yi-0.3: Yi/Char.hs

--
-- Copyright (c) 2005 Tuomo Valkonen
--
--

--
-- | Same character classification and remapping routines.
--

module Yi.Char ( upcaseCtrl
	       , lowcaseCtrl
	       , upcaseLowcase
	       , ctrlLowcase
	       , lowcaseUpcase
	       , ctrlUpcase
	       , validChar
	       , remapChar
	       , remapBS
	       , isDel
	       , isEnter
	       , setMeta, clrMeta, isMeta, metaBit
	       ) where

import Yi.Event ( keyBackspace )
import Data.Char
import Data.Bits

validChar :: Char -> Bool
validChar '\n' = True
validChar '\r' = True
validChar c | isControl c = False
validChar _    = True

-- Remap a sequence of keys to another sequence.
remapChar :: Char -> Char -> Char -> Char -> Char -> Char
remapChar a1 b1 a2 _ c
    | a1 <= c && c <= b1 = chr $ ord c - ord a1 + ord a2
    | otherwise          = c

upcaseCtrl, lowcaseCtrl :: Char -> Char
upcaseLowcase, ctrlLowcase :: Char -> Char
lowcaseUpcase, ctrlUpcase :: Char -> Char
upcaseCtrl    = remapChar '\^A' '\^Z' 'A'   'Z'
lowcaseCtrl   = remapChar '\^A' '\^Z' 'a'   'z'
upcaseLowcase = remapChar 'a'   'z'   'A'   'Z'
ctrlLowcase   = remapChar 'a'   'z'   '\^A' '\^Z'
lowcaseUpcase = remapChar 'A'   'Z'   'a'   'z'
ctrlUpcase    = remapChar 'A'   'Z'   '\^A' '\^Z'

remapBS :: Char -> Char
remapBS k | isDel k = '\BS'
          | otherwise = k

isDel :: Char -> Bool
isDel '\BS'        = True
isDel '\127'       = True
isDel c | c == keyBackspace = True
isDel _            = False

isEnter :: Char -> Bool
isEnter '\n' = True
isEnter '\r' = True
isEnter _    = False

-- ---------------------------------------------------------------------
--
-- If Bit 7 is set in Char, then treat as a META key (ESC)
-- This is useful as it avoids the ncurses timeout issues associated
-- with the real ESC.

-- set the meta bit, as if Mod1/Alt had been pressed
setMeta :: Char -> Char
setMeta c = chr (setBit (ord c) metaBit)

-- remove the meta bit
clrMeta :: Char -> Char
clrMeta c = chr (clearBit (ord c) metaBit)

isMeta  :: Char -> Bool
isMeta  c = testBit (ord c) metaBit

metaBit :: Int
metaBit = 7