NAME
SDLx::Controller - Handles the loops for event, movement and rendering
SYNOPSIS
use SDLx::Controller
# create our controller object
my $app = SDLx::Controller->new;
# register some callbacks
$app->add_event_handler( \&on_event );
$app->add_move_handler( \&on_move );
$app->add_show_handler( &on_show );
# run our game loop
$app->run;DESCRIPTION
The core of a SDL application/game is the main loop, where you handle events and display your elements on the screen until something signals the end of the program. This usually goes in the form of:
while (1) {
...
}The problem most developers face, besides the repetitive work, is to ensure the screen update is independent of the frame rate. Otherwise, your game will run at different speeds on different machines and this is never good (old MS-DOS games, anyone?).
One way to circumveint this is by capping the frame rate so it's the same no matter what, but this is not the right way to do it as it penalizes better hardware.
This module provides an industry-proven standard for frame independent movement. It calls the movement handlers based on time (tick counts) rather than frame rate. You can add/remove handlers and control your main loop with ease.
METHODS
new
new( dt => 0.5 )
Controller construction. Optional dt parameter indicates delta t times in which to call the movement handlers, and defaults to 0.1.
Returns the new object.
run
After creating and setting up your handlers (see below), call this method to activate the main loop. The main loop will run until an event handler returns undef.
All hooked functions will be called during the main loop, in this order:
Please refer to each handler below for information on received arguments.
add_event_handler
Register a callback to handle events. You can add as many subs as you need. Whenever a SDL::Event occurs, all registered callbacks will be triggered in order. Returns the order queue number of the added callback.
The first (and only) argument passed to registered callbacks is the SDL::Event object itself, so you can test for $event->type, etc.
Each event handler is required to return a defined value for the main loop to continue. To exit the main loop (see "run" above), return undef or nothing at all.
add_move_handler
Register a callback to update your objects. You can add as many subs as you need. Returns the order queue number of the added callback.
All registered callbacks will be triggered in order for as many dt as have happened between calls. You should use these handlers to update your in-game objects, check collisions, etc.
The first (and only) argument passed is a reference to the dt value itself, so you can check and/or update it as necessary.
Any returned values are ignored.
add_show_handler
Register a callback to render objects. You can add as many subs as you need. Returns the order queue number of the added callback.
All registered callbacks will be triggered in order, once per run of the main loop. The first (and only) argument passed is the number of ticks since the previous round.
quit
Exits the main loop. Calling this method will cause run to return.
remove_move_handler( $index )
remove_event_handler( $index )
remove_show_handler( $index )
Removes the handler with the given index from the respective calling queue.
Returns the removed handler.
remove_all_move_handlers
remove_all_event_handlers
remove_all_show_handlers
Removes all handlers from the respective calling queue.
remove_all_handlers
Quick access to removing all handlers at once.
AUTHORS
Kartik Thakore
Breno G. de Oliveira
ACKNOWLEGDEMENTS
The idea and base for this module comes from Lazy Foo's Frame Independent Movement tutorial, and Glenn Fiedler's Fix Your Timestep article on timing.