97 lines
3.4 KiB
C++
97 lines
3.4 KiB
C++
// Copyright (c) 2012 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef CHROME_BROWSER_ICON_LOADER_H_
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#define CHROME_BROWSER_ICON_LOADER_H_
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#include <memory>
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#include <string>
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#include "base/callback.h"
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#include "base/files/file_path.h"
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#include "base/macros.h"
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#include "base/single_thread_task_runner.h"
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#include "base/task_scheduler/task_traits.h"
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#include "build/build_config.h"
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#include "content/public/browser/browser_thread.h"
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#include "ui/gfx/image/image.h"
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////////////////////////////////////////////////////////////////////////////////
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//
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// A facility to read a file containing an icon asynchronously in the IO
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// thread. Returns the icon in the form of an ImageSkia.
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//
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////////////////////////////////////////////////////////////////////////////////
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class IconLoader {
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public:
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// An IconGroup is a class of files that all share the same icon. For all
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// platforms but Windows, and for most files on Windows, it is the file type
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// (e.g. all .mp3 files share an icon, all .html files share an icon). On
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// Windows, for certain file types (.exe, .dll, etc), each file of that type
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// is assumed to have a unique icon. In that case, each of those files is a
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// group to itself.
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using IconGroup = base::FilePath::StringType;
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enum IconSize {
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SMALL = 0, // 16x16
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NORMAL, // 32x32
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LARGE, // Windows: 32x32, Linux: 48x48, Mac: Unsupported
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ALL, // All sizes available
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};
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// The callback invoked when an icon has been read. The parameters are:
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// - The icon that was loaded, or null if there was a failure to load it.
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// - The determined group from the original requested path.
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using IconLoadedCallback =
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base::Callback<void(std::unique_ptr<gfx::Image>, const IconGroup&)>;
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// Creates an IconLoader, which owns itself. If the IconLoader might outlive
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// the caller, be sure to use a weak pointer in the |callback|.
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static IconLoader* Create(const base::FilePath& file_path,
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IconSize size,
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IconLoadedCallback callback);
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// Starts the process of reading the icon. When the reading of the icon is
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// complete, the IconLoadedCallback callback will be fulfilled, and the
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// IconLoader will delete itself.
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void Start();
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private:
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IconLoader(const base::FilePath& file_path,
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IconSize size,
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IconLoadedCallback callback);
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~IconLoader();
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// Given a file path, get the group for the given file.
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static IconGroup GroupForFilepath(const base::FilePath& file_path);
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// The TaskRunner that ReadIcon() must be called on.
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static scoped_refptr<base::TaskRunner> GetReadIconTaskRunner();
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void ReadGroup();
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void ReadIcon();
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// The traits of the tasks posted by this class. These operations may block,
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// because they are fetching icons from the disk, yet the result will be seen
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// by the user so they should be prioritized accordingly.
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static constexpr base::TaskTraits traits() {
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return {base::MayBlock(), base::TaskPriority::USER_VISIBLE};
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}
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// The task runner object of the thread in which we notify the delegate.
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scoped_refptr<base::SingleThreadTaskRunner> target_task_runner_;
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base::FilePath file_path_;
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IconGroup group_;
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IconSize icon_size_;
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IconLoadedCallback callback_;
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DISALLOW_COPY_AND_ASSIGN(IconLoader);
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};
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#endif // CHROME_BROWSER_ICON_LOADER_H_
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