IPerl display demo

author: Zaki Mughal

date: 2015-02-09

This notebook demonstrates how to use the rich display system in IPerl and how it can be extended on the fly.

All data that is displayed implements a Displayable role. This role requires a method called iperl_data_representations that returns a HashRef of different representations of the data where the keys are the MIME type of the data (e.g., text/html) and values are the strings that contain the bytestream for that MIME type. For example, with PNG, we have

  use v5.16;
  use DDP; # Data::Printer
  my $png_display = Devel::IPerl::Display::PNG->new( "http://www.libpng.org/pub/png/PngSuite/ccwn3p08.png" );
  say &p( [ keys $png_display->iperl_data_representations ] );
    [0] "image/png",                                                            
    [1] "text/html",                                                            
    [2] "text/plain"                                                            

Notice that I just displayed that PNG by just putting the $png_display variable at the end? That's because any displayable is automatically displayed if it is at the end of a cell.

But there's a problem: I don't want to type or remember Devel::IPerl::Display::PNG every time I want to load up a PNG.

Instead, you can just call the helper method IPerl->png() and you'll get the same result.

  IPerl->png( "http://www.libpng.org/pub/png/PngSuite/ccwn3p08.png" );

There are other Displayables too. For example, let's load up an <iframe>.

  my $iframe_display = IPerl->iframe( "http://metacpan.org/recent", width => "75%" );

What if we want to display multiple things in one cell? For example, we want to loop over a number of images and display each of them?

You can do that by calling the IPerl->display() on the Displayable object.

  my @svg = split ' ', q[
  IPerl->display( IPerl->svg( $_ , width => "200" ) ) for @svg;

There is also a way to display arbitrary HTML. Here, we create a simple HTML table that loops over a 2D nested ArrayRef.

We could send the string directly to the IPerl->html() method, but that isn't very DRY. Instead, we'll create our own helper!

  IPerl->helper( my_table => sub {
      my ($self, $data) = @_;
      return unless ref $data eq 'ARRAY';
      my $html = "<table>";
      for my $row (@$data) {
          $html .= "<tr>";
          for my $cell (@$row) {
               my $cell_html = $cell->iperl_data_representations->{"text/html"};
               $html .=  "<td>$cell_html</td>\n";
          $html .= "</tr>";
      $html .= "</table>";
      IPerl->html( $html );
  my $N = 4; my $M = 10;
  my $d = [ ([ ( $png_display ) x $M ]) x $N  ];
  IPerl->my_table(  $d  );

There are other plugins besides the Displayables that work directly on file types (PNG, SVG, HTML, etc.).

For example, you can load a plugin that adds a role to PDL::Graphics::Gnuplot and makes it displayable as an SVG.

  IPerl->load_plugin( "PDLGraphicsGnuplot" );
  use PDL;
  use PDL::Graphics::Gnuplot;
  use PDL::Constants qw(PI);
  my $gp = gpwin();
  # do some styling
  $gp->option( topcmd => <<'GP');
  # define axis
  # remove border on top and right and set color to gray
  set style line 11 lc rgb '#808080' lt 1
  set border 3 back ls 11
  set tics nomirror
  # define grid
  set style line 12 lc rgb '#808080' lt 0 lw 1
  set grid back ls 12
  my $theta = zeros(200)->xlinvals(-1*PI, 1*PI);
  $gp->plot( { lw => 2 }, $theta, sin($theta), {}, $theta, cos($theta)  );
  IPerl->display( IPerl->tex( q| $\sin\theta$ and $\cos\theta$ | ) );

Have fun and let me know what you make with your IPerl notebooks!

Feel free to add your notebooks to the IPerl wiki!