Allow events to run even when focus is lost

[stevenmathews]

eg. sources.Time.periodic(1000) pauses when I switch tabs and resumes when I come back due to requestAnimationFrame.

[staltz]

Hmm, I understand this, but may I ask what is the root problem? What feature are you trying to achieve by wanting the periodic to keep emitting when the tab has changed?

[stevenmathews]

Generating invoices from a pomodoro timer. Need the timer to continue while I work.

Nick asked me to open this issue but also recommended I use Time.animationFrames() which offers the functionality I need.

[Frikki]

Doesn’t the events pick up and synchronize when you return to the tab?

[stevenmathews]

@Frikki It pauses the time then resumes where it left off on refocus.

[staltz]

What if you don't use periodic() to track time, but just use periodic() to sample time? For instance with Date.now(). If you want a stopwatch, you can subtract from an initial timestamp.

[stevenmathews]

What is the advantage of this approach over usingTime.animationFrames()? (wanting to learn not saying it's better).

[Widdershin]

They're comparable, but either way all it's not going to run in the background, since both of them are powered by requestAnimationFrame under the hood, and animations don't need to run in the background.

One option to consider, is that I just checked in Chrome and it seems like setImmediate still runs in the background, albeit slower, and I wouldn't be surprised if the polyfill hack using postMessage works as well.

I might consider powering periodic() and others from a setImmediate schedule to enable this. That additional flexibility in the design would also aid with implementing #29.

animationFrames and throttleAnimation would still be requestAnimationFrame powered and could be used to throttle the UI as needed, so that would be okay. We could just document how requestAnimationFrame works here.

[Widdershin]

Oh, and a use case as to why this is important: say you want to play a sound on a timer, it would not be great if it just didn't work at all because it was in a background tab. Much better to have it play 500ms later than not at all.

[Widdershin]

I started having a look and as I hoped the setImmediate polyfill runs in the background in Chrome and Firefox, so I can go ahead with this.