Add a class to replace ImageLoadingTracker with a nicer API.

chrome/browser/extensions/image_utils.cc

Index: chrome/browser/extensions/image_utils.cc
diff --git a/chrome/browser/extensions/image_utils.cc b/chrome/browser/extensions/image_utils.cc
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index 0000000000000000000000000000000000000000..b72ea41d97c4c35256abf9173fa97fa38b0226bc
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+++ b/chrome/browser/extensions/image_utils.cc
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+// 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 "chrome/browser/extensions/image_utils.h"
+
+#include "base/callback.h"
+#include "base/file_util.h"
+#include "base/path_service.h"
+#include "base/threading/sequenced_worker_pool.h"
+#include "chrome/common/chrome_notification_types.h"
+#include "chrome/common/chrome_paths.h"
+#include "chrome/common/extensions/extension.h"
+#include "content/public/browser/browser_thread.h"
+#include "content/public/browser/notification_observer.h"
+#include "content/public/browser/notification_registrar.h"
+#include "content/public/browser/notification_service.h"
+#include "grit/component_extension_resources_map.h"
+#include "grit/theme_resources.h"
+#include "skia/ext/image_operations.h"
+#include "third_party/skia/include/core/SkBitmap.h"
+#include "ui/base/resource/resource_bundle.h"
+#include "ui/gfx/image/image.h"
+#include "ui/gfx/image/image_skia.h"
+#include "webkit/glue/image_decoder.h"
+
+using content::BrowserThread;
+using extension_image_utils::ImageRepresentation;
+using extensions::Extension;
+
+namespace {
+
+bool ShouldResizeImageRepresentation(
+    ImageRepresentation::ResizeCondition resize_method,
+    const gfx::Size& decoded_size,
+    const gfx::Size& desired_size) {
+  switch (resize_method) {
+    case ImageRepresentation::ALWAYS_RESIZE:
+      return decoded_size != desired_size;
+    case ImageRepresentation::RESIZE_WHEN_LARGER:
+      return decoded_size.width() > desired_size.width() ||
+             decoded_size.height() > desired_size.height();
+    default:
+      NOTREACHED();
+      return false;
+  }
+}
+
+SkBitmap ResizeIfNeeded(const SkBitmap& bitmap,
+                        const ImageRepresentation& image_info) {
+  gfx::Size original_size(bitmap.width(), bitmap.height());
+  if (ShouldResizeImageRepresentation(image_info.resize_condition,
+                                      original_size,
+                                      image_info.desired_size)) {
+    return skia::ImageOperations::Resize(
+        bitmap, skia::ImageOperations::RESIZE_LANCZOS3,
+        image_info.desired_size.width(), image_info.desired_size.height());
+  }
+
+  return bitmap;
+}
+
+void LoadResourceOnUIThread(int resource_id, SkBitmap* bitmap) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+
+  gfx::ImageSkia image(
+      *ResourceBundle::GetSharedInstance().GetImageSkiaNamed(resource_id));
+  image.MakeThreadSafe();
+  *bitmap = *image.bitmap();
+}
+
+void LoadImageOnBlockingPool(const ImageRepresentation& image_info,
