Hi Mark, On Wed, 25 Feb 2026 01:47:04 -0800 Mark Geisert via Cygwin <[email protected]> wrote: > On 2/23/2026 5:36 PM, Takashi Yano via Cygwin wrote: > > Hi, > > > > I encountered a clipboard issue common to cygwin. > > > > Affected components: > > /dev/clipboard, putclip/getclip, mintty > > > > The issue: > > If the clipbard is opened by `OpenClipboard(NULL)`, occasionally > > SetClipboardData() and GetClipboardData() fails with > > ERROR_CLIPBOARD_NOT_OPEN. > > > > When UltraVNC Viewer (https://uvnc.com/) is opened, this issue > > happens with a very high probability (> ~90%). > > > > $ echo AAAA > /dev/clipboard > > echo: write error: Permission denied > > > > On mintty, text selection by mouse and clicking center button > > fails at the first attempt. > > > > For putlclip/getclip, the following command outputs nothing > > in a few attempts. ("ABCD" is lost.) > > $ echo ABCD |putclip; for a in `seq 100`; do getclip |putclip; done; getclip > > > > $ > > > > > > Solutions: > > This can be solved by passing non-zero HWND to OpenClipboard(). > > Therefore, as for mintty, the following patch is ok I think. > > diff --git a/src/winclip.c b/src/winclip.c > > index 12c54525..a7cbe365 100644 > > --- a/src/winclip.c > > +++ b/src/winclip.c > > @@ -1324,7 +1324,7 @@ static void > > do_win_paste(bool do_path) > > { > > //printf("OpenClipboard win_paste\n"); > > - if (!OpenClipboard(null)) > > + if (!OpenClipboard(wnd)) > > return; > > > > if (cfg.input_clears_selection) > > > > However, for /dev/clipbard and {put|get}clip, there is no > > suitable HWND to pass to OpenClipboard(). Fortunately, I > > found the patch attached solves the /dev/clipboard issue. > > > > This is not smart, however it works. > > > > I think similar patch is ok for putclip/getclip. > > > > Any suggestions and comments will be appreciated. > > I did not try your mintty or UltraVNC tests but the others worked fine > for me, even when in a loop of 10,000 attempts.
In my environment, I also confirmed that a loop of 1,000 attempts worked without the issue if UltraVNC Viewer is not opened. I guess UltraVNC Viewer accesses clipboard very frequently. > IIUC you are finding OpenClipboard() returning as if it's opened the > clipboard, but a subsequent operation claims the clipboard is not open. > I'm curious if GetLastError() reports anything from this phantom open. Yeah, indeed. > As for the "not smart" patch :-) I'm leery of cpu-bound loops that might > not end for some unforeseen situation. I'd rather you make use of the > existing max_retry mechanism. Maybe with shorter Sleep()s, say 100ms, > and possibly larger retry count. > HTH, Thanks. That might be better. Current Sleep(1) is 1ms, so just increase max_retry is enough I think. -- Takashi Yano <[email protected]> -- Problem reports: https://cygwin.com/problems.html FAQ: https://cygwin.com/faq/ Documentation: https://cygwin.com/docs.html Unsubscribe info: https://cygwin.com/ml/#unsubscribe-simple
