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How can I create an arc (-style=>'chord') with an arrow on the end, in a Perl-Tk canvas?

This sounded like a simple thing for me to answer. It's turning into a quagmire. Here's where I've been so far:

  • Arrow option on $can->createArc()? Nope - arrow option on line items only.
  • Make an arc out of a bunch of lines (needed to ask in CB for math formula).
  • Duh, CB suggestion to put a small line on end of arc, with arrow! Good thinking..., but wait - I can't figure out how to do this, since there's no way I know of to get the coords of the end of the arc to attach a line to (you only get coords of a rectangle that encloses the arc). Back to bunch-o-lines strategy.
  • Built bunch-o-lines prototype (see attached), but arrowhead doesn't follow curve, and there's no way to rotate the arrowhead.
  • Thinking I could create a really short line right at the end, that orients the arrow in the correct direction. Started thinking there has to be a better way. Decided to ask for Monk's help.

    Any thoughts are much appreciated.

    Thanks

    -Craig 

    use strict;
use warnings;

use Tk;
my $top = MainWindow->new;
my $can = $top->Canvas()->pack();

my @offset = (100, 100);

my $PI = atan2(1,1) * 4;
my $max = 100;
my $radius = 20;

my @coords;

foreach my $i (1..$max-30) {
    push(@coords, _circleCoord($i*2*$PI/$max, $radius));
}

$can->createLine(@coords, -arrow=>'last',
    #-arrowshape=>[10, 15, 9],    # Goofy arrowhead - this  helps
    tags=>['SELFARROW']);
$can->move('SELFARROW', @offset);

MainLoop;

sub _circleCoord {
    my $radians = shift || die "Missing radians";
    my $radius = shift || die "Missing radius";

    my @coords;
    push(@coords, ($radius * sin($radians)));
    push(@coords, ($radius * cos($radians)));
    return(@coords);
}

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    In reply to Tk:Canvas - Arc with an arrow? by cmv

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