Function Prototypes

Function prototypes are also provided in generic, ANSI, and Unicode varieties, as shown below. The generic function prototype consists of the standard function name implemented as a macro. The preprocessor expands each macro into one of the specific function prototypes, depending on whether UNICODE is defined. The letters A (ANSI) and W (wide) are added at the end of the function names in the specific function prototypes. In this example, the generic prototype uses the generic type LPTSTR for the text parameter, but the A and W prototypes use the LPCSTR and LPCWSTR character types, respectively.

SetWindowText(HWND hwnd, LPTSTR lpText);

SetWindowTextA(HWND hwnd, LPCSTR lpText);

SetWindowTextW(HWND hwnd, LPCWSTR lpText);

An application can use the generic function and make Unicode dependent on whether the UNICODE option is used to compile the code, or it can make mixed calls by using the explicit function names ending with A and W.

This three-prototype approach applies to all functions with text arguments. Always use a generic function prototype with the generic string and character types. All function names that end with an uppercase W take wide-character arguments.

Some functions exist only in wide-character versions and can be used only with the appropriate data type.

The reference material for each Unicode-enabled function is labeled with a Unicode icon. If the function exists as a macro that the preprocessor must expand into an ANSI or Unicode form, only the macro form is documented.

Note Whenever a function has a length parameter for a character string, the length should be given as a count of characters (TCHAR units) in the string. However, functions that require or return pointers to untyped memory blocks, such as the GlobalAlloc function, are exceptions.

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