bug#28342: 26.0.50; (OSX) Jumpy Scrolling using Trackpad

[Alan Third <athird@googlemail.com>]

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I can replicate on ms windows using just:

(setq scroll-margin 5)
(setq scroll-preserve-screen-position 1)
(setq mouse-wheel-scroll-amount '(1))

Open a large file. Make sure you're at the start of the file

M-<

Scroll down with the mouse wheel and within a few clicks point jumps to the
middle of the screen. A few more and it jumps to the end of the file.

On 6 Sep 2017 2:15 a.m., "James Nguyen" <jamesn@fastmail.com> wrote:

The cursor jumps from within the scroll-margins to end of file and back and
forth.

Some of those settings can probably be removed but scroll-margin is
probably important.

> On Sep 5, 2017, at 1:14 PM, Charles A. Roelli <charles@aurox.ch> wrote:
>
>> Resent-From: James Nguyen <james@jojojames.com>
>> Original-Sender: "Debbugs-submit" <debbugs-submit-bounces@debbugs.gnu.org
>
>> Resent-CC: bug-gnu-emacs@gnu.org
>> Resent-Sender: help-debbugs@gnu.org
>> From: James Nguyen <james@jojojames.com>
>> Date: Sun, 03 Sep 2017 17:22:29 -0700
>> Content-Type: text/plain
>>
>>
>> Recipe:
>>
>> emacs -Q
>>
>> (setq scroll-margin 5
>>      scroll-step 1
>>      scroll-conservatively 10000
>>      scroll-preserve-screen-position 1
>>        mouse-wheel-scroll-amount '(1)
>>        mouse-wheel-progressive-speed nil
>>        mouse-wheel-follow-mouse 't)
>>
>> Open another buffer (init.el for example). Use only one window.
>> Scroll with trackpad up and down.
>> Use trackpad mouse to click past the scroll margin.
>> Try scrolling up and down with trackpad. It will jump wildly.
>
> What jumps wildly?  Does removing any of these settings stop the issue
> from occurring?

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