root/ui/gfx/image/image_skia.cc

DEFINITIONS

1. NullImageRep
2. read_only_
3. read_only_
4. has_source
5. image_reps
6. size
7. read_only
8. DeleteSource
9. SetReadOnly
10. DetachFromThread
11. CanModify
12. CanRead
13. FindRepresentation
14. SetSupportedScales
15. GetSupportedScales
16. GetMaxSupportedScale
17. CreateFrom1xBitmap
18. DeepCopy
19. BackedBySameObjectAs
20. AddRepresentation
21. RemoveRepresentation
22. HasRepresentation
23. GetRepresentation
24. SetReadOnly
25. MakeThreadSafe
26. IsThreadSafe
27. width
28. size
29. height
30. image_reps
31. EnsureRepsForSupportedScales
32. Init
33. GetBitmap
34. CanRead
35. CanModify
36. DetachStorageFromThread

// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "ui/gfx/image/image_skia.h"

#include <algorithm>
#include <cmath>
#include <limits>

#include "base/logging.h"
#include "base/memory/scoped_ptr.h"
#include "base/threading/non_thread_safe.h"
#include "ui/gfx/image/image_skia_operations.h"
#include "ui/gfx/image/image_skia_source.h"
#include "ui/gfx/rect.h"
#include "ui/gfx/size.h"
#include "ui/gfx/skia_util.h"

namespace gfx {
namespace {

// static
gfx::ImageSkiaRep& NullImageRep() {
  CR_DEFINE_STATIC_LOCAL(ImageSkiaRep, null_image_rep, ());
  return null_image_rep;
}

std::vector<float>* g_supported_scales = NULL;
}  // namespace

namespace internal {
namespace {

class Matcher {
 public:
  explicit Matcher(float scale) : scale_(scale) {
  }

  bool operator()(const ImageSkiaRep& rep) const {
    return rep.scale() == scale_;
  }

 private:
  float scale_;
};

}  // namespace

// A helper class such that ImageSkia can be cheaply copied. ImageSkia holds a
// refptr instance of ImageSkiaStorage, which in turn holds all of ImageSkia's
// information. Having both |base::RefCountedThreadSafe| and
// |base::NonThreadSafe| may sounds strange but necessary to turn
// the 'thread-non-safe modifiable ImageSkiaStorage' into
// the 'thread-safe read-only ImageSkiaStorage'.
class ImageSkiaStorage : public base::RefCountedThreadSafe<ImageSkiaStorage>,
                         public base::NonThreadSafe {
 public:
  ImageSkiaStorage(ImageSkiaSource* source, const gfx::Size& size)
      : source_(source),
        size_(size),
        read_only_(false) {
  }

  ImageSkiaStorage(ImageSkiaSource* source, float scale)
      : source_(source),
        read_only_(false) {
    ImageSkia::ImageSkiaReps::iterator it = FindRepresentation(scale, true);
    if (it == image_reps_.end() || it->is_null())
      source_.reset();
    else
      size_.SetSize(it->GetWidth(), it->GetHeight());
  }

  bool has_source() const { return source_.get() != NULL; }

  std::vector<gfx::ImageSkiaRep>& image_reps() { return image_reps_; }

  const gfx::Size& size() const { return size_; }

  bool read_only() const { return read_only_; }

  void DeleteSource() {
    source_.reset();
  }

  void SetReadOnly() {
    read_only_ = true;
  }

  void DetachFromThread() {
    base::NonThreadSafe::DetachFromThread();
  }

  // Checks if the current thread can safely modify the storage.
  bool CanModify() const {
    return !read_only_ && CalledOnValidThread();
  }

  // Checks if the current thread can safely read the storage.
  bool CanRead() const {
    return (read_only_ && !source_.get()) || CalledOnValidThread();
  }

  // Returns the iterator of the image rep whose density best matches
  // |scale|. If the image for the |scale| doesn't exist in the storage and
  // |storage| is set, it fetches new image by calling
  // |ImageSkiaSource::GetImageForScale|. If the source returns the image with
  // different scale (if the image doesn't exist in resource, for example), it
  // will fallback to closest image rep.
  std::vector<ImageSkiaRep>::iterator FindRepresentation(
      float scale, bool fetch_new_image) const {
    ImageSkiaStorage* non_const = const_cast<ImageSkiaStorage*>(this);

    ImageSkia::ImageSkiaReps::iterator closest_iter =
        non_const->image_reps().end();
    ImageSkia::ImageSkiaReps::iterator exact_iter =
        non_const->image_reps().end();
    float smallest_diff = std::numeric_limits<float>::max();
    for (ImageSkia::ImageSkiaReps::iterator it =
             non_const->image_reps().begin();
         it < image_reps_.end(); ++it) {
      if (it->scale() == scale) {
        // found exact match
        fetch_new_image = false;
        if (it->is_null())
          continue;
        exact_iter = it;
        break;
      }
      float diff = std::abs(it->scale() - scale);
      if (diff < smallest_diff && !it->is_null()) {
        closest_iter = it;
        smallest_diff = diff;
      }
    }

    if (fetch_new_image && source_.get()) {
      DCHECK(CalledOnValidThread()) <<
          "An ImageSkia with the source must be accessed by the same thread.";

