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Undesired space between Tk Canvases

by liverpole (Monsignor)
on Apr 25, 2007 at 00:10 UTC ( #611882=perlquestion: print w/replies, xml ) Need Help??

liverpole has asked for the wisdom of the Perl Monks concerning the following question:

I'm sure I'm missing something obvious here.

Within my Perl/Tk application, I'd like to have a 256x256 white Canvas in the center of 4 other Canvas objects (of different colors here, while debugging).

I've tried every option I can think of, searched for a possible solution, and perused the most recent volume of "Mastering Perl/Tk" -- all to no avail.

Here is a stripped down version of my original program which still shows the problem.  When you run it, you get a white Canvas in the middle of 4 Canvas "strips" of other colors.  I'd like the Canvas objects to all be flush with one another, but there's a little space between each of them.

I know this has to be something simple and easy, but I'm just not seeing it.  It's not the enclosing Frame (at least I don't think it is), because the Frame has a blue background, and there isn't any blue showing through anywhere.

Can someone point me to a solution?  Thanks!

#!/usr/bin/perl -w # Strict use strict; use warnings; # Libraries use Tk; # Main program create_gui(); # Subroutines sub create_gui { my $mw = new MainWindow(-title => 'Type "Escape" to exit...'); $mw->bind('<Escape>' => sub { $mw->destroy() }); my $frame = $mw->Frame(-background => 'blue'); $frame->pack(-expand => 0, -fill => 'both'); # Note: 288 = 256 + 16 + 16 canvas($frame, 'hotpink', 'left', 16, 256 + 16 + 16); canvas($frame, 'gold', 'right', 16, 256 + 16 + 16); canvas($frame, 'maroon', 'top', 256, 16); canvas($frame, 'white', 'top', 256, 256); canvas($frame, 'purple', 'bottom', 256, 16); MainLoop; } sub canvas { my ($w, $background, $side, $width, $height) = @_; my $canvas = $w->Canvas(-background => $background); $canvas->configure(-width => $width); $canvas->configure(-height => $height); $canvas->pack(-expand => 1, -fill => 'both', -side => $side); return $canvas; } # # Key: H = Hotpink, M = Maroon, P = Purple, G = Gold, . = White # # The GUI I'm actually getting: The GUI I'd *LIKE* to get: # # +------------------------------+ +------------------------------+ # |Tk Type "Escape" to exit..." | |Tk Type "Escape" to exit..." | # +------------------------------+ +------------------------------+ # |H MMMMMMMMMMMMMMMMMMMMMMMM G| |HMMMMMMMMMMMMMMMMMMMMMMMMMMMMG| # |H G| |H............................G| # |H ........................ G| |H............................G| # |H ........................ G| |H............................G| # |H ........................ G| |H............................G| # |H ........................ G| |H............................G| # |H ........................ G| |H............................G| # |H ........................ G| |H............................G| # |H ........................ G| |H............................G| # |H ........................ G| |H............................G| # |H G| |H............................G| # |H PPPPPPPPPPPPPPPPPPPPPPPP G| |HPPPPPPPPPPPPPPPPPPPPPPPPPPPPG| # +------------------------------+ +------------------------------+ #

Update:  After Super-Searching some more, I came across this node, by the venerable zentara.  He used a Canvas option I hadn't tried:  -highlightthickness => 0.

Although I'm still not exactly sure what highlightthickness is used for, it does the trick; inserting the following line completely addresses my problem:

$canvas->configure(-highlightthickness => 0);

Thanks, zentara -- you help me even when you're not logged in!


s''(q.S:$/9=(T1';s;(..)(..);$..=substr+crypt($1,$2),2,3;eg;print$..$/

Replies are listed 'Best First'.
Re: Undesired space between Tk Canvases
by shmem (Chancellor) on Apr 25, 2007 at 04:44 UTC
    Press <Tab> in that Tk window. See? You want
    $canvas->configure(-highlightthickness =>0);

    :-)

    update: I see you found out while I was writing the answer... highlightthickness is the width of the highlight border (default 1 pixel). If you set it to 0, the element will not highlight while cycling through the elements with <Tab>, since there is nothing to colour. If you want to leave the border there, use

    $canvas->configure(-highlightbackground => $background);

    --shmem

    _($_=" "x(1<<5)."?\n".q·/)Oo.  G°\        /
                                  /\_¯/(q    /
    ----------------------------  \__(m.====·.(_("always off the crowd"))."·
    ");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}
      ++shmem, and thanks,

      Your example illustrates the meaning of highlightthickness quite nicely.  Typing <Tab> several times makes it very clear why you might want to have a space there (I don't of course, because I'm only using the border Canvases to frame the inner one, and thus don't need to select them).

      Similarly, just as I had never used highlightthickness before, highlightbackground was also new to me.  So that's 2 new things you've taught me in Tk -- thank you!


      s''(q.S:$/9=(T1';s;(..)(..);$..=substr+crypt($1,$2),2,3;eg;print$..$/

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