:before pseudo-element causes gap in border - css

Question

I have this piece of HTML that I want to style.
The html is a table (and actual table), which I want to give a border.
The element also had a :before pseudo-element, which I use to put a small triangle in the top corner.
The JSFiddle is here.
I hope it makes sense. I stripped down the markup and the CSS as much as possible, because it's actually a small part of a big site.
http://jsfiddle.net/GolezTrol/28yDb/2/
Now the problem is that the combination of having 2 columns, having border-collapse: collapse; on the table and the :before pseudo element, cause the top border of the element to partially disappear. It's only there for the length of the first column.
You would assume that it is the pseudo element that is on top of the border, but this element is very small, and as far as I can tell, this could not be the problem. I added visibility: hidden; to the pseudo element to be sure, and I can tell that the triangle is gone, but the border is still incomplete.
Unfortunately I cannot change the markup, since this is outputted by MediaWiki, but I do have full control over the CSS.
The HTML:
<div id="globalWrapper">
<div id="column-content">
<div class="thumb tright">
<table class="infobox vcard" style="">
<tbody>
<tr>
<th colspan="2" class="fn org" style=""> Example text</th>
</tr>
<tr>
<th>Row head</th>
<td>Content</td>
</tr>
The CSS:
/* Generic table styling */
table {
border-collapse: collapse;
/*border-spacing: 0;*/ }
/* The box */
.thumb.tright table.infobox.vcard {
border: 3px solid #fae104;
position: relative;
}
/* Triangle */
.thumb.tright table.infobox.vcard:before {
content: "";
position: absolute;
width: 0;
height: 1px;
border-top: 5px solid transparent;
top: -7px;
border-left: 10px solid #555;
visibility: hidden;
right: -1px; }
I already found out that it works when I remove border-collapse: collapse;, but I'm not sure that is a proper solution, and even if it is, I would really like an explanation of what is going on.
Btw. I got this problem both in Chrome 29 and in Internet Explorer 10. Haven't tested other browsers.
Update
Instead of using -or not using- 'border-collapse' to fix the problem, I found out that this also works:
.thumb.tright table.infobox.vcard tbody {
display: block;
}
So the table itself is still a table, the pseudo element is still on the table, as is the border, positioning etc. The tbody, which was unstyled before, is now a block and the problem is solved in both browsers. I found this by trial and error, and still wouldn't know the reason behind it.
Updated fiddle: http://jsfiddle.net/GolezTrol/28yDb/9/

Answer 1

Being a newbie to StackOverflow and jsFiddle I updated the Fiddle with that I think is the solution. I didn't change the CSS except for moving the pseudo class from the table itself to the table header, and changing it into :after. Works for me in Firefox and Chrome!
/* Triangle */
.thumb.tright table.infobox.vcard th:after { }
Border-collapse: seperate is not supported in IE8 but I think this will be.
edit: nevermind ;)

Answer 2

It is a problem only occur on Webkit browsers I think. It can be considered a "browser bug" imo.
th should be inside thead, not tbody:
<thead>
<tr>
<th colspan="2" class="fn org" style=""> Example text</th>
</tr>
</thead>
<tbody>
<tr>
<th>Row head</th>
<td>Content</td>
</tr>
<tbody>
And I think this is the correct solution. You are putting an element where it is not advised to be, so it should be normal for a problem to occur.
Edit: as thirtydot pointed out, changing the th to td doesn't change the result. It only work when I moved the th to the thead section. At this point I am at a loss, I can't find a way to solve this.
But at least I think I can provide my speculation on the cause of this problem:
:before create a pseudo element inside the target element. What kind of element is unknown to me, but I suspect that the browser create a td. If that is true, then after rendering your html should look like this:
<table>
<td></td> /*the pseudo element*/
<tbody>
<tr>
<th colspan="2" class="fn org" style=""> Example text</th>
</tr>
<tr>
<th>Row head</th>
<td>Content</td>
</tr>
<tbody>
</table>
Needless to say this look weird. And if you try the above html out you can see the result is similar to your problem. border-collapse:collapse will merge 2 borders together where there are 2 cells next to each other, or a cell is next to the table's border. So I suspect in this case, the pseudo element - which doesn't have appropriate colspan - last only 1 column, the rest of that row is empty: nothing's there. This is where I think caused the bug: because there's no cells next to the table border there, no border is created at all.
The real reason may be a little bit more complicated ("why doesn't the bug occur when I put in a thead?"), but I think my answer is not too far off the mark. :)

Answer 3

The only reasonable explanation I can think of is pseudo-element :before not being compatible with the display: table of the table in collapsed mode. That is why border-collapse: separate; solves the problem. Suddenly, the browser can display the top border not caring about the pseudo element.
If you look closely, you can clearly see that the missing part of the border is the width of the second column. If you change it to after pseudo element, the border is missing in the bottom-right corner, again due to the fact that the borders of the table and the pseudo-element are collapsed.
If you change the border-bottom of th to be 3px solid red in collapsed mode, the th overpowers the table and the border is red. I presume, the power of after and before follow the same rule. It would be nice if someone who knows the specs better came to answer that.
Thinking this way, I do not believe there can be any other solution than:
using separate borders
putting the pseudo element on the parent div
What I inspected is that the pseudo element is actually rendered as block and can be change to table and list-item. However, none of these change the behaviour.
Very random stuff that is actually compliant with Av Avt's answer about where the pseudo element is rendered in regards of the DOM.
If I append the :beofre like this, the border stays:
.thumb.tright table.infobox.vcard tr:before
Obviously, it creates as many new pseudo element as there are rows.