README.md

Rollback State Machines

General-purpose State Machine system with rollback netcode sync support (optional).

Setup

You can download the .yymps file (right side - releases) or simply copy the script from the .gml file.

Features

• Create states and organize all the code in just one place;
• It has a "Free State" that is executed every frame, regardless of the current state;
• Transitions: change from one state to another using a condition;
• onStart, onStep and onExit functions/methods for each state (all optional).
• State history (useful for going back to previous states);
• Triggers (clone the execution behaviour of another state);
• State override (single function or to another state);
• Get current state name.
• Netcode rollback compatible (non-native)
• • With just one integer variable, synchronize State Machine state - which consumes less memory than structs, and better performance (no need for serialization).
• • Uses object variable to synchronize, which updates automatically.
• You can use strings or integers to reference the states.

Usage

An example of usage:

Create Event:

// Create State Machine
fsmChar = new StateMachine("Idle");
characterState = 0; // trackable state variable (for rollback netcode sync)

// Free
fsmChar.AddFreeState(function() {
	// get input
	inputH = keyboard_check(vk_right) - keyboard_check(vk_left);
	inputV = keyboard_check(vk_down) - keyboard_check(vk_up);
	inputJump = keyboard_check_pressed(vk_up);
});

// Idle
fsmChar.AddState("Idle", {
	onEnter : function() {
		sprite_index = sprPlayerIdle;
		image_speed = 0.25;
	},
});

// Walk
fsmChar.AddState("Walk", {
	onStep : function() {
		if (inputH != 0) image_xscale = sign(inputH);
	},
	onEnter : function() {
		sprite_index = sprPlayerWalk;
		image_speed = 0.8;
	},
	onExit : function() {
		show_debug_message("Walk Exit...");
	}
});

// Create Transitions
fsmChar.AddTransition("Idle", "Walk", function() {
	return (inputH != 0);
});
fsmChar.AddTransition("Walk", "Idle", function() {
	return (inputH == 0);
});

Step Event:

fsmChar.Update(id, "characterState");