<div class="example-cntr backdrop">
<h1>CSS <code>::backdrop</code> pseudo-element</h1>
<p>The <code>::backdrop</code> pseudo-element is a box that the full screen element has behind it, but at the same time it sits above all other content.</p>
<p>It can be used together with the <code>:fullscreen</code> pseudo-class or the <code><dialog></code> HTML5 element to change the background color of the maximized screen, just in case we don’t want to go with the default black.</p>
<div class="notes">
<h2>A few notes to consider:</h2>
<ol>
<li>It’s mandatory to use double colon with the <code>::backdrop</code> pseudo- element, it doesn’t work with single colon like with other pseudo-elements.</li>
<li>Edge is the only one that shows any styling of the <code>::backdrop</code> pseudo-element in this demo.</li>
<li>Firefox 47 (<a href="https://developer.mozilla.org/en-US/Firefox/Releases/47" target="_blank" title="Links opens in a new tab">release date June 29, 2016</a>) will start supporting the <code>::backdrop</code> pseudo-element.</li>
<li>Also, <a href="http://caniuse.com/#search=dialog" target="_blank"
title="Links opens in a new tab">no current version of Firefox supports the <code><dialog></code></a> HTML5 element.</li>
<li>Chrome doesn’t style the <code>::backdrop</code> pseudo-element when used with the <code>:fullscreen</code> pseudo-class even though <a href="https://developer.mozilla.org/en-US/docs/Web/CSS/::backdrop#Browser_compatibility" target="_blank"
title="Links opens in a new tab">MDN states that Chrome does support it </a>if prefixed with <code>-webkit-</code>. This is for Example 1.</li>
<li>Chrome properly styles the <code>::backdrop</code> pseudo-element when used with the <code><dialog></code> HTML5 element. This is for Example 2.</li>
<li><a href="http://caniuse.com/#search=dialog" target="_blank"
title="Links opens in a new tab">Only Chrome supports the <code><dialog></code></a> HTML5 element at the moment.</li>
<li>No mobile device supports the <code>::backdrop</code> pseudo-element.</li>
</ol>
</div>
<div class="example">
<h2>Example 1: Using <code>:fullscreen</code></h2>
<h1 id="element"><span class="hide">The text is injected via CSS</span></h1>
<button onclick="var el = document.getElementById('element'); el.webkitRequestFullscreen();">Trigger Full Screen!</button>
</div>
<div class="example">
<h2>Example 2: Using <code><dialog></code></h2>
<dialog>
<h1>This is a dialog. Good job! :]</h1>
<p>Press <code>ESC</code> or click on Close button.</p>
<hr>
<button id="close">Close</button>
</dialog>
<button id="show">Open Dialog!</button>
</div>
</div>
//Example 1
#element {
border-bottom: none;
background: none;
//Content in "normal" mode.
&:before {
content: 'Normal mode';
}
//Content in fullscreen mode
&:fullscreen:before {
content: 'Fullscreen mode';
}
&:fullscreen::backdrop {
background: $b;
}
//According to MDN we need to prefix, but it doesn't work in my tests.
&:fullscreen::-webkit-backdrop {
background: $b;
}
}
//Example 2
dialog {
width: 350px;
padding: 40px;
border: 1px solid rgba(black,.3);
border-radius: 2px;
box-shadow: 0 5px 20px black;
top: 30%;
}
dialog::backdrop {
position: fixed;
top: 0;
left: 0;
right: 0;
bottom: 0;
background: rgba(darken($g,25),.8);
}
//Styling stuff not needed for demo
body {
text-align: left;
line-height: 1.5;
}
h1 {
font-size: 22px;
text-transform: none;
border-bottom: #636363 1px dotted;
code {
display: inline-block;
margin-bottom: 10px;
color: $y;
background: none;
box-shadow: none;
}
}
h2 { font-size: 18px; }
code { font-size: 1em; }
.example-cntr {
max-width: 800px;
margin: 0 auto 50px;
padding: 30px;
box-shadow: 0 1px 2px rgba(black,.3);
background: rgba(black,.15);
& > code {
display: block;
margin-bottom: 10px;
font-size: 22px;
color: $y;
background: none;
box-shadow: none;
}
}
.underline { text-decoration: underline; }
//
.hide { display: none; }
#element {
border-bottom: #444 1px solid;
padding-bottom: 20px;
&:before {
display: block;
padding: 5px 0;
background: $g;
}
&:fullscreen:before {
display: block;
padding: 5px 250px;
background: $r;
}
}
button {
padding: 8px 15px;
cursor: pointer;
background: linear-gradient(white, #aaa);
border-radius: 2px;
&:hover { background: white; }
&:active { background: linear-gradient(#aaa, white 20%);}
}
.note {
color: desaturate($y,30);
font-size: 12px;
letter-spacing: .5px;
}
.notes {
margin-bottom: 20px;
padding: 20px 20px 0;
border: #444 1px solid;
border-radius: 3px;
h2 { margin: 0; }
}
.example {
margin: 0 20px;
padding: 20px;
background: rgba(black,.2);
margin-bottom: 20px;
&:last-child { margin-bottom: 0; }
h1 { border: none !important; margin-bottom: 0 !important; }
h2 { margin-top: 0; }
}
dialog {
text-align: center;
p { text-align: left; }
}
View Compiled
//Trigger the dialog box
var dialog = document.querySelector('dialog');
document.querySelector('#show').onclick = function() {
dialog.showModal();
};
document.querySelector('#close').onclick = function() {
dialog.close();
};
/* More information about the <dialog> element here: http://demo.agektmr.com/dialog/ */
This Pen doesn't use any external JavaScript resources.