Allow resizing of panels

This allows the use of +/- to change the panel sizes, like
in PuDB.

MANUAL.rst

@@ -82,6 +82,14 @@ additional keybindings.
 currently running. For example, it can display the current bindings, loaded
 modules, and the current program trace.
 
+----------
+Navigation
+----------
+
+At any point in time, you can revert back to the Source Viewer panel with the
+``<Esc>`` key, and you can always quit by hitting ``<Esc>`` in the Source Viewer
+panel.
+
 -----------
 Keybindings
 -----------
@@ -100,6 +108,7 @@ Source Viewer
 - ``Down``, ``j``: Move the cursor down. (``j`` and ``k`` from Vim keybinds).
 - ``PgUp``: Move the source viewer one page up.
 - ``PgDown``: Move the source viewer one page down.
+- ``+``, ``-``: Increase/decrease the Info panel size.
 - ``b``: Toggle breakpoint at current line. Not every line in a source file can
   have a breakpoint placed on it.
 - ``s``: Advance execution by one step. Same as the ``:step`` in GHCi.
@@ -108,9 +117,9 @@ Source Viewer
 - ``t``: Advance execution until next breakpoint under tracing. Same as
   ``:trace`` in GHCi.
 
-****************
-Live Interpreter
-****************
+***********************
+Live Interpreter (REPL)
+***********************
 
 - ``Ctrl+x``: Toggle between the Source Viewer and the Live Interpreter
   panels.
@@ -119,4 +128,7 @@ Live Interpreter
 - ``Down``: Scroll forward in time through the REPL command history.
 - ``PgUp``: Scroll the Live Interpreter window one page up.
 - ``PgDown``: Scroll the Live Interpreter window one page down.
+- ``Ctrl+n``: Toggle scrolling mode.
+- ``+``, ``-`` while in scrolling mode: Increase/decrease the live
+  panel size.
 - ``<Enter>``: Enter a command to the REPL.

app/AppState.hs

@@ -4,6 +4,11 @@ module AppState
     ( ActiveWindow (..)
     , AppConfig (..)
     , AppState (..)
+    , WidgetSizes
+    , changeInfoWidgetSize
+    , changeReplWidgetSize
+    , getInfoWidth
+    , getReplHeight
     , appInterpState
     , getSourceContents
     , getSourceLineCount
@@ -33,15 +38,29 @@ import AppTopLevel (AppName (..))
 import Ghcid.Daemon (toggleBreakpointLine)
 import qualified Ghcid.Daemon as Daemon
 import qualified Loc
+import qualified Util
 
 data ActiveWindow = ActiveCodeViewport | ActiveLiveInterpreter | ActiveInfoWindow
     deriving (Show, Eq, Ord)
 
-{- | Size information of the current GHCiTUI main boxes.
-type WindowSizes = [(ActiveWindow, (Maybe Int, Maybe Int))]
--}
+data MaxState = NoMaxState | Maximised | Minimised
 
--- | Application state wrapper
+-- | Size information of the current GHCiTUI main boxes.
+data WidgetSizes = WidgetSizes
+    { _wsInfoWidth :: !Int
+    , _wsInfoMaxState :: !MaxState
+    , _wsReplHeight :: !Int
+    , _wsReplMaxState :: !MaxState
+    }
+
+{- | Application state wrapper.
+
+Contains information about the UI and configuration. It also holds a
+handle to the actual interpreter under the hood, but on the high level
+it should not hold anything internal to GHCi or GHCiD.
+
+Prefer to create this with 'makeInitialState'.
+-}
 data AppState n = AppState
     { interpState :: Daemon.InterpState ()
     -- ^ The interpreter handle.
@@ -61,6 +80,9 @@ data AppState n = AppState
     -- ^ Currently selected line number. Resets back to 1.
     , sourceMap :: Map.Map FilePath T.Text
     -- ^ Mapping between source filepaths and their contents.
+    , _currentWidgetSizes :: WidgetSizes
+    -- ^ Current window/box/panel sizes (since it can change). Do not edit
+    -- directly.
     , displayDebugConsoleLogs :: !Bool
     -- ^ Whether to display debug Console logs.
     , debugConsoleLogs :: [Text]
@@ -95,6 +117,15 @@ appInterpState = Lens.lens _appInterpState (\x ais -> x{_appInterpState = ais})
 liveEditor' :: Lens.Lens' (AppState n) (BE.Editor T.Text n)
 liveEditor' = appInterpState . AIS.liveEditor
 
