Bug 15230 – Scrollbar has two thumbs

• Component: Layout and Rendering
• Status: RESOLVED WONTFIX

[Norman Hardy]

This is ephemeral; as soon as any scrolling happens it disappears.
The utility 'Grab' captures the image found at (http://cap-lore.com/bug/bug42.tiff).
Sometimes blob is truncated with square end.

I have been seeing this for a few months.

[David Kilzer (:ddkilzer)]

Thanks for the bug report, Norman.  Does this happen every time you load http://cap-lore.com/HL.html?

[David Kilzer (:ddkilzer)]

Also, what version of Mac OS X and Safari are you using?  Are you using a WebKit Nightly build (http://nightly.webkit.org/)?  Do you have the Safari 3 Public Beta installed?

[Norman Hardy]

Created attachment 16322 [details]
before image

This is the scroll bar just before bug is manifest.
(After is shown in b2.tiff, to come)
Files also at (http://cap-lore.com/bug/bq1.tiff) and (http://cap-lore.com/bug/bq2.tiff)

[Norman Hardy]

Created attachment 16323 [details]
Grab image of scroll bar after bug is manifest

After I hit the back button the upper part of the scroll bar remains unrendered, thus leaving part of the image of the thumb of the previous page visible.
Note the alignment as determined by the text just to the right of the scroll bar and window.
This is very strong circumstantial evidence that the phantom thumb is that from the previous page.
"The ghost of the dead thumb!"
I could go back and forth several times and the bug repeated.

[David Kilzer (:ddkilzer)]

This sounds like a duplicate of Bug 15033.

Norman, could you give exact, step-by-step instructions on how to reproduce this issue?  Or does it appear to happen randomly?

[Norman Hardy]

I agree that this is probably the same as bug 15033.

Here is a rather reliable and simple script that failed three times in three trials.
It is simpler than the test provided for 15033.

Launch Safari (WebKit)
Resize window so that page text display size (page minus chrome) is = 776 wide, 487 high (I measure with Grab) (there is at least a few pixels of tolerance)
go to (http://cap-lore.com/HL.html)
(observe that thumb is at top of scroll bar. This is correct.)
Click on 'CIA' link (under politics, near bottom)
   (Alternatively 'Libertarians')
Click once near bottom in vertical scroll bar.
Click back button.
(observe thumb in wrong position; should be at top of screen.)
Switch to other application.

Observe two thumbs.

Relevant parameters that occur to me:
Preferences > Appearance > Standard font = Cochin 18
Preferences > Security > Web Content: (all four checked)
no proxies

[Ahmad Saleem]

I am not able to reproduce this bug in Safari 16.3 and Safari Technology Preview 164 and I think it was Safari layer bug rather than WebKit unless if earlier version of WebKit was managing scrollbar itself. Since it was happening in scrollbar area where it had background "color" bleed kind of like repaint issue etc.

I am going to mark this as "RESOLVED WONTFIX" but I will CC some to get their input.