129981 - Manipulating opacity seems to affect block's margins

Status: RESOLVED FIXED

(Core :: Layout: Block and Inline, defect, P3)

Description

[Porter Glendinning]

(I'm not sure if this should be a style issue or an event handling one, but the
latter seems more proper.)

The sample URL points to a page containing two sets of links whose display has
been changed to "block". The first set is fine; however, mousing over the links
in the second set from top to bottom causes the elements to push apart, and
mousing back up from the bottom causes them to contract again. The only
difference between the two sets are two CSS rule sets that apply to the links in
the second set to manipulate the links' opacity with "-moz-opacity."

I've tested this with several of the latest nightlies (currently today's:
20020310). I will double check, but I don't believe this was happening in the
0.9.8 release.

Comment 1

[Porter Glendinning]

I've checked with the 0.9.8 release on WinNT, and I was right -- it does not
exhibit this behavior.

Comment 2

[Jonathan Watt [:jwatt]]

Confirming in 0.9.9 on WinME. 

Comment 3

[Porter Glendinning]

This is still a problem in recent nightlies (2002040803).

Comment 4

[Porter Glendinning]

I may have tracked down more specific behavior on this bug. I believe what's
happening is that manipulating the opacity of an element with the :hover
pseudo-class is causing that element's bottom margin not to collapse with the
following element's top margin, for some reason.

I've updated the referenced URL to show a third case with larger top and bottom
margins on the elements, and you can see that the jump is much larger --
basically doubling the space between the elements.

Comment 5

[Porter Glendinning]

This problem is still present in the current nightly build (2002081004).

Comment 6

[Porter Glendinning]

I had implemented a temporary fix for this problem on my home page, but the 1.2a
release now breaks my fix. Will post more once I've had a chance to debug a
little better.

Comment 7

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

->Layout.

Comment 8

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

er, really this time

Comment 9

[Jesse Ruderman]

Attachment: testcase: changing h3's opacity temporarily doubles its margin-bottom

Comment 10

[Jesse Ruderman]

I was about to resummarize this bug as "Changing block's opacity temporarily
doubles effect of margin-bottom", but I noticed that in my testcase, changing
the h3's opacity also makes the h3 move up a pixel or two.

Comment 11

[Porter Glendinning]

Just removing the "on hover" from the summary, since it seems pretty clear now
that it's any sort of manipulation of the opacity that causes this problem.

Comment 12

[Benjamin Smedberg]

*** Bug 193411 has been marked as a duplicate of this bug. ***

Comment 13

[Boris Zbarsky [:bzbarsky]]

Fixed by checkin for bug 257612