Fix widget tree

This fix took way too long. Something like this shouldn't be that difficult, but
it apparently is. :/

src/Forest/Client/WidgetTree.hs

@@ -11,18 +11,34 @@ module Forest.Client.WidgetTree
   ) where
 
 import           Brick
+import           Brick.BorderMap
 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.
+addLoc :: Location -> Location -> Location
+addLoc l1 l2 =
+  let (x1, y1) = loc l1
+      (x2, y2) = loc l2
+  in  Location (x1 + x2, y1 + y2)
+
+offsetResult :: Location -> Result n -> Result n
+offsetResult offset result = result
+  { cursors = map offsetCursor $ cursors result
+  , visibilityRequests = map offsetVr $ visibilityRequests result
+  , extents = map offsetExtent $ extents result
+  , borders = translate offset $ borders result
+  }
+  where
+    offsetCursor c = c{cursorLocation = addLoc offset $ cursorLocation c}
+    offsetVr vr = vr{vrPosition = addLoc offset $ vrPosition vr}
+    offsetExtent e = e
+      { extentUpperLeft = addLoc offset $ extentUpperLeft e
+      , extentOffset    = addLoc offset $ extentOffset e
+      }
+
 indentWith :: T.Text -> T.Text -> Widget n -> Widget n
 indentWith firstLine otherLines wrapped = Widget
   { hSize = hSize wrapped
@@ -35,8 +51,11 @@ indentWith firstLine otherLines wrapped = Widget
       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
+          textLines = firstLine : replicate (resultHeight - 1) otherLines
+          leftImage = Vty.vertCat $ map (Vty.text' Vty.defAttr) textLines
+          newImage = leftImage Vty.<|> image result
+          newResult = offsetResult (Location (maxWidth, 0)) $ result{image=newImage}
+      pure newResult
 
 indent :: IndentOptions -> [Widget n] -> Widget n
 indent opts widgets = vBox $ reverse $ case reverse widgets of