mfc大观之五、六（消息机制和消息运行）

    写过windows程序的朋友都知道，win32主要是利用消息进行界面的编写的。那么在mfc中，系统是如何处理消息的。换句话说，mfc是如何利用类的特性进行消息的传递的。说到这，当让离不开之前说道的静态变量机制。事实上，mfc中所有的消息都是保存在静态全局变量中的。下面是一段示例代码，大家可以体会一下。

#include <iostream>
using namespace std;

class cobject;
struct runclass;

#define get_class(basic) \
  basic::get_run_class()

#define CREATE_MESSAGE(basic) \
  static runclass run_##basic; \
  static runclass* get_run_class() {return &run_##basic;} 

class cobject{

public:
  CREATE_MESSAGE(cobject)

public:
  cobject() {
    cout << "cobject::cobject()" << endl; 
  }
  virtual ~cobject() {
    cout << "cobject::~cobject()" << endl;
  }

  virtual void process() {
    cout << "cobject::process()" << endl;
  }

};

typedef void (cobject::*func)();

struct message {
  int id;
  func f;
};

struct runclass {
  char name[64];
  struct runclass* next;
  struct message msg;

};

runclass cobject::run_cobject = {"cobject", NULL, {0, &cobject::process}};


#define IMPLEMENT_MESSAGE(basic, origin) \
  runclass basic::run_##basic = {#basic, &origin::run_##origin, {0, static_cast<func>(&ctemplate::process)}}

class ctemplate : public cobject {

public:
  ctemplate() {
    cout << "ctemplate::ctemplate()" << endl;
  }
  ~ctemplate() {
    cout << "ctemplate::~ctemplate()" << endl;
  }

  void process() {
    cout << "ctemplate::process()" << endl;
  }

  CREATE_MESSAGE(ctemplate)
};

IMPLEMENT_MESSAGE(ctemplate, cobject);

bool 
isKindOf(runclass* basic, runclass* origin){
  if(NULL == basic || NULL == origin)
    return false;

  while(basic->next)
    basic = basic->next;

  return 0 == strcmp(basic->name, origin->name) ? true :false;
}

int
main(int argc, char* argv[]){

  return 0;
}

    有了消息之后，如果真的接收到了系统的消息，那么又改如何处理呢？之前我们编写mfc的代码，不知道大家有没有注意，同样一段代码，放在view里面可以，放在doc也可以，放在frame好像也没问题，这是为什么？其实不复杂，主要是mfc框架在处理消息的时候，会把frame、doc、view都遍历一遍，等到真的没有对应处理函数的时候才会返回上去，说到这里，大家应该有一些明白了。

#include <iostream>
using namespace std;

class cobject;
struct runclass;

#define get_class(basic) \
    basic::get_run_class()

#define CREATE_MESSAGE(basic) \
    static runclass run_##basic; \
    static runclass* get_run_class() {return &run_##basic;} 

class cobject{

public:
    CREATE_MESSAGE(cobject)

public:
    cobject() {
        cout << "cobject::cobject()" << endl; 
    }
    virtual ~cobject() {
        cout << "cobject::~cobject()" << endl;
    }

    virtual void process() {
        cout << "cobject::process()" << endl;
    }

};

typedef void (cobject::*func)();

struct message {
    int id;
    func f;
};

struct runclass {
    char name[64];
    struct runclass* next;
    struct message msg;

};

runclass cobject::run_cobject = {"cobject", NULL, {0, &cobject::process}};


#define IMPLEMENT_MESSAGE(basic, origin) \
    runclass basic::run_##basic = {#basic, &origin::run_##origin, {100, static_cast<func>(&ctemplate::process)}}

class ctemplate : public cobject {

public:
    ctemplate() {
        cout << "ctemplate::ctemplate()" << endl;
    }
    ~ctemplate() {
        cout << "ctemplate::~ctemplate()" << endl;
    }

    void process() {
        cout << "ctemplate::process()" << endl;
    }

    CREATE_MESSAGE(ctemplate)
};

IMPLEMENT_MESSAGE(ctemplate, cobject);

bool 
isKindOf(runclass* basic, runclass* origin){
    if(NULL == basic || NULL == origin)
        return false;

    while(basic->next)
        basic = basic->next;

    return 0 == strcmp(basic->name, origin->name) ? true :false;
}

bool
process_msg(cobject* c, int value){
    struct runclass* p;

    // process message, see if cobject can process it
    p = get_class(cobject);
    if(value == p->msg.id){
        (c->*(p->msg.f))();
        return true;
    }

    // process message, see if ctemplate can process it
    p = get_class(ctemplate);
    if(value == p->msg.id){
        (c->*(p->msg.f))();
        return true;
    }

    return false;
}

int
main(int argc, char* argv[]){

    return 0;
}