cc: Add image decode control in the compositor.

cc/tiles/image_decode_controller.cc

Index: cc/tiles/image_decode_controller.cc
diff --git a/cc/tiles/image_decode_controller.cc b/cc/tiles/image_decode_controller.cc
index 70b6dc789257332e8a097b0c8d7158bc060c666e..adc690a2acc3e9a7d0165b1bc5648f43cd11e469 100644
--- a/cc/tiles/image_decode_controller.cc
+++ b/cc/tiles/image_decode_controller.cc
@@ -4,20 +4,32 @@
 
 #include "cc/tiles/image_decode_controller.h"
 
+#include "base/memory/discardable_memory.h"
 #include "cc/debug/devtools_instrumentation.h"
+#include "third_party/skia/include/core/SkCanvas.h"
 
 namespace cc {
 namespace {
 
+// The amount of memory we can lock ahead of time (100MB). This limit is only
+// used to inform the caller of the amount of space available in the cache. The
+// caller can still request tasks which can cause this limit to be breached.
+const size_t kLockedMemoryLimitBytes = 100 * 1024 * 1024;
+
+// The number of entries to keep around in the cache. This limit can be breached
+// if more items are locked. That is, locked items ignore this limit.
+const size_t kMaxItemsInCache = 100;
+
 class ImageDecodeTaskImpl : public ImageDecodeTask {
  public:
   ImageDecodeTaskImpl(ImageDecodeController* controller,
-                      const SkImage* image,
-                      int layer_id,
+                      const ImageDecodeController::ImageKey& image_key,
+                      const DrawImage& image,
                       uint64_t source_prepare_tiles_id)
       : controller_(controller),
-        image_(skia::SharePtr(image)),
-        layer_id_(layer_id),
+        image_key_(image_key),
+        image_(image),
+        image_ref_(skia::SharePtr(image.image())),
         source_prepare_tiles_id_(source_prepare_tiles_id) {}
 
   // Overridden from Task:
@@ -25,19 +37,14 @@ class ImageDecodeTaskImpl : public ImageDecodeTask {
     TRACE_EVENT1("cc", "ImageDecodeTaskImpl::RunOnWorkerThread",
                  "source_prepare_tiles_id", source_prepare_tiles_id_);
     devtools_instrumentation::ScopedImageDecodeTask image_decode_task(
-        image_.get());
-    controller_->DecodeImage(image_.get());
-
-    // Release the reference after decoding image to ensure that it is not kept
-    // alive unless needed.
-    image_.clear();
+        image_ref_.get());
+    controller_->DecodeImage(image_key_, image_);
   }
 
   // Overridden from TileTask:
   void ScheduleOnOriginThread(TileTaskClient* client) override {}
   void CompleteOnOriginThread(TileTaskClient* client) override {
-    controller_->OnImageDecodeTaskCompleted(layer_id_, image_.get(),
-                                            !HasFinishedRunning());
+    controller_->OnImageDecodeTaskCompleted(image_key_, !HasFinishedRunning());
   }
 
  protected:
@@ -45,8 +52,9 @@ class ImageDecodeTaskImpl : public ImageDecodeTask {
 
  private:
   ImageDecodeController* controller_;
-  skia::RefPtr<const SkImage> image_;
-  int layer_id_;
+  ImageDecodeController::ImageKey image_key_;
+  DrawImage image_;
+  skia::RefPtr<const SkImage> image_ref_;
   uint64_t source_prepare_tiles_id_;
 
   DISALLOW_COPY_AND_ASSIGN(ImageDecodeTaskImpl);
@@ -54,67 +62,342 @@ class ImageDecodeTaskImpl : public ImageDecodeTask {
 
 }  // namespace
 
-ImageDecodeController::ImageDecodeController() {}
+ImageDecodeController::ImageDecodeController()
+    : locked_images_budget_(kLockedMemoryLimitBytes) {}
 
