939846 - Consider changing the padding area for fieldset elements with a legend

Status: RESOLVED WONTFIX

(Core :: Layout: Form Controls, enhancement)

Description

[Alice0775 White]

Tgis is spun off from Bug 770645 Comment 13

There are two fieldsets, one without overflow and another with.
The second fieldset is working good in Firefox 25 but not in Firefox 27.0a2

STR
Open attachment 8333818 [details] 

Regression window(m-c)
Good:
http://hg.mozilla.org/mozilla-central/rev/9f8233fcce1d
Mozilla/5.0 (Windows NT 6.1; WOW64; rv:27.0) Gecko/20100101 Firefox/27.0 ID:20131025025009
Bad:
http://hg.mozilla.org/mozilla-central/rev/85ade1df0597
Mozilla/5.0 (Windows NT 6.1; WOW64; rv:27.0) Gecko/20100101 Firefox/27.0 ID:20131025092711
Pushlog:
http://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=9f8233fcce1d&tochange=85ade1df0597


Regression window(m-i)
Good:
http://hg.mozilla.org/integration/mozilla-inbound/rev/c79088ab4e0c
Mozilla/5.0 (Windows NT 6.1; WOW64; rv:27.0) Gecko/20100101 Firefox/27.0 ID:20131024215509
Bad:
http://hg.mozilla.org/integration/mozilla-inbound/rev/c1578a4fc86d
Mozilla/5.0 (Windows NT 6.1; WOW64; rv:27.0) Gecko/20100101 Firefox/27.0 ID:20131025004510
Pushlog:
http://hg.mozilla.org/integration/mozilla-inbound/pushloghtml?fromchange=c79088ab4e0c&tochange=c1578a4fc86d

Suspected:
	44de05b3239b	Robert O'Callahan — Bug 261037. Support scrolled fieldsets. r=mats

Comment 1

[Boris Zbarsky [:bzbarsky]]

The old rendering just showed us not actually applying the overflow property.

The new rendering looks correct to me, insofar as you can reason about how CSS applies to <fieldset> at all.

Comment 2

[Mats Palmgren (inactive)]

I think attachment 730479 [details] might be a better testcase for the issue I had in mind.
See attachment 731562 [details] for a screenshot of how other UAs rendered it 2013-03-30.
It appears they have a different idea of where the (top) clip edge should be.
I don't necessarily think they are correct, but nor are we IMO.
I think the ideal would be to clip at the padding edge, like we do at the bottom,
but yeah, I understand that's going to be tricky given that the inner anonymous
block doesn't stretch that far.  But that's where the padding edge of the
*fieldset* should be as I see it, because that's where the border starts.
IOW, the vertical space that the legend incurs belongs to the padding area.

Comment 3

[Mats Palmgren (inactive)]

I don't feel strongly about it though; I think our current rendering is fine
for the time being, given that there's no spec for fieldset rendering.

Comment 4

[Boris Zbarsky [:bzbarsky]]

It seems to me that the clip edge should be in the same exact place for overflow:scroll and overflow:hidden...

Comment 5

[Mats Palmgren (inactive)]

Absolutely, I didn't mean to imply otherwise.

Comment 6

[Mats Palmgren (inactive)]

Attachment: Testcase #1

Comment 7

[Mats Palmgren (inactive)]

Attachment: Screenshot of Testcase #1 in IE10, Chrome33

Comment 8

[Mats Palmgren (inactive)]

The behavior in IE10 and Chrome33 seems identical.  The legend moves out of view
together with the content when I scroll.  That doesn't seem right.

Comment 9

[Mats Palmgren (inactive)]

One drawback with having the clip edge below the border is that the content
would appear under the (bottom half of) the legend when you scroll.
Hmm, so maybe the current layout is the best compromise after all...

Comment 10

[Mats Palmgren (inactive)]

One way of dealing with that overlap during scroll could be a fading/blurring effect
for the part under the legend so that it doesn't affect readability of the legend to much.
Seems like a lot of work for not much gain though, so I'm leaning towards wontfix.

Comment 11

[Robert O'Callahan (:roc) (email my personal email if necessary)]

Attachment: WIP

We can mostly fix this by laying out the fieldset's child at the top-left of the inner edge of the fieldset's border, and putting the space between the inner edge of the top border and the bottom of the legend into the fieldset's child's top padding.

border-radius is still a bit broken though.

This isn't all that important so I'm attaching my experiments here but not planning to work on this for now.

Comment 12

[Mats Palmgren (inactive)]

Attachment: Screenshot (Testcase #1 with WIP patch on Linux)

The rounded borders looks fine to me with that patch (on Linux) except
on the corners that meets with a scrollbar, but that problem also occurs
in Nightly so it seems like an existing problem.  This looks nice when
viewing the attached test, but when I change it to a default black-
on-white colors it does become a bit messy when scrolling.

Comment 13

[Robert O'Callahan (:roc) (email my personal email if necessary)]

Mats, you can review that WIP patch if you want. I'm just a little bit worried about it causing regressions that I don't really want to spend time fixing :-).

Comment 14

[Robert O'Callahan (:roc) (email my personal email if necessary)]

Actually I just noted comment #9, and I agree with you. WONTFIX!

Comment 15

[Mats Palmgren (inactive)]

It's a pity because I really like the clipping that patch implements.
It looks better and it feels more box model correct.

I've thought of ways to avoid the overlap, by default, but it's hard
because the legend and its siblings are normally in the same stacking
level.  I can think of two alternative solutions (and I'll write them
down here just for the record - I don't plan to work on it).

A. specify a default background in the UA sheet for the legend if it's
in a fieldset that is scrollable.  And give it some special priority in
the stacking context, above its normal flow siblings.

B. move the legend upward when scrolling occurs until its bottom edge
meets the fieldset padding edge, but not further.  That would avoid
the overlap, but it will make the top of the legend overflow the
fieldset frame, which might be a problem if the background above has
the same color as its text, making it unreadable.  That seems unlikely
though and a minor issue if it occurs.