A Password .DLL File That Can Be Called Anywhere in FoxPro

The information in this article applies to:

• Microsoft Visual FoxPro for Windows, versions 3.0, 5.0
• Microsoft FoxPro for Windows, versions 2.5, 2.5a, 2.5b, 2.6, 2.6a

SUMMARY

This article shows by example code how to generate a modal dialog box on top of the FoxPro desktop. The structure of code in this article follows the same structure shown in the LCK manual -- FoxPro code is given first followed by the C code. The C code was compiled using Visual C++ version 1.5.

MORE INFORMATION

The following example creates a .DLL that defines a modal dialog box for passwords. This is a generic example where the user can pass both the dialog title and the length of the password. The .DLL will return the password to FoxPro.

FoxPro Code

   CLEAR
   CLOSE DATABASES
   PASSWORD=SPACE(50)   && DEFINE THE PASSWORD TO BE
                        && OF 50 ELEMENTS
   SET LIBRARY TO SYS(2004)+'FOXTOOLS' && SET THE LIBRARY TO FOXTOOLS
   FHANDLE=MAINHWND()   && RETURN FOXPRO MAIN SCREEN HANDLE
   FUNCHANDLE=REGFN("MyInputBox","LC@CI","I","C:\FPW26\PASSWORD.DLL")
   * THE .DLL TITLE IS "PASSWORD DIALOG"
   * THE FHANDLE IS THE FOXPRO DESKTOP HANDLE
   * THE FUNCHANDLE IS A HANDLE TO THE FUNCTION IN THE .DLL
   * THE .DLL RETURNS THE PASSWORD IN THE VARIABLE PASSWORD
   =CALLFN(FUNCHANDLE,FHANDLE,"PASSWORD DIALOG",@PASSWORD,50)
   PASSWORD=ALLTRIM(PASSWORD) && TRIM PROCEEDING SPACES
   RELEASE LIBRARY SYS(2004)+'FOXTOOLS'

C Code

Because this is a true .DLL and not an .FLL, all required functions of the .DLL must be included. These files are: the C code file, the resource file (RC), and the definition file (DEF). These files are required to compile any true Windows .DLL file

To generate the .DLL file, you need a text editor and a C for Windows compiler. This example was compiled using Visual C++ version 1.5

1. Create a text file with your favorite text editor or use the Visual Workbench if you are using Visual C++. Type in the following code into the file, and save it as MYDLL.C:

      #include <windows.h>
      #include "mydll.h"
   
      // Data Structures
      typedef struct tagXFERBUFFER2
      {char *lpszTitle;
      LPSTR lpszBuffer;
      int *length;
      }XFERBUFFER2;
      //Prototyping
      BOOL FAR PASCAL _export InputBoxDlgProc(HWND hDlg, UINT
      message,WPARAM wParam, LPARAM lParam);
      int FAR PASCAL _export WEP(int nShutDownFlag);
      int FAR PASCAL _export MyInputBox(HWND hWndParent, LPCSTR
      lpszTitle,LPSTR Buffer, int StrLen);
      HINSTANCE ghInstance;
      /*******************************************/
      /* THE FOLLOWING FUNCTION  (LibMain) IS    */
      /* NEEDED FOR EVERY .DLL                   */
      /*******************************************/
      int FAR PASCAL LibMain(HINSTANCE hInstance, WORD wDataSeg,
      WORD wHeapSize, LPSTR lpszCmdLine)
      {ghInstance=hInstance;
      if (wHeapSize > 0)
      UnlockData(0);
      ghInstance = hInstance;
      return 1;}
      /*******************************************/
      /* THE FOLLOWING FUNCTION  (WEP) IS    */
      /* NEEDED FOR EVERY .DLL                   */
      /*******************************************/
      int FAR PASCAL _export WEP(int nShutDownFlag)
      { return 1;}
      /*******************************************/
      /* THE FOLLOWING FUNCTION  (MyInputBox) IS*/
      /* WHAT THE FOXPRO .PRG CALLS*/
      /*******************************************/
      /*******************************************/
      int FAR PASCAL _export MyInputBox(HWND hWndParent,
      LPCSTR lpszTitle,LPSTR Buffer, int Length)
      {DLGPROC lpfnInputBoxDlgProc;
      XFERBUFFER2 XferBuffer;
      int Result;
      XferBuffer.lpszTitle = (char *) lpszTitle;
      XferBuffer.lpszBuffer = (LPSTR) Buffer;
      XferBuffer.length = &Length;
      lpfnInputBoxDlgProc= (DLGPROC)
      MakeProcInstance((FARPROC)InputBoxDlgProc, ghInstance);
      Result=DialogBoxParam(ghInstance,"INPUTDIALOG",
      hWndParent,lpfnInputBoxDlgProc,(LPARAM)&XferBuffer);
      FreeProcInstance((FARPROC)lpfnInputBoxDlgProc);
      return Result;}
      /*******************************************/
      BOOL FAR PASCAL _export InputBoxDlgProc(HWND hDlg,
      UINT message,WPARAM wParam, LPARAM lParam)
      {static XFERBUFFER2 *XferBuffer;
      switch(message)
      {case WM_INITDIALOG :
      {XferBuffer = (XFERBUFFER2*)lParam;
      SetWindowText(hDlg, XferBuffer->lpszTitle);
      return TRUE; }
      case WM_COMMAND :
      {switch(wParam)
      {case IDOK :
      {int NumChars;
      NumChars=GetDlgItemText(hDlg,IDD_EDIT,
      (XferBuffer->lpszBuffer+'\0'),
      *XferBuffer->length+'\0');
      EndDialog(hDlg,NumChars);
      break; }
      case IDCANCEL :
      {  EndDialog(hDlg, 0);
      break;}}}}
      return FALSE;}
   
   

2. Create a new text file, type the following code into it, and save it as MYDLL.DEF:

      LIBRARY    mydll
      EXETYPE    WINDOWS
      CODE       PRELOAD MOVEABLE DISCARDABLE
      DATA       PRELOAD SINGLE
      HEAPSIZE   1024
      EXPORTS    MyInputBox
   
   

3. Create a new text file. Type the following code into it, and save it as MYDLL.RC:

      #include <windows.h>
      #include "mydll.h"
      INPUTDIALOG DIALOG 20, 24, 180, 64
      STYLE WS_POPUP | WS_CAPTION | DS_SETFONT
      FONT 8, "Helv"
      BEGIN
      CONTROL "", IDD_EDIT, "EDIT", WS_CHILD | WS_VISIBLE | WS_BORDER |
      WS_TABSTOP | ES_AUTOHSCROLL  | ES_PASSWORD, 10, 20, 160, 12
      DEFPUSHBUTTON "&OK", IDOK, 47, 42, 40, 14
      PUSHBUTTON "&Cancel", IDCANCEL, 93, 42, 40, 14
      END
   
   

4. Create a new text file, type the following line of code into it, and save it as MYDLL.H:

      #define IDD_EDIT    200
   
   

5. In Visual C++, create a new project and name it PASSWORD.

6. From the Option menu, choose Project, and select "Windows dynamic-link library (DLL)" as the project type.

7. Add the files MYDLL.C, MYDLL.DEF, and MYDLL.RC to the project.

8. From the project menu, choose build PASSWORD.DLL

9. Run the code in FoxPro.