 ImageDecodeController::~ImageDecodeController() {}
 
-scoped_refptr<ImageDecodeTask> ImageDecodeController::GetTaskForImage(
+scoped_refptr<ImageDecodeTask> ImageDecodeController::GetTaskForImageAndRef(
     const DrawImage& image,
-    int layer_id,
     uint64_t prepare_tiles_id) {
-  uint32_t generation_id = image.image()->uniqueID();
-  scoped_refptr<ImageDecodeTask>& decode_task =
-      image_decode_tasks_[layer_id][generation_id];
-  if (!decode_task)
-    decode_task = CreateTaskForImage(image.image(), layer_id, prepare_tiles_id);
-  return decode_task;
+  // If the image already exist or if we're going to create a task for it, then
+  // we need to ref this image. That means the image is or will be in the cache.
+  // When the ref goes to 0, it will be unpinned but will remain in the cache.
+  // If the image does not fit into the budget, then we don't ref this image,
+  // since it will be decoded at raster time which is when it will be
+  // temporarily put in the cache.
+  ImageKey key = ImageKey::FromDrawImage(image);
+
+  // Image already exists.
+  if (LockDecodedImageIfPossibleAndRef(key))
+    return nullptr;
+
+  base::AutoLock lock(lock_);
+
+  scoped_refptr<ImageDecodeTask>& task = pending_image_tasks_[key];
+  if (task) {
+    ++decoded_images_ref_counts_[key];
+    return task;
+  }
+
+  // Image won't fit into the cache, we'll scale it at raster time.
+  if (locked_images_budget_.AvailableMemoryBytes() < key.target_bytes())
+    return nullptr;
+
+  // We have account for memory usage when we create the task, not when the task
+  // puts an image in the cache, because we need to ensure that we don't create
+  // more tasks than we would have memory. That is, since tasks are created up
+  // front, it will be too late to count memory when they run.
+  locked_images_budget_.AddUsage(key.target_bytes());
+
+  task = CreateTaskForImage(key, image, prepare_tiles_id);
+
+  ++decoded_images_ref_counts_[key];
+  return task;
+}
+
+void ImageDecodeController::UnrefImage(const DrawImage& image) {
+  // When we unref the image, there are several situations we need to consider:
+  // 1. This image was not even scheduled to be in the locked cache, which means
+  //    that the ref count doesn't even exist.
+  // 2. The ref did not reach 0, which means we have to keep the image locked.
+  // 3. The ref reached 0, we should unlock it.
+  //   3a. The image isn't in the locked cache because we didn't get to decode
+  //       it yet (this is different from (1.) since it was actually scheduled
+  //       to be decoded).
+  //   3b. Unlock the image but keep it in list.
+  const ImageKey& key = ImageKey::FromDrawImage(image);
+
+  base::AutoLock lock(lock_);
+  auto ref_count_it = decoded_images_ref_counts_.find(key);
+  if (ref_count_it == decoded_images_ref_counts_.end())
+    return;
+
+  --ref_count_it->second;
+  if (ref_count_it->second == 0) {
+    decoded_images_ref_counts_.erase(key);
+    locked_images_budget_.SubtractUsage(key.target_bytes());
+
+    auto decoded_image_it =
+        std::find_if(decoded_images_.begin(), decoded_images_.end(),
+                     [key](const AnnotatedDecodedImage& decoded_image) {
+                       return key == decoded_image.first;
+                     });
+    // If we've never decoded the image before ref reached 0, then we wouldn't
+    // have it in our cache. This would happen if we canceled tasks.
+    if (decoded_image_it == decoded_images_.end())
+      return;
+    DCHECK(decoded_image_it->second->is_locked());
+    decoded_image_it->second->Unlock();
+  }
+}
+
+bool ImageDecodeController::LockDecodedImageIfPossibleAndRef(
+    const ImageKey& key) {
+  base::AutoLock lock(lock_);
+  auto decoded_images_iterator =
+      std::find_if(decoded_images_.begin(), decoded_images_.end(),
+                   [key](const AnnotatedDecodedImage& annotated_image) {
+                     return key == annotated_image.first;
+                   });
+  if (decoded_images_iterator == decoded_images_.end())
+    return false;
+
+  AnnotatedDecodedImage decoded_image = *decoded_images_iterator;
+  decoded_images_.erase(decoded_images_iterator);
+
+  // Figure out if the image is locked or try to lock it.
+  bool locked = decoded_image.second->is_locked();
+  if (!locked) {
+    locked = decoded_image.second->Lock();
+    if (!locked)
+      return false;
+
+    locked_images_budget_.AddUsage(key.target_bytes());
+  }
+
+  // If the image is locked or we locked it, then it has to be in the cache.
+  decoded_images_.push_back(decoded_image);
+  ++decoded_images_ref_counts_[key];
+  return true;
 }
 
