Add wallpaper switch

hm-modules/theme/default.nix

@@ -30,11 +30,53 @@ let
 
   availableVariants = concatStringsSep " " (attrNames themeVariants);
 
+  # `variant:schemeFile` pairs so the wallpaper picker can read each variant's
+  # base16 palette at runtime.
+  variantSchemes = concatStringsSep " "
+    (mapAttrsToList (variant: v: "${variant}:${v.scheme}") themeVariants);
+
   # variant:doomtheme pairs consumed by the theme-switch script's
   # best-effort Doom Emacs hook (see ./theme-switch.sh).
   doomThemeMap = concatStringsSep " "
     (mapAttrsToList (variant: theme: "${variant}:${theme}") cfg.doomThemes);
 
+  # Stylix is only declared on hosts that import its Home Manager module
+  # (e.g. `fujin`). Servers (susano, izanagi, amaterasu, ...) don't, so
+  # `stylix` isn't declared there. We probe option *declarations* (not
+  # config values) to avoid an evaluation cycle.
+  hasStylix = options ? stylix;
+
+  # --- Wallpaper handling (runtime-cloned repo + palette matching) ----------
+  wallpapersEnabled = cfg.wallpaperRepo != null;
+  wallpapersDir = "${config.home.homeDirectory}/Wallpapers";
+  # hyprpaper's config points here; set-wallpaper rebinds this symlink, so we
+  # never have to write hyprpaper config ourselves.
+  wallpaperSymlink = "${config.xdg.stateHome}/theme/wallpaper-current";
+
+  wallpaper-pick = pkgs.writeShellScriptBin "wallpaper-pick" ''
+    SCRIPT_TAG="wallpaper-pick"
+    ${builtins.readFile ./log.sh}
+    wallpapersDir="${wallpapersDir}"
+    wallpaperRepo="${cfg.wallpaperRepo or ""}"
+    variantSchemes="${variantSchemes}"
+    MAGICK="${getExe pkgs.imagemagick}"
+    GIT="${getExe pkgs.git}"
+    ${builtins.readFile ./wallpaper-pick.sh}
+  '';
+
+  wallpaper-set = pkgs.writeShellScriptBin "wallpaper-set" ''
+    SCRIPT_TAG="wallpaper-set"
+    ${builtins.readFile ./log.sh}
+    wallpaperSymlink="${wallpaperSymlink}"
+    ${builtins.readFile ./set-wallpaper.sh}
+  '';
+
+  # Applied once at login (after hyprpaper) to seed a base-variant wallpaper.
+  wallpaper-init = pkgs.writeShellScript "wallpaper-init" ''
+    wp="$(${getExe wallpaper-pick} ${baseVariant} 2>/dev/null)" || exit 0
+    [ -n "$wp" ] && ${getExe wallpaper-set} "$wp" || true
+  '';
+
   # Userspace theme switcher: activates a pre-built Home Manager
   # specialisation generation. No sudo, no OS rebuild — just runs the
   # specialisation's activation script in the base HM generation.
@@ -42,17 +84,16 @@ let
   # The script logic lives in ./theme-switch.sh (plain shell, no Nix
   # escaping); we only inject the config-derived values it needs.
   theme-switch = pkgs.writeShellScriptBin "theme-switch" ''
+    SCRIPT_TAG="theme-switch"
+    ${builtins.readFile ./log.sh}
     baseVariant="${baseVariant}"
     availableVariants="${availableVariants}"
     doomThemes="${doomThemeMap}"
+    wallpapersEnabled="${if wallpapersEnabled then "1" else "0"}"
+    wallpaperPickBin="${if wallpapersEnabled then getExe wallpaper-pick else ""}"
+    wallpaperSetBin="${if wallpapersEnabled then getExe wallpaper-set else ""}"
     ${builtins.readFile ./theme-switch.sh}
   '';
-
-  # Stylix is only declared on hosts that import its Home Manager module
-  # (e.g. `fujin`). Servers (susano, izanagi, amaterasu, ...) don't, so
-  # `stylix` isn't declared there. We probe option *declarations* (not
-  # config values) to avoid an evaluation cycle.
-  hasStylix = options ? stylix;
 in {
   options.dov.dynamic-theme = {
     enable = mkEnableOption "dynamic theme switching";
@@ -95,24 +136,43 @@ in {
         map the variants to `catppuccin-mocha` / `catppuccin-latte`.
       '';
     };
+
+    wallpaperRepo = mkOption {
+      type = types.nullOr types.str;
+      default = null;
+      example = "https://example.org/me/wallpapers.git";
+      description = ''
+        Git URL of a wallpaper repository. When set, theme-switch also picks
+        a random wallpaper whose palette matches the current variant and
+        applies it via hyprpaper. The repo is cloned to
+        `~/Wallpapers` on first use (a one-time, runtime cost — it is NOT
+        fetched at build time, so `nix build` stays fast).
+      '';
+    };
   };
 
