Bug 8909 - Vertical scrollbar appears to detach during horizontal scrolling
Summary: Vertical scrollbar appears to detach during horizontal scrolling
Status: NEW
Alias: None
Product: WebKit
Classification: Unclassified
Component: Layout and Rendering (show other bugs)
Version: 420+
Hardware: Macintosh OS X 10.4
: P2 Normal
Assignee: Nobody
URL: http://www.zone-h.org/defacements/mir...
Keywords: HasReduction, InRadar
Depends on:
Blocks:
 
Reported: 2006-05-14 12:11 PDT by David Kilzer (:ddkilzer)
Modified: 2013-06-04 11:17 PDT (History)
3 users (show)

See Also:


Attachments
Screenshot of detached scrollbar (87.19 KB, image/png)
2006-05-14 12:13 PDT, David Kilzer (:ddkilzer)
no flags Details
Movie of page loading and detached scrollbar (155.30 KB, video/quicktime)
2006-05-14 12:15 PDT, David Kilzer (:ddkilzer)
no flags Details
Webarchive of problematic URL (does not exhibit the problem) (18.19 KB, application/x-webarchive)
2006-05-14 12:19 PDT, David Kilzer (:ddkilzer)
no flags Details
Partical reduction (680 bytes, text/html)
2006-06-11 19:33 PDT, David Kilzer (:ddkilzer)
no flags Details
Further reduction (151 bytes, text/html)
2006-06-28 00:21 PDT, mitz
no flags Details

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Description David Kilzer (:ddkilzer) 2006-05-14 12:11:39 PDT
Summary: 

When a particular page loads, a vertical scrollbar is drawn and then later not needed, but it is never "undrawn" later (unless the window is resized or Safari is hidden and unhidden).  When the horizontal scrollbar is used, it appears to detach the vertical scrollbar that is no longer used.

Steps to Reproduce: 

1. Open Safari.
2. Load this URL:  http://www.zone-h.org/defacements/mirror/id=3680404/
3. If the vertical scrollbar is usable, click the "Reload" button once.

Expected Results: 

The vertical scrollbar should disappear after it is no longer being used.

Actual Results: 

The vertical scrollbar does not disappear after it is no longer being used.

Regression: 

This occurs in a local nightly build based on Subversion revision r14360.

It also occurs in Mac OS X 10.4.6 (Build 8I127) with Safari 2.0.3 (417.9.3).

Notes: 

This is bug is very timing-based during the page load.  Currently, about half of the page loads from the original web site cause this problem.
Comment 1 David Kilzer (:ddkilzer) 2006-05-14 12:13:14 PDT
Created attachment 8306 [details]
Screenshot of detached scrollbar
Comment 2 David Kilzer (:ddkilzer) 2006-05-14 12:15:07 PDT
Created attachment 8307 [details]
Movie of page loading and detached scrollbar

Note that the initial page load does not cause the problem, but the reload of the page does.
Comment 3 David Kilzer (:ddkilzer) 2006-05-14 12:19:54 PDT
Created attachment 8309 [details]
Webarchive of problematic URL (does not exhibit the problem)

Note that the webarchive does not exhibit the problem since it is a timing issue.
Comment 4 David Kilzer (:ddkilzer) 2006-05-14 12:30:16 PDT
Created Radar bug 4547726.  rdar://problem/4547726
Comment 5 David Kilzer (:ddkilzer) 2006-06-11 05:28:00 PDT
(In reply to comment #0)
> 2. Load this URL:  http://www.zone-h.org/defacements/mirror/id=3680404/

The web site has been redesigned and the URL above no longer exists.  Hopefully there is enough information to recreate the problem using the webarchive.  Here is the new URL for the redesigned site (for what it's worth):

http://www.zone-h.org/index2.php?option=com_mirrorwrp&Itemid=43&id=3680404
Comment 6 David Kilzer (:ddkilzer) 2006-06-11 19:33:33 PDT
Created attachment 8815 [details]
Partical reduction

This is a partial reduction of the problem.  The only external link left is the original <iframe> source.  I think it works well because it takes a while to load.  (For example, you could change the source to http://www.google.com/, but the problem doesn't reproduce as reliably.)

To reproduce the problem, shift-reload this page until the gray border at the bottom is fully visible, then scroll to the right.  The vertical scrollbar should appear to "detach", but is really just an artifact that should have been redrawn after it was no longer needed.
Comment 7 David Kilzer (:ddkilzer) 2006-06-11 19:36:33 PDT
Mitz, I'm cc-ing you since I thought you'd get a kick out of the visual effects of this bug.
Comment 8 jonathanjohnsson 2006-06-15 14:51:58 PDT
Maybe of interest: The description of a bug in Safari at the Ars Technica forum ( http://episteme.arstechnica.com/eve/forums?a=tpc&s=50009562&f=8300945231&m=869008469731&r=882003569731#882003569731 ) sounds very much like this one.
Comment 9 mitz 2006-06-28 00:21:58 PDT
Created attachment 9073 [details]
Further reduction

It looks like the root cause is indeed a variation on bug 9531. The solution might be to take stronger action in the "view height changed" case added in that fix.
Comment 10 David Kilzer (:ddkilzer) 2006-06-28 04:00:08 PDT
(In reply to comment #9)
> Created an attachment (id=9073) [edit]
> Further reduction
> 
> It looks like the root cause is indeed a variation on bug 9531. The solution
> might be to take stronger action in the "view height changed" case added in
> that fix.

I can't get this reduction to ever "detach" the vertical scroll bar (I'm still on 10.4.6 on PowerPC), but I suppose with a height of 100%, there shouldn't be a vertical scrollbar anyway.

Comment 11 mitz 2006-06-28 04:08:28 PDT
(In reply to comment #10) 
> I can't get this reduction to ever "detach" the vertical scroll bar (I'm still
> on 10.4.6 on PowerPC), but I suppose with a height of 100%, there shouldn't be
> a vertical scrollbar anyway.
>  

Sorry. I should have clarified that the reduction is for that part of the bug. I'm going to try to add the second part, or better yet, a case that starts out with a legitimate vertical scrollbar.
Comment 12 mitz 2006-10-08 23:01:43 PDT
Bug 11224 is the "horizontal scrollbar" version of this bug.
Comment 13 Robert Hogan 2013-06-04 11:17:32 PDT
Can anyone still recreate this bug with any of the available reductions? I'm drawing a total blank - seems like there's nothing to do here anymore.