feat: redmine_tonalmine plugin for default and per-account appearance

Admins set the default mode, contrast and color on Settings > Display,
shown as three labelled form rows below the Theme select. Logged-in
users' choices are saved on their account and override only the parts
they changed; anonymous visitors get the default.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

redmine_tonalmine/lib/redmine_tonalmine/appearance.rb

@@ -0,0 +1,58 @@
+module RedmineTonalmine
+  # Validates appearance hashes ({mode, contrast, palette, seed, css}) coming from users and from
+  # the Display settings form. Any part may be missing: it then falls back to the default.
+  module Appearance
+    MODES = %w[auto light dark].freeze
+    CONTRASTS = %w[standard medium high].freeze
+    # Ids must match PALETTES in tonalmine/javascripts/theme.js (tools/palettes checks this).
+    PALETTES = %w[purple blue green orange].freeze
+    KEYS = %w[mode contrast palette seed css].freeze
+    MAX_CSS = 32.kilobytes
+
+    module_function
+
+    # Returns a list of problems; empty when the hash is valid.
+    def errors(hash)
+      prefs = normalize(hash)
+      errors = hash.to_h.filter_map do |key, value|
+        if !KEYS.include?(key.to_s) then "unknown key #{key}"
+        elsif !value.nil? && !value.is_a?(String) then "invalid #{key}"
+        end
+      end
+      errors << 'invalid mode' if prefs['mode'] && !MODES.include?(prefs['mode'])
+      errors << 'invalid contrast' if prefs['contrast'] && !CONTRASTS.include?(prefs['contrast'])
+      errors.concat(custom_errors(prefs))
+      errors
+    end
+
+    # Returns only the valid parts, with string keys.
+    def clean(hash)
+      prefs = normalize(hash)
+      prefs.delete('mode') unless MODES.include?(prefs['mode'])
+      prefs.delete('contrast') unless CONTRASTS.include?(prefs['contrast'])
+      prefs = prefs.except('palette', 'seed', 'css') if custom_errors(prefs).any?
+      prefs.compact
+    end
+
+    # String keys, known keys only, blank values dropped (the settings form posts "" for unset parts).
+    def normalize(hash)
+      hash.to_h.transform_keys(&:to_s).slice(*KEYS).select { |_, value| value.is_a?(String) && value.present? }
+    end
+
+    # palette, seed and css belong together: a custom palette needs its seed and generated CSS.
+    # A built-in palette may keep the last custom color, so the custom swatch can switch back.
+    def custom_errors(prefs)
+      palette, seed, css = prefs.values_at('palette', 'seed', 'css')
+      return [] if palette.nil? && seed.nil? && css.nil?
+
+      required = palette == 'custom'
+      errors = []
+      errors << 'invalid palette' unless required || PALETTES.include?(palette)
+      errors << 'invalid seed' unless (seed.nil? && !required) || seed.to_s.match?(/\A#\h{6}\z/)
+      # The CSS is rendered into a <script> as JSON and applied via style.textContent; refusing
+      # "<" keeps it from ever closing either element.
+      errors << 'invalid css' unless (css.nil? && !required) || (css && !css.include?('<') && css.bytesize <= MAX_CSS)
+      errors
+    end
+  end
+end

redmine_tonalmine/lib/redmine_tonalmine/hooks.rb

@@ -0,0 +1,19 @@
+module RedmineTonalmine
+  # Hands the default and the current user's appearance to theme.js. Rendered in <head> right
+  # after the theme's scripts, so the colors are applied before the page is painted.
+  class Hooks < Redmine::Hook::ViewListener
+    def view_layouts_base_html_head(context = {})
+      defaults = Appearance.clean(Setting.plugin_redmine_tonalmine)
+      config = {defaults: defaults, user: nil, url: nil}
+      if User.current.logged?
+        user = Appearance.clean(User.current.pref[:tonalmine])
+        # The user's own palette replaces the default one: skip the default's generated CSS.
+        # Admins keep it: the Display settings tab posts the whole default back.
+        defaults.delete('css') if user['palette'] && !User.current.admin?
+        config.update(user: user, url: tonalmine_appearance_path)
+      end
+      # to_json escapes <, > and &, so values can't end the script element.
+      javascript_tag "window.Tonalmine && Tonalmine.configure(#{config.to_json});"
+    end
+  end
+end