[lock,idle] Fixes the swaylock script to work for multiple monitors and fixes it's invocation

home-manager/features/hypr/hypridle.nix

@@ -4,7 +4,7 @@
     enable = true;
     settings = {
       general = {
-        lock_cmd = "pidof swaylock || swaylock"; # avoid starting multiple lock instances.
+        lock_cmd = "pidof swaylock || ~/.config/swaylock/swaylock.sh"; # avoid starting multiple lock instances.
         before_sleep_cmd = "loginctl lock-session"; # lock before suspend.
         after_sleep_cmd = "hyprctl dispatch dpms on"; # to avoid having to press a key twice to turn on the display.
       };

home-manager/features/swaylock.nix

@@ -12,12 +12,26 @@
 
   home.file.".config/swaylock/swaylock.sh" = {
     executable = true;
+    # A script that will take the wallpaper folder for each monitor (see
+    # wallpaper.nix) and use a random image as the background on each monitor.
     text = ''
-      #!/bin/env bash
+      #!/usr/bin/env sh
 
-      image=`fd . ~/Pictures/Wallpaper --type f | sort -R | tail -1`
+      wallpaper_dir="$HOME/Pictures/Wallpaper"
+      cmd="swaylock"
 
-      swaylock --image "$image"
+      for monitor in $(hyprctl monitors | awk '/^Monitor/ { print $2 }'); do
+        dir="$wallpaper_dir/$monitor"
+        if [ -d "$dir" ]; then
+          image=$(find "$dir" -type f | shuf -n 1)
+          if [ -n "$image" ]; then
+            cmd="$cmd --image \"$monitor:$image\""
+          fi
+        fi
+      done
+
+      # Eval to handle the quoted image paths correctly
+      eval $cmd
     '';
   };
 }

home-manager/features/wallpaper.nix

@@ -12,6 +12,7 @@ monitors:
         map (mon: {
           name = mon;
           value = {
+            # Each monitor gets a folder under wallpaper that containes the current images.
             path = "~/Pictures/Wallpaper/${mon}";
           };
         }) monitors