in reply to TK Canvas: Group vs. tags

As an example of the usefulness of using groups in motion operations, show me how you would do this with just 'tags'. 
#!/usr/bin/perl
use warnings;
use strict;
use Tk;

my $mw = MainWindow->new();

# first create a canvas widget 
my $canvas = $mw->Canvas(width => 300, height => 200)->pack();
my $one = $canvas->createOval(5,  0, 20, 30, -fill => 'blue');
my $two = $canvas->createRectangle(0, 20, 50, 75, -fill => 'red');

my $group = $canvas->createGroup([0, 0], -members => [$one, $two]);

my $dx = 1;
my $dy = 1;
my $id = Tk::After->new($canvas,10,'repeat',
             sub {$canvas->move($group, $dx,$dy);
                 my ($x,$y) = $canvas->bbox($group);
                 print "$x $y\n";
                 if($y >= 100){$dy = -1};
                 if($x >= 200){$dy = 1; $dx = -1};
                 if($x < -5){$dx=1;$dy=1};
          });

my $ebutton = $mw->Button(-text => 'Exit',
                  -command => 'Tk::exit')->pack();

my $sbutton = $mw->Button(-text => 'Stop',
                  -command => sub{$id->cancel;})->pack();


MainLoop();

[download]
I'm not really a human, but I play one on earth. flash japh

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Re: Re: TK Canvas: Group vs. tags
by dreadpiratepeter (Priest) on Mar 26, 2004 at 19:03 UTC
    Like this: 
    #!/usr/bin/perl
use warnings;
use strict;
use Tk;

my $mw = MainWindow->new();

# first create a canvas widget 
my $canvas = $mw->Canvas(width => 300, height => 200)->pack();
my $one = $canvas->createOval(5,  0, 20, 30, -fill => 'blue',-tags => 
+['fred']);
my $two = $canvas->createRectangle(0, 20, 50, 75, -fill => 'red',-tags
+ => ['fred']);

#my $group = $canvas->createGroup([0, 0], -members => [$one, $two]);
my $group='fred';
my $dx = 1;
my $dy = 1;
my $id = Tk::After->new($canvas,10,'repeat',
             sub {$canvas->move($group, $dx,$dy);
                 my ($x,$y) = $canvas->bbox($group);
                 print "$x $y\n";
                 if($y >= 100){$dy = -1};
                 if($x >= 200){$dy = 1; $dx = -1};
                 if($x < -5){$dx=1;$dy=1};
          });

my $ebutton = $mw->Button(-text => 'Exit',
                  -command => 'Tk::exit')->pack();

my $sbutton = $mw->Button(-text => 'Stop',
                  -command => sub{$id->cancel;})->pack();


MainLoop();

    [download]
    Update: Actually I can see the usefulness for rotation. But for motion, and state-changes and such the two methods appear the same.


    -pete
    "Worry is like a rocking chair. It gives you something to do, but it doesn't get you anywhere."
[reply]
[d/l]
      Well, I'm out of XP today, but I would give you one for that. :-)
      I'm not really a human, but I play one on earth. flash japh
[reply]

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