Add withContent alias and use it in Box examples (#139)

Author: arthurxavierx

docs/Examples2/Box.example.purs

@@ -2,7 +2,7 @@ module Lumi.Components2.Examples.Box where
 
 import Prelude
 import Color.Scheme.MaterialDesign (blue, green, red)
-import Lumi.Components (lumiElement)
+import Lumi.Components (lumiElement, ($$$))
 import Lumi.Components.Example (example)
 import Lumi.Components.Spacing (Space(..), vspace)
 import Lumi.Components.Text (h2_, p_)
@@ -40,22 +40,22 @@ docs =
           , vspace S24
           , h2_ "Defaults"
           , example $ lumiElement box
-              $ _ { content = exampleContent }
+              $$$ exampleContent
           , h2_ "Row"
           , example $ lumiElement box
               $ _row
-              $ _ { content = exampleContent }
+              $$$ exampleContent
           , h2_ "Align/justify"
           , example $ lumiElement box
               $ _row
               $ _alignSelf Stretch -- only necessary because `example` isn't a Box
               $ _justify End
-              $ _ { content = exampleContent }
+              $$$ exampleContent
           , h2_ "Space evenly"
           , example $ lumiElement box
               $ _row
               $ _alignSelf Stretch -- only necessary because `example` isn't a Box
               $ _justify SpaceEvenly
-              $ _ { content = exampleContent }
+              $$$ exampleContent
           ]
         }

src/Lumi/Components.purs

@@ -6,6 +6,7 @@ module Lumi.Components
   , lumiComponent
   , lumiComponentFromHook
   , lumiElement
+  , withContent, ($$$)
   ) where
 
 import Prelude
@@ -76,6 +77,19 @@ lumiComponentFromHook name defaults propsToHook = do
         , className: lumiComponentClassName name
         }
 
+-- | A convenient alias for setting the `content` property of a Lumi component
+-- | if it exists.
+infixr 0 withContent as $$$
+
+withContent ::
+  forall props content r.
+  ((LumiProps (content :: content | props) -> LumiProps (content :: content | props)) -> r) ->
+  content ->
+  r
+withContent m content = m _{ content = content }
+
+-- # Internal
+
 lumiComponentClassName :: String -> String
 lumiComponentClassName name = "lumi-component lumi-" <> toLower name