if (wroteSome) {
	    return errorCode;
	} else if (statePtr->outQueueHead == NULL) {
	    ResetFlag(statePtr, BG_FLUSH_SCHEDULED);
	    (chanPtr->typePtr->watchProc)(chanPtr->instanceData,
		    statePtr->interestMask);
	} else {
	    /* TODO: If code reaches this point, it means a writable


	     * event is being handled on the channel, but the channel




	     * could not in fact be written to.  This ought not happen,

	     * but Unix pipes appear to act this way (see io-53.4).

	     * Also can imagine broken reflected channels. */
	}
    }

    /*
     * If the channel is flagged as closed, delete it when the refCount drops
     * to zero, the output queue is empty and there is no output in the
     * current output buffer.

    /*
     * When the channel has an escape sequence driven encoding such as
     * iso2022, the terminated escape sequence must write to the buffer.
     */

    stickyError = 0;

    if (GotFlag(statePtr, TCL_WRITABLE) && (statePtr->encoding != NULL)
	    && !(statePtr->outputEncodingFlags & TCL_ENCODING_START)) {

	int code = CheckChannelErrors(statePtr, TCL_WRITABLE);

	if (code == 0) {
	    statePtr->outputEncodingFlags |= TCL_ENCODING_END;
	    code = WriteChars(chanPtr, "", 0);
	    statePtr->outputEncodingFlags &= ~TCL_ENCODING_END;
	    statePtr->outputEncodingFlags |= TCL_ENCODING_START;
	}
	if (code < 0) {
	    stickyError = Tcl_GetErrno();
	}

	/*
	 * TIP #219, Tcl Channel Reflection API.
	 * Move an error message found in the channel bypass into the
	 * interpreter bypass. Just clear it if there is no interpreter.

    /*
     * If we are flushing in the background, be sure to call FlushChannel for
     * writable events. Note that we have to discard the writable event so we
     * don't call any write handlers before the flush is complete.
     */

    if (GotFlag(statePtr, BG_FLUSH_SCHEDULED) && (mask & TCL_WRITABLE)) {
	if (0 == FlushChannel(NULL, chanPtr, 1)) {
	    mask &= ~TCL_WRITABLE;
	}
    }

    /*
     * Add this invocation to the list of recursive invocations of
     * ChannelHandlerEventProc.
     */

} "ready line1 line2 {done\n}"
test io-53.4 {CopyData: background write overflow} {stdio unix openpipe fileevent fcopy} {
    set big bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb\n
    variable x
    for {set x 0} {$x < 12} {incr x} {
	append big $big
    }
#    file delete $path(test1)
    file delete $path(pipe)
    set f1 [open $path(pipe) w]
    puts $f1 {
	puts ready
	fcopy stdin stdout -command { set x }
	vwait x
#	set f [open $path(test1) w]
#	fconfigure $f -translation lf
#	puts $f "done"
#	close $f
    }
    close $f1
    set f1 [open "|[list [interpreter] $path(pipe)]" r+]
    set result [gets $f1]
    fconfigure $f1 -blocking 0
    puts $f1 $big
    flush $f1
    after 500
    set result ""
    fileevent $f1 read [namespace code {
	append result [read $f1 1024]
	if {[string length $result] >= [string length $big]} {
	    set x done
	}
    }]

{
    PipeState *psPtr = (PipeState *) instanceData;
    int newmask;

    if (psPtr->inFile) {
	newmask = mask & (TCL_READABLE | TCL_EXCEPTION);
	if (newmask) {
	    Tcl_CreateFileHandler(GetFd(psPtr->inFile), mask,
		    (Tcl_FileProc *) Tcl_NotifyChannel,
		    (ClientData) psPtr->channel);
	} else {
	    Tcl_DeleteFileHandler(GetFd(psPtr->inFile));
	}
    }
    if (psPtr->outFile) {
	newmask = mask & (TCL_WRITABLE | TCL_EXCEPTION);
	if (newmask) {
	    Tcl_CreateFileHandler(GetFd(psPtr->outFile), mask,
		    (Tcl_FileProc *) Tcl_NotifyChannel,
		    (ClientData) psPtr->channel);
	} else {
	    Tcl_DeleteFileHandler(GetFd(psPtr->outFile));
	}
    }
}

     * Be sure to disable event servicing so we are truly modal.
     */

    oldMode = Tcl_SetServiceMode(TCL_SERVICE_NONE);

    /*
     * Reset WSAAsyncSelect so we have a fresh set of events pending.
     * Don't do that if we are waiting for a connect as we may miss
     * a connect (bug 336441ed59).
     */

    if ( 0 == (events & FD_CONNECT) ) {
        SendMessage(tsdPtr->hwnd, SOCKET_SELECT, (WPARAM) UNSELECT,
                (LPARAM) infoPtr);
    
        SendMessage(tsdPtr->hwnd, SOCKET_SELECT, (WPARAM) SELECT,
                (LPARAM) infoPtr);
    }

    while (1) {
	if (infoPtr->lastError) {
	    *errorCodePtr = infoPtr->lastError;
	    result = 0;
	    break;
	} else if (infoPtr->readyEvents & events) {

	}
	SetEvent(tsdPtr->socketListLock);
	break;

    case SOCKET_SELECT:
	infoPtr = (SocketInfo *) lParam;
	if (wParam == SELECT) {
            /*
             * Start notification by windows messages on socket events
             */

	    WSAAsyncSelect(infoPtr->socket, hwnd,
		    SOCKET_MESSAGE, infoPtr->selectEvents);
	} else {
	    /*
	     * UNSELECT: Clear the selection mask
	     */

	    WSAAsyncSelect(infoPtr->socket, hwnd, 0, 0);
	}
	break;

    case SOCKET_TERMINATE: