bug#29737: 27.0.50; pixel-scroll-mode is laggy

[Tak Kunihiro <tkk@misasa.okayama-u.ac.jp>]

>> Date: Mon, 01 Jan 2018 09:58:38 +0900 (JST)
>> Cc: eliz@gnu.org, 29737@debbugs.gnu.org, tkk@misasa.okayama-u.ac.jp
>> From: Tak Kunihiro <tkk@misasa.okayama-u.ac.jp>
>>
>> I think that on scrolling of 1000 lines, smooth scroll is not
>> necessary.  User wants smooth scrolling only for the first spin of
>> mouse wheel.
>>
>> This patch introduces a new variable `pixel-dead-time' and
>> `pixel-last-scroll-time'.  When another scroll request was delivered
>> within `pixel-dead-time', very likely user does not want smooth
>> scrolling.
>>
>> On such situation, `scroll-down' is called instead of
>> `pixel-scroll-pixel-down'.  On theory there should not be lag because
>> of smoothing.
>>
>> I tested the revised pixel-scroll-mode for a week and confirmed that
>> works good.  When `pixel-dead-time' is zero, its behavior is the same
>> as before.  I think `pixel-dead-time' 0.1 works better.
>>
>> I'm sending ChangeLog and a patch relative to the current master.
>
> There was no response, but do you think we should push this
> regardless?  (It should go to the release branch, not to master.)

I think I understood what the laggy meant.  The laggy scroll is slow
scroll with too frequent redisplay.  If my understanding is correct, I
am sure this patch fixes the laggy problem.

I think it is good to avoid the laggy situation.  Thus I think, to
push this patch to the release branch is a good idea.