-  config = mkIf cfg.enable (
+  config = mkIf cfg.enable (mkMerge [
     {
-      home.packages = [ theme-switch ];
+      home.packages = [ theme-switch ]
+        ++ optionals wallpapersEnabled [ wallpaper-pick wallpaper-set ];
     }
+
     # Only reference the `stylix` option where it is actually declared.
     # `mkIf false` is NOT enough: the module system still rejects a
     # definition (even a disabled one) for an option that does not exist,
     # which breaks every host that doesn't import stylix. `optionalAttrs`
-    # removes the key structurally, so non-stylix hosts evaluate cleanly.
+    # (keyed on `options ?`, i.e. *declarations* — never a config value) is
-    // optionalAttrs hasStylix {
+    # the recursion-free way to gate structure on stylix presence.
+    (optionalAttrs hasStylix {
       stylix = {
         enable = true;
         autoEnable = true;
         # Base scheme/polarity; overridable per specialisation below.
         base16Scheme = mkDefault themeVariants.${baseVariant}.scheme;
         polarity = mkDefault themeVariants.${baseVariant}.polarity;
+        # When we manage hyprpaper's wallpaper ourselves, disable stylix's
+        # hyprpaper target so the two don't fight over the wallpaper path.
+        targets.hyprpaper.enable = mkForce (!wallpapersEnabled);
       };
 
       # Generate Home Manager specialisations for every non-base variant.
@@ -126,6 +186,32 @@ in {
           };
         };
       }) specialisationVariants;
+    })
+
+    # Wallpaper handling. These options always exist structurally (HM ships
+    # services.hyprpaper and a freeform systemd.user.services), so we gate
+    # the *values* with mkIf/optionals rather than shaping structure — that
+    # avoids the config-depends-on-config recursion that optionalAttrs on a
+    # config value would cause.
+    {
+      services.hyprpaper.enable = wallpapersEnabled;
+      services.hyprpaper.settings = mkIf wallpapersEnabled {
+        splash = false;
+        wallpaper = [{ monitor = ""; path = wallpaperSymlink; }];
+      };
+
+      systemd.user.services.wallpaper-init = mkIf wallpapersEnabled {
+        Unit = {
+          Description = "Pick and apply a wallpaper matching the base theme";
+          After = [ "hyprpaper.service" ];
+          PartOf = [ "graphical-session.target" ];
+        };
+        Service = {
+          Type = "oneshot";
+          ExecStart = "${wallpaper-init}";
+        };
+        Install.WantedBy = [ "graphical-session.target" ];
+      };
     }
-  );
+  ]);
 }

hm-modules/theme/log.sh

@@ -0,0 +1,24 @@
+# shellcheck shell=bash
+# Colorful, TTY-aware logging helpers: log_info / log_warn / log_error.
+#
+# Everything is written to *stderr*, so a script's stdout stays a clean data
+# channel (e.g. wallpaper-pick prints the chosen image path on stdout while
+# its progress goes to stderr). Set SCRIPT_TAG to prefix every line with the
+# originating script, e.g. "[theme-switch] selecting wallpaper...".
+#
+# Colors are auto-disabled when stderr isn't a terminal or NO_COLOR is set.
+__theme_log_init() {
+  if [ -t 2 ] && [ -z "${NO_COLOR:-}" ]; then
+    __C_RESET=$'\033[0m'
+    __C_INFO=$'\033[1;34m'   # blue
+    __C_WARN=$'\033[1;33m'   # yellow
+    __C_ERR=$'\033[1;31m'    # red
+  else
+    __C_RESET=""; __C_INFO=""; __C_WARN=""; __C_ERR=""
+  fi
+}
+__theme_log_init
+
+log_info()  { printf '%s%s%s%s\n' "${__C_INFO}" "${SCRIPT_TAG:+[$SCRIPT_TAG] }" "$*" "${__C_RESET}" >&2; }
+log_warn()  { printf '%s%s%s%s\n' "${__C_WARN}" "${SCRIPT_TAG:+[$SCRIPT_TAG] }" "warning: $*" "${__C_RESET}" >&2; }
+log_error() { printf '%s%s%s%s\n' "${__C_ERR}"  "${SCRIPT_TAG:+[$SCRIPT_TAG] }" "error: $*"   "${__C_RESET}" >&2; }

