John Hornick [MSFT] wrote:
Thanks very much, John. I spent a few hours looking at the DDK last
night, and think I get the general idea. What's missing in my
understanding is how PC-Duo (and PC Anywhere, too, I believe) use a
mirror driver to optimize the transporting of window drawing to a
remote window. Was that a fairly trivial tweak, or was it more like
hundreds of man hours of R & D to get their end result of extremely
high performance?

For what it's worth, we're developing this remote window capture
capability for use within a product in a very narrow market segment,
so we're not really competitors to PC-Duo or PC Anywhere.

Thanks for any insights we can get here.

Dave Briccetti

Hi, Dave

The basic trick what UNC systems use is a fact that mirror driver
can intercept all rendering to the screen and thus it knows
the exact update region each time. This may help to lower the
bandwidth great compared to full-screen updates.
But it still will be rather high.
I have some experience with mirror drivers and can say
that mirror driver shows its real power when we use it not
simply to catch and post the updated regions, but to
intercept, transfer and replay the rendering commands themselves.
This way we enjoy numerous advantages, including bitmap and font
caching, rendering operations performed on client (resultant bitmaps
are not posted, only source ones if any), etc.
Yes, this second approach requires substantial R&D.

--------------------
Lev Kazarkin
Mirror drivers. Consulting and custom development.