+                             SkBitmap* bitmap) {
+  DCHECK(BrowserThread::GetBlockingPool()->RunsTasksOnCurrentThread());
+
+  // Read the file from disk.
+  std::string file_contents;
+  FilePath path = image_info.resource.GetFilePath();
+  if (path.empty() || !file_util::ReadFileToString(path, &file_contents)) {
+    return;
+  }
+
+  // Decode the bitmap using WebKit's image decoder.
+  const unsigned char* data =
+      reinterpret_cast<const unsigned char*>(file_contents.data());
+  webkit_glue::ImageDecoder decoder;
+  // Note: This class only decodes bitmaps from extension resources. Chrome
+  // doesn't (for security reasons) directly load extension resources provided
+  // by the extension author, but instead decodes them in a separate
+  // locked-down utility process. Only if the decoding succeeds is the image
+  // saved from memory to disk and subsequently used in the Chrome UI.
+  // Chrome is therefore decoding bitmaps here that were generated by Chrome.
+  *bitmap = decoder.Decode(data, file_contents.length());
+}
+
+void LoadImagesOnBlockingPool(
+    const std::vector<ImageRepresentation>& info_list,
+    const std::vector<SkBitmap*>& bitmaps,
+    const base::Callback<void(const gfx::Image&)>& callback,
+    BrowserThread::ID thread_id) {
+  DCHECK(BrowserThread::GetBlockingPool()->RunsTasksOnCurrentThread());
+
+  gfx::ImageSkia image_skia;
+
+  int i = 0;
+  for (std::vector<ImageRepresentation>::const_iterator it = info_list.begin();
+       it != info_list.end(); ++it, ++i) {
+    // If we don't have a path there isn't anything we can do, just skip it.
+    if (it->resource.relative_path().empty())
+      continue;
+
+    SkBitmap bitmap;
+    if (bitmaps[i]) {
+      bitmap = *bitmaps[i];
+      delete bitmaps[i];
+    } else {
+      LoadImageOnBlockingPool(*it, &bitmap);
+    }
+
+    // If the image failed to load, skip it.
+    if (bitmap.isNull() || bitmap.empty())
+      continue;
+
+    bitmap = ResizeIfNeeded(bitmap, *it);
+
+    image_skia.AddRepresentation(gfx::ImageSkiaRep(bitmap, it->scale_factor));
+  }
+
+  gfx::Image image;
+
+  if (!image_skia.isNull()) {
+    image_skia.MakeThreadSafe();
+    image = gfx::Image(image_skia);
+  }
+
+  BrowserThread::PostTask(thread_id, FROM_HERE, base::Bind(callback, image));
+}
+
+}  // namespace
+
+namespace extension_image_utils {
+
+bool IsComponentExtensionResource(const Extension* extension,
+                                  const FilePath& resource_path,
+                                  int* resource_id) {
+  static const GritResourceMap kExtraComponentExtensionResources[] = {
+    {"web_store/webstore_icon_128.png", IDR_WEBSTORE_ICON},
+    {"web_store/webstore_icon_16.png", IDR_WEBSTORE_ICON_16},
+    {"chrome_app/product_logo_128.png", IDR_PRODUCT_LOGO_128},
+    {"chrome_app/product_logo_16.png", IDR_PRODUCT_LOGO_16},
+  };
+  static const size_t kExtraComponentExtensionResourcesSize =
+      arraysize(kExtraComponentExtensionResources);
+
+  if (extension->location() != Extension::COMPONENT)

