1262947 - Mouseover has a gap between 2 divs

Status: RESOLVED WONTFIX

(Core :: Layout: Floats, defect, P4)

Description

[Peter Möller]

User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Firefox/45.0
Build ID: 2016031600

Steps to reproduce:

- call http://mieterhilfeverein.de/mietrecht-politik
- move the mouse over to the menu item "Mietrecht&Politik"
  => a sub menu below will open, with 1px of (optical) distance
- move mouse vertical into the submenu region


Actual results:

In about 50% of tries the submenu will close, before the mouse is entering the region of the submenu




Expected results:

in 100% of tries the submenu should stay visible.

Hints:
- FF has 45.0.1, seen in Windows 32bit and opensuse 13.1 64bit
- Chrome (win, linux) doesn't show this effect
- I'm not sure, what causes this behaviour, maybe its just a "round up/down" problem, but it is pretty nasty

Comment 1

[Loic]

I can't reproduce it with FF45 on Win 7 64-bits.

Comment 2

[Loic]

Forget my previous comment, I can reproduce it at resolution 100% when I hover the menu fastly 10 times then I try to scroll down the submenu.

Comment 3

[Loic]

Firefox 8 has the bug too, old issue.

Comment 4

[srakitnican]

I am able to reproduce 80% of tries, but on the arrow pointing to main menu stays 100% of tries. It helps to reproduce if mouse cursor is moved very slowly between menus transition. If moved fast it disappears only like 20% of tries.

Setting margin from the following to 1px makes the problem go away, but it also moves sub-menu closer to main menu.

http://mieterhilfeverein.de/templates/mhv/css/template.css line 7237

.navigation .nav-child {
	position: absolute;
	top: 95%;
	left: 0;
	z-index: 1000;
	display: none;
	float: left;
	min-width: 160px;
	padding: 5px 0;
	margin: 2px 0 0;

Firefox 45.0.1 x86_64 Linux

Comment 5

[Peter Möller]

@srakitnican: its true, reducing margin to 1px helps to get rid of the effect. Dunno, i could accept this change for the website, but others might encounter the same problem.

Comment 6

[srakitnican]

I think other pages may encounter it, also. I found the same happening on imgur.com when mousing over menu that appears from logged in username on top right.

Comment 7

[Ciprian Muresan [:cmuresan], Ecosystem QA]

Attachment: ReducedTestcase.7z

Hi,

I have managed to reproduce the issue on the latest Firefox (45.0.2, Build ID 20160407164938) and the latest Nightly (48.0a1, Build ID 20160414030247) on Windows 10, Ubuntu 15.10 and Mac OS X 10.10. I've attached a reduced testcase where the issue is present. I can also confirm what was said in Comment 4.
 
Thanks,
Cipri

Comment 8

[Loic]

Attachment: index.html (testcase)

Comment 9

[Peter Möller]

Tried it again with ff78 and don't see the effect any more, using testcase attachment
Closing it