General clipboard issue on cygwin (mintty, putclip, getclip, /dev/clipboard)

[Takashi Yano]

Hi Thomas,

On Wed, 25 Feb 2026 05:18:34 +0100
Thomas Wolff wrote:
> Am 24.02.2026 um 02:36 schrieb Takashi Yano:
> > 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.
> According to Windows docs, OpenClipboard(0) would make SetClipboardData 
> fail. There is no such statement about reading from the clipboard.
> Accordingly, mintty calls OpenClipbard(wnd) before writing to the 
> clipboard and (0) only before pasting. Also I'm not aware pasting ever 
> fails for me. But if there is a chance to fail, I'll add the (wnd) to 
> both other calls.

Thanks. That's fine.

> About the cygwin patch, could perhaps GetDesktopWindow help?

I guess, I confirmed GetDesktopWindow() normally works.
However, unfortunately, it does not work in ssh session
even though it returns non-zero HWND.

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