Monday, May 21, 2007, 12:44:51 AM, Daniel Dekany wrote:
> With an example:
>
> ...
> <foo>
> <bar>
> Blah
> </bar>
> </foo>
> ...
>
> If foo has a vertical margin A and bar has a vertical margin B, and
> neither elements have vertical padding or border, then the total
> vertical margin around the text should be max(A, B). But it seems that
> with XXE it's A + B instead.
Unfortunately, it seems the problem is not confined to vertical margin
collapsing between elements that are in parent-child relationship.
Here is another case (working example attached):
...
<foo>X1</foo>
<div>
<foo>X2</foo>
</div>
<foo>X3</foo>
<foo>X4</foo>
...
Here, when both "foo" and "div" is "display: block", and "foo" has
vertical margin of size M, and div has no margin (and neither element
has border, nor padding) the visual vertical distance between all the
"X" texts should be M. With XXE, the distance between X3 and X4 will
be M as expected, but will be 2 * M between X1 and X2, and also
between X2 and X3.
So, to recap, (CSS experts please correct me if I'm wrong) the CSS
rule is basically that if we have boxes in the normal-flow, then when
the vertical margin of them touches each-other (i.e. nothing separates
them, like another box or even padding or a border), the smaller
vertical margin will be eaten by the bigger one. It's irrelevant what
is the relation between the XML nodes for which the boxes were
generated. It only matters if the two boxes touch each other visually.
And please don't go into fights about the importance of this bug... I
didn't wanted that ever, I just initially taken granted that I'm
satiating the obvious. Like, probably the reason why the DocBook
itemizedlist/listitem-s has, well, at best strange vertical spacing
with XXE (and also maybe that you didn't attempted to implement
spacing="compact") is that the author of the style sheet have find it
too hard make it better (too hard considering that it's just for
editing anyway). The good news is that real CSS is not that hard to
work with when it comes to vertical distances. If you don't have to
afraid of vertical spaces stacking up, it's as easy to solve a quite
decent itemizedlist/listitem vertical spacing as it was creating the
current one, even a bit easier [*]. (It's logical why. Simplified, the
idea is that by saying "I want a vertical margin of 1.33ex", you just
say "I don't want anything visible to be closer to this thing
vertically than 1.33ex". And if it really just means that (but it
doesn't with XXE), then you can just drop the margins there like a
safety thing that can be only good. You don't have to wonder what can
possibly be next to the box visually that may already have a margin.)
* Like you don't have to explicitly erase the vertical margin of the
first child of the listitem. Nothing like that. Really, you just had
to say that listitems has 1.33ex vertical marging, and itemizedlist
have no vertical margin. Pretty trivial, and the result looks
satisfying even for a bastard like me.
--
Best regards,
Daniel Dekany
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