API정복 보다가 SendMessageCallback 함수가 나왔는데요
메시지 보내자마자 리턴해서 다른일 할수 있다하는데.. 왜 안되는거죠?
Send1 윈도우 , Send2 윈도우 만들어서
Send1에서 보내고 Send2에서 받게 한다음 Send2에서 for문 돌리는데.. 다 돌아야 Send1이 드래그도되고 닫기도 되고 하네요..
소스 올립니다.

// Send1
#include <windows.h>

LRESULT CALLBACK WndProc(HWND,UINT,WPARAM,LPARAM);
HINSTANCE g_hInst;
LPCTSTR lpszClass=TEXT("Send1");
HWND hWndMain;
int APIENTRY WinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance
      ,LPSTR lpszCmdParam,int nCmdShow)
{
 HWND hWnd;
 MSG Message;
 WNDCLASS WndClass;
 g_hInst=hInstance;

 WndClass.cbClsExtra=0;
 WndClass.cbWndExtra=0;
 WndClass.hbrBackground=(HBRUSH)(COLOR_WINDOW+1);
 WndClass.hCursor=LoadCursor(NULL,IDC_ARROW);
 WndClass.hIcon=LoadIcon(NULL,IDI_APPLICATION);
 WndClass.hInstance=hInstance;
 WndClass.lpfnWndProc=WndProc;
 WndClass.lpszClassName=lpszClass;
 WndClass.lpszMenuName=NULL;
 WndClass.style=CS_HREDRAW | CS_VREDRAW;
 RegisterClass(&WndClass);

 hWnd=CreateWindow(lpszClass,lpszClass,WS_OVERLAPPEDWINDOW,
  CW_USEDEFAULT,CW_USEDEFAULT,CW_USEDEFAULT,CW_USEDEFAULT,
  NULL,(HMENU)NULL,hInstance,NULL);
 ShowWindow(hWnd,nCmdShow);

 while (GetMessage(&Message,NULL,0,0)) {
  TranslateMessage(&Message);
  DispatchMessage(&Message);
 }
 return (int)Message.wParam;
}

VOID CALLBACK SendAsyncProc(HWND hWnd, UINT uMsg, ULONG_PTR dwData,LRESULT lResult)
{
 //MessageBox(hWndMain,TEXT("작업을 완료했습니다."),TEXT("Send1"),MB_OK);
}

LRESULT CALLBACK WndProc(HWND hWnd,UINT iMessage,WPARAM wParam,LPARAM lParam)
{
 HDC hdc;
 PAINTSTRUCT ps;
 static HWND hSend2;
 TCHAR *Mes = TEXT("왼쪽 버튼을 누르시오");

 switch (iMessage) {
  case WM_CREATE:
   hWndMain = hWnd;
   return 0;
  case WM_LBUTTONDOWN:
   hSend2 = FindWindow(NULL,TEXT("Send2"));
   if(hSend2 != NULL)
   {
     //SendMessageCallback(hSend2,WM_USER+1,0,0,SendAsyncProc,NULL);
    PostMessage(hSend2,WM_USER+1,0,0);
   }
   return 0;
 case WM_PAINT:
  hdc=BeginPaint(hWnd, &ps);
  TextOut(hdc,10,10,Mes,lstrlen(Mes));
  EndPaint(hWnd, &ps);
  return 0;
 case WM_DESTROY:
  PostQuitMessage(0);
  return 0;
 }
 return(DefWindowProc(hWnd,iMessage,wParam,lParam));
}
// Send2
#include <windows.h>

LRESULT CALLBACK WndProc(HWND,UINT,WPARAM,LPARAM);
HINSTANCE g_hInst;
LPCTSTR lpszClass=TEXT("Send2");

int APIENTRY WinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance
      ,LPSTR lpszCmdParam,int nCmdShow)
{
 HWND hWnd;
 MSG Message;
 WNDCLASS WndClass;
 g_hInst=hInstance;

 WndClass.cbClsExtra=0;
 WndClass.cbWndExtra=0;
 WndClass.hbrBackground=(HBRUSH)(COLOR_WINDOW+1);
 WndClass.hCursor=LoadCursor(NULL,IDC_ARROW);
 WndClass.hIcon=LoadIcon(NULL,IDI_APPLICATION);
 WndClass.hInstance=hInstance;
 WndClass.lpfnWndProc=WndProc;
 WndClass.lpszClassName=lpszClass;
 WndClass.lpszMenuName=NULL;
 WndClass.style=CS_HREDRAW | CS_VREDRAW;
 RegisterClass(&WndClass);

 hWnd=CreateWindow(lpszClass,lpszClass,WS_OVERLAPPEDWINDOW,
  CW_USEDEFAULT,CW_USEDEFAULT,CW_USEDEFAULT,CW_USEDEFAULT,
  NULL,(HMENU)NULL,hInstance,NULL);
 ShowWindow(hWnd,nCmdShow);

 while (GetMessage(&Message,NULL,0,0)) {
  TranslateMessage(&Message);
  DispatchMessage(&Message);
 }
 return (int)Message.wParam;
}

LRESULT CALLBACK WndProc(HWND hWnd,UINT iMessage,WPARAM wParam,LPARAM lParam)
{
 HDC hdc;
 PAINTSTRUCT ps;
 TCHAR str[128];
 switch (iMessage) {
  case WM_USER+1:
   for(int i=0;i<100000;i++){
    wsprintf(str,TEXT("%d"),i);
    SetWindowText(hWnd,str);
   }
   SetWindowText(hWnd,TEXT("Send2"));
   return 0;
 case WM_PAINT:
  hdc=BeginPaint(hWnd, &ps);
  EndPaint(hWnd, &ps);
  return 0;
 case WM_DESTROY:
  PostQuitMessage(0);
  return 0;
 }
 return(DefWindowProc(hWnd,iMessage,wParam,lParam));
}