Open Bug 1291678 Opened 8 years ago Updated 2 years ago

Some posts on GoT (gathering of tweakers)-forum are scrollable for fractions of pixels

Categories

(Core :: Layout, defect, P3)

49 Branch
All
Android
defect

Tracking

()

Tracking Status
firefox48 --- wontfix
firefox49 --- affected
firefox50 --- affected
firefox51 --- affected

People

(Reporter: f.smulders, Unassigned)

References

()

Details

Attachments

(2 files)

User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:48.0) Gecko/20100101 Firefox/48.0
Build ID: 20160726073904

Steps to reproduce:

Enter one of the threads on gathering.tweakers.net and tried to scroll through the posts


Actual results:

Multiple posts seemed to be 'scrollable' in their own, even though all the information was visible without scrolling.


Expected results:

No scrolling within posts, only through/between posts.
I can reproduce on (for example) the post by Philpend on https://gathering.tweakers.net/forum/list_messages/1709787. It looks like the <div class="post"> has overflow:auto and is fractionally smaller than its contents, and so ends up being scrollable. The clientHeight and scrollHeight are the same, but getBoundingClientRect() returns a fractional number that is ~.2 smaller, so presumably that is what is making it scrollable. Interesting that on desktop it is also fractionally smaller, but it is not scrollable. Do we have different thresholds for scrollability between Fennec and desktop?
Status: UNCONFIRMED → NEW
Ever confirmed: true
Flags: needinfo?(rbarker)
OS: Unspecified → Android
Priority: -- → P3
Hardware: Unspecified → All
Summary: Scrolling not working on GoT (gathering of tweakers)-forum → Some posts on GoT (gathering of tweakers)-forum are scrollable for fractions of pixels
I looked at the prefs and didn't see anything obvious to me that would cause fennec to scroll differently other than fennec has scrolling handoff disabled. But it sounds like the element wasn't even scrollable on desktop? Maybe something inherited from FxOS or a pref I missed/misunderstood? I'm currently going through all of the MOZ_ANDROID_APZ #ifdefs as part of the JPZ removal so I will keep an eye out.
Flags: needinfo?(rbarker)
I think this is a layout bug, if it's a bug at all. It might be evangelism. I saved the page and reduced it somewhat, saved at the bug URL. On Desktop the scrollport for the div is the same size as the scrolled rect, so the scrollframe never scrolls. On Fennec I see that the scrollport is 30 app units smaller than the scrolled rect (15948 vs 15978 on my Xperia Z3C), which is one dev pixel, and so the scrollframe scrolls as expected. The question then is, why is the scrollport 30 app units smaller than the scrolled rect? That seems to be a layout problem or a bug in the page. I'll also attach a frame dump of the reduced page from Fennec.
Component: Graphics, Panning and Zooming → Layout
Product: Firefox for Android → Core
Is this bug actively worked on? Are there things an enduser could do to prevent it from happening?
(In reply to f.smulders from comment #5)
> Is this bug actively worked on?

Not at the moment

> Are there things an enduser could do to
> prevent it from happening?

You could probably use an addon like Stylish to add a user stylesheet for these websites which changes the height of the page contents or the overflowing element in a way that avoids the problem.
Severity: normal → S3
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