301429 - Autoscroll doesn't scroll position:fixed element on snook.ca

Status: RESOLVED DUPLICATE of bug 189308

(Core :: Layout: Positioned, defect)

Description

[Grey Nicholson (they/them)]

Visit http://www.snook.ca/archives/000386.html
Ensure autoscroll is enabled and that the horizontal scroll bar is alive
Autoscroll horizontally (by pressing the wheel button)

The comments form and the rest of that div's content don't move with the rest of
the page. They snap back into position when using a scrollbar.

The div (#postcomment) is position:fixed; the bug does not manifest itself if
this is changed to position:absolute using DOM Inspector.

My feeble attempts to cook up a reduced testcase couldn't reproduce the bug, but
it was confirmed on MozillaZine forums (
http://forums.mozillazine.org/viewtopic.php?p=1617104#1617104 ).

Comment 1

[Martijn Wargers (dead)]

It's the purpose of position:fixed elements to not move, when the window is
scrolled.
So I think this is invalid.

See:
http://www.w3.org/TR/2005/WD-CSS21-20050613/visuren.html#choose-position
"...the box is fixed with respect to the viewport and doesn't move when scrolled"

Comment 2

[Grey Nicholson (they/them)]

There must be some sort of bug here because it snaps back into place when the
scroll bars are used - i.e. the method of scrolling affects the display.

Comment 3

[Ben Basson]

I see this too. It's probably important to emphasise that to reproduce this you
need to scroll _horizontally_ and not vertically.

Comment 4

[Martijn Wargers (dead)]

Ah, sorry, now I see the bug. Forget about comment 1.

Comment 5

[Martijn Wargers (dead)]

Ok, I have investigated it a bit more.
I still think it is invalid.
Compare with javascript turned on/off.
With javascript turned off is the correct behavior.
See: http://www.snook.ca/_images/j/snook.js
This has an onscroll event handler which probably does this weird thing (which
in the case for Mozilla shouldn't have to, since it supports position:fixed).

Comment 6

[Grey Nicholson (they/them)]

(In reply to comment #5)
> This has an onscroll event handler which probably does this weird thing (which
> in the case for Mozilla shouldn't have to, since it supports position:fixed).

In that case the bug is that the onscroll event handler doesn't play nicely with
autoscroll and mouse-wheel scrolling.

I think the intention is to have the position:fixed behaviour vertically but
position:absolute-like behaviour horizontally.

Comment 7

[Martijn Wargers (dead)]

(In reply to comment #6)
> In that case the bug is that the onscroll event handler doesn't play nicely with
> autoscroll and mouse-wheel scrolling.
Yes, and that's basically bug 189308. So indeed, you could say this depends on a
fix for that bug.

Comment 8

[Grey Nicholson (they/them)]

(In reply to comment #7)
> (In reply to comment #6)
> > In that case the bug is that the onscroll event handler doesn't play nicely with
> > autoscroll and mouse-wheel scrolling.
> Yes, and that's basically bug 189308. So indeed, you could say this depends on a
> fix for that bug.

Actually, I think it's just a dupe. Thanks for your help.

*** This bug has been marked as a duplicate of 189308 ***