CSS: a simple layout won't work in CSS

L

liketofindoutwhy

Found it!  ;-)
Check this out for all possibilities:
<http://www.student.oulu.fi/~laurirai/www/css/middle/>
By:  Lauri Raittila


erik.j's solution doesn't work? really? coz it works for me... using
IE 7 and Firefox 2

this first version is the one that doesn't work:

<div style="border:1px solid blue;width:500px; margin: 0 auto">
<img style="border:1px dashed orange" src="pic.jpg" alt="pic">Hello
</div>

and then, just by adding vertical-align to the image:


<div style="border:1px solid blue;width:500px; margin: 0 auto">
<img style="border:1px dashed orange;vertical-align:middle"
src="pic.jpg" alt="pic">Hello
</div>

now it will work. this might be the simplest solution. why the
vertical-align is added to the image part... i think reading more on
inline elements is needed to fully understand it.
 
K

kenneth02394832

The same goes for text: (to vertically center the "Hello")

THIS WON'T WORK: even if you add style="vertical-align:middle" to the
outer div, it won't work either.

<div>
<span style="font-size:100px;">XY</span><span style="vertical-
align:middle">Hello</span>
</div>


THIS ALSO WON'T WORK: even if you add style="vertical-align:middle" to
the outer div, it also won't work either.

<div>
<span style="vertical-align:middle"><span style="font-size:
100px;">XY</span>Hello</span>
</div>


NOW if the vertical-align is added to the big text portion, now the
small text is vertically centered... this is wrecking my brain right
now

<div>
<span style="font-size:100px;vertical-align:middle">XY</span>Hello
</div>
 
B

Ben C

The same goes for text: (to vertically center the "Hello")

THIS WON'T WORK: even if you add style="vertical-align:middle" to the
outer div, it won't work either.

Vertical-align doesn't apply to blocks and isn't inherited, so no point
in ever applying it to a div unless you've changed the div to display:
inline or table-cell.
<div>
<span style="font-size:100px;">XY</span><span style="vertical-
align:middle">Hello</span>
</div>

The second span is vertically aligned with respect to the "strut" of its
container, which has normal font-size.

If you add vertical-align: middle to the _first_ span, then the second
one ends up roughly halfway up it.

The reason this is all so counterintuitive is that both spans are being
aligned to something that you can't see.

The affect of aligning the big span is to move the top edge of the
invisible imaginary inline parent which the second span is aligned
relative to, relative to the containing div. So the second span (which
is positioned relative to that imaginary inline parent) moves on the
screen.
THIS ALSO WON'T WORK: even if you add style="vertical-align:middle" to
the outer div, it also won't work either.

<div>
<span style="vertical-align:middle"><span style="font-size:
100px;">XY</span>Hello</span>
</div>

There too the word Hello is vertically aligned within its inline parent,
which since it doesn't have one, is this so called "strut" of the div.
That has normal line-height, so "Hello" doesn't move much.
NOW if the vertical-align is added to the big text portion, now the
small text is vertically centered... this is wrecking my brain right
now

<div>
<span style="font-size:100px;vertical-align:middle">XY</span>Hello
</div>

Yes exactly! It is very confusing.

I will try to explain again.

Vertical-align (on an inline box) aligns it with respect to its inline
parent. The obvious case in which this makes sense is when you nest one
span inside another. The two spans may have different font sizes.
Normally the inner span's baseline lines up with that of the larger one
(its inline parent), but you can move it up and down with
vertical-align. The obvious time you might want to do this is for super
or subscript.

If an inline element doesn't have an inline parent (because its parent
is a block), then it's treated as though it had an inline parent anyway,
with the font-size that applies to the block. That imaginary inline
parent is called the "strut".

In this case, the strut is not particularly tall-- it has font-size:
normal. The first span, the one containing XY, is lined up so that its
middle is at the middle of the strut.

The second span is lined up with its baseline at the strut's baseline.
So why does the second span move up? Because the alignment of the first
span causes the line box top edge to move down relative to the
strut's baseline.

Once both the spans have been lined up with respect to the strut, then a
bounding box is drawn around the whole lot. That's the line box. The
line box sits in the div with its top edge at the top of the div.

The first span is the biggest thing on the line. It's therefore what
determines the height of the line box. If it's vertical-align: baseline,
it pushes the top of the line box up more than it pushes the bottom of
it down. If it's vertical-align: middle, it pushes the top up less and
the bottom down more.

Here are some diagrams: http://tidraso.co.uk/misc/vertical-align.html
 
G

Gus Richter

erik.j's solution doesn't work? really? coz it works for me... using
IE 7 and Firefox 2

When I clicked on the link provided, it brought me to the version using
overflow: hidden; and this one did not work.

The one also discussed by Ben and Neredbojias works.
 
N

Neredbojias

It works great except that in the div these two items are not needed:
line-height:100%;vertical-align:middle;

Precisely. I just threw vertical-align:middle; on the image on the OP's
original markup without carefully checking all his mistakes, but I probably
should have removed those in the example.
 
G

Gus Richter

Ben said:
Vertical-align doesn't apply to blocks and isn't inherited, so no point
in ever applying it to a div unless you've changed the div to display:
inline or table-cell.


The second span is vertically aligned with respect to the "strut" of its
container, which has normal font-size.

If you add vertical-align: middle to the _first_ span, then the second
one ends up roughly halfway up it.

The reason this is all so counterintuitive is that both spans are being
aligned to something that you can't see.

The affect of aligning the big span is to move the top edge of the
invisible imaginary inline parent which the second span is aligned
relative to, relative to the containing div. So the second span (which
is positioned relative to that imaginary inline parent) moves on the
screen.


There too the word Hello is vertically aligned within its inline parent,
which since it doesn't have one, is this so called "strut" of the div.
That has normal line-height, so "Hello" doesn't move much.


Yes exactly! It is very confusing.

I will try to explain again.

Vertical-align (on an inline box) aligns it with respect to its inline
parent. The obvious case in which this makes sense is when you nest one
span inside another. The two spans may have different font sizes.
Normally the inner span's baseline lines up with that of the larger one
(its inline parent), but you can move it up and down with
vertical-align. The obvious time you might want to do this is for super
or subscript.

If an inline element doesn't have an inline parent (because its parent
is a block), then it's treated as though it had an inline parent anyway,
with the font-size that applies to the block. That imaginary inline
parent is called the "strut".

In this case, the strut is not particularly tall-- it has font-size:
normal. The first span, the one containing XY, is lined up so that its
middle is at the middle of the strut.

The second span is lined up with its baseline at the strut's baseline.
So why does the second span move up? Because the alignment of the first
span causes the line box top edge to move down relative to the
strut's baseline.

Once both the spans have been lined up with respect to the strut, then a
bounding box is drawn around the whole lot. That's the line box. The
line box sits in the div with its top edge at the top of the div.

The first span is the biggest thing on the line. It's therefore what
determines the height of the line box. If it's vertical-align: baseline,
it pushes the top of the line box up more than it pushes the bottom of
it down. If it's vertical-align: middle, it pushes the top up less and
the bottom down more.

Here are some diagrams: http://tidraso.co.uk/misc/vertical-align.html

Great stuff Ben. Where did you get this "strut" thing from? Sounds like
something for my car.
 
B

Ben C

Ben C wrote: [...]
Great stuff Ben. Where did you get this "strut" thing from? Sounds like
something for my car.

It's mentioned in the CSS specification. Apparently it's a TeX term.
 

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