11.7. How do I get a Canvas to output PostScript(c)? 
 
 Many thanks to Tom Oelke <tpo9617@rit.edu> for providing this questio
+n,
 answer & snippet of code: 
 
  The following section of code gets the postscript code for the secti
+on of
  canvas that's top-left corner is at $min_x, $min_y, and has a width 
+and
  height equivalent to the displayed region. This ps code is then pipe
+d out
  to lpr to be printed. 
 
     my $ps = $canvas->postscript( '-x' => $min_x,
                                   '-y' => $min_y,
                                   -width => $canv->Width,
                                  -height => $canv->Height);
     open (PS, "| lpr"); # customize with -Pname e.g. 
     print PS $ps;
     close (PS);
 
 Whereas you would use something like: 
 
     open (PS, ">file.ps"); # to output to a file
     print PS $ps;
     close (PS);
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% lpr file.ps
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but! that doesnt do anything does it ? just prints it to the screen, or to a file. It doesnt print it (hard copy) whatsoever! Maybe i have misunderstood?

sub area_save {

    my($w, $pinfo) = @_;

    my($x1, $x2, $y1, $y2, $a);

    if($pinfo->{'areaX2'} != -1) {
    ($x1, $x2, $y1, $y2) =
      @$pinfo{'areaX1', 'areaX2', 'areaY1', 'areaY2'}; # slice !
    ($x1, $x2) = @$pinfo{'areaX2', 'areaX1'} if $x2 <= $x1;
    ($y1, $y2) = @$pinfo{'areaY2', 'areaY1'} if $y2 <= $y1;
    $a = $w->postscript('-x' => $x1, '-y' => $y1,
                -width => $x2 - $x1, -height => $y2 - $y1);
    } else {
    $a = $w->postscript;
    }

    $SIG{'PIPE'} = sub {};
    open(LPR, "| $pinfo->{'prcmd'}");
    print LPR $a;
    close(LPR);

} # end area_save
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i hate to keep asking questions, but :P

1) what are the 2 arguments passed to it ?
my($w, $pinfo) = @_;
i.e. which is the canvas, and what is the other thing ?

2) This appears to use PIPE's ? im using windowsXP, I though pelr couyldnt use pipes outside of linux. Or is that just for the Printer module ?

Thanks again :)

If you're on Windows, you could check out Tk::WinPrint. Though I'm in the search for a maintainer for this module :-)

So rather than try to explain to you, what you can find yourself, I will give a "more straight-forward" example.

Like in kvale's first reply, you need to specify the "boundaries" of what you want to capture as postscript. That is what the $pinfo is for. So look at this simple example.

#!/usr/bin/perl
use Tk;
#to change the background color, edit the ps file 
#  0.000 0.000 0.000 setrgbcolor AdjustColor 
#  fill 

$width = 800;
$height = 500;
my $main = MainWindow->new();
my $canvas = $main->Canvas( -width=>$width, -height=>$height, -backgro
+und=>"black");
$canvas->pack( -expand=>1,-fill=>'both');

&create;

$canvas->update;
$main->update;

$main->Button(
    -text    => "Save",
    -command => [sub {
         $canvas->update;
         my @capture=();
         my ($x0,$y0,$x1,$y1)=$canvas->bbox('all');
         @capture=('-x'=>$x0,'-y'=>$y0,-height=>$y1-$y0,-width=>$x1-$x
+0);
         $canvas -> postscript(-colormode=>'color',
                               -file=>$0.'.ps',
                               -rotate=>0,
                               -width=>800,
                               -height=>500,
                               @capture);

                              }

  ]  )->pack;

MainLoop;

sub create{
$canvas->createOval(100, 100, 600, 600,-fill=>'green')

}
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wow, thanks for that :) i didnt know about that widget demo thing, its very useful :)

It all appears to work now, my canvas prints to postscript form, almost perfectly! the biggest thing which would go on it, is luckily in perfect proportions for an A4 sheet! The only problem i am still having is with the lpr command...

lpr -S localhost or 127.0.0.1 -P LPT1 FILENAME

which its having problems with (Error: print server unreachable or specified printer does not exist.). Howevetr im sure its only a matter of time before i work this out! And the fact it is getting this far anyway means that it is likely to work once it finds te correct place! :)

Thanks alot!

The reason You're having problems with:

lpr -S localhost or 127.0.0.1 -P LPT1 FILENAME
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Is that under WinXP (which you mention running), you need to enable lpr support under "services". Please note that lpr support is only available under XP-Pro, NOT under XP-Home.

And even then it's kludgy and hard to administer. It's easier to just dump into a file and spawn (Win32::CreateProcess()) something to do the dirty work of sending it to the printer, like maybe, ghostscript.

---

madams55075@comcast.net