Re: flags object from strings

[muppet <scott asofyet org>]

On Apr 30, 2008, at 9:44 PM, Kevin Ryde wrote:

> Is there a way to make a Glib::Flags object, or rather a subclass like
> Gtk2::Gdk::EventMask, from an array of elements like ['a','b','c']?
> Which is to say, perl level access to gperl_convert_flags() basically.
>
> I know an array is converted automatically on input to various funcs,
> but I'd like to do some arithmetic setting and clearing elements, and
> thought to use the flags object overloads, as long as one of my  
> operands
> is an object.


Seems like a reasonable thing to want to do.  The big question is,  
what kind of syntax would you expect for this?  Here's one possible way:


#!/usr/bin/perl -w

use Glib qw(1.173); # the value field is relatively new
use Gtk2;

#
# pretend you didn't see this.  it takes advantage of knowledge of the  
internal
# representation of GFlags values in the bindings.
#
sub Glib::Flags::bless {
    my ($val, $type) = @_;

    my %valmap = (map { ($_->{name} => $_->{value}),
                        ($_->{nick} => $_->{value})
                  } Glib::Type->list_values ($type));

    my $num = 0;
    $num += $valmap{$_} foreach ('ARRAY' eq ref $val) ? @$val : $val;

    return bless \$num, $type;
}

# a plain-jane array of modifier enum value names
my $modifiers = [ qw(GDK_CONTROL_MASK shift-mask) ];

# give if the Glib::Flags magic
$modifiers = Glib::Flags::bless $modifiers, 'Gtk2::Gdk::ModifierType';

# Now the Glib::Flags operator overloads work.
print "$modifiers\n";
if ($modifiers >= 'control-mask') {
        print "yay, we're evil!\n";
}

__END__


Of course, it would be much more efficient if implemented as a line or  
two of XS code...



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