Function boolean_2d_fixed_grid 

pub fn boolean_2d_fixed_grid(
    subject: &[Ring2D],
    clip: &[Ring2D],
    op: BooleanOp2D,
    fill: ContourFillRule,
    grid_size: f64,
) -> Result<ContourSet, String>

Fixed-grid contour overlay using the same canonical engine and complete island/hole collector as boolean_2d. Coordinates are quantized; callers must include grid_size in their declared approximation and charge repeated operations against a shared budget. The per-call edge cap also bounds the uninterruptible overlay’s worst-case intersection expansion.