Wumpus.Basic.Kernel.Objects.Anchors

Anchor points on shapes, bounding boxes, etc.

Anchors are addressable positions, an examplary use is taking anchors on node shapes to get the start and end points for connectors in a network (graph) diagram.

** WARNING ** - The API here needs some thought as to a good balance of the type classes - in a nutshell "are corners better than cardinals". Originally I tried to follow how I understand the TikZ anchors to work, but this is perhaps not ideal for dividing into type-classes.

Anchors

type Anchor u = Point2 u

Note an Anchor is just a Point2.

Anchor classes

class CenterAnchor a where

Center of an object.

Methods

center :: u ~ DUnit a => a -> Anchor u

Instances

Fractional u => CenterAnchor (BoundingBox u)

class ApexAnchor a where

Apex of an object.

Methods

apex :: u ~ DUnit a => a -> Anchor u

class CardinalAnchor a where

Cardinal (compass) positions on an object.

Cardinal anchors should be at their equivalent radial position. However, some shapes may not be able to easily define radial positions or may be able to provide more efficient definitions for the cardinal anchors. Hence the redundancy seems justified.

Methods

north :: u ~ DUnit a => a -> Anchor u

south :: u ~ DUnit a => a -> Anchor u

east :: u ~ DUnit a => a -> Anchor u

west :: u ~ DUnit a => a -> Anchor u

Instances

Fractional u => CardinalAnchor (BoundingBox u)

class CardinalAnchor2 a where

Secondary group of cardinal (compass) positions on an object for the diagonal positions.

It seems possible that for some objects defining the primary compass points (north, south,...) will be straight-forward whereas defining the secondary compass points may be problematic, hence the compass points are split into two classes.

Methods

northeast :: u ~ DUnit a => a -> Anchor u

southeast :: u ~ DUnit a => a -> Anchor u

southwest :: u ~ DUnit a => a -> Anchor u

northwest :: u ~ DUnit a => a -> Anchor u

Instances

Fractional u => CardinalAnchor2 (BoundingBox u)

class RadialAnchor a where

Anchor on a border that can be addressed by an angle.

The angle is counter-clockwise from the right-horizontal, i.e. 0 is east.

Methods

radialAnchor :: Radian -> u ~ DUnit a => a -> Anchor u

class TopCornerAnchor a where

Anchors at the top left and right corners of a shape.

For some shapes (Rectangle) the TikZ convention appears to be have cardinals as the corner anchors, but this doesn't seem to be uniform. Wumpus will need to reconsider anchors at some point...

Methods

topLeftCorner :: u ~ DUnit a => a -> Anchor u

topRightCorner :: u ~ DUnit a => a -> Anchor u

class BottomCornerAnchor a where

Anchors at the bottom left and right corners of a shape.

Methods

bottomLeftCorner :: u ~ DUnit a => a -> Anchor u

bottomRightCorner :: u ~ DUnit a => a -> Anchor u

class SideMidpointAnchor a where

Anchors in the center of a side.

Sides are addressable by index. Following TikZ, side 1 is expected to be the top of the shape. If the shape has an apex instead of a side then side 1 is expected to be the first side left of the apex.

Implementations are also expected to modulo the side number, rather than throw an out-of-bounds error.

Methods

sideMidpoint :: Int -> u ~ DUnit a => a -> Anchor u

Extended anchor points

projectAnchor :: (Real u, Floating u, CenterAnchor a, u ~ DUnit a) => (a -> Anchor u) -> u -> a -> Anchor u

projectAnchor : extract_func * dist * object -> Point

Derive a anchor by projecting a line from the center of an object through the intermediate anchor (produced by the extraction function). The final answer point is located along the projected line at the supplied distance dist.

E.g. take the north of a rectangle and project it 10 units further on:

 projectAnchor north 10 my_rect

If the distance is zero the answer with be whatever point the the extraction function produces.

If the distance is negative the answer will be along the projection line, between the center and the intermediate anchor.

If the distance is positive the anchor will be extend outwards from the intermediate anchor.

radialConnectorPoints :: (Real u, Floating u, CenterAnchor a, RadialAnchor a, CenterAnchor b, RadialAnchor b, u ~ DUnit a, u ~ DUnit b) => a -> b -> (Point2 u, Point2 u)

radialConnectorPoints : object_a * object_b -> (Point_a, Point_b)

Find the radial connectors points for objects a and b along the line joining their centers.