arc-app-launcher: Minimal support for ARC app launcher.

chrome/browser/ui/app_list/arc/arc_app_icon.h

+// Copyright 2015 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.
+
+#ifndef CHROME_BROWSER_UI_APP_LIST_ARC_ARC_APP_ICON_H_
+#define CHROME_BROWSER_UI_APP_LIST_ARC_ARC_APP_ICON_H_
+
+#include <string>
+
+#include "base/macros.h"
+#include "base/memory/scoped_vector.h"
+#include "base/memory/weak_ptr.h"
+#include "ui/base/layout.h"
+#include "ui/gfx/image/image.h"
+#include "ui/gfx/image/image_skia.h"
+
+namespace base {
+class FilePath;
+}
+
+namespace content {
+class BrowserContext;
+}
+
+// A class that provides an ImageSkia for UI code to use. It handles ARC app
+// icon resource loading, screen scale factor change etc. UI code that uses
+// ARC app icon should host this class.
+class ArcAppIcon {
+ public:
+  class Observer {
+   public:
+    // Invoked when a new image rep for an additional scale factor
+    // is loaded and added to |image|.
+    virtual void OnIconUpdated() = 0;
+
+   protected:
+    virtual ~Observer() {}
+  };
+
+  ArcAppIcon(content::BrowserContext* context,
+             const std::string& app_id,
+             int resource_size_in_dip,
+             Observer* observer);
+  ~ArcAppIcon();
+
+  gfx::Image image() const { return image_; }
+  const gfx::ImageSkia& image_skia() const { return image_skia_; }
+
+  // Icon loading is performed in several steps. It is initiated by
+  // LoadImageForScaleFactor request that specifies a required scale factor.
+  // ArcAppListPrefs is used to resolve a path to resource. Content of file is
+  // asynchronously read in context of browser file thread. On successful read,
+  // an icon data is decoded to an image in the special utility process.
+  // DecodeRequest is used to interact with the utility process, and each
+  // active request is stored at |decode_requests_| vector. When decoding is
+  // complete, results are returned in context of UI thread, and corresponding
+  // request is removed from |decode_requests_|. In case of some requests are
+  // not completed by the time of deleting this icon, they are automatically
+  // canceled.
+  // In case of the icon file is not available this requests ArcAppListPrefs to
+  // install required resource from ARC side. ArcAppListPrefs notifies UI items
+  // that new icon is available and corresponding item should invoke
+  // LoadImageForScaleFactor again.
+  void LoadForScaleFactor(ui::ScaleFactor scale_factor);
+
+  // Disables decoding requests when unit tests are executed. This is done to
+  // avoid two problems. Problems come because icons are decoded at a separate
+  // process created by ImageDecoder. ImageDecoder has 5 seconds delay to stop
+  // since the last request (see its kBatchModeTimeoutSeconds for more details).
+  // This is unacceptably long for unit tests because the test framework waits
+  // until external process is finished. Another problem happens when we issue
+  // a decoding request, but the process has not started its processing yet by
+  // the time when a test exits. This might cause situation when
+  // g_one_utility_thread_lock from in_process_utility_thread.cc gets released
+  // in an acquired state which is crash condition in debug builds.
+  static void DisableDecodingForTesting();
+
+ private:
+  class Source;
+  class DecodeRequest;
+  struct ReadResult;
+
+  void RequestIcon(ui::ScaleFactor scale_factor);
+  static scoped_ptr<ArcAppIcon::ReadResult> ReadOnFileThread(
+      ui::ScaleFactor scale_factor,
+      const base::FilePath& path);
+  void OnIconRead(scoped_ptr<ArcAppIcon::ReadResult> read_result);
+  void Update(const gfx::ImageSkia* image);
+  void DiscardDecodeRequest(DecodeRequest* request);
+
+  content::BrowserContext* context_;
+  std::string app_id_;
+  const int resource_size_in_dip_;
+  Observer* observer_;
+
+  Source* source_ = nullptr;  // Owned by ImageSkia storage.
+  gfx::ImageSkia image_skia_;
+
+  // The image wrapper around |image_skia_|.
+  // Note: this is reset each time a new representation is loaded.
+  gfx::Image image_;
+
+  // Contains pending image decode requests.
+  ScopedVector<DecodeRequest> decode_requests_;
+
+  base::WeakPtrFactory<ArcAppIcon> weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(ArcAppIcon);
+};
+
+#endif  // CHROME_BROWSER_UI_APP_LIST_ARC_ARC_APP_ICON_H_