chrome/browser/icon_loader.h

// Copyright (c) 2006-2008 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.

#ifndef CHROME_BROWSER_ICON_LOADER_H_
#define CHROME_BROWSER_ICON_LOADER_H_

#include <string>

#include "base/basictypes.h"
#include "base/file_path.h"

namespace {
class IconLoaderProcessor;
}

class SkBitmap;

////////////////////////////////////////////////////////////////////////////////
//
// A facility to read a file containing an icon asynchronously in the IO
// thread. Clients has the option to get the icon in the form of two HICON
// handles (one for a small icon size and one for a large icon) or in the form
// of an SkBitmap.
//
// This class currently only supports reading .ico files. Please extend as
// needed.
//
////////////////////////////////////////////////////////////////////////////////
class IconLoader {
 public:
  enum IconSize {
    SMALL = 0,  // 16x16
    NORMAL,     // 32x32
    LARGE
  };

  class Delegate {
   public:
    // Invoked when an icon has been read. |source| is the IconLoader. If the
    // icon has been successfully loaded, result is non-null. This method must
    // return true if it is taking ownership of the returned bitmap.
    virtual bool OnSkBitmapLoaded(IconLoader* source, SkBitmap* result) = 0;
  };

  // Create a new IconLoader that loads the icon from the data at contained in
  // the file at |path|.
  static IconLoader* CreateIconLoaderForFile(const FilePath& path,
                                             Delegate* delegate);

  // Create a new IconLoader that loads the icon in the resource of the file
  // at |path|.  This is used with .exe/.dll files.
  // Note that this generates a SkBitmap (and consequently OnSkBitmapLoaded is
  // invoked on the delegate once the load has completed).
  static IconLoader* CreateIconLoaderForFileResource(const FilePath& path,
                                                     IconSize size,
                                                     Delegate* delegate);

  ~IconLoader();

  // Start the read operation
  void Start();

  // Cancel the read operation. The delegate will no longer be contacted. Call
  // this method if you need to delete the delegate.
  void Cancel();

 private:
  friend class IconLoaderProcessor;

  // Use the factory methods CreateIconLoader* instead of using this constructor
  IconLoader(const FilePath& path,
             bool from_resource,
             IconSize size,
             Delegate* delegate);

  // Invoked by the processor when the file has been read and an SkBitmap
  // object was requested.
  bool OnLoadComplete(SkBitmap* result);

  // The path.
  FilePath path_;

  // The delegate.
  Delegate* delegate_;

  // Whether we are loading the icon from the resource in the file (if false,
  // the icon is simply loaded from the file content).
  bool loading_from_resource_;

  // The size of the icon that should be loaded from the file resource.
  // Not used if loading_from_resource_ is false.
  IconSize icon_size_;

  // The underlying object performing the read.
  IconLoaderProcessor* processor_;

  DISALLOW_COPY_AND_ASSIGN(IconLoader);
};

#endif  // CHROME_BROWSER_ICON_LOADER_H_