This is a fork of impress.js that adds sub-step capability. For documentation on everything else about impress.js, read that documentation.

You can see an example of this code in action here: http://tehfoo.github.io/impress.js

This is pretty easy. There are two parts, the HTML part and the CSS part.

Just like impress.js, you really only need the impress.js file. You can learn all about using impesss.js by viewing the source of the main index.html file. This just builds on what is already there, and doesn't break anything... I think ;)

This is pretty simple. In an element marked with the step class, you can add the substep class to whatever elements you want to be a substep. On init, the modified impress.js script will find all elements with class substep, and mark them with the class future. This is just like regular steps.

As you navigate forward or backward through your steps, any substep found will be treated as a navigation step. While viewing an element with substeps, navigation forward finds the next substep, swapping future for present and active. When a moving forward from a substep, the present substep has present removed, and the class past is added. This is much like the behavior for steps. If there are no more substeps ahead, the navigation moves to the next step.

An important key difference between regular steps and substeps is that substeps keep their active class when they are marked as past. This is different from regular steps, which have the active class removed when they are marked as past. I might make this behavior configurable in the future.

The reverse is applied when navigating backward; if there are substeps they last one will get focus, which adds removes past and adds present. Continue backward, and both present and active classes are removed, while the class future is set. If there is another substep, that gets focus and is treated as above. If there are no more substeps, backward navigation moves to the previous step.

To get all this magic on, all you have to do is set the substep class on whatever you want to have act as a substep. Of course, this has to be withing a step enabled element.

Example

<div id="introduction" class="step" data-x="0" data-y="0">
  <h1 class="line">Can Haz Substep?</h1>
    <ul>
      <li class="substep">Sure!</li>
      <li class="substep">Why Not?</li>
      <li class="substep">Just Add the Substep Class</li>
      <li class="substep">And Amaze Friends</li>
      <li class="substep">With Substep Goodness</li>
    </ul>
  </div>

That will get you substep elements with CSS classes that change as you navigate. Now you need to style them.

To put the substeps to work, you need to style them. They don't really do anything by default. You might be thinking 'Y U NO HIDE AS DEFAULT?'. Ask me that later. This is easy to make work with some CSS.

A simple (and possibly 'Powerpointish') behavior is to set the substep opacity: 0 by default, and then transition them to opacity: 1 when they are active.

Example

.impress-enabled .substep {
  opacity: 0;
  -webkit-transition: all 1s;
  -moz-transition:    all 1s;
  -ms-transition:     all 1s;
  -o-transition:      all 1s;
  transition:         all 1s;  
}

.impress-enabled .substep.active {
  opacity: 1;
}

.impress-enabled .substep.present { 
  color: rgb(100, 135, 195);
}

This would style the HTML example above to have substeps hidden by default, become visible when a substep becomes active, and get colored when the substep becomes present. All the property changes get a 1 second transition.

If you need more help, try viewing source on the substep.html example file, and looking at the substep.css as well.

See this exact code working here: http://tehfoo.github.io/impress.js

You may notice there is no default behavior to hide substeps, and reveal them when they get focus. That's because I wanted to mimic the default impress.js behavior for steps. By default, all steps are visible; they may be out of the viewport, but they are visible. If you want steps to act otherwise, you need to style them. Same applies for substeps. You could pretty easily fork this and hack in default hiding if you really want it.

I haven't added "impress:substep" events dispatching yet. I actually have a day job. They're coming soon, and then maybe I'll pull request @bartaz :)

Same as impress.js, this code is released under the MIT and GPL Licenses.