Example Shows How to Pass Objects to FLL

• Microsoft Visual FoxPro for Windows, version 3.0b

SUMMARY

Visual FoxPro provides eight new API routines that allow you to manipulate Visual FoxPro objects and controls. In addition, the Value structure defined in the Library Construction Kit (LCK) has been expanded to use object references. This article gives an example showing how to pass and receive object references within an LCK routine.

MORE INFORMATION

The following C code illustrates how to use one of the new API routines, which requires an object reference (_WGetObjectClientWindow) and returns a handle to the window containing the passed object. The LCK routine clears the command button from the window to verify that the program is working as expected.

FoxPro Code

* Place the following code in the Click event of a button on a form: SET LIBRARY TO clearwind.FLL ADDITIVE = CLEARWIND(this) && we are passing the button object to the C routine RELEASE LIBRARY clearwind

C Code

#include <pro_ext.h>

void FAR ClearObjWin(ParamBlk FAR *parm)

   WHANDLE Wh;
   \\ Note that you are passing the address to the Value structure.
   Wh = _WGetObjectClientWindow(&parm->p[0].val);
   _WClear(Wh);

\\ Note below that the parameter type is "O" (for Object). FoxInfo myFoxInfo[] = {

   {"CLEARWIND", (FPFI) ClearObjWin, 1, "O"},

FoxTable _FoxTable = {

   (FoxTable FAR *) 0, sizeof(myFoxInfo)/sizeof(FoxInfo), myFoxInfo

REFERENCES

For more information about building FLLs for Visual FoxPro, please see the following articles in the Microsoft Knowledge Base:

   ARTICLE-ID: Q135709
   TITLE     : PRB: Visual C++ Link Error LNK2001: unresolved external
               symbol

   ARTICLE-ID: Q137059
   TITLE     : DOCERR: Missing Visual C/C++ "Multithreaded Using DLL"
               Setting