Add site setting to pick dark mode color scheme (#10390)

Co-authored-by: Robin Ward <robin.ward@gmail.com>

app/models/color_scheme_setting.rb

@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+class ColorSchemeSetting < EnumSiteSetting
+
+  def self.valid_value?(val)
+    val == -1 || ColorScheme.find_by_id(val)
+  end
+
+  def self.values
+    values = [{ name: I18n.t("site_settings.dark_mode_none"), value: -1 }]
+    ColorScheme.all.map do |c|
+      values << { name: c.name, value: c.id }
+    end
+    values
+  end
+
+end

config/locales/server.en.yml

@@ -1834,6 +1834,8 @@ en:
     desktop_category_page_style: "Visual style for the /categories page."
     category_colors: "A list of hexadecimal color values allowed for categories."
     category_style: "Visual style for category badges."
+    default_dark_mode_color_scheme_id: "The color scheme used when in dark mode."
+    dark_mode_none: "None"
 
     max_image_size_kb: "The maximum image upload size in kB. This must be configured in nginx (client_max_body_size) / apache or proxy as well. Images larger than this and smaller than client_max_body_size will be resized to fit on upload."
     max_attachment_size_kb: "The maximum attachment files upload size in kB. This must be configured in nginx (client_max_body_size) / apache or proxy as well."

config/site_settings.yml

@@ -247,7 +247,8 @@ basic:
     hidden: true
   default_dark_mode_color_scheme_id:
     default: -1
-    hidden: true
+    type: enum
+    enum: "ColorSchemeSetting"
     client: true
   relative_date_duration:
     client: true

spec/helpers/application_helper_spec.rb

@@ -364,8 +364,10 @@ describe ApplicationHelper do
       expect(cs_stylesheets.scan("stylesheets/color_definitions").size).to eq(2)
     end
 
-    it 'fails gracefully when the dark color scheme ID is set but missing' do
-      SiteSetting.default_dark_mode_color_scheme_id = -5
+    it 'handles a missing dark color scheme gracefully' do
+      scheme = ColorScheme.create!(name: "pyramid")
+      SiteSetting.default_dark_mode_color_scheme_id = scheme.id
+      scheme.destroy!
       cs_stylesheets = helper.discourse_color_scheme_stylesheets
 
       expect(cs_stylesheets).to include("stylesheets/color_definitions")