Implement tree rendering

package.yaml

@@ -19,6 +19,7 @@ dependencies:
 - brick
 - containers
 - text
+- transformers
 - vty
 - websockets
 

src/Forest/Client/WidgetTree.hs

@@ -0,0 +1,95 @@
+{-# LANGUAGE OverloadedStrings #-}
+
+module Forest.Client.WidgetTree
+  ( WidgetTree(..)
+  , renderWidgetTree
+  , IndentOptions(..)
+  , boxDrawingBranching
+  , boxDrawingLine
+  , asciiBranching
+  , asciiLine
+  ) where
+
+import           Brick
+import           Control.Monad.Trans.Reader
+import qualified Data.Text                  as T
+import qualified Graphics.Vty               as Vty
+
+data WidgetTree n = WidgetTree (Widget n) [WidgetTree n]
+
+-- This attempts to properly indent multi-line widgets, though it's kinda hacky.
+-- It seems to work though, so I'm not going to complain (until the first bugs
+-- appear, that is).
+--
+-- The text strings passed MUST NOT be multiline strings, or this entire
+-- function will break.
+indentWith :: T.Text -> T.Text -> Widget n -> Widget n
+indentWith firstLine otherLines wrapped = Widget
+  { hSize = hSize wrapped
+  , vSize = vSize wrapped
+  , render = renderWidget
+  }
+  where
+    maxWidth = max (T.length firstLine) (T.length otherLines)
+    renderWidget = do
+      context <- ask
+      result <- render $ hLimit (availWidth context - maxWidth) wrapped
+      let resultHeight = Vty.imageHeight $ image result
+          leftText = vBox $ txt firstLine : replicate (resultHeight - 1) (txt otherLines)
+      render $ leftText <+> wrapped
+
+indent :: IndentOptions -> [Widget n] -> Widget n
+indent opts widgets = vBox $ reverse $ case reverse widgets of
+  [] -> []
+  (w:ws) ->
+    indentWith (lastBranch opts) (afterLastBranch opts) w :
+    map (indentWith (inlineBranch opts) (noBranch opts)) ws
+
+renderWidgetTree :: IndentOptions -> WidgetTree n -> Widget n
+renderWidgetTree opts (WidgetTree node children) =
+  node <=> indent opts (map (renderWidgetTree opts) children)
+
+-- | These options control how a tree is rendered. For more information on how
+-- the various options are used, try rendering a tree with 'boxDrawingBranhing'
+-- and inspect the results.
+--
+-- Warning: The options *must* be single line strings and *must not* contain
+-- newlines of any sort.
+data IndentOptions = IndentOptions
+  { noBranch        :: T.Text
+  , inlineBranch    :: T.Text
+  , lastBranch      :: T.Text
+  , afterLastBranch :: T.Text
+  } deriving (Show, Eq)
+
+boxDrawingBranching :: IndentOptions
+boxDrawingBranching = IndentOptions
+  { noBranch        = "│ "
+  , inlineBranch    = "├╴"
+  , lastBranch      = "└╴"
+  , afterLastBranch = "  "
+  }
+
+boxDrawingLine :: IndentOptions
+boxDrawingLine = IndentOptions
+  { noBranch        = "│ "
+  , inlineBranch    = "│ "
+  , lastBranch      = "│ "
+  , afterLastBranch = "│ "
+  }
+
+asciiBranching :: IndentOptions
+asciiBranching = IndentOptions
+  { noBranch        = "| "
+  , inlineBranch    = "+-"
+  , lastBranch      = "+-"
+  , afterLastBranch = "  "
+  }
+
+asciiLine :: IndentOptions
+asciiLine = IndentOptions
+  { noBranch        = "| "
+  , inlineBranch    = "| "
+  , lastBranch      = "| "
+  , afterLastBranch = "| "
+  }