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https://github.com/jtdaugherty/brick.git
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84 lines
2.5 KiB
Haskell
84 lines
2.5 KiB
Haskell
{-# LANGUAGE CPP #-}
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{-# LANGUAGE OverloadedStrings #-}
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module Main where
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#if !MIN_VERSION_base(4,8,0)
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import Control.Applicative
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#endif
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import Control.Monad (void)
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#if !(MIN_VERSION_base(4,11,0))
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import Data.Monoid ((<>))
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#endif
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import qualified Graphics.Vty as V
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import qualified Brick.Types as T
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import qualified Brick.Main as M
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import qualified Brick.Widgets.Center as C
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import Brick.Types
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( Widget
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, BrickEvent(..)
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)
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import Brick.Widgets.Core
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( vBox
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, padTopBottom
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, withDefAttr
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, cached
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, padBottom
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, str
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)
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import Brick (on)
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import Brick.Widgets.Center
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( hCenter
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)
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import Brick.AttrMap
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( AttrName
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, attrMap
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)
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data Name = ExpensiveWidget
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deriving (Ord, Show, Eq)
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drawUi :: Int -> [Widget Name]
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drawUi i = [ui]
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where
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ui = C.vCenter $
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vBox $ hCenter <$>
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[ str "This demo shows how cached widgets behave. The top widget below"
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, str "is cacheable, so once it's rendered, brick re-uses the rendering"
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, str "each time it is drawn. The bottom widget is not cacheable so it is"
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, str "drawn on every request. Brick supports cache invalidation to force"
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, str "a redraw of cached widgets; we can trigger that here with 'i'. Notice"
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, str "how state changes with '+' aren't reflected in the cached widget"
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, str "until the cache is invalidated with 'i'."
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, padTopBottom 1 $
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cached ExpensiveWidget $
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withDefAttr emphAttr $ str $ "This widget is cached (state = " <> show i <> ")"
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, padBottom (T.Pad 1) $
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withDefAttr emphAttr $ str $ "This widget is not cached (state = " <> show i <> ")"
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, hCenter $ str "Press 'i' to invalidate the cache,"
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, str "'+' to change the state value, and"
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, str "'Esc' to quit."
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]
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appEvent :: Int -> BrickEvent Name e -> T.EventM Name (T.Next Int)
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appEvent i (VtyEvent (V.EvKey (V.KChar '+') [])) = M.continue $ i + 1
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appEvent i (VtyEvent (V.EvKey (V.KChar 'i') [])) = M.invalidateCacheEntry ExpensiveWidget >> M.continue i
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appEvent i (VtyEvent (V.EvKey V.KEsc [])) = M.halt i
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appEvent i _ = M.continue i
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emphAttr :: AttrName
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emphAttr = "emphasis"
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app :: M.App Int e Name
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app =
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M.App { M.appDraw = drawUi
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, M.appStartEvent = return
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, M.appHandleEvent = appEvent
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, M.appAttrMap = const $ attrMap V.defAttr [(emphAttr, V.white `on` V.blue)]
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, M.appChooseCursor = M.neverShowCursor
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}
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main :: IO ()
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main = void $ M.defaultMain app 0
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