This approach is more efficient than having a separate std::vector for buffer allocation, with a separate dynamic memory allocation, and then a deep-copy into the std::wstring. However, you have to pass the whole destination buffer length (*including* the terminating NUL) to GetWindowText() as third parameter. Note that the length value returned by GetWindowTextLength() excludes the terminating NUL. Str.resize(len) // make enough room in string Something like this: int len = GetWindowTextLength(hwnd) To obtain the exact length of the text, use the WM_GETTEXT, LB_GETTEXT, or CB_GETLBTEXT messages, or the GetWindowText function.Then how are you supposed to get any window text ?Īn option would be to make enough room inside the string for storing text in it. For more information on ANSI and ANSI functions, see Conventions for Function Prototypes. It can also occur when an application uses the ANSI version of GetWindowTextLength with a window whose window procedure is Unicode, or the Unicode version of GetWindowTextLength with a window whose window procedure is ANSI. This behavior can occur when an application uses both ANSI functions and common dialogs, which use Unicode. The return value, however, will always be at least as large as the actual length of the text you can thus always use it to guide buffer allocation. This occurs with certain mixtures of ANSI and Unicode, and is due to the system allowing for the possible existence of double-byte character set (DBCS) characters within the text. Under certain conditions, the GetWindowTextLength function may return a value that is larger than the actual length of the text.
If the target window is owned by the current process, GetWindowTextLength causes a WM_GETTEXTLENGTH message to be sent to the specified window or control. To determine success or failure, clear the most recent error information by calling SetLastError with 0, then call GetLastError.
This function does not clear the most recent error information.
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