hm-modules/theme/set-wallpaper.sh

@@ -0,0 +1,27 @@
+# shellcheck shell=bash
+# set-wallpaper — bind the runtime wallpaper symlink to $1 and restart hyprpaper
+# so it picks up the new image. hyprpaper's config (managed by Home Manager)
+# points at the symlink, so we never write hyprpaper config ourselves.
+#
+# Env (injected by the Nix wrapper):
+#   wallpaperSymlink  path to the symlink hyprpaper's `wallpaper.path` reads
+# Arg: image path
+
+: "${wallpaperSymlink:?set-wallpaper: wallpaperSymlink not set}"
+set -euo pipefail
+
+target="${1:?usage: set-wallpaper <image-path>}"
+[ -f "$target" ] || { log_error "not a file: $target"; exit 1; }
+
+mkdir -p "$(dirname "$wallpaperSymlink")"
+ln -sfn "$target" "$wallpaperSymlink"
+
+# Apply live by (re)starting the user hyprpaper service. `systemctl restart`
+# starts the unit even if it is inactive — important because a freshly-added
+# hyprpaper service won't be running until the first switch. Tolerate the
+# service being absent (e.g. on a host without hyprpaper).
+if command -v systemctl >/dev/null 2>&1 && systemctl --user restart hyprpaper 2>/dev/null; then
+  log_info "applied $(basename "$target") (hyprpaper started)"
+else
+  log_warn "could not start hyprpaper; wallpaper symlink set but not displayed"
+fi

hm-modules/theme/theme-switch.sh

@@ -57,7 +57,7 @@ do
 done
 
 if [ -z "$gen" ]; then
-  echo "error: could not resolve Home Manager base generation" >&2
+  log_error "could not resolve Home Manager base generation"
   exit 1
 fi
 
@@ -72,18 +72,16 @@ case "$variant" in
 esac
 
 if [ ! -x "$activate" ]; then
-  echo "error: variant '$variant' not found at $activate" >&2
+  log_error "variant '$variant' not found at $activate"
-  echo "Available: ${availableVariants}"
+  log_info "available: ${availableVariants}"
   exit 1
 fi
 
-echo "Switching theme to $variant..."
+log_info "switching theme to ${variant}"
 
 # Best-effort: live-switch the running Doom Emacs daemon too. No config
 # files are touched; if the daemon isn't running or emacsclient isn't
-# installed (e.g. on a server), this is silently skipped. A theme symbol
+# installed (e.g. on a server), this is silently skipped.
-# that isn't installed in Doom makes emacsclient return non-zero, which we
-# also treat as skip.
 doom_theme=""
 if [ -n "$doomThemes" ]; then
   for pair in $doomThemes; do
@@ -92,12 +90,26 @@ if [ -n "$doomThemes" ]; then
     esac
   done
 fi
-if [ -n "$doom_theme" ] && command -v emacsclient >/dev/null 2>&1; then
+if [ -n "$doom_theme" ]; then
-  if emacsclient --eval "(progn (mapc (function disable-theme) custom-enabled-themes) (load-theme (quote ${doom_theme}) t))" >/dev/null 2>&1; then
+  if command -v emacsclient >/dev/null 2>&1 \
-    echo "Doom: ${doom_theme}"
+     && emacsclient --eval "(progn (mapc (function disable-theme) custom-enabled-themes) (load-theme (quote ${doom_theme}) t))" >/dev/null 2>&1; then
+    log_info "doom: ${doom_theme}"
   else
-    echo "note: Doom theme switch skipped (daemon not running or '${doom_theme}' not installed)" >&2
+    log_warn "doom theme not applied (daemon not running or '${doom_theme}' not installed)"
   fi
 fi
 
