134518 - Incorrectly calculated value for margin-bottom (in conjunction with position: fixed?)

Status: RESOLVED DUPLICATE of bug 126213

(Core :: Layout, defect, P2)

Description

[mozilla]

From Bugzilla Helper:
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:0.9.9+)
Gecko/20020330
BuildID:    2002033009

In some cases, the value calculated for margin-bottom is not correct. Look at
the URL to see this problem: the left <div> (named 'foo') with a CSS 'height'
value is correctly displayed, the right <div> (named 'bar') without a given
'height' has a wrong bottom margin.

It seems as mozilla calculates the margin-bottom as follows:
  margin-bottom = margin-bottom + padding-top + padding-bottom + border-top +
border-bottom
(Maybe mozilla adds additional values which I have not tested.)

Reproducible: Always
Steps to Reproduce:
You can use the example in the URL to do some testing. Changing the CSS values
for padding or border also changes the bottom margin of the right <div>.

Comment 1

[Boris Zbarsky [:bzbarsky]]

What do you mean by "bottom margin of the right div"?  Do you mean "the 
location of the outer edge of the bottom border of the right div"?  If so, the 
padding and border widths _should_ affect the location of that border edge (see 
http://www.w3.org/TR/REC-CSS2/box.html#box-dimensions and note that "height" 
specifies the height of the content area only, from inner padding edge to inner 
padding edge) 

Comment 2

[mozilla]

The "bottom margin" of an element is the space below that element, which can be influenced by 
setting the 'margin-bottom' CSS property.

I set the offset from the bottom margin's edge to 
the bottom of the viewport to 0 for both <div>'s (see "bottom: 0px;" in the source). The width of all 
four margins should be 0 if I don't specify otherwise. But if I don't set a height for the element, as 
in the left <div>, mozilla will add a margin at the bottom, as happened with the right <div>, which 
is wrong.

Even if I explicitly set "margin-bottom: 0px;" for the right <div>, this element 
will not be displayed without a gap to the viewport bottom edge.

Comment 3

[Boris Zbarsky [:bzbarsky]]

Ah, I see what you mean.  Confirming bug.  This happens with absolutely
positioned elements too...

Comment 4

[Christine Hoffman]

Changing QA contact

Comment 5

[Boris Zbarsky [:bzbarsky]]

this is almost certainly bug 126213

Comment 6

[Boris Zbarsky [:bzbarsky]]

This is fixed by the patch in bug 126213

*** This bug has been marked as a duplicate of 126213 ***