Greetings BrowserUk!

I just recently came across the infamous Canvas bind problem again.

According to Mastering Perl/Tk (published by O'Reilly), you need to use a different bind method with a Canvas object, called CanvasBind.  (This is described in chapter 9.4, and it's because a Canvas object has its own bind method).

Here's an example program I created to demonstrate.  When you resize the main window (and thus the Canvas object), it draws random squares as a result of the change in size and/or position (the event for which is a "<Configure>"): 

#!/usr/bin/perl -w
                                                                      
+          
# Strict
use strict;
use warnings;
                                                                      
+          
# Libraries
use Tk;
                                                                      
+          
# Subroutines
sub random($) { int rand $_[0] }

sub random_square($) {
    my $can = shift;
    my ($x0, $y0, $x1, $y1) = (random 256, random 256, random 256, ran
+dom 256);
    $x1 += $x0; $y1 += $y0;
    my $bg = sprintf "#%02x%02x%02x", random 256, random 256, random 2
+56;
    $can->createRectangle($x0, $y0, $x1, $y1, -fill => $bg);
}

# Main program
my $mw = new MainWindow(-title => "Canvas binding test");
my $can = $mw->Canvas(-bg => 'white', -width => 512, -height => 512);
$can->pack(-expand => 1, -fill => 'both');
$can->CanvasBind('<Configure>', [\&random_square]);
MainLoop;

[download]
@ARGV=split//,"/:L"; map{print substr crypt($_,ord pop),2,3}qw"PerlyouC READPIPE provides"

In reply to Re^3: Tk how-to? by liverpole
in thread Tk how-to? by BrowserUk

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