icon_manager.h | Explore in Territory

// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
//
// Class for finding and caching Windows explorer icons. The IconManager
// lives on the UI thread but performs icon extraction work on the file thread
// to avoid blocking the UI thread with potentially expensive COM and disk
// operations.
//
// Terminology
//
// Windows files have icons associated with them that can be of two types:
//   1. "Per class": the icon used for this file is used for all files with the
//      same file extension or class. Examples are PDF or MP3 files, which use
//      the same icon for all files of that type.
//   2. "Per instance": the icon used for this file is embedded in the file
//      itself and is unique. Executable files are typically "per instance".
//
// Files that end in the following extensions are considered "per instance":
//   .exe
//   .dll
//   .ico
// The IconManager will do explicit icon loads on the full path of these files
// and cache the results per file. All other file types will be looked up by
// file extension and the results will be cached per extension. That way, all
// .mp3 files will share one icon, but all .exe files will have their own icon.
//
// POSIX files don't have associated icons. We query the OS by the file's
// mime type.
//
// The IconManager can be queried in two ways:
//   1. A quick, synchronous check of its caches which does not touch the disk:
//      IconManager::LookupIcon()
//   2. An asynchronous icon load from a file on the file thread:
//      IconManager::LoadIcon()
//
// When using the second (asynchronous) method, callers must supply a callback
// which will be run once the icon has been extracted. The icon manager will
// cache the results of the icon extraction so that subsequent lookups will be
// fast.
//
// Icon bitmaps returned should be treated as const since they may be referenced
// by other clients. Make a copy of the icon if you need to modify it.

#ifndef CHROME_BROWSER_ICON_MANAGER_H_
#define CHROME_BROWSER_ICON_MANAGER_H_

#include <map>
#include <memory>

#include "base/files/file_path.h"
#include "base/memory/weak_ptr.h"
#include "base/task/cancelable_task_tracker.h"
#include "chrome/browser/icon_loader.h"
#include "ui/gfx/image/image.h"

class IconManager { … };

#endif  // CHROME_BROWSER_ICON_MANAGER_H_
chromium/chrome/browser/icon_manager.h
