module Data.Text.ParagraphLayout.Internal.ParagraphLine (cutLines, mergeLines) where import Data.Int (Int32) import qualified Data.List.NonEmpty as NonEmpty import Data.Text.ParagraphLayout.Internal.Fragment import Data.Text.ParagraphLayout.Internal.LinePagination import Data.Text.ParagraphLayout.Internal.Plain.ParagraphLayout import Data.Text.ParagraphLayout.Internal.Rect -- | Represents one line of a `ParagraphLayout`. newtype ParagraphLine = ParagraphLine ParagraphLayout instance Line ParagraphLine where lineHeight (ParagraphLine pl) = height $ paragraphRect pl -- | Split the given `ParagraphLayout` into individual lines. cutLines :: ParagraphLayout -> [ParagraphLine] cutLines pl = map (\ y -> cutLine y pl) (lineOrigins pl) -- | Reduce the given `ParagraphLayout` to fragments with the given `y_origin`. -- -- This assumes that each line consists of fragments of equal height and that -- there is no space between lines. -- -- TODO: Use line numbers to support rich text. cutLine :: Int32 -> ParagraphLayout -> ParagraphLine cutLine y pl = ParagraphLine $ shiftFragments (-y) $ limitFragments y pl lineOrigins :: ParagraphLayout -> [Int32] lineOrigins pl = dedupe $ map (y_origin . fragmentRect) $ paragraphFragments pl -- | Remove duplicates from a sorted list. dedupe :: Eq a => [a] -> [a] dedupe xs = map NonEmpty.head $ NonEmpty.group xs -- | Combine the given `ParagraphLine`s into a `ParagraphLayout` by merging -- their fragments. mergeLines :: [ParagraphLine] -> ParagraphLayout mergeLines lls = foldl mergeLine emptyParagraphLayout lls mergeLine :: ParagraphLayout -> ParagraphLine -> ParagraphLayout mergeLine pl (ParagraphLine nextLine) = pl' where -- Quadratic time complexity. TODO: Consider optimising. pl' = appendFragments pl $ shiftFragments y nextLine y = y_terminus $ paragraphRect pl -- | Add @dy@ to each fragment's `y_origin`. shiftFragments :: Int32 -> ParagraphLayout -> ParagraphLayout shiftFragments dy = mapFragments (shiftFragment dy) shiftFragment :: Int32 -> Fragment -> Fragment shiftFragment dy f = f' where f' = f { fragmentRect = r' } r' = r { y_origin = y_origin r + dy } r = fragmentRect f -- | Keep only fragments with the given `y_origin` value. limitFragments :: Int32 -> ParagraphLayout -> ParagraphLayout limitFragments y = filterFragments ((== y) . y_origin . fragmentRect)