Whitespace

programs/LayerDemo.hs

@@ -46,8 +46,8 @@ drawUi st =
     [ C.centerLayer $
       B.border $ str "This layer is centered but other\nlayers are placed underneath it."
     , arrowLayer
-    , middleLayer st
-    , bottomLayer st
+    , middleLayer (st^.middleLayerLocation)
+    , bottomLayer (st^.bottomLayerLocation)
     ]
 
 arrowLayer :: Widget Name
@@ -59,15 +59,15 @@ arrowLayer =
        withDefAttr arrowAttr $
        str msg
 
-middleLayer :: St -> Widget Name
-middleLayer st =
-    translateBy (st^.middleLayerLocation) $
+middleLayer :: Location -> Widget Name
+middleLayer l =
+    translateBy l $
     reportExtent MiddleLayerElement $
     B.border $ str "Middle layer\n(Arrow keys move)"
 
-bottomLayer :: St -> Widget Name
-bottomLayer st =
-    translateBy (st^.bottomLayerLocation) $
+bottomLayer :: Location -> Widget Name
+bottomLayer l =
+    translateBy l $
     B.border $ str "Bottom layer\n(Ctrl-arrow keys move)"
 
 appEvent :: T.BrickEvent Name e -> T.EventM Name St ()

src/Brick/BorderMap.hs

@@ -17,7 +17,9 @@ module Brick.BorderMap
     ) where
 
 import Brick.Types.Common (Edges(..), Location(..), eTopL, eBottomL, eRightL, eLeftL, origin)
+#if !(MIN_VERSION_base(4,10,0))
 import Control.Applicative (liftA2)
+#endif
 import Data.IMap (IMap, Run(Run))
 import GHC.Generics
 import Control.DeepSeq

src/Brick/Widgets/Core.hs

@@ -1084,15 +1084,16 @@ translateBy off p =
 -- | Given a widget, translate it to position it relative to the
 -- upper-left coordinates of a reported extent with the specified
 -- positioning offset. If the specified name has no reported extent,
--- this just draws the specified widget with no special positioning.
+-- this draws nothing on the basis that it only makes sense to draw what
+-- was requested when the relative position can be known.
 --
 -- This is only useful for positioning something in a higher layer
 -- relative to a reported extent in a lower layer. Any other use is
--- likely to result in the specified widget being rendered as-is with
--- no translation. This is because this function relies on information
--- about lower layer renderings in order to work; using it with a
--- resource name that wasn't rendered in a lower layer will result in
--- this being equivalent to @id@.
+-- likely to result in the specified widget not being rendered. This
+-- is because this function relies on information about lower layer
+-- renderings in order to work; using it with a resource name that
+-- wasn't rendered in a lower layer will result in this being equivalent
+-- to @emptyWidget@.
 --
 -- For example, if you have two layers @topLayer@ and @bottomLayer@,
 -- then a widget drawn in @bottomLayer@ with @reportExtent Foo@ can be
@@ -1103,7 +1104,7 @@ relativeTo n off w =
     Widget (hSize w) (vSize w) $ do
         mExt <- lookupReportedExtent n
         case mExt of
-            Nothing -> render w
+            Nothing -> render emptyWidget
             Just ext -> render $ translateBy (extentUpperLeft ext <> off) w
 
 -- | Crop the specified widget on the left by the specified number of
@@ -1254,7 +1255,6 @@ cached n w =
             allClickables <- use clickableNamesL
             return [extentName e | e <- renderResult^.extentsL, extentName e `elem` allClickables]
 
-
 cacheLookup :: (Ord n) => n -> RenderM n (Maybe ([n], Result n))
 cacheLookup n = do
     cache <- lift $ gets (^.renderCacheL)

src/Brick/Widgets/Internal.hs

@@ -8,7 +8,7 @@ module Brick.Widgets.Internal
   )
 where
 
-import Lens.Micro ((^.), (&), (%~))
+import Lens.Micro ((^.), (&), (%~), (.~))
 import Lens.Micro.Mtl ((%=))
 import Control.Monad
 import Control.Monad.State.Strict
@@ -35,7 +35,14 @@ renderFinal :: (Ord n)
 renderFinal aMap layerRenders (w, h) chooseCursor rs =
     (newRS, picWithBg, theCursor, concat layerExtents)
     where
-        (layerResults, !newRS) = flip runState rs $ sequence $
+        -- Reset various fields from the last rendering state so they
+        -- don't accumulate or affect this rendering.
+        resetRs = rs & reportedExtentsL .~ mempty
+                     & observedNamesL .~ mempty
+                     & clickableNamesL .~ mempty
+                     & requestedVisibleNames_L .~ mempty
+
+        (layerResults, !newRS) = flip runState resetRs $ sequence $
             (\p -> runReaderT p ctx) <$>
             (\layerWidget -> do
                 result <- render $ cropToContext layerWidget