15.18. Program: Small termcap program

Description

This program clears your screen and scribbles all over it until you interrupt it. It shows how to use Term::Cap to clear the screen, move the cursor, and write anywhere on the screen. It also uses Recipe 16.6 .

The program text is shown in Example 15.9 .

Example 15.9: tcapdemo

#!/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();
}



This is what it looks like in mid-run:

*     _                       /     |                       \     -
 *   _ \                     - /   | /                     | \   - *
  * _   \                   -   / |   /                   |   \ -   *
   *     \                 -     |     /                 |     -     *
  _ *     \               -     | /     /               |     - \     *
 _   *     \             -     |   /     /             |     -   \     *
*     *     \           -     |     /     /           |     -     \     *
 *     *     \         -     |       /     /         |     -       \     *
  *     *     \       -     |         /     /       |     -         \     *
   *     *     \     -     |           /     /     |     -           \     *
    *     *     \   -     |             /     /   |     -             \     *
     *     *     \ -     |               /     / |     -               \     
      *     -     \     |                 /     /     -                 \    
       *   - *   - \   |                   /   | /   -                   \   
        * -   * -   \ |                     / |   / -                     \ _
         -     -     \                       |     /                       _

See Also

termcap (5) (if you have it); the documentation for the standard Term::Cap module


Previous: 15.17. Removing the DOS Shell Window with Windows Perl/Tk Perl Cookbook Next: 15.19. Program: tkshufflepod
15.17. Removing the DOS Shell Window with Windows Perl/Tk Book Index 15.19. Program: tkshufflepod