extensions/browser/extension_icon_image.h

// Copyright 2014 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 EXTENSIONS_BROWSER_EXTENSION_ICON_IMAGE_H_
#define EXTENSIONS_BROWSER_EXTENSION_ICON_IMAGE_H_

#include <map>
#include <string>

#include "base/macros.h"
#include "base/memory/weak_ptr.h"
#include "base/observer_list.h"
#include "content/public/browser/notification_observer.h"
#include "content/public/browser/notification_registrar.h"
#include "extensions/common/extension_icon_set.h"
#include "ui/gfx/image/image.h"
#include "ui/gfx/image/image_skia.h"

namespace content {
class BrowserContext;
}

namespace extensions {
class Extension;
}

namespace gfx {
class Image;
}

namespace extensions {

// A class that provides an ImageSkia for UI code to use. It handles extension
// icon resource loading, screen scale factor change etc. UI code that uses
// extension icon should host this class. In painting code, UI code paints with
// the ImageSkia provided by this class. If the required extension icon resource
// is not already present, this class tries to load it and calls its observer
// interface when the image get updated. Until the resource is loaded, the UI
// code will be provided with a blank, transparent image.
// If the requested resource doesn't exist or can't be loaded and a default
// icon was supplied in the constructor, icon image will be updated with the
// default icon's resource.
// The default icon doesn't need to be supplied, but in that case, icon image
// representation will be left blank if the resource loading fails.
// If default icon is supplied, it is assumed that it contains or can
// synchronously create (when |GetRepresentation| is called on it)
// representations for all the scale factors supported by the current platform.
// Note that |IconImage| is not thread safe.
class IconImage : public content::NotificationObserver {
 public:
  class Observer {
   public:
    // Invoked when a new image rep for an additional scale factor
    // is loaded and added to |image|.
    virtual void OnExtensionIconImageChanged(IconImage* image) = 0;

    // Called when this object is deleted. Objects should observe this if there
    // is a question about the lifetime of the icon image vs observer.
    virtual void OnExtensionIconImageDestroyed(IconImage* image) {}

   protected:
    virtual ~Observer() {}
  };

  // |context| is required by the underlying implementation to retrieve the
  // |ImageLoader| instance associated with the given context. |ImageLoader| is
  // used to perform the asynchronous image load work.
  // Set |keep_original_size| to true to load the icon at the original size
  // without resizing. In this case |resource_size_in_dip| will still be used to
  // pick the correct icon representation. This is useful if the client code
  // performs its own resizing.
  IconImage(content::BrowserContext* context,
            const Extension* extension,
            const ExtensionIconSet& icon_set,
            int resource_size_in_dip,
            bool keep_original_size,
            const gfx::ImageSkia& default_icon,
            Observer* observer);
  IconImage(content::BrowserContext* context,
            const Extension* extension,
            const ExtensionIconSet& icon_set,
            int resource_size_in_dip,
            const gfx::ImageSkia& default_icon,
            Observer* observer);
  ~IconImage() override;

  gfx::Image image() const { return image_; }
  const gfx::ImageSkia& image_skia() const { return image_skia_; }

  // Returns true if the icon is attached to an existing extension.
  bool is_valid() const { return extension_ ? true : false; }

  void AddObserver(Observer* observer);
  void RemoveObserver(Observer* observer);

 private:
  class Source;

  // Loads an image representation for the scale factor asynchronously. Result
  // is passed to OnImageRepLoaded.
  void LoadImageForScaleAsync(float scale);

  void OnImageLoaded(float scale, const gfx::Image& image);
  void OnImageRepLoaded(const gfx::ImageSkiaRep& rep);

  // content::NotificationObserver overrides:
  void Observe(int type,
               const content::NotificationSource& source,
               const content::NotificationDetails& details) override;

  content::BrowserContext* browser_context_;
  scoped_refptr<const Extension> extension_;
  ExtensionIconSet icon_set_;
  const int resource_size_in_dip_;
  // Whether the loaded icon should be kept at the original size.
  const bool keep_original_size_;

  base::ObserverList<Observer>::Unchecked observers_;

  Source* source_;  // Owned by ImageSkia storage.
  gfx::ImageSkia image_skia_;
  // The icon with whose representation |image_skia_| should be updated if
  // its own representation load fails.
  gfx::ImageSkia default_icon_;

  // The image wrapper around |image_skia_|.
  // Note: this is reset each time a new representation is loaded.
  gfx::Image image_;

  content::NotificationRegistrar registrar_;

  base::WeakPtrFactory<IconImage> weak_ptr_factory_;

  DISALLOW_COPY_AND_ASSIGN(IconImage);
};

}  // namespace extensions

#endif  // EXTENSIONS_BROWSER_EXTENSION_ICON_IMAGE_H_