Better comments, prevent duplicate waybars

Generate a single config file. Multiple processes seems to have run into
a bug where waybar will restore killed bars.

sway/displays.pl

@@ -1,5 +1,16 @@
 #!/usr/bin/perl
 
+########################################################################
+# Usage
+########################################################################
+#
+# $ displays.pl [layout] [-w]
+#
+# layout    Name of desired layout, as configured starting at line 100
+#           If missing, last known layout is used (logged to file $last)
+# -w        (Re)load waybar only. Skip display configuration. Only kill
+#           existing waybars and start new ones for desired layout
+
 ########################################################################
 # Dependencies
 ########################################################################
@@ -17,11 +28,14 @@
 # "output": __OUTPUT__
 # "position": __POSITION__
 # "width": __WIDTH__ (optional)
-my $waybar_template = '/home/jpm/.config/waybar/config.template';
+my $waybar_template = "$ENV{'HOME'}/.config/waybar/config.template";
 
 # Temporary directory to save generated waybar config(s)
 my $waybar_temporary = '/tmp';
 
+# File to log and recover last used layout name
+my $last = "$ENV{'HOME'}/.config/last_display";
+
 ########################################################################
 # Display Serials and Names
 ########################################################################
@@ -138,8 +152,6 @@ my %configs = (
 use strict;
 use warnings;
 
-# Bail if zero or >1 args
-my $last = "/home/jpm/.config/last_display";
 my $waybar_only = 0;
 my $config;
 
@@ -157,12 +169,12 @@ if (scalar(@ARGV)) {
     }
 }
 
+# Get previous config if one is not provided
 unless (defined $config) {
-    open(my $fh, '<', $last);
+    open(my $fh, '<', $last) || die "Config name not provided and failed to open $last\n";
     $config = <$fh>;
     close($fh);
     chomp $config;
-    print "$config\n";
 }
 
 # Bail if requested config doesn't exist
@@ -170,11 +182,14 @@ unless (defined $configs{$config}) {
     die "$config is not a defined configuration: " . join(', ', keys %configs) . "\n";
 }
 
-# Import and setup JSON object
-use JSON::XS;
-my $json = JSON::XS->new();
+# Write config that is to be used so that it can be recovered as default
+open(my $fh, '>', $last) || print STDERR "Config name cannot be written to $last\n";
+print $fh $config;
+close($fh);
 
 # Fetch connected displays
+use JSON::XS;
+my $json = JSON::XS->new();
 my $displays_raw = `swaymsg -t get_outputs --raw`;
 my $displays = $json->decode($displays_raw);
 
@@ -182,7 +197,6 @@ my $displays = $json->decode($displays_raw);
 # displays and a list of displays to disable
 my $on;
 my @off;
-
 for (my $i = 0; $i < scalar(@$displays); $i++) {
 
     # If a display is found without any settings, print error and turn it off
@@ -203,8 +217,9 @@ for (my $i = 0; $i < scalar(@$displays); $i++) {
 
 }
 
+# Skip enabling/disabling displays if only running waybar (re)start
 unless ($waybar_only) {
-    # Number of simultaneous outputs is limited by  possible, so disabled displays first
+    # Number of simultaneous outputs is limited by gpu, so disabled displays first
     foreach (@off) {
 
         # Sway returns status as JSON
@@ -226,14 +241,35 @@ foreach my $p ( @{ $t->table } ) {
     my $cmndline = $p->{'cmndline'};
     $cmndline =~ s/\s*$//g;
     if ($cmndline =~ /^waybar.*/) {
+        # Never kill this process
         if ($p->{'pid'} == $$) {
             next;
+        # SIGKILL match
+        # TODO BUG: when multiple processes are running, some respawn with new PIDs. IDK why?
         } else {
             $p->kill(9);
         }
     }
 }
 
+# Load in config template
+my $template;
+if (open (my $fh, '<', $waybar_template)) {
+    while (<$fh>) {
+        $template .= $_;
+    }
+    close $fh;
+    chomp $template;
+} else {
+    print STDERR "Failed to load template $waybar_template\n";
+}
+
+# If template is already set up as an array, remove the square brackets so that we can concatenate multiple displays
+$template =~ s/^[^\[\{]*\[(.*)\]$/$1/s;
+
+# Setup waybar config file
+my $waybar = '';
+
 # Configure each enabled display
 foreach my $out (keys %$on) {
 
@@ -262,22 +298,15 @@ foreach my $out (keys %$on) {
         }
     }
 
-    # If waybar position is set, fork, generate config and execute it
-    if (defined $on->{$out}->{waybar}) {
-        my $pid = fork;
-        unless ($pid) {
-            open STDIN,  '/dev/null';
-            open STDOUT, '>>/dev/null';
-            open STDERR, '>>/dev/null';
+    # Skip waybar setup if template failed to be loaded
+    if ( (defined $template) && (defined $on->{$out}->{waybar}) && ($on->{$out}->{waybar} =~ m/(top|bottom|left|right)/) ) {
 
-            # Load in config template
-            my $waybar;
-            open (my $fh, '<', $waybar_template);
-            while (<$fh>) {
-                $waybar .= $_;
+        # If there's already a display set up, add a comma
+        unless ($waybar eq '') {
+            $waybar .= ',';
         }
-            close $fh;
-            chomp $waybar;
+
+        $waybar .= $template;
 
         # Replace basic preferences
         $waybar =~ s/__OUTPUT__/"$on->{$out}->{output}"/;
@@ -289,8 +318,20 @@ foreach my $out (keys %$on) {
             $waybar =~ s/([^\s]*\s*)__WIDTH__/\/\/ $1__WIDTH__/gg;
         }
 
+    }
+}
+
+# Restore array formatting
+$waybar = '[' . $waybar . ']';
+
+# Start Waybar as fork
+my $pid = fork;
+unless ($pid) {
+    open STDIN,  '/dev/null';
+    open STDOUT, '>>/dev/null';
+    open STDERR, '>>/dev/null';
     # Write config to a temporary file
-            my $tmp = $waybar_temporary . "/" . $on->{$out}->{output} . ".tmp";
+    my $tmp = $waybar_temporary . "/waybar-" . time() .".config";
     open ($fh, '>', $tmp);
     print $fh $waybar;
     close $fh;
@@ -299,9 +340,3 @@ foreach my $out (keys %$on) {
     # Remove config
     unlink $tmp;
 }
-    }
-}
-
-open(my $fh, '>', $last);
-print $fh $config;
-close($fh);