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Subject: Re: Cygwin terminal weirdness
From: Warren Young <wyml@etr-usa.com>
In-Reply-To: <91152470.20150913213611@yandex.ru>
Date: Mon, 14 Sep 2015 14:09:18 -0600
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References: <91152470.20150913213611@yandex.ru>
To: cygwin@cygwin.com
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On Sep 13, 2015, at 12:36 PM, Andrey Repin <anrdaemon@yandex.ru> wrote:
> 
> 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 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.

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.
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