pretty_xml.pl

#!/usr/bin/perl
use strict;
use warnings;
use XML::LibXML;
use XML::LibXML::PrettyPrint;
use HTML::Entities;
use Syntax::Highlight::Engine::Kate::XML;

my $hl = Syntax::Highlight::Engine::Kate::XML->new(
    format_table => {
       Alert => ["<font color=\"#0000ff\">", "</font>"],
       BaseN => ["<font color=\"#007f00\">", "</font>"],
       BString => ["<font color=\"#c9a7ff\">", "</font>"],
       Char => ["<font color=\"#ff00ff\">", "</font>"],
       Comment => ["<font color=\"#7f7f7f\"><i>", "</i></font>"],
       DataType => ["<font color=\"#0000ff\">", "</font>"],
       DecVal => ["<font color=\"#00007f\">", "</font>"],
       Error => ["<font color=\"#ff0000\"><b><i>", "</i></b></font>"],
       Float => ["<font color=\"#00007f\">", "</font>"],
       Function => ["<font color=\"#007f00\">", "</font>"],
       IString => ["<font color=\"#ff0000\">", ""],
       Keyword => ["<font color=\"#00007f\">", "</font>"],
       Normal => ["<b>", "</b>"],
       Operator => ["<font color=\"#ffa500\">", "</font>"],
       Others => ["<font color=\"#b03060\">", "</font>"],
       RegionMarker => ["<font color=\"#96b9ff\"><i>", "</i></font>"],
       Reserved => ["<font color=\"#9b30ff\"><b>", "</b></font>"],
       String => ["<font color=\"#ff0000\">", "</font>"],
       Variable => ["<font color=\"#0000ff\"><b>", "</b></font>"],
       Warning => ["<font color=\"#0000ff\"><b><i>", "</b></i></font>"],
    },
);

my $str = join('', <STDIN>);
my $doc = XML::LibXML->load_xml( string => $str );
my $callback = sub {
    my $node = shift;
    my @nodes = $node->childNodes();
    scalar(@nodes) == 1 && ref($node->firstChild) eq 'XML::LibXML::Text'
};
my $pp = XML::LibXML::PrettyPrint->new(
    indent_string => "  ",
    element => {
        compact => [$callback],
    }
);
$pp->pretty_print($doc);
$str = $doc->toString;
$str =~ s/"\sxmlns:/"\"\n".(" " x 10)."xmlns:"/e while $str =~ /" xmlns:/;
my @lines = split "\n", $str;
my $pat = "";
for (@lines) {
    $pat = /^(.+?\s)xmlns/ && " " x length $1 if /\S\sxmlns/;
    /^\s+xmlns/ && s/^\s+/$pat/e;
}
$str = join "\n", @lines;
$str = $hl->highlightText($str);
$str =~ s{<(?!/?(font|b)\b)}{&lt;}g;

print $str