Re: experiments with clipboards and clipboard managers

[Ben Pfaff]

John Darrington <address@hidden> writes:

> On Mon, Oct 15, 2012 at 08:52:03PM -0700, Ben Pfaff wrote:
>      I did a little bit of research tonight after thinking about our
>      IRC conversation about when it takes a long time to compose
>      selection data for a clipboard response.  I modified the function
>      that responds to a clipboard request to printf a message, and
>      then tried a few clipboard copies with two different clipboard
>      managers running (Parcellite and Diodon) and with no clipboard
>      manager running.
>      
>      Parcellite's behavior surprised me.  Twice a second, it requests
>      a new copy of the primary selection from whatever app owns it.
>      If an app has a big selection, it essentially DOSes the machine.
>      
>      Diodon seems a little better.  It appeared to request the
>      selection three times (three formats? didn't check) and then
>      stops.
>      
>      Without a clipboard manager, there's no problem.
>
> None of the above surprises me.  Clipboard "managers" cause problems 
> as you have discovered.

Oops, I made a small mistake above: where I wrote "primary
selection", I should have written "clipboard".  But the behavior
would be the same for the primary selection if the clipboard
manager is configured to monitor it too (this does not seem to be
the default).

The reason that considering clipboard managers seems interesting
is because some desktop environments include one by default.  I
think that Ubuntu does, for example.

>      Gnumeric doesn't handle large copy/cut/paste particularly well
>      either.  It's easy to induce long pauses (seconds, maybe tens of
>      seconds?) with a few hundred thousand cells.
>
> Does this happen going in both directions, or only in one?  And is 
> the bottleneck in the Gnumeric side or the Psppire side?

This was for copy and pasting large sheets from Gnumeric to
Gnumeric, without PSPPIRE involved.

> At the end of the day, I would never encourage anyone to make large
> cut and pastes.  Not only because of the performance issue, but also
> because it is so easy to inadvertently and unwittingly select the 
> wrong cells - leading to data getting dropped or duplicated without
> anyone realising it.
>
> The clipboards (both PRIMARY and CLIPBOARD)  are IMO a convenience
> feature designed to be used for quick transfer of small amounts of
> data between applications.  The clipboards need to be able to 
> generate text and html so that they can be pasted to spreadsheets
> and to text editors.  The code in master does this quite well I 
> think, so can probably be reused for the psppsheet branch.

I have already reused it.  The clipboard is now implemented on
psppsheet, using this code, since the weekend.  I haven't
implemented the primary selection yet though.