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// Copyright (c) 2011 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_EXTENSIONS_IMAGE_LOADING_TRACKER_H_
#define CHROME_BROWSER_EXTENSIONS_IMAGE_LOADING_TRACKER_H_
#pragma once
#include <map>
#include "base/ref_counted.h"
#include "content/common/notification_observer.h"
#include "content/common/notification_registrar.h"
class Extension;
class ExtensionResource;
class SkBitmap;
namespace gfx {
class Size;
}
// The views need to load their icons asynchronously but might be deleted before
// the images have loaded. This class encapsulates a loader class that stays
// alive while the request is in progress (manages its own lifetime) and keeps
// track of whether the view still cares about the icon loading.
//
// To use this class, have your class derive from ImageLoadingTracker::Observer,
// and add a member variable ImageLoadingTracker tracker_. Then override
// Observer::OnImageLoaded and call:
// tracker_.LoadImage(extension, resource, max_size, false);
// ... and wait for OnImageLoaded to be called back on you with a pointer to the
// SkBitmap loaded.
// NOTE: if the image is available already (or the resource is not valid), the
// Observer is notified immediately from the call to LoadImage. In other words,
// by the time LoadImage returns the observer has been notified.
//
class ImageLoadingTracker : public NotificationObserver {
public:
enum CacheParam {
CACHE,
DONT_CACHE
};
class Observer {
public:
virtual ~Observer();
// Will be called when the image with the given index has loaded.
// The |image| is owned by the tracker, so the observer should make a copy
// if they need to access it after this call. |image| can be null if valid
// image was not found or it failed to decode. |resource| is the
// ExtensionResource where the |image| came from and the |index| represents
// the index of the image just loaded (starts at 0 and increments every
// time LoadImage is called).
virtual void OnImageLoaded(SkBitmap* image,
const ExtensionResource& resource,
int index) = 0;
};
explicit ImageLoadingTracker(Observer* observer);
~ImageLoadingTracker();
// Specify image resource to load. If the loaded image is larger than
// |max_size| it will be resized to those dimensions. IMPORTANT NOTE: this
// function may call back your observer synchronously (ie before it returns)
// if the image was found in the cache.
void LoadImage(const Extension* extension,
const ExtensionResource& resource,
const gfx::Size& max_size,
CacheParam cache);
private:
typedef std::map<int, const Extension*> LoadMap;
class ImageLoader;
// When an image has finished loaded and been resized on the file thread, it
// is posted back to this method on the original thread. This method then
// calls the observer's OnImageLoaded and deletes the ImageLoadingTracker if
// it was the last image in the list. The |original_size| should be the size
// of the image before any resizing was done.
// |image| may be null if the file failed to decode.
void OnImageLoaded(SkBitmap* image, const ExtensionResource& resource,
const gfx::Size& original_size, int id);
// NotificationObserver method. If an extension is uninstalled while we're
// waiting for the image we remove the entry from load_map_.
virtual void Observe(NotificationType type,
const NotificationSource& source,
const NotificationDetails& details);
// The view that is waiting for the image to load.
Observer* observer_;
// ID to use for next image requested. This is an ever increasing integer.
int next_id_;
// The object responsible for loading the image on the File thread.
scoped_refptr<ImageLoader> loader_;
// If LoadImage is told to cache the result an entry is added here. The
// integer identifies the id assigned to the request. If the extension is
// deleted while fetching the image the entry is removed from the map.
LoadMap load_map_;
NotificationRegistrar registrar_;
DISALLOW_COPY_AND_ASSIGN(ImageLoadingTracker);
};
#endif // CHROME_BROWSER_EXTENSIONS_IMAGE_LOADING_TRACKER_H_
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