Module Hugin_gg

These are the values every other Hugin library speaks in: points P2, boxes Box2, affine maps Affine, paths Path and the pen that strokes them Stroke, and colours Color. The library depends on nothing.

Conventions

• The plane. The x axis points right and the y axis points down, as on a page or a screen. Units are the caller's; Hugin uses points, 1/72 inch. Angles are in radians, and a positive angle turns from the positive x axis towards the positive y axis, clockwise on screen.
• Argument order. Functions that build or transform a value take it last, so they chain with |>: Path.empty |> Path.move_to p |> Path.line_to q. Path.append follows the rule, which makes it the opposite of List.append.
• Equality. equal functions compare structure, with floats compared by Float.equal, so nan equals nan and 0. equals -0.. One shape can have several structures: a rectangle from Path.rect and the same rectangle drawn from another corner are not equal. compare functions are total orders compatible with equal.
• Printing. pp functions format values for debugging and tests. Their output may change between releases unless the function says otherwise.
• Non-finite numbers. Points and affine maps hold any floats, and functions on them follow float arithmetic: a non-finite coordinate or coefficient makes the points it reaches non-finite. In a path such points are gaps (Gaps). Boxes, stroke styles and colours never hold a non-finite number: their constructors raise Invalid_argument, as each states.