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// Copyright (c) 2012 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.
// 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.
#include <map>
#include <memory>
#include "base/files/file_path.h"
#include "base/macros.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 {
// Synchronous call to examine the internal caches for the icon. Returns the
// icon if we have already loaded it, or null if we don't have it and must
// load it via LoadIcon(). The returned bitmap is owned by the IconManager and
// must not be free'd by the caller. If the caller needs to modify the icon,
// it must make a copy and modify the copy.
gfx::Image* LookupIconFromFilepath(const base::FilePath& file_path,
IconLoader::IconSize size);
using IconRequestCallback = base::Callback<void(gfx::Image*)>;
// Asynchronous call to lookup and return the icon associated with file. The
// work is done on the file thread, with the callbacks running on the thread
// this function is called.
// Note:
// 1. This does *not* check the cache.
// 2. The returned bitmap pointer is *not* owned by callback. So callback
// should never keep it or delete it.
// 3. The gfx::Image pointer passed to the callback will be null if decoding
// failed.
base::CancelableTaskTracker::TaskId LoadIcon(
const base::FilePath& file_name,
IconLoader::IconSize size,
const IconRequestCallback& callback,
base::CancelableTaskTracker* tracker);
void OnIconLoaded(IconRequestCallback callback,
base::FilePath file_path,
IconLoader::IconSize size,
std::unique_ptr<gfx::Image> result,
const IconLoader::IconGroup& group);
struct CacheKey {
CacheKey(const IconLoader::IconGroup& group, IconLoader::IconSize size);
// Used as a key in the map below, so we need this comparator.
bool operator<(const CacheKey &other) const;
IconLoader::IconGroup group;
IconLoader::IconSize size;
std::map<base::FilePath, IconLoader::IconGroup> group_cache_;
std::map<CacheKey, std::unique_ptr<gfx::Image>> icon_cache_;
base::WeakPtrFactory<IconManager> weak_factory_;