+# Pick a palette-matching wallpaper and apply it. This BLOCKS — on the very
+# first run wallpaper-pick clones the wallpaper repo and builds the palette
+# index, which can take a few minutes; progress is logged on stderr by the
+# pick/set scripts. Failures fall back to leaving the wallpaper unchanged.
+if [ "${wallpapersEnabled:-0}" = "1" ] && [ -n "${wallpaperPickBin:-}" ] && [ -n "${wallpaperSetBin:-}" ]; then
+  if wp="$("$wallpaperPickBin" "$variant")" && [ -n "$wp" ]; then
+    "$wallpaperSetBin" "$wp" || log_warn "wallpaper apply failed"
+  else
+    log_warn "wallpaper selection failed; leaving wallpaper unchanged"
+  fi
+fi
+
+log_info "activating Home Manager specialisation"
 exec "$activate"

hm-modules/theme/wallpaper-pick.sh

@@ -0,0 +1,131 @@
+# shellcheck shell=bash
+# wallpaper-pick — print a random wallpaper from $wallpapersDir whose palette
+# best matches the given theme variant. Per-image palettes are extracted once
+# (ImageMagick) and cached, keyed by the (immutable) source path so a rebuild
+# that changes the wallpaper set reindexes automatically.
+#
+# Matching uses several key colors on both sides: the variant's base16
+# base00–base05 (the background→foreground neutral range) are each matched to
+# their nearest wallpaper dominant color; the sum of those nearest distances
+# is the score. A random image is picked from the lowest-score tier.
+#
+# Env (injected by the Nix wrapper):
+#   wallpapersDir    directory of wallpaper images (~/Wallpapers, a git clone)
+#   wallpaperRepo    git URL cloned into wallpapersDir on first use
+#   variantSchemes   space-separated `variant:schemeFile` pairs (base16 YAML)
+#   MAGICK           path to the ImageMagick `magick` binary
+#   GIT              path to the `git` binary
+# Arg: variant name (e.g. gruvbox-dark)
+
+: "${wallpapersDir:?wallpaper-pick: wallpapersDir not set}"
+: "${wallpaperRepo:?wallpaper-pick: wallpaperRepo not set}"
+: "${variantSchemes:?wallpaper-pick: variantSchemes not set}"
+: "${MAGICK:?wallpaper-pick: MAGICK not set}"
+: "${GIT:?wallpaper-pick: GIT not set}"
+set -euo pipefail
+
+variant="${1:?usage: wallpaper-pick <variant>}"
+
+# Ensure the wallpaper repo is cloned locally. The clone is a one-time cost
+# paid on first use (not at build time), keeping `nix build` fast.
+if [ ! -d "$wallpapersDir/.git" ]; then
+  log_info "cloning wallpaper repo (one-time, may take a few minutes)..."
+  mkdir -p "$(dirname "$wallpapersDir")"
+  "$GIT" clone --depth=1 --single-branch "$wallpaperRepo" "$wallpapersDir" >&2
+  log_info "clone ready"
+fi
+
+cache_dir="${XDG_CACHE_HOME:-$HOME/.cache}/wallpaper-pick"
+palettes="$cache_dir/palettes.tsv"
+stamp_file="$cache_dir/source"
+
+# Cache key: the clone's current commit, so a `git pull` reindexes. Falls back
+# to the resolved path if git fails for some reason.
+src_stamp="$("$GIT" -C "$wallpapersDir" rev-parse HEAD 2>/dev/null || readlink -f "$wallpapersDir")"
+
+rebuild_cache() {
+  img_count="$(find "$wallpapersDir" -type f \( -iname '*.png' -o -iname '*.jpg' -o -iname '*.jpeg' -o -iname '*.webp' \) -printf . 2>/dev/null | wc -c)"
+  log_info "indexing ${img_count} wallpapers (one-time, building palette cache)..."
+  mkdir -p "$cache_dir"
+  tmp="$palettes.tmp"
+  : > "$tmp"
+  jobs="$(nproc 2>/dev/null || echo 4)"
+
+  # For each image: top dominant colors (by pixel count) as space-separated #hex.
+  find "$wallpapersDir" -type f \( -iname '*.png' -o -iname '*.jpg' -o -iname '*.jpeg' -o -iname '*.webp' \) -print0 \
+    | xargs -0 -P "$jobs" -n1 sh -c '
+        MAGICK="$0" img="$1"
