Horizontal scrolling of sticky header doesn't working - html

Question

I have a sticky header on my page, but I found a bug that buttons on right side of sticky header is not visible when browser window is small... and horizontal scrolling does not work for hearder.
Here is html code:
<div class="search-container">
<div class="sticky-wrapper">
<!-- it's fixed header -->
</div>
<div class="sidebar">
<!-- search filters e.g. -->
</div>
<div class="content">
<!-- search results e.g. -->
</div>
</div>
Here is my CSS (sass) code:
.search-container {
.sticky-wrapper {
box-shadow: 0 3px 3px 0 #8f8f8f;
position: fixed;
top: 0;
z-index: 999;
}
.sidebar {
float: left;
margin-left: 5px;
width: 229px;
}
.content {
background: none repeat scroll 0 0 #fff;
border-top: 4px solid #5d5d5d;
display: inline;
float: left;
margin-left: 18px;
margin-right: 0;
width: 691px !important;
}
}
When I make browser window smaller then (sidebar + content) width, horizontal scrolling appears - but it works only for .sidebar and .content.
How can I make sticky header horizontal-scrollable too?
P.S. it's important to working in FF, Chrome, IE >= 9. And I it not good to change/add new css ids or classes, cause many tests become broken.
Please, help.
Thanks kindly.
If it will be helpful - jsfiddle with header and content

Answer 1

I think CSS alone cannot handle this scenario. It would be better if you add a pinch of JS flavour. Try this Fiddle.
Added a JS code: (Note: I have used JQuery, you can also have it rewritten in pure JS if required)
$(window).scroll(function() {
var max_width = 990;
if ($(window).width() < max_width) {
$('.sticky-wrapper').css('margin-left', -$(this).scrollLeft() + "px");
}
});

Answer 2

For what I could test, and for previous experience, is to add a div inside with a width bigger than the container one, and to that container add an overflow-x: auto;
For example:
<div class="sticky-wrapper">
<div class="bigger">Your text here</div>
</div>
.sticky-wrapper {
box-shadow: 0 3px 3px 0 #8f8f8f;
position: fixed;
top: 0;
z-index: 999;
background: grey;
width: 900px;
overflow-x: auto;
}
.bigger {
width: 1000px;
}
Fiddle: https://jsfiddle.net/afs5k1zp/1/