general purpose state machine

A lean general purpose state machine plugin for Godot.

• AssetLib: Godot GPSM (#23837)
  • 1st proposal at Godot GPSM (#23828)
  • 2nd proposal at Godot GPSM (#23837)
• Github: github.com/kraasch/godot-gpsm
  • asset download url on github.com/kraasch/godot-gpsm

demo

code example

A little demo can be found in the ./addons/gpsm/examples/ sub-folder.

After downloading the plugin with the AssetLib tab or manually and after enabling the plugin under Project>Project Settings>Plugins the node GPSM will be available when adding a new node with the new node dialog (e.g. after having the Scene tab open and pressing ctrl+a).

For creating and connecting a new state machine do as shown below.

# setup a state machine like this.

var _SM: GPSM
var _A: GPSM.State
var _B: GPSM.State
var _C: GPSM.State
var _D: GPSM.State
var _T0: GPSM.Transition
var _T1: GPSM.Transition
var _T2: GPSM.Transition
var _T3: GPSM.Transition
var _T4: GPSM.Transition
var _T5: GPSM.Transition

func _setup_testing_state_machine() -> void:
    _SM = GPSM.new()
    #     ---->   T0
    #  A  <---- B T1
    #  |        |
    #  | T4     | T5
    #  V        V
    #  C  ----> D T2
    #     <----   T3
    _A = _SM.new_state()
    _B = _SM.new_state()
    _C = _SM.new_state()
    _D = _SM.new_state()
    _T0 = _SM.new_transition(_A, _B)
    _T1 = _SM.new_transition(_B, _A)
    _T2 = _SM.new_transition(_C, _D)
    _T3 = _SM.new_transition(_D, _C)
    _T4 = _SM.new_transition(_A, _C)
    _T5 = _SM.new_transition(_B, _D)

connect state transitions or log failure as shown below.

    var collect_failures: Callable = func(message: String, transition: GPSM.Transition, current_state: GPSM.State):
        label.text = message
    for i: int in len(states):
        var state: GPSM.State = states[i]
        var visual_state: DemoState = visual_states[i]
        state.on_entered.connect(visual_state.blink)
        state.on_exited.connect(visual_state.stop_blink)
        state.on_entered.connect(func (): print('entered state' + str(i)))
        state.on_exited.connect(func (): print('exited state' + str(i)))
    for i: int in len(transitions):
        var transition: GPSM.Transition = transitions[i]
        var arrow: DemoArrow = arrows[i]
        arrow.inner_transition = transition
        transition.on_failure.connect(arrow.blink)
        transition.on_failure.connect(func (msg, t, s): print('failed transition: ' + str(msg)))
        transition.on_failure.connect(collect_failures)
    _SM.initialize()

the intial state transition when calling the statem machine's initialize() function can be toggled on or off.

the machine can throw warnings, when transitions are triggered during the wrong state.

individual transitions can also be troggled.

# will create push_warning() or push_error()
    _SM.throw_type = GPSM.THROW_TYPE.SILENT
    _SM.throw_type = GPSM.THROW_TYPE.ERROR
    _T3.throw_type = GPSM.THROW_TYPE.WARNING

# or connect a custom function to transition failure.
    var collect_failures: Callable = func(message: String, transition: GPSM.Transition, current_state: GPSM.State):
        custom_messages.append(message)
        transitions.append(transition)
        states.append(current_state)
    _T3.on_failure.connect(collect_failures)

license

see license file.

credits

see web repository's contributions.