Animating a CSS gradient background on the hover event - html

Question

I have some menu items that are styled using a background gradient on hover using the following styling:
#sidebar ul li a:hover {
background-image: linear-gradient(bottom, rgb(68,68,68) 5%, rgb(51,51,51) 100%);
background-image: -o-linear-gradient(bottom, rgb(68,68,68) 5%, rgb(51,51,51) 100%);
background-image: -moz-linear-gradient(bottom, rgb(68,68,68) 5%, rgb(51,51,51) 100%);
background-image: -webkit-linear-gradient(bottom, rgb(68,68,68) 5%, rgb(51,51,51) 100%);
background-image: -ms-linear-gradient(bottom, rgb(68,68,68) 5%, rgb(51,51,51) 100%);
background-image: -webkit-gradient(
linear,
left bottom,
left top,
color-stop(0.05, rgb(68,68,68)),
color-stop(1, rgb(51,51,51))
);
color: #f0f0f0;
border-top-left-radius: 4px;
border-bottom-left-radius: 4px;
}
My question is, is it possible to make the new background (defined by gradients) slide in from the right using CSS3 transitions or animations? Or will I have to resort to using a sprite image or Javascript?

Answer 1

Animation on gradients aren't supported yet. However this site provides a pleasing approach for a animated kind of feel on hover-
http://sapphion.com/2011/10/css3-gradient-transition-with-background-position/
Sample css:-
#DemoGradient{
background: -webkit-linear-gradient(#C7D3DC,#5B798E);
background: -moz-linear-gradient(#C7D3DC,#5B798E);
background: -o-linear-gradient(#C7D3DC,#5B798E);
background: linear-gradient(#C7D3DC,#5B798E);
-webkit-transition: background 1s ease-out;
-moz-transition: background 1s ease-out;
-o-transition: background 1s ease-out;
transition: background 1s ease-out;
background-size:1px 200px;
border-radius: 10px;
border: 1px solid #839DB0;
cursor:pointer;
width: 150px;
height: 100px;
}
#DemoGradient:Hover{
background-position:100px;
}

Answer 2

It seems gradients don't support transitions yet (still):
Use CSS3 transitions with gradient backgrounds
If you use a background image rather than a css3 gradient, then you can use css transition to animate it in and out.

Answer 3

Try this as a hack:
<div class="background-animate">
<div class="content">Hi im content</div>
</div>
And style it
.background-animate {
position: relative;
z-index: 10;
display: block;
background: transparent;
}
.background-animate:before {
content: "";
position: absolute;
transition: opacity .35s ease-in-out;
-moz-transition: opacity .35s ease-in-out;
-webkit-transition: opacity .35s ease-in-out;
top:0; left: 0; right: 0; bottom: 0; z-index:-1;
background: -moz-radial-gradient(center, ellipse cover, #ffffff 40%, #e9eae9 100%); /* FF3.6-15 */
background: -webkit-radial-gradient(center, ellipse cover, #ffffff 40%,#e9eae9 100%); /* Chrome10-25,Safari5.1-6 */
background: radial-gradient(ellipse at center, #ffffff 40%,#e9eae9 100%); /* W3C, IE10+, FF16+, Chrome26+, Opera12+, Safari7+ */
}
.background-animate:hover:before {
opacity: 0;
}
.background-animate:after {
content: ""; opacity: 0;
transition: opacity .35s ease-in-out;
-moz-transition: opacity .35s ease-in-out;
-webkit-transition: opacity .35s ease-in-out;
position: absolute;
top:0; left: 0; right: 0; bottom: 0; z-index:-1;
background: -moz-radial-gradient(center, ellipse cover, #ffffff 80%, #e9eae9 100%); /* FF3.6-15 */
background: -webkit-radial-gradient(center, ellipse cover, #ffffff 80%,#e9eae9 100%); /* Chrome10-25,Safari5.1-6 */
background: radial-gradient(ellipse at center, #ffffff 80%,#e9eae9 100%); /* W3C, IE10+, FF16+, Chrome26+, Opera12+, Safari7+ */
}
.background-animate:hover:after {
opacity: 1;
}
It basically does an opacity switch between to gradients. Demo found here https://codepen.io/anon/pen/eWOEoR