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module Data.Text.ParagraphLayout.Internal.Fragment
(Fragment(..)
,ShapedRun
,shapedRun)
where
import Data.Int (Int32)
import Data.Text.Glyphize (GlyphInfo, GlyphPos)
import Data.Text.ParagraphLayout.Internal.Rect
-- | A unit of text laid out in a rectangular area.
--
-- Equivalent to the CSS3 terms /box fragment/ or /fragment/, except that
-- continuous text even within one line can be split into multiple fragments,
-- either because it comes from multiple input spans, or because it contains
-- glyphs from multiple scripts.
data Fragment = Fragment
{ fragmentRect :: Rect Int32
-- ^ Physical position of the fragment within the paragraph, calculated
-- using all glyph advances in this fragment and the calculated line height.
--
-- This is the space that the glyphs "take up" and is probably what you
-- want to use for detecting position-based events such as mouse clicks.
--
-- Beware that actual glyphs will not be drawn exactly to the borders of
-- this rectangle -- they may be offset inwards and they can also extend
-- outwards!
--
-- These are not the typographic bounding boxes that you use for determining
-- the area to draw on -- you need FreeType or a similar library for that.
--
-- The origin coordinates are relative to the paragraph.
, fragmentPen :: (Int32, Int32)
-- ^ Coordinates of the initial pen position, from which the first glyph
-- should be drawn, relative to the origin of the `fragmentRect`.
-- Each glyph's `x_advance` or `y_advance` are then used to move the pen
-- position for the next glyph.
, fragmentGlyphs :: [(GlyphInfo, GlyphPos)]
-- ^ Glyphs contained in the fragment, as returned from HarfBuzz.
}
deriving (Eq, Read, Show)
-- | A simplified representation of a box fragment, suitable for passing to a
-- text drawing library but lacking detailed size information.
type ShapedRun = (Int32, Int32, [(GlyphInfo, GlyphPos)])
-- | Convert a `Fragment` to a `ShapedRun`.
shapedRun :: Fragment -> ShapedRun
shapedRun f = (x, y, g)
where
x = x_origin r + px
y = y_origin r + py
g = fragmentGlyphs f
(px, py) = fragmentPen f
r = fragmentRect f