[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. [code]godot -s my_loop.gd[/code]) or the [member ProjectSettings.application/run/main_loop_type] project setting is overwritten.
Called each physics frame with the time since the last physics frame as argument ([param delta], in seconds). Equivalent to [method Node._physics_process].
If implemented, the method must return a boolean value. [code]true[/code] ends the main loop, while [code]false[/code] lets it proceed to the next frame.
[b]Note:[/b] [param delta] will be larger than expected if running at a framerate lower than [member Engine.physics_ticks_per_second] / [member Engine.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 [method _process] and [method _physics_process]. As a result, avoid using [param delta] for time measurements in real-world seconds. Use the [Time] singleton's methods for this purpose instead, such as [method Time.get_ticks_usec].
Called each process (idle) frame with the time since the last process frame as argument (in seconds). Equivalent to [method Node._process].
If implemented, the method must return a boolean value. [code]true[/code] ends the main loop, while [code]false[/code] lets it proceed to the next frame.
[b]Note:[/b] [param delta] will be larger than expected if running at a framerate lower than [member Engine.physics_ticks_per_second] / [member Engine.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 [method _process] and [method _physics_process]. As a result, avoid using [param delta] for time measurements in real-world seconds. Use the [Time] singleton's methods for this purpose instead, such as [method Time.get_ticks_usec].
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 [method Object.tr].
[b]Note:[/b] 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.
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.
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.
