Problem with the L prefix ( LPCWSTR typecast) in winAPI

Question

I'm new to winAPI and encountered a problem I can't seem to solve... Couldn't find a solution by google yet, either.

My program has several buttons of similar size so I made a macro to hide all the mess. The original macro was:

#define _BUTTON(s, x, y, v)    CreateWindowW(L"Button", (L)s, WS_VISIBLE | WS_CHILD, x, y, 75, 25, hWnd, (HMENU)v, 0, 0);

However, " L(s) " doesn't work with or without the parenthesis, on s or L . I also tried replacing L with LPCWSTR , WCHAR* , _T() , etc... The compiler error is always the same: "L (or LPCWSTR, etc) is not declared in this scope" although I thought it should be...

For now I resolved the issue by going with the non-Unicode:

#define _BUTTON(s, x, y, v)    CreateWindow("Button", s, WS_VISIBLE | WS_CHILD, x, y, 75, 25, hWnd, (HMENU)v, 0, 0);

But I'd like all the windows to support the same chars... Where is the problem?

Answer 1

One way is what RbMm metioned, like:

#define Create_Button(s, x, y, v)     CreateWindowW(L"Button", L##s, WS_VISIBLE | WS_CHILD, x, y, 75, 25, hWnd, (HMENU)v, 0, 0);

Another way is to use a common approach:

#define Create_ButtonA(s, x, y, v)    CreateWindowA("Button", s, WS_VISIBLE | WS_CHILD, x, y, 75, 25, hWnd, (HMENU)v, 0, 0);
#define Create_ButtonW(s, x, y, v)    CreateWindowW(L"Button", s, WS_VISIBLE | WS_CHILD, x, y, 75, 25, hWnd, (HMENU)v, 0, 0);
#ifdef _UNICODE
#define Create_Button(s, x, y, v)     Create_ButtonW(s, x, y, v)
#else
#define Create_Button(s, x, y, v)     Create_ButtonA(s, x, y, v)
#endif

Usage:

Create_Button(TEXT("name"),10,10,2);
Create_ButtonA("name",10,10,2);
Create_ButtonW(L"name",10,10,2);