Div with position absolute having innerwidth of div with scrollbar - html

Question

The last two days I've been reading most questions here and a lot more about 'fill remaining width' and 'escaping overflow: hidden', but I can't get my problem solved. At the moment, I seriously doubt if it is possible at all.
I have a scrolling box with full body width. On top of that I have a absolute positioned header that I need to make the exact same width as the scrollbox. My intention is to make the header 0px or (if needed) 1px in height and let the content overflow.
Here is a fiddle.
The scrollbox has a scrollbar (always visible), the header obviously not. To compensate for that, I float a fake scrollbar to the right inside the header container, and left of that a <div> filling the remaining width (being exactly the innerwidth of the scrollbox).
HTML
//THE SCROLLBOX
<div id="scrollbox">
<div id="center2">
content<br>content<br>...
</div>
</div>
// THE HEADER
<div id="header_box">
<!--- FAKE SCROLLBAR -->
<div id="scroller">
<div></div>
</div>
// REMAINING WIDTH
<div id="container">
<div id="FIRST">
<div id="FIRST_banner"></div>
</div>
</div>
<div id="SECOND">
<div id="SECOND_banner"></div>
</div>
</div>
</div>
CSS
#header_box {
background: yellow;
position: absolute;
left: 0;
top: 0;
right: 0;
height: 25px;
width: 100%;
overflow: visible;
}
#scroller {
float: right;
overflow-x: hidden;
overflow-y: scroll;
height: 50px;
width: auto;
/* visibility: hidden; */
}
#scroller>div {
width: 0px;
height: 101%;
}
#container {
display: inline;
width: auto;
height: 50px;
overflow: visible;
}
#FIRST {
position: relative;
overflow: hidden;
height: 25px;
background: pink;
}
#FIRST_banner {
position: absolute;
top: 0;
left: 50%;
height: 220px;
width: 30px;
background: crimson;
}
#SECOND {
background: darkcyan;
position: relative;
height: 5px;
}
#SECOND_banner {
position: absolute;
top: 0;
left: 50%;
height: 220px;
width: 30px;
background: blue;
}
The problem lies in the div (#FIRST) with remaining width. From all the solutions I've read only the one with
position: relative;
overflow: hidden;
works for me. It gives the exact width, lining up the center of the header and the scrollbox nicely. But I can't break out of the overflow: hidden, so it cuts off the content.
So my second thought was: wrap #FIRST in a #container and let the child determine the width of the parent. After that, I can put another div (#SECOND) inside the container with the width of the parent. It works partially. The #container has the width intended, and the #SECOND div overflows nicely but takes on the width of #header_box, as no width is set on the parent itself.
So, my questions:
Can I somehow break out of the overflow: hidden of the FIRST div? (In that case the container and second div can be removed).
Is there a way to let the SECOND div obey the width of it's parent.
Some totally different solution.
Sadly there is a catch to this all:
css only
no javascript
no flexbox
Thanks voor any toughts.

Answer 1

In the end, it was the good old <table> that saved the day, much simpler than I tought. There still is a fake scrollbar, but the absolute header now aligns perfect with the contents of the scrollable div behind it, and it remains fluid.
See fiddle here
HTML:
<!--- HEADER -->
<div id="THIRD">
<div id="THIRD_A">
<div id="THIRD_B"></div>
<div id="THIRD_C"></div>
<div id="THIRD_D"></div>
</div>
</div>
<!--- FAKE SCROLLBAR -->
<div id="scroller">
<div></div>
</div>
</div>
CSS:
/* The container for the header */
#header_box{
position: absolute;
left: 0;
top: 0;
right: 0;
height: 0px;
width: 100%;
overflow: visible;
display: table;
}
/* Takes on the width of its child: the fake scrollbar */
#scroller {
display: table-cell;
float: right;
overflow-x: hidden;
overflow-y: scroll;
height: 0px;
width: auto;
}
/* This triggers a scrollbar to be shown */
#scroller>div {
width: 0px;
height: 101%;
}
/* The 'remaining width' container (= screenwidth - scrollbar, equals innerwidth of scrollbox) */
#THIRD{
display: table-cell;
width: 100%;
height: 0px;
}
/* Needed to give the children a 'width' reference */
#THIRD_A{
position: relative;
width: 100%;
height: 0px;
}
/* The actual header items */
#THIRD_B {
position: absolute;
top: 0;
left: 50%;
width: 25px;
height: 220px;
background: black;
}
#THIRD_C {
position: absolute;
top: 0;
left: 10%;
width: 125px;
height: 120px;
background: black;
}
#THIRD_D {
position: absolute;
top: 0;
right: 0%;
width: 25px;
height: 220px;
background: black;
}
NOTE:
On most handheld browser, this is 1px off. It seems webkit based browsers display a tablecell of 0px width as 1px width (see this question). The solution is to wrap the table in another div with css:
position absolute;
left: 0;
right: -1px
and setting #scroller>div to a width of 1px.
NOTE 2:
This is also a solution for a fixed div inside a scrollable div. See this fiddle