Print Page - Creating a simple COM example

Title: Creating a simple COM example - undeclared identifier
Post by: Vortex on May 05, 2013, 11:32:01 AM

Hello,

I am trying to convert my Poasm code to Pelles C :


#include <windows.h>

#include <shlobj.h>
#include <shlguid.h>

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
    LPSTR lpCmdLine, int nCmdShow)
{
	HRESULT     hr;
	IActiveDesktop *pAD;
	
	CoInitialize(0);

	hr = CoCreateInstance(&CLSID_ActiveDesktop,
						0,
						CLSCTX_INPROC_SERVER,
						&IID_IActiveDesktop,
						(void**) &pAD);
	
	pAD->Release();

	CoUninitialize();

	return 0;
}

The compiler reports the following error message :

Code Select

SetWallpaper.c(10): error #2048: Undeclared identifier 'IActiveDesktop'.
SetWallpaper.c(10): error #2048: Undeclared identifier 'pAD'.

The IActiveDesktop interface is defined in shlobj.h How to solve the problem above?

Title: Re: Creating a simple COM example - undeclared identifier
Post by: Vortex on May 05, 2013, 12:08:04 PM

I found this article :

PRB: ActiveDesktop Compilation Errors Under Visual C++ 6.0 MFC

http://support.microsoft.com/kb/196342/en-us

Adding #include <wininet.h> is solving the problem.

Title: Re: Creating a simple COM example - undeclared identifier
Post by: TimoVJL on May 05, 2013, 12:43:26 PM

Correct this line too:

Code Select

pAD->lpVtbl->Release(pAD);

Title: Re: Creating a simple COM example - undeclared identifier
Post by: Vortex on May 05, 2013, 12:49:37 PM

Hi Timo,

Thanks. This time, I have other problems :

Code Select

#include <windows.h>

#include <wininet.h>
#include <shlobj.h>
#include <shlguid.h>

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
    LPSTR lpCmdLine, int nCmdShow)
{
	HRESULT     hr;
	IActiveDesktop *pAD;
	WALLPAPEROPT wpo;
	
	LPCWSTR file1 = L"Test.bmp";
	CoInitialize(0);

	hr = CoCreateInstance(&CLSID_ActiveDesktop,
						0,
						CLSCTX_INPROC_SERVER,
						&IID_IActiveDesktop,
						(void**)&pAD);
	
	wpo.dwSize=sizeof(WALLPAPEROPT);
	wpo.dwStyle=WPSTYLE_CENTER;

	pAD->lpVtbl->SetWallpaper(file1,0);

    pAD->lpVtbl->SetWallpaperOptions(&wpo,0);

    pAD->lpVtbl->ApplyChanges(AD_APPLY_ALL);

	pAD->lpVtbl->Release(pAD);

	CoUninitialize();

	return 0;
}

Code Select

SetWallpaper.c(26): error #2140: Type error in argument 1 to 'function'; expected 'LPACTIVEDESKTOP' but found 'const wchar_t *'.
SetWallpaper.c(26): error #2070: Insufficient number of arguments to 'function'.
SetWallpaper.c(28): error #2140: Type error in argument 1 to 'function'; expected 'LPACTIVEDESKTOP' but found 'LPWALLPAPEROPT'.
SetWallpaper.c(28): error #2070: Insufficient number of arguments to 'function'.
SetWallpaper.c(30): error #2140: Type error in argument 1 to 'function'; expected 'LPACTIVEDESKTOP' but found 'int'.
SetWallpaper.c(30): error #2070: Insufficient number of arguments to 'function'.

Title: Re: Creating a simple COM example - undeclared identifier
Post by: TimoVJL on May 05, 2013, 12:53:10 PM

Don't forget object pointer:

Code Select

pAD->lpVtbl->SetWallpaper(pAD,file1,0);and these pragmas are useful

Code Select

#pragma comment(lib, "ole32.lib")
#pragma comment(lib, "uuid.lib")

Title: Re: Creating a simple COM example - undeclared identifier
Post by: Vortex on May 05, 2013, 06:34:52 PM

Hi Timo,

Adding the pointer solved the problem. As I was focused on the classical C++ syntax without the pointer, it was a bit confusing. Thanks for the info.

Pelles C forum

C language => Beginner questions => Topic started by: Vortex on May 05, 2013, 11:32:01 AM