Detailed Description

A context stores information that influences the execution of steps and sequences, namely:

A list of variables that can be im-/exported into steps.
An initialization function (in C++) that is called on a Lua state before a step is executed.
A step setup script (in Lua) that is executed before a step is executed. Global variables and functions defined in this step setup script can be accessed by the Lua script in the step. When a sequence is executed, this step setup script is overwritten with the one from the sequence.
A callback that is invoked whenever a message is being processed by the execution engine (see below for details).

Message callback function

The Context contains a message_callback_function that is called once for each message that is being processed by the execution engine in the main thread. By default, this function will send the output of the Lua "print()" command and error messages to stdout (see default_message_callback()). However, message_callback_function can also be set to nullptr (to disable any special behavior) or to a custom function:

void my_message_callback(const Message& msg)
{
    if (msg.get_type() == Message::Type::output)
        send_to_console(msg.get_text());
    else if (msg.get_type() == Message::Type::sequence_stopped_with_error)
        show_alert_box(msg.get_text());
}
 
Context context;
context.message_callback_function = my_message_callback;

The callback function receives a reference to the message that is being processed. If a sequence is executed in the current thread (e.g. via Sequence::execute()), the callback is executed whenever a message is generated. If the sequence is handed to an Executor for parallel execution, the callback is run whenever the main thread has received the message (i.e. typically within Executor::update()). Callbacks are never executed on the worker thread.

#include <Context.h>

Public Attributes
VariableTable	variables
	A map of variables (names and values) that can be im-/exported into steps. More...

std::string	step_setup_script = ""
	Step setup script with common functions or constants like a small library. More...

std::function< void(sol::state &)>	step_setup_function
	An initialization function that is called on a Lua state before a step is executed. More...

MessageCallback	message_callback_function = default_message_callback
	A callback (or "hook") function that is invoked whenever a message is processed during the execution of a sequence. More...