any
// particular CSSGeneratedImageValue to have clients at many different
// sizes at any given time.
using ImageSizeCountMap = HashCountedSet<FloatSize>;
using GeneratedImageMap = HashMap<FloatSize, scoped_refptr<Image>>;

class GeneratedImageCache {
  DISALLOW_NEW();

 public:
  void AddSize(const FloatSize&);
  void RemoveSize(const FloatSize&);

  Image* GetImage(const FloatSize&) const;
  void PutImage(const FloatSize&, scoped_refptr<Image>);

 private:
  // A count of how many times a given image size is in use.
  ImageSizeCountMap sizes_;

  // A cache of Image objects by image size.
  GeneratedImageMap images_;
};

struct SizeAndCount {
  DISALLOW_NEW();
  SizeAndCount() : size(), count(0) {}

  // The non-zero size associated with this client. A client must only
  // ever be present at one non-zero size, with as many zero sizes as it wants.
  FloatSize size;

  // The net number of times this client has been added.
  int count;
};

using ClientSizeCountMap = HashMap<const ImageResourceObserver*, SizeAndCount>;

class CORE_EXPORT CSSImageGeneratorValue : public CSSValue {
 public:
  ~CSSImageGeneratorValue();

  void AddClient(const ImageResourceObserver*);

  void RemoveClient(const ImageResourceObserver*);
  // The |target_size| is the desired image size. Background images should not
  // be snapped. In other case the target size must be pixel snapped already.
  scoped_refptr<Image> GetImage(const ImageResourceObserver&,
                                const Document&,
                                const ComputedStyle&,
                                const FloatSize& target_size);

  bool IsFixedSize() const;
  FloatSize FixedSize(const Document&, const FloatSize& default_object_size);

  bool IsPending() const;
  bool KnownToBeOpaque(const Document&, const ComputedStyle&) const;

  void LoadSubimages(const Document&);

  CSSImageGeneratorValue* ValueWithURLsMadeAbsolute();

  void TraceAfterDispatch(blink::Visitor* visitor) {
    CSSValue::TraceAfterDispatch(visitor);
  }

 protected:
  explicit CSSImageGeneratorValue(ClassType);

  Image* GetImage(const ImageResourceObserver*, const FloatSize&) const;
  void PutImage(const FloatSize&, scoped_refptr<Image>) const;
  const ClientSizeCountMap& Clients() const { return clients_; }

  // A map from LayoutObjects (with entry count) to image sizes.
  mutable ClientSizeCountMap clients_;

  // Cached image instances.
  mutable GeneratedImageCache cached_images_;

  // TODO(Oilpan): when/if we can make the layoutObject point directly to the
  // CSSImageGenerator value using a member we don't need to have this hack
  // where we keep a persistent to the instance as long as there are clients in
  // the ClientSizeCountMap.
  SelfKeepAlive<CSSImageGeneratorValue> keep_alive_;
};

template <>
struct DowncastTraits<CSSImageGeneratorValue> {
  static bool AllowFrom(const CSSValue& value) {
    return value.IsImageGeneratorValue();
  }
};

}  // namespace blink

#endif  // THIRD_PARTY_BLINK_RENDERER_CORE_CSS_CSS_IMAGE_GENERATOR_VALUE_H_