Hi Takashi,
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.
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.
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,
..mark
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