Convert Char * to Lpwstr

Convert char[] to LPCWSTR

For this specific case, the fix is quite simple:

wchar_t szBuff[64];
swprintf(szBuff, L"%p", m_hWnd);
MessageBox(NULL, szBuff, L"Test print handler", MB_OK);

That is, use Unicode strings throughout. In general, when programming on Windows, using wchar_t and UTF-16 is probably the simplest. It depends on how much interaction with other systems you have to do, of course.

For the general case, if you've got an ASCII (or char *) string, use either WideCharToMultiByte for the general case, or mbstowcs as @Matthew points out for simpler cases (mbstowcs works if the string is in the current C locale).

Cannot convert CHAR to LPWSTR

Instead of your current code:

FILE *sortie;
char fichier[256];//   <--- HERE s my char table

int main(int argc, char *argv[])
{
    //on masque 
    HWND hwnd = GetForegroundWindow();
    ShowWindow(hwnd, SW_HIDE);

    int i, lettre, result, lastresult, lastletter, compteur;

    GetCurrentDirectory(256, fichier); 
    strcat(fichier, "\\fichierlog.txt");

do e.g.

auto main() -> int
{
    //on masque 
    HWND hwnd = GetForegroundWindow();
    ShowWindow(hwnd, SW_HIDE);

    int i, lettre, result, lastresult, lastletter, compteur;

    std::wstring fichier( MAX_PATH, L'\0' );//   <--- HERE s my char table
    const DWORD len = GetCurrentDirectory( fichier.size(), &fichier[0] );
    if( len == 0 || len >= fichier.size() ) { throw std::runtime_error( "GetCurrentDirectory failed." ); }
    fichier.resize( len );
    fichier += L"/fichierlog.txt";

    std::ifstream sortie( fichier );

This should fix three issues:

• You're compiling as Unicode (probably a Visual Studio project), but the code is for the Windows ANSI API.

• You're using a C++ compiler, but the code is low level C.

• Too small buffer for maximum path length, and possible buffer overrun for the concatenation.

Note that the ifstream constructor that accepts a wide string is a Microsoft extension. It will however be practically required for Windows C++ compilers by the file system addition to the standard library in C++17.

LPCWSTR to char* and vice versa

The most probable reason that you had no problem before is that you turned on unicode in Visual C++ project's settings. See the accepted answer here to turn it off again (if it's possible for you):
How do I turn off Unicode in a VC++ project?

Otherwise you need to convert char * to wchar_t * using MultiByteToWideChar function.

E0513 a value of type const char * cannot be assigned to an entity of type LPCWSTR

The W in LPCWSTR stands for wide.

You are passing the narrow characters, while you program is compiled as UNICODE.

You can either add a prefix L to all you strings or use a _T() macro.

For example:

windowclass.lpszClassName = L"CrystalWindow";

Convert char * to LPWSTR

The std::mbstowcs function is what you are looking for:

 char text[] = "something";
 wchar_t wtext[20];
 mbstowcs(wtext, text, strlen(text)+1);//Plus null
 LPWSTR ptr = wtext;

for strings,

 string text = "something";
 wchar_t wtext[20];
 mbstowcs(wtext, text.c_str(), text.length());//includes null
 LPWSTR ptr = wtext;

--> ED: The "L" prefix only works on string literals, not variables. <--

Cannot convert parameter from 'const char[20]' to 'LPCWSTR'

You have UNICODE defined, so MessageBox is expecting a wide string.

Cannot convert argument 1 from 'const char [11]' to 'LPCWSTR'

1. Put a 'L' in front of the "example.bmp" string, e.g:

   file = CreateFile(L"exmple.bmp",GENERIC_WRITE, 0, NULL, CREATE_ALWAYS,FILE_ATTRIBUTE_NORMAL, NULL);
   

2. This transforms "example.bmp" into a wide-character string.

argument of type char * is incompatible with parameter of type LPCWSTR

You're building with the UNICODE macro defined, which means that all functions default to their wide-character equivalent. So when you call SetConsoleTitle that's really a macro that expands to SetConsoleTitleW.

A wide character has the type wchar_t and is incompatible with char.

You either have to explicitly call SetConsoleTitleA, remove the definition of UNICODE, or start using TCHAR and related types and macros.

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