35554 - CSS2 borders displaying on components with no height

Status: VERIFIED FIXED

(Core :: Layout, defect, P3)

Description

[Andrew Thompson]

Please see the two attachments I'm going to add:
simplified.html
and 
simplified.css

You have have to download these to disk to see the example.

There seems to be something rather odd going on with the handling of the height 
and max height on fixed position elements...

The example shows two nested fix position elements, the outer div is green, the 
inner one is orange, but its sized in such as way so that you can't see any 
green.
The red and yellow DIVs merely serve to show how the white borders on the inner 
orange div are behaving.

The immediate bug is this:

The orange div has max-height: 100%;

However this is being rendered incorrectly - as the DIV has no content it has no 
intrinsic height. Max height according to CSS2 sections 10.7 and 10.6.4 max-
height should only come into play if the ordinary computed height is greater than 
the max-height. This cleary cannot be the case for a div with no intrinsic 
height.

Mr Baron (see cc: above) believes the correct rendering for this test case is for 
no orange to be visible at all.

Further - if one changes max-height:100% to height:100% the display does not 
change. This would imply max-height is being treated as height. 

If further evidence is needed, try removing all reference to height/max-height 
from the orange div - it collapses away to nothing - well almost - the bottom 
border is still displayed! This does not seem right. Especially since if one also 
turns off the bottom border, no part of the right border is seen in the green 
box. All in all, its pretty inconsistent when dealing with height and width.


[As an aside - I don't like the way that the horizontal right border renders 
inside the orange div, but the vertical bottom border renders outside it. Mr 
Baron has convinced me that this is correct behaviour when "height:100%;" is set, 
because height refers to the content height and the box is over constrained if 
its content is 100% and it has borders, so they spill outside. It remains ugly 
when compared to the rendering of the right border though. This is pretty much 
unrelated to the actual bug report.]

Comment 1

[Andrew Thompson]

Apologies. Forgot to say build is Netscape 6 pr1	platform is Mac OS 9 but I 
would suspect this is fundamental to the Mozilla CSS implementation and applies 
to all platforms and recent builds.

Comment 2

[Andrew Thompson]

Attachment: Test case showing odd max-height handling

Comment 3

[Andrew Thompson]

Attachment: Stylesheet accompanies above HTML page

Comment 4

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

Confirming bug and changing component to Layout and reassigning.  Also changing
from Mac/Mac9.0 to All/All since I've seen this on a Linux build from a few days
ago.

There's a similar bug relating to replaced elements somewhere (but I forget
whether it's max-width or max-height).

Comment 5

[troy]

Fixed. Now no orange is visible

Comment 6

[Andrew Thompson]

Confirm max-height bug fixed as of build 200041915

However, if you look at the attached example in this build, you can see the 
other problem mentioned, the border display, is still there...

i.e. now the max-height is being collapsed to 0 as required, but the bottom 
border is still visible (at the top of the green area there's a white strip - 
this is the bottom border of the orange region,(the orange region that now has 
no height)).

This is inconsistent with the way that left and right borders are handled.
If one alters the orange div to have only a right border (by deleting the 
bottom border) one can see no part of this right border.

Whether this is a bug as far as the spec is concerned or merely cosmetic I 
don't know, but it seems symptomatic of something inconsistent in the handling 
of left/right top/bottom borders...

Comment 7

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

The border handling makes perfect sense.  When there's no height, and only a
right border, the right border should have 0 length.  But when there's no height
and a bottom border, the border should be the length of the width.

Comment 8

[troy]

David beat me to it, but that's exactly what I was gong to say as well. marking 
FIXED again, because the max-height issue has been fixed

Comment 9

[Chris Petersen]

Marking verified fixed in the May 22nd build.