RegisterWindowMessageA function (winuser.h)
Defines a new window message that is guaranteed to be unique throughout the system. The message value can be used when sending or posting messages.
UINT RegisterWindowMessageA( LPCSTR lpString );
The message to be registered.
If the message is successfully registered, the return value is a message identifier in the range 0xC000 through 0xFFFF.
If the function fails, the return value is zero. To get extended error information, call GetLastError.
The RegisterWindowMessage function is typically used to register messages for communicating between two cooperating applications.
If two different applications register the same message string, the applications return the same message value. The message remains registered until the session ends.
Only use RegisterWindowMessage when more than one application must process the same message. For sending private messages within a window class, an application can use any integer in the range WM_USER through 0x7FFF. (Messages in this range are private to a window class, not to an application. For example, predefined control classes such as BUTTON, EDIT, LISTBOX, and COMBOBOX may use values in this range.)
For an example, see Finding Text.
The winuser.h header defines RegisterWindowMessage as an alias which automatically selects the ANSI or Unicode version of this function based on the definition of the UNICODE preprocessor constant. Mixing usage of the encoding-neutral alias with code that not encoding-neutral can lead to mismatches that result in compilation or runtime errors. For more information, see Conventions for Function Prototypes.
|Minimum supported client||Windows 2000 Professional [desktop apps only]|
|Minimum supported server||Windows 2000 Server [desktop apps only]|
|Header||winuser.h (include Windows.h)|
|API set||ext-ms-win-ntuser-message-l1-1-0 (introduced in Windows 8)|