Function GetWindowTextTimeout

source/window.cpp:1361–1466

int GetWindowTextTimeout(HWND aWnd, LPTSTR aBuf, INT_PTR aBufSize, UINT aTimeout)
// This function must be kept thread-safe because it may be called (indirectly) by hook thread too.
// aBufSize is an int so that any negative values passed in from caller are not lost.
// Returns the length of what would be copied (not including the zero terminator).
// In addition, if aBuf is not NULL, the window text is copied into aBuf (not to exceed aBufSize).
// AutoIt3 author indicates that using WM_GETTEXT vs. GetWindowText() sometimes yields more text.
// Perhaps this is because GetWindowText() has built-in protection against hung windows and
// thus isn't actually sending WM_GETTEXT.  The method here is hopefully the best of both worlds
// (protection against hung windows causing our thread to hang, and getting more text).
// Another tidbit from MSDN about SendMessage() that might be of use here sometime:
// "However, the sending thread will process incoming nonqueued (those sent directly to a window
// procedure) messages while waiting for its message to be processed. To prevent this, use
// SendMessageTimeout with SMTO_BLOCK set."  Currently not using SMTO_BLOCK because it
// doesn't seem necessary.
// Update: GetWindowText() is so much faster than SendMessage() and SendMessageTimeout(), at
// least on XP, so GetWindowTextTimeout() should probably only be used when getting the max amount
// of text is important (e.g. this function can fetch the text in a RichEdit20A control and
// other edit controls, whereas GetWindowText() doesn't).  This function is used to implement
// things like WinGetText and ControlGetText, in which getting the maximum amount and types
// of text is more important than performance.
{
	if (!aWnd || (aBuf && aBufSize < 1)) // No HWND or no room left in buffer (some callers rely on this check).
		return 0; // v1.0.40.04: Fixed to return 0 rather than setting aBuf to NULL and continuing (callers don't want that).

	LRESULT result, length;
	if (aBuf)
	{
		*aBuf = '\0';  // Init just to get it out of the way in case of early return/error.
		if (aBufSize == 1) // Room only for the terminator, so go no further (some callers rely on this check).
			return 0;

		// Below demonstrated that GetWindowText() is dramatically faster than either SendMessage()
		// or SendMessageTimeout() (noticeably faster when you have hotkeys that activate
		// windows, or toggle between two windows):
		//return GetWindowText(aWnd, aBuf, aBufSize);
		//return (int)SendMessage(aWnd, WM_GETTEXT, (WPARAM)aBufSize, (LPARAM)aBuf);

		// Don't bother calling IsWindowHung() because the below call will return
		// nearly instantly if the OS already "knows" that the target window has
		// be unresponsive for 5 seconds or so (i.e. it keeps track of such things
		// on an ongoing basis, at least XP seems to).
		result = SendMessageTimeout(aWnd, WM_GETTEXT, (WPARAM)aBufSize, (LPARAM)aBuf
			, SMTO_ABORTIFHUNG, aTimeout, (PDWORD_PTR) &length);
		if (length >= aBufSize) // Happens sometimes (at least ==aBufSize) for apps that wrongly include the terminator in the reported length.
			length = aBufSize - 1; // Override.

		// v1.0.40.04: The following check was added because when the text is too large to to fit in the
		// buffer, the OS (or at least certain applications such as AIM) return a length that *includes*
		// the zero terminator, violating the documented behavior of WM_GETTEXT.  In case the returned
		// length is too long by 1 (or even more than 1), calculate the length explicitly by checking if
		// there's another terminator to the left of the indicated length.  The following loop
		// is used in lieu of strlen() for performance reasons (because sometimes the text is huge).
		// It assumes that there will be no more than one additional terminator to the left of the
		// indicated length, which so far seems to be true:
		for (LPTSTR cp = aBuf + length; cp >= aBuf; --cp)
		{
			if (!*cp)
			{