Fix AudioStreamPlayer.play() ignores get_tree().paused

[neclor]

Problem

AudioStreamPlayerInternal::play_basic() does not respect Node pause mode.
As a result, a AudioStreamPlayer can start playback while the SceneTree is paused.

This change prevents play from starting when node->can_process() is false.

Issue

Fixes #114694

[wlsnmrk]

Thanks for putting this fix together!

A suggestion: it might be preferable, instead of returning early, to let the playback construction proceed and then call set_stream_paused(!node->can_process()) at the end of play_basic(), before the return.

Advantages:

• It leaves the playback queued for when the tree resumes, instead of discarding the call to play_basic()
• It's analogous to the behavior in notification() at line 97
• I believe it would fix the TODO in set_stream_paused() at line 178 (181 in your modified version), which seems likely to be the root of AudioStreamPlayer.play() ignores get_tree().paused #114694

[neclor]

You're right, your suggestion makes more sense.

I noticed that VideoStreamPlayer handles this by manually triggering the pause notification:

void VideoStreamPlayer::play() {
	//...
	if (!can_process()) {
		_notification(NOTIFICATION_PAUSED);
	}
}

I think we should follow the same pattern in AudioStreamPlayerInternal
Something like:

if (!node->can_process()) {
	notification(Node::NOTIFICATION_PAUSED);
}

[neclor]

I don't think this will resolve the TODO in set_stream_paused(). To fix it, we would need a new variable to save the pause state even when there is no stream.