Consider pausing all sound generators that support it when sim goes inactive

[jbphet]

Issue phetsims/john-travoltage#309 describes a problem where sound could keep playing when the sim is paused in the LoL framework. To resolve that issue, I added code that essentially disabled sound generation when the sim is not active. A more complete, but also more complex, solution would be to pause all sound generators that support it when the sim becomes inactive, and then resume then if and when the sim becomes active again. The pause functionality is not yet implemented for sound clips (see #40), but once it is, we should consider using it for a more complete pause behavior.

[pixelzoom]

I see "when the sim is paused in the LoL framework" and "when the sim is not active" in the above paragraph. Are "paused" and "not active" synonymous?

And out of curiosity, how does the LoL framework pause a sim?

[samreid]

LOL support is implemented in LegendsOfLearningSupport:

    // Respond to pause/resume commands from the Legends of Learning platform
    window.addEventListener( 'message', function( message ) {
      if ( message.data.messageName === 'pause' ) {
        sim.stepOneFrame();
        sim.activeProperty.value = false;
      }
      else if ( message.data.messageName === 'resume' ) {
        sim.activeProperty.value = true;
      }
    } );
  }