Add regression tests for #178 pollEvent space use

Author: chrisdone

bench/Space.hs

@@ -0,0 +1,40 @@
+{-# LANGUAGE OverloadedStrings #-}
+
+-- | Test that space usage is low and avoid GCs where possible.
+
+module Main where
+
+import SDL
+import Weigh
+
+-- | Main entry point.
+main :: IO ()
+main =
+  mainWith
+    (do setColumns [Case, Allocated, GCs]
+        sequence_
+          [ validateAction
+            ("pollEvent " ++ show i)
+            pollEventTest
+            i
+            (\weight ->
+               if weightGCs weight > 0
+                 then Just "Non-zero number of garbage collections!"
+                 else if weightAllocatedBytes weight > 2000
+                        then Just
+                               "Allocated >2KB! Allocations should be constant."
+                        else Nothing)
+          | i <- [1, 10, 100, 1000, 10000]
+          ])
+
+-- | Test that merely polling does not allocate or engage the GC.
+-- <https://github.com/haskell-game/sdl2/issues/178>
+pollEventTest :: Int -> IO ()
+pollEventTest iters = do
+  initializeAll
+  let go :: Int -> IO ()
+      go 0 = pure ()
+      go i = do
+        _ <- pollEvent
+        go (i - 1)
+  go iters

sdl2.cabal

@@ -140,6 +140,18 @@ library
   if os(windows)
     cpp-options: -D_SDL_main_h -DSDL_main_h_
 
+test-suite sdl-space
+  type:                exitcode-stdio-1.0
+  main-is:             Space.hs
+  hs-source-dirs:      bench
+  build-depends:       base
+                     , weigh
+                     , linear
+                     , sdl2
+                     , deepseq
+  ghc-options:         -Wall -rtsopts -O2
+  default-language:    Haskell2010
+
 executable lazyfoo-lesson-01
   if flag(examples)
     build-depends: base, sdl2