Recipe 15.21 Program: Small termcap Program

15.21.1 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 15-8.

Example 15-8. 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:

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

15.21.2 See Also

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