Dave's Brain

Browse - programming tips - dialog box param

Date: 2004Aug24
OS: Windows

Q. Is there a way to avoid global variables with win32 dialogs?

A. Use DialogBoxParam() and Set/GetDialogData() like this:

inline void SetDialogData(const HWND hDlg, const LPVOID pVoid)
{
	SetWindowLongPtr(hDlg, DWL_USER, (LONG) pVoid);
}

inline LPVOID GetDialogData(const HWND hDlg)
{
	return (LPVOID) GetWindowLongPtr(hDlg, DWL_USER);
}

struct Record
{
   int     stuff1;
   int     stuff2;
   int     stuff3;
};

static BOOL __stdcall
MyDialogDlgProc(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam)
{
    WORD        id, code;

    switch (message)
    {
    case WM_INITDIALOG:
       {
           Record *pRecord = (Record *) lParam;

           SetDialogData(hDlg, pRecord);
           Load(hDlg, pRecord);
       }
       return TRUE;

    case WM_COMMAND:
       id = LOWORD(wParam);
       code = HIWORD(wParam);

       switch(id)
       {
       case IDOK: 
          {
             Record *pRecord = (Record *) GetDialogData(hDlg);

             Save(hDlg, pRecord);
             EndDialog(hDlg, IDOK);
          }
          break;

       case IDCANCEL:
          EndDialog(hDlg, IDCANCEL);
          break;
       }
       break; // end of WM_COMMAND
    }

    return FALSE;
}

int MyDialog(const HWND hDlg, Record *record)
{
   return DialogBoxParam(ghInstance, MAKEINTRESOURCE(IDD_MY_DIALOG), hDlg, (DLGPROC) MyDialogDlgProc, (LPARAM)record);
}

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