The Ecore Main Loop

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The Ecore Main Loop

# What is Ecore?

Ecore is a clean and tiny event loop library with many modules to do lots of convenient things for a programmer to save time and effort. It's small and lean, designed to work from embedded systems all the way up to large and powerful multi-cpu workstations. The main loop has a number of primitives to be used with its main loop. It serializes all the primitives and allows for great responsiveness without the need for threads(or any other concurrency).

## Timers

Timers serve two main purposes: doing something at a specified time and repeatedly doing something with a set interval.

See also
  Ecore Timer functions

## Pollers

Pollers allow for polling to be centralized into a single place therefore alleviating the need for different parts of the program to wake up at different times to do polling, thereby making the code simpler and more efficient.

See also
  Ecore Poll functions

## Idlers

There are three types of idlers: enterers, idlers(proper) and exiters. They are called, respectively, when the program is about to enter an idle state, when the program is idle, and when the program is leaving an idle state. Idler enterers are usually a good place to update the program state. Proper idlers are the appropriate place to do heavy computational tasks thereby using what would otherwise be wasted CPU cycles. Exiters are the perfect place to do anything your program should do just before processing events (also timers, pollers, file descriptor handlers and animators)

See also
  Ecore Idle functions

## File descriptor handlers

File descriptor handlers allow you to monitor when there is data available to read on file descriptors, when writing will not block, or if there was an error. Any valid file descriptor can be used with this API, regardless of if was gotten with an OS specific API or from ecore.

See also
  File Descriptor Handling Functions

## Animators

Ecore provides a facility called animators, so named since the intended use was in animations, that facilitates knowing what percentage of a given interval has elapsed. This is perfect for performing animations, but is not limited to that use, it can, for example, also be used to create a progress bar.

See also
  Ecore Animator functions

## Event handlers

Event handlers are, arguably, the most important feature of the ecore main loop, they are what allows the programmer to easily handle user interaction. Events however are not only things the user does, events can represent anything for which a type is created.

See also
  Ecore Event functions All of these primitives are discussed in more detail in their respective pages linked above.

Here is a diagram of the main loop flow of a simple program:

# How does Ecore work?

Ecore is very easy to learn and use. All the function calls are designed to be easy to remember, explicit in describing what they do, and heavily name-spaced. Ecore programs can start and be very simple.

For example:

#include <Ecore.h>
int
main(int argc, const char **argv)
{
ecore_init();
ecore_app_args_set(argc, argv);
ecore_main_loop_begin();
ecore_shutdown();
return 0;
}
ecore_app_args_set
void ecore_app_args_set(int argc, const char **argv)
Sets up the programs command-line arguments.
Definition ecore_app.c:15
ecore_shutdown
EAPI int ecore_shutdown(void)
Shuts down connections, signal handlers sockets etc.
Definition ecore.c:371
ecore_init
EAPI int ecore_init(void)
Sets up connections, signal handlers, sockets etc.
Definition ecore.c:230
ecore_main_loop_begin
void ecore_main_loop_begin(void)
Runs the application main loop.
Definition ecore_main.c:1316

This program is very simple and doesn't check for errors, but it does start up and begin a main loop waiting for events or timers to tick off. This program doesn't set up any, but now we can expand on this simple program a little more by adding some event handlers and timers.

#include <Ecore.h>
Ecore_Timer *timer1 = NULL;
Ecore_Event_Handler *handler1 = NULL;
double start_time = 0.0;
int
timer_func(void *data)
{
printf("Tick timer. Sec: %3.2f\n", ecore_time_get() - start_time);
return ECORE_CALLBACK_RENEW;
}
int
exit_func(void *data, int ev_type, void *ev)
{
Ecore_Event_Signal_Exit *e;
e = (Ecore_Event_Signal_Exit *)ev;
if (e->interrupt) printf("Exit: interrupt\n");
else if (e->quit) printf("Exit: quit\n");
else if (e->terminate) printf("Exit: terminate\n");
ecore_main_loop_quit();
return 1;
}
int
main(int argc, const char **argv)
{
ecore_init();
ecore_app_args_set(argc, argv);
start_time = ecore_time_get();
handler1 = ecore_event_handler_add(ECORE_EVENT_SIGNAL_EXIT, exit_func, NULL);
timer1 = ecore_timer_add(0.5, timer_func, NULL);
ecore_main_loop_begin();
ecore_shutdown();
return 0;
}
ECORE_EVENT_SIGNAL_EXIT
#define ECORE_EVENT_SIGNAL_EXIT
Exit signal event.
Definition Ecore_Common.h:565
Ecore_Event_Handler
struct _Ecore_Event_Handler Ecore_Event_Handler
A handle for an event handler.
Definition Ecore_Common.h:576
ecore_event_handler_add
Ecore_Event_Handler * ecore_event_handler_add(int type, Ecore_Event_Handler_Cb func, const void *data)
Adds an event handler.
Definition ecore_events.c:13
ECORE_CALLBACK_RENEW
#define ECORE_CALLBACK_RENEW
Return value to keep a callback.
Definition Ecore_Common.h:153
ecore_main_loop_quit
void ecore_main_loop_quit(void)
Quits the main loop once all the events currently on the queue have been processed.
Definition ecore_main.c:1326
ecore_time_get
double ecore_time_get(void)
Retrieves the current system time as a floating point value in seconds.
Definition ecore_time.c:33
ecore_timer_add
Ecore_Timer * ecore_timer_add(double in, Ecore_Task_Cb func, const void *data)
Creates a timer to call the given function in the given period of time.
Definition ecore_timer.c:189
Ecore_Timer
Eo Ecore_Timer
A handle for timers.
Definition Ecore_Common.h:3079
_Ecore_Event_Signal_Exit
A structure that stores information of an Exit request event.
Definition Ecore_Common.h:637
_Ecore_Event_Signal_Exit::interrupt
Eina_Bool interrupt
Set if the exit request was an interrupt signal.
Definition Ecore_Common.h:638
_Ecore_Event_Signal_Exit::quit
Eina_Bool quit
set if the exit request was a quit signal
Definition Ecore_Common.h:639
_Ecore_Event_Signal_Exit::terminate
Eina_Bool terminate
Set if the exit request was a terminate signal.
Definition Ecore_Common.h:640

In the previous example, we initialize our application and get the time at which our program has started so we can calculate an offset. We set up a timer to tick off in 0.5 seconds, and since it returns 1, will keep ticking off every 0.5 seconds until it returns 0, or is deleted by hand. An event handler is set up to call a function - exit_func(), whenever an event of type ECORE_EVENT_SIGNAL_EXIT is received (CTRL-C on the command line will cause such an event to happen). If this event occurs it tells you what kind of exit signal was received, and asks the main loop to quit when it is finished by calling ecore_main_loop_quit().

The handles returned by ecore_timer_add() and ecore_event_handler_add() are only stored here as an example. If you don't need to address the timer or event handler again you don't need to store the result, so just call the function, and don't assign the result to any variable.

This program looks slightly more complex than needed to do these simple things, but in principle, programs don't get any more complex. You add more event handlers, for more events, will have more timers and such, BUT it all follows the same principles as shown in this example.