Problem1.
I have a yellow rectangle on scrolled canvas...
#!/usr/bin/perl -w

use Tk;
use strict;

# Main program / GUI setup
my $mw = MainWindow->new;
my $c = $mw->Scrolled('Canvas', -width => 200, -height => 200)->grid;
$c->configure(-background =>'blue', -scrollregion => [ 0, 0, 500, 500 
+]);

#Grid
$c->createGrid(0, 0, 10, 10);
$c->createGrid(0, 0, 100, 100, -lines => 1, -dash => '.-');

$c->pack(-expand => 1, -fill => 'both');

my $rect = $c->createRectangle(20, 20, 40, 40, 
    -outline => 'yellow', 
    -fill => 'yellow');

MainLoop;

[download]
..which is the best way to make the rectangle float in the same place regardless of in which direction the canvas in scrolled?


Problem2.
Here are two rectangles red and green on a scrolled canvas... 
#!/usr/bin/perl -w             
use Tk;
use strict;  
                                                
my $mw = MainWindow->new;

$mw->geometry('300x300'); #try this
 
my $c = $mw->Scrolled('Canvas',
-width => 200,
-height => 200,
-background =>'blue',
-scrollregion => [ 0, 0, 500, 500 ]
)->pack(-expand => -2, -fill => 'both');

$c->createRectangle(100, 100, 150, 150, -fill => 'red');
$c->createRectangle(100, 400, 150, 450, -fill => 'green');

my $plus = $c->Button( 
   -text    => '  +  ', 
       -command => sub {$c->scale("all", 125, 125, 2, 2); } );
   $plus->pack;      
   
my $minus = $c->Button( 
    -text    => '  .  ', 
    -command => sub {$c->scale("all", 125, 125, 0.5, 0.5); } );
   $minus->pack;  


MainLoop;

[download]
...when the canvas is zoomed by 2x by clicking the '+' button the canvas remains in the same size which means that the areas not fitting in the new zoom disapear outside the visible area. (For example it is not possible to scroll to the green rectangle when zooming once.)How is it possible to zoom in a way so that the areas over which it is possible to scroll are expanded to contain the areas that do not fit to the new larger zoom. Thank you very much for your advice.

In reply to Two questions regarding -tk-canvas by tamaguchi

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