I have SVG clock that is animated using <animatetransform>
. When you switch to another tab animation freezes and don't catch up to where it should be.
I want this animation to either run smoothly when page is not visible or to pause and catch up when the page is visible again. I can convert this to CSS animation, it doesn't matter.
Here's a simplified code for seconds hand:
HTML:
<svg viewbox="-250 -250 500 500" fill="none" stroke="#000">
<!-- ... -->
<path id="Sec" stroke="#000" stroke-width="14" d="M0 0v-220">
<animatetransform fill="freeze" additive="sum" attributename="transform" dur="60s" from="0" repeatcount="indefinite" to="360" type="rotate" />
</path>
<!-- ... -->
</svg>
JS:
const date = new Date()
const sec = date.getSeconds()
document.getElementById('Sec').setAttribute('transform', `rotate(${(sec * 360 / 60) % 360})`)
I know how to use Page Visibility API
to pause things but how to prevent them from doing so is incomprehensible for me.
Ok. I figured that one out.
When the page is hidden the animation is paused with animationsPaused()
.
When the page is visible again the script:
setCurrentTime(0)
<path>
transform
attributeunpauseAnimations()
HTML:
<svg id="Watch" viewbox="-250 -250 500 500" fill="none" stroke="#000">
<!-- ... -->
<path id="Sec" stroke="#000" stroke-width="14" d="M0 0v-220">
<animatetransform fill="freeze" additive="sum" attributename="transform" dur="60s" from="0" repeatcount="indefinite" to="360" type="rotate" />
</path>
<!-- ... -->
</svg>
JS:
const svg = document.getElementById('Watch')
let date = new Date()
const watch = () => {
document.getElementById('Sec').setAttribute('transform', `rotate(${(date.getSeconds() * 360 / 60) % 360})`)
}
window.requestIdleCallback(() => watch())
document.addEventListener('visibilitychange', () => {
if (document.hidden) svg.pauseAnimations()
else {
date = new Date()
svg.setCurrentTime(0)
watch()
svg.unpauseAnimations()
}
})