init () initializes the backend

Exceptions:

• Failure if initialization fails

run k executes the backend event loop, calling update functions as needed, and calling the continuation function k when the event loop terminates. Note that the call to run MUST be the last instruction in your program (to avoid different behaviors between the native and javascript backends). If you need to perform additional stuff when the program terminates, you MUST use the k function: it is meant for that. Note that calling run from an update function will just be ignored (though this should not be done). However, run may be called from the k function, if needed.

Exceptions:

• Exception.Not_initialized if Backend.init was not called

stop () requests termination of the currently running event loop, if any. It should be called from an update function. Actual termination of the event loop will occur at the end of the current iteration of the event loop, so after calling stop an update function should proceed normally until it returns.

Exceptions:

• Exception.Not_initialized if Backend.init was not called

getCanvas i returns the canvas that has id i, if it exists

Exceptions:

• Exception.Not_initialized if Backend.init was not called
• Not_found if no canvas has id i

getCurrentTimestamp () returns the current timestamp in microseconds, from an arbitrary starting point

Exceptions:

• Exception.Not_initialized if Backend.init was not called