emacs-x11: new clipboard size limitation?

Jon TURNEY jon.turney@dronecode.org.uk
Mon Dec 2 14:56:00 GMT 2013

On 02/12/2013 14:17, Corinna Vinschen wrote:
> On Dec  2 13:11, Jon TURNEY wrote:
>> On 02/12/2013 12:13, Markus Hoenicka wrote:
>>> I'm running emacs-x11 24.3.1 on
>>> CYGWIN_NT-5.1 sbhc123 1.7.25(0.270/5/3) 2013-08-31 20:39 i686 Cygwin
>>> I used to be able to copy text from Emacs to Windows applications through the
>>> clipboard without practical size limitations. However, since my last Cygwin
>>> upgrade (which updated both Emacs and cygwin1.dll to the versions mentioned
>>> above) the clipboard seems to be limited in size. All I do is the following:
>>> - open a file containing ASCII text, amounting to like three printed pages of
>>> text
>>> - at the beginning of the buffer, press Ctrl-Space
>>> - at the end of the buffer, press M-w
>>> - switch to a Windows application (any that can handle unformatted text will
>>> do, use e.g. LibreOffice Writer)
>>> - insert the text using Ctrl-v
>>> stderr shows the following messages:
>>> winClipboardWindowProc - timed out waiting for WIN_XEVENTS_NOTIFY_DATA
>>> winClipboardFlushXEvents - SelectionNotify - X*TextPropertyToTextList
>>> returned: XConverterNotFound
>>> winClipboardWindowProc - timed out waiting for WIN_XEVENTS_NOTIFY_TARGETS
>>> On the receiving end, the message reads something like:
>>> "Clipboard does not contain specified formatted data"
>>> Trial and error tells me that I can copy 6104 characters without problems.
>>> Trying to copy 6105 or more characters triggers the error. I'll try and see if
>>> this number is constant across reboots. Copying within Emacs, i.e. by yanking
>>> the text into a different buffer, is not affected. The problem persists if I
>>> start Emacs using the -q flag.
>> This looks like the same issue as reported in [1], so you might like to try
>> the snapshot from [2] and see if it improves things for you?
>> What you write does seem to support the theory that this is a regression in
>> select() in the cygwin DLL.  It might be useful if you could say what version
>> of the cygwin DLL you had when it was working correctly before you upgraded.
>> [1] http://cygwin.com/ml/cygwin-xfree/2013-10/msg00031.html
>> [2] http://cygwin.com/ml/cygwin-xfree/2013-11/msg00012.html
> Are you sure this is a select problem?  If so, can you create an STC,
> perhaps?

"Only a madman is absolutely sure".  I'm afraid the best test case I have a
the moment is:

Install xorg-server-debuginfo
Start XWin -noclipboard -multiwindow
Start xwinclip under gdb, and place a breakpoint at wndproc.c:133, and run it
Start emacs-x11, open the Shakespeare text from [1] in a buffer
Open notepad
Copy and paste the text from the emacs buffer into notepad
The breakpoint is hit.  Notice that select() has returned 0, the read ready
fd_set is empty and the timeout hasn't expired. I claim that the read ready
fd_set should indicate that the X connection socket is ready.

Volunteer Cygwin/X X Server maintainer

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