Engine

The Engine class represents top-level static methods that assist in many aspects of game development.

• switch_level()
• quit()
• fps_limit
• delta
• time
• fps
• info
• get_class()
• timestep=
• timestep_percent
• process_frame
• argv
• using_pak
• profile_error_estimate
• profile_fn
• delta_max

switch_level

static switch_level(level)

Parameters

• level -> Level level to switch to

Switches the current level to level. level must be an instance of a class that inherits from Level and implements all its methods.

After this method is called the current frame will finish execution, then the current level’s destruction method will be called before the new level’s creation method.

quit

static quit()

Forces the game to exit. The game will finish executing the current frame, then the level’s destruction method will be called before all resources are cleaned up and program closes. This method is also implicitly called when the user closes the game window.

fps_limit

Write Only: static fps_limit=(fps)

Variable Type: Num - target framerate

Forces the engine to process no more than fps frames a second. If fps is 0, there will be no limit on framerate.

If you set the screen mode to SCREEN_MODE_VSYNC, the framerate will be capped at the monitor’s refresh rate (typically 60) regardless of what you set with this function.

timestep=

Write Only: timestep=(timestep)

Variable Type: Num - How many times process_frame should be set to true each second.

For fixed-timestep logic. This controls how many times each second that process_frame will be set to true to let the user handle their own fixed-timestep code. Level’s update method will only update entities when process_frame is true automatically. Set this to 0 (the default) to disable fixed-timestep.

Do not set this value before the first level is initialized; ie, in init.wren.

timestep_percent

Read Only: timestep_percent

Variable Type: Num

How far (hypothetically) we are through this current second for fixed timestep interpolation.

process_frame

Read Only: process_frame

Variable Type: Bool

Returns true if this frame is meant to be processed for fixed timestep games, always returns true if timestep is 0.

delta

Read Only: static delta

Variable Type: Num

Returns the time in seconds the last frame took to process. This is typically useful when making game logic not bound to framerate.

time

Read Only: static time

Variable Type: Num

Returns the time seconds since the engine initialized.

fps

Read Only: static fps

Variable Type: Num

Returns the average framerate over the last second.

info

Read Only: static info

Variable Type: Map

Returns a map containing information about the engine, the map will contain the following keys:

• name - A string containing the name of the engine.
• wren-version - Number representing the version of Wren the engine was built with.
• astro-version - A list representing the engine’s version in the form [major, minor, patch].
• build-date - Date the engine was built on as a string.

get_class

static get_class(class_name)

Parameters

• class_name -> String Class name in the form module::class.

This method finds a variable in a module and returns it, or returns null if the variable/module does not exist.

argv

Read Only: static argv

Variable Type: List - List of command line parameters given to the program on startup.

using_pak

Read Only: static using_pak

Variable Type: Bool - True if Astro is using a game.pak file.

profile_error_estimate

static profile_error_estimate(trials)

Parameters

• trials -> Num Number of trials to perform.

This method attempts to find the overhead associated with a for loop on the host machine. It will run an empty for loop a given amount of times and return the average time per iteration in microseconds.

profile_fn

static profile_fn(function, trials)

Parameters

• function -> Fn Function to profile, should require no parameters.
• trials -> Num Number of trials to perform.

Profiles a given function by running it trials amount of times - more trials will produce more reliable numbers. This method will return a list in the format

[total time in seconds, average time in microseconds, trial count]

Because function is called in a for loop, you may use profile_error_estimate to estimate how much of the average time is just the overhead associated with the for loop. Because how fast you are able to run something is dependent on the host machine, the results are only useful in comparison to other results and because this is being executed in a VM there is a little bit of error associated with all of the results. Do not take these numbers as law, they are a decent estimate that is useful to compare algorithms but it is not a completely reliable software testing tool.

delta_max

Write Only: static delta_max

Variable Type: Num

By default this is zero, meaning there is no cap on the delta time. If set to something other than 0 delta will not return anything higher than this value.