307667 - :hover performance has regressed in FF 1.5b1 (MathML, float)

Status: RESOLVED WORKSFORME

(Core :: Layout, defect)

Description

[Mikko Rantalainen]

User-Agent:       Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8b4) Gecko/20050908 Firefox/1.4
Build Identifier: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8b4) Gecko/20050908 Firefox/1.4

I'm still creating smallest test case but it seems that some combinations of
float, MathML content and :hover activate some code path which performance has
greatly decreased since Firefox 1.0.x.

Reproducible: Always

Steps to Reproduce:
1. Open attached test case
2. Hover mouse cursor above the menu items on the left side of the page

Actual Results:  
Hover effect should happen immediately. It seems that Firefox is displaying the
effect as fast as possible as testing this takes 100% of CPU power. For some
reason, the page renders fine in older versions.

Expected Results:  
Hover effect should be at least as fast as in the previous releases.

This may be Linux only.
Test environment:
Mandrakelinux release 10.2 (Limited Edition 2005) for i586 (Mandriva)

X Window System Version 6.8.2
Release Date: 9 February 2005

Graphics adapter: Matrox Graphics, Inc. MGA G550 AGP
CPU: AMD Athlon(tm) XP 2800+

$ rpm -qf `which xfs`
xorg-x11-xfs-6.8.2-7.1.102mdk
$ rpm -qf `which X`
xorg-x11-6.8.2-7.1.102mdk
$ xdpyinfo
vendor string:    Mandrakelinux (X.Org X11 6.8.2, patch level 7.1.102mdk)
vendor release number:    60802000
X.Org version: 6.8.2
...
screen #0:
  print screen:    no
  dimensions:    1400x1050 pixels (370x278 millimeters)
  resolution:    96x96 dots per inch
  depths (7):    24, 1, 4, 8, 15, 16, 32
  root window id:    0x38
  depth of root window:    24 planes
...
  default visual id:  0x21
  visual:
    visual id:    0x21
    class:    TrueColor
    depth:    24 planes
    available colormap entries:    256 per subfield
    red, green, blue masks:    0xff0000, 0xff00, 0xff
    significant bits in color specification:    8 bits

Comment 1

[Mikko Rantalainen]

Attachment: A Test case where hovering is slow in FF 1.5b1

This test case does include MathML markup in the content area of the page;
hovering is slow.

Comment 2

[Mikko Rantalainen]

Attachment: A Test case where hovering is fast in FF 1.5b1

This test case includes only text in the content area of the page;
hovering is as fast as expected.

Comment 3

[Martijn Wargers (dead)]

I'm seeing this also with the testcase in 2005-09-04 trunk build on windows.
A reduced testcase (to the bare minimum required) would be helpful here, I think.

Comment 4

[Mikko Rantalainen]

Attachment: Reduced test case (with some commentary)

A reduced test case. Hovering the menu (at the bottom of the page) is still
slow.

Comment 5

[Mikko Rantalainen]

Attachment: Reduced test case (just the code)

A reduced test case where problematic floats are not even touching each other.
If the DIV with red border doesn't contain MathML content, then hovering is
fast inside the blue DIV.

Resizing the browser window is slow too.

Comment 6

[Mikko Rantalainen]

WFM with Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9a1) Gecko/20051122 Firefox/1.6a1
from http://ftp.mozilla.org/pub/mozilla.org/firefox/nightly/latest-trunk-fs/firefox-1.6a1.en-US.linux-i686.tar.bz2

Comment 7

[Boris Zbarsky [:bzbarsky]]

I can't reproduce this either; should this be resolved as "worksforme"?

Comment 8

[Adam Guthrie]

Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9a1) Gecko/20051227 Firefox/1.6a1

Works for me, too.

Comment 9

[Martijn Wargers (dead)]

The problem is that I now have a very **** videocard, which makes everything slow in Mozilla, so I don't see a difference anymore in the testcase, it's all slow.
When I have a decent videocard again, I'll test again (because I think it wasn't WORKSFORME then).