Figure C-3. clock-bezier.ppl

#!/usr/local/bin/perl -w
#
# This most entertaining program was written in Tcl/Tk by Scott Hess
# (shess@winternet.com).  It's a clock that uses a bezier curve anchored
# at four points—the hour position, the minute position, the second
# position and the center of the clock—to show the time.
#
# <Button-1> switches between display modes, and <Button-2> switches
# between line thicknesses.
#
# Perl/Tk version by Stephen.O.Lidie@Lehigh.EDU, 2000/02/05.

use POSIX qw/asin/;
use Tk;
use subs qw/buildclock hands setclock/;
use vars qw/$clock %hand $mw $pi180 $resize/;
use strict;

%hand = (
    hour    => 0.40,
    minute  => 0.75,
    second  => 0.85,
    0       => 0.00,
    intick  => 0.95,
    outtick => 1.00,
    width   => 0.05,
    scale   => 100,

    type    => 'bezier',
    types   => [qw/normal curve angle bezier/],
    tindx   => 3,
    normal  => [qw/minute 0 0 second 0 0 hour 0 0 minute/],
    curve   => [qw/minute 0 second 0 hour 0 minute/],
    angle   => [qw/minute second second hour/],
    bezier  => [qw/minute second 0 hour/],
    
    tick    => [qw/intick outtick/],
);
$pi180 = asin(1) / 90.0;
$resize = 0;

$mw = MainWindow->new;
$clock = $mw->Canvas(qw/-width 200 -height 200/);
$clock->pack(qw/-expand 1 -fill both/);
$mw->bind('<Configure>' => \&buildclock);
$mw->bind('<Button-1>'  => \&incrtype);
$mw->bind('<Button-2>'  => \&incrwidth);
buildclock;
$mw->repeat(1000 => sub {my(@t) = localtime; setclock @t[0 .. 2]});
MainLoop;

sub buildclock  {

    # Build the clock.  Puts tickmarks every 30 degrees, tagged
    # "ticks", and prefills the "hands" line.

    my $pi180 = asin(1)/90.0;
    
    Tk::catch {$clock->delete('marks')};
    $clock->update;
    my $w = $clock->width;
    $mw->geometry("${w}x${w}") if $resize; # ensure clock is square
    $resize++;
    $hand{scale} = $w / 2.0;
    
    # This is a horrid hack.  Use the hands( ) procedure to
    # calculate the tickmark positions by temporarily changing
    # the clock type.
    
    my $type = $hand{type};
    $hand{type} = 'tick';
    my %angles;
    for (my $ii = 0; $ii < 12; $ii++) {
        $angles{intick} = $angles{outtick} = $ii * 30 * $pi180;
        $clock->createLine(hands(\%angles), -tags => [qw/ticks marks/]);
    }
    $hand{type} =  $type;
    
    $clock->createLine(qw/0 0 0 0 -smooth 1 -tags/ => [qw/hands marks/]);
    $clock->itemconfigure(qw/marks -capstyle round -width/ =>
              $hand{width} * $hand{scale});
}

sub hands {

    # Calculate the set of points for the current hand type and
    # the angles in the passed array.

    my($aa) = @_;

    my $ss = $hand{scale};
    my @points;
    foreach my $desc ( @{ $hand{$hand{type}} } ) {
        push @points, sin($aa->{$desc}) * $hand{$desc} * $ss + $ss;
        push @points, $ss - cos($aa->{$desc}) * $hand{$desc} * $ss;
    }
    #print join(', ', @points), "\n";
    return @points;
}

sub incrtype {
    $hand{type} = $hand{types}->[ ++$hand{tindx} % @{$hand{types}} ];
}

sub incrwidth {
    my $w = $hand{width} + .05;
    $hand{width} = $w > .25 ? 0 : $w;
    $clock->itemconfigure('marks', -width => $hand{width} * $hand{scale});
}

sub setclock {

    # Calculate the angles for the second, minute, and hour hands,
    # and then update the clock hands to match.

    my($second, $minute, $hour) = @_;

    my %angles;
    $angles{0}      = 0;
    $angles{second} = $second *  6 * $pi180;
    $angles{minute} = $minute *  6 * $pi180;
    $angles{hour}   = $hour   * 30 * $pi180 + $angles{minute} / 12;

    my $sector  = int( $angles{second} + 0.5 );
    my(@colors) = qw/cyan green blue purple red yellow orange/;
    $clock->itemconfigure(qw/hands -fill/ => $colors[$sector]);

    $clock->coords('hands',  hands \%angles);
}

C.10. Robot Control Program complex.ptr		C.12. tkhanoi.ppl