MainLoop

Inherits: Object

Inherited By: SceneTree

Abstract base class for the game's main loop.

Description

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 main Script is provided from the command line (with e.g. godot -s my_loop.gd, which should then be a MainLoop implementation.

Here is an example script implementing a simple MainLoop:

extends MainLoop

var time_elapsed = 0
var keys_typed = []
var quit = false

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

func _idle(delta):
    time_elapsed += delta
    # Return true to end the main loop.
    return quit

func _input_event(event):
    # Record keys.
    if event is InputEventKey and event.pressed and !event.echo:
        keys_typed.append(OS.get_scancode_string(event.scancode))
        # Quit on Escape press.
        if event.scancode == KEY_ESCAPE:
            quit = true
    # Quit on any mouse click.
    if event is InputEventMouseButton:
        quit = true

func _finalize():
    print("Finalized:")
    print("  End time: %s" % str(time_elapsed))
    print("  Keys typed: %s" % var2str(keys_typed))

Methods

void	_drop_files ( PoolStringArray files, int from_screen ) virtual
void	_finalize ( ) virtual
void	_global_menu_action ( Variant id, Variant meta ) virtual
bool	_idle ( float delta ) virtual
void	_initialize ( ) virtual
void	_input_event ( InputEvent event ) virtual
void	_input_text ( String text ) virtual
bool	_iteration ( float delta ) virtual
void	finish ( )
bool	idle ( float delta )
void	init ( )
void	input_event ( InputEvent event )
void	input_text ( String text )
bool	iteration ( float delta )

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Signals

on_request_permissions_result ( String permission, bool granted )

Emitted when a user responds to a permission request.

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Constants

NOTIFICATION_WM_MOUSE_ENTER = 1002

Notification received from the OS when the mouse enters the game window.

Implemented on desktop and web platforms.

NOTIFICATION_WM_MOUSE_EXIT = 1003

Notification received from the OS when the mouse leaves the game window.

Implemented on desktop and web platforms.

NOTIFICATION_WM_FOCUS_IN = 1004

Notification received from the OS when the game window is focused.

Implemented on all platforms.

NOTIFICATION_WM_FOCUS_OUT = 1005

Notification received from the OS when the game window is unfocused.

Implemented on all platforms.

NOTIFICATION_WM_QUIT_REQUEST = 1006

Notification received from the OS when a quit request is sent (e.g. closing the window with a "Close" button or Alt+F4).

Implemented on desktop platforms.

NOTIFICATION_WM_GO_BACK_REQUEST = 1007

Notification received from the OS when a go back request is sent (e.g. pressing the "Back" button on Android).

Specific to the Android platform.

NOTIFICATION_WM_UNFOCUS_REQUEST = 1008

Notification received from the OS when an unfocus request is sent (e.g. another OS window wants to take the focus).

No supported platforms currently send this notification.

NOTIFICATION_OS_MEMORY_WARNING = 1009

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

Specific to the iOS platform.

NOTIFICATION_TRANSLATION_CHANGED = 1010

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.

NOTIFICATION_WM_ABOUT = 1011

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

Specific to the macOS platform.

NOTIFICATION_CRASH = 1012

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

Implemented on desktop platforms if the crash handler is enabled.

NOTIFICATION_OS_IME_UPDATE = 1013

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.

NOTIFICATION_APP_RESUMED = 1014

Notification received from the OS when the app is resumed.

Specific to mobile platforms.

NOTIFICATION_APP_PAUSED = 1015

Notification received from the OS when the app is paused.

Specific to mobile 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.

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Method Descriptions

void _drop_files ( PoolStringArray files, int from_screen ) virtual

Called when files are dragged from the OS file manager and dropped in the game window. The arguments are a list of file paths and the identifier of the screen where the drag originated.

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void _finalize ( ) virtual

Called before the program exits.

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void _global_menu_action ( Variant id, Variant meta ) virtual

Called when the user performs an action in the system global menu (e.g. the Mac OS menu bar).

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bool _idle ( float delta ) virtual

Called each idle frame with the time since the last idle 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.

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void _initialize ( ) virtual

Called once during initialization.

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void _input_event ( InputEvent event ) virtual

Called whenever an InputEvent is received by the main loop.

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void _input_text ( String text ) virtual

Deprecated callback, does not do anything. Use _input_event to parse text input. Will be removed in Godot 4.0.

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bool _iteration ( float delta ) 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.

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void finish ( )

Should not be called manually, override _finalize instead. Will be removed in Godot 4.0.

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bool idle ( float delta )

Should not be called manually, override _idle instead. Will be removed in Godot 4.0.

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void init ( )

Should not be called manually, override _initialize instead. Will be removed in Godot 4.0.

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void input_event ( InputEvent event )

Should not be called manually, override _input_event instead. Will be removed in Godot 4.0.

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void input_text ( String text )

Should not be called manually, override _input_text instead. Will be removed in Godot 4.0.

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bool iteration ( float delta )

Should not be called manually, override _iteration instead. Will be removed in Godot 4.0.