 scoped_refptr<ImageDecodeTask> ImageDecodeController::CreateTaskForImage(
-    const SkImage* image,
-    int layer_id,
+    const ImageKey& key,
+    const DrawImage& image,
     uint64_t prepare_tiles_id) {
   return make_scoped_refptr(
-      new ImageDecodeTaskImpl(this, image, layer_id, prepare_tiles_id));
+      new ImageDecodeTaskImpl(this, key, image, prepare_tiles_id));
 }
 
-void ImageDecodeController::DecodeImage(const SkImage* image) {
-  image->preroll();
-}
+void ImageDecodeController::DecodeImage(const ImageKey& key,
+                                        const DrawImage& image) {
+  if (!CanHandleFilterQuality(image.filter_quality()))
+    return;
 
-void ImageDecodeController::AddLayerUsedCount(int layer_id) {
-  ++used_layer_counts_[layer_id];
+  scoped_refptr<DecodedImage> decoded_image =
+      DecodeImageInternal(key, image.image());
+
+  // Add the image to the cache. Don't add the budget usage, since it was
+  // already handled by the code that created the task for this decode.
+  base::AutoLock lock(lock_);
+  decoded_images_.push_back(AnnotatedDecodedImage(key, decoded_image));
 }
 
-void ImageDecodeController::SubtractLayerUsedCount(int layer_id) {
-  if (--used_layer_counts_[layer_id])
-    return;
+scoped_refptr<ImageDecodeController::DecodedImage>
+ImageDecodeController::DecodeImageInternal(const ImageKey& key,
+                                           const SkImage* image) {
+  // TODO(vmpstr, reed): Scale the image here without caching it in skia.
+  SkImageInfo info = SkImageInfo::MakeN32Premul(key.target_size().width(),
+                                                key.target_size().height());
+  scoped_ptr<base::DiscardableMemory> locked_memory =
+      base::DiscardableMemoryAllocator::GetInstance()
+          ->AllocateLockedDiscardableMemory(info.minRowBytes() * info.height());
 
-  // Clean up decode tasks once a layer is no longer used.
-  used_layer_counts_.erase(layer_id);
-  image_decode_tasks_.erase(layer_id);
+  skia::RefPtr<SkCanvas> canvas = skia::AdoptRef(SkCanvas::NewRasterDirect(
+      info, locked_memory->data(), info.minRowBytes()));
+  canvas->setMatrix(SkMatrix::MakeRectToRect(
+      SkRect::MakeWH(image->width(), image->height()),
+      SkRect::MakeWH(key.target_size().width(), key.target_size().height()),
+      SkMatrix::kFill_ScaleToFit));
+  canvas->clear(SK_ColorTRANSPARENT);
+  SkPaint paint;
+  paint.setFilterQuality(kHigh_SkFilterQuality);
+  canvas->drawImage(image, 0, 0, &paint);
+  canvas->flush();
+
+  return make_scoped_refptr(new DecodedImage(info, locked_memory.Pass()));
 }
 
