How to style element to overlap scroll

Question

I am working on an already existing project, with a pretty complex front end. I want to introduce a new element which should be a substitute for a dropdown. Basically it's a div bind with knockout to a collection.

The problem I have is that on a single page there are several divs inside which a more complex structure is rendered for each one, and inside one of this divs is my custom dropdown. The problem is that when I try to expand the dropdown (a class bind to a click event using jQuery) my "dropdown" is rendered up to the top of the div because of the fact that there is too much content and in order to preserve the entire page look and appearance there is no good way to use overflow: visible.

A snippet that pretty well introduce my problem is HERE :

$('.show-dropdown').click(function() {
if ($(this).next('.render-this').hasClass('hide-me')) {
 $(this).next('.render-this').removeClass('hide-me');
  } else {
  $(this).next('.render-this').addClass('hide-me');
  }

})

td {
  position: relative;
}

#top-div {
  width: 500px;
  max-width: 500px;
border: 1px solid black;
  max-height: 100px;
  overflow-y: auto;
white-space: nowrap;
}

#bottom-div {
  width: 500px;
  max-width: 500px;
border: 1px solid black;
  max-height: 100px;
    overflow-y: auto;

}

.show-dropdown {
  width: 120px;
  height: 40px;
  background-color: green;
}

.render-this {
  position: absolute;
  bottom: 10px;
  z-index: 5;
  width: 20px;
  height: 150px;
  background-color: red;
}
.hide-me {
  display: none;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div id="top-div">
<p>
lorem ipsum lorem ipsum lorem ipsum lorem ipsumlorem ipsumlorem ipsum lorem ipsum lorem ipsum
</p>
</div>
<div id="bottom-div">
<table class="w3-table">
<tr>
  <th>Column 1</th>
  <th>Column 2</th>
  <th>Column 3</th>
  <th>Column 4</th>
  <th>Column 5</th>
  <th>Column 6</th>
</tr>
<tr>
  <td><div class="show-dropdown"></div><div class="render-this hide-me"></div></td>
  <td><div class="show-dropdown"></div><div class="render-this hide-me"></div></td>
  <td><div class="show-dropdown"></div><div class="render-this hide-me"></div></td>
  <td><div class="show-dropdown"></div><div class="render-this hide-me"></div></td>
  <td><div class="show-dropdown">></div><div class="render-this hide-me"></div></td>
  <td><div class="show-dropdown"></div><div class="render-this hide-me"></div></td>
</tr>
</table>

I've read a lot about this topic. My conclusion so far is that if you have overflow it is pretty much game over. However from the question HERE I see that with transform and maybe some other CSS it might be still possible to achieve something. Also, what I need is to render my dropdown completely, I was also thinking about using overflow: visible and some sort of JS created scroll, but haven't dig deep for this still.

Answer 1

You can add a wrapper div with relative position around the scrollable container and then your absolute positioned dropdown would bind to that element. As you can see in this example.

css:

.position-relative {
    position: relative;
}

#top-div {
    width: 500px;
    max-width: 500px;
    border: 1px solid black;
    max-height: 100px;
    overflow-y: auto;
    white-space: nowrap;
}

#bottom-div {
    width: 500px;
    max-width: 500px;
    border: 1px solid black;
    max-height: 100px;
    overflow-y: auto;

}

.show-dropdown {
    width: 120px;
    height: 40px;
    background-color: green;
}

.render-this {
    position: absolute;
    bottom: 10px;
    z-index: 5;
    width: 20px;
    height: 150px;
    background-color: red;
}
.hide-me {
    display: none;
}

html:

<div class="position-relative">
    <div id="bottom-div">
        <table class="w3-table">
            <tr>
                <th>Column 1</th>
                <th>Column 2</th>
                <th>Column 3</th>
                <th>Column 4</th>
                <th>Column 5</th>
                <th>Column 6</th>
            </tr>
            <tr>
                <td>
                    <div class="show-dropdown"></div>
                    <div class="render-this hide-me"></div>
                </td>
                <td>
                    <div class="show-dropdown"></div>
                    <div class="render-this hide-me"></div>
                </td>
                <td>
                    <div class="show-dropdown"></div>
                    <div class="render-this hide-me"></div>
                </td>
                <td>
                    <div class="show-dropdown"></div>
                    <div class="render-this hide-me"></div>
                </td>
                <td>
                    <div class="show-dropdown">></div>
                    <div class="render-this hide-me"></div>
                </td>
                <td>
                    <div class="show-dropdown"></div>
                    <div class="render-this hide-me"></div>
                </td>
            </tr>
        </table>
    </div>
</div>

js

$('.show-dropdown').click(function() {
    if ($(this).next('.render-this').hasClass('hide-me')) {
        $(this).next('.render-this').removeClass('hide-me');
    } else {
        $(this).next('.render-this').addClass('hide-me');
    }
})

Then you can adjust the top, left, right, bottom properties as you wish.

Answer 2

If you change your CSS as follows, you can get this to work as you would like:

• Remove the position:relative; from your td.
• Use a different approach to make the #bottom-div expend to it's content, using display: table;, and also apply the position:relative; to it.
• all other css rules stay the same.

So, this is your new css:

#top-div {
  width: 500px;
  max-width: 500px;
border: 1px solid black;
  max-height: 100px;
  overflow-y: auto;
white-space: nowrap;
}

#bottom-div {
  width: 500px;
  max-width: 500px;
  border: 1px solid black;
  max-height: 100px;
  position: relative;
  display: table;
}

.show-dropdown {
  width: 120px;
  height: 40px;
  background-color: green;
}

.render-this {
  position: absolute;
  bottom: 10px;
  z-index: 5;
  width: 20px;
  height: 150px;
  background-color: red;
}
.hide-me {
  display: none;
}

Here is a link to a Fiddle with the new css.

Answer 3

Demo

https://jsfiddle.net/mg8zbr41/172/

(I hope this was the desired behaviour)

Explanation

The whole problem would have been solved if we were allowed to have overflow-x: auto and overflow-y: visible together. But we cannot do that (see this answer). So we use the following workaround.

1. If you want to have want the red div to pop out you cannot put position: relative parent. So we remove that first
2. Now bottom becomes relative to parent relative element i.e. body but we don't want that so we also remove bottom
3. Now we have top, right, bottom, left all as auto. So the elements placed below the green box as it would have been if it was static. The only difference is it pops out of the bottom box
4. Now we want it to be 10px above the green box for that we use translateY(calc(100% + 10px) * -1)
5. Now this works till there's no scrolling. When the div is scrolled the red box stays there and doesn't move with its green box, we need to fix that
6. This can be easily fixed if we know how much is the div scrolled. Suppose the div is scrolled by 100px towards left we'll shift the red box towards left by 100px
7. We cannot find scrollLeft without JS. I personally don't like JS intervention for styling. We cannot avoid it but at least we can make it more semantic by using css variables for communication between JS and CSS.
8. We use JS to update a --scroll-left css variable on #bottom-div with the scrollLeft value
9. Once we have --scroll-left we can now add translateX(calc(var(--scroll-left,0px) * -1))
10. Also we don't want the red box to pop out of the box horizontally. We cannot fix this by overflow: hidden because that would require position: relative. So we use clip-path: inset(-999px 0px -999px 0px).
11. Finally we achieved want we wanted. Phew.

Demerits:

1. Horizontal repositioning will be laggy in Firefox because of Scroll Lined Effects. Same might be the problem in mobile browsers

See also:

https://css-tricks.com/popping-hidden-overflow/ Source of inspiration for my answer but both (solution in the article and my solution) are quite different but same core approach