#!/usr/bin/perl
# desktop_watcher.pl
# written Joseph Bylund, 2011/10/12
# this script watches for desktop changes, and when it finds one it changes the background. Currently this is a hackjob, but it 
# should work if you fix the paths and number the files you'd like to  use as 1.jpg, 2.jpg, 3.jpg (for workspaces 1,2,3 
# respectively).  You can even use xml files as per the cosmos background as your backgrounds, just rename to 1.xml, 
# 2.xml ... You'll also have to change the extension to xml from jpg.
# also update the path_to_bg_files to where you're keeping your background files.  

use strict;

use Time::HiRes qw( nanosleep );

my $extension = "jpg";

my $user = `whoami`;
chomp($user);

my $path_to_bg_files = "/home/$user/Desktop/multi_wallpaper_test";
my $last_workspace = &get_workspace;
my $current_workspace = $last_workspace;

while(1)
{
	$current_workspace = &get_workspace;
	if($current_workspace != $last_workspace)
	{
		$last_workspace = $current_workspace;
		system("gconftool --type string --set /desktop/gnome/background/picture_filename \"$path_to_bg_files/$current_workspace.${extension}\"");
	}
	nanosleep(int(0.5*10^9)); # increase sleep timer to reduce cpu usage, decrease to improve response time
}

sub get_workspace
{
	my $current_workspace;
	if(&get_window_manager eq "metacity")
	{
		$current_workspace = `wmctrl -d|grep \\*`;
		chomp($current_workspace);
		$current_workspace =~ s/.*Workspace//g;		
		$current_workspace =~ s/\s*//g;
		$current_workspace;
	}
	else
	{
		my $current_vp = `wmctrl -d`;
		chomp($current_vp);
		$current_vp =~ s/.*VP: //;#cut off leading
		$current_vp =~ s/,.*//;#cut off trailing
		$current_workspace = $current_vp/&get_workspace_width + 1; # this actually gives only the column at the moment, need to add row
	}
}

sub get_workspace_width
{
	my $workspace_width = `wmctrl -d|head -n 1`;
	chomp($workspace_width);
	$workspace_width =~ s/.*WA: [^ ]* //;
	$workspace_width =~ s/x.*//;
	$workspace_width = int($workspace_width);
}

sub get_window_manager
{
	my $lines = `wmctrl -d|wc -l`;
	chomp($lines);
	if($lines > 1)
	{"metacity";}
	else
	{"compiz";}
}