+        "$MAGICK" "$img" -resize 128x128^ -gravity center -extent 128x128 +dither -colors 8 -format "%c" histogram:info: 2>/dev/null \
+          | grep -E "^[[:space:]]*[0-9]+:" | sort -rn | grep -oE "#[0-9A-Fa-f]{6}" | head -6 | paste -sd" " - \
+          | { read -r hex; [ -n "$hex" ] && printf "%s\t%s\n" "$img" "$hex"; }
+      ' "$MAGICK" >> "$tmp" || true
+
+  mv "$tmp" "$palettes"
+  printf '%s\n' "$src_stamp" > "$stamp_file"
+}
+
+if [ ! -f "$palettes" ] || [ ! -f "$stamp_file" ] || [ "$(cat "$stamp_file")" != "$src_stamp" ]; then
+  rebuild_cache
+fi
+
+# Resolve the base16 scheme file for the requested variant.
+scheme=""
+for pair in $variantSchemes; do
+  case "$pair" in
+    "${variant}":*) scheme="${pair#*:}"; break ;;
+  esac
+done
+[ -n "$scheme" ] || { log_error "no scheme mapped for variant '$variant'"; exit 2; }
+
+# Theme key colors: base00–base05 hex (one per line, with leading #).
+theme_colors="$(grep -E '^[[:space:]]*base0[0-5]:' "$scheme" | grep -oE '#[0-9A-Fa-f]{6}')"
+[ -n "$theme_colors" ] || { log_error "could not parse base00–05 from $scheme"; exit 2; }
+
+# hex (no #) -> decimal rgb on stdout
+hex2dec() { printf '%d %d %d\n' "$((16#${1:0:2}))" "$((16#${1:2:2}))" "$((16#${1:4:2}))"; }
+
+# Theme colors as parallel arrays.
+t_r=(); t_g=(); t_b=()
+while read -r h; do
+  read -r r g b < <(hex2dec "${h#\#}")
+  t_r+=("$r"); t_g+=("$g"); t_b+=("$b")
+done <<< "$theme_colors"
+
+# Score every indexed wallpaper: sum over theme colors of nearest wallpaper color.
+scores="$cache_dir/scores.tmp"
+: > "$scores"
+while IFS=$'\t' read -r path whexes; do
+  w_r=(); w_g=(); w_b=()
+  for wh in $whexes; do
+    read -r wr wg wb < <(hex2dec "${wh#\#}")
+    w_r+=("$wr"); w_g+=("$wg"); w_b+=("$wb")
+  done
+  if [ "${#w_r[@]}" -eq 0 ]; then continue; fi
+  total=0
+  for i in "${!t_r[@]}"; do
+    mind=1000000000
+    for j in "${!w_r[@]}"; do
+      dr=$(( t_r[i] - w_r[j] )); dg=$(( t_g[i] - w_g[j] )); db=$(( t_b[i] - w_b[j] ))
+      cd=$(( dr*dr + dg*dg + db*db ))
+      if [ "$cd" -lt "$mind" ]; then mind=$cd; fi
+    done
+    total=$(( total + mind ))
+  done
+  printf '%s\t%s\n' "$total" "$path"
+done < "$palettes" | sort -n -k1 > "$scores"
+
+[ -s "$scores" ] || { log_error "no wallpapers indexed"; exit 3; }
+
+# Matched tier: within 1.4x of the best score (fall back to closest 20).
+best="$(head -n1 "$scores" | cut -f1)"
+threshold=$(( best * 14 / 10 ))
+matched="$(awk -F'\t' -v t="$threshold" '$1 <= t {print $2}' "$scores")"
+if [ "$(printf '%s\n' "$matched" | grep -c .)" -lt 5 ]; then
+  matched="$(head -n20 "$scores" | cut -f2)"
+fi
+
+# Print the chosen PATH on stdout (data channel for callers) and log the
+# human-readable choice on stderr.
+chosen="$(printf '%s\n' "$matched" | shuf -n1)"
+log_info "picked $(basename "$chosen") for ${variant}"
+printf '%s\n' "$chosen"

machines/fujin/main/home.nix

@@ -70,7 +70,10 @@
 
     notification.mako.enable = true;
 
-    dynamic-theme.enable = true;
+    dynamic-theme = {
+      enable = true;
+      wallpaperRepo = "https://gitea.susano-homelab.duckdns.org/fujin/gruvbox-wallpapers.git";
+    };
   };
 
   programs = {
@@ -88,13 +91,6 @@
           directory = ["/home/${username}/nixos-dotfiles" "/home/${username}/.cache/nix"];
         };
       };
-      hooks = {
-        commit-msg = pkgs.writeScript "commit-msg" ''
-          #!${pkgs.bash}/bin/bash
-          # Remove Co-Authored-by lines from commit messages (Claude likes to add these)
-          ${pkgs.gnused}/bin/sed -i '/^Co-[Aa]uthored-[Bb]y:/d' "$1"
-        '';
-      };
     };
   };