skrollr-stylesheets (v 0.0.4, yes, it's that hot)

Allows separation of skrollr keyframes and the document by putting them inside your stylesheets, in under 1kb (minified + gzipped). Works in all browsers including IE8+.

See https://github.com/Prinzhorn/skrollr for infos on skrollr.

Documentation

This is a completely separate project. skrollr-stylesheets does not depend on skrollr in any way. It parses your stylesheets (link and style elements) and adds the information to the document as skrollr compatible data-attributes. After skrollr-stylesheets did it's job, you can use skrollr they way you're used to, just as if you had put the data-attributes on the elements manually.

When I say "parsing" I mean it's using regular expressions. Thus you should avoid doing funky stuff inside your CSS files (actually, comments at the wrong place could break the current version). Just put all skrollr related things in one file and keep it clean.

skrollr-stylesheets borrows it's syntax from CSS animations and uses it's own -skrollr prefix. Here's an example which should explain everything to get you started with skrollr-stylesheets.

This HTML

<div id="foo"></div>

together with this CSS (inside any style or link)

#foo {
	-skrollr-animation-name:animation1;
}

@-skrollr-keyframes animation1 {
	0 {
		left:100%;
	}

	2000 {
		left:0%;
	}

	top {
		color:rgb(0,0,0);
	}

	bottom {
		color:rgb(255,0,0);
	}
}

results in this HTML

<div id="foo" data-0="left:100%;" data-2000="left:0%;" data-top="color:rgb(0,0,0);" data-bottom="color:rgb(255,0,0);"></div>

You can use any CSS selector you want because we are using document.querySelectorAll. And you can even have multiple declarations affect the same element. The lower they appear inside the stylesheet(s), the higher their priority gets.

The script

In order to use skrollr-stylesheets, just place dist/skrollr.stylesheets.min.js at the bottom of your page before the closing </body> (but before skrollr itself). skrollr-stylesheets will execute right when it's included and searches for all stylesheets and processes them synchronously.

skrollr-stylesheets doesn't expose or expect any globals (well, except for window and document, duh). You don't need to do anything but include the script.

External stylesheets

If you want skrollr-stylesheets to parse an external stylesheet (those using a link element), add an empty data-skrollr-stylesheet attribute to it.

Example

<link rel="stylesheet" type="text/css" href="style.css" data-skrollr-stylesheet />

Heads up: Since external stylesheets are fetched using AJAX (more like SJACSS, but that's not the point here) the same origin policy applies which prohibits AJAX requests when viewing files using the file:// protocol. Either fire up a local server (e.g. npm install http-server -g && http-server or php -S localhost:8080) or start Chrome using google-chrome --disable-web-security.

Media queries

You cannot use media queries inside your stylesheets. Parsing those would add another level of complexity to the code. Further more this would not fit the current philosophy of skrollr-stylesheets, which is to parse and apply the keyframes once on page load and then do nothing. Media queries would need to be evaluated at each resize and orientationchange.

But wait! You can use the media attribute on external stylesheets. But bare in mind that they are only evaluated once at page load.

Example

<link rel="stylesheet" type="text/css" href="style-large.css" media="only screen and (min-width: 1050px)" data-skrollr-stylesheet />

This feature relies on window.matchMedia. There is a matchMedia polyfill available that can be used with older browsers. Look at http://caniuse.com/#search=matchmedia for browser compatibility.

Sass

The above is already pretty awesome, but it gets even better. If you know skrollr, you probably heard about the constants feature. Let's admit it: it does it's job, but it's ugly.

Sass to the rescue! Using Sass variables and interpolation, things can now look like this:

$about_section_begin: 0;
$about_section_duration: 2000;
$about_section_end: $about_section_begin + $about_section_duration;

@-skrollr-keyframes animation1 {
	#{$about_section_begin} {
		left:100%;
		opacity#{"[swing]"}: 0.0;
	}

	#{$about_section_end} {
		left:0%;
		opacity: 1.0;
	}
}

*mind blown*

And of course you can use all the things you already love about Sass as well.

Note that easing functions need to be interpolated as strings in Sass because of the non-standard syntax.

Limitations

skrollr-stylesheets does not react to changes in the document. The stylesheets are parsed once and then applied. You can't add a class to an element and expect the keyframes to get updated.

skrollr-stylesheets tries to mimic the way normal CSS works in terms of inheritance and order of precedence. Stylesheets which appear lower in the document will have higher precedence, and inline keyframes will have precedence over everything else. That means if you declare the same keyframe with same properties (probably different values) in multiple places, they overwrite each other, just as normal CSS does. But skrollr-stylesheets is not able to detect which selector has a higher specificity. It only operates on element-level. Thus only the order of rules counts, not the specificity of the selector.

Changelog

0.0.4 (2013-05-27)

• Allow dashes in animation names just like in CSS animations (#18)

0.0.3 (2013-05-15)

• Added support for media attribute on external stylesheets.

0.0.2 (2013-04-12)

• Fixed several issues with IE.
• breaking: The logic of data-no-skrollr has been inversed. The attribute has been removed. Instead add data-skrollr-stylesheet to explicitly parse this external stylesheet.

0.0.1

• Initial "release". Features a reasonable amount of tests to at least let people play with it.