time stamp appearing, then disappearing when pointed at, near the foot of the messages area

[grahamperrin]

Description

If a message is at or near the foot of the messages area, then its time stamp may disappear when pointed at.

Steps to reproduce

1. https://matrix.to/#/!GiBpZSGcdzTfkNXmer:matrix.org/$1493418047567086nulfy:matrix.org
2. view in browser
3. scroll up until an earlier message is at or near the foot of the messages area
4. point at the centre of the messages area
5. move the pointer rapidly down towards the time stamp
6. observe appearance of the time stamp

Expected

• when the pointer arrives at the time stamp, the time stamp should persist

Actual result

• at the time of (or a split-second before) arrival of the pointer at the time stamp area, the stamp disappears.

Making this reproducible, for issue reporting purposes, does feel contrived. However the experiences of the bug were not contrived. I observed the bug:

• almost immediately after beginning to test the recent enhancement for a jump should be followed by orientation; show the day, date and time element-meta#1230
• then a few more incidents.

A key to making the bug reproducible may be rapidity of movement of the pointer.

Log: not sent

Screenshots

/develop/

Worked around:

/app/

Worked around:

Version information

Platform: web

Firefox 53.0 (64-bit)

URLs:

https://riot.im/develop/#/room/#mozilla_#firefox:matrix.org

• homeserver is https://matrix.org
• identity server is https://vector.im
• matrix-react-sdk version: 19482d7
• riot-web version: 67efb8b-react-19482d751d82-js-acd7f15c8376
• olm version: v2.2.1

Also at https://riot.im/app/#/room/#mozilla_#firefox:matrix.org

$ about

===================
General information
===================

boot environment now (N) … 12.0-CURRENT-up-20170330_080908 NR 2017-03-30
       after restart (R) … 12.0-CURRENT-up-20170330_080908 NR 2017-03-30
boot loader …………………………………… BSD
            type ……………………… EFI
CPU ………………………………………………………… Intel(R) Core(TM) i7-5600U CPU @ 2.60GHz
    number of cores ……………… 4
host ……………………………………………………… momh167-gjp4-hpelitebook850g2-trueos.university.brighton.ac.uk
memory ………………………………………………… 16384 MB available, 4135 MB free
OS git branch ……………………………………………………………………………………… drm-next
OS git revision ………………………………………………………………………………… a009033ff
OS kernel build time ………………………………………………………… Wed 2017 Mar 29 20:13:33 UTC
OS kernel identity …………………………………………… (uname -i) GENERIC
OS platform (architecture) ……………………… (uname -m) amd64
OS release level ………………………………………………… (uname -r) 12.0-CURRENT
OS version and patch level …… (freebsd-version) 12.0-CURRENT
TrueOS package set ………………… CUSTOM
TrueOS version …………………………… TrueOS-Desktop-201703201429
uptime ………………………………………………… 11:01
user  …………………………………………………… grahamperrin

More (TrueOS Desktop):

    desktop environment …… KDE
    sound card driver ………… pcm1: <Realtek (0x0280) (Analog 2.0+HP/2.0)> on hdaa1  (1p:2v/1r:1v) default
    wireless driver ……………… iwm0
    X11 drivers ………………………… intel_drv.so 

$ 

[lampholder]

On the occasions when the timestamp hasn't appeared, it looks like the line highlight hasn't appeared either. The line highlight is just plain-old CSS :hover on the mx_EventTile I think (and hence unlikely to go wrong) so there's an outside chance of this being firefox being a tiny bit glitchy :\

I wasn't able to reproduce (even moving my mouse as fast as I could) on chrome or ff on mac.

[grahamperrin]

I set aside a screen recording 2017-04-29 00-16-49.mp4 but refrained from sharing (wishing to not publicly disclose the chat at the time of the recording – nothing sensitive, AFAICT, but I like to not disclose without the explicit permission of participants). A frame from that recording:

Screenshots from a more recent example:

More exaggerated:

It 'feels' like an edge case; would you like to demote from p3 to p5?

[grahamperrin]

… wishing to not publicly disclose the chat …

Scrub that. For the room that was recorded, the topic (not visible, a separate issue) draws attention to a public log, so here's the screen recording:

2017-04-29 00-16-49.mp4.tar.gz

[lampholder]

It certainly does seem very edge casey - I can't reproduce running ff 53 on my ubuntu machine. But it is obviously a real glitch that, so I think it's okay to leave it p3. Certainly something weird is going on :P