[Aaron Boodman, 2012/10/08 19:00:31]

If the location is component, then we should never go to the disk to try and
find this icon. But some of the branches below return false, so we will.

[Marijn Kruisselbrink, 2012/10/08 20:24:52]

So should all the branches that return false have a NOTREACHED() to hopefully
check that this method is only called when a resource actually exists? Although
since this method can potentially be called with arbitrary chrome-extension://
urls that might be a bad idea. So this would either need some other output
("this is a component extension resource but I don't have a resource id") or
whatever place calls this method should do the location() check and deal with
the case of no resource id (even if IsComponentExtensionResource would do the
check, all the places that call it would still need to special case the
situation where it would return true but not return a valid resource id).

+    return false;
+
+  FilePath directory_path = extension->path();
+  FilePath resources_dir;
+  FilePath relative_path;
+  if (!PathService::Get(chrome::DIR_RESOURCES, &resources_dir) ||
+      !resources_dir.AppendRelativePath(directory_path, &relative_path)) {
+    return false;
+  }
+  relative_path = relative_path.Append(resource_path);
+  relative_path = relative_path.NormalizePathSeparators();
+
+  // TODO(tc): Make a map of FilePath -> resource ids so we don't have to
+  // covert to FilePaths all the time.  This will be more useful as we add
+  // more resources.
+  for (size_t i = 0; i < kComponentExtensionResourcesSize; ++i) {
+    FilePath resource_path =
+        FilePath().AppendASCII(kComponentExtensionResources[i].name);
+    resource_path = resource_path.NormalizePathSeparators();
+
+    if (relative_path == resource_path) {
+      *resource_id = kComponentExtensionResources[i].value;
+      return true;
+    }
+  }
+  for (size_t i = 0; i < kExtraComponentExtensionResourcesSize; ++i) {
+    FilePath resource_path =
+        FilePath().AppendASCII(kExtraComponentExtensionResources[i].name);
+    resource_path = resource_path.NormalizePathSeparators();
+
+    if (relative_path == resource_path) {
+      *resource_id = kExtraComponentExtensionResources[i].value;
+      return true;
+    }
+  }
+  return false;
+}
+
+ImageRepresentation::ImageRepresentation(
+    const ExtensionResource& resource,
+    ResizeCondition resize_condition,
+    const gfx::Size& desired_size,
+    ui::ScaleFactor scale_factor)
+    : resource(resource),
+      resize_condition(resize_condition),
+      desired_size(desired_size),
+      scale_factor(scale_factor) {
+}
+
+ImageRepresentation::~ImageRepresentation() {
+}
+
+void LoadImageAsync(const Extension* extension,
+                    const ExtensionResource& resource,
+                    const gfx::Size& max_size,
+                    const base::Callback<void(const gfx::Image&)>& callback) {
+  std::vector<ImageRepresentation> info_list;
+  info_list.push_back(ImageRepresentation(
+      resource,
+      ImageRepresentation::RESIZE_WHEN_LARGER,
+      max_size,
+      ui::SCALE_FACTOR_100P));
+  LoadImagesAsync(extension, info_list, callback);
+}
+
+void LoadImagesAsync(const Extension* extension,
+                     const std::vector<ImageRepresentation>& info_list,
+                     const base::Callback<void(const gfx::Image&)>& callback) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+
+  // Loading an image from the cache and loading resources have to happen
+  // on the UI thread. So do those two things first, and pass the rest of the
+  // work of as a blocking pool task.
+  std::vector<SkBitmap*> bitmaps;
+  bitmaps.resize(info_list.size());
+  int i = 0;
+  for (std::vector<ImageRepresentation>::const_iterator it = info_list.begin();
+       it != info_list.end(); ++it, ++i) {
+    DCHECK(it->resource.relative_path().empty() ||
+           extension->path() == it->resource.extension_root());
+
+    if (extension->HasCachedImage(it->resource, it->desired_size)) {
+      bitmaps[i] = new SkBitmap(extension->GetCachedImage(it->resource,
+                                                          it->desired_size));
+      continue;
+    }
+
+    int resource_id;
+    if (IsComponentExtensionResource(extension, it->resource.relative_path(),
+                                     &resource_id)) {
+      bitmaps[i] = new SkBitmap;
+      LoadResourceOnUIThread(resource_id, bitmaps[i]);
+    }
+  }

[Aaron Boodman, 2012/10/08 19:00:31]

If we're done at this point, it would be nice to call the callback. You should
document that it could be re-entrant though.

[Marijn Kruisselbrink, 2012/10/08 20:24:52]

Done. I wasn't sure if it made sense to complicate code for this particular
case/if it made sense to expose this sort of detail to users of LoadImage, but I
can see how it is desirable to not have to wait for the message loop to get the
image if it is available immediately anyway.

+
+  BrowserThread::ID thread_id;
+  CHECK(BrowserThread::GetCurrentThreadIdentifier(&thread_id));
+  DCHECK(!BrowserThread::GetBlockingPool()->RunsTasksOnCurrentThread());
+  BrowserThread::PostBlockingPoolTask(
+      FROM_HERE,
+      base::Bind(&LoadImagesOnBlockingPool, info_list,
+                 bitmaps, callback, thread_id));
+}
+
+}  // namespace extension_image_utils