
=pod

=head1 NAME

SDLx::Controller::Interface - Interface Physics and Rendering with the Controller with callbacks

=head1 CATEGORY

Extension, Controller

=head1 SYNOPSIS

 use SDL;
 use SDLx::App;
 use SDLx::Controller::Interface;

 #SDLx::App is a controller
 my $app = SDLx::App->new(width => 200, height => 200 ); 

 my $ball = SDLx::Controller::Interface->new( x=> 10, y => 50, v_x => 10, v_y=> 20 );
 #Set the initial state of the ball's physics, this is optional

 $ball->set_acceleration( 
    sub { 
              my ($time, $current_state) = @_;
              return( 0, -10, 0 ); # Return accelerations (x,y,rotation)
        }
 );

 my $ball_render = sub {
       my $state = shift;
 
       $app->draw_rect( undef, 0 );
       $app->draw_rect( [$state->x, $state->y, 10,10], [255,0,0,255] );
       $app->update();
 };


 $ball->attach( $app, $ball_render, @params ); 

 $app->run();

 $ball->detach(); #can be called at anytime (for example when ball 'dies')

=head1 DESCRIPTION

=head1 METHODS

=head2 set_acceleration

Allows you to set the acceleration callback for defining the inferface's
behaviour in terms of x,y and rotation.

  $interface->set_acceleration ( 
      sub {
         my ($time, $current_state) = @_; 
       
         return ( $accel_x, $accel_y, $torque );
      }
  );

These accelerations are arbitary and can be set to any frame of reference.
Your render callback will handle how to interpret it.

The callback will receive the time and the current state as a
C<SDLx::Controller::State> element.

=head2 attach

Attaches the interface to a controller with a render callback

  $interface->attach( $controller, $render, @params );

Where $render is a callback that receives the interpolated
C<SDLx::Controller::State>.

  my $render = sub {
        my ($state, @params) = @_; 
        # draw the current $state.
  };

The @params are any extra parameters you would like to pass to the $render
callback.

=head2 current

  my $current_state = $interface->current();

Returns the current state of the interface as a C<SDLx::Controller::State>.

=head2 previous

  my $previous_state = $interface->previous();

Returns the previous state of the interface as a C<SDLx::Controller::State>.

=head2 detach

  $interface->detach();

If $interface has been C<attach()>'ed to any controller it will be detached now.

=head1 OTHER METHODS

Don't use these unless you really really want to.

=head2 acceleration

Call the acceleration callback once.

=head2 interpolate

Interpolate the current state

=head2 evaluate

Evaluate the new currrent and previous state.

=head2 update

Update the states by integrating with time.

=head1 AUTHORS

See L<SDL/AUTHORS>.

=cut
