#!/usr/bin/perl -w
# tcapdemo - show off direct cursor placement

use POSIX;
use Term::Cap;
    
init();                     # Initialize Term::Cap.
zip();                      # Bounce lines around the screen.
finish();                   # Clean up afterward.
exit();

# Two convenience functions.  clear_screen is obvious, and
# clear_end clears to the end of the screen.
sub clear_screen { $tcap->Tputs('cl', 1, *STDOUT) } 
sub clear_end    { $tcap->Tputs('cd', 1, *STDOUT) } 

# Move the cursor to a particular location.
sub gotoxy {
    my($x, $y) = @_;
    $tcap->Tgoto('cm', $x, $y, *STDOUT);
} 

# Get the terminal speed through the POSIX module and use that
# to initialize Term::Cap.
sub init { 
    $| = 1;
    $delay = (shift() || 0) * 0.005;
    my $termios = POSIX::Termios->new();
    $termios->getattr;
    my $ospeed = $termios->getospeed;
    $tcap = Term::Cap->Tgetent ({ TERM => undef, OSPEED => $ospeed });
    $tcap->Trequire(qw(cl cm cd));
}

# Bounce lines around the screen until the user interrupts with
# Ctrl-C.
sub zip { 
    clear_screen();
    ($maxrow, $maxcol) = ($tcap->{_li} - 1, $tcap->{_co} - 1);

    @chars = qw(* - / | \ _ );
    sub circle { push(@chars, shift @chars); }

    $interrupted = 0;
    $SIG{INT} = sub { ++$interrupted };

    $col = $row = 0;
    ($row_sign, $col_sign) = (1,1);

    do {
        gotoxy($col, $row);
        print $chars[0];
        select(undef, undef, undef, $delay);

        $row += $row_sign;
        $col += $col_sign;

        if    ($row == $maxrow) { $row_sign = -1; circle; } 
        elsif ($row == 0 )      { $row_sign = +1; circle; }

        if    ($col == $maxcol) { $col_sign = -1; circle; } 
        elsif ($col == 0 )      { $col_sign = +1; circle; }
    
    } until $interrupted;

}

# Clean up the screen.
sub finish { 
    gotoxy(0, $maxrow);
    clear_end();
}