Implement "looped" signal for AudioStreamPlayer, 2D and 3D

[vaartis]

Track the number of loops on the player and if it changes, emit a singal.

Closes godotengine/godot-proposals#1641

[vaartis]

Also added the same signal to the animation player, as suggested in the linked issue.

[TokageItLab]

These codes looks messed up in totality.

It makes no sense to count the number of loops on the signal side. Also, it may cause an implicit overflow. Signal should only notify the fact that a loop has occurred and should be counted on the user script side.

Moreover, the looped signal should fire only when a loop occurs, so should not fire at the same time as finished.

[TokageItLab]

Ah, I misunderstood a bit. The looped count is something that already exists, and the user determines the upper limit, right? But I think there may be a cleaner way to fire signal.

Also I remember there was some problem with the AnimationPlayer looped flag and I didn't implement it. I'll take a look at it later...

[vaartis]

It makes no sense to count the number of loops on the signal side. Also, it may cause an implicit overflow. Signal should only notify the fact that a loop has occurred and should be counted on the user script side.

The overflow here does not matter, even if it overflows the number still changes and this is what matters to fire the signal. I just used the type that get_loop_count() returns.

Moreover, the looped signal should fire only when a loop occurs, so should not fire at the same time as finished.

It only fires if the stream did not end, hence the else if on the condition that checks if it ended.

Don't know about the AnimationPlayer problem, I only tested the simplest case of making a looping animation and subscribing to the signal.

[reduz]

I oppose the merging of this PR on the following grounds:

• Emitting a signal from the audio thread is wrong in many accounts 1) Audio thread must never run complex logic that can allocate memory or run game logic as a result of a signal, because its time (callback) constrained. 2) A signal emitted from the audio thread is useless and dangerous.
• You can already query the loop count, so all you have to do is check every frame whether the audio has looped.

[TokageItLab]

This PR originally tried to fire a signal by storing the loop counts of all streams in a map, is this the correct way to do it? Considering the many possibilities of not using the signal, it seemed to me to be expensive.

Perhaps the correct way to do it is to set up a script that monitors only certain Streams when a signal is needed on the user's side.

[vaartis]

Perhaps the correct way to do it is to set up a script that monitors only certain Streams when a signal is needed on the user's side.

Is there a way to check if a signal is needed at all? And if so, how should it track the looping? If emitting a signal on the audio thread is not a good idea, maybe just using the old approach with the dictionary is fine, as long as I can somehow know if I need to track only certain streams.