chrome/browser/icon_manager.h

   1 // Copyright (c) 2012 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
  48 #include <map>
  49
  50 #include "base/files/file_path.h"
  51 #include "base/task/cancelable_task_tracker.h"
  52 #include "chrome/browser/icon_loader.h"
  53 #include "ui/gfx/image/image.h"
  54
  55 class IconManager : public IconLoader::Delegate {
  56  public:
  57   IconManager();
  58   ~IconManager() override;
  59
  60   // Synchronous call to examine the internal caches for the icon. Returns the
  61   // icon if we have already loaded it, NULL if we don't have it and must load
  62   // it via 'LoadIcon'. The returned bitmap is owned by the IconManager and must
  63   // not be free'd by the caller. If the caller needs to modify the icon, it
  64   // must make a copy and modify the copy.
  65   gfx::Image* LookupIconFromFilepath(const base::FilePath& file_name,
  66                                      IconLoader::IconSize size);
  67
  68   typedef base::Callback<void(gfx::Image*)> IconRequestCallback;
  69
  70   // Asynchronous call to lookup and return the icon associated with file. The
  71   // work is done on the file thread, with the callbacks running on the thread
  72   // this function is called.
  73   //
  74   // Note:
  75   // 1. This does *not* check the cache.
  76   // 2. The returned bitmap pointer is *not* owned by callback. So callback
  77   //    should never keep it or delete it.
  78   // 3. The gfx::Image pointer passed to the callback may be NULL if decoding
  79   //    failed.
  80   base::CancelableTaskTracker::TaskId LoadIcon(
  81       const base::FilePath& file_name,
  82       IconLoader::IconSize size,
  83       const IconRequestCallback& callback,
  84       base::CancelableTaskTracker* tracker);
  85
  86   // IconLoader::Delegate interface.
  87   bool OnGroupLoaded(IconLoader* loader, const IconGroupID& group) override;
  88   bool OnImageLoaded(IconLoader* loader,
  89                      gfx::Image* result,
  90                      const IconGroupID& group) override;
  91
  92  private:
  93   struct CacheKey {
  94     CacheKey(const IconGroupID& group, IconLoader::IconSize size);
  95
  96     // Used as a key in the map below, so we need this comparator.
  97     bool operator<(const CacheKey &other) const;
  98
  99     IconGroupID group;
 100     IconLoader::IconSize size;
 101   };
 102
 103   gfx::Image* LookupIconFromGroup(const IconGroupID& group,
 104                                   IconLoader::IconSize size);
 105
 106   typedef std::map<CacheKey, gfx::Image*> IconMap;
 107   IconMap icon_cache_;
 108
 109   typedef std::map<base::FilePath, IconGroupID> GroupMap;
 110   GroupMap group_cache_;
 111
 112   // Asynchronous requests that have not yet been completed.
 113   struct ClientRequest;
 114   typedef std::map<IconLoader*, ClientRequest> ClientRequests;
 115   ClientRequests requests_;
 116
 117   DISALLOW_COPY_AND_ASSIGN(IconManager);
 118 };
 119
 120 #endif  // CHROME_BROWSER_ICON_MANAGER_H_