cniggeler has asked for the wisdom of the Perl Monks concerning the following question:

Hi, I'd like to use the -font option in a Tk Label if the font's been externally defined by the user. I'd also like to condense my lines of code by combining options I'm repeating. So I'd like something like this: 
my $newfont = '';
# maybe font value read from user, results in
# $newfont = "{liberation sans} 8 normal";
my $opt = "-fg => $fg, -bg => $bg";
$opt .= ", -font => $newfont" if length($newfont);
$rw->Label(-text => "Col. 1", $opt, -padx => 10)->grid(
   $rw->Label(-text => "Col. 2", $opt, -padx => 11),
   $rw->Label(-text => "Col. 3", $opt, -padx => 11))

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but I get this error message: 
Tk::Error: Odd number of args to Tk::Label->new(...)

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Nothing I could think of, including escaped quotes or eval(), has gotten around it, so for now I use an if-else that checks length($newfont) and repeats the Label widget creation, once with and once without -font.

Is this possible? I lack detailed perl knowledge, so probably something like \$${opt} would do the trick :-) Thanks!

Replies are listed 'Best First'.
Re: tk option+value in variable?
by choroba (Cardinal) on Jan 25, 2019 at 20:51 UTC
    No advanced referencing is needed, just use an array of options instead of a string: 
        my @opt = (-fg => $fg, -bg => $bg);
    push @opt, -font => $newfont if length $newfont;
    $mw->Label(-text => "Col. 1", @opt, -padx => 10)->grid(
        $mw->Label(-text => "Col. 2", @opt, -padx => 11),
        $mw->Label(-text => "Col. 3", @opt, -padx => 11));

    [download]
    map{substr$_->[0],$_->[1]||0,1}[\*||{},3],[[]],[ref qr-1,-,-1],[{}],[sub{}^*ARGV,3]
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[d/l]
[select]
      Bingo! Thanks so much!
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        Maybe this should be a nother top-level question, but can you tell me know you knew to promote my string to an array? I was playing with subroutines and arguments, and I found that all these generated the same answer (5):

        my $a = 2; 
my $b = 3;
print &add($a, $b) . "\n";

my $opt = "$a, $b";
print &add(eval($opt)) . "\n";

my @opt = ($a, $b);
print &add(@opt) . "\n";

exit;

sub add {
   my ($x, $y) = @_;
   return ($x +$y);
}

        [download]
        Another area my knowledge is lacking is the dash notation for the options (-font => 'courier', for example); is that common in other areas of perl or specific to Tk?
[reply]
[d/l]

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