AnimationTree: Frame has mixed information when using both continuous and discrete animation tracks while auto transitioning in AnimationNodeStateMachine

[Akatuoro]

Godot version

v4.0.stable.official.92bee43ad and v4.0.1.stable.official.cacf49999

System information

Windows 10

Issue description

In an AnimationNodeStateMachine, when transitioning between animation states (with 'At End', 'Auto'), there is a single frame glitch showing a mix of the old and the new animation (old region_rect and new frame for a Sprite2D). The region_rect track has 'Update Mode' 'Continuous' while the frame track has 'Update Mode' 'Discrete'.

When changing the animation directly on the AnimationPlayer (via timer), it correctly shows the new animation.

reproduce-animation-bug.DEBUG.2023-03-27.00-25-11.mp4

When logging the changing region_rect and frame values in _process, the frame is also visible:

# using AnimationNodeStateMachine
region x: 64, frame: 0, anim:   blue12, pos: 0.008333
region x: 64, frame: 1, anim:   blue12, pos: 0.400000
region x: 64, frame: 0, anim:  black12, pos: 0.000000   # this is unexpected
region x:  0, frame: 0, anim:  black12, pos: 0.008333
region x:  0, frame: 1, anim:  black12, pos: 0.400000
region x:  0, frame: 0, anim:   blue12, pos: 0.000000   # here as well
region x: 64, frame: 0, anim:   blue12, pos: 0.008333
region x: 64, frame: 1, anim:   blue12, pos: 0.400000
region x: 64, frame: 0, anim:  black12, pos: 0.000000   # etc.
region x:  0, frame: 0, anim:  black12, pos: 0.008333

# using AnimationPlayer.play()
region x:  0, frame: 1, anim:  black12, pos: 0.400000
region x: 64, frame: 0, anim:   blue12, pos: 0.008333
region x: 64, frame: 1, anim:   blue12, pos: 0.400000
region x:  0, frame: 0, anim:  black12, pos: 0.008333
region x:  0, frame: 1, anim:  black12, pos: 0.400000
region x: 64, frame: 0, anim:   blue12, pos: 0.008333
region x: 64, frame: 1, anim:   blue12, pos: 0.400000
region x:  0, frame: 0, anim:  black12, pos: 0.008333

Switching the 'Update Mode' to 'Discrete' for the region_rect animation track fixes the glitched frame. But that inhibits other functionality, so my expectation would be that the animation state transition also behaves coherently with 'Update Mode' set to 'Continuous'.

Steps to reproduce

Create 2 animations in an AnimationPlayer, each with a track for region_rect and frame on a Sprite2D:

Then create an AnimationTree with an AnimationNodeStateMachine that automatically transitions between these animations with switch mode 'At End':

Minimal reproduction project

reproduce-animation-bug.zip

[TokageItLab]

Closed by #86629 (or previous)