Scroll using SDL's viewport

Horizontal needs testing.

1 files changed, 20 insertions, 1 deletions

diff --git a/src/Game/Entities.hs b/src/Game/Entities.hs
index 7e0e0cf..4e5a686 100644
--- a/src/Game/Entities.hs
+++ b/src/Game/Entities.hs
@@ -1,4 +1,4 @@
-module Game.Entities (Entities, Entity, mkEntities, updateAll, render) where
+module Game.Entities (Entities, Entity, mkEntities, updateAll, render, renderVisible, playerPosition) where
 
 import Control.Monad
 import Data.Bits (Bits (..))
@@ -35,6 +35,13 @@ mkEntities sprites m controls stateRef = do
     toEntity playerRef (M.BatteryEntity x y) = mkBattery sprites x y (collision playerRef 16) (collectedBattery stateRef)
     toEntity _ (M.PlayerEntity _ _) = error "Player already processed"
 
+-- | Return the player's entity position (x, y).
+playerPosition :: Entities -> (Int, Int)
+playerPosition (Entities _ _ _ entities) =
+  (player.x, player.y)
+  where
+    player = head entities
+
 processSpawn :: S.SpriteSheet -> Spawn -> IO Entity
 processSpawn sprites (DustEffectSpawn x y) = mkEffect sprites x y "dust"
 
@@ -73,6 +80,18 @@ updateAll es = do
       TypeEnemy -> False
       _ -> True
 
+-- | Render only visible entities according to the provided viewport.
+renderVisible :: SDL.Renderer -> Entities -> M.Viewport -> IO ()
+renderVisible renderer (Entities sprites player state entities) v =
+  render renderer (Entities sprites player state visible)
+  where
+    -- FIXME: entities should have size so we can be exact here and
+    -- avoid the hardcoded size
+    visible = filter (\e -> isVisible v e.x e.y 16 16) entities
+    isVisible :: M.Viewport -> Int -> Int -> Int -> Int -> Bool
+    isVisible (M.Viewport vx vy vw vh) x y w h =
+      x < vx + vw && vx < x + w && y < vy + vh && vy < y + h
+
 render :: SDL.Renderer -> Entities -> IO ()
 render renderer es = do
   state <- readIORef es.state