Jittery text during scaling animations with JavaScript

Question

When using scaling to change the size of an HTML element containing text, the text jitters during the animation, but only if being animated with JavaScript libraries.

The jittering is most visible when the animation is slower and the text is smaller. I can't seem to figure out what causes it or how to get rid of it.

This jittering does not occur during CSS animations or animations using the fairly new JavaScript Web Animations API. It also doesn't seem to occur in some browsers. (On my iPhone)

To easily compare the different methods of animating the scaling of an element and how they appear, I made a CodePen for convenience. Before checking it out, note these points:

1. All the animations are using some form or imitation of the CSS property transform: scale(num); for the animation and have the same easing and duration so they can be compared more easily.
2. Although the jittering appears on macOS too, it is almost impossible to see on Macs with retina screens because of the high resolution.
3. The results I got are a reflection of the appearance of the animations on a Windows 10 machine in Google Chrome 59, although for me Microsoft Edge also showed the same results.

So my question is this: How can I prevent the text from jittering or becoming blurry when animating a scale property with JavaScript? How can I make the text in my JavaScript scale animations appear just as smooth as they do when using CSS?

You may be wondering why I don't just use CSS. The answer is because I'm frustrated with how limited CSS animation is. I would like to use advanced easing functions beyond the capabilities of a simple bezier curve (like Robert Penner's bounce and elastic functions), and use different easings on hover when the mouse enters and exits the element. This s completely my own opinion, but so far the only painless way I've found to do this is with JavaScript libraries. Besides their functionality relating to easing, most seem to offer many other capabilities which make animating much more effortless. If you know of a better way to get all the functionality I need please let me know!

Answer 1

What you are encountering are differences in a browser's layerizing strategy. You'll find that all the examples appear smooth in Firefox. That's because Firefox detects when script is changing a property that can animated using layers and creates a layer in response.

Although all browsers create layers when needed for declarative animations (CSS animations, CSS transitions, Web Animations API animations, and even SVG SMIL animations in some cases) not all browsers do it for Javascript animations. So, for those browsers you need to try to trick the browser into creating a layer (or, you could just file a bug on the browser, since it really should do this for you!).

Until recently, using will-change: transform was the recommended approach to get a browser to create a layer. However, Chrome changed its rendering strategy and now will-change: transform can produce very blurry results with scale animations in Chrome. Some people have succeeded in tricking Chrome to layerize at a higher resolution initially and then scaling their element down before animating. This is really unfortunate to have to do this and I can only encourage you to petition Chrome to fix this.

Also, the examples using "with HA" are not accurate. The CSS animation in (1) will also use hardware acceleration in every browser I know of--there's no need to add perspective in. Unfortunately, there is a lot of misleading information in this area (e.g. some articles claim animations can run on the GPU but that's simply not true). At the risk of self promotion, you might find an article I wrote on this last year helpful.