Re: [PATCH v3] Cygwin: clipboard: Add workaround for ERROR_CLIPBOARD_NOT_OPEN

On Fri, 12 Jun 2026 22:55:05 -0700
Mark Geisert wrote:
> Hi Takashi,
> 
> On 6/12/2026 7:54 PM, Takashi Yano wrote:
> > SetClipboardData() and GetClipboardData() occasionally fail with
> > ERROR_CLIPBOARD_NOT_OPEN, even though OpenClipboard() succeeded if
> > NULL HWND is used. Retry until GetClipboardData() does not return
> > ERROR_CLIPBOARD_NOT_OPEN.
> > 
> > Addresses: https://cygwin.com/pipermail/cygwin/2026-February/259438.html
> > Signed-off-by: Takashi Yano <[email protected]>
> > Reviewed-by: Mark Geisert <[email protected]>
> > ---
> > v2: Handle ERROR_NOT_FOUND case. Call CloseClipboard() in the loop.
> > v3: Change the timing of CloseClipboard().
> 
> Thanks for catching this ^^^ I was just about to mention it myself...
> 
> >   winsup/cygwin/fhandler/clipboard.cc | 19 +++++++++++++++++--
> >   1 file changed, 17 insertions(+), 2 deletions(-)
> > 
> > diff --git a/winsup/cygwin/fhandler/clipboard.cc b/winsup/cygwin/fhandler/clipboard.cc
> > index 12691c7c1..1273863f4 100644
> > --- a/winsup/cygwin/fhandler/clipboard.cc
> > +++ b/winsup/cygwin/fhandler/clipboard.cc
> > @@ -25,11 +25,26 @@ details. */
> >   static inline bool
> >   open_clipboard ()
> >   {
> > -  const int max_retry = 10;
> > +  const int max_retry = 20;
> >     for (int i = 0; i < max_retry; i++)
> >       {
> > +      /* No appropriate HWND exists here. */
> >         if (OpenClipboard (NULL))
> > -	return true;
> > +	{
> > +	  /* SetClipboardData() and GetClipboardData() occasionally
> > +	     fail with ERROR_CLIPBOARD_NOT_OPEN, even though
> > +	     OpenClipboard() succeeded if NULL HWND is used.
> > +	     Retry until GetClipboardData() does not return
> > +	     ERROR_CLIPBOARD_NOT_OPEN. */
> > +	  if (GetClipboardData (CF_UNICODETEXT))
> > +	    return true;
> > +	  DWORD err = GetLastError ();
> 
> Given the ambiguity of "ERROR_NOT_FOUND" I would add a one-line comment 
> here saying ERROR_NOT_FOUND means GetClipboardData() couldn't find 
> CF_UNICODETEXT data, but it would return data if you ask for the correct 
> format. This latter case means the clipboard is indeed open. (Or some 
> briefer way of saying this complicated case.)
> 
> Hmm. Maybe more than one line for that comment. With that, patch is GTG.

Thanks! Pushed.

-- 
Takashi Yano <[email protected]>