256538 - Can't scroll window with scroll wheel if a position: fixed element covers the top-left corner of the viewport.

Status: RESOLVED FIXED

(Camino Graveyard :: General, defect)

Description

[Wevah (Nate Weaver)]

User-Agent:       Mozilla/5.0 (Macintosh; U; PPC Mac OS X Mach-O; en-US; rv:1.8a3) Gecko/20040820 Camino/0.8+
Build Identifier: Mozilla/5.0 (Macintosh; U; PPC Mac OS X Mach-O; en-US; rv:1.8a3) Gecko/20040820 Camino/0.8+

Scrolling works fine for me with Camino builds before 2004-08-07 (incidentally
the day that the fix for Bug 97283 was checked in). This does not affect
Firefox. I have had a few people check under 10.3, but they were able to scroll
just fine, so I'm guessing it's a 10.2-only occurrence (it could be my machine,
too, but I'd rather play it safe).

Other test URL: http://weblogs.mozillazine.org/hyatt/ with one of the "Clean"
stylesheets selected.

Reproducible: Always
Steps to Reproduce:
1. Navigate to a page with a position: fixed; element that covers the top-left
corner of the viewport.
2. Attempt to scroll with a scroll wheel.

Actual Results:  
Page did not scroll.

Expected Results:  
Page should scroll.

Comment 1

[Hiro]

It reproduced.
And there is no problem in Mozilla.

Mac OS X 10.3.5
-- Camino 2004081919 (v0.8+)
-- Mozilla/5.0 (Macintosh; U; PPC Mac OS X Mach-O; en-US; rv:1.8a3) Gecko/20040822

Comment 2

[Mike Pinkerton (not reading bugmail)]

is this different from the scrollwheel-<div> bug that affects all mozilla platforms?

Comment 3

[Wevah (Nate Weaver)]

I believe so, since this doesn't occur in Mozilla or Firefox. Were you referring
to Bug 237962? I've seen that one also, in Camino, Firefox, and Mozilla for
quite a while, but this one is fairly recent and seems to be Camino-only. If I
move the fixed div on either the sample page or Hyatt's weblog right or down by
1px, the scroll wheel functions properly.

Comment 4

[Mats Palmgren (inactive)]

I can take a look if I can dig up a Mac with a mouse-wheel...

Comment 5

[Mike Pinkerton (not reading bugmail)]

-> mats

Comment 6

[Mats Palmgren (inactive)]

Attachment: Testcase

Comment 7

[Mats Palmgren (inactive)]

There are two separate problems:

1. The new code in ESM::DoScrollText (bug 97283) is expecting that
   |aTargetFrame| is set to the frame that is under the mouse.
   In Camino this is not the case.
   For the testcase it's set to the text frame at position 0,0 regardless
   of the mouse position. (The |aEvent| is also at 0,0).
   This is a deeper platform-specific problem that I would prefer someone
   else have a look at.
   
2. Mouse-wheel scrolling over fixed pos. elements does not propagate so that
   it can affect the viewport scrollbar (occurs on all platforms).

This bug is about problem 1. I have spawned off bug 258006 for problem 2.

-> default owner

Comment 8

[Jasper]

*** Bug 260341 has been marked as a duplicate of this bug. ***

Comment 9

[Wevah (Nate Weaver)]

Removing "under OS X 10.2" as this has apparently been verified under 10.3.x also.

Comment 10

[Geoff "temporarily off bugmail" Beier]

Attachment: this solves the scrolling problem for all test cases i've seen

the problem is that we set the location of scroll events to 0,0, and fixed
elements don't pass scroll events. So a position:fixed element at 0,0 stops
camino from scrolling a page at all.

the original reason for doing this was performance. this patch removes the code
that sets the location to 0,0, no longer seems to impact performance, and makes
scrolling work again.

Comment 11

[Wevah (Nate Weaver)]

Comment on attachment 160364 [details] [diff] [review]
this solves the scrolling problem for all test cases i've seen

Marking r+; seems to fix a few other mild annoyances as well.

Comment 12

[Geoff "temporarily off bugmail" Beier]

Comment on attachment 160364 [details] [diff] [review]
this solves the scrolling problem for all test cases i've seen

should this maybe go to the branch as well?

Comment 13

[Mike Pinkerton (not reading bugmail)]

landed on trunk, dunno if we need this on the branch. i don't think so.