[PATCH v4] Cygwin: pty: Fix handling of data after CSI6n response

[Takashi Yano]

On Sat, 7 Mar 2026 12:58:00 +0100 (CET)
Johannes Schindelin wrote:
> Hi Takashi,
> 
> On Fri, 6 Mar 2026, Takashi Yano wrote:
> 
> > Previously, CSI6n was not handled correctly if the some sequences
> > are appended after the response for CSI6n. Especially, if the
> > appended sequence is a ESC sequence, which is longer than the
> > expected maximum length of the CSI6n response, the sequence will
> > not be written atomically.
> > 
> > Moreover, when the terminal's CSI 6n response and subsequent data
> > (e.g. keystrokes) arrive in the same write buffer, master::write()
> > processes all of it inside the pcon_start loop and returns early.
> > Bytes after the 'R' terminator go through per-byte line_edit() in
> > that loop instead of falling through to the `nat` pipe fast path
> > or the normal bulk `line_edit()` call. Due to this behaviour,
> > the chance of code conversion to the terminal code page for the
> > subsequent data in `to_be_read_from_nat_pipe()` case, will be lost.
> > 
> > Fix this by breaking out of the loop when 'R' is found and letting
> > the remaining data fall through to the normal write paths, which
> > are now reachable because `pcon_start` has been cleared.
> > 
> > Fixes: f20641789427 ("Cygwin: pty: Reduce unecessary input transfer.")
> > Signed-off-by: Takashi Yano <takashi.yano@nifty.ne.jp>
> > Co-authored-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
> > Reviewed-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
> 
> Thank you! This version looks good to me!

Thanks! Pushed.

-- 
Takashi Yano <takashi.yano@nifty.ne.jp>