GPUParticles don't emit finished signal when oneshot is set true in gdscript

[JUSTCAMH]

Tested versions

• Reproducible in 4.3.beta2
• Reproducible in 4.2.1.stable

System information

Godot v4.3.beta2 - Windows 10.0.19045 - GLES3 (Compatibility) - NVIDIA GeForce RTX 3070 (NVIDIA; 31.0.15.3619) - 11th Gen Intel(R) Core(TM) i7-11700K @ 3.60GHz (16 Threads)

Issue description

When setting oneshot to true on a GPUParticles2D node, the particles visually stop emitting some time later as expected, however the 'finished' signal is not emitted. This does not occur with CPUParticles2D. I have not tested this for 3D particles, but I presume that this also applies to the GPUParticles3D.

Steps to reproduce

• Open the MRP below
• There are two particle emitters, the left is GPU and the right is CPU.
• Both are setup the same, and each have a custom script. In this script, the emitters are set to have oneshot enabled on ready. A function is connected to the finish signal which will print a message and free the particle emitters.
• Play the game. Both particle emitters visually stop emitting, however only the CPU particles prints a message and frees itself. Checking the remote hierarchy, you can see that the GPUParticles2D is still present despite nothing being emitted; the finished signal should have emitted!
• If the oneshot setting is enabled on the GPUParticles2D from the beginning (rather than being set through gdscript), then the finished signal correctly emits.

Minimal reproduction project (MRP)

particles-finished-bug.zip

[JekSun97]

I confirm this problem

[4X3L82]

I reported something similar in #93546.

[patwork]

Perhaps this is related #76859 (comment)

❗ UPDATE: try using restart() instead of emitting = true (godotengine/godot-proposals#7322)

[4X3L82]

Perhaps this is related #76859 (comment)

❗ UPDATE: try using restart() instead of emitting = true (godotengine/godot-proposals#7322)

But that comment is about how to start a particle emitter, while this issue (and #93546) is about finishing it?
Not to mention on my issue #93546 I do use restart() and I still don't get a finished() signal.

[patwork]

This is script from the MRP in this issue (sorry, I didn't look at yours):

extends GPUParticles2D

func _ready() -> void:
	one_shot = true
	emitting = true
	finished.connect(finish)


func finish() -> void:
	print("GPU Particles Destroyed!")
	queue_free()

After adding restart() in _ready() function signal will be emitted.

IMHO he problem lies in the fact that the one_shot value is changed when the emitter is already added to the scene tree and has an active emitting state.

godot/scene/2d/gpu_particles_2d.cpp

Lines 43 to 68 in b97110c

	void GPUParticles2D::set_emitting(bool p_emitting) {
	// Do not return even if `p_emitting == emitting` because `emitting` is just an approximation.
	if (p_emitting && one_shot) {
	if (!active && !emitting) {
	// Last cycle ended.
	active = true;
	time = 0;
	signal_canceled = false;
	emission_time = lifetime;
	active_time = lifetime * (2 - explosiveness_ratio);
	} else {
	signal_canceled = true;
	}
	set_process_internal(true);
	} else if (!p_emitting) {
	if (one_shot) {
	set_process_internal(true);
	} else {
	set_process_internal(false);
	}
	}
	emitting = p_emitting;
	RS::get_singleton()->particles_set_emitting(particles, p_emitting);
	}

If signal_canceled is set, signal will not be emitted.