How to move up/down the row element in a ListBox/Mlistbox

[ghosh123]

Hi Monks, I need one push in regard to move a row element up and down by clicking a button or pressing Up/Down key. Let us consider this small code below ================================================

my $mw = MainWindow -> new();

my $lb = $mw -> Scrolled("Listbox",

    -scrollbars=>'e' ,
    
) -> pack(

    -side => 'left' ,
    -fill => 'y'
);

foreach my $key ("first" , "second" , "third", "fourth") {
    
    $lb -> insert( 'end', $key );

}

    $lb->activate ( 0 ) ;
    $lb->selectionSet ( 0 ) ;
    $lb->focus;

$lb -> bind ('<Key-Down>', sub {print "Down\n"} );

$mw -> bind ('<Key-Up>', sub {print "\nUP"} );

MainLoop;

================================================== Now the items appear as "first", "second" ,"third" and "fourth" in row1 row2,row3 and row4 respectively. My requirement is to alter the order of appearence by clicking or pressing up/down key. For example after the order would appear as "second" "first" "fouth" and "third". Kindly help . Thanks in advance. -AG

[GrandFather]

Binding to the up and down arrow keys is somewhat problematic because they are already used for list box navigation. However using 'x' and 'e' for the down and up keys you can reorder the list as follows:

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

my $mw = MainWindow->new();

my $lb = $mw->Scrolled("Listbox", -scrollbars => 'e',)->pack(
    -side => 'left',
    -fill => 'y'
);

for my $key ("first", "second", "third", "fourth") {
    $lb->insert('end', $key);
}

$lb->activate(0);
$lb->selectionSet(0);
$lb->focus();

$lb->bind('<x>', sub {down($lb, @_)});
$mw->bind('<e>', sub {up($lb, @_)});

MainLoop;


sub down {
    my ($lb) = @_;
    my @selItems = $lb->curselection();

    return if 1 != @selItems || $selItems[0] == $lb->size();

    my $item = $lb->get($selItems[0]);

    $lb->delete($selItems[0]);
    $lb->insert($selItems[0] + 1, $item);
    $lb->selectionSet($selItems[0] + 1);
}


sub up {
    my ($lb) = @_;
    my @selItems = $lb->curselection();

    return if 1 != @selItems || $selItems[0] == 1;

    my $item = $lb->get($selItems[0]);

    $lb->delete($selItems[0]);
    $lb->insert($selItems[0] - 1, $item);
    $lb->selectionSet($selItems[0] - 1);
}

[chessgui]

Something like (untested):

$UP=-1;
$DOWN=1;

sub move
{
my $lb=shift;
my $direction=shift;
my $cur=$lb->curselection();
$cur+=$direction;
my $size=$lb->size();
$cur=0 if $cur>=$size;
$cur=$size-1 if $cur<0;
$lb->see($cur);
}

usage: move($lb,$UP); move($lb,$DOWN); (only works if one and only one element is selected)

[thundergnat]

If you are doing it in a GUI, why not do it with the GUI? Drag and drop, baby!

#!/usr/bin/perl
use warnings;
use strict;
use Tk;
use Tk::DragDrop;
use Tk::DropSite;

my %tk;

my $font = '{Helvetica} 14';

$tk{mw} = MainWindow->new;

$tk{lbframe} = $tk{mw}->Frame->pack(
    -expand => 1,
    -fill   => 'both',
    -anchor => 'nw'
);

$tk{listbox} = $tk{lbframe}->Scrolled(
    'Listbox',
    -selectmode => 'single',
    -scrollbars => 'ose',
    -font       => $font,
  )->pack(
    -expand => 1,
    -fill   => 'both',
    -padx   => 5,
    -pady   => 5,
  );

$tk{listbox}->insert( 'end', $_) for qw/first second third fourth fift
+h etc./; 

my $dnd_token = $tk{listbox}->DragDrop(
    -event        => '<B1-Motion>',
    -sitetypes    => [qw/Local/],
    -startcommand => \&DragStart,
);

$tk{listbox}->DropSite(
    -droptypes   => [qw/Local/],
    -dropcommand => [ \&Drop, $tk{listbox}, $dnd_token ],
);

MainLoop;

sub DragStart {
    my ($token) = @_;
    my $site    = $token->parent;
    my $e       = $site->XEvent;
    my $idx     = $site->index( '@' . $e->x . ',' . $e->y );
    if ( defined $idx ) {
        $token->configure( -text => $site->get($idx), -font => $font )
+;
        $site->delete($idx);
        my ( $X, $Y ) = ( $e->X, $e->Y );
        $token->MoveToplevelWindow( $X, $Y );
        $token->raise;
        $token->deiconify;
        $token->FindSite( $X, $Y, $e );
    }
}

sub Drop {
    my ( $site, $token ) = @_;
    my $text    = $token->cget('-text');
    my $y       = $site->pointery - $site->rooty;
    my $nearest = $site->nearest($y);
    if ( defined $nearest ) {
        my @xy = $site->bbox($nearest);
        if ( $xy[1] + $xy[3] > $y ) {
            $site->insert( $nearest, $text );
        }
        else {
            $site->insert( 'end', $text );
        }
    }
}

[gllore]

Dear Perl gurus, This is my first time asking a question with regard to the use of Drag and Drop in the previous example. (( #3333=superdoc: print w/replies, xml )) When I implement the above code for a ListBox and I drag the name of the item outside the Listbox and I accidently let go of the mouse, the following happens: (1) the text that I am dragging disappears and (2) the text corresponding to the dragged item does not return to the Listbox. Is there a way you could recommend to force the item to return in the listbox when this happens? REGARDS gllore

[gllore]

Since my last question, I have actually taken advantage of the accidental disappearance of the dragged item. I use the disappearance to represent a deletion of the item --- a "swoosh" and delete of the pointer. I now keep track of whether the user has exited the ListBox and deleted the item (accidentally or by mistake) by keeping count of how many times the user enters and leaves the Listbox --- not too elegant but it works. Is there a simpler alternative? I already have an explicit "Delete" button for the first-time user who is yet unfamiliar with the behavior of the GUI. Best, Juan