Function draw_shape_preview

fn draw_shape_preview(
    p: &Painter,
    kind: ShapeKind,
    from: Pos2,
    to: Pos2,
    palette: &Palette,
    stroke: Stroke,
)

Outline of the shape a drag is creating: from is where the press landed, to is the cursor. Bounded shapes fill the rectangle between them; a line or arrow runs from one to the other, so it must not be handed a normalised rect (its corners would point the wrong way down two of the four diagonals).