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ui/gfx/image/mojo/image_skia_struct_traits.cc

+// Copyright 2017 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/mojo/image_skia_struct_traits.h"
+
+#include <string.h>
+
+#include "base/logging.h"
+#include "skia/public/interfaces/bitmap_skbitmap_struct_traits.h"
+
+namespace mojo {
+
+namespace {
+
+// Strip out empty image reps. Needed because ImageSkia::image_reps does not

[msw, 2017/03/24 17:59:33]

I wonder if filtering out empty image reps is an unnecessary step that makes our
traits code more complicated than it should be. What's the harm in keeping
these? Wouldn't that be more like the c++ class?

[xiyuan, 2017/03/24 18:36:53]

My intention is to save some data to be transported. Maybe not worth it.

Changed to just use what C++ class provides to keep it more straightforward.

+// filter out empty SkBitmap.
+void GetNonemptyImageReps(const gfx::ImageSkia& image,
+                          std::vector<gfx::ImageSkiaRep>* out_reps) {
+  for (auto& input_rep : image.image_reps()) {
+    if (!StructTraits<gfx::mojom::ImageSkiaRepDataView,
+                      gfx::ImageSkiaRep>::IsNull(input_rep)) {
+      out_reps->emplace_back(input_rep);
+    }
+  }
+}
+
+}  // namespace
+
+StructTraits<gfx::mojom::SharedBufferSkBitmapDataView,
+             SkBitmap>::Context::Context() = default;
+StructTraits<gfx::mojom::SharedBufferSkBitmapDataView,
+             SkBitmap>::Context::~Context() = default;
+
+// static
+void* StructTraits<gfx::mojom::SharedBufferSkBitmapDataView,
+                   SkBitmap>::SetUpContext(const SkBitmap& input) {
+  // Shared buffer is not a good way for huge images. Consider alternatives.
+  DCHECK_LT(input.width() * input.height(), 4000 * 4000);
+
+  const std::vector<uint8_t> serialized_sk_bitmap(
+      skia::mojom::Bitmap::Serialize(&input));
+
+  // Use a context to serialize the bitmap to a shared buffer only once.
+  Context* context = new Context;
+  context->buffer_byte_size = serialized_sk_bitmap.size();
+  context->shared_buffer_handle =
+      mojo::SharedBufferHandle::Create(context->buffer_byte_size);
+  mojo::ScopedSharedBufferMapping mapping =
+      context->shared_buffer_handle->Map(context->buffer_byte_size);
+  memcpy(mapping.get(), serialized_sk_bitmap.data(), context->buffer_byte_size);
+  return context;
+}
+
+// static
+void StructTraits<gfx::mojom::SharedBufferSkBitmapDataView,
+                  SkBitmap>::TearDownContext(const SkBitmap& input,
+                                             void* context) {
+  delete static_cast<Context*>(context);
+}
+
+// static
+mojo::ScopedSharedBufferHandle
+StructTraits<gfx::mojom::SharedBufferSkBitmapDataView,
+             SkBitmap>::shared_buffer_handle(const SkBitmap& input,
+                                             void* context) {
+  return (static_cast<Context*>(context))
+      ->shared_buffer_handle->Clone(
+          mojo::SharedBufferHandle::AccessMode::READ_ONLY);
+}
+
+// static
+uint64_t StructTraits<gfx::mojom::SharedBufferSkBitmapDataView,
+                      SkBitmap>::buffer_byte_size(const SkBitmap& input,
+                                                  void* context) {
+  return (static_cast<Context*>(context))->buffer_byte_size;
+}
+
+// static
