517820 - Distorted page contents when scrolling

Status: RESOLVED WORKSFORME

(Core :: Web Painting, defect)

Description

[LRN]

User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 5.2; en-US; rv:1.9.3a1pre) Gecko/20090920 Minefield/3.7a1pre
Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.2; en-US; rv:1.9.3a1pre) Gecko/20090920 Minefield/3.7a1pre

http://clang.llvm.org/features.html#enduser (and all other pages on clang.llvm.org) are the only pages where i have seen this bug so far.

It looks like Minefield scales the image it draws with a nearest-neighbor scaling method when it scrolls the page. There's no actual scaling there, of course, but the 'tearing' effect it usually produced is there. One can also describe it as a 'tearing' effect produced by single-buffered (as opposed to double-buffered) drawing, but multiplied across the whole image.

Affects the whole part of the page that is being scrolled, including both text and images.

This bug is not showing itself in latest Firefox (3.5.3), only normal tearing (due to the lack of refresh rate synchronization) is visible there, but it is barely noticeable.

The bug is evident when smooth scrolling is enabled or when vertical scroll bar is slowly dragged.

Reproducible: Always

Steps to Reproduce:
1. Go to http://clang.llvm.org/features.html#enduser
2. Enable smooth scrolling
3. Scroll the page
Actual Results:  
Scrolled area is distorted, tearing is obvious.

Expected Results:  
Scrolled area should not be distorted, tearing should not be seen.

Windows XP x64 SP2, latest Minefield at the moment, an ATI video card.

Comment 1

[Ria Klaassen (not reading all bugmail)]

Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.9.3a1pre) Gecko/20090919 Minefield/3.7a1pre

I see no problem at first glance, the page seems normal. Can you provide a screenshot? https://bugzilla.mozilla.org/attachment.cgi?bugid=517820&action=enter
Thanks!

Comment 2

[LRN]

It is not possible to register the bug on a screenshot, so i've recorded a video. It's 4.6 Mb, so i wouldn't even try to upload it here. But you can get it from my server - http://lrn.no-ip.info/other/scroll_minefield_00.ogv (and take advantage of Firefox built-in Theora support!)

Comment 3

[Ria Klaassen (not reading all bugmail)]

On your video I see that it scrolls a bit jumpy. I can't reproduce that exactly but I do see that Minefield scrolls less pleasant than Shiretoko. You can't follow the text with your eyes while scrolling down.

Comment 4

[LRN]

If you play it with a standalone video player (with frame stepping capability) you will see frames with distortions (such as frame #149, #810 or #828, as shown by SMplayer frame counter). Firefox plays the video a bit too fast to notice anything other than general jumpiness.

Comment 5

[Ria Klaassen (not reading all bugmail)]

Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.9.3a1pre) Gecko/20091001 Minefield/3.7a1pre

OK, I can reproduce it today. With Shiretoko you see the jumpiness with the images and with Minefield the problem has worsened and devided itself over the whole page.

Comment 6

[Ria Klaassen (not reading all bugmail)]

This is a rather new laptop BTW and scrolling shouldn't be a problem:
Intel Pentium Dual T3200 1995 MHz, NVIDEA GeForce 9200M GS, memory 3068 MB.

Comment 7

[Wayne Mery (:wsmwk)]

LRN, do you still see this issue?

Comment 8

[LRN]

No.