Main loop

Initialization

The game initialization happens right after the game launch. It consists of the following steps:

All global on_initialize() functions are called.
- It is possible for every module to have its own single on_initialize(), but the call order will be undefined.
A default prefab is instantiated.
- For every node, Component.on_initialize() is called (like in any prefab instantiation).
  The calls order is the same as the order of Component.on_update() calls (see below).
- This step is skipped if no default prefab is provided.

Game loop

The main loop consists of the following calls to user-provided functions:

on_resolution_changed if resolution changed
All global on_update() functions.
- Multiple modules can have their own on_update() functions (but a single module can have only one on_update()).
  If multiple modules have on_update(), they are called in random order.
All Component.on_update() functions
- For every alive node, call Component.on_update()
  Order of nodes: in the order of creation
  
  For example, if node a is created before b, then a will always be called before b, regardless of the scene tree.
  
  Order of components: in the order of addition
  
  For example, if component Foo is added to a node before component Bar, then Foo.on_update() will be called before Bar.on_update().
Physics simulation
- Simulate physics and invoke collision callbacks for collisions that occurred during this frame. See Physics Simulation in a Main Loop.

Functions

on_initialize ()

on_update ()

on_resolution_changed (res: int2)

on_before_reload ()

on_after_reload ()

on_pause (pause: bool)

on_exit ()

on_editor_update (playing: bool)

on_initialize()

This function is called once when the scene is first loaded

Usage example:

[export]
def on_initialize() {
    print("Hello, world!")
}

on_update()

This function is called every frame

Usage example:

[export]
def on_update() {
    print("Frame time {get_delta_time()}")
}

on_resolution_changed(res: int2)

This function is called when the resolution is changed

Arguments:

res : int2 - The new resolution

Usage example:

[export]
def on_resolution_changed(res : int2) {
    print("Resolution changed to {res}")
}

on_before_reload()

This function is called before the scene is reloaded Usually whole global state of game can be automatically hot-reloaded, but sometimes you need to do some manual setups in this function

Usage example:

[export]
def on_before_reload() {
    print("Reloading scene...")
}

on_after_reload()

This function is called after the scene is reloaded

Usage example:

[export]
def on_after_reload() {
    print("Scene reloaded")
}

on_pause(pause: bool)

This function is called when the scene is paused. Can be used to save the game state

Arguments:

pause : bool - True if the scene is paused, False if it is resumed

Usage example:

[export]
def on_pause(pause : bool) {
    if (pause) {
        print("Game paused")
    } else {
        print("Game resumed")
    }
}

on_exit()

This function is called when the scene is exited. Last chance to save the game state

Usage example:

[export]
def on_exit() {
    print("Exiting game")
}

on_editor_update(playing: bool)

This function is called every frame in the editor. Can be used to draw debug information in the editor.

Arguments:

playing : bool - True if the game is running in the editor, False if it is paused

Usage example:

[export]
def on_editor_update() {
    print("Inside editor")
}