Vertically aligning CSS :before and :after content

问题:

I am trying to centre the link with the image, but can't seem to move the content vertically in any way.

<h4>More Information</h4>
<a href="#" class="pdf">File Name</a>

The icon is 22 x 22px

.pdf {
    font-size: 12px;
}
.pdf:before {
    padding:0 5px 0 0;
    content: url(../img/icon/pdf_small.png);
}
.pdf:after {
    content: " ( .pdf )";
    font-size: 10px;
}
.pdf:hover:after {
    color: #000;
}

回答1:

Answered my own question after reading your advice on the vertical-align CSS attribute. Thanks for the tip!

.pdf:before {
    padding: 0 5px 0 0;
    content: url(../img/icon/pdf_small.png);
    vertical-align: -50%;
}

回答2:

I'm no CSS expert, but what happens if you put vertical-align: middle; into your .pdf:before directive?

回答3:

You can also use tables to accomplish this, like:

.pdf {
  display: table;
}
.pdf:before {
  display: table-cell;
  vertical-align: middle;
}

Here is an example: https://jsfiddle.net/ar9fadd0/2/

EDIT: You can also use flex to accomplish this:

.pdf {
  display: flex;
}
.pdf:before {
  display: flex;
  align-items: center;
}

Here is an example: https://jsfiddle.net/ctqk0xq1/1/

回答4:

I think a cleaner approach is to inherit the vertical alignment:

In html:

<div class="shortcut"><a href="#">Download</a></div>

And in css:

.shortcut {
    vertical-align: middle;
}
.shortcut > a:after {
    vertical-align: inherit;
{

This way the icon will align properly in any resolution/font-size combination. Great for use with icon fonts.

回答5:

Messing around with the line-height attribute should do the trick. I haven't tested this, so the exact value may not be right, but start with 1.5em, and tweak it in 0.1 increments until it lines up.

.pdf{ line-height:1.5em; }

回答6:

I spent a good amount of time trying to work this out today, and couldn't get things working using line-height or vertical-align. The easiest solution I was able to find was to set the <a/> to be relatively positioned so it would contain absolutes, and the :after to be positioned absolutely taking it out of the flow.

a{
    position:relative;
    padding-right:18px;
}
a:after{
    position:absolute;
    content:url(image.png);
}

The after image seemed to automatically center in that case, at least under Firefox/Chrome. Such may be a bit sloppier for browsers not supporting :after, due to the excess spacing on the <a/>.

回答7:

I just found a pretty neat solution, I think. The trick is to set the line-height of image (or any content) height.

text

Using CSS:

div{
  line-height: 26px; /* height of the image in #submit span:after */
}

span:after{
    content: url('images/forward.png');
    vertical-align: bottom;
}

That would probably also work without the span.

回答8:

I had a similar problem. Here is what I did. Since the element I was trying to center vertically had height = 60px, I managed to center it vertically using:

top: calc(50% - 30px);