Magic Lantern Lua API Documentation

Startup

The scripting engine looks for scripts in ML/SCRIPTS. Scripts should end with .LUA.

There are two types of scripts "simple" and "complex". "Simple" scripts do not define custom menus, don't leave any background tasks running, or any event or property handlers registered when they finish loading. The user will be able to execute such scripts from the 'Scripts' menu and they will not autorun when the camera starts. Also, such scripts will be 'unloaded' when they're not actively running, which will help conserve memory.

"Complex" scripts are any scripts that define custom menus, start background task(s), or leave event or property handlers registered when they finish loading. These scripts cannot be unloaded; they will run in background until the camera is turned off.

Tasks, event handlers and property handlers are allowed in simple scripts as long as they are cleaned up before the main task exits (that is, the top-level code from your script). See unload.lua and api_test.lua for examples.

Menus

All script will appear in the 'Scripts' menu. Scripts can be run from here and autorun can be toggled on or off. Scripts can also define their own menu(s) elsewhere if they need extra settings or parameters. See: menu, copy2m.lua, menutest.lua, recdelay.lua.

State

For "complex" scripts, the scripting engine will maintain your script's global state for as long as the camera is powered on. So any global variables you declare will persist until the camera is turned off. "Simple" scripts are unloaded when they finish executing, so global state is lost when the script is executed again (if you need to persist information from run to run, you can use file I/O).

Each script gets it's own Lua state (virtual machine). If you would like scripts to share a state, have only one of the scripts in the ML/SCRIPTS folder, and have it call the other scripts with dofile() or require()

Tasks (threading)

"Preemptive" multithreading is not allowed within a single lua state, so only one thread of execution is allowed to be running in your script at a given time. Any attempts by other tasks to call functions in your scripts (e.g. via event handlers) will block until the current execution completes (or yields) or some timeout is reached (this is achieved by the scripting backend making use of semaphores). (Separate scripts may run at "the same time" since they have separate lua states)

The scripting engine will load and run scripts in a separate task created explicitly to load scripts. If a script blocks during loading, it will prevent other subsequent scripts from loading.

Different event and menu handlers get called from different ML or Canon tasks, and scripts may start their own tasks. A script may yield it's execution to some other task that is calling the script by calling task.yield. Execution is automatically yielded when the script returns from a call.

When writing a script, you should be mindful of the context (task) from which your script is running, and consider when it might be appropriate to start something in a separate task (to keep from blocking some ML or Canon task), or when to yield (to keep the script from blocking itself).

See: task, api_test.lua, unload.lua, recdelay.lua, calc.lua, editor.lua.

Library Scripts

You can write re-usable script code as a "library" by saving it as a .lua file in ML/SCRIPTS/LIB The require function will search for libraries (or "packages") here. As with regular scripts make sure to use valid 8.3 filenames. For a library called ML/SCRIPTS/LIB/MYLIB.LUA, load it by calling require("MYLIB"). For example, see config.lua and keys.lua, which are 'library' scripts included in this API.

Canon Properties

Canon firmware manages many settings via what it refers to as "properties". We can set handlers to recieve notificatons when properties change and we can send requests to change their values. One must be very careful when doing so, because Canon firmware persists this properties in NVRAM, and setting invalid values can 'soft-brick' the camera.

'Safe' getters and setters for some of the more common of these properties are available in sereveral of the modules, mainly camera and lens. You can register handlers for properties with the property module. Property handlers are run in a seprate task, so you can take as much time as you like without worrying about blocking Canon code, but doing so will block subsequent property handlers.

Errors

Unhandled errors are logged to the "console". You can turn it on from Scripts > Show Console. This is also where you will see the output of the print() function. You can also implement your own error handling, see editor.lua.

Standard Libraries

All of the standard Lua libraries are available except os (replaced by dryos):

Modules

event Event Handlers.
battery Battery properties.
camera Basic camera operations and properties
console Functions for writing data to the console
constants Constants
display Display and bmp drawing functions
dryos DryOS operating system functions.
global Global Functions
interval Intervalometer operations and properties.
key Key functions
lens Lens functions
lv LiveView functions
menu Functions for interacting with the ML menu.
movie Movie functions
property Canon Properties
task Task functions
config Functions for saving/loading config data
keys Helper for dealing with keypresses
logger Logging helper.

Examples

api_test.lua
calc.lua
copy2m.lua
editor.lua
hello.lua
config.lua
keys.lua
logger.lua
strict.lua
menutest.lua
pong.lua
recdelay.lua
scrnshot.lua
sokoban.lua
unload.lua
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