Table of Contents

Class MainLoop

Abstract base class for the game's main loop.

Inheritance
MainLoop
Derived

Remarks

MainLoop is the abstract base class for a Godot project's game loop. It is inherited by SceneTree, which is the default game loop implementation used in Godot projects, though it is also possible to write and use one's own MainLoop subclass instead of the scene tree.

Upon the application start, a MainLoop implementation must be provided to the OS; otherwise, the application will exit. This happens automatically (and a SceneTree is created) unless a MainLoop Script is provided from the command line (with e.g. godot -s my_loop.gd) or the application/run/main_loop_type project setting is overwritten.

Here is an example script implementing a simple MainLoop:

class_name CustomMainLoop
extends MainLoop

var time_elapsed = 0

func _initialize():
    print("Initialized:")
    print("  Starting time: %s" % str(time_elapsed))

func _process(delta):
    time_elapsed += delta
    # Return true to end the main loop.
    return Input.get_mouse_button_mask() != 0 || Input.is_key_pressed(KEY_ESCAPE)

func _finalize():
    print("Finalized:")
    print("  End time: %s" % str(time_elapsed))

Fields

NOTIFICATION_OS_MEMORY_WARNING

Notification received from the OS when the application is exceeding its allocated memory.

Specific to the iOS platform.

const NOTIFICATION_OS_MEMORY_WARNING = 2009

NOTIFICATION_TRANSLATION_CHANGED

Notification received when translations may have changed. Can be triggered by the user changing the locale. Can be used to respond to language changes, for example to change the UI strings on the fly. Useful when working with the built-in translation support, like Object.tr.

const NOTIFICATION_TRANSLATION_CHANGED = 2010

NOTIFICATION_WM_ABOUT

Notification received from the OS when a request for "About" information is sent.

Specific to the macOS platform.

const NOTIFICATION_WM_ABOUT = 2011

NOTIFICATION_CRASH

Notification received from Godot's crash handler when the engine is about to crash.

Implemented on desktop platforms if the crash handler is enabled.

const NOTIFICATION_CRASH = 2012

NOTIFICATION_OS_IME_UPDATE

Notification received from the OS when an update of the Input Method Engine occurs (e.g. change of IME cursor position or composition string).

Specific to the macOS platform.

const NOTIFICATION_OS_IME_UPDATE = 2013

NOTIFICATION_APPLICATION_RESUMED

Notification received from the OS when the application is resumed.

Specific to the Android and iOS platforms.

const NOTIFICATION_APPLICATION_RESUMED = 2014

NOTIFICATION_APPLICATION_PAUSED

Notification received from the OS when the application is paused.

Specific to the Android and iOS platforms.

Note: On iOS, you only have approximately 5 seconds to finish a task started by this signal. If you go over this allotment, iOS will kill the app instead of pausing it.

const NOTIFICATION_APPLICATION_PAUSED = 2015

NOTIFICATION_APPLICATION_FOCUS_IN

Notification received from the OS when the application is focused, i.e. when changing the focus from the OS desktop or a thirdparty application to any open window of the Godot instance.

Implemented on desktop and mobile platforms.

const NOTIFICATION_APPLICATION_FOCUS_IN = 2016

NOTIFICATION_APPLICATION_FOCUS_OUT

Notification received from the OS when the application is defocused, i.e. when changing the focus from any open window of the Godot instance to the OS desktop or a thirdparty application.

Implemented on desktop and mobile platforms.

const NOTIFICATION_APPLICATION_FOCUS_OUT = 2017

NOTIFICATION_TEXT_SERVER_CHANGED

Notification received when text server is changed.

const NOTIFICATION_TEXT_SERVER_CHANGED = 2018

Methods

_finalize

Qualifiers: virtual

Called before the program exits.

void _finalize

_initialize

Qualifiers: virtual

Called once during initialization.

void _initialize

_physics_process(float)

Qualifiers: virtual

Called each physics frame with the time since the last physics frame as argument (delta, in seconds). Equivalent to Node._physics_process.

If implemented, the method must return a boolean value. true ends the main loop, while false lets it proceed to the next frame.

Note: delta will be larger than expected if running at a framerate lower than physics_ticks_per_second / max_physics_steps_per_frame FPS. This is done to avoid "spiral of death" scenarios where performance would plummet due to an ever-increasing number of physics steps per frame. This behavior affects both MainLoop._process and MainLoop._physics_process. As a result, avoid using delta for time measurements in real-world seconds. Use the Time singleton's methods for this purpose instead, such as get_ticks_usec.

bool _physics_process(float delta)

Parameters

delta float

_process(float)

Qualifiers: virtual

Called each process (idle) frame with the time since the last process frame as argument (in seconds). Equivalent to Node._process.

If implemented, the method must return a boolean value. true ends the main loop, while false lets it proceed to the next frame.

Note: delta will be larger than expected if running at a framerate lower than physics_ticks_per_second / max_physics_steps_per_frame FPS. This is done to avoid "spiral of death" scenarios where performance would plummet due to an ever-increasing number of physics steps per frame. This behavior affects both MainLoop._process and MainLoop._physics_process. As a result, avoid using delta for time measurements in real-world seconds. Use the Time singleton's methods for this purpose instead, such as get_ticks_usec.

bool _process(float delta)

Parameters

delta float

Events

on_request_permissions_result(String, bool)

Emitted when a user responds to a permission request.

signal on_request_permissions_result(String permission, bool granted)

Parameters

permission String
granted bool