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/* Copyright (C) 2009 Wildfire Games.
* This file is part of 0 A.D.
*
* 0 A.D. is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 2 of the License, or
* (at your option) any later version.
*
* 0 A.D. is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with 0 A.D. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef INCLUDED_COMMANDPROC
#define INCLUDED_COMMANDPROC
#include <string>
#include <list>
#include <map>
#include "SharedMemory.h"
namespace AtlasMessage
{
struct Command
{
virtual ~Command() {}
virtual void Do() = 0;
virtual void Undo() = 0;
virtual void Redo() = 0;
virtual void Merge(Command* prev) = 0;
virtual const char* GetType() const = 0;
};
class CommandProc
{
public:
CommandProc();
~CommandProc();
// Should be called before shutting down, so it can free
// references to entities/etc that are stored in commands
void Destroy();
void Submit(Command* cmd);
void Undo();
void Redo();
void Merge();
private:
std::list<Command*> m_Commands;
typedef std::list<Command*>::iterator cmdIt;
// The 'current' command is the latest one which has been executed
// (ignoring any that have been undone)
cmdIt m_CurrentCommand;
};
typedef Command* (*cmdHandler)(const void*);
typedef std::map<std::string, cmdHandler> cmdHandlers;
extern cmdHandlers& GetCmdHandlers();
CommandProc& GetCommandProc();
/*
We want the command handler implementations to be as pretty as possible - so let people write
BEGIN_COMMAND(CommandName)
{
int member;
cCommandName() { ... } // } both are optional; neither may
~cCommandName() { ... } // } make use of this->msg
void Do() { ... interact with this->msg ... }
void Undo() { ... }
void Redo() { ... }
void MergeIntoPrevious(cCommandName* prev) { ... } // iff this command is a mergeable one
};
END_COMMAND(CommandName)
which looks almost exactly like a class definition, and is about the simplest
system I can find.
The following macros convert that into:
class cCommandName_base : public Command
{
protected:
// Storage for data passed into this command
dCommandName* msg;
public:
// Ensure msg is initialised to something 'safe'
cCommandName_base : msg(NULL) {}
// MergeIntoPrevious should be overridden by mergeable commands, and implemented
// to update 'prev' to include the effects of 'this'. (A subclass overriding
// any function named 'MergeIntoPrevious' will hide this function, even if
// the types differ.)
void MergeIntoPrevious(void*) { ...error - needs to be overridden... }
};
// Use 'struct' for automatic publicness - we want users to write as little as possible
struct cCommandName : public cCommandName_base
{
// (user's command code - mostly overriding virtual methods from Command)
}
// Subclass the command to add things which require knowledge of the
// complete class definition
class cCommandName_sub : public cCommandName
{
public:
cCommandName_sub(dCommandName *data) { ...set msg... }
~cCommandName_sub() { ...clear msg... }
// Implement the relevant virtual methods from the Command base class,
// with automatic casting to the correct types and stuff
virtual void Merge(Command* prev) { ...call MergeIntoPrevious... }
virtual const char* GetType() const { return "CommandName"; }
// Factory method for creating an instance of this class, casting the
// data pointer into the right form (to avoid forcing the generic
// command-handling support code to worry about the types)
static Command* Create(const void* data) { ...return new cCommandName_sub... }
};
// Register.cpp wants to get that Create method, but it doesn't want to
// load all the class definitions; so define a simple method that just
// returns the address of Create
cmdHandler cCommandName_create()
{
return &cCommandName_sub::Create;
}
// (TODO: make sure this stays in sync with the code below)
*/
#define BEGIN_COMMAND(t) \
class c##t##_base : public Command \
{ \
protected: \
d##t* msg; \
public: \
c##t##_base() : msg(NULL) {} \
void MergeIntoPrevious(void*) { debug_warn(L"MergeIntoPrevious unimplemented in command " WIDEN(#t)); } \
}; \
struct c##t : public c##t##_base
#define END_COMMAND(t) \
class c##t##_sub : public c##t \
{ \
public: \
c##t##_sub(d##t* data) \
{ \
msg = data; \
} \
~c##t##_sub() \
{ \
/* (msg was allocated in mDoCommand(), using SHAREABLE_NEW) */ \
AtlasMessage::ShareableDelete(msg); \
msg = NULL; \
} \
virtual void Merge(Command* prev) { MergeIntoPrevious(static_cast<c##t##_sub*>(prev)); } \
virtual const char* GetType() const { return #t; } \
static Command* Create(const void* data) \
{ \
return new c##t##_sub (reinterpret_cast<d##t*>(const_cast<void*>(data))); \
} \
}; \
cmdHandler c##t##_create() \
{ \
return &c##t##_sub ::Create; \
}
}
#endif // INCLUDED_COMMANDPROC
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