#!/usr/bin/perl

use strict;
use warnings;
use Tk;

my $mw = tkinit( -title => 'timeline' );

my $c = $mw->Scrolled(
    Canvas =>
    -scrollbars => 'soe',
    -width => 500,
    -height => 400,
    -background => 'white',
)->pack(
    -fill => 'both',
    -expand => 1,
)->Subwidget('scrolled');

my @data = (
    time - 60 * 60 * 24 * 7 * 4,
        [ 'Anfang' ],
    time - 60 * 60 * 24 * 7 * 3,
        [ 'Termin', 'Termin 2' ],
    time - 60 * 60 * 24 * 7 * 2,
        [ 'Mitte' ],
    time - 60 * 60 * 24 * 7 * 1,
        [ 'Termin 3', 'Termin 4' ],
    time - 60 * 60 * 24 * 7 * 0,
        [ 'Ende' ],
);

my $scrltop = $c->createTimeline(
    0, 400,
    500, 400,
    \@data,
);

$c->configure( -scrollregion => [ -100, $scrltop-15, 600, 415 ] );

MainLoop;

sub Tk::Canvas::createTimeline {
    my( $self, $x0, $y0, $x1, $y1, $data ) = @_;
    
    my $xstep = @$data > 2 ? ($x1 - $x0) / ($data->[-2] - $data->[0])
                           : die "Timeline: Not enough data specified!\n";
    
    # create x-axe:
    $self->createLine(
        $x0, $y0, $x1, $y1,
        -fill => 'black',
        -arrow => 'last',
    );
    
    my $scrltop = $y0;
    
    # plot data:
    for ( my $i = 0; $i < @$data; $i += 2 ) {
        my( $x, $y ) = @{$data}[$i,$i+1];
        
        my $xpos = ($x - $data->[0]) * $xstep;
        
        # create x-axe-label:
        $self->createLine(
            $xpos, $y1,
            $xpos, $y1+3,
            -fill => 'black',
        );
        $self->createText(
            $xpos, $y1+15 + ($i/2 % 2 ? 0 : 15),
            -anchor => 'center',
            -text => scalar localtime $x,
            -fill => 'black',
        );
        
        # plot events:
        for ( my $j = 0; $j < @$y; $j++ ) {
            $self->createText(
                $xpos, $y1 - $j * 24 - ($i/2 % 2 ? 24 : 12),
                -anchor => 'center',
                -text => $y->[$j],
                -fill => 'black',
            );
        } # for
        
        # update $scrltop:
        my $yh = $y1 - $#{$y} * 24 - ($i/2 % 2 ? 24 : 12);
        $scrltop = $yh if $yh < $scrltop;
    } # for
    
    # return top-coordinate:
    return $scrltop;
} # Tk::Canva::createTimeline