sub draw_coordinates {
	my ($pboard) = @_;

	# Delete existing coordinate text
	my $canvas = $pboard->{'canvas'};
	my $ptext  = $pboard->{'text'};
	map { my_delete($canvas, $_) } @$ptext;
	$pboard->{'text'} = [ ];

	for (my $i = 0; $i < $ncols; $i++) {
		my $x = $borderx + $i * $cellx + $i * $linex + $linex / 2;
		for (my $j = 0; $j < $nrows; $j++) {
			my $y = $bordery + $j * $celly + $j * $liney + $liney / 2;
			my @opts = ($x, $y, -text => coor_to_square([$i, $j]));
			push @opts, -anchor => 'nw';
			($coor_font || 0) and push @opts, -font => $coor_font;
			my $id = my_create($canvas, "createText", [@opts]);
			push @$ptext, $id;
		}
	}
}