Fix to stop xwinclip from clobbering remote clipboard

[Harold L Hunt II]

Øyvind,

Øyvind Harboe wrote:

> I'm going out on a limb here, as my experience with xfree86 is extremely
> limited. Perhaps there is an option to achieve what I'm suggesting here.
> 
> Oh well! :-)
> 
> xwinclip is clobbering the clipboard when I work w/e.g. OpenOffice:
> 
> - If I copy and paste a spreadsheet cell while xwinclip is running, only
> the value is copied.
> - If xwinclip is not running, I can copy and paste formulas without
> problems.

Yes, that is a valid problem.

> AFAICT, xwinclip clobbers the remote clipboard by doing a "conversion
> round-trip": remote clipboard->windows clipboard->remote clipboard. Such
> round trip conversions are inheritely lossy and should be avoided.
> 
> After examining the source code(see below), I've come up with the
> following "scheme" for a fix:
> 
> - register a new dummy windows clipboard data type, e.g. named
> "REMOTEDATA".
> - whenever xwinclip updates the Windows clipboard, it also invokes
> SetClipboardData(REMOTEDATA, dummyval).
> - whenever xwinclip executes a paste from the Windows clipboard to e.g.
> an OpenOffice spreadsheet not running under Windows, xwinclip first
> checks if REMOTEDATA is present in the Windows clipboard. If the flag is
> present, xwinclip effectively needs to do nothing because the remote
> clipboard already contains the correct data.

No, that scheme does not work.

The problem is that we have to grab ownership of the X clipboard each 
time that either the X clipboard or the Windows clipboard changes.  So, 
we can't even attempt your idea because it requires that the original 
provider of the X clipboard data still be around when the request comes 
to paste that data; by grabbing ownership of the clipboard we tell that 
X app to dump the data to us in a single format.  This essentially means 
that OpenOffice no longer knows that it put in the clipboard; we have to 
tell it.

Your idea is part of what we will do when we use the XFIXES extension to 
monitor changes to the clipboard instead of stealing ownership of the 
clipboar each time another application changes it.  I wrote the code a 
while back to work with the XFIXES extension but it was never completely 
finished.  Maybe I will get to it soon.

Harold