Re: Attacking round trips

[Keith Packard <keithp keithp com>]

Around 9 o'clock on Jul 5, Soeren Sandmann wrote:

> There are 67 calls to gdk_get_pointer() in gtk+. Would it be worthwhile
> to turn off the hint mask and doing motion compression instead?

Quite likely -- motion hints never really worked as well as we'd hoped 
because they required an additional round trip.  It would be equivalent to 
just do XSync and motion compression; motion events just aren't a 
significant bandwidth problem.

One thing to consider is that each motion event will be in a separate 
packet (Nagle is turned off on X connections), and the mouse delivers 100 
positions/sec (approximately), so waving the mouse will tend to add quite 
a few packets to the system.  I don't think this is a serious problem for 
most environments, but we might consider whether an X extension would be 
appropriate to throttle motion events somehow without requiring round 
trips like motion hint does.

-keith