DomainKey-Signature: a=rsa-sha1; c=nofws; d=sourceware.org; h=list-id
	:list-unsubscribe:list-subscribe:list-archive:list-post
	:list-help:sender:date:from:reply-to:message-id:to:subject
	:in-reply-to:references:mime-version:content-type
	:content-transfer-encoding; q=dns; s=default; b=sBRDiIRdmavHxwIa
	kz+/1YQ6nI6+3dWSByYap+jHfUcQB87b2nVfpdrf0hQ2shOAUgZk+TolKitubW2z
	w+6grqukCgHMTN1mHv/bxhgG99WFsRtd/ukpxvS5iBtOUmZtoDazAHgpfStGdm4a
	0w+22HWCUwWg1/74aRHTUMpNHzI=
Mailing-List: contact cygwin-help@cygwin.com; run by ezmlm
Sender: cygwin-owner@cygwin.com
Mail-Followup-To: cygwin@cygwin.com
Date: Tue, 15 Sep 2015 06:54:25 +0300
From: Andrey Repin <anrdaemon@yandex.ru>
Reply-To: cygwin@cygwin.com
Message-ID: <1548943127.20150915065425@yandex.ru>
To: Warren Young <wyml@etr-usa.com>, cygwin@cygwin.com
Subject: Re: Cygwin terminal weirdness
In-Reply-To: <7AF4498C-6FE4-4541-9CAD-03EC3D867D72@etr-usa.com>
References: <91152470.20150913213611@yandex.ru> <7AF4498C-6FE4-4541-9CAD-03EC3D867D72@etr-usa.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 8bit

Greetings, Warren Young!

>> Call "man" on a sufficiently long topic. man bash would be quite sufficient.
>> Or just `less` a long enough text.
>> Hold down "End" key.
>> The screen buffer will jump and tear repeatedly, until you release the key.

> That sounds like a video card performance issue, not a Cygwin, mintty, or less issue.

I can't believe it is a gfx performance issue, as I can't reproduce it with
PuTTY in the same situation.
I.e.
native console/local less = jumping and tearing.
mintty/local less = jumping and tearing.
native console/ssh+less = jumping and tearing.
mintty/ssh+less = jumping and tearing.
putty+less = no jumping, no tearing.

Let's try a different approach. The video id is ne3VmLZmD9g on a well-known
tube hosting service.

> I just tried it here on a VM hosted on a box with an NVIDIA GeForce GTX
> 680MX GPU, and all I saw was normal redrawing, with scarcely any tearing. 
> That chip is about 3 years old, which probably still outperforms any current CPU-integrated GPU.

> There are some small mitigations that might help.

> One would be to convince the maintainers of less to be smarter about
> repainting the whole screen when it isn’t necessary.  But given that they
> haven’t fixed the horizontal scrolling bug in the ~20 years I’ve been using
> it, I wouldn’t hold out hope on that front.

Well, let's say, this is unconvincing.

> Another would be to make mintty double-buffer its screen, if it doesn’t
> already.  That won’t help with the clear-screen call less is currently
> making, but it might reduce the tearing effect.

> The same thing is happening with something like “ls -lR /“.  The only
> difference is that you can easily see what’s going on in the “man bash”
> case, since the content remains static.

> Another way to see it is “vim /etc/sshd_config”, then hold down Ctrl-L.

I'm not familiar with vi/m, so I'll just trust you on the matter.


-- 
With best regards,
Andrey Repin
Tuesday, September 15, 2015 06:47:19

Sorry for my terrible english...