486635 - Slow Scrolling with Page Zoom on sites with non-fixed background images

Status: RESOLVED INCOMPLETE

(Core :: Graphics, defect)

Description

[Gordon Byrnes]

User-Agent:       Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.5; en-US; rv:1.9.1b3) Gecko/20090305 Firefox/3.1b3
Build Identifier: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.5; en-US; rv:1.9.1b3) Gecko/20090305 Firefox/3.1b3

Firefox 3.1b3 has extremely bad scrolling performance when using a page zoom setting other than the default (can be higher or lower) on many sites. Definitely specific to certain sites. On some sites, zooming the page has little to no impact on scrolling smoothness or delay, while on others any change to the zoom setting immediately makes scrolling all but impossible. The problem does not seem related to apparent complexity of the site, as seemingly very simple layouts can also exhibit it (e.g., http://www.lclark.edu/~campion/hist217/sched.htm). It occurs whether or not smooth scrolling is enabled, although is most noticeable with smooth scrolling. This is a regression since Firefox 3.1b2. Page zooming must be enabled — simply zooming text does not cause the problem to occur. I have reproduced with 100% reliability on both Windows XP SP3 and Mac OS 10.5.6.

Reproducible: Always

Steps to Reproduce:
1. load a page exhibiting the problem (e.g., http://www.rottentomatoes.com/ , http://www.lclark.edu/~campion/hist217/sched.htm and many others)
2. increase or decrease the page zoom by any amount.
3. Attempt to scroll up or down on the page.
Actual Results:  
Scrolling should be very slow, with a long lag time. Almost uncontrollable.

Expected Results:  
Scrolling should remain smooth and instantaneous as it was prior to zooming the page.

Comment 1

[Gordon Byrnes]

So this bug has been present in the last two betas of Firefox 3.1 (b3 and b4). I do hope it isn't being ignored, as it is a serious regression for anyone who actually uses the zooming feature.

Comment 2

[Gordon Byrnes]

Bug seems to be related to large background images used on sites. Removal of background images immediately demonstrates 100% improvement.

Comment 4

[RNicoletto]

Attachment: Reduced testcase

This ZIP file contains a reduced testcase:
- a basic HTML page with some text
- a CSS file that "call" the background image
- a small JPEG file (150x150) as the background image

Comment 5

[Dimitrios]

Confirming and slightly modifying summary. This one is slightly different than bug #487267, because it occurs with non-fixed backround image (although the performance hit is much worse with fixed background). I expect them both to be resolved by the same patch (whenever it comes).

Comment 6

[Carlos Alén Silva]

This bug affects Gecko 1.9.2 too.

Comment 7

[Tanner M. Young [:tmyoung]]

Is this a problem on the latest trunk nightly (4.0b2pre or higher) now that retained layers have been implemented?

Comment 8

[u41249]

Certain pages under current Sea Monkey have dead slow scrolling on zoom level 200%.

Example: open http://users.livejournal.com/_windwalker_/friends
Zoom to 150%, observe slowness.

Comment 9

[Stewart]

Tested with current release, Iceweasel-38.4.0
The 3 example pages given above are not speedy fast in scrolling, but is "tolerable." up to 1 second wait typical, 2 seconds for some images on the page.
Same refresh time as this page actually.
Increasing zoom levels seems to be the same speed now.

I say barely & grugingly "tolerable," because running an old browser like Seamonkey-1.1 scrolls super fast without the new CSS stuff, and there's lots of other bug reports about slow scrolling in general, so I think this specific issue connected with page-zoom may be fixed.

Comment 10

[BugBot [:suhaib / :marco/ :calixte]]

The severity field for this bug is relatively low, S3. However, the bug has 14 votes.
:bhood, could you consider increasing the bug severity?

For more information, please visit auto_nag documentation.

Comment 11

[BugBot (nomail) [:suhaib / :marco/ :calixte]]

The last needinfo from me was triggered in error by recent activity on the bug. I'm clearing the needinfo since this is a very old bug and I don't know if it's still relevant.

Comment 12

[BugBot [:suhaib / :marco/ :calixte]]

Clear a needinfo that is pending on an inactive user.

Inactive users most likely will not respond; if the missing information is essential and cannot be collected another way, the bug maybe should be closed as INCOMPLETE.

For more information, please visit auto_nag documentation.