Re: How to destroy and re-create bound widgets

[zentara]

I ran your code, and saw one problem immediately.

#Here are some fake buttons using sub-canvas:
my $scan1 = $rightframe-> Canvas(-width => 64, -height => 54, -highlig
+htthickness => 0);
my $scan2 = $rightframe-> Canvas(-width => 64, -height => 54, -highlig
+htthickness => 0);
my $scan3 = $rightframe-> Canvas(-width => 64, -height => 54, -highlig
+htthickness => 0);

&scan1start;

MainLoop;

sub reset {
        my @buttons = ($scan1,$scan2,$scan3);
        foreach (@buttons) { $_-> destroy; }
        #&scan1start;
}

sub scan1start {
        if ($numscan1 == 0) {
                $scan1-> form(-left => '187', -top => '319');
                $scan1-> configure(-background => 'black');
                $scan1-> Tk::bind('<Button-1>' => sub {
.... etc 
.... etc
.... etc
}

You define $scan1, $scan2, $scan3 globally, then destroy them in your reset sub. Then without recreating them, you try to access them in &scan1start.

Although it dosn't address all your issues, you might start by tring something like this:

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

my $mw = new MainWindow;
$mw-> geometry('640x480');
$mw-> resizable( 0, 0 );

my $numscan1 = 0;
my $numscan2 = 0;
my $numscan3 = 0;

my $leftframe = $mw-> Frame();
$leftframe->form(-left => '%0', -right => '%25', -bottom => '%99', -to
+p => '%1');
my $resetb = $leftframe-> Button(-text => 'Reset', -command => \&reset
+ )->form(-left => '%50', -top => '%50');

my $rightframe = $mw-> Frame(-relief => 'groove', -borderwidth => 1);
$rightframe-> form(-left => $leftframe, -right => '%99', -bottom => '%
+99', -top => '%1');

my $maincanvas = $rightframe-> Canvas(-background => 'blue', -highligh
+tthickness => 0);
$maincanvas-> form(-left => '%1', -right => '%99', -bottom => '%99', -
+top => '%1');

#Here are some fake buttons using sub-canvas:
#my $scan1 = $rightframe-> Canvas(-width => 64, -height => 54, -highli
+ghtthickness => 0);
#my $scan2 = $rightframe-> Canvas(-width => 64, -height => 54, -highli
+ghtthickness => 0);
#my $scan3 = $rightframe-> Canvas(-width => 64, -height => 54, -highli
+ghtthickness => 0);

my $scan1;
my $scan2;
my $scan3;

&scan1start;

MainLoop;

sub reset {
    my @buttons = ($scan1,$scan2,$scan3);
    foreach (@buttons) { $_-> destroy; }
    &scan1start;
}

sub scan1start {

 $scan1 = $rightframe-> Canvas(-width => 64, -height => 54, -highlight
+thickness => 0);
 $scan2 = $rightframe-> Canvas(-width => 64, -height => 54, -highlight
+thickness => 0);
 $scan3 = $rightframe-> Canvas(-width => 64, -height => 54, -highlight
+thickness => 0);

    
    if ($numscan1 == 0) {
        $scan1-> form(-left => '187', -top => '319');
        $scan1-> configure(-background => 'black');
        $scan1-> Tk::bind('<Button-1>' => sub {
            $numscan1 = 1;
            &scan2start; &scan3start; &scan1start;
        } );
        $scan1-> Tk::bind('<Button-3>' => sub { });
    }
    elsif ($numscan1 == 1) {
        $scan1-> form(-left => '187', -top => '319');
        $scan1-> configure(-background => 'white');
        $scan1-> Tk::bind('<Button-3>' => sub {
            if (($numscan2 == 0) && ($numscan3 == 0)) {
                $scan2->formForget;
                $scan3->formForget;
                $numscan1 = 0;
                &scan1start;
            } 
        } );
        $scan1-> Tk::bind('<Button-1>' => sub { });
    }
}

