following book examples using Unicode Character Set - windows

Question

I'm reading a book called "Introduction to 3D Game Programming with DirectX 9.0c: A Shader Approach" and I was following the codes there but the application used Multi-Byte Character Set and I read from somewhere that it's not a good practice to use that and im having error when creating a window. here is the code that im having error.
mhMainWnd = CreateWindow(L"D3DWndClassName", mMainWndCaption.c_str(), WS_OVERLAPPEDWINDOW,
GetSystemMetrics(SM_CXSCREEN)/2 - width/2,
GetSystemMetrics(SM_CYSCREEN)/2 - height/2,
R.right, R.bottom, 0, 0, mhAppInst, 0);
then the eror is:
error C2664: 'CreateWindowExW' : cannot convert parameter 2 from 'const char [16]' to 'LPCWSTR'
hope someone can help me

Answer 1

What you heard about the preferability of Unicode over the ANSI/MBCS is entirely correct. All new Windows code should be written to work with Unicode. In order to make this happen, you have to ensure two things:
Both the UNICODE and _UNICODE symbols need to be defined globally to ensure that the Unicode versions of the API functions are called, even if you forget the W suffix.
You can either do this at the top of your precompiled header
#define UNICODE
#define _UNICODE
or in your project's Properties window within Visual Studio. Simply add both of the values to the list.
All of your strings (both literals and otherwise) need to be Unicode strings.
With literals, you accomplish this by prefixing them with L, just as you've done in the example: L"D3DWndClassName"
With strings that are allocated at runtime, you need to use the wchar_t type. Since you're using C++, you should obviously be using a string class rather than raw character arrays like you would in C. So you need to use a string class that treats the characters in the string as wchar_t. This would either be std::wstring or MFC/ATL/WTL's CStringW class.
It looks like you've got most of this down already. The culprit is mMainWndCaption.c_str(). You are using std::string (which returns a nul-terminated array of chars) instead of std::wstring (which returns a nul-terminated array of wchar_ts).

Answer 2

Either change your project to ANSI or MBCS rather than UNICODE, then change
L"D3DWndClassName"
to
"D3DWndClassName"
or, leave your project properties as UNICODE but use a UNICODE string of your window caption - so
CString szCaption(mMainWndCaption.c_str()); // CString is actually CStringW in UNICODE build
mhMainWnd = CreateWindow(L"D3DWndClassName", szCaption, WS_OVERLAPPEDWINDOW,
GetSystemMetrics(SM_CXSCREEN)/2 - width/2,
GetSystemMetrics(SM_CYSCREEN)/2 - height/2,
R.right, R.bottom, 0, 0, mhAppInst, 0);