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

Tk gurus:

I want to have a text widget where I can display a running log from a process. Example code below. This all works fine except if the x-axis scroll bar is at it's maximum right hand position relative to the text widget and more text is printed to the widget the x-axis scrollbar moves to it's most left hand position. I want the scrollbar to stay at it's current postion.

This is my first attempt at using Tk.... I can't figure out how to control this - or if's it's controllable. Maybe there is a better method. All suggestions are most welome.

Thanks! 

use strict;
use Tk;

my ($mainwindow, $menubar, $display, $text);

my $counter = 0;

$mainwindow = new MainWindow;
$mainwindow->geometry("800x400");

$display = $mainwindow->Scrolled('Text', -relief=>'sunken',
-borderwidth=>'2',
  -height=>'24', -scrollbars=>'se', '-width' => 40, '-wrap'=>'none');
$display->pack(-expand=>'1', -fill=>'both');

$text =  $display->Subwidget('text');           # need this because yo
+u
can't tie to $display - main widget
tie *STDOUT, ref $text, $text;

create_gui_main();

$text->repeat(
  1000, sub {
    goto \&mymain;
  },
);

MainLoop;

sub mymain() {
  # This would normally be real text
  $counter++;
  print "this is a very long line we need a scrollbar on the x
axis........ this is a very long line we need a scrollbar on the x
axis........ this is a very long line we need a scrollbar on the x
axis........ well the number is current = " . $counter . " \n";
}

# ------------------------ #
sub quitapp() {
  exit;
}

# ------------------------ #
sub create_gui_main {
  my $menuitems = [
    [Cascade => "~File", -menuitems => [
        [Button => "~Quit", -command => \&quitapp],
      ]
    ],
  ];
  if ($Tk::VERSION >= 800) {
    $menubar = $mainwindow->Menu(-menuitems => $menuitems);
      $mainwindow->configure(-menu => $menubar);
  } else {
    $mainwindow->Menubutton(-text => "Pseudo menubar",
      -menuitems => $menuitems)->pack;
  }
}
__END__

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Replies are listed 'Best First'.
Re: Tk and scrollbars
by eserte (Deacon) on Jul 09, 2004 at 09:22 UTC
    You can remember the scrollbar position before printing to the widget and restore the position after printing. E.g: 
    sub mymain() {
  # This would normally be real text
  my(@old_x_view) = $text->xview;
  $counter++;
  print "this is a very long line we need a scrollbar on the x axis...
+..... this is a very long line we need a scrollbar on the x axis.....
+... this is a very long line we need a scrollbar on the x axis.......
+. well the number is current = " . $counter . " \n";
  $text->xview(moveto => $old_x_view[0]);
}

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[d/l]
      Thank you - my(@old_x_view) = $text->xview; $text->xview(moveto => $old_x_view[0]); this works perfectly --jammin
[reply]
Re: Tk and scrollbars
by SciDude (Friar) on Jul 09, 2004 at 03:56 UTC

    Did you want the single quotes around '-wrap' and '-width' ?

    Also, your "very long line" had line breaks in my downloaded version. Here are my modest hacks to activate the horizontal scroll bar: 

    #!/usr/bin/perl

use strict;
use Tk;

my ($mainwindow, $menubar, $display, $text);

my $counter = 0;

$mainwindow = new MainWindow;
$mainwindow->geometry("800x400");

$display = $mainwindow->Scrolled('Text', -relief=>'sunken',
-borderwidth=>'2',
  -height=>'24', -scrollbars=>'se', '-width' => 40, -wrap=>'none');
$display->pack(-expand=>'1', -fill=>'both');

$text =  $display->Subwidget('text', -scrollbars=>'se', -wrap=>'none')
+;           # need this because you can't tie to $display - main widg
+et
tie *STDOUT, ref $text, $text;

create_gui_main();

$text->repeat(
  1000, sub {
    goto \&mymain;
  },
);

MainLoop;

sub mymain() {
  # This would normally be real text
  $counter++;
  print "this is a very long line we need a scrollbar on the x axis...
+..... this is a very long line we need a scrollbar on the x axis.....
+... this is a very long line we need a scrollbar on the x axis.......
+. well the number is current = " . $counter . " \n";
}

# ------------------------ #
sub quitapp() {
  exit;
}

# ------------------------ #
sub create_gui_main {
  my $menuitems = [
    [Cascade => "~File", -menuitems => [
        [Button => "~Quit", -command => \&quitapp],
      ]
    ],
  ];
  if ($Tk::VERSION >= 800) {
    $menubar = $mainwindow->Menu(-menuitems => $menuitems);
      $mainwindow->configure(-menu => $menubar);
  } else {
    $mainwindow->Menubutton(-text => "Pseudo menubar",
      -menuitems => $menuitems)->pack;
  }
}
__END__

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    SciDude
    The first dog barks... all other dogs bark at the first dog.
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[d/l]

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