197020 - excessive flashing on page load

Status: RESOLVED DUPLICATE of bug 115429

(Core :: Layout, defect)

Description

[Dan Price]

User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.3b; StumbleUpon.com) Gecko/20030210
Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.3b; StumbleUpon.com) Gecko/20030210


This page flashes 6 or seven times in a very distracting way during page load,
on a reasonably fast (1.3GHz) machine.  The load time is also fairly high,
even when loading a saved version from the filesystem.

It looks like it is triggering some expensive behavior in the layout engine.

IE renders this page in a snap, with no flashing.

Reproducible: Always

Steps to Reproduce:
1. Visit the URL given.
2.
3.

Comment 1

[Dan Price]

Even Nav 4.x doesn't flash loading the page :)

Comment 2

[Warner Young]

Probably bug 196308.

Comment 3

[Matthias Versen [:Matti]]

confirming with todays win2k trunk build

Comment 4

[Rainer Bielefeld]

I confirm the problem with
Mozilla/5.0 (Windows; U; Win98; en-US; rv:1.4a) Gecko/20030304
and also
Mozilla/5.0 (Windows; U; Win98; en-US; rv:1.2b) Gecko/20021029 Phoenix/0.4
No Problems with NC4.73, IE6, OPERA6

I think the problem here is not the same as in bug 196308
Here we see when loading:
- Background is visible immediately
- Text appears - goes away - reappears - goes away appears ....
  and so on until page is loaded completely
- loading rendering page causes much CPU-load (on my system app 100%)

Might be interesting:
- "View Page Info" needs endless to list all links (there are very many)
- On my DSL-Speed-Manager I see that always when the page reappears, the 
   load-speed goes to 0 for a little moment
- Problem is visible when I load the page in a new TAB and also if I load it in 
  a new window
- I see the Problem if I load the page in the composer, too

Comment 5

[Rainer Bielefeld]

I ss it in
Mozilla/5.0 (Windows; U; Win98; de-DE; rv:1.0.2) Gecko/20030208 Netscape/7.02
(Compact)
too

I had "Pipelining off"

Comment 6

[Boris Zbarsky [:bzbarsky]]

This is a problem on Linux too.

Could someone produce a minimal testcase?  I suspect something's making us
reframe the whole page or something dumb like that....

Comment 7

[Larry Belan]

Agent:  Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.3b) Gecko/20030311
Phoenix/0.5

I'm using the daily builds of Phoenix, and think this problem creeped in over
the weekend 03-08 or 03-09.

An easy way to reproduce this is just open two window tabs (about:blank) and
switch back and forth.  The flashing is very annoying.  Looks like the code is
redwawing the entire window in a black, then quiclkly refreshes the display.  

Comment 8

[Boris Zbarsky [:bzbarsky]]

Larry, you are seeing a DIFFERENT bug from this one.  And the bug you are seeing
is fixed on the Mozilla trunk.

Comment 9

[Larry Belan]

Thanks Much!  Sorry.  After a two hour download of today's Phoenix build, the
problem I was describing on IS gone.  :)

Comment 10

[Ronald Tilby]

Mozilla/5.0 (Windows; U; Win98; en-US; rv:1.4a) Gecko/20030312
200 mhz processor
The page in the URL takes nearly 8 minutes to render from my C: drive.
I corrected the markup by adding a <dl> before the first <dt> and a corresponding 
</dl> at the end of the page, and rendering time went to about 30 seconds, with no
spurious redrawing.
There over 1000 empty <p> </p> pairs in the page, and that may be contributing
to the problem.

Comment 11

[Boris Zbarsky [:bzbarsky]]

OK.  Now how much stuff can you remove from the page and _still_ have it flash?

Comment 12

[Ronald Tilby]

This is a duplicate of 115429.

Comment 13

[Maarten Afman]

Found invalid HTML: the DL tag is missing. 

Per HTML 4.0 the <DL> and </DL> are REQUIRED for defining a definition list. If
you don't provide them then Moz renders the page different: now only DD's first
line is indented versus the entire paragraph with proper usage of DL and DD. 

Compare my attached wgg-orig.html and wgg-fixed.html which I attach. 

It seems the original HTML contains over 1000+ DL lists where after adding DL
tags we now have 3 proper DL's and no flickering. 

Someone mark this bug INVALID?

Comment 14

[Maarten Afman]

Attachment: fixed HTML (.ZIP compressed)

This is the modified HTML file.
The only modification is the insertion of the <DL> and </DL> tags at proper
locations. Speedy loading and completely flickerfree! (1.3 final)

Comment 15

[Ronald Tilby]

Maarten, I agree that the HTML4.0 spec requires <dd>'s to be nested in <dl>
</dl>'s.  But the problem here is that the screen flashes and performance is
awful when the markup is bad.  I believe the browser should perform better than
it is when rendering this specific case of bad markup.  See bug 115429 for
further details and a testcase exhibiting this problem.

Comment 16

[Maarten Afman]

Ronald, I completely agree with your statement above! 

I overlooked bug 115429, the missing DL behaviour is precisely known to
bugzilla, that's a relief. It is really funny the amount of speedup you get just
adding the missing DL tags! If there were a list of tips for develioping for
Mozilla then this should definitely be on that list. 

Anyway the maintainer of the URL referenced clearly wants the functionality of
the HTML definition lists so he should fix his code to include DL tags. Doing
that there is no other problem with mozilla here so that renders this bug
INVALID IMO. Mozilla clearly has a problem in this area but for this author that
is not relevant once he adds the tags per the spec. 

Else make it a duplicate, but then you have two open bugs about the same thing.

Comment 17

[Christopher Hoess (gone)]

*** This bug has been marked as a duplicate of 115429 ***