-void ImageDecodeController::OnImageDecodeTaskCompleted(int layer_id,
-                                                       const SkImage* image,
+void ImageDecodeController::OnImageDecodeTaskCompleted(const ImageKey& key,
                                                        bool was_canceled) {
-  // If the task has successfully finished, then keep the task until the layer
-  // is no longer in use. This ensures that we only decode a image once.
-  // TODO(vmpstr): Remove this when decode lifetime is controlled by cc.
-  if (!was_canceled)
-    return;
+  pending_image_tasks_.erase(key);
+}
 
-  // Otherwise, we have to clean up the task so that a new one can be created if
-  // we need to decode the image again.
-  LayerImageTaskMap::iterator layer_it = image_decode_tasks_.find(layer_id);
-  if (layer_it == image_decode_tasks_.end())
-    return;
+DecodedDrawImage ImageDecodeController::GetDecodedImage(
+    const DrawImage& image) {
+  if (!CanHandleFilterQuality(image.filter_quality())) {
+    return DecodedDrawImage(image.image(), SkSize::Make(1.f, 1.f),
+                            image.filter_quality());
+  }
 
-  ImageTaskMap& image_tasks = layer_it->second;
-  ImageTaskMap::iterator task_it = image_tasks.find(image->uniqueID());
-  if (task_it == image_tasks.end())
+  ImageKey key = ImageKey::FromDrawImage(image);
+
+  base::AutoLock lock(lock_);
+  auto decoded_images_iterator =
+      std::find_if(decoded_images_.begin(), decoded_images_.end(),
+                   [key](const AnnotatedDecodedImage& annotated_image) {
+                     return key == annotated_image.first;
+                   });
+  scoped_refptr<DecodedImage> decoded_image;
+  if (decoded_images_iterator != decoded_images_.end()) {
+    decoded_image = decoded_images_iterator->second;
+    if (!decoded_image->is_locked()) {
+      if (decoded_image->Lock()) {
+        locked_images_budget_.AddUsage(key.target_bytes());
+      } else {
+        decoded_images_.erase(decoded_images_iterator);
+        decoded_image = nullptr;
+      }
+    }
+  }
+
+  if (!decoded_image) {
+    // This means that we didn't have an image task to decode this (otherwise it
+    // would have run and locked the image already). So, we need to decode/scale
+    // in place.
+    decoded_image = DecodeImageInternal(key, image.image());
+    decoded_images_.push_back(AnnotatedDecodedImage(key, decoded_image));
+    locked_images_budget_.AddUsage(key.target_bytes());
+  }
+
+  DCHECK(decoded_image->is_locked()) << key.ToString();
+  float x_scale =
+      key.target_size().width() / static_cast<float>(image.image()->width());
+  float y_scale =
+      key.target_size().height() / static_cast<float>(image.image()->height());
+
+  ++decoded_images_ref_counts_[key];
+  return DecodedDrawImage(decoded_image->image(),
+                          SkSize::Make(x_scale, y_scale), kLow_SkFilterQuality);
+}
+
+void ImageDecodeController::DrawWithImageFinished(const DrawImage& image) {
+  if (!CanHandleFilterQuality(image.filter_quality()))
     return;
-  image_tasks.erase(task_it);
+  UnrefImage(image);
+}
+
+bool ImageDecodeController::CanHandleFilterQuality(
+    SkFilterQuality filter_quality) {
+  DCHECK(filter_quality != kNone_SkFilterQuality);
+  // We don't need to handle low quality filters.
+  if (filter_quality == kLow_SkFilterQuality)
+    return false;
+  // TODO(vmpstr): We need to start caching mipmaps for medium quality and
+  // caching the interpolated values from those. For now, we don't have this.
+  if (filter_quality == kMedium_SkFilterQuality)
+    return false;
+  DCHECK(filter_quality == kHigh_SkFilterQuality);
+  return true;
+}
+
