#!/usr/bin/perl -w
# Copyright © 2003, 2005 Jamie Zawinski <jwz@jwz.org>.
#
# Permission to use, copy, modify, distribute, and sell this software and its
# documentation for any purpose is hereby granted without fee, provided that
# the above copyright notice appear in all copies and that both that
# copyright notice and this permission notice appear in supporting
# documentation.  No representations are made about the suitability of this
# software for any purpose.  It is provided "as is" without express or 
# implied warranty.
#
# This program attempts to grab an image of the desktop, and then load
# it on to the root window using the "xscreensaver-getimage-file"
# program.  Various frame-grabbing programs are known, and the first
# one found is used.
#
# NOTE:  This script is only used on MacOS X / XDarwin systems, because
#        on those systems, it's necessary to use the "screencapture"
#        program to get an image of the desktop -- the usual X11
#        mechanism for grabbing the screen doesn't work on OSX.
#
# The various xscreensaver hacks that manipulate images ("slidescreen",
# "jigsaw", etc.) get the image to manipulate by running the
# "xscreensaver-getimage" program.
#
# "xscreensaver-getimage" will invoke this program, depending on the
# value of the "grabDesktopImages" setting in the ~/.xscreensaver file
# (or in /usr/lib/X11/app-defaults/XScreenSaver).
#
# Created: 20-Oct-2003.

require 5;
#use diagnostics;	# Fails on some MacOS 10.5 systems
use strict;

my $progname = $0; $progname =~ s@.*/@@g;
my $version = q{ $Revision: 1.4 $ }; $version =~ s/^[^0-9]+([0-9.]+).*$/$1/;

my @grabber   = ("screencapture", "-x");
my @converter = ("pdf2jpeg");

my $verbose = 0;
my $use_stdout_p = 0;
my $return_filename_p = 0;


sub error {
  ($_) = @_;
  print STDERR "$progname: $_\n";
  exit 1;
}

# returns the full path of the named program, or undef.
#
sub which {
  my ($prog) = @_;
  foreach (split (/:/, $ENV{PATH})) {
    if (-x "$_/$prog") {
      return $prog;
    }
  }
  return undef;
}

sub check_path {
  my $ok = 1;
  foreach ($grabber[0], $converter[0]) {
    if (! which ($_)) {
      print STDERR "$progname: \"$_\" not found on \$PATH.\n";
      $ok = 0;
    }
  }
  exit (1) unless $ok;
}


sub grab_image {

  check_path();

  my $tmpdir = $ENV{TMPDIR};
  $tmpdir = "/tmp" unless $tmpdir;

  my $tmpfile = sprintf ("%s/xssgrab.%08x.pdf", $tmpdir, rand(0xffffffff));
  my @cmd     = (@grabber, $tmpfile);

  unlink $tmpfile;

  print STDERR "$progname: executing \"" . join(' ', @cmd) . "\"\n"
    if ($verbose);
  system (@cmd);

  my @st = stat($tmpfile);
  my $size = (@st ? $st[7] : 0);
  if ($size <= 2048) {
    unlink $tmpfile;
    if ($size == 0) {
      error "\"" . join(' ', @cmd) . "\" produced no data.";
    } else {
      error "\"" . join(' ', @cmd) . "\" produced only $size bytes.";
    }
  }

  # On MacOS 10.3, "screencapture -x" always wrote a PDF.
  # On 10.4.2, it writes a PNG by default, and the output format can be
  # changed with the new "-t" argument.
  #
  # So, for maximal compatibility, we run it without "-t", but look at
  # the first few bytes to see if it's a PDF, and if it is, convert it
  # to a JPEG first.  Otherwise, we assume that whatever screencapture
  # wrote is a file format that xscreensaver-getimage-file can already
  # cope with (though it will have the extension ".pdf", regardless of
  # what is actually in the file).
  #
  my $pdf_p = 0;
  {
    local *IN;
    open (IN, "<$tmpfile") || error ("$tmpfile: $!");
    my $buf = '';
    read (IN, $buf, 10);
    close IN;
    $pdf_p = ($buf =~ m/^%PDF-/s);
  }

  # If it's a PDF, convert it to a JPEG.
  #
  if ($pdf_p)
    {
      my $jpgfile = $tmpfile;
      $jpgfile =~ s/\.[^.]+$//;
      $jpgfile .= ".jpg";

      @cmd = (@converter, $tmpfile, $jpgfile);
      push @cmd, "--verbose" if ($verbose);

      print STDERR "$progname: executing \"" . join(' ', @cmd) . "\"\n"
        if ($verbose);
      system (@cmd);
      unlink $tmpfile;
      $tmpfile = $jpgfile;
    }

  @st = stat($tmpfile);
  $size = (@st ? $st[7] : 0);
  if ($size <= 2048) {
    unlink $tmpfile;
    if ($size == 0) {
      error "\"" . join(' ', @cmd) . "\" produced no data.";
    } else {
      error "\"" . join(' ', @cmd) . "\" produced only $size bytes.";
    }
  }

  if ($return_filename_p) {
    print STDERR "$progname: wrote \"$tmpfile\"\n" if ($verbose);
    print STDOUT "$tmpfile\n";

  } elsif ($use_stdout_p) {
    local *IN;
    my $ppm = "";
    my $reader = "djpeg $tmpfile";
    $reader .= " 2>/dev/null" if ($verbose <= 1);
    $reader .= " |";

    open(IN, $reader) || error "reading $tmpfile: $!";
    print STDERR "$progname: reading $tmpfile\n" if ($verbose > 1);
    while (<IN>) { $ppm .= $_; }
    close IN;
    unlink $tmpfile;
    print STDOUT $ppm;

  } else {

    @cmd = ("xscreensaver-getimage-file");
    push @cmd, "--verbose" if ($verbose);
    push @cmd, $tmpfile;

    print STDERR "$progname: executing \"" . join(' ', @cmd) . "\"\n"
      if ($verbose);
    system (@cmd);

    unlink $tmpfile;
  }
}


sub usage {
  print STDERR "usage: $progname [--verbose] [--name | --stdout]\n";
  exit 1;
}

sub main {
  while ($_ = $ARGV[0]) {
    shift @ARGV;
    if ($_ eq "--verbose") { $verbose++; }
    elsif (m/^-v+$/) { $verbose += length($_)-1; }
    elsif (m/^--?stdout$/) { $use_stdout_p = 1; }
    elsif (m/^--?name$/)   { $return_filename_p = 1; }
    elsif (m/^-./) { usage; }
    else { usage; }
  }

  grab_image();
}

main;
exit 0;