149933 - Fixed-positioned elements leave artifacts when scrolling

Status: RESOLVED DUPLICATE of bug 93526

(Core :: CSS Parsing and Computation, defect)

Description

[Millennium]

From Bugzilla Helper:
User-Agent: Mozilla/5.0 (Macintosh; U; PPC Mac OS X; en-US; rv:1.0.0+)
Gecko/20020518
BuildID:    Chimera 0.2.8, Mach/ATSUI, and Mozilla 1.0

When scrolling any fixed-positioned element, artifacts are left behind. This
only seem to apply when scrolling by some mechanism other than a page at a time,
such as the arrow keys, scroll arrows, dragging the scroll thumb, or the scroll
wheel. When the scroll is complete, an image of the element is drawn where it
would be if the object were absolutely-positioned rather than fixed-positioned,
but then the actual element is also drawn in its proper place. The artifact
itself doesn't do anything except sit there (i.e. links in the artifact are
unclickable and don't respond to :hover rules) but the actual element works as
normal.

Reproducible: Always
Steps to Reproduce:
1. Visit any page with a fixed-positioned element. http://www.w3.org/Style/CSS
will do.
2. Scroll the page by any method other than a screenful at a time. Arrow keys,
scroll arrows, dragging the scroll thumb, and such will all work.
3. Observe the fixed-positioned element and the space around it.

Actual Results:  The element is drawn in its proper position, but behind it
(seemingly as part of the page background) is an image of the element where it
would be if it were absolutely-positioned instead of fixed.

Expected Results:  The element is drawn in its proper position, and no artifacts
are visible.

This only seems to occur in builds which use Quartz for rendering text. This
includes Mach/ATSUI and Chimera, of course. But, interestingly, it also includes
the normal CFM builds if the user is running BOTH OSX 10.1.5 and Silk, a haxie
by <a href="http://www.unsanity.com">Unsanity</a> which enables Quartz text
drawing in all Carbon apps (this requires 10.1.5).

I rated this "major" because it's highly visible. Even though position:fixed is
not in particularly popular use yet, people are starting to experiment with it.

Comment 1

[Eric A. Meyer (dead account)]

I'm pretty sure this is a duplicate of bug 93526.

Comment 2

[Millennium]

Although it's similar to the bug 93526, I'd argue that it's not quite a
duplicate. This seems to only affect Quartz-enabled builds (93526 doesn't seem
to), and the workaround mentioned in that bug (inserting an image into the fixed
element) doesn't work here.

Comment 3

[Eric A. Meyer (dead account)]

I already pointed out in 93526 that the image-insertion trick doesn't always
work; it did simply in that particular testcase.  I'd be curious to hear if
taking the steps required for that testcase have simmilar results for you in a
Quartz build-- if not, that's useful information and may help track down the
problem.  Anyway, I'll let the owner/QA decide whether or not they think these
are duplicates, or instead closely related.

Comment 4

[Greg K.]

This is certainly a duplicate.

Milennium, if bug 93526 gets fixed and this problem is still evident, then reopen.

*** This bug has been marked as a duplicate of 93526 ***