Add wallpaper-based color theming with matugen

- Matugen templates for Ghostty theme and GTK4 colors
- Ghostty uses generated wallpaper theme instead of Catppuccin
- GTK4 CSS imports generated color overrides
- Update alias runs matugen after switch to regenerate colors
- Add wallpaper fish function to change wallpaper + regen colors

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

common.nix

@@ -74,7 +74,7 @@
 
   # Shell aliases (work in both bash and fish)
   environment.shellAliases = {
-    update = "bash -c 'OLD_SYSTEM=$(readlink /run/current-system) && sudo nixos-rebuild build $@ --flake github:ediblerope/nixos-config && sudo nixos-rebuild switch $@ --flake github:ediblerope/nixos-config && nvd diff $OLD_SYSTEM /run/current-system' --";
+    update = "bash -c 'OLD_SYSTEM=$(readlink /run/current-system) && sudo nixos-rebuild build $@ --flake github:ediblerope/nixos-config && sudo nixos-rebuild switch $@ --flake github:ediblerope/nixos-config && nvd diff $OLD_SYSTEM /run/current-system && matugen image ~/.local/share/backgrounds/wallpaper.png --source-color-index 0 -m dark' --";
     clean = "sudo nix-collect-garbage -d";
     ll = "ls -alh";
     clear = "command clear";

home-manager/fred.nix

@@ -1,5 +1,5 @@
 # settings/fred.nix
-{ config, pkgs, lib, ... }:
+{ config, pkgs, lib, inputs, ... }:
 {
   # Define the state version for Home Manager
   home.stateVersion = "25.11";
@@ -20,7 +20,7 @@
     font-family = FiraMono Nerd Font
     font-size = 11
     font-thicken = true
-    theme = dark:Catppuccin Mocha,light:Catppuccin Latte
+    theme = wallpaper
     window-padding-x = 10
     window-padding-y = 10
     window-padding-balance = true
@@ -31,4 +31,19 @@
     cursor-style-blink = true
   '';
 
+  # Matugen config — templates for wallpaper-based color generation
+  home.file.".config/matugen/config.toml".text = ''
+    [config]
+    reload_apps = true
+    reload_apps_list = { ghostty = "" }
+
+    [templates.ghostty]
+    input_path = "${inputs.self}/templates/ghostty-colors"
+    output_path = "~/.config/ghostty/themes/wallpaper"
+
+    [templates.gtk4]
+    input_path = "${inputs.self}/templates/gtk4-colors.css"
+    output_path = "~/.config/gtk-4.0/colors.css"
+  '';
+
 }

settings/gnome.nix

@@ -67,6 +67,7 @@
       # Minimal titlebars — hide window buttons and shrink headerbar
       home.file.".config/gtk-4.0/gtk.css".force = true;
       home.file.".config/gtk-4.0/gtk.css".text = ''
+        @import url("colors.css");
         headerbar {
           min-height: 0;
           padding: 0;

settings/shell.nix

@@ -127,5 +127,23 @@
     end
 
     function fish_right_prompt; end
+
+    # Set wallpaper and regenerate color theme
+    function wallpaper
+      if test (count $argv) -ne 1
+        echo "Usage: wallpaper <path-to-image>"
+        return 1
+      end
+      set -l img (realpath "$argv[1]")
+      if not test -f "$img"
+        echo "File not found: $img"
+        return 1
+      end
+      cp "$img" ~/.local/share/backgrounds/wallpaper.png
+      gsettings set org.gnome.desktop.background picture-uri "file://$HOME/.local/share/backgrounds/wallpaper.png"
+      gsettings set org.gnome.desktop.background picture-uri-dark "file://$HOME/.local/share/backgrounds/wallpaper.png"
+      matugen image "$img" --source-color-index 0 -m dark
+      echo "Wallpaper and colors updated!"
+    end
   '';
 }

templates/ghostty-colors

@@ -0,0 +1,21 @@
+palette = 0={{colors.base16.base00.default.color}}
+palette = 1={{colors.base16.base08.default.color}}
+palette = 2={{colors.base16.base0b.default.color}}
+palette = 3={{colors.base16.base0a.default.color}}
+palette = 4={{colors.base16.base0d.default.color}}
+palette = 5={{colors.base16.base0e.default.color}}
+palette = 6={{colors.base16.base0c.default.color}}
+palette = 7={{colors.base16.base05.default.color}}
+palette = 8={{colors.base16.base03.default.color}}
+palette = 9={{colors.base16.base08.default.color}}
+palette = 10={{colors.base16.base0b.default.color}}
+palette = 11={{colors.base16.base0a.default.color}}
+palette = 12={{colors.base16.base0d.default.color}}
+palette = 13={{colors.base16.base0e.default.color}}
+palette = 14={{colors.base16.base0c.default.color}}
+palette = 15={{colors.base16.base07.default.color}}
+background = {{colors.primary.surface.default.color}}
+foreground = {{colors.primary.on_surface.default.color}}
+cursor-color = {{colors.primary.primary.default.color}}
+selection-background = {{colors.primary.primary_container.default.color}}
+selection-foreground = {{colors.primary.on_primary_container.default.color}}

templates/gtk4-colors.css

@@ -0,0 +1,15 @@
+@define-color accent_color {{colors.primary.primary.default.color}};
+@define-color accent_bg_color {{colors.primary.primary_container.default.color}};
+@define-color accent_fg_color {{colors.primary.on_primary_container.default.color}};
+@define-color window_bg_color {{colors.primary.surface.default.color}};
+@define-color window_fg_color {{colors.primary.on_surface.default.color}};
+@define-color view_bg_color {{colors.primary.surface_container_low.default.color}};
+@define-color view_fg_color {{colors.primary.on_surface.default.color}};
+@define-color headerbar_bg_color {{colors.primary.surface_container.default.color}};
+@define-color headerbar_fg_color {{colors.primary.on_surface.default.color}};
+@define-color card_bg_color {{colors.primary.surface_container_high.default.color}};
+@define-color card_fg_color {{colors.primary.on_surface.default.color}};
+@define-color sidebar_bg_color {{colors.primary.surface_container.default.color}};
+@define-color sidebar_fg_color {{colors.primary.on_surface.default.color}};
+@define-color popover_bg_color {{colors.primary.surface_container.default.color}};
+@define-color popover_fg_color {{colors.primary.on_surface.default.color}};