I think there is an missing + in the SDL_manual, in the move handlers it should be
$paddle->( $paddle->y + ($v_y * $step ) );
If you get stuck, here is working code up to the point you are at now
#!/usr/bin/perl
use strict;
use warnings;
# These will allow us to use all the modules necessary to create a GUI
+.
# They are all parts of the Perl SDL module.
# The :: are use to seperate the name of the module and its correspond
+ing member.
use SDL;
use SDL::Events;
use SDLx::App;
use SDLX::Rect;
# First is to set up the screen.
# The => operator is similiar to a comma.
# but it treates the word to the left as a quoted word.
# Even though there isn't any quotes.
my $app = SDLx::App->new(
width => 500,
height => 500,
title => 'PONG',
dt => 0.02,
exit_on_quit => 1,
);
# The next step is to set up the paddles for each player.
# This is done in a hash reference.
# This is done so its possible to add information later.
# The numbers may need to be changed later to fit the paddles to the s
+creen.
# I am not 100% sure what -> actually does.
# Other than the fact its a deference operator.
# h is a shortened reference to height
my $player1 = {
paddle => SDLx::Rect->new( 10, $app->h / 2, 10, 40),
v_y => 0,
score => 0,
};
my $player2 = {
paddle => SDLx::Rect->new( $app->w - 20, $app->h / 2, 10, 40),
v_y => 0,
score => 0,
};
# This is to create the ball
my $ball = {
rect => SDLx::Rect->new( $app->w / 2, $app->h / 2, 10, 10 ),
v_x => -2.7,
v_y => 1.8,
};
# This is a show handler.
# This will render the objects to the screen.
$app->add_show_handler (
sub {
$app->draw_rect( [ 0, 0, $app->w, $app->h ], 0x000000FF );
$app->draw_rect( $ball->{rect}, 0xFF0000FF );
$app->draw_rect( $player1->{paddle}, 0xFF0000FF );
$app->draw_rect( $player2->{paddle}, 0xFF0000FF );
$app->update;
}
);
$app->add_move_handler( sub {
my ( $step, $app ) = @_;
my $paddle = $player1->{paddle};
my $v_y = $player1->{v_y};
$paddle->y( $paddle->y + ($v_y * $step) );
});
$app->add_move_handler( sub {
my ( $step, $app ) = @_;
my $paddle = $player2->{paddle};
my $v_y = $player2->{v_y};
$paddle->y( $paddle->y + ($v_y * $step) );
});
$app->add_move_handler( sub {
my ( $step, $app ) = @_;
my $ball_rect = $ball->{rect};
$ball_rect->x( $ball_rect->x + ($ball->{v_x} * $step) );
$ball_rect->y( $ball_rect->y + ($ball->{v_y} * $step) );
if ( $ball_rect->bottom >= $app->h ) {
$ball_rect->bottom( $app->h );
$ball->{v_y} *= -1;
}
elsif ( $ball_rect->top <= 0 ) {
$ball_rect->top( 0 );
$ball->{v_y} *= -1;
}
elsif ( $ball_rect->right >= $app->w ) {
$player1->{score}++;
$ball->{v_x} *= -1;
#reset_game();
#return;
}
elsif ( $ball_rect->left <= 0 ) {
$player2->{score}++;
$ball->{v_x} *= -1;
#reset_game();
#return;
}
});
$app->add_event_handler(
sub {
my ( $event, $app ) = @_;
if ( $event->type == SDL_KEYDOWN ) {
if ( $event->key_sym == SDLK_UP) {
$player1->{v_y} = -2;
}
elsif ( $event->key_sym == SDLK_DOWN ){
$player1->{v_y} = 2;
}
}
elsif ( $event->type == SDL_KEYUP) {
if (
$event->key_sym == SDLK_UP
or $event->key_sym == SDLK_DOWN
) {
$player1->{v_y} = 0;
}
}
}
);
$app->run;
poj
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