[Xcb] Is there any way to intercept or generate protocol to an in-memory buffer?

Clemens Eisserer linuxhippy at gmail.com
Sat Dec 30 14:40:02 UTC 2017

Hi Bart,

> I don't remember the details of how we did the sync in XCB back when: we did
> something very like what you are doing, but the details are a bit tricky to
> get right.  In particular, XCB will only send an input focus request when no
> request (not just input focus) has received a reply in the last 64K
> requests. So...yeah. It's been literally a decade since I looked at this
> stuff, but I *think* you should be able to dig the last-sync count out of
> XCB and just work from that: probably can just use the XCB code or at least
> algorithm to tell you when to sync.

Thanks for taking a look at the approach - actually it was just a
simple bug on my side ;)
Overall things look good now - I am able to reduce the number of
XPutImage requests depending on the workload by about 4-20x, with no
regressions running code which is not the target of the optimization.

So the tinkering I did with socket handoff 8-9 years ago now turns
into something useful after all :)

Thanks and best regards, Clemens

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