510158 - Mouse jumps up 50 or so pixels when held stationary over one LI tag, then moved 1 pixel

Status: RESOLVED INCOMPLETE

(Firefox :: General, defect)

Description

[Jeremy Warne]

User-Agent:       Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.5; en-US; rv:1.9.1.2) Gecko/20090729 Firefox/3.5.2
Build Identifier: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.5; en-US; rv:1.9.1.2) Gecko/20090729 Firefox/3.5.2

When you mouse over any LI inside a UL tag, leave the mouse for a second, then move the mouse 1 pixel, the browser acts as if the mouse had been pointing at a space directly above the current location of the pointer, about 50 pixels up. Visually the pointer does not move -- however, the tooltip and any other mouseover events (javascript etc) will fire as if the pointer was 50 pixels above its current location. This only happens if you move the mouse 1 pixel after it has come to rest on an LI element. If you move more than one pixel, the second pixel's movement will return focus to the correct location.

Reproducible: Always

Steps to Reproduce:
1. Use the following test HTML:
<ul>			
<li><a title="test 1" href="#">Test text test text 1</a></li>
<li><a title="test 2" href="#">Test text test text 1</a></li>
<li><a title="test 3" href="#">Test text test text 1</a></li>
<li><a title="test 4" href="#">Test text test text 1</a></li>
<li><a title="test 5" href="#">Test text test text 1</a></li>
<li><a title="test 6" href="#">Test text test text 1</a></li>
</ul>

2. Mouse over the last item in the list. Allow the mouse to come to rest. A tooltip should appear saying "Test 6"
3. Move the mouse one pixel only, in any direction; after a few seconds the tooltip for "Test 2" will appear, as if you'd held the mouse over the second item in the list.
Actual Results:  
As above

Expected Results:  
The expected behaviour would be that when you move the mouse 1 pixel, the normal tooltip would disappear and appear again with the same text as before, as you're still mousing over the same element.

Comment 1

[Jeremy Warne]

This is especially annoying in Javascript menus when you have an onMouseOver event which animates a page element -- if you come to rest, then move the mouse slowly, a menu several items up will pop out unexpectedly.

Comment 2

[Tyler Downer [He/Him]]

Reporter, are you still seeing this issue with Firefox 3.6.12 or later in safe mode? If not, please close. These links can help you in your testing.
http://support.mozilla.com/kb/Safe+Mode
http://support.mozilla.com/kb/Managing+profiles
Also, please consider using the most recent Firefox 4 beta build, your bug may be resolved there.

Comment 3

[Tyler Downer [He/Him]]

No reply, INCOMPLETE. Please retest with Firefox 3.6.13 or later and a new profile (http://support.mozilla.com/kb/Managing+profiles). If you continue to see this issue with the newest firefox and a new profile, then please comment on this bug.