~alcinnz/CatTrap

ref: 15ad59dbc0899181a3066ba2a4d8104a7b055861 CatTrap/Graphics/Layout/Inline/CSS.hs -rw-r--r-- 2.2 KiB
15ad59db — Adrian Cochrane Draft utility to aid resolving conflicting dataflow. 1 year, 6 months ago 
                                                                                
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{-# LANGUAGE OverloadedStrings #-}
module Graphics.Layout.Inline.CSS(CSSInline(..), ParagraphBuilder(..),
    buildParagraph, concatParagraph, finalizeParagraph) where

import Data.CSS.Syntax.Tokens (Token(..))
import Stylist (PropertyParser(..))
import qualified Data.Text.Lazy as Lz
import qualified Data.Text as Txt
import Data.Text.Internal (Text(..))
import Data.Text.ParagraphLayout (Span(..), SpanOptions(..), LineHeight(..),
                                Paragraph(..), ParagraphOptions(..))

import Graphics.Layout.CSS.Font (Font'(..), hbScale)
import Data.Char (isSpace)

data CSSInline = CSSInline Lz.Text SpanOptions

instance PropertyParser CSSInline where
    temp = CSSInline "" SpanOptions {
        spanLanguage = "Zxx"
    }
    inherit (CSSInline _ opts) = CSSInline "" opts

    longhand _ (CSSInline _ opts) "content" toks
        | all isString toks =
            Just $ CSSInline (Lz.concat [Lz.fromStrict x | String x <- toks]) opts
      where
        isString (String _) = True
        isString _ = False
    longhand _ (CSSInline txt opts) "-argo-lang" [String x] =
        Just $ CSSInline txt opts { spanLanguage = Txt.unpack x }
    longhand _ _ _ _ = Nothing

data ParagraphBuilder = ParagraphBuilder Lz.Text [Span]

buildParagraph :: CSSInline -> ParagraphBuilder
buildParagraph (CSSInline txt opts) =
    ParagraphBuilder txt [flip Span opts $ fromEnum $ Lz.length txt]
concatParagraph :: ParagraphBuilder -> ParagraphBuilder -> ParagraphBuilder
concatParagraph (ParagraphBuilder aTxt aOpts) (ParagraphBuilder bTxt bOps) =
    ParagraphBuilder (aTxt `Lz.append` bTxt)
                    (aOpts ++ [Span (toEnum (fromEnum $ Lz.length aTxt) + off) opts
                                | Span off opts <- bOps])
finalizeParagraph :: ParagraphBuilder -> Font' -> Maybe Paragraph
finalizeParagraph (ParagraphBuilder txt _) _ | Lz.all isSpace txt || Lz.null txt = Nothing
finalizeParagraph (ParagraphBuilder txt ops) font' = Just $ Paragraph txt' 0 ops pOps
    where
        Text txt' _ _ = Lz.toStrict txt
        pOps = ParagraphOptions {
            paragraphFont = hbFont font',
            paragraphLineHeight = Absolute $ round (lineheight font' * hbScale font'),
            paragraphMaxWidth = 0 -- This is what we're computing!
        }