+void ImageDecodeController::ReduceCacheUsage() {
+  base::AutoLock lock(lock_);
+  size_t num_to_remove = (decoded_images_.size() > kMaxItemsInCache)
+                             ? (decoded_images_.size() - kMaxItemsInCache)
+                             : 0;
+  for (auto it = decoded_images_.begin();
+       num_to_remove != 0 && it != decoded_images_.end();) {
+    if (it->second->is_locked()) {
+      ++it;
+      continue;
+    }
+
+    it = decoded_images_.erase(it);
+    --num_to_remove;
+  }
+}
+
+// ImageDecodeControllerKey
+ImageDecodeControllerKey ImageDecodeControllerKey::FromDrawImage(
+    const DrawImage& image) {
+  gfx::Size target_size(std::abs(SkScalarRoundToInt(image.image()->width() *
+                                                    image.scale().width())),
+                        std::abs(SkScalarRoundToInt(image.image()->height() *
+                                                    image.scale().height())));
+  return ImageDecodeControllerKey(image.image()->uniqueID(), target_size,
+                                  image.filter_quality());
+}
+
+ImageDecodeControllerKey::ImageDecodeControllerKey(
+    uint32_t image_id,
+    const gfx::Size& size,
+    SkFilterQuality filter_quality)
+    : image_id_(image_id), size_(size), filter_quality_(filter_quality) {}
+
+std::string ImageDecodeControllerKey::ToString() const {
+  std::ostringstream str;
+  str << "id[" << image_id_ << "] size[" << size_.width() << "x"
+      << size_.height() << "] filter_quality[" << filter_quality_ << "]";
+  return str.str();
+}
+
+// TODO(vmpstr): Not sure if this needs to do something. It could have some
+// extra state to DCHECK if we pass it DecodedImage object as the context.
+static void noop(const void* pixels, void* context) {}
+
+// DecodedImage
+ImageDecodeController::DecodedImage::DecodedImage(
+    const SkImageInfo& info,
+    scoped_ptr<base::DiscardableMemory> memory)
+    : locked_(true), image_info_(info), memory_(memory.Pass()) {
+  CreateImageFromLockedMemory();
+}
+
+ImageDecodeController::DecodedImage::~DecodedImage() {}
+
+bool ImageDecodeController::DecodedImage::Lock() {
+  DCHECK(!locked_);
+  bool success = memory_->Lock();
+  if (!success)
+    return false;
+  locked_ = true;
+  CreateImageFromLockedMemory();
+  return true;
+}
+
+void ImageDecodeController::DecodedImage::Unlock() {
+  DCHECK(locked_);
+  image_.clear();
+  memory_->Unlock();
+  locked_ = false;
+}
+
+void ImageDecodeController::DecodedImage::CreateImageFromLockedMemory() {
+  image_ = skia::AdoptRef(SkImage::NewFromRaster(
+      image_info_, memory_->data(), image_info_.minRowBytes(), &noop, nullptr));
+}
+
+// MemoryBudget
+ImageDecodeController::MemoryBudget::MemoryBudget(size_t limit_bytes)
+    : limit_bytes_(limit_bytes), current_usage_bytes_(0u) {}
+
+size_t ImageDecodeController::MemoryBudget::AvailableMemoryBytes() const {
+  size_t usage = GetCurrentUsageSafe();
+  return usage >= limit_bytes_ ? 0u : (limit_bytes_ - usage);
+}
+
+void ImageDecodeController::MemoryBudget::AddUsage(size_t usage) {
+  current_usage_bytes_ += usage;
+}
+
+void ImageDecodeController::MemoryBudget::SubtractUsage(size_t usage) {
+  DCHECK_GE(current_usage_bytes_.ValueOrDefault(0u), usage);
+  current_usage_bytes_ -= usage;
+}
+
+void ImageDecodeController::MemoryBudget::ResetUsage() {
+  current_usage_bytes_ = 0;
+}
+
+bool ImageDecodeController::MemoryBudget::NeedsReset() const {
+  return !current_usage_bytes_.IsValid();
+}
+
+size_t ImageDecodeController::MemoryBudget::GetCurrentUsageSafe() const {
+  return current_usage_bytes_.ValueOrDefault(
+      std::numeric_limits<size_t>::max());
 }
 
 }  // namespace cc