[Emacs-vr-mode-devel] Re: vr-cmd-make-changes

[Patrik J. <pa...@uc...>]

>I see.
>
>I had misunderstood the purpose of the buffer change notification gizmo. I
>thought it was meant to keep Emacs' and DNS' versions of the buffer in sync so
>that you could support "scratch that/correct that". But from what you say, it
>sounds like all vr.el is interested in is is keeping the visible regions in
>sync so that we can support "Select XYZ".
>
>This raises a new question for me. Why do we bother with a complex (and
>probably very fragile) buffer change notification approach instead of sending
>the whole visible region at the beginning of every utterance? Unless you 
>have a
>very slow connection, sending the whole visible region (note: just the visible
>region, not the whole buffer) can't be that expensive.

that's a VERY good question!  This is just the way VR mode is made, and I 
don't know why Barry made that decision.  It might have been that he simply 
wasn't aware of the other possibilities.  I haven't thought about it, my 
changes to VR mode has been evolutionary, not revolutionary... :-)

As for the communication overhead, I don't really know.  I HAVE noticed a 
significant delay when doing the full buffer resynchronization over a 
tunneled secure shell link to external hosts, but I don't remember how 
large those buffers were.  I also have never tried running it over for 
example a DSL link, which I suspect will be significantly slower.

In my mind, the responsiveness of the recognition is one of the most 
important factors affecting how usable it is, so I'd prefer erring on the 
side of caution.  However, this is easily testable!  Simply add (setq 
vr-resynchronize t) at the beginning of get-buffer-info, and a full buffer 
resynchronization will be performed for every utterance.  If you try this 
on a buffer which just about fills your window you should get a pretty good 
estimate of the communications delay.

/Patrik


============================================================
Patrik Jonsson                                  (831) 459-3809
Department of Astronomy & Astrophysics
University of California, Santa Cruz, CA 95064

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