How to call c function in C++?

Question

Hi,

I have a c header file in C:\Program Files\Microsoft SDKs\Windows\v7.0A\Include\UIAutomation.h. I want to call a function ElementFromPoint in my C++ app. I have written below code

#include "stdafx.h"
#include "afxwinappex.h"
#include "afxdialogex.h"
#include "FirstMFCApplication.h"
#include "MainFrm.h"
#include <UIAutomation.h>
#include <UIAutomationClient.h>
#include <UIAutomationCore.h>
#include <UIAutomationCoreApi.h>
#include <WinDef.h>
#include <Windows.h>
#include "FirstMFCApplicationDoc.h"
#include "FirstMFCApplicationView.h"

extern "C" HRESULT ElementFromPoint([in] POINT pt, [out, retVal IUIAutomationElement **element);

But when i compile i am getting below errors.

Error 1 error C3115: 'in': this attribute is not allowed on 'pt' d:\tutorial\c++\firstmfcapplication\firstmfcapplication\firstmfcapplication.cpp 230 1 FirstMFCApplication
Error 2 error C2337: 'retVal' : attribute not found d:\tutorial\c++\firstmfcapplication\firstmfcapplication\firstmfcapplication.cpp 230 1 FirstMFCApplication
Error 3 error C2146: syntax error : missing ']' before identifier 'IUIAutomationElement' d:\tutorial\c++\firstmfcapplication\firstmfcapplication\firstmfcapplication.cpp 230 1 FirstMFCApplication
Error 4 error C2061: syntax error : identifier 'IUIAutomationElement' d:\tutorial\c++\firstmfcapplication\firstmfcapplication\firstmfcapplication.cpp 230 1 FirstMFCApplication

I doubt my syntax is correct and that UIAutomation.h is actually a c header. I just want to call some of the c functions in my C++ app. Please help.

Thanks,

Pratap

Answer 1

Pratap15 wrote:

I have a c header file in C:\Program Files\Microsoft  SDKs\Windows\v7.0A\Include\UIAutomation.h. I want to call a function
ElementFromPoint in my C++ app. I have written below code

extern "C" HRESULT ElementFromPoint([in] POINT pt, [out, retVal  IUIAutomationElement **element);

If you are talking about this:

http://msdn.microsoft.com/en-us/library/windows/desktop/ee671538.aspx

then ElementFromPoint is not a C nor a C++ function, but a COM interface  method. You have to first create a CUIAutomation object, then call a  method on this object.

You might want to study this sample:

http://code.msdn.microsoft.com/windowsdesktop/UI-Automation-Document-24a3 7c82

I doubt my syntax is correct

Your doubt is well founded.

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Igor Tandetnik