268312 - Focusing links very slow on this page (links in pre tag)

Status: RESOLVED WORKSFORME

(Core :: Layout, defect)

Description

[Martijn Wargers (dead)]

User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8a5) Gecko/20041106 Firefox/0.9.1+
Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8a5) Gecko/20041106 Firefox/0.9.1+

That page contains a lot of links in a <pre> tag. 
When the window has a small width (say 500px wide), tabbing through those links
becomes very slow. 

The regression range is 2004-07-16/2004-07-17, so I think this bug is most
likely caused by the fix for bug 151375.

Reproducible: Always
Steps to Reproduce:
1.
2.
3.

Comment 1

[Martijn Wargers (dead)]

Attachment: testcase

I'm doing this in a <pre> tag:
for (var i=0;i<3000;i++){
document.write(' <a href="#">NetworkManager-gnome-0.3.1-3...&gt;</a>
02-Nov-2004 11:07\n');
}
to make a lot of links. 
This is quite slow when tabbing through the links.
But when I remove the space just before the link, tabbing through the links
become much faster.

Comment 2

[Martijn Wargers (dead)]

Attachment: Testcase2 (faster)

Same as the first testcase, but this one is faster with tabbing through the
links, because I removed the space just before the link.

Comment 3

[Boris Zbarsky [:bzbarsky]]

Profiling shows that all the time is spent in block reflow (ReflowDirtyLines and
the like).  It's not clear to me why having a space at the beginning of the line
would affect the performance here...

Comment 4

[Martijn Wargers (dead)]

Strangely enough, testcase2, is now rather slow in current trunk build and the first testcase is quite fast.
So something has changed between 2004 and now.

Comment 5

[Ronald Tilby]

Mozilla/5.0 (Windows NT 5.1; rv:17.0) Gecko/17.0 Firefox/17.0 ID:20120928042009
Testcase 2 is more cpu intensive, but both testcases are WFM in current Aurora build.