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module Data.Text.ParagraphLayout.Internal.Plain.Paragraph
( Paragraph (..)
, paragraphSpanBounds
, paragraphSpanTexts
, paragraphText
)
where
import Data.List.NonEmpty (NonEmpty)
import qualified Data.List.NonEmpty as NonEmpty
import Data.Text.Array (Array)
import Data.Text.Internal (Text (Text))
import Data.Text.ParagraphLayout.Internal.ParagraphOptions
import Data.Text.ParagraphLayout.Internal.Span
-- | Text to be laid out as a single paragraph.
--
-- May be divided into any number of neighbouring spans, each of which will
-- be represented as a separate `SpanLayout` in the resulting layout.
--
-- The input text must be encoded as UTF-8 in a contiguous byte array.
--
-- You may need to use "Data.Text.Internal" in order to determine the byte
-- array and the necessary offsets to construct the paragraph without copying
-- data.
--
-- For simple use cases, it may be sufficient to construct paragraphs using
-- [ParagraphConstruction]("Data.Text.ParagraphLayout.ParagraphConstruction").
data Paragraph d = Paragraph
Array
-- ^ A byte array containing the whole text to be laid out, in UTF-8.
--
-- This array will be passed to "Data.Text.Glyphize", which passes it to
-- [@hb_buffer_add_utf8()@]
-- (https://harfbuzz.github.io/harfbuzz-hb-buffer.html#hb-buffer-add-utf8).
--
-- In the output, `Data.Text.Glyphize.cluster` will be a byte offset of
-- the corresponding input character from this array.
Int
-- ^ Byte offset of the first span from the start of the byte array.
-- Any characters preceding this offset will not be shaped, but may still
-- be used to influence the shape of neighbouring characters.
[Span d]
-- ^ Parts of the text to be laid out, in logical order.
-- The initial offset plus total length of all spans must not exceed
-- the bounds of the byte array.
-- Any characters following the last span will not be shaped, but may still
-- be used to influence the shape of neighbouring characters.
ParagraphOptions
-- ^ Options applying to the paragraph as a whole.
-- | Calculate the offsets into the `Paragraph`'s underlying `Data.Text.Array`
-- where each span starts and ends, in ascending order. The resulting list
-- will be one larger than the list of input spans.
--
-- You can use this function to verify that Balkón will slice the input text
-- correctly.
paragraphSpanBounds :: Paragraph d -> NonEmpty Int
paragraphSpanBounds (Paragraph _ initialOffset spans _) =
-- TODO: Consider adding checks for array bounds.
NonEmpty.scanl (+) initialOffset (map spanLength spans)
-- | Turn each span of the input `Paragraph` into a `Text`.
--
-- You can use this function to verify that Balkón will slice the input text
-- correctly.
paragraphSpanTexts :: Paragraph d -> [Text]
paragraphSpanTexts p@(Paragraph arr _ _ _) = zipWith toText sStarts sEnds
where
toText start end = Text arr start (end - start)
sStarts = NonEmpty.init sBounds
sEnds = NonEmpty.tail sBounds
sBounds = paragraphSpanBounds p
-- | Turn all spans of the input `Paragraph` into one combined `Text`.
--
-- You can use this function to verify that Balkón will slice the input text
-- correctly.
paragraphText :: Paragraph d -> Text
paragraphText p@(Paragraph arr _ _ _) = Text arr start (end - start)
where
start = NonEmpty.head sBounds
end = NonEmpty.last sBounds
sBounds = paragraphSpanBounds p