Isn't that a function of the OS, under linux Tk should check the LANG setting and then handle text based on those rules.
Windows should do the samething if you have the language pack installed and switch to a R to L language.
I only have us-eng installed on my linux box so I can't change languages to test.

It's a function several pieces of software: the font / font renderer and the toolkit the edit widget came from, and sadly the particular application. That's why there are often inconsistencies across systems and softwares. In Windows, the consistency issue at least is better, because one vendor is responsible for more things.

On your linux box where you "only have us-eng installed", you might in fact get BiDi anyway in certain cases (say, for example, in a browser). And to get it *everywhere*, you might have to work very hard.

#!/usr/bin/perl
use warnings;
use strict;

my $a1= "I sit here and think ?";
print "$a1\n";
my $b1 =  reverse $a1;
print "$b1\n";
[download]

let me assure you, that right-to-left writing are so in a quite fortunate way.

May be a bit unfortunate a fact that it is a bit more complicated to process in a simple hello-world program, but this is another question...

I suspect that the OP meant that it was unfortunate for him/her that Urdu is not written in the same direction that the Tk widget set works in, with no slight intended towards RTL languages.

And I'd also like to second the suggestion (below) to use a browser as the renderer. Search the monastery for links on using translation and Template::Toolkit together, and you're off to a good start.


--
Spring: Forces, Coiled Again!

#!/usr/bin/perl
# urdu.pl, written by Mike Foster
# feel free to reuse, modify, redistribute,
# bend, fold, staple, or mutilate.

use strict;
use warnings;
use Tk;

my $lastlength=1;
my $lastdepth=1;
my $mw = MainWindow->new(
    -background=>"darkviolet"
    );
$mw->title('Right-to-left text entry');

my $t1 = $mw->Text(
       -background=>"navy",
       -foreground=>"white",
       -height=>35,
       -width=>80,
       -wrap=>"word",
       -selectbackground=>"blueviolet"
       )->pack;
$t1->bind("<Key>" => \&rtl);

sub rtl {
    #gets end position
    my $depth = $t1->index('end');
    #reduces to line
    $depth =~ s/\..*$//;
    #converts back to an integer
    $depth--;
    if ($lastdepth < $depth) {
        $t1->SetCursor('insert - 1 lines lineend');
    }
    #remember where we were
    $lastdepth = $depth;
    
    #gets end of current line
    my $length = $t1->index('insert lineend');
    #reduces to character number
    $length =~ s/^.*\.//;
    #converts back to integer
    $length++;
    if ($lastlength < $length) {
        $t1->SetCursor('insert - 1 chars');
    }
    #remember where we were
    $lastlength = $length;
}

MainLoop;
[download]

Wolfger,

Thanks for the code. It is pretty much what I am looking for. I modified it to 1) have only 1 line of text (because they will copy/paste), 2) have a simple menu, and 3) use an Udru font.

davidj

#!/usr/bin/perl
use strict;
use warnings;
use Tk;

my $mw = MainWindow->new(
    -background=>"darkviolet"
    );


my $t1 = $mw->Text(
       -background=>"navy",
       -foreground=>"white",
       -height=>35,
       -width=>80,
       -wrap=>"word",
       -selectbackground=>"blueviolet"
       )->pack;
$t1->bind("<KeyRelease>" => sub {$t1->SetCursor('current - 1 chars')})
+;

MainLoop;
[download]

Okay, I got it working better, but it's still buggy. I fixed the bug that prevented cursor keys from working. Also, delete and backspace function normally now (without causing undue cursor movement), although backspace still goes left rather than right, and vice versa. The proper text direction is more reliable, but still committing errors. When I type "This is a test.", I invariably wind up with " .tseta si sihT". The cursor fails to move left on the space following the "a" every single time I type that sentence. If somebody can figure this out, I'd be grateful, as I am now quite interested in solving this problem.

#!/usr/bin/perl
use strict;
use warnings;
use Tk;

my $last=1.0;
my $mw = MainWindow->new(
    -background=>"darkviolet"
    );


my $t1 = $mw->Text(
       -background=>"navy",
       -foreground=>"white",
       -height=>35,
       -width=>80,
       -wrap=>"word",
       -selectbackground=>"blueviolet"
       )->pack;
$t1->bind("<Key>" => \&rtl);
#$t1->bind("<KeyRelease>" => sub {$t1->SetCursor('insert - 1 chars')})
+;

sub rtl {
    my $size = $t1->index('end - 1 chars');
    if ($last < $size) {
        $t1->SetCursor('insert - 1 chars');
    }
    $last = $size;
}

MainLoop;
[download]


edit: Got it! This error occurs on the 10th character of the line, and repeats at the 100th. Our comparison is saying that 1.9 is not less than 1.10 and 1.99 is not less than 1.100. True for integers, but not for line.word count.

--
Linux, sci-fi, and Nat Torkington, all at Penguicon 3.0

Obviously, there are ways of dealing with these issues; just bear in mind that it's more than just a simple matter of reversing the direction of text lines.

Hopefully, Gtk will have what you need (though I've never used it with perl, and am not sure about its merits or deficiencies for rendering Arabic script). Let me know if you get anywhere with that...