introducing particles

first little drafts

affection.cabal

@@ -34,6 +34,7 @@ flag examples
 library
   exposed-modules:     Affection
                      , Affection.Draw
+                     , Affection.Particle
                      , Affection.Types
   default-extensions:  OverloadedStrings
 

src/Affection.hs

@@ -30,6 +30,7 @@ import Foreign.Storable (peek)
 
 import Affection.Types as A
 import Affection.Draw as A
+import Afection.Particle as A
 
 import qualified BABL as B
 

src/Affection/Particle.hs

@@ -0,0 +1,32 @@
+-- | This module introduces a simple particle system to Affection
+module Affection.Particle
+  ( updateParticles
+  , drawParticles
+  ) where
+
+import Affection.Types
+
+-- This function updates particles through a specified function. Particle ageing
+-- and death is being handled by 'updateParticles' itself and does not need to
+-- bother you.
+updateParticles
+  :: Double                           -- ^ Elapsed time in seconds
+  -> (Double -> Particle -> Particle) -- ^ Update function for a single 'Particle'
+                                      -- This Function should take the elapsed time
+                                      -- in seconds and the initial particle as arguments.
+  -> [Particle]                       -- ^ List of 'Particle's to be processed
+  -> [Particle]                       -- ^ resulting list of particles
+updateParticles _    _     []     = []
+updateParticles time funct (p:ps) =
+  if particleLife p - time < 0
+  then
+    updateParticles time funct ps
+  else
+    (funct time $ p { particleLife = particleLife p - time }) :
+    updateparticles time funct ps
+
+drawParticles
+  :: (Particle -> Affection us ())
+  -> [Particle]
+  -> Affection us ()
+drawParticles = mapM_

src/Affection/Types.hs

@@ -13,10 +13,12 @@ module Affection.Types
   , RGBA(..)
   , DrawType(..)
   , DrawRequest(..)
-  , SDL.WindowConfig(..)
+    -- | Particle system
-  , SDL.defaultWindow
+  , Particle(..)
     -- | Convenience exports
   , liftIO
+  , SDL.WindowConfig(..)
+  , SDL.defaultWindow
     -- | GEGL reexports
   , G.GeglRectangle(..)
   , G.GeglBuffer(..)
@@ -122,3 +124,11 @@ data DrawType
   | Line     -- ^ only draw the outline of the area
     { lineWidth :: Int -- ^ Width of line in pixels
     }
+
+-- | A single particle
+data Particle = Particle
+  { particleLife     :: Double     -- ^ Time to live in seconds
+  , particlePosition :: (Int, Int) -- ^ Position of particle on canvas
+  , particleRotation :: Double     -- ^ Particle rotation
+  , particleVelocity :: (Int, Int) -- ^ particle velocity as vector of pixels per second
+  } deriving (Show, Eq)