MFC dialog program core -isdialogmessage function -msg message structure -getmessage function -dispatchmessage function

stay MFC Programming , Common messages are as follows ：

#define WM_INITDIALOG 0x0110
#define WM_COMMAND 0x0111
#define WM_MOUSEMOVE 0x0200
#define WM_CREATE 0x0001
#define WM_DESTROY 0x0002
#define WM_MOVE 0x0003
#define WM_SIZE 0x0005
#define WM_PAINT 0x000F
#define WM_CLOSE 0x0010
#define WM_SHOWWINDOW 0x0018
#define SPI_SETGRADIENTCAPTIONS 0x1009

   if necessary Hook Window message , These functions must have some understanding of the program .

1.IsDialogMessage function

   The functionality ： This function determines whether a message is assigned to the specified dialog , If it is , Then process the message .　
   The function prototype ：BOOL IsDialogMessage(HWND hDlg,LPMSG IpMsg);
  hDlg： Identification dialog .
  IpMsg： Point to a that contains a message to be detected MSG structure .
   Return value ： If the message is processed , The return value is nonzero ; If the message is not processed , The return value is zero .
   Check whether the message is the dialog message of the corresponding handle , If it is , Then hand in one user32.dll Module alignment for processing , actually user32.dll The module forwards it to the window function to which the dialog belongs , Judge the message in the window function of the dialog box , Finally, call the function corresponding to the message , The function corresponding to the message is mapped previously , Already exists in the dialog message mapping table .

while(GetMessage(&stMsg,NULL,0,0))
{
    
	if(!IsDialogMessage(hDlg,&stMsg))
	{
    
		TranslateMessage(&stMsg);
		DispatchMessage(&stMsg);
	}
}

MSG Message structure
   stay Windows In the program , The news is from MSG To express by structure .
   Structural prototype ：

typedef struct tagMSG {
    
  HWND   hwnd;
  UINT   message;
  WPARAM wParam;
  LPARAM lParam;
  DWORD  time;
  POINT  pt;
} MSG, *PMSG, *LPMSG;

To obtain parameters , Then forward .

2.GetMessage function

   In the create window 、 Display window 、 After updating the window , We need to write a message loop , Constantly pulling messages from the message queue , And respond . To get a message from the message queue , We need to call GetMessage() function , The prototype declaration of this function is as follows ：

BOOL GetMessage(
          LPMSG lpMsg,              // address of structure with message
          HWND hWnd,                // handle of window
          UINT wMsgFilterMin,       // first message
          UINT wMsgFilterMax        // last message
);

   Parameters lpMsg Point to a message （MSG） Structure .GetMessage The message information retrieved from the thread's message queue will be saved in the structure object .
   Parameters hWnd Specify which window to receive messages from . Usually we set it to NULL, Used to receive window messages for all windows belonging to the calling thread .
   Parameters wMsgFilterMin Specify the minimum value of the message to get , Usually set to 0.
   Parameters wMsgFilterMax Specify the maximum number of messages to get . If wMsgFilterMin and wMsgFilter Max Set to 0, Then all messages are received .
  GetMessage Function received Division WM_QUIT All messages except return non-zero values . about WM_QUIT news , This function returns zero . If something goes wrong , This function returns -1, for example , When parameters hWnd Is an invalid window handle or lpMsg Is an invalid pointer .

3.DispatchMessage function

WINUSERAPI
LRESULT
WINAPI
DispatchMessageA(
    _In_ CONST MSG *lpMsg);

   The function prototype ：LONG DispatchMessage（CONST MSG*lpmsg）;
   Parameters ：lpmsg： Point to the... Containing the message MSG Pointer to structure .
   Return value ： The return value is the value returned by the window program . Although the meaning of the return value depends on the message being scheduled , But the return value is usually ignored .

4. Window procedure function model

LONG OldWndProc = 0;
LRESULT CALLBACK WindowProc2(  HWND hwnd,      // handle to window
							UINT uMsg,      // message identifier
							WPARAM wParam,  // first message parameter
							LPARAM lParam   // second message parameter
							)
{
    
	if (uMsg == WM_KEYDOWN)
	{
    
		if (wParam == VK_F6)
		{
    
			AfxMessageBox(L" You pressed F6 key ");
		}
	}
	return CallWindowProc((WNDPROC)OldWndProc,hwnd,uMsg,wParam,lParam);
}
 
void CttDlg::OnBnClickedOk()
{
    
	// TODO:  Add control notification handler code here 
	OldWndProc = ::SetWindowLong(m_hWnd,GWL_WNDPROC,(LONG)WindowProc2);
}

5. Author Q & A

   If you have any questions , Please leave a message .