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// Copyright (c) 2010 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_COMMAND_UPDATER_H_
#define CHROME_BROWSER_COMMAND_UPDATER_H_
#pragma once
#include "base/basictypes.h"
#include "base/hash_tables.h"
////////////////////////////////////////////////////////////////////////////////
//
// CommandUpdater class
//
// This object manages the enabled state of a set of commands. Observers
// register to listen to changes in this state so they can update their
// presentation.
//
class CommandUpdater {
public:
// A Delegate object implements this interface so that it can execute commands
// when needed.
class CommandUpdaterDelegate {
public:
// Perform the action associated with the command with the specified ID.
virtual void ExecuteCommand(int id) = 0;
protected:
virtual ~CommandUpdaterDelegate();
};
// Create a CommandUpdater with a CommandUpdaterDelegate to handle execution
// of specific commands.
explicit CommandUpdater(CommandUpdaterDelegate* handler);
virtual ~CommandUpdater();
// Returns true if the specified command ID is supported.
bool SupportsCommand(int id) const;
// Returns true if the specified command ID is enabled. The command ID must be
// supported by this updater.
bool IsCommandEnabled(int id) const;
// Performs the action associated with this command ID.
// TODO(beng): get rid of this since it's effectively just a pass-thru and the
// call sites would be better off using more well defined delegate interfaces.
void ExecuteCommand(int id);
// An Observer interface implemented by objects that want to be informed when
// the state of a particular command ID is modified.
class CommandObserver {
public:
// Notifies the observer that the enabled state has changed for the
// specified command id.
virtual void EnabledStateChangedForCommand(int id, bool enabled) = 0;
protected:
virtual ~CommandObserver();
};
// Adds an observer to the state of a particular command. If the command does
// not exist, it is created, initialized to false.
void AddCommandObserver(int id, CommandObserver* observer);
// Removes an observer to the state of a particular command.
void RemoveCommandObserver(int id, CommandObserver* observer);
// Removes |observer| for all commands on which it's registered.
void RemoveCommandObserver(CommandObserver* observer);
// Notify all observers of a particular command that the command has been
// enabled or disabled. If the command does not exist, it is created and
// initialized to |state|. This function is very lightweight if the command
// state has not changed.
void UpdateCommandEnabled(int id, bool state);
private:
// A piece of data about a command - whether or not it is enabled, and a list
// of objects that observe the enabled state of this command.
class Command;
// Get a Command node for a given command ID, creating an entry if it doesn't
// exist if desired.
Command* GetCommand(int id, bool create);
// The delegate is responsible for executing commands.
CommandUpdaterDelegate* delegate_;
// This is a map of command IDs to states and observer lists
typedef base::hash_map<int, Command*> CommandMap;
CommandMap commands_;
CommandUpdater();
DISALLOW_COPY_AND_ASSIGN(CommandUpdater);
};
#endif // CHROME_BROWSER_COMMAND_UPDATER_H_
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