Cover.piece.line: def of gralha-coverage@0.1.0.1
Import: import gralha-coverage@0.1.0.1/cover.bend as Cover
Lines 716-727 of gralha-coverage@0.1.0.1/cover.bend: https://jend.leeeet.dev/read.txt?path=gralha-coverage@0.1.0.1/cover.bend&start_line=716&end_line=727

import Base
import gralha-text-scan@0.1.0.1/scan.bend as U

# A piece as a line shifted so the row starts at zero, for the sub-scanline
# scan of a row whose exact areas showed an overlap.
def piece.line(+p: Piece, +y: F32) -> CovLine:
  Piece{x0, y0, slope, top, bottom, dir} = p
  +xx0 = x0
  +yy0 = y0
  +s = slope
  +t = top
  +b = bottom
  +xt = (xx0 + (t - yy0) * s : F32)
  +xb = (xx0 + (b - yy0) * s : F32)
  U.choose(CovLine, F32.is_gt(dir, 0.0), CovLine{xt, (t - y : F32), xb, (b - y : F32)}, CovLine{xb, (b - y : F32), xt, (t - y : F32)})

Uses (8):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=F32
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=F32.add
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=F32.is_gt
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=F32.mul
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=F32.sub
  https://jend.leeeet.dev/definition.txt?path=gralha-coverage@0.1.0.1/cover.bend&name=CovLine
  https://jend.leeeet.dev/definition.txt?path=gralha-coverage@0.1.0.1/cover.bend&name=Piece
  https://jend.leeeet.dev/definition.txt?path=gralha-text-scan@0.1.0.1/scan.bend&name=choose