UI: Add settings option to change main UI color

config/settings-default.yaml

@@ -171,3 +171,9 @@ retry-delivery-every:
 # documents. The available styles are listed in the "Text.Pandoc.Highlighting"
 # module documentation.
 highlight-style:        zenburn
+
+# Color scheme to use for UI header, footer, links on pages etc., should help
+# with visually identifying instances that may otherwise look very much alike.
+# Any number is valid; the scheme is chosen via modulo the number of available
+# schemes.
+main-color:             0

src/Vervis/Foundation.hs

@@ -275,6 +275,15 @@ instance Yesod App where
                 instanceHost = appInstanceHost settings
                 federationDisabled = not $ appFederation settings
                 federatedServers = appInstances settings
+                main =
+                    case appMainColor settings `mod` 6 of
+                        0 -> blue
+                        1 -> green
+                        2 -> red
+                        3 -> yellow
+                        4 -> magenta
+                        5 -> cyan
+                        _ -> error "Impossible mod 6"
             $(widgetFile "default-layout")
         withUrlRenderer $(hamletFile "templates/default-layout-wrapper.hamlet")
         where

src/Vervis/Settings.hs

@@ -194,6 +194,11 @@ data AppSettings = AppSettings
       -- | Default color scheme for syntax highlighting of code blocks inside
       -- documentes rendered with pandoc.
     , appHighlightStyle           :: Text
+      -- | COlor scheme to use for UI header, footer, links on pages etc.,
+      -- should help with visually identifying instances that may otherwise
+      -- look very much alike. Any number is valid; the scheme is chosen via
+      -- modulo the number of available schemes.
+    , appMainColor                :: Int
     }
 
 instance FromJSON AppSettings where
@@ -253,6 +258,7 @@ instance FromJSON AppSettings where
             case lookup s highlightingStyles of
                 Nothing -> fail $ "Highlighting style " ++ s ++ " not found"
                 Just _ -> return $ T.pack s
+        appMainColor                <- o .:? "main-color" .!= 0
 
         return AppSettings {..}
         where

templates/default-layout.cassius

@@ -27,13 +27,13 @@ body
 header
     padding: 1.2rem 1.8rem
     margin: 0 0 3rem
-    background-color: #{dark blue}
+    background-color: #{dark main}
 
 footer
     margin-top: 3rem
     padding: 1.4rem 1.8rem
     font-size: 1.4rem
-    background-color: #{dark blue}
+    background-color: #{dark main}
     line-height: 1.5
 
 footer a
@@ -54,7 +54,7 @@ ul
     line-height: 1.3
 
 a
-    color:           #{light blue}
+    color:           #{light main}
     text-decoration: none
 
 a:hover
@@ -111,7 +111,7 @@ input:hover[type="submit"]
     background:  #{dark gray}
 
 .instance
-    color: #{light blue}
+    color: #{light main}
     font:  180% monospace
 
 .username