+currentWidgetSizes :: Lens.Lens' (AppState n) WidgetSizes
+currentWidgetSizes = Lens.lens _currentWidgetSizes (\x cws -> x{_currentWidgetSizes = cws})
+
+wsInfoWidth :: Lens.Lens' WidgetSizes Int
+wsInfoWidth = Lens.lens _wsInfoWidth (\x ipw -> x{_wsInfoWidth = ipw})
+
+wsReplHeight :: Lens.Lens' WidgetSizes Int
+wsReplHeight = Lens.lens _wsReplHeight (\x rh -> x{_wsReplHeight = rh})
+
 -- | Write a debug log entry.
 writeDebugLog :: T.Text -> AppState n -> AppState n
 writeDebugLog lg s = s{debugConsoleLogs = lg : debugConsoleLogs s}
@@ -155,6 +186,30 @@ getSourceContents s = s.selectedFile >>= (s.sourceMap Map.!?)
 getSourceLineCount :: AppState n -> Maybe Int
 getSourceLineCount s = length . T.lines <$> getSourceContents s
 
+changeInfoWidgetSize :: Int -> AppState n -> AppState n
+changeInfoWidgetSize amnt s =
+    Lens.set
+        (currentWidgetSizes . wsInfoWidth)
+        -- Do not let the min go too low (<=2), because this causes a memory leak in Brick?
+        (Util.clamp (10, 120) (getInfoWidth s + amnt))
+        s
+
+changeReplWidgetSize :: Int -> AppState n -> AppState n
+changeReplWidgetSize amnt s =
+    Lens.set
+        (currentWidgetSizes . wsReplHeight)
+        -- Do not let the min go too low, because the box disappears then.
+        (Util.clamp (1, 80) (getReplHeight s + amnt))
+        s
+
+-- | Return the info box's desired width in character columns.
+getInfoWidth :: AppState n -> Int
+getInfoWidth = _wsInfoWidth . _currentWidgetSizes
+
+-- | Return the REPL (interactive interpreter)'s box in lines.
+getReplHeight :: AppState n -> Int
+getReplHeight = _wsReplHeight . _currentWidgetSizes
+
 -- | Initialise the state from the config.
 makeInitialState
     :: AppConfig
@@ -199,5 +254,12 @@ makeInitialState appConfig target cwd = do
             , selectedFile
             , selectedLine = 1
             , sourceMap = mempty
+            , _currentWidgetSizes =
+                WidgetSizes
+                    { _wsInfoWidth = 30
+                    , _wsInfoMaxState = NoMaxState
+                    , _wsReplHeight = 11 -- 10 plus 1 for the entry line.
+                    , _wsReplMaxState = NoMaxState
+                    }
             , splashContents
             }

app/BrickUI.hs

@@ -28,6 +28,7 @@ import AppState
     , liveEditor'
     , makeInitialState
     )
+import qualified AppState
 import AppTopLevel (AppName (..))
 import qualified Events
 import qualified Ghcid.Daemon as Daemon
@@ -58,6 +59,7 @@ appDraw s =
                 else "Interpreter (Scrolling)"
             )
 
+    -- For seeing the source code.
     viewportBox :: B.Widget AppName
     viewportBox =
         B.borderWithLabel sourceLabel
@@ -72,16 +74,16 @@ appDraw s =
                 Just h -> B.padBottom B.Max (w <=> B.hBorder <=> B.txt h)
                 _ -> w
 
