Hi Alexandre,

* Alexandre Pineau wrote (2004-07-19 20:40):
>Thorsten Haude <email address hidden> wrote:
>> * Alexandre Pineau wrote (2004-07-18 22:37):
>> >Thorsten Haude <email address hidden> wrote:
>> >> What setup do you use on the machine where you could not reproduce it?
>> >
>> >With Sarge's Nedit, I can reproduce it under KDE, but not under xfce3
>> >(ctrl C Ctrl V from Firefox to Abiword) 
>> 
>> Did you try the trick I mentioned in the Lesstif bug report? Please
>> do, it might help to fix the bug.
>
>In your Lesstif bug report, you say :
>
>>1. Put text A in the clipboard (verify with xclipboard)
>>2. Open DDD and NEdit
>>3. Copy text B in DDD
>>4. Paste the clipboard to NEdit both *before* and *after*
>>the five second timeout is up (xclipboard dialog).
>
>>What I see here: The first paste inserts text B, the second
>>paste inserts text A. My blind guess is that B is stored
>>internally in Lesstif (it's not accessible to other apps)
>>and overwritten with the clipboard once the timeout is up.
>
>I can reproduce what you describe, but only if xclipboard is open.
>Strange, not?

I think it works like this: The clipboard (CLIPBOARD) does not work
very much different than the primary and secondary selection (PRIMARY
and SECONDARY). No data is actually copied on Copy, the app only
reports to some level of X11 that it has data other apps might find
useful. It has to name a callback function which is supposed to be
called once the data is actually requested by another app. This is
done to avoid expensive transmissions between client and server (which
may be on different continents).

Motif covers this with a number of convenience functions which makes
it a bit easier for the application to use CLIPBOARD (XmClipboardCopy
and friends). There is no need for the callback function, at least
this is how it is explained in my book, how it is done in NEdit and
how it actually works with Open Motif.


Enter xclipboard: This app *does* actually request the data put in
CLIPBOARD. It does that by means of a second callback function which
informs it that it no longer owns CLIPBOARD. Little xclipboard
immediately request the new content of CLIPBOARD from NEdit, and again
claims that it owns CLIPBOARD.

The request fails for some reason in our case, the transfer times out
and xclipboard gets the result XT_CONVERT_FAIL, which brings forth the
error message. CLIPBOARD is immediately reclaimed by xclipboard (still
with the old value) and NEdit happily requests and pastes *that* (A in
the above example). Without xclipboard, this would not happen, and
CLIPBOARD would remain claimed by NEdit.


If xclipboard does not run and the content of CLIPBOARD is only
requested by NEdit and DDD, everything works fine. As soon as
non-Lesstif apps enter the play, things get ugly because these apps do
similar things as xclipboard does, only without noticing the user of
problems.

The original description is matching my xclipboard story exactly:
1. Put text A in the clipboard (by copying from Konqueror into Emacs)
2. Start NEdit
3. Copy text B in Lesstif app
4a. Paste the clipboard to NEdit before five seconds are up.
4a. Paste the clipboard to NEdit after five seconds are up.


OTOH, all this may be completely wrong.


Thorsten
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