+bool StructTraits<gfx::mojom::SharedBufferSkBitmapDataView, SkBitmap>::Read(
+    gfx::mojom::SharedBufferSkBitmapDataView data,
+    SkBitmap* out) {
+  mojo::ScopedSharedBufferHandle shared_buffer_handle =
+      data.TakeSharedBufferHandle();
+  if (!shared_buffer_handle.is_valid())
+    return false;
+
+  mojo::ScopedSharedBufferMapping mapping =
+      shared_buffer_handle->Map(data.buffer_byte_size());
+  if (!mapping)
+    return false;
+
+  const std::vector<uint8_t> serialized_sk_bitmap(
+      static_cast<uint8_t*>(mapping.get()),
+      static_cast<uint8_t*>(mapping.get()) + data.buffer_byte_size());
+
+  return skia::mojom::Bitmap::Deserialize(serialized_sk_bitmap, out);
+}
+
+// static
+float StructTraits<gfx::mojom::ImageSkiaRepDataView, gfx::ImageSkiaRep>::scale(
+    const gfx::ImageSkiaRep& input) {
+  const float scale = input.unscaled() ? 0.0f : input.scale();
+  DCHECK_GE(scale, 0.0f);
+
+  return scale;
+}
+
+// static
+bool StructTraits<gfx::mojom::ImageSkiaRepDataView, gfx::ImageSkiaRep>::Read(
+    gfx::mojom::ImageSkiaRepDataView data,
+    gfx::ImageSkiaRep* out) {
+  // An acceptable scale must be greater than or equal to 0.
+  if (data.scale() < 0)
+    return false;
+
+  SkBitmap bitmap;
+  if (!data.ReadBitmap(&bitmap))
+    return false;
+
+  *out = gfx::ImageSkiaRep(bitmap, data.scale());
+  return true;
+}
+
+// static
+void* StructTraits<gfx::mojom::ImageSkiaDataView, gfx::ImageSkia>::SetUpContext(
+    const gfx::ImageSkia& input) {
+  // Trigger the image to load everything.
+  input.EnsureRepsForSupportedScales();
+
+  // Use a context to return a stable list of ImageSkiaRep objects. That is,
+  // multiple calls of image_reps() should return exactly the same list of
+  // ImageSkiaRep objects. So that ImageSkiaRep with the same backing pixel
+  // buffer is properly serialized and only once.
+  auto* image_reps = new std::vector<gfx::ImageSkiaRep>;
+  GetNonemptyImageReps(input, image_reps);
+
+  return image_reps;
+}
+
+// static
+void StructTraits<gfx::mojom::ImageSkiaDataView,
+                  gfx::ImageSkia>::TearDownContext(const gfx::ImageSkia& input,
+                                                   void* context) {
+  delete static_cast<std::vector<gfx::ImageSkiaRep>*>(context);
+}
+
+// static
+const std::vector<gfx::ImageSkiaRep>&
+StructTraits<gfx::mojom::ImageSkiaDataView, gfx::ImageSkia>::image_reps(
+    const gfx::ImageSkia& input,
+    void* context) {
+  // See the comment in SetUpContext regarding context usage.
+  return *(static_cast<std::vector<gfx::ImageSkiaRep>*>(context));
+}
+
+// static
+bool StructTraits<gfx::mojom::ImageSkiaDataView, gfx::ImageSkia>::IsNull(
+    const gfx::ImageSkia& input) {
+  std::vector<gfx::ImageSkiaRep> image_reps;
+  GetNonemptyImageReps(input, &image_reps);
+  return image_reps.empty();
+}
+
+// static
+bool StructTraits<gfx::mojom::ImageSkiaDataView, gfx::ImageSkia>::Read(
+    gfx::mojom::ImageSkiaDataView data,
+    gfx::ImageSkia* out) {
+  DCHECK(out->isNull());
+
+  std::vector<gfx::ImageSkiaRep> image_reps;
+  if (!data.ReadImageReps(&image_reps))
+    return false;
+
+  for (const auto& image_rep : image_reps)
+    out->AddRepresentation(image_rep);
+
+  if (out->isNull())
+    return false;
+
+  out->SetReadOnly();
+  return true;
+}
+
+}  // namespace mojo