{-# LANGUAGE FlexibleContexts , FlexibleInstances , DeriveDataTypeable , GeneralizedNewtypeDeriving , TypeFamilies , ViewPatterns #-} {-# OPTIONS_GHC -fno-warn-orphans #-} ----------------------------------------------------------------------------- -- | -- Module : Diagrams.TwoD.Path -- Copyright : (c) 2011 diagrams-lib team (see LICENSE) -- License : BSD-style (see LICENSE) -- Maintainer : diagrams-discuss@googlegroups.com -- -- Paths in two dimensions are special since we may stroke them to -- create a 2D diagram, and (eventually) perform operations such as -- intersection and union. They also have a trace, whereas paths in -- higher dimensions do not. -- ----------------------------------------------------------------------------- module Diagrams.TwoD.Path ( -- * Constructing path-based diagrams stroke, stroke', strokeT, strokeT' -- ** Stroke options , FillRule(..) , FillRuleA(..), getFillRule, fillRule , StrokeOpts(..) -- ** Inside/outside testing , isInsideWinding, isInsideEvenOdd -- * Clipping , Clip(..), clipBy ) where import Control.Applicative (liftA2) import qualified Data.Foldable as F import Data.Semigroup import Data.Typeable import Data.AffineSpace import Data.Default import Data.VectorSpace import Diagrams.Core import Diagrams.Coordinates import Diagrams.Path import Diagrams.Segment import Diagrams.Solve import Diagrams.TwoD.Segment import Diagrams.TwoD.Types import Diagrams.Util (tau) ------------------------------------------------------------ -- Trail and path traces --------------------------------- ------------------------------------------------------------ -- Only 2D trails and paths have a trace. -- XXX can the efficiency of this be improved? See the comment in -- Diagrams.Path on the Enveloped instance for Trail. instance Traced (Trail R2) where getTrace t = case addClosingSegment t of (Trail segs _) -> foldr (\seg bds -> moveOriginBy (negateV . segOffset $ seg) bds <> getTrace seg) mempty segs instance Traced (Path R2) where getTrace = F.foldMap trailTrace . pathTrails where trailTrace (p, t) = moveOriginTo ((-1) *. p) (getTrace t) ------------------------------------------------------------ -- Constructing path-based diagrams ---------------------- ------------------------------------------------------------ -- | Convert a path into a diagram. The resulting diagram has the -- names 0, 1, ... assigned to each of the path's vertices. -- -- See also 'stroke'', which takes an extra options record allowing -- its behavior to be customized. -- -- Note that a bug in GHC 7.0.1 causes a context stack overflow when -- inferring the type of @stroke@. The solution is to give a type -- signature to expressions involving @stroke@, or (recommended) -- upgrade GHC (the bug is fixed in 7.0.2 onwards). stroke :: Renderable (Path R2) b => Path R2 -> Diagram b R2 stroke = stroke' (def :: StrokeOpts ()) instance Renderable (Path R2) b => PathLike (QDiagram b R2 Any) where pathLike st cl segs = stroke $ pathLike st cl segs -- | A variant of 'stroke' that takes an extra record of options to -- customize its behavior. In particular: -- -- * Names can be assigned to the path's vertices -- -- 'StrokeOpts' is an instance of 'Default', so @stroke' 'with' { -- ... }@ syntax may be used. stroke' :: (Renderable (Path R2) b, IsName a) => StrokeOpts a -> Path R2 -> Diagram b R2 stroke' opts p = mkQD (Prim p) (getEnvelope p) (getTrace p) (fromNames . concat $ zipWith zip (vertexNames opts) ((map . map) subPoint (pathVertices p)) ) (Query $ Any . flip (runFillRule (queryFillRule opts)) p) -- | A record of options that control how a path is stroked. -- @StrokeOpts@ is an instance of 'Default', so a @StrokeOpts@ -- records can be created using @'with' { ... }@ notation. data StrokeOpts a = StrokeOpts { vertexNames :: [[a]] -- ^ Atomic names that should be assigned -- to the vertices of the path so that -- they can be referenced later. If -- there are not enough names, the extra -- vertices are not assigned names; if -- there are too many, the extra names -- are ignored. Note that this is a -- /list of lists/ of names, since paths -- can consist of multiple trails. The -- first list of names are assigned to -- the vertices of the first trail, the -- second list to the second trail, and -- so on. -- -- The default value is the empty list. , queryFillRule :: FillRule -- ^ The fill rule used for determining -- which points are inside the path. -- The default is 'Winding'. NOTE: for -- now, this only affects the resulting -- diagram's 'Query', /not/ how it will -- be drawn! To set the fill rule -- determining how it is to be drawn, -- use the 'fillRule' function. } instance Default (StrokeOpts a) where def = StrokeOpts { vertexNames = [] , queryFillRule = Winding } -- | A composition of 'stroke' and 'pathFromTrail' for conveniently -- converting a trail directly into a diagram. -- -- Note that a bug in GHC 7.0.1 causes a context stack overflow when -- inferring the type of 'stroke' and hence of @strokeT@ as well. -- The solution is to give a type signature to expressions involving -- @strokeT@, or (recommended) upgrade GHC (the bug is fixed in 7.0.2 -- onwards). strokeT :: (Renderable (Path R2) b) => Trail R2 -> Diagram b R2 strokeT = stroke . pathFromTrail -- | A composition of 'stroke'' and 'pathFromTrail' for conveniently -- converting a trail directly into a diagram. strokeT' :: (Renderable (Path R2) b, IsName a) => StrokeOpts a -> Trail R2 -> Diagram b R2 strokeT' opts = stroke' opts . pathFromTrail ------------------------------------------------------------ -- Inside/outside testing ------------------------------------------------------------ -- | Enumeration of algorithms or \"rules\" for determining which -- points lie in the interior of a (possibly self-intersecting) -- closed path. data FillRule = Winding -- ^ Interior points are those with a nonzero -- /winding/ /number/. See -- <http://en.wikipedia.org/wiki/Nonzero-rule>. | EvenOdd -- ^ Interior points are those where a ray -- extended infinitely in a particular -- direction crosses the path an odd number -- of times. See -- <http://en.wikipedia.org/wiki/Even-odd_rule>. deriving (Eq) runFillRule :: FillRule -> P2 -> Path R2 -> Bool runFillRule Winding = isInsideWinding runFillRule EvenOdd = isInsideEvenOdd newtype FillRuleA = FillRuleA (Last FillRule) deriving (Typeable, Semigroup) instance AttributeClass FillRuleA -- | Extract the fill rule from a 'FillRuleA' attribute. getFillRule :: FillRuleA -> FillRule getFillRule (FillRuleA (Last r)) = r -- | Specify the fill rule that should be used for determining which -- points are inside a path. fillRule :: HasStyle a => FillRule -> a -> a fillRule = applyAttr . FillRuleA . Last cross :: R2 -> R2 -> Double cross (coords -> x :& y) (coords -> x' :& y') = x * y' - y * x' -- XXX link to more info on this -- | Test whether the given point is inside the given (closed) path, -- by testing whether the point's /winding number/ is nonzero. Note -- that @False@ is /always/ returned for /open/ paths, regardless of -- the winding number. isInsideWinding :: P2 -> Path R2 -> Bool isInsideWinding p = (/= 0) . crossings p -- | Test whether the given point is inside the given (closed) path, -- by testing whether a ray extending from the point in the positive -- x direction crosses the path an even (outside) or odd (inside) -- number of times. Note that @False@ is /always/ returned for -- /open/ paths, regardless of the number of crossings. isInsideEvenOdd :: P2 -> Path R2 -> Bool isInsideEvenOdd p = odd . crossings p -- | Compute the sum of /signed/ crossings of a path as we travel in the -- positive x direction from a given point. crossings :: P2 -> Path R2 -> Int crossings p = F.sum . map (trailCrossings p) . pathTrails -- | Compute the sum of signed crossings of a trail starting from the -- given point in the positive x direction. trailCrossings :: P2 -> (P2, Trail R2) -> Int -- open trails have no inside or outside, so don't contribute crossings trailCrossings _ (_, t) | not (isClosed t) = 0 trailCrossings p@(unp2 -> (x,y)) (start, tr) = sum . map test $ fixTrail start tr where test (FLinear a@(unp2 -> (_,ay)) b@(unp2 -> (_,by))) | ay <= y && by > y && isLeft a b > 0 = 1 | by <= y && ay > y && isLeft a b < 0 = -1 | otherwise = 0 test c@(FCubic (unp2 -> x1@(_,x1y)) (unp2 -> c1@(_,c1y)) (unp2 -> c2@(_,c2y)) (unp2 -> x2@(_,x2y)) ) = sum . map testT $ ts where ts = filter (liftA2 (&&) (>=0) (<=1)) $ cubForm (- x1y + 3*c1y - 3*c2y + x2y) ( 3*x1y - 6*c1y + 3*c2y) (-3*x1y + 3*c1y) (x1y - y) testT t = let (unp2 -> (px,_)) = c `fAtParam` t in if px > x then signFromDerivAt t else 0 signFromDerivAt t = let (dx,dy) = (3*t*t) *^ ((-1)*^x1 ^+^ 3*^c1 ^-^ 3*^c2 ^+^ x2) ^+^ (2*t) *^ (3*^x1 ^-^ 6*^c1 ^+^ 3*^c2) ^+^ ((-3)*^x1 ^+^ 3*^c1) ang = atan2 dy dx in case () of _ | 0 < ang && ang < tau/2 && t < 1 -> 1 | -tau/2 < ang && ang < 0 && t > 0 -> -1 | otherwise -> 0 isLeft a b = cross (b .-. a) (p .-. a) ------------------------------------------------------------ -- Clipping ---------------------------------------------- ------------------------------------------------------------ -- | @Clip@ tracks the accumulated clipping paths applied to a -- diagram. Note that the semigroup structure on @Clip@ is list -- concatenation, so applying multiple clipping paths is sensible. -- The clipping region is the intersection of all the applied -- clipping paths. newtype Clip = Clip { getClip :: [Path R2] } deriving (Typeable, Semigroup) instance AttributeClass Clip type instance V Clip = R2 instance Transformable Clip where transform t (Clip ps) = Clip (transform t ps) -- | Clip a diagram by the given path: -- -- * Only the parts of the diagram which lie in the interior of the -- path will be drawn. -- -- * The envelope of the diagram is unaffected. clipBy :: (HasStyle a, V a ~ R2) => Path R2 -> a -> a clipBy = applyTAttr . Clip . (:[]) -- XXX Should include a 'clipTo' function which clips a diagram AND -- restricts its envelope. It will have to take a *pointwise minimum* -- of the diagram's current envelope and the path's envelope. Not -- sure of the best way to do this at the moment.