Avoid iFrame content clipping with CSS transform on iOS

The HTML(5) version of our SCORM based e-learning runtime heavily uses i-frames as template containers. This architecture gives a lot of flexibility but since customers mainly request iPad support we where very unhappy with Safari’s rendering capabilities on iOS. Of course we use CSS transform to get the best animation performance on mobile devices, but in Apple’s mobile browser you’ll likely see huge clipping rectangles during hardware accelerated transitions.

There was not much information about that issue online but at least this entry on stackoverflow suggested there is not much you can do. Well, it took a lot of trail an error testing time but finally we nailed it. The solution is quite simple:

Whenever you use CSS transform with i-frames or it’s parents you also need to apply a basic CSS transform to the body tag of your i-frame content. That’s it. You can also use other contents within the loaded frame HTML page but the body tag seems to be the perfect target.

So this is a little JavaScript code snipped:

// Reference to your iFrame HTML element
var iFrameElement = document.getElementById( "yourIFrameID" );
 
// Avoid clipping by applying simple css transfrom3D to the iframe content itself
$( iFrameElement.contentWindow.document.body ).css( "-webkit-transform", "translate3d(0,0,0)" );
 
// Start your iFrame transition (from a visible position)
$( iFrameElement ).css( "-webkit-transform", "translate3d(-1000px,0,0)" );

UPDATE: Make sure you start from a visible position!

Don’t forget to remove CSS transform after your animation is done:

// Don't forget to reset after your transition has finished!
$( iFrameElement.contentWindow.document.body ).css( "-webkit-transform", "none" );

I suggest to use “none” as the default value. We sometimes experienced weird behavior using an empty string…

Have fun coding!

4 thoughts on “Avoid iFrame content clipping with CSS transform on iOS”

  1. Hi,

    I’m looking for a fix for that issue. What do you mean exactlly by ” from a visible position ” ?

    Thanks

  2. Hi! It worked best when the <iframe> was in a visible area but had full alpha transparency!

    Hopefully this is not outdated since wie already have new mobile Safari versions… Does it still work?

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