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{-
Copyright (C) 2007 John MacFarlane <jgm@berkeley.edu>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
-}
{- |
Module : Text.Pandoc.Blocks
Copyright : Copyright (C) 2007 John MacFarlane
License : GNU GPL, version 2 or above
Maintainer : John MacFarlane <jgm@berkeley.edu>
Stability : alpha
Portability : portable
Functions for the manipulation of fixed-width blocks of text.
These are used in the construction of plain-text tables.
-}
module Text.Pandoc.Blocks
(
TextBlock (..),
docToBlock,
blockToDoc,
widthOfBlock,
heightOfBlock,
hcatBlocks,
hsepBlocks,
centerAlignBlock,
leftAlignBlock,
rightAlignBlock
)
where
import Text.PrettyPrint
import Data.List ( intersperse )
-- | A fixed-width block of text. Parameters are width of block,
-- height of block, and list of lines.
data TextBlock = TextBlock Int Int [String]
instance Show TextBlock where
show x = show $ blockToDoc x
-- | Break lines in a list of lines so that none are greater than
-- a given width.
breakLines :: Int -- ^ Maximum length of lines.
-> [String] -- ^ List of lines.
-> [String]
breakLines _ [] = []
breakLines width (l:ls) =
if length l > width
then (take width l):(breakLines width ((drop width l):ls))
else l:(breakLines width ls)
-- | Convert a @Doc@ element into a @TextBlock@ with a specified width.
docToBlock :: Int -- ^ Width of text block.
-> Doc -- ^ @Doc@ to convert.
-> TextBlock
docToBlock width doc =
let rendered = renderStyle (style {lineLength = width,
ribbonsPerLine = 1}) doc
lns = breakLines width $ lines rendered
in TextBlock width (length lns) lns
-- | Convert a @TextBlock@ to a @Doc@ element.
blockToDoc :: TextBlock -> Doc
blockToDoc (TextBlock _ _ lns) =
if null lns
then empty
else vcat $ map text lns
-- | Returns width of a @TextBlock@ (number of columns).
widthOfBlock :: TextBlock -> Int
widthOfBlock (TextBlock width _ _) = width
-- | Returns height of a @TextBlock@ (number of rows).
heightOfBlock :: TextBlock -> Int
heightOfBlock (TextBlock _ height _) = height
-- | Pads a string out to a given width using spaces.
hPad :: Int -- ^ Desired width.
-> String -- ^ String to pad.
-> String
hPad width line =
let linelen = length line
in if linelen <= width
then line ++ replicate (width - linelen) ' '
else take width line
-- | Concatenates a list of @TextBlock@s into a new @TextBlock@ in
-- which they appear side by side.
hcatBlocks :: [TextBlock] -> TextBlock
hcatBlocks [] = TextBlock 0 0 []
hcatBlocks [x] = x -- This is not redundant! We don't want last item hPad'd.
hcatBlocks ((TextBlock width1 height1 lns1):xs) =
let (TextBlock width2 height2 lns2) = hcatBlocks xs
height = max height1 height2
width = width1 + width2
lns1' = map (hPad width1) $ lns1 ++ replicate (height - height1) ""
lns2' = lns2 ++ replicate (height - height2) ""
lns = zipWith (++) lns1' lns2'
in TextBlock width height lns
-- | Like @hcatBlocks@, but inserts space between the @TextBlock@s.
hsepBlocks :: [TextBlock] -> TextBlock
hsepBlocks = hcatBlocks . (intersperse (TextBlock 1 1 [" "]))
isWhitespace :: Char -> Bool
isWhitespace x = x `elem` " \t"
-- | Left-aligns the contents of a @TextBlock@ within the block.
leftAlignBlock :: TextBlock -> TextBlock
leftAlignBlock (TextBlock width height lns) =
TextBlock width height $ map (dropWhile isWhitespace) lns
-- | Right-aligns the contents of a @TextBlock@ within the block.
rightAlignBlock :: TextBlock -> TextBlock
rightAlignBlock (TextBlock width height lns) =
let rightAlignLine ln =
let (spaces, rest) = span isWhitespace $ reverse $ hPad width ln
in reverse (rest ++ spaces)
in TextBlock width height $ map rightAlignLine lns
-- | Centers the contents of a @TextBlock@ within the block.
centerAlignBlock :: TextBlock -> TextBlock
centerAlignBlock (TextBlock width height lns) =
let centerAlignLine ln =
let ln' = hPad width ln
(startSpaces, rest) = span isWhitespace ln'
endSpaces = takeWhile isWhitespace (reverse ln')
numSpaces = length (startSpaces ++ endSpaces)
startSpaces' = replicate (quot numSpaces 2) ' '
in startSpaces' ++ rest
in TextBlock width height $ map centerAlignLine lns
|
