Can't restore RNG state properly

[timothyqiu]

Godot version: 3.2.3 & current master (ba51af7)

OS/device including version: not graphics-related.

Issue description:

RNG state is not restored after calling RandomNumberGenerator.set_seed with a seed saved from RandomNumberGenerator.get_seed.

The issue is caused by get_seed returning the current RNG state, while set_seed takes a seed, not state.

PR #35764 tries to resolve this problem by making the interface more intuitive, but seems inactive.

PR #27171 introduced this behavior.

A workaround is, maybe, reseeding manually after generating a number, sacrificing randomness.

Steps to reproduce:

Run the following script with Godot.

extends SceneTree


func _init():
	var rng = RandomNumberGenerator.new()

	# let the seed change
	rng.randomize()
	rng.randi()
	rng.randi()

	var saved = rng.seed
	print('Current seed: ', saved)

	print('This seed produces:')
	print(rng.randf())
	print(rng.randf())

	rng.seed = saved
	print('Resetting the seed produces:')
	print(rng.randf())
	print(rng.randf())

Actual output:

Current seed: 8670679328791200068
This seed produces:
0.823806
0.514134
Resetting the seed produces:
0.028601
0.02974

Expected output:

Current seed: 8670679328791200068
This seed produces:
0.823806
0.514134
Resetting the seed produces:
0.823806
0.514134

Minimal reproduction project: N/A

[ghost]

PR #27171 introduced this behavior.

I thought that was reverted. b5d9099

[timothyqiu]

It's only reverted on the 3.1 branch. 😂

[ghost]

Oh right, it was left in the master, and 3.2 was the master back then. Yeah, reverting it solves the issue.