WChar to char

This is a discussion on WChar to char within the C++ Programming forums, part of the General Programming Boards category; Hello, i'm trying to use COM to interface with iactivedesktop inorder to change wallpaper on my desktop but i seemed ...

  1. #1
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    WChar to char

    Hello,

    i'm trying to use COM to interface with iactivedesktop inorder to change wallpaper on my desktop but i seemed to be having problems converting a WChar to a Char or somthing along thoghts lines.

    My code:
    Code:
    #include <stdio.h>
    #include <Windows.h>
    #include <WinInet.h>
    #include <ShlObj.h>
    #include <iostream>
    
    using namespace std;
    
    int main ()
    {
    	CoInitialize (0) ;
    
    	HRESULT hr;
    	IActiveDesktop *pActiveDesktop;
    
    	hr = CoCreateInstance(CLSID_ActiveDesktop, NULL, CLSCTX_INPROC_SERVER,
    						IID_IActiveDesktop, (void**)&pActiveDesktop);
    
    		
    	LPCWSTR  FilePath[77];	
    	FilePath = "C:/Documents and Settings/Michael Knights/My Documents/My Pictures/board.bmp";	
    	
    	pActiveDesktop -> SetWallpaper (FilePath,77);
    
    
    	WCHAR wcTemp[512] ;
    	hr = pActiveDesktop -> GetWallpaper (wcTemp, 512, 0);
    
    	MessageBoxW (0, wcTemp, 0, 0);
    
    	//cout << wcTemp;
    
    
    	pActiveDesktop->Release();
    
    	CoUninitialize ();
    
    	return 0;
    }
    the error's i get from my complier are:
    Cpp1.cpp(23) : error C2734: 'FilePath' : const object must be initialized if not extern
    Cpp1.cpp(24) : error C2440: '=' : cannot convert from 'char [77]' to 'const unsigned short [77]'
    There is no context in which this conversion is possible


    I would be greatful for any help,

    Chears.

  2. #2
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    assuming UNICODE is defined TEXT macro will convert from char* to wchar_t*.

    Code:
    LPCWSTR  FilePath = TEXT( "C:/Documents and Settings/Michael Knights/My Documents/My Pictures/board.bmp");
    If UNICODE is not defined you can force the coversion by using L
    Code:
    LPCWSTR  FilePath = L"C:/Documents and Settings/Michael Knights/My Documents/My Pictures/board.bmp";
    There are a few win32 api functions that do not like the forward *nix-style path separaters, but all of them use the normal MS-Windows style back-slashes.
    Last edited by Ancient Dragon; 04-16-2006 at 12:41 PM.

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    Tryed it and i got the same errors.

  4. #4
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    Quote Originally Posted by MK4554
    Tryed it and i got the same errors.

    repost code -- it works with VC++ 2005 Express. what version of VC++ are you using? you may need to include <tchar.h>

  5. #5
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    Quote Originally Posted by Ancient Dragon
    repost code -- it works with VC++ 2005 Express. what version of VC++ are you using? you may need to include <tchar.h>
    Code:
    #include <stdio.h>
    #include <Windows.h>
    #include <WinInet.h>
    #include <ShlObj.h>
    #include <iostream>
    #include <tchar.h>
    
    using namespace std;
    
    int main ()
    {
    	CoInitialize (0) ;
    
    	HRESULT hr;
    	IActiveDesktop *pActiveDesktop;
    	
    
    
    
    	hr = CoCreateInstance(CLSID_ActiveDesktop, NULL, CLSCTX_INPROC_SERVER,
    						IID_IActiveDesktop, (void**)&pActiveDesktop);
    
    		
    	LPCWSTR  FilePath[77];	
    	FilePath =  TEXT( "C:/Documents and Settings/Michael Knights/My Documents/My Pictures/board.bmp");	
    	
    	pActiveDesktop -> SetWallpaper (FilePath,77);
    
    
    	WCHAR wcTemp[512] ;
    	hr = pActiveDesktop -> GetWallpaper (wcTemp, 512, 0);
    
    	MessageBoxW (0, wcTemp, 0, 0);
    
    	//cout << wcTemp;
    
    
    	pActiveDesktop->Release();
    
    	CoUninitialize ();
    
    	return 0;
    }


    hey,
    i'm useing vs6 ( yeh i know ) and i just tryed what u told me and it didnt work hmm i dont know what else to try....
    Last edited by MK4554; 04-16-2006 at 03:08 PM.

  6. #6
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    Code:
    LPCWSTR  FilePath[77];	
    	FilePath =  TEXT( "C:/Documents and Settings/Michael Knights/My Documents/My Pictures/board.bmp");
    for arrays, you can only make direct assignment during initialization. once created, your only option is to copy the data manually (using wstrcpy, memcpy, etc). of course, you could use a std::wstring instead which would allow you to use that construct.

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    [QUOTE=MK4554]
    Code:
    	LPCWSTR  FilePath[77];	
    	FilePath =  TEXT( "C:/Documents and Settings/Michael Knights/My Documents/My Pictures/board.bmp");
    That is not like the example I posted. character arrays cannot be assigned that way. See the example I posted for the correct method. Another way is like this
    Code:
    LPCWSTR FilePath[] = TEXT( "C:/Documents and Settings/Michael Knights/My Documents/My Pictures/board.bmp");
    If FilePath was declared someplace else, then use one of the conversion functions previously posted.

