This is close enough

sub bboxwh {
    my( $g ) = @_;
    my @xx; 
    my @yy;
    for my $k ( $g->getChildren ){
        my %att =  $k->getAttributes ;
        my $swid = eval { $att{style}{"stroke-width"} } || 0;
        my $points = $att{points};
        $points or next;
        for my $xy ( split ' ', $points){
            my( $xx, $yy ) = split ',', $xy;
            push @xx, $xx; push @yy, $yy;
## account for swid??
        }
    }
    @xx = sort { $a <=> $b } @xx;
    @yy = sort { $a <=> $b } @yy;
    my $minx = $xx[ 0  ];
    my $miny = $yy[ 0  ];
    my $maxx = $xx[ -1 ];
    my $maxy = $yy[ -1 ];
    my $w = $minx < 0 ? abs($minx)+$maxx : abs( $minx - $maxx );
    my $h = $miny < 0 ? abs($miny)+$maxy : abs( $miny - $maxy );
    my $r = { 
        bbox => [ $minx, $miny, $maxx, $maxy ],
        p1 => [ $minx, $miny ],
        p2 => [ $maxx, $maxy ],
        left => $minx, top => $miny, right => $maxx, bottom => $maxy,
        id => $g->getElementID,
        width =>  $w,
        height => $h,
    };
    return $r;
}
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