1327869 - Mouse wheel (PageDown) STILL scrolls too far on pages with fixed header elements, and some lines stay invisible

Status: NEW

(Core :: Layout, defect, P3)

Description

[arni2033]

>>>
STR_1:
1. Open url [1]
2. Open responsive design view (Ctrl+Shift+M), set resolution to 1200x928
  (or choose any other height, just make sure that the page is scrolled to the top,
   and the last visible line ends with "Martin Van")
3. Click on the page, press PageDown button

AR:  The page scrolls to much, so one line stays invisible. It affects my UX a lot,
     because I use mouse option "when I rotate mouse wheel" set to "scroll by 1 page"
     
ER:  All text lines should be visible as I scroll the page, just like in GoogleChrome


Note:  I don't need Step 2 on my screen. Ignore Step 2 if you want to understand the impact of the bug

> [1] http://www.newyorker.com/magazine/2016/06/27/hillary-clinton-and-the-history-of-women-in-american-politics

Comment 1

[arni2033]

Note that I reported this bug as an indication that what was implemented in bug 780345 was not enough to fix the original UX issue. And as a possible argument to resolve bug 1328047 by completely removing the feature implemented in bug 780345.
It was occasionally reported w/ status "NEW", in fact I'm not sure about status, given that I personally want bug 1328047 to be resolved by removing all changes from bug 780345.

Comment 2

[Timothy Nikkel (:tnikkel)]

So the reason the fixed position adjustment isn't working on this page is that the fixed pos element has height zero, and the fixed position content that actually takes up space is a position: absolute child of zero-height fixed pos element. We don't look at the whole fixed subtree in nsGfxScrollFrame, just the direct children of the viewport.

Comment 3

[Timothy Nikkel (:tnikkel)]

We can't even use the visual overflow rect here because the visual overflow rect covers the entire viewport.

Comment 4

[bshanks3]

I have a similar problem, but only when NOT in responsive design view.

On the URL http://www.economist.com/news/world-week/21722228-politics-week , pressing PageDown scrolls one line too far.

Interestingly, there are a bunch of similar, but supposedly resolved, issues in Bugzilla, which i found before finding this one: https://bugzilla.mozilla.org/show_bug.cgi?id=780345 https://bugzilla.mozilla.org/show_bug.cgi?id=1081272

Comment 5

[bshanks3]

More similar resolved bugs:

https://bugzilla.mozilla.org/show_bug.cgi?id=830479 https://bugzilla.mozilla.org/show_bug.cgi?id=1224307 https://bugzilla.mozilla.org/show_bug.cgi?id=1225201 https://bugzilla.mozilla.org/show_bug.cgi?id=1327869

Comment 6

[bshanks3]

(oops the last one in the list in the previous comment is THIS bug, which is not resolved obviously, sorry)

Comment 7

[Timothy Nikkel (:tnikkel)]

(In reply to bshanks3 from comment #4)
> On the URL http://www.economist.com/news/world-week/21722228-politics-week ,
> pressing PageDown scrolls one line too far.

That appears to be the same problem as comment 2 (except the overflow rect is reasonable and not the whole page). Safari and Chrome seem to have the same problem with this page.

Comment 9

[Jonathan Watt [:jwatt]]

Mass bug change to replace various 'parity' whiteboard flags with the new canonical keywords. (See bug 1443764 comment 13.)

Comment 10

[nyanpasu64]

The same issue has arisen with new Twitter. Should I report a new bug?

• The center of the page scrolls. The left and right are fixed.
• The fixed header only covers the center of the page.
• The scrollbar is to the right of the entire window, not the right of the scrolling center column.

Example URL: https://twitter.com/dril