mirror of
https://github.com/jtdaugherty/brick.git
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136 lines
4.6 KiB
Haskell
136 lines
4.6 KiB
Haskell
{-# LANGUAGE TemplateHaskell #-}
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{-# LANGUAGE CPP #-}
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module Main where
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import Control.Monad (void)
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import Lens.Micro
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import Lens.Micro.TH
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import Lens.Micro.Mtl
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import qualified Graphics.Vty as V
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#if !(MIN_VERSION_base(4,11,0))
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import Data.Semigroup ((<>))
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#endif
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import qualified Brick.Main as M
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import qualified Brick.Types as T
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import Brick.Widgets.Core
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( (<+>)
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, vBox
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, hLimit
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, vLimit
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, str
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, visible
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, viewport
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, withDefAttr
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)
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import qualified Brick.Widgets.Center as C
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import qualified Brick.Widgets.Edit as E
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import qualified Brick.AttrMap as A
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import Brick.Util (on, fg)
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data Name = Edit
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| EditLines
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deriving (Ord, Show, Eq)
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data St =
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St { _edit :: E.Editor String Name
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}
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makeLenses ''St
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drawUI :: St -> [T.Widget Name]
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drawUI st = [ui]
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where
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e = renderWithLineNumbers (st^.edit)
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ui = C.center $ hLimit 50 $ vLimit 10 e
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-- | Given an editor, render the editor with line numbers to the left of
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-- the editor.
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--
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-- This essentially exploits knowledge of how the editor is implemented:
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-- we make a viewport containing line numbers that is just as high as
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-- the editor, then request that the line number associated with the
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-- editor's current line position be made visible, thus scrolling it
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-- into view. This is slightly brittle, however, because it relies on
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-- essentially keeping the line number viewport and the editor viewport
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-- in the same vertical scrolling state; with direct scrolling requests
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-- from EventM it is easily possible to put the two viewports into a
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-- state where they do not have the same vertical scrolling offset. That
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-- means that visibility requests made with 'visible' won't necessarily
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-- have the same effect in each viewport in that case. So this is
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-- only really usable in the case where you're sure that the editor's
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-- viewport and the line number viewports will not be managed by direct
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-- viewport operations in EventM. That's what I'd recommend anyway, but
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-- still, this is an important caveat.
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--
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-- There's another important caveat here: this particular implementation
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-- has @O(n)@ performance for editor height @n@ because we generate
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-- the entire list of line numbers on each rendering depending on the
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-- height of the editor. That means that for sufficiently large files,
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-- it will get more expensive to render the line numbers. There is a way
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-- around this problem, which is to take the approach that the @List@
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-- implementation takes: only render a region of visible line numbers
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-- around the currently-edited line that is just large enough to be
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-- guaranteed to fill the viewport, then translate that so that it
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-- appears at the right viewport offset, thus faking a viewport filled
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-- with line numbers when in fact we'd only ever render at most @2 * K +
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-- 1@ line numbers for a viewport height of @K@. That's more involved,
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-- so I didn't do it here, but that would be the way to go for a Real
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-- Application.
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renderWithLineNumbers :: E.Editor String Name -> T.Widget Name
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renderWithLineNumbers e =
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lineNumbersVp <+> editorVp
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where
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lineNumbersVp = hLimit (maxNumWidth + 1) $ viewport EditLines T.Vertical body
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editorVp = E.renderEditor (str . unlines) True e
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body = withDefAttr lineNumberAttr $ vBox numWidgets
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numWidgets = mkNumWidget <$> numbers
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mkNumWidget i = maybeVisible i $ str $ show i
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maybeVisible i
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| i == curLine + 1 =
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visible . withDefAttr currentLineNumberAttr
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| otherwise =
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id
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numbers = [1..h]
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contents = E.getEditContents e
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h = length contents
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curLine = fst $ E.getCursorPosition e
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maxNumWidth = length $ show h
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appEvent :: T.BrickEvent Name e -> T.EventM Name St ()
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appEvent (T.VtyEvent (V.EvKey V.KEsc [])) =
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M.halt
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appEvent ev = do
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zoom edit $ E.handleEditorEvent ev
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initialState :: St
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initialState =
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St (E.editor Edit Nothing "")
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lineNumberAttr :: A.AttrName
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lineNumberAttr = A.attrName "lineNumber"
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currentLineNumberAttr :: A.AttrName
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currentLineNumberAttr = lineNumberAttr <> A.attrName "current"
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theMap :: A.AttrMap
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theMap = A.attrMap V.defAttr
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[ (E.editAttr, V.white `on` V.blue)
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, (E.editFocusedAttr, V.black `on` V.yellow)
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, (lineNumberAttr, fg V.cyan)
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, (currentLineNumberAttr, V.defAttr `V.withStyle` V.bold)
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]
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theApp :: M.App St e Name
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theApp =
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M.App { M.appDraw = drawUI
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, M.appChooseCursor = const $ M.showCursorNamed Edit
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, M.appHandleEvent = appEvent
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, M.appStartEvent = return ()
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, M.appAttrMap = const theMap
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}
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main :: IO ()
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main = do
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void $ M.defaultMain theApp initialState
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