      ImageSkiaRep image = source_->GetImageForScale(scale);

      // If the source returned the new image, store it.
      if (!image.is_null() &&
          std::find_if(image_reps_.begin(), image_reps_.end(),
                       Matcher(image.scale())) == image_reps_.end()) {
        non_const->image_reps().push_back(image);
      }

      // If the result image's scale isn't same as the expected scale, create
      // null ImageSkiaRep with the |scale| so that the next lookup will
      // fallback to the closest scale.
      if (image.is_null() || image.scale() != scale) {
        non_const->image_reps().push_back(ImageSkiaRep(SkBitmap(), scale));
      }

      // image_reps_ must have the exact much now, so find again.
      return FindRepresentation(scale, false);
    }
    return exact_iter != image_reps_.end() ? exact_iter : closest_iter;
  }

 private:
  virtual ~ImageSkiaStorage() {
    // We only care if the storage is modified by the same thread.
    // Don't blow up even if someone else deleted the ImageSkia.
    DetachFromThread();
  }

  // Vector of bitmaps and their associated scale.
  std::vector<gfx::ImageSkiaRep> image_reps_;

  scoped_ptr<ImageSkiaSource> source_;

  // Size of the image in DIP.
  gfx::Size size_;

  bool read_only_;

  friend class base::RefCountedThreadSafe<ImageSkiaStorage>;
};

}  // internal

ImageSkia::ImageSkia() : storage_(NULL) {
}

ImageSkia::ImageSkia(ImageSkiaSource* source, const gfx::Size& size)
    : storage_(new internal::ImageSkiaStorage(source, size)) {
  DCHECK(source);
  // No other thread has reference to this, so it's safe to detach the thread.
  DetachStorageFromThread();
}

ImageSkia::ImageSkia(ImageSkiaSource* source, float scale)
    : storage_(new internal::ImageSkiaStorage(source, scale)) {
  DCHECK(source);
  if (!storage_->has_source())
    storage_ = NULL;
  // No other thread has reference to this, so it's safe to detach the thread.
  DetachStorageFromThread();
}

ImageSkia::ImageSkia(const ImageSkiaRep& image_rep) {
  Init(image_rep);
  // No other thread has reference to this, so it's safe to detach the thread.
  DetachStorageFromThread();
}

ImageSkia::ImageSkia(const ImageSkia& other) : storage_(other.storage_) {
}

ImageSkia& ImageSkia::operator=(const ImageSkia& other) {
  storage_ = other.storage_;
  return *this;
}

ImageSkia::~ImageSkia() {
}

// static
void ImageSkia::SetSupportedScales(const std::vector<float>& supported_scales) {
  if (g_supported_scales != NULL)
    delete g_supported_scales;
  g_supported_scales = new std::vector<float>(supported_scales);
  std::sort(g_supported_scales->begin(), g_supported_scales->end());
}

// static
const std::vector<float>& ImageSkia::GetSupportedScales() {
  DCHECK(g_supported_scales != NULL);
  return *g_supported_scales;
}

// static
float ImageSkia::GetMaxSupportedScale() {
  return g_supported_scales->back();
}

// static
ImageSkia ImageSkia::CreateFrom1xBitmap(const SkBitmap& bitmap) {
  return ImageSkia(ImageSkiaRep(bitmap, 1.0f));
}

scoped_ptr<ImageSkia> ImageSkia::DeepCopy() const {
  ImageSkia* copy = new ImageSkia;
  if (isNull())
    return scoped_ptr<ImageSkia>(copy);

  CHECK(CanRead());

  std::vector<gfx::ImageSkiaRep>& reps = storage_->image_reps();
  for (std::vector<gfx::ImageSkiaRep>::iterator iter = reps.begin();
       iter != reps.end(); ++iter) {
    copy->AddRepresentation(*iter);
  }
  // The copy has its own storage. Detach the copy from the current
  // thread so that other thread can use this.
  if (!copy->isNull())
    copy->storage_->DetachFromThread();
  return scoped_ptr<ImageSkia>(copy);
}

bool ImageSkia::BackedBySameObjectAs(const gfx::ImageSkia& other) const {
  return storage_.get() == other.storage_.get();
}

void ImageSkia::AddRepresentation(const ImageSkiaRep& image_rep) {
  DCHECK(!image_rep.is_null());