+    -- For the REPL.
     interpreterBox :: B.Widget AppName
     interpreterBox =
         B.borderWithLabel interpreterLabel
-            . B.vLimit (displayLimit + 1) -- Plus one for the current line.
+            . B.vLimit (AppState.getReplHeight s)
             . B.withVScrollBars B.OnRight
             . B.viewport LiveInterpreterViewport B.Vertical
             $ previousOutput <=> lockToBottomOnViewLock promptLine
       where
         enableCursor = True
-        displayLimit = 10
         previousOutput =
             if null s.interpLogs
                 then B.emptyWidget
@@ -119,7 +121,7 @@ appDraw s =
 infoBox :: AppS -> B.Widget AppName
 infoBox appState =
     B.borderWithLabel (B.txt "Info")
-        . B.hLimit 30
+        . B.hLimit (AppState.getInfoWidth appState)
         . B.padRight B.Max
         . B.padBottom B.Max
         $ bindingBox

app/Events.hs

@@ -38,10 +38,10 @@ handleEvent ev = do
 
 -- | Handle events when the interpreter (live GHCi) is selected.
 handleInterpreterEvent :: B.BrickEvent AppName e -> B.EventM AppName (AppState AppName) ()
-handleInterpreterEvent ev =
+handleInterpreterEvent ev = do
+    appState <- B.get
     case ev of
         B.VtyEvent (V.EvKey V.KEnter []) -> do
-            appState <- B.get
             let cmd = T.strip (T.unlines (editorContents appState))
 
             -- Actually run the command.
@@ -70,7 +70,6 @@ handleInterpreterEvent ev =
             B.invalidateCache
         B.VtyEvent (V.EvKey (V.KChar '\t') []) -> do
             -- Tab completion?
-            appState <- B.get
             let cmd = T.strip (T.unlines (editorContents appState))
             (newAppState1, _output) <-
                 runDaemon2
@@ -94,7 +93,6 @@ handleInterpreterEvent ev =
                             <> (showT . AIS.historyPos . getAis $ s)
                         )
                         s
-            appState <- B.get
             let appState' =
                     wDebug
                         . replaceCommandBufferWithHist -- Display the history.
@@ -103,7 +101,6 @@ handleInterpreterEvent ev =
                         $ appState
             B.put appState'
         B.VtyEvent (V.EvKey V.KDown _) -> do
-            appState <- B.get
             let wDebug s =
                     writeDebugLog
                         ( "Handled Down; historyPos is "
@@ -120,10 +117,22 @@ handleInterpreterEvent ev =
             B.vScrollPage (B.viewportScroll LiveInterpreterViewport) B.Down
         B.VtyEvent (V.EvKey V.KPageUp _) -> do
             B.vScrollPage (B.viewportScroll LiveInterpreterViewport) B.Up
-            appState <- B.get
             B.put (Lens.set (appInterpState . AIS.viewLock) False appState)
+        B.VtyEvent (V.EvKey (V.KChar 'n') [V.MCtrl]) -> do
+            -- Invert the viewLock.
+            B.put (Lens.over (appInterpState . AIS.viewLock) not appState)
+
+        -- While scrolling (viewLock disabled), allow resizing the live interpreter history.
+        B.VtyEvent (V.EvKey (V.KChar '+') [])
+            | not (appState ^. appInterpState . AIS.viewLock) -> do
+                B.put (AppState.changeReplWidgetSize 1 appState)
+        B.VtyEvent (V.EvKey (V.KChar '-') [])
+            | not (appState ^. appInterpState . AIS.viewLock) -> do
+                B.put (AppState.changeReplWidgetSize (-1) appState)
+
+        -- Actually handle keystrokes.
         ev' -> do
-            appState <- B.get
+            -- When typing, bring us back down to the terminal.
             B.put (Lens.set (appInterpState . AIS.viewLock) True appState)
             -- Actually handle text input commands.
             B.zoom liveEditor' $ BE.handleEditorEvent ev'
@@ -192,6 +201,13 @@ handleViewportEvent (B.VtyEvent (V.EvKey key ms))
         moveSelectedLineBy 1
     | key `elem` [V.KUp, V.KChar 'k'] = do
         moveSelectedLineBy (-1)
+    -- '+' and '-' move the middle border.
+    | key == V.KChar '+' && null ms = do
+        appState <- B.get
+        B.put (AppState.changeInfoWidgetSize 1 appState)
+    | key == V.KChar '-' && null ms = do
+        appState <- B.get
+        B.put (AppState.changeInfoWidgetSize (-1) appState)
     | key == V.KPageDown = do
         appState <- B.get
         mViewport <- B.lookupViewport CodeViewport