1// Copyright (c) 2011 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// Class for finding and caching Windows explorer icons. The IconManager
6// lives on the UI thread but performs icon extraction work on the file thread
7// to avoid blocking the UI thread with potentially expensive COM and disk
8// operations.
9//
10// Terminology
11//
12// Windows files have icons associated with them that can be of two types:
13//   1. "Per class": the icon used for this file is used for all files with the
14//      same file extension or class. Examples are PDF or MP3 files, which use
15//      the same icon for all files of that type.
16//   2. "Per instance": the icon used for this file is embedded in the file
17//      itself and is unique. Executable files are typically "per instance".
18//
19// Files that end in the following extensions are considered "per instance":
20//   .exe
21//   .dll
22//   .ico
23// The IconManager will do explicit icon loads on the full path of these files
24// and cache the results per file. All other file types will be looked up by
25// file extension and the results will be cached per extension. That way, all
26// .mp3 files will share one icon, but all .exe files will have their own icon.
27//
28// POSIX files don't have associated icons. We query the OS by the file's
29// mime type.
30//
31// The IconManager can be queried in two ways:
32//   1. A quick, synchronous check of its caches which does not touch the disk:
33//      IconManager::LookupIcon()
34//   2. An asynchronous icon load from a file on the file thread:
35//      IconManager::LoadIcon()
36//
37// When using the second (asychronous) method, callers must supply a callback
38// which will be run once the icon has been extracted. The icon manager will
39// cache the results of the icon extraction so that subsequent lookups will be
40// fast.
41//
42// Icon bitmaps returned should be treated as const since they may be referenced
43// by other clients. Make a copy of the icon if you need to modify it.
44
45#ifndef CHROME_BROWSER_ICON_MANAGER_H_
46#define CHROME_BROWSER_ICON_MANAGER_H_
47#pragma once
48
49#include <map>
50
51#include "base/callback.h"
52#include "base/hash_tables.h"
53#include "chrome/browser/icon_loader.h"
54#include "content/browser/cancelable_request.h"
55#include "ui/gfx/image.h"
56
57class FilePath;
58
59class IconManager : public IconLoader::Delegate,
60                    public CancelableRequestProvider {
61 public:
62  IconManager();
63  ~IconManager();
64
65  // Synchronous call to examine the internal caches for the icon. Returns the
66  // icon if we have already loaded it, NULL if we don't have it and must load
67  // it via 'LoadIcon'. The returned bitmap is owned by the IconManager and must
68  // not be free'd by the caller. If the caller needs to modify the icon, it
69  // must make a copy and modify the copy.
70  gfx::Image* LookupIcon(const FilePath& file_name,
71                         IconLoader::IconSize size);
72
73  typedef CancelableRequestProvider::Handle Handle;
74  typedef Callback2<Handle, gfx::Image*>::Type IconRequestCallback;
75
76  // Asynchronous call to lookup and return the icon associated with file. The
77  // work is done on the file thread, with the callbacks running on the UI
78  // thread. The return value is the 'request_id' that will be passed to the
79  // client in the callback. Note: this does *not* check the cache.
80  //
81  // WATCH OUT: The returned bitmap pointer may be NULL if decoding failed.
82  Handle LoadIcon(const FilePath& file_name,
83                  IconLoader::IconSize size,
84                  CancelableRequestConsumerBase* consumer,
85                  IconRequestCallback* callback);
86
87  // IconLoader::Delegate interface.
88  virtual bool OnImageLoaded(IconLoader* source, gfx::Image* result);
89
90  // Get the identifying string for the given file. The implementation
91  // is in icon_manager_[platform].cc.
92  static IconGroupID GetGroupIDFromFilepath(const FilePath& path);
93
94 private:
95  struct CacheKey {
96    CacheKey(const IconGroupID& group, IconLoader::IconSize size);
97
98    // Used as a key in the map below, so we need this comparator.
99    bool operator<(const CacheKey &other) const;
100
101    IconGroupID group;
102    IconLoader::IconSize size;
103  };
104
105  typedef std::map<CacheKey, gfx::Image*> IconMap;
106  IconMap icon_cache_;
107
108  typedef CancelableRequest<IconRequestCallback> IconRequest;
109
110  // Asynchronous requests that have not yet been completed.
111  struct ClientRequest;
112  typedef std::map<IconLoader*, ClientRequest> ClientRequests;
113  ClientRequests requests_;
114
115  DISALLOW_COPY_AND_ASSIGN(IconManager);
116};
117
118#endif  // CHROME_BROWSER_ICON_MANAGER_H_
119