GitHub-Style Sliding Links

GitHub seems to change a lot but not really change at all, if that makes any sense; the updates come often but are always fairly small. I spotted one of the most recent updates on the pull request page. Links to long branch names now have their text visually truncated, and upon hover, the text animates to its full value. The CSS to accomplish this task is fairly simple, so let me show you how to make this happen!

The HTML

Adding an A element is obvious but less obvious is that the element must be wrapped with another element (you'll see why in the CSS section):

<p class="github-branch-wrap">
	Pull request from: <a href="" class="github-branch">david-walsh-test-branch-name</a>
</p>

Simples.

The CSS

The wrapping element requires a max-width and position of relative:

.github-branch-wrap {
	max-width:690px;
	position:relative;
}

The animation centers around CSS transitions and the max-width property paired with overflow:

.github-branch {
	position: relative;
	height: 24px;
	display: inline-block;
	top: 7px;
	padding: 0 7px;
	background: #444;
	background: -moz-linear-gradient(#444, #222);
	background: -webkit-linear-gradient(#444, #222);
	-ms-filter: "progid:DXImageTransform.Microsoft.gradient(startColorstr='#444444',endColorstr='#222222')";
	border: 1px solid black;
	border-radius: 3px;
	color: white;
	font-family: Consolas,"Liberation Mono",Courier,monospace;
	font-size: 13px;
	line-height: 24px;
	text-overflow: ellipsis;
	overflow: hidden;
	white-space: nowrap;
	vertical-align: top;
	z-index: 100;
	
	max-width: 125px;
	transition: .2s max-width linear;
	-o-transition: .2s max-width linear;
	-moz-transition: .2s max-width linear;
	-webkit-transition: .2s max-width linear;
	-ms-transition: .2s max-width linear;
}

/* Transition to complete width! */
.github-branch:hover, .github-branch:active {
	max-width: inherit;
}

Also note the nice touch of text-overflow:ellipsis -- this adds the "..." during the plain state.

I didn't like the effect at first, but it's grown on me, and actually does have some value. There's definitely some clever thought behind the effect, and it's the the type of effect I admire: simple but purposeful. Well done GitHub devs!