javascriptcss-animationssvg-animatesmilvisibilitychange

Prevent SMIL animation from pausing when switching between browser tabs


How to prevent SMIL animation from pausing when switching between browser tabs?

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.


Solution

  • 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:

    1. gets new date
    2. resets animation clock with setCurrentTime(0)
    3. updates <path> transform attribute
    4. starts animation with unpauseAnimations()

    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()
         }
       })