Prevent gradient overlay from scrolling

Question

I am trying to put a small gradient on the bottom of a scrolling div. I've based my solution on the accepted answer to this SO thread. The gradient shows up fine, but when I scroll the content in the div, the bottom of the gradient moves. I need it to remain in place so that the content scrolls independently of the gradient. I've tried several combinations of position: fixed, position: relative, and position: relatve to no avail. What have I missed?

Relevant markup:

<div class="resultListContainer">
    <ul class="result">
        <li><span class="resultPermitNumber resultElement">B123456789</span></li>
        <li><span class="resultPermitType resultElement">FINAL</span></li>
        <li><span class="resultDisplayAddress resultElement">41975 LOUDOUN CENTER PL SE, LEESBURG, VA 20175</span></li>
    </ul>
    <!-- Lots more of the ul. -->
</div>

Relevant CSS:

.resultListContainer {
    border: 1px solid #000;
    height: 400px;
    width: 40em;
    overflow-y: scroll;
    font-size: 1em;
    position: relative;
}

.resultListContainer::before {
    background-image: linear-gradient( top, rgba( 255, 255, 255, 0 ) 0%, rgba( 255, 255, 255, 1 ) 100% );
    background-image: -moz-linear-gradient( top, rgba( 255, 255, 255, 0 ) 0%, rgba( 255, 255, 255, 1 ) 100% );
    background-image: -ms-linear-gradient( top, rgba( 255, 255, 255, 0 ) 0%, rgba( 255, 255, 255, 1 ) 100% );
    background-image: -o-linear-gradient( top, rgba( 255, 255, 255, 0 ) 0%, rgba( 255, 255, 255, 1 ) 100% );
    background-image: -webkit-linear-gradient( top, rgba( 255, 255, 255, 0 ) 95%, rgba( 255, 255, 255, 1 ) 100% );
    content: "\00a0";
    height: 100%;
    position: absolute;
    width: 100%;
}

.result {
    margin-bottom: 0;
    padding-top: 5px;
    padding-bottom: 5px;
    padding-left: 5px;
    list-style-type: none;
}

The result:

score 4 · Answer 1 · answered Mar 04 '16 at 17:24

Because your element is positioned absolute, it's position is absolute to the parent element so when you scroll it scrolls with your content. What you want is your ul to scroll. I have quickly rewritten yours, but below I've got a simplified and cleaned up version:

.resultListContainer {
    border: 1px solid #000;
    height: 400px;
    width: 40em;
    font-size: 1em;
    position: relative;
}

.resultListContainer::before {
    background-image: linear-gradient( top, rgba( 255, 255, 255, 0 ) 0%, rgba( 255, 255, 255, 1 ) 100% );
    background-image: -moz-linear-gradient( top, rgba( 255, 255, 255, 0 ) 0%, rgba( 255, 255, 255, 1 ) 100% );
    background-image: -ms-linear-gradient( top, rgba( 255, 255, 255, 0 ) 0%, rgba( 255, 255, 255, 1 ) 100% );
    background-image: -o-linear-gradient( top, rgba( 255, 255, 255, 0 ) 0%, rgba( 255, 255, 255, 1 ) 100% );
    background-image: -webkit-linear-gradient( top, rgba( 255, 255, 255, 0 ) 95%, rgba( 255, 255, 255, 1 ) 100% );
    content: "\00a0";
    height: 100%;
    position: absolute;
    width: 100%;
  z-index: 2;
  pointer-events: none;
}

.result {
  position: absolute;
  left: 0;
  top: 0;
  margin: 0;
  box-sizing: border-box;
  z-index: 1;
    width: 100%;
    height: 100%;
    margin-bottom: 0;
    padding-top: 5px;
    padding-bottom: 5px;
    padding-left: 5px;
    list-style-type: none;
    overflow-y: scroll;
}

.result li {
  height: 100px;
  background: red;
}

<div class="resultListContainer">
    <ul class="result">
        <li><span class="resultPermitNumber resultElement">B123456789</span></li>
        <li><span class="resultPermitType resultElement">FINAL</span></li>
        <li><span class="resultDisplayAddress resultElement">41975 LOUDOUN CENTER PL SE, LEESBURG, VA 20175</span></li>
        <li><span class="resultPermitNumber resultElement">B123456789</span></li>
        <li><span class="resultPermitType resultElement">FINAL</span></li>
        <li><span class="resultDisplayAddress resultElement">41975 LOUDOUN CENTER PL SE, LEESBURG, VA 20175</span></li>
        <li><span class="resultPermitNumber resultElement">B123456789</span></li>
        <li><span class="resultPermitType resultElement">FINAL</span></li>
        <li><span class="resultDisplayAddress resultElement">41975 LOUDOUN CENTER PL SE, LEESBURG, VA 20175</span></li>
    </ul>
    <!-- Lots more of the ul. -->
</div>

Basically there are two things that are important: your outer box cannot be scrollable, you inner box can. All the fixed elements need to be outside your inner box (which is your ul in this case). Secondly, your :before cannot be 100% high, as it will absorb your mouse events, preventing scrolling. For all browsers except IE you can solve this by using pointer-events: none, but otherwise the safest way is to make your gradient a fixed height and your :before element the height of the gradient you want, resulting in a (in this case) 20px area that would not take your mouse events at the bottom.

html, body { height: 100%; } body { padding: 0; margin: 0; }
div {
  width: 400px;
  height: 400px;
  max-height: 100%;
  position: relative;
}

div:before, div ul {
  position: absolute;
  left: 0;
  bottom: 0;
  width: 100%;
}

div:before {
  background: linear-gradient(0deg, rgba(255,255,255,1), rgba(255,255,255,0));
  background-size: 100% 100%;
  height: 20px;
  z-index: 2;
  /* IE does not support pointer events, so making this small in height is important
  as your scroll events will not be passed to the ul if it is covered by your :before */
  pointer-events: none;
  content: '';
  display: block;
}

div ul {
  margin: 0;
  padding: 0;
  height: 100%;
  overflow-y: scroll;
  z-index: 1;
}

div li {
  width: 100%;
  height: 100px;
  background: #ececec;
}

div li:nth-child(2n){
  background: #cecece;
}

<div>
    <ul>
        <li>1</li>
        <li>2</li>
        <li>3</li>
        <li>4</li>
        <li>5</li>
        <li>6</li>
        <li>7</li>
    </ul>
</div>

score 1 · Accepted Answer · answered Mar 04 '16 at 17:31

1

You need to wrap your container in another div that is positioned as relative.

Also, overlay will block your scroll bar, so instead of width: 100% I used: left:0; right: 16px; - now scroll is clickable.

Try my fiddle: https://fiddle.jshell.net/8c6k4k6d/1/

answered Mar 04 '16 at 17:31

Kocik

494
2
17

The answer provided by @somethinghere is awesome and in-depth and taught me a few things, but @Kocik directly answers my question (for example, @somethinghere changes the structure of my layout to have just one `
– mrcoulson Mar 11 '16 at 19:57

score 0 · Answer 3 · answered Mar 04 '16 at 17:12

0

replace

.resultListContainer::before

with

.resultListContainer .result:last-of-type::before

answered Mar 04 '16 at 17:12

Emirhan Özlen

474
2
14

This one exchanges the gradient for a large white empty area after the last `ul.result`. – mrcoulson Mar 04 '16 at 17:20

Prevent gradient overlay from scrolling

3 Answers3

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