EffectSpawner:: has_more_to_spawn to report if particles will be spawned

[jpedrick]

Describe the solution you'd like
A function describing whether an effect spawner has more particles to spawn without reset() being called.

    /// Get whether the spawner is active.
    ///
    /// Inactive spawners do not spawn any particle.
    pub fn has_more_to_spawn(&self) -> bool {
        if self.active {
            if self.limit.is_finite() {
                self.active
            } else {
                self.spawn_remainder > 1.
            }
        } else {
            self.active
        }
    }

Describe why you want that solution. Is this related to a problem?
I would like to remove expired particle spawners after some time:

#[derive(Component)]
struct ScheduleDespawn{
    timer: Timer
}

fn despawn_explosion_effect( 
    mut commands: Commands,
    effect: Query<(Entity, &EffectSpawner), (With<ExplosionEffect>, Without<ScheduleDespawn>)>,
){
    for (e, spawner) in effect.iter() {
        if !spawner.has_more_to_spawn() {
            commands.entity(e).insert(ScheduleDespawn{
                timer: Timer::new(Duration::from_millis(5000), TimerMode::Once),
            });
        }
    }
}

fn despawn_scheduled(
    mut commands: Commands,
    mut scheduled: Query<(Entity, &mut ScheduleDespawn)>,
    time: Res<Time>,
){
    for (e, mut scheduled_despawn) in scheduled.iter_mut() {
        scheduled_despawn.timer.tick(time.delta());
        if scheduled_despawn.timer.finished() {
            commands.entity(e).despawn();
        }
    }
}

Describe alternatives you've considered
Just despawn entities after a known time limit. This change would just allow users to track or infer fewer parameters themselves.

[djeedai]

I looked again at this, I'm ok in principle I think, but the proposed implementation looks problematic. An "active" spawner is already defined conceptually as a spawner which ticks, irrelevant of whether or not more particle can be spawned. So a Spawner::rate() for example, which is infinite, would return has_more_to_spawn() == false if paused (set inactive) which feels wrong, if only because in your use case @jpedrick you'd despawn it even though it's not "finished". Thoughts?