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    hey,
    i found what my problem is now its that

    pActiveDesktop -> SetWallpaper (FilePath,77);

    doesnt work probly with varibles i dunno why but it does the only way i can get it to work is by doing somthing like

    pActiveDesktop -> SetWallpaper (L"C:\joke.jpg",0);

    does anyone know how to use a varable insade of this.

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    this is from a project I got from codeproject.com. I illustrates the use of that and other functions
    Code:
    void CWallpaperQDlg::ChangeWallpaper(int iRandom)
    {
    	USES_CONVERSION;
    
    	int iImageNum = 0;
    	int iPosition = 1;
    	CString cstrTileWallpaper;
    	CString cstrWallpaperStyle;
    	TCHAR szBuf[MAX_PATH];
    
    	// Choose then next image in the list, or choose a random image.
    	if (iRandom == 1)
    	{
    		srand((unsigned)time(NULL));
    
    		iImageNum = rand()%m_lbQList.GetCount();
    
    		iCurrentImage = iImageNum;
    	}
    	else
    	{
    		iCurrentImage++;
    		if (iCurrentImage + 1 > m_lbQList.GetCount()) iCurrentImage = 0;
    		CRegistry::SetRegDWORD("Software\\JasonSoft\\WallpaperQ", "CurrentImage", (DWORD)iCurrentImage);
    
    		iImageNum = iCurrentImage;
    	}
    
    	// Get the image path from the registry by the image number.
    	iPosition = (int)m_lbQList.GetItemData(iImageNum);
    	m_lbQList.GetText(iImageNum, szBuf);
    
    	if (szBuf[0] != '/0')
    	{
    		// If Active Desktop is not available, use the SystemParametersInfo function.
    		if (pIActiveDesktop == NULL)
    		{
    			if (iPosition == 0)
    			{
    				// Tiled
    				cstrTileWallpaper = "1";
    				cstrWallpaperStyle = "1";
    			}
    			else if (iPosition == 1)
    			{
    				// Center
    				cstrTileWallpaper = "0";
    				cstrWallpaperStyle = "1";
    			}
    			else
    			{
    				// Stretch
    				cstrTileWallpaper = "0";
    				cstrWallpaperStyle = "2";
    			}
    
    			// Set registry values for the wallpaper position.
    			CRegistry::SetRegString("Control Panel\\Desktop", "TileWallpaper", cstrTileWallpaper);
    			CRegistry::SetRegString("Control Panel\\Desktop", "WallpaperStyle", cstrWallpaperStyle);
    
    			// Change the wallpaper.
    			SystemParametersInfo(SPI_SETDESKWALLPAPER, 0, (void*)szBuf, 
    				SPIF_UPDATEINIFILE | SPIF_SENDWININICHANGE);	
    		}
    		else
    		{
    			WALLPAPEROPT wpOptions;
    			COMPONENTSOPT compOptions;
    
    			compOptions.dwSize = sizeof(COMPONENTSOPT);
    			compOptions.fActiveDesktop = TRUE;
    			compOptions.fEnableComponents = TRUE;
    
    			pIActiveDesktop->SetDesktopItemOptions(&compOptions, 0);
    
    			// Set the wallpaper position.
    			wpOptions.dwSize = sizeof(WALLPAPEROPT);
    			if (iPosition == 0)
    				wpOptions.dwStyle = WPSTYLE_TILE;
    			else if (iPosition == 1)
    				wpOptions.dwStyle = WPSTYLE_CENTER;
    			else
    				wpOptions.dwStyle = WPSTYLE_STRETCH;
    
    			pIActiveDesktop->SetWallpaperOptions(&wpOptions, 0);
    
    			// Set the wallpaper image.
    
    			pIActiveDesktop->SetWallpaper(T2CW(szBuf), 0);
    
    			// Apply all changes.
    			pIActiveDesktop->ApplyChanges(AD_APPLY_ALL);
    		}
    
    		if (iExitAfter == 1) OnExit();
    	}
    }

  11. #11
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    what the hell is T2CW?

  12. #12
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    A macro that converts from char* to wchar_t*

  13. #13
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    do you know how i would go about including it - i did search the internet befoure asking.

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    You might want to read this article about unicode conversions. That macro is defined in atlconv.h

  15. #15
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    Quote Originally Posted by Ancient Dragon
    You might want to read this article about unicode conversions. That macro is defined in atlconv.h
    ok i hade ago at using it but when i did i got header file errors such as:
    c:\program files\microsoft visual studio\vc98\include\wininet.h(48) : error C2146: syntax error : missing ';' before identifier 'HINTERNET'
    c:\program files\microsoft visual studio\vc98\include\wininet.h(48) : fatal error C1004: unexpected end of file found
    Error executing cl.exe.
    is it possable if somone isnt too busy that they could write me a quick example of using T2CW.

    btw Thank you for that link i read the whole page i must addmit i didnt understand everything but most of it i did.

    Edit:

    btw i figured out that setwallpaper has this syntax

    HRESULT SetWallpaper( LPCWSTR pwszWallpaper,
    DWORD dwReserved
    );

    i don't think it helps much but i may was well post it
    Last edited by MK4554; 04-19-2006 at 05:28 AM.

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