I'm using an old module from CPAN called WinConsole. It is a simple windowing utility for terminals. It works pretty good for me until recently. I decided to profile my application and I discovered that this sub takes up about 1/3 of the processing time. I suspect the substrs at the bottom of the innermost loop to be the problem, but I'm not even 100% sure what that line is doing.

Any suggestions for improvements

I have reformatted the code for clarity, but not changed it's functionality. 

#
# makeFullBackBuffer
#
# return a fullscreen attribute and a fullscreen text backbuffers usin
+g all the miniwins' backbuffer content.
sub makeFullBackBuffer
{
   my ($self) = @_;
   my (@backAtt, @backTxt, $screen, $current, $destCol, $destRow, $act
+ive);

   $screen = $self->{'miniwin'}[0];
   for (1..$screen->{'height'})
      {
      push @backTxt, ' ' x $screen->{'width'};
      push @backAtt, [(0) x $screen->{'width'}];
      }

   for $active (reverse @{$self->{'winStack'}})
      {
      $current=$self->{'miniwin'}[$active];
      for my $row (1..$current->{'height'})
         {
         for my $col (1..$current->{'width'})
            {
            $destCol = $current->{'colTop'} + $col - 2;

            if ($destCol > $screen->{'width'})
               {
               $destCol = $screen->{'width'};
               }

            $destRow = $current->{'rowTop'} + $row - 2;

            if ($destRow>$screen->{'height'})
                  {
                  $destRow = $screen->{'height'};
                  }

            $backAtt[$destRow][$destCol] = $current->{'backAtt'}[$row 
+- 1][$col - 1];
            $self->{'zBuffer'}[$destRow][$destCol] = $active;
            substr($backTxt[$destRow], $destCol, 1) = substr($current-
+>{'backTxt'}[$row - 1],$col - 1, 1);
            }
         }
      }

   return \(@backAtt,@backTxt);
}

[download]

And before someone mentions it, it does run under strict & warnings without a problem.

In reply to Help in improving Performance of WinConsole makeFullBackBuffer by NateTut

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