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Re^5: Unbind canvas items and Forget

by zentara (Archbishop)
on Nov 03, 2012 at 09:05 UTC ( #1002089=note: print w/ replies, xml ) Need Help??


in reply to Re^4: Unbind canvas items and Forget
in thread Unbind canvas items and Forget

You are on the right track in your thinking, but the thing to remember is that Canvas items are NOT objects, and don't respond correctly to create/destroy ...... a Canvas is an object, but things you put into a canvas's surface are called Canvas Items. Items can be shown/hidden/deleted. Most times on a Canvas, if you wanted to reuse canvas items, you hide them, then reconfigure them in the background, then show them again. If you try to put another Canvas on top of another Canvas, it will probably not work as you expect, unless you put the other canvas into a createWindow of the underlying canvas.

#!/usr/bin/perl use warnings; use strict; use Tk; # the -stipple=>'transparent' option will still # allow the bindings to work, but you can see the overlap # See Chapter 17 of Mastering Perl/Tk my $mw = MainWindow->new(); # first create a canvas widget my $canvas = $mw->Canvas(width => 300, height => 200)->pack(); my $one = $canvas->createOval(55, 20, 200, 190, -fill => 'blue', -outline=>'blue', -tags => ['blue'], -stipple => 'transparent', ); my $two = $canvas->createOval(105, 20, 250, 190, -fill => 'red', -outline=>'red', -tags => ['red'], -stipple => 'transparent', ); my $ebutton = $mw->Button(-text => 'Exit', -command => 'Tk::exit')->pack(); my $cbutton = $mw->Button(-text => 'Clear', -command => sub{$canvas->delete('all')})->pack(); $canvas->Tk::bind("<Motion>", [ \&print_xy, Ev('x'), Ev('y') ]); MainLoop(); sub print_xy { my ($canv, $x, $y) = @_; # print "(x,y) = ", $canv->canvasx($x), ", ", $canv->canvasy($y), "\n +"; #trick to find overlapping objects, just use x1 = x and y1 = y #to get a rectangular region of 1 point my (@current) = $canvas->find('overlapping', $x, $y, $x, $y); foreach my $id(@current){ print $canvas->gettags($id),' '; } print "\n"; }

I'm not really a human, but I play one on earth.
Old Perl Programmer Haiku ................... flash japh


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