sub scan2start {
    if ($numscan2 == 0) {
        $scan2-> form(-left => '102', -top => '211');
        $scan2-> configure(-background => 'black');
        $scan2-> Tk::bind('<Button-1>' => sub {
            $numscan2 = 1;
            &scan2start;
        } );
        $scan2-> Tk::bind('<Button-3>' => sub { });
    }
    elsif ($numscan2 == 1) {
        $scan2-> form(-left => '102', -top => '211');
        $scan2-> configure(-background => 'white');
        $scan2-> Tk::bind('<Button-3>' => sub {
            $numscan2 = 0;
            &scan2start;
        } );
        $scan2-> Tk::bind('<Button-1>' => sub { });
    }
}

sub scan3start {
    if ($numscan3 == 0) {
        $scan3-> form(-left => '202', -top => '211');
        $scan3-> configure(-background => 'black');
        $scan3-> Tk::bind('<Button-1>' => sub {
            $numscan3 = 1;
            &scan3start;
        } );
        $scan3-> Tk::bind('<Button-3>' => sub { });
    }
    elsif ($numscan3 == 1) {
        $scan3-> form(-left => '202', -top => '211');
        $scan3-> configure(-background => 'white');
        $scan3-> Tk::bind('<Button-3>' => sub {
            $numscan3 = 0;
            &scan3start;
        } );
        $scan3-> Tk::bind('<Button-1>' => sub { });
    }
}

P. S. I also notice that you have recursive subroutine called in scan1start(). The way I set it up in the example, or in any Tk script, a recursive widget-creating sub is bound to cause havoc. By the way, why are you not using the createWindow method to embed those sub canvases?

[Phinix]

I did try createWindow... I'm still learning so I've been just experimenting and doing research trying to get the syntax right. Perhaps though you could explain why doing this:

my $canvaswindow = $canvas->createWindow(0,0, -window => $widget);

$canvaswindow->Tk::bind('<Button-1>' => sub { &dostuff0 });

...gives me an error saying: "Global symbol "$canvaswindow" requires explicit package name at line 3."

I have created $widget before attempting this, of various types. Is it not possible to create custom event binds on canvas objects? If so, that is why I do not use createWindow. If it is possible I would love to know how.

EDIT: I was able to get things working after I realized that the createWindow method isn't so much creating a new object that gets a reference but rather more like saying "put me here" to a previously created object template.

So, the above instead becomes:

$canvas->createWindow(0,0, -window => $widget);

$widget->Tk::bind('<Button-1>' => sub { &dostuff0 });

I'll post a full working example in a bit once I finish the translation. Thanks for all the helpful pointers and syntax examples though!

[zentara]

It sounds like you, as a beginner, my want to reconsider your design. The first thing I have to say, is why do you need the overlapping secondary sub-canvases? If you can make something on your sub-canvas, you can do the same thing on the underlying canvas. You can still put a background image on the main canvas, then instead of overlaying other canvases, why not create rectangular regions on the base canvas? In any event, look at this example:

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

my $mw = new MainWindow;

my $main = $mw -> Scrolled("Canvas",-scrollbars=>'e')-> 
          pack(-side =>'left', -fill => 'both', -expand => 1);

my $canvas = $main->Subwidget("canvas");

Tk::bind($canvas, '<MouseWheel>', [ sub {$canvas->yview('scroll',
    -($_[1] / 120) * 3,'units')}, Ev('D')]); 

my $see = "\nHaaa, See that and scroll!";

my $info = $main->createText(180, 15, -text => "$see", 
                    -font => 'Arial 11 bold' , -fill => 'red');

$main->configure(-scrollregion => [0,0,2000 , 2000]);

my $canvas_cube = $main->Canvas(-width => 45, -height => 45, 
                                          -background => 'green');

my $canvasWindow = $main->createWindow(75,75, -window => $canvas_cube)
+;

Tk::bind( $canvas_cube,  '<Enter>' => sub { print "Enter\n"; });
Tk::bind( $canvas_cube,  '<Leave>' => sub { print "Leave\n"; });

Tk::bind( $canvas_cube,  '<Button-1>' => sub { print "1\n"; });

$canvas->focus;

MainLoop;

[zentara]

Also see embedding xterm into a Tk app. If you are determined to use embeded Canvases, you could use this technique, to hide show them. Tk is somwhat limited and you need to cover the createWindow with another properly colored rectangle.

Tk::Zinc can actually hide or show the window. See the second example in Re: Window with background image and transparent listbox . You could put a second Zinc canvas in there, instead of an xterm.