art with code

2014-08-31

Spinners on the membrane

I wonder if you could do image loading spinners purely in CSS. The spinner part you can do by using an animated SVG spinner as the background-image and inlining that as a data URL. Detecting image load state, now that's the problem. I don't think they have any attribute that flicks to true when the image is loaded. There's img.complete on the DOM side, but I don't think that's exposed to CSS. And it's probably tough to style a parent element based on child states. And <img> elements are fiddly beasts to begin with.

If you had a :loading (or some sort of extended :unresolved) pseudo-class that bubbled up the tree, that might do it. You could do something like .spinner-overlay { background: white, url(spinner.svg)50% 50%; width: 100%; height: 100%; opacity: 0; } *:loading > .spinner-overlay { opacity: 1; transition: 0.5s; }. Now when your image is loading, it'd have a spinner on top of it and it'd go away when it stopped loading. And since :loading doesn't care about what is loading, it'd also work for background-images, video, audio, iframes, web components, whatever.

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