  // TODO(oshima): This method should be called |SetRepresentation|
  // and replace the existing rep if there is already one with the
  // same scale so that we can guarantee that a ImageSkia instance contains only
  // one image rep per scale. This is not possible now as ImageLoader currently
  // stores need this feature, but this needs to be fixed.
  if (isNull()) {
    Init(image_rep);
  } else {
    CHECK(CanModify());
    storage_->image_reps().push_back(image_rep);
  }
}

void ImageSkia::RemoveRepresentation(float scale) {
  if (isNull())
    return;
  CHECK(CanModify());

  ImageSkiaReps& image_reps = storage_->image_reps();
  ImageSkiaReps::iterator it =
      storage_->FindRepresentation(scale, false);
  if (it != image_reps.end() && it->scale() == scale)
    image_reps.erase(it);
}

bool ImageSkia::HasRepresentation(float scale) const {
  if (isNull())
    return false;
  CHECK(CanRead());

  ImageSkiaReps::iterator it = storage_->FindRepresentation(scale, false);
  return (it != storage_->image_reps().end() && it->scale() == scale);
}

const ImageSkiaRep& ImageSkia::GetRepresentation(float scale) const {
  if (isNull())
    return NullImageRep();

  CHECK(CanRead());

  ImageSkiaReps::iterator it = storage_->FindRepresentation(scale, true);
  if (it == storage_->image_reps().end())
    return NullImageRep();

  return *it;
}

void ImageSkia::SetReadOnly() {
  CHECK(storage_.get());
  storage_->SetReadOnly();
  DetachStorageFromThread();
}

void ImageSkia::MakeThreadSafe() {
  CHECK(storage_.get());
  EnsureRepsForSupportedScales();
  // Delete source as we no longer needs it.
  if (storage_.get())
    storage_->DeleteSource();
  storage_->SetReadOnly();
  CHECK(IsThreadSafe());
}

bool ImageSkia::IsThreadSafe() const {
  return !storage_.get() || (storage_->read_only() && !storage_->has_source());
}

int ImageSkia::width() const {
  return isNull() ? 0 : storage_->size().width();
}

gfx::Size ImageSkia::size() const {
  return gfx::Size(width(), height());
}

int ImageSkia::height() const {
  return isNull() ? 0 : storage_->size().height();
}

std::vector<ImageSkiaRep> ImageSkia::image_reps() const {
  if (isNull())
    return std::vector<ImageSkiaRep>();

  CHECK(CanRead());

  ImageSkiaReps internal_image_reps = storage_->image_reps();
  // Create list of image reps to return, skipping null image reps which were
  // added for caching purposes only.
  ImageSkiaReps image_reps;
  for (ImageSkiaReps::iterator it = internal_image_reps.begin();
       it != internal_image_reps.end(); ++it) {
    if (!it->is_null())
      image_reps.push_back(*it);
  }

  return image_reps;
}

void ImageSkia::EnsureRepsForSupportedScales() const {
  DCHECK(g_supported_scales != NULL);
  // Don't check ReadOnly because the source may generate images
  // even for read only ImageSkia. Concurrent access will be protected
  // by |DCHECK(CalledOnValidThread())| in FindRepresentation.
  if (storage_.get() && storage_->has_source()) {
    for (std::vector<float>::const_iterator it = g_supported_scales->begin();
         it != g_supported_scales->end(); ++it)
      storage_->FindRepresentation(*it, true);
  }
}

void ImageSkia::Init(const ImageSkiaRep& image_rep) {
  // TODO(pkotwicz): The image should be null whenever image rep is null.
  if (image_rep.sk_bitmap().empty()) {
    storage_ = NULL;
    return;
  }
  storage_ = new internal::ImageSkiaStorage(
      NULL, gfx::Size(image_rep.GetWidth(), image_rep.GetHeight()));
  storage_->image_reps().push_back(image_rep);
}

SkBitmap& ImageSkia::GetBitmap() const {
  if (isNull()) {
    // Callers expect a ImageSkiaRep even if it is |isNull()|.
    // TODO(pkotwicz): Fix this.
    return NullImageRep().mutable_sk_bitmap();
  }

  // TODO(oshima): This made a few tests flaky on Windows.
  // Fix the root cause and re-enable this. crbug.com/145623.
#if !defined(OS_WIN)
  CHECK(CanRead());
#endif

  ImageSkiaReps::iterator it = storage_->FindRepresentation(1.0f, true);
  if (it != storage_->image_reps().end())
    return it->mutable_sk_bitmap();
  return NullImageRep().mutable_sk_bitmap();
}

bool ImageSkia::CanRead() const {
  return !storage_.get() || storage_->CanRead();
}

bool ImageSkia::CanModify() const {
  return !storage_.get() || storage_->CanModify();
}

void ImageSkia::DetachStorageFromThread() {
  if (storage_.get())
    storage_->DetachFromThread();
}

}  // namespace gfx