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1 // Copyright (c) 2009 The Chromium Authors. All rights reserved. | |
2 // Use of this source code is governed by a BSD-style license that can be | |
3 // found in the LICENSE file. | |
4 | |
5 #ifndef CHROME_BROWSER_IMAGE_LOADING_TRACKER_H_ | |
6 #define CHROME_BROWSER_IMAGE_LOADING_TRACKER_H_ | |
7 | |
8 #include "base/ref_counted.h" | |
9 | |
10 class FilePath; | |
11 class SkBitmap; | |
12 | |
13 // The views need to load their icons asynchronously but might be deleted before | |
14 // the images have loaded. This class stays alive while the request is in | |
15 // progress (manages its own lifetime) and keeps track of whether the view still | |
16 // cares about the icon loading. | |
17 class ImageLoadingTracker | |
18 : public base::RefCountedThreadSafe<ImageLoadingTracker> { | |
19 public: | |
20 class Observer { | |
21 public: | |
22 // Will be called when the image with the given index has loaded. | |
23 // The |image| is owned by the tracker, so the observer should make a copy | |
24 // if they need to access it after this call. | |
25 virtual void OnImageLoaded(SkBitmap* image, size_t index) = 0; | |
26 }; | |
27 | |
28 ImageLoadingTracker(Observer* observer, size_t image_count) | |
29 : observer_(observer), image_count_(image_count), posted_count_(0) { | |
30 AddRef(); // We hold on to a reference to ourself to make sure we don't | |
31 // get deleted until we get a response from image loading (see | |
32 // ImageLoadingDone). | |
33 } | |
34 ~ImageLoadingTracker() {} | |
35 | |
36 // If there are remaining images to be loaded, the observing object should | |
37 // call this method on its destruction, so that the tracker will not attempt | |
38 // to make any more callbacks to it. | |
39 void StopTrackingImageLoad() { | |
40 observer_ = NULL; | |
41 } | |
42 | |
43 // Specify path of image to load. This method must be called a number of | |
44 // times equal to the |image_count| arugment to the constructor. Calling it | |
45 // any more or less than that is an error. | |
46 void PostLoadImageTask(FilePath path); | |
47 | |
48 private: | |
49 class LoadImageTask; | |
50 | |
51 // When an image has finished loaded and scaled on the file thread, it is | |
52 // posted back to this method on the original thread. This method then calls | |
53 // the observer's OnImageLoaded and deletes the ImageLoadingTracker if it was | |
54 // the last image in the list. | |
55 // |image| may be null if the file failed to decode. | |
56 void OnImageLoaded(SkBitmap* image, size_t index); | |
57 | |
58 // The view that is waiting for the image to load. | |
59 Observer* observer_; | |
60 | |
61 // The number of images this ImageTracker should keep track of. This is | |
62 // decremented as each image finishes loading, and the tracker will delete | |
63 // itself when it reaches zero. | |
64 size_t image_count_; | |
65 | |
66 // The number of tasks that have been posted so far. | |
67 size_t posted_count_; | |
68 | |
69 DISALLOW_COPY_AND_ASSIGN(ImageLoadingTracker); | |
70 }; | |
71 | |
72 #endif // CHROME_BROWSER_IMAGE_LOADING_TRACKER_H_ | |
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