Internet Explorer 9 introduced support for CSS 2D Transforms. Internet Explorer 10 Developer Preview added support for
CSS 3D Transforms and
CSS Animations. By tapping the power of your GPU and running asynchronously from regular JavaScript, these IE10 features provide a more performant and flexible alternative to traditional script-based animations for Web content.
In previous blog posts, we covered
CSS 3D Transforms as well as
CSS Animations and Transitions. In this post, we introduce a more “unconventional” use case for these technologies by describing the concept of “full-page animations” that can be used during the navigation process to add fluidity and continuity to browsing. Our target is to achieve a seamless browsing experience in which content smoothly appears into view when the user visits a page and transitions away when he clicks on a link or performs a relevant action.
These effects can be accomplished by transforming the HTML
The code samples in this post use unprefixed CSS markup as supported by IE10 Release Preview; other browsers may require vendor prefixes for the CSS Animations and CSS Transforms properties used.
Transforming a Page’s Entire Content
CSS Transforms are defined on the stylistic properties of an HTML DOM Element. For example, the markup for rotating an element 45 degrees along its Z axis would look like this:
#element {
transform: rotateZ(45deg);
}
Attaching a transform to the
body {
transform: rotateZ(45deg);
}
Let’s look at a before-and-after shot of a page when applying a transform to the body element:
Applying a rotateZ(45deg) transform to the body element of a document.
For three dimensional transformations, the CSS Transforms specification defines the perspective property that can be specified on the parent of the element that we transforming. When transforming the
html {
perspective: 500px;
}
Combining this with a rotateY(45deg) transform on the
Applying a rotate(45deg) transform to with perspective: 500px set on .
We can manipulate the transform-origin property on the body element for interesting results. Let’s look at a couple of examples:
body {
transform-origin: 50% 100%;
transform: rotateX(45deg);
}
The above markup sets a rotation along X for the body element while shifting the origin of rotations to the bottom of the element using transform-origin. Effectively this rotates the document’s contents “into” the screen like this:
We can also manipulate the perspective-origin property on the root element of our document to achieve an off-axis projection effect. Changing the style for
html {
perspective: 500px;
perspective-origin: 90% 50%;
}
Our page now looks like this:
By using CSS Transforms, we can easily manipulate the visual appearance of the entirety of our page’s content. Since the usual layout and sizing rules still apply, some transforms on the body element (particularly ones that use percentage values or rely on the transform-origin property) can result in different visual effects depending on the content of our page. Recall our previous rotateX(45deg) example with transform-originset to 50% 100%.
Below you can see the results before and after the transform is applied.
Notice how the content does not actually pivot on the bottom of the window but rather at some point outside of the viewport. This is expected behavior for CSS Transforms: the
So how do we deal with arbitrarily sized content when applying transforms to our body element? Custom tailoring all content in order to ensure that the size of the body does not expand more than a certain amount may be unrealistic. Instead, we can use a simple HTML/CSS pattern that allows us to fix the size of the body element to that of the browser window and append content inside a wrapper
. The following markup achieves just that:
html, body {
width: 100%;
height: 100%;
min-width: 100%;
max-width: 100%;
padding: 0;
margin: 0;
overflow: hidden;
}
#Wrapper {
position: absolute;
width: 100%;
height: 100%;
overflow: scroll;
}
The illustration below shows what happens when a page is scrolled vertically and we apply a rotateY(45deg)transform to the
The direct application of the transform results in a skewed visual result due to the off-axis projection (since we are no longer looking at the “center” of the body element). Using the wrapper pattern ensures that the perspective-origin property (50% 50% by default) will always be correctly centered with relation to the
By utilizing the above pattern and setting up CSS Transforms with percentage values whenever possible, we can affect our
From Transforms to Animations
Having sorted out the intricacies of applying CSS Transforms to the
Consider this basic @keyframes rule:
@keyframes rotateInLeft {
from {
transform-origin: 0% 0%;
transform: rotateY(180deg);
}
to {
transform-origin: 0% 0%;
transform: rotateY(0deg);
}
}
When applied to an element, this animation will cause it to rotate on its left side. When applied to a
Similarly, we can compose animations that fluidly remove our Web content from view. For example, if we wanted our page to disappear into the distance while rotating, we could use something like this:
@keyframes whirlOut {
to {
transform: scale(0) rotateZ(1260deg);
}
}
With the visual result being:
Since we can use the full power of CSS Animations to affect the entirety of our Web content, we have a lot of flexibility in terms of generating these page effects (and we are certainly not limited to just using CSS Transforms). But once we have composed the effects that we want to apply to our content, how do we cause them to trigger during the page navigation process?
Attaching Animations to
Our goal is to use trigger animations at strategic times during the browser experience in order to give the appearance of content transitioning into view when a page loads and out of view when the user clicks on a link.
The first intuitive place to add an animation to the body element would be the onload JavaScript event. As it turns out however, adding an animation when onload fires is actually too late. This event actually triggers when the entirety of the content in our page has finished loading (including any images or other bandwidth-intensive resources). Attaching an animation to onload on a bandwidth-intensive page would result in our content displaying “normally,” followed by the animation triggering and re-bringing the content into view. Not exactly the effect that we were aiming for.
Alternatively, we could utilize the
DOMContentLoaded event that triggers when the browser has finished parsing the DOM structure of our content (but potentially before resources have finished loading). The IE Test Drive
DOMContentLoaded demo illustrates the difference between these two events. However, in cases of complex Web content, a modern browser may choose to perform “progressive” rendering, displaying the page before the entirety of the DOM tree has been loaded. In these situations, the visual result would be similar to the
onload scenario.
The optimal place to set up an animation that transitions our page content in view is inline at the top of thefrom keyframe of our selected animation). A pleasant side effect of this approach is that the animation may actually mask any progressive rendering, re-layout or resource loading that can occur with complex content.
Setting up the animations that transition our content out of view is also interesting. One could assume that we could attach an
onclick handler to all elements of interest in our content (for instance all
tags) and just set the relevant animation properties (
animation-name,
animation-duration, etc.) in the callback function. However, if we do not actually
delay the navigation from happening, we will not see our expected fluid transition.
This is a good opportunity to utilize the
animation events described in the CSS Animations specification. In particular, we can use the
animationend event to detect when the animation has completed and then
trigger a navigation (by setting
window.location.href, for instance). Thus our
onclick will trigger the “remove-from-view” animation and register a handler for
animationend on
that will ensure that the navigation event occurs.
Live Demo Available
To simply enjoy the page-to-page animations, step through the pages of the tutorial using the “Continue to ...” links in the lower right corner of each page.
At the end of the tutorial we provide some additional guidance and sample code on how to incorporate these animations with your own Web content.
Conclusion
CSS Transforms and CSS Animations are two powerful feature-sets that enable richer and more immersive Web experiences. This blog post outlined the considerations of using CSS Transforms and CSS Animations to bring the entirety of your Web content to life. With a small amount of effort you can create Web pages (even static ones) that provide a fluid and almost app-like navigation experience.
—Charilaos “Harris” Papadopoulos, Program Manager Intern, Internet Explorer Graphics
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