Add tool for spreading tasks across frames

[timothyqiu]

Tasks like pathfinding and enemy AI are heavy but usually do not require high immediacy. When there are a large number of characters in the scene that need to perform such tasks, to reduce the overhead per frame, a common practice is to spread these tasks across a number of frames.

For example, out of 1000 enemies, 100 enemies are processed per frame, and the round is completed in 10 frames. Or a limit is set for the processing time of each frame, and as many tasks as possible are executed per frame.

Example usage:

if get_tree().is_spreading_task_completed(path_finding_task):
    path_finding_task = get_tree().submit_spreading_task(TASK_PHYSICS_PROCESS, enemies, func (enemy):
        # won't be called if enemy is freed
        do_path_finding(enemy)
    ))
    get_tree().set_spreading_task_elements_per_frame(path_finding_task, 100)  # 100 enemies per frame
    get_tree().set_spreading_task_time_per_frame(path_finding_task, 100)  # max 100 ms per frame
    get_tree().bind_spreading_task(path_finding_task, self)  # kill the task if self is freed (e.g., current scene)

[Calinou]

• Related to Add a Node property to specify a reduced processing rate #12371.

I proposed a way to do it in there. It's not perfect, but doesn't require any central processing in SceneTree or another singleton.

[timothyqiu]

It's in SceneTree so tasks don't have to be node-related. e.g., data processing / io.

The